Antibiotics

15 pages, 1309 KB

Open AccessArticle

Emergence of Polymyxin Resistance Driven by a PhoQ Mutation in KPC-2-Producing Klebsiella pneumoniae

by Huijuan Song, Cui Jian, Lu Gong, Ziyong Sun, Zhongju Chen and Yue Wang

Antibiotics 2026, 15(2), 183; https://doi.org/10.3390/antibiotics15020183 (registering DOI) - 7 Feb 2026

Background: The emergence of polymyxin-resistant, carbapenem-resistant Klebsiella pneumoniae (CRKP) presents a critical challenge to clinical management. This study aimed to delineate the molecular mechanisms driving the acquisition of polymyxin resistance in CRKP. Methods: We analyzed polymyxin-susceptible and polymyxin-resistant CRKP isolates obtained [...] Read more.

Background: The emergence of polymyxin-resistant, carbapenem-resistant Klebsiella pneumoniae (CRKP) presents a critical challenge to clinical management. This study aimed to delineate the molecular mechanisms driving the acquisition of polymyxin resistance in CRKP. Methods: We analyzed polymyxin-susceptible and polymyxin-resistant CRKP isolates obtained from a single patient. Antimicrobial susceptibility testing was performed to determine the minimum inhibitory concentrations. Whole genome sequencing was employed to identify variations in two-component systems and to screen for mcr genes, which were involved in polymyxin resistance. Differential gene expression was assessed using RNA sequencing and validated by quantitative real-time PCR. Furthermore, site-directed mutagenesis was utilized to confirm the causal role of specific mutations in conferring the resistant phenotype. Results: An L96P mutation in the PhoQ protein was found in the polymyxin-resistant CRKP isolate. Compared with the PhoQ wild-type, this mutation significantly upregulated expression of phoP/Q, pmrD, and arnBCADTEF operon-related genes. A corresponding L96P mutant was subsequently constructed in the polymyxin-susceptible ATCC 13883 strain via site-directed mutagenesis. Antimicrobial susceptibility testing confirmed that the PhoQ L96P mutation elevates the minimal inhibitory concentrations of colistin and polymyxin B to 64 mg/L and >32 mg/L, respectively, from a baseline of 0.5 mg/L. Conclusions: The PhoQ L96P mutation is a pivotal driver of polymyxin resistance in CRKP, primarily mediated through the upregulation of the arnBCADTEF operon. Full article

(This article belongs to the Section Mechanism and Evolution of Antibiotic Resistance)

17 pages, 584 KB

Open AccessArticle

Integrating Syndromic Molecular Assays into Routine Diagnostic Microbiology: Benefits and Challenges

by Sara Comini, Anna Maria Priori, Francesco Coppari, Matteo Sabbatini, Concetta Bruno, Matteo Boattini, Gabriele Bianco and Francesca Brecciaroli

Antibiotics 2026, 15(2), 182; https://doi.org/10.3390/antibiotics15020182 (registering DOI) - 7 Feb 2026

Abstract

Background/Objectives: Rapid pathogen identification is essential to optimize antimicrobial therapy and improve patient outcomes, particularly in severe infections. Syndromic molecular diagnostics have been introduced to overcome the limitations of conventional culture-based methods. This study evaluated the diagnostic performance and real-life implementation of [...] Read more.

Background/Objectives: Rapid pathogen identification is essential to optimize antimicrobial therapy and improve patient outcomes, particularly in severe infections. Syndromic molecular diagnostics have been introduced to overcome the limitations of conventional culture-based methods. This study evaluated the diagnostic performance and real-life implementation of BioFire^® FilmArray^® syndromic panels compared with routine microbiological diagnostics. Methods: A total of 955 clinical specimens collected between 2022 and June 2025 were retrospectively analyzed, including positive blood cultures (n = 400), lower respiratory tract samples (n = 309), cerebrospinal fluid (n = 158) and stool specimens (n = 88). FilmArray^® BCID2, Pneumonia Plus, Meningitis/Encephalitis and Gastrointestinal panels were performed on the Biofire Fimarray^® instrument according to clinical indication and compared with conventional culture-based identification and phenotypic antimicrobial susceptibility testing. Results: Overall diagnostic concordance between BioFire^® FilmArray^® syndromic panels and conventional methods was high across all specimen types, with the highest positive percent agreement (PPA) observed for bloodstream infections (97.7%) and gastrointestinal pathogens (100%). In respiratory samples, the Pneumonia Plus panel detected a considerable number of microorganisms that could not be identified by culture, including viral pathogens and fastidious bacteria. Molecular detection of antimicrobial resistance markers showed excellent concordance with phenotypic profiles, with 100% agreement for CTX-M, carbapenemases (KPC, NDM, OXA-48-like, IMP), and vanA/B, while lower concordance was observed for mecA/C in staphylococci. In parallel, semi-quantitative bacterial loads provided by the Pneumonia Plus panel showed a strong essential agreement with culture-based quantification (97.4%, ±1 log₁₀). Across all panels, syndromic testing significantly reduced diagnostic turnaround time. Conclusions: Syndromic molecular panels provide rapid and reliable simultaneous detection of pathogens, as well as early resistance marker detection, thereby supporting timely antimicrobial optimization and stewardship when integrated with conventional microbiological diagnostics. Full article

(This article belongs to the Special Issue Bacterial Detection, Identification, and Antimicrobial Susceptibility Testing)

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13 pages, 1142 KB

Open AccessArticle

Unbound and Periprostatic Adipose Tissue Cefazolin Pharmacokinetics in Robotic-Assisted Radical Prostatectomy

by Toshiaki Komatsu, Yuki Takahashi, Yoko Takayama, Yuto Akamada, Masaomi Ikeda, Hideyasu Tsumura, Daisuke Ishii, Kazumasa Matsumoto, Masatsugu Iwamura, Hirotsugu Okamoto, Hideaki Hanaki and Katsuya Otori

Antibiotics 2026, 15(2), 181; https://doi.org/10.3390/antibiotics15020181 - 6 Feb 2026

Abstract

Background/Objectives: This study aimed to describe the population pharmacokinetics of cefazolin (CFZ) using unbound serum and periprostatic adipose tissue concentrations and to optimize dosing regimens for patients undergoing robotic-assisted radical prostatectomy (RARP). Methods: We investigated the population pharmacokinetics of CFZ using 295 unbound [...] Read more.

Background/Objectives: This study aimed to describe the population pharmacokinetics of cefazolin (CFZ) using unbound serum and periprostatic adipose tissue concentrations and to optimize dosing regimens for patients undergoing robotic-assisted radical prostatectomy (RARP). Methods: We investigated the population pharmacokinetics of CFZ using 295 unbound serum and 67 periprostatic adipose tissue samples from 67 individuals. CFZ concentrations were determined in all samples. A nonlinear mixed-effects model was developed. The pharmacodynamic target was defined as maintaining unbound trough and periprostatic adipose tissue concentrations exceeding the minimum inhibitory concentration (MIC) against methicillin-susceptible Staphylococcus aureus (MSSA) for over 90% of the dosing interval (MIC₉₀; 0.5 mg/L). Results: Systemic clearance of unbound CFZ was significantly associated with creatinine clearance (CLcr). In patients with normal renal function, simulations showed that a 1 g CFZ infusion over 15 min maintained unbound concentrations exceeding the MSSA MIC₉₀ for >90% of the 3 h interval after the initial dose. Notably, in patients with mild renal impairment (CLcr ≤ 80 mL/min), a 5 h dosing interval also achieved a >90% probability of maintaining the target CFZ concentration. Conclusions: The simulations demonstrated that the probability of target attainment of >90% was maintained for up to 5 h in patients with mild renal impairment (CLcr ≤ 80 mL/min). These findings provide a pharmacokinetic rationale suggesting that the standard additional dose may not be necessary for this subgroup; however, future clinical studies are needed to validate safety and efficacy. Full article

(This article belongs to the Special Issue Clinical Pharmacokinetics, Pharmacodynamics, and/or TDM of Antimicrobial Agents)

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31 pages, 1441 KB

Open AccessReview

A Century-Old Solution for 21st Century Challenges: Current Applications with a Focus on Biocontrol, Environmental Impacts, and Regulatory Perspectives

by Anaelle Baud, Inès Rougis and Franck Bertolla

Antibiotics 2026, 15(2), 180; https://doi.org/10.3390/antibiotics15020180 - 6 Feb 2026

Abstract

In the face of rising antimicrobial resistance, food insecurity, and climate change, bacteriophages are gaining renewed attention as promising biological alternatives to antibiotics across human, animal, and plant health sectors. Their high specificity, self-replicating capacity, and biodegradability make them valuable tools for combating [...] Read more.

In the face of rising antimicrobial resistance, food insecurity, and climate change, bacteriophages are gaining renewed attention as promising biological alternatives to antibiotics across human, animal, and plant health sectors. Their high specificity, self-replicating capacity, and biodegradability make them valuable tools for combating antimicrobial or pesticide resistance and promoting sustainable biocontrol. This review discusses commonly accepted selection criteria for therapeutic phages, such as avoiding temperate types and screening for undesirable genes, while acknowledging ongoing debates and exceptions in specific clinical or ecological contexts. An overview of phage-based applications within a One Health framework is provided, spanning human medicine, veterinary practice, aquaculture, food safety and crop protection. Particular attention is given to agricultural biocontrol, where several successful plant protection strategies are highlighted, illustrating the feasibility and diversity of phage-based approaches. Despite their potential, key challenges remain regarding phage stability, formulation, and persistence under environmental conditions. Emerging innovations such as encapsulation, carrier bacteria, and protective formulations aim to enhance field performance. Furthermore, this review emphasizes the need to assess the environmental safety of phage applications, particularly their impacts on natural ecosystems, microbial communities, and ecological functions. Finally, the regulatory and policy challenges that currently limit the large-scale deployment of phages, particularly in the European Union, where they remain evaluated under conventional chemical pesticide frameworks are discussed. The development of dedicated regulatory pathways, better adapted to the specificities of phages, is argued to be essential for supporting their integration into agroecological transition strategies and next-generation antimicrobial policies. Full article

(This article belongs to the Special Issue Phage Applications from Diagnostics to Treatment of Bacterial Infections in a One Health World)

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13 pages, 567 KB

Open AccessArticle

Clinical Outcomes and Healthcare Resource Utilization of Ceftolozane/Tazobactam in Vulnerable Patient Populations

by Emre Yücel, Alex Soriano, Florian Thalhammer, Stefan Kluge, Mike Allen, Jessica Levy, Huina Yang and Sunny Kaul

Antibiotics 2026, 15(2), 179; https://doi.org/10.3390/antibiotics15020179 - 6 Feb 2026

Abstract

Background: AMR is a public health concern which leads to high global morbidity and mortality. Immunocompromised patients, who are more susceptible to contracting potentially life-threatening infections, are faced with reduced treatment options due to emerging AMR. Ceftolozane/tazobactam is a novel β-lactam/β-lactamase inhibitor which [...] Read more.

Background: AMR is a public health concern which leads to high global morbidity and mortality. Immunocompromised patients, who are more susceptible to contracting potentially life-threatening infections, are faced with reduced treatment options due to emerging AMR. Ceftolozane/tazobactam is a novel β-lactam/β-lactamase inhibitor which displays effectiveness against resistant Gram-negative infections. Methods: SPECTRA was a multinational, observational study conducted in seven countries including 617 patients who received ≥48 h of ceftolozane/tazobactam. Medical-record data were collected up to 6 months before treatment and 30 days after the final dose or until death. This analysis describes clinical outcomes and healthcare resource use in patients with sepsis or who were immunocompromised, specifically in patients with hematologic malignancy with and without solid tumor, febrile neutropenia, and solid organ transplant patients. Results: Clinical success ranged from 50.0% in patients with hematologic malignancy and solid tumor to 69.4% in 38 patients with febrile neutropenia. All-cause in-hospital mortality was 23.1–42.9%, with the lowest rates in patients with solid organ transplant. ICU admission was 46.4–68.2% across subpopulations (excluding febrile neutropenia) with the lowest rates in patients with hematologic malignancy. ICU length of stay was lowest within transplant patients (9 days) and highest within the hematologic malignancy and solid tumor population (32 days). Conclusions: The results from this sub analysis of SPECTRA showed that ceftolozane/tazobactam was associated with clinical success in the selected immunocompromised and sepsis patient populations and may lead to reduced morbidity, mortality, and healthcare-resource use. Further research is required to standardize treatment protocols and improve patient outcomes. Full article

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21 pages, 905 KB

Open AccessArticle

Barriers and Facilitators in the Implementation of a Syndromic Antibiogram for Pediatric Patients Hospitalized in Maputo, Mozambique: A Qualitative Study Using the Dynamic Adaptation Process (DAP) Framework

by Darlenne B. Kenga, Troy D. Moon, Mohsin Sidat, Valéria Chicamba, Andrea Ntanga Kenga, Yara Manjate, Dércio Nhanala, Inês C. Caetano, Ramígio Pololo, Olga Cambaco and Jahit Sacarlal

Antibiotics 2026, 15(2), 178; https://doi.org/10.3390/antibiotics15020178 - 6 Feb 2026

Abstract

Introduction: The global rise in antimicrobial resistance poses a growing threat to public health, particularly in low- and middle-income countries where diagnostic capacity and surveillance systems remain limited. In these settings, optimizing empiric antibiotic prescribing is critical, and syndromic antibiograms offer a promising [...] Read more.

Introduction: The global rise in antimicrobial resistance poses a growing threat to public health, particularly in low- and middle-income countries where diagnostic capacity and surveillance systems remain limited. In these settings, optimizing empiric antibiotic prescribing is critical, and syndromic antibiograms offer a promising approach to support evidence-based decision-making. This study examines anticipated barriers and facilitators to the adoption of syndromic antibiograms from the perspectives of pediatric clinicians and laboratory professionals at Maputo Central Hospital in Mozambique. Methods: Guided by the Dynamic Adaptation Process (DAP) framework, this qualitative study used semi-structured interviews with eighteen healthcare professionals to explore empiric antibiotic prescribing practices, perceptions of syndromic antibiograms, and system-level barriers and facilitators. Data were analyzed thematically using deductive codes derived from the DAP framework alongside inductive codes generated from participants’ narratives. Results: Barriers were identified at individual, organizational, and systems levels. Individual barriers included limited awareness, reliance on traditional practices, and resistance to change. Organizational barriers included weak leadership support, insufficient training, poor communication between clinicians and laboratory staff, suboptimal sample collection, heavy workloads, and staff shortages. Systems-level barriers comprised shortages of laboratory supplies and medicines, delays in laboratory results, and weak monitoring mechanisms. Facilitators included health worker motivation for evidence-based practice, organizational collaboration, peer and team support, and the presence of influential champions. Systems-level enablers included functional laboratory services, supportive institutional environments, alignment with clinical guidelines, and recognition of clinical utility. Conclusions: Successful implementation of syndromic antibiograms in LMIC will require addressing systemic and organizational barriers while fostering professional motivation, collaboration, and institutional support. Sustainable integration will depend on coordinated strategies—including resource strengthening, continuous training, supportive leadership, and structured monitoring—that collectively strengthen antimicrobial stewardship and inform health policy. Full article

(This article belongs to the Section Antibiotics Use and Antimicrobial Stewardship)

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17 pages, 1658 KB

Open AccessArticle

Liposomal Encapsulation Reduces the Cytotoxic Effects of Gramicidin S in Monolayer and Spheroid Fibroblast Cultures

by Ihor Perepelytsia, Galyna Bozhok, Volodymyr Berest, Valentina Gallo, Marco Pizzi, Larysa Sichevska and Oleksii Skorokhod

Antibiotics 2026, 15(2), 177; https://doi.org/10.3390/antibiotics15020177 - 6 Feb 2026

Abstract

Background/Objectives: Gramicidin S (GS) is a cyclic antimicrobial peptide with strong antibacterial activity but significant cytotoxicity toward mammalian cells. This study evaluated GS-induced cytotoxicity in L929 fibroblast cells using both traditional 2D monolayer cultures and more physiologically relevant 3D spheroid models, and assessed [...] Read more.

Background/Objectives: Gramicidin S (GS) is a cyclic antimicrobial peptide with strong antibacterial activity but significant cytotoxicity toward mammalian cells. This study evaluated GS-induced cytotoxicity in L929 fibroblast cells using both traditional 2D monolayer cultures and more physiologically relevant 3D spheroid models, and assessed whether liposomal encapsulation could mitigate toxicity and improve biocompatibility. Methods: L929 cells were cultured in monolayers and spheroids and treated with free GS or GS encapsulated in liposomes of varying lipid compositions. Cell viability and morphology were evaluated after 24 h of exposure using standard cytotoxicity assays. Results: Control liposomes, regardless of tested lipid type or concentration, showed no adverse effects on cell morphology or viability. Free GS caused pronounced, dose-dependent cytotoxicity in monolayers, decreasing viability to 11.0 ± 1.9% and 0.5 ± 1.1% at 50 and 75 µg/mL, respectively. By contrast, encapsulation in liposomes significantly reduced toxicity (p < 0.05), preserving 80.3–82.2% viability at 75 µg/mL depending on formulation, corresponding to protection factors exceeding 160-fold (80.3% vs. 0.5%). Spheroid cultures showed slightly higher resistance to GS; free GS reduced viability to 2.9%, while liposomal GS preserved it above 84.8%, depending on lipid composition. Conclusions: Liposomal encapsulation effectively reduces GS-induced cytotoxicity, likely by limiting direct membrane disruption. Moreover, spheroid models provide a more physiologically relevant and predictive platform for toxicity testing, while the results support nanoliposomes as a practical delivery strategy to enhance the safety of antimicrobial peptides during preclinical development. Full article

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18 pages, 1403 KB

Open AccessReview

Bloodstream Infections Due to Carbapenemase-Producing Escherichia coli: A Comprehensive Review

by Maria Scrascia, Adriana Antonina Tempesta, Viviana Cafiso, Carlo Pazzani and Maria Lina Mezzatesta

Antibiotics 2026, 15(2), 176; https://doi.org/10.3390/antibiotics15020176 - 5 Feb 2026

Abstract

Background/Objectives: Carbapenemase-producing Escherichia coli (CP-Ec) has emerged as an important contributor to the global crisis of antimicrobial resistance. Although less prevalent than carbapenemase-producing Klebsiella pneumoniae, CP-Ec exhibits marked genomic plasticity, efficient plasmid-mediated dissemination, and increasing involvement in bloodstream infections. This comprehensive review [...] Read more.

Background/Objectives: Carbapenemase-producing Escherichia coli (CP-Ec) has emerged as an important contributor to the global crisis of antimicrobial resistance. Although less prevalent than carbapenemase-producing Klebsiella pneumoniae, CP-Ec exhibits marked genomic plasticity, efficient plasmid-mediated dissemination, and increasing involvement in bloodstream infections. This comprehensive review summarizes the global epidemiology, molecular features, treatment options, clonal structure and transmission dynamics of CP-Ec. Particular attention is given to the expanding repertoire of NDM, OXA-48-like, and KPC carbapenemases and their associated plasmid backbones. Key high-risk clones, including ST410, ST167 and ST131, are highlighted as drivers of international spread. Conclusions and Future Directions: CP-Ec bloodstream infections represent a growing clinical challenge, often associated with severe outcomes and limited therapeutic options, particularly for NDM producers. The emergence of treatment failures with last-resort agents further underscores the need for improved management strategies. Strengthened global surveillance, integration of genomic epidemiology, optimized antimicrobial stewardship, and targeted infection control measures are essential to limit the dissemination of CP-Ec and mitigate its impact on human health. Full article

(This article belongs to the Special Issue Pharmacologic Management of MDR Respiratory and Bacteraemic Infections)

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22 pages, 4716 KB

Open AccessArticle

Appraisal of Multidrug-Resistant Listeria monocytogenes and Salmonella spp. Recovered from Commercial Meat Samples in the Eastern Cape, South Africa: Implications for Public Health Safety

by Luyanda Msolo, Zanda Mbiko, Sindisiwe Nokhatyana and Antony Ifeanyi Okoh

Antibiotics 2026, 15(2), 175; https://doi.org/10.3390/antibiotics15020175 - 5 Feb 2026

Abstract

Background: Multidrug-resistant bacteria have quadrupled globally, impacting effective treatment of infectious diseases. A growing concern is that many Gram-negative and Gram-positive bacteria harbor genes conferring resistance to various antibiotics including colistin. The alarming emergence of colistin resistance is exacerbated by the growing [...] Read more.

Background: Multidrug-resistant bacteria have quadrupled globally, impacting effective treatment of infectious diseases. A growing concern is that many Gram-negative and Gram-positive bacteria harbor genes conferring resistance to various antibiotics including colistin. The alarming emergence of colistin resistance is exacerbated by the growing threat of MDR Salmonella species and Listeria monocytogenes (LMO), which pose an escalating risk to global public health. Materials and Methods: In the present study, red meat samples were collected from randomly selected key retail markets in the Eastern Cape province, South Africa, and were evaluated for the incidence of LMO and the Salmonella species using standard culture-based and molecular methods. The confirmed isolates were subjected to antibiotic susceptibility testing. Results: This study demonstrated the occurrence of multidrug-resistant LMO (62%) and Salmonella species (spp.) (58%) in the red meat specimen. There were high resistance rates in both LMO and Salmonella isolates, with LMO exhibiting resistance to penicillin (89%), colistin (81%), nitrofurantoin (78%), and erythromycin (29%), while Salmonella showed resistance to trimethoprim (96.87%), tetracycline, and colistin (90.62%). Antibiotic resistance genes were also detected including BlaTem, erm, Sul1, Sul2 and mcr 1–6. Notably, Salmonella did not harbor any mcr genes that were screened in this study, whereas Listeria isolates harbored the mcr 2 (10%), 3 (7%), 4 (10%), and 6 (3%), with mcr 5 being the most prevalent with 57%. Conclusions: These findings highlight a threat to food security and public health, emphasizing the need for sturdier food handling procedures to ensure safety, enhanced antimicrobial stewardship, and alternative therapeutic strategies to combat antibiotic-resistant pathogens. Full article

(This article belongs to the Special Issue Antibiotic Surveillance and Rational Use in Special Populations: Enhancing Stewardship for Vulnerable Groups)

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17 pages, 710 KB

Open AccessArticle

Genomic Characterisation of Antibiotic-Resistant Escherichia coli from an Intensive Poultry Production System in the uMgungundlovu District, KwaZulu-Natal, South Africa: A Snapshot

by Nelisiwe S. Gumede, Joshua Mbanga, Charles Hunter, Melissa Ramtahal, Sabiha Y. Essack and Linda A. Bester

Antibiotics 2026, 15(2), 174; https://doi.org/10.3390/antibiotics15020174 - 5 Feb 2026

Abstract

Background: Intensive poultry production systems can act as reservoirs for antibiotic-resistant and multidrug-resistant (MDR) Escherichia coli, posing a public health risk through food and environmental transmission. Methods: This study investigated the genomic characteristics of antibiotic-resistant E. coli isolated from an intensive [...] Read more.

Background: Intensive poultry production systems can act as reservoirs for antibiotic-resistant and multidrug-resistant (MDR) Escherichia coli, posing a public health risk through food and environmental transmission. Methods: This study investigated the genomic characteristics of antibiotic-resistant E. coli isolated from an intensive poultry production system in the uMgungundlovu District, KwaZulu-Natal, South Africa. Chicken litter, wastewater, and floor swab samples were collected over three consecutive production cycles. Putative E. coli isolates were detected using the Colilert-18 system, cultured on eosin methylene blue agar, and genomically confirmed by quantitative PCR (q-PCR) targeting the uidA gene. Whole genome sequencing was performed using the Illumina MiSeq platform, followed by bioinformatic analyses to assess resistance genes, mobile genetic elements, and phylogenetic relationships. Results: Of 150 presumptive E. coli, 70 were genomically confirmed as E. coli and resistant to at least one antibiotic, with 74% exhibiting multidrug resistance. Resistance was highest to tetracycline (100%), ampicillin (94%), and trimethoprim–sulfamethoxazole (76%), while ciprofloxacin resistance was rare (3%). Genomic analysis identified multiple antibiotic resistance genes conferring resistance to fluoroquinolones, β-lactams, aminoglycosides, amphenicols, fosfomycin, and sulfonamides, as well as the disinfectant resistance gene qacI. These genes were frequently associated with mobile genetic elements, including plasmids, integrons, transposons, and insertion sequences. Predominant sequence types included ST155, ST48, ST1286, and ST602, with phylogenetic relatedness to poultry-associated isolates from Cameroon, Ghana, Nigeria, and Tanzania, as well as environmental E. coli strains previously identified in South Africa and Ghana. Conclusions: The detection of diverse, mobile MDR E. coli lineages in poultry environments clearly signals a substantial risk for resistance gene dissemination into the food chain and surrounding ecosystems. Immediate attention and intervention are warranted to mitigate public health threats. Full article

(This article belongs to the Special Issue Antibiotics Use in Farms, 3rd Edition)

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15 pages, 829 KB

Open AccessArticle

In Vitro Antimicrobial Potential of Different Platelet Concentrates Against Eight Clinically Relevant Oral Pathobionts

by Ellen E. Jansen, Zahra Hejazi, Andreas Braun, Patrick Jansen and Georg Conrads

Antibiotics 2026, 15(2), 173; https://doi.org/10.3390/antibiotics15020173 - 5 Feb 2026

Abstract

Background/Objectives: Oral infections are caused by a wide spectrum of bacterial and fungal species and remain clinically challenging, particularly against the background of increasing antimicrobial resistance and efforts to reduce antibiotic use in dentistry. Platelet concentrates are widely applied in periodontal and oral [...] Read more.

Background/Objectives: Oral infections are caused by a wide spectrum of bacterial and fungal species and remain clinically challenging, particularly against the background of increasing antimicrobial resistance and efforts to reduce antibiotic use in dentistry. Platelet concentrates are widely applied in periodontal and oral surgery due to their regenerative and immunomodulatory properties, and accumulating evidence suggests additional antimicrobial effects. This study evaluated the antimicrobial activity of platelet-rich plasma (PRP), platelet-rich fibrin (PRF), and injectable PRF (i-PRF) against clinically relevant oral microorganisms. Methods: PRP, PRF, and i-PRF were prepared from venous blood of five healthy donors and evaluated using diffusion-dependent, qualitative-semiquantitative agar diffusion assays against Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Staphylococcus aureus, Streptococcus mutans, Streptococcus mitis, Enterococcus faecalis, and Candida albicans, with inhibition zones assessed after species-specific incubation times. Chlorhexidine (2%) and amoxicillin served as positive controls and NaCl (0.9%) as negative control. Inhibition zones were digitally quantified and analyzed using non-parametric statistics (Kruskal–Wallis, Friedmann) due to skewed distributions and frequent zero values. Results: All platelet concentrates demonstrated microorganism-dependent inhibition zones in vitro. Overall, i-PRF demonstrated the strongest inhibitory effect across all pathogens (p < 0.001). Significant differences were detected for E. faecalis and C. albicans, where i-PRF produced markedly larger inhibition zones compared to PRP and PRF. Descriptively, anaerobic periodontal pathogens and S. aureus tended to be more susceptible, while streptococci and C. albicans demonstrated lower inhibition. Conclusions: These findings support a potential adjunctive antimicrobial role of platelet-derived preparations in dental infection management but should be interpreted with caution, as agar diffusion results do not necessarily reflect clinical performance. Full article

(This article belongs to the Special Issue Antimicrobial Biomaterials for Dentistry)

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19 pages, 3240 KB

Open AccessArticle

Cost Analysis of the Belgian National Antimicrobial Resistance Monitoring in Livestock: Effects on Sampling Design and Statistical Performance

by Maria Eleni Filippitzi, Adrien de Fraipont, Mickaël Cargnel, Céline Guillaume and Jean Baptiste Hanon

Antibiotics 2026, 15(2), 172; https://doi.org/10.3390/antibiotics15020172 - 5 Feb 2026

Abstract

Background/Objectives: As part of the European Union’s harmonized monitoring framework, Belgium conducts antimicrobial resistance (AMR) monitoring in commensal bacteria from livestock. The aim of this study was to conduct a cost analysis of the national AMR monitoring in livestock, and to explore sampling [...] Read more.

Background/Objectives: As part of the European Union’s harmonized monitoring framework, Belgium conducts antimicrobial resistance (AMR) monitoring in commensal bacteria from livestock. The aim of this study was to conduct a cost analysis of the national AMR monitoring in livestock, and to explore sampling size scenarios in relation to their associated costs and statistical performance (power and confidence) of monitoring. Methods: To our knowledge, this is the first published cost evaluation using unit cost aggregation of a national AMR monitoring program in animals. Results: The testing of the different sample size scenarios showed that if the sample size increases, the costs increase linearly. A sample size increase of 10 samples/isolates (e.g., from 170 to 180) can increase the yearly total costs per animal species by 5.2%. Moreover, the testing of the different scenarios showed that if the sample size increases, the power and the confidence level also increase, providing a higher level of trust in the results of the monitoring program. The highest total monitoring costs per animal category were estimated for fattening pigs, broilers and veal calves (over 18% of total costs each, using 2024 data). Among the various monitoring activities, antimicrobial susceptibility testing emerged as the costliest component, representing 50.2% of the total monitoring costs. Conclusions: The approach presented allows it to be used by other countries aiming to estimate the cost of their national AMR monitoring in animals or other similar activities. This economic and scenario testing analysis can be used to suggest informed suggestions to improve AMR monitoring in animals. Full article

(This article belongs to the Special Issue Antimicrobial Resistance in Veterinary Science, 2nd Edition)

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11 pages, 2082 KB

Open AccessArticle

Evaluating Early Macrolide Therapy in Pediatric Campylobacter Enterocolitis: A Comparative Study

by Ho Jung Choi, Yoon Kyung Cho, Ye Ji Kim, Hyun Mi Kang, Dae Chul Jeong and In Hyuk Yoo

Antibiotics 2026, 15(2), 171; https://doi.org/10.3390/antibiotics15020171 - 5 Feb 2026

Abstract

Background/Objectives: Azithromycin is widely recommended as the first-line treatment for pediatric Campylobacter enterocolitis, although supporting evidence is limited and there is a lack of studies evaluating the efficacy of other macrolide antibiotics. This study aims to assess the effectiveness of starting macrolide therapy [...] Read more.

Background/Objectives: Azithromycin is widely recommended as the first-line treatment for pediatric Campylobacter enterocolitis, although supporting evidence is limited and there is a lack of studies evaluating the efficacy of other macrolide antibiotics. This study aims to assess the effectiveness of starting macrolide therapy within three days of symptom onset in pediatric patients with Campylobacter enterocolitis. Methods: Pediatric patients under 19 years of age with a new diagnosis of Campylobacter enterocolitis were enrolled and randomly assigned to receive macrolide antibiotic treatment with either azithromycin or clarithromycin in a 1:1 ratio. Additionally, a retrospective historical cohort of pediatric patients diagnosed with Campylobacter enterocolitis prior to the study period, who did not receive macrolide antibiotics, was retrospectively reviewed for comparison. This dual approach allowed for the evaluation of macrolide therapy’s effectiveness against untreated cases. Results: The study included 27 patients in the macrolide group and 37 patients in the non-macrolide group. Baseline demographic and clinical characteristics were comparable between groups. Early macrolide therapy was associated with reduced hospital stay (3.8 ± 0.7 vs. 4.5 ± 0.9 days), shorter duration of diarrhea (1.8 ± 1.2 vs. 3.4 ± 0.7 days, p < 0.001), and shorter duration of fever (1.1 ± 0.6 vs. 2.8 ± 1.0 days, p < 0.001). No significant difference was observed in the duration of vomiting (p = 0.061). Conclusions: Early initiation of macrolide antibiotics in children with Campylobacter enterocolitis significantly accelerated complete clinical resolution and shortened hospitalization, particularly by hastening the resolution of diarrhea, fever, and abdominal pain. These findings support the use of early macrolide therapy for pediatric Campylobacter enterocolitis. Full article

(This article belongs to the Special Issue Antibiotic Choices for Pediatric Infections)

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16 pages, 1199 KB

Open AccessSystematic Review

Exploring the Effectiveness of Imipenem/Relebactam in Patients with Antimicrobial-Resistant Hospital-Acquired Infections: Findings from Systematic Literature Reviews

by Ryan K. Shields, Ignacio Martin-Loeches, Emre Yücel, Shalini Bagga, Vaneet Pal Kaur Khurana, Prashant Soni, Prateek Das and Carolyn Cameron

Antibiotics 2026, 15(2), 170; https://doi.org/10.3390/antibiotics15020170 - 5 Feb 2026

Abstract

Introduction: Infections attributed to multidrug-resistant organisms have resulted in a significant clinical burden, high mortality, and excessive costs. Identifying the most appropriate and efficacious treatments will aid in reducing these burdens. Imipenem/cilastatin + relebactam (I/R) is used against multidrug-resistant infections providing an alternative [...] Read more.

Introduction: Infections attributed to multidrug-resistant organisms have resulted in a significant clinical burden, high mortality, and excessive costs. Identifying the most appropriate and efficacious treatments will aid in reducing these burdens. Imipenem/cilastatin + relebactam (I/R) is used against multidrug-resistant infections providing an alternative option which may support patients where traditional treatments are no longer effective. Objective: The objective was to evaluate the efficacy of I/R for complicated urinary tract infections, complicated intra-abdominal infections, hospital-acquired bacterial pneumonia, and ventilator-associated bacterial pneumonia, based on data aggregated from randomized controlled trials. Method: Two systematic literature reviews were conducted to include randomized controlled trials which aligned with the inclusion criteria reporting on the efficacy of I/R against placebo or other comparators such as piperacillin/tazobactam or colistin. The outcomes of interest were mortality, clinical response, and microbiological response. Results: The results found reduced mortality and comparable clinical and microbiological response with I/R versus its comparators. I/R displayed the largest favorable clinical and microbiological responses within high-risk populations, including those with severe renal impairment when compared with piperacillin/tazobactam. Conclusions: These findings support the efficacy of I/R for key Gram-negative infections, particularly within vulnerable patient populations. Despite the favorable outcomes reported, there is a need for further real-world evidence generation to support the efficacy of I/R to aid in standardizing treatment guidelines and reducing the clinical and economic burden associated with multidrug-resistant bacterial infections. Full article

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14 pages, 643 KB

Open AccessArticle

Acquisition Origin Matters: Clinical, Microbiological and Immunological Characteristics and Treatment Effects in Community- vs. Hospital-Acquired Septic Shock

by Irene Coloretti, Martina Tosi, Emanuela Biagioni, Federica Morselli, Elena Munari, Jacopo Bertolini, Sara Ferrari, Marianna Meschiari, Erica Franceschini, Nathan D. Nielsen, Stefano Busani and Massimo Girardis

Antibiotics 2026, 15(2), 169; https://doi.org/10.3390/antibiotics15020169 - 5 Feb 2026

Abstract

Background: Septic shock is a leading cause of mortality worldwide, with community-acquired (CA) and hospital-acquired (HA) infections representing distinct clinical entities. The differences in clinical characteristics, immune response profiles, and effects of sepsis treatments between CA and HA septic shock have not [...] Read more.

Background: Septic shock is a leading cause of mortality worldwide, with community-acquired (CA) and hospital-acquired (HA) infections representing distinct clinical entities. The differences in clinical characteristics, immune response profiles, and effects of sepsis treatments between CA and HA septic shock have not been fully elucidated. Methods: This retrospective cohort study included 726 adults with septic shock who were admitted to two ICUs at Modena University Hospital between January 2006 and September 2024. Patients were classified as having CA or HA septic shock based on the origin of the infection. Clinical, microbiological, and immunological data, treatments, and outcomes were analysed. Immune cell dynamics were assessed during the first week after the onset of the shock. Multivariable Cox regression models were used to identify predictors and the effects of treatment on ICU mortality. Results: Among 344 patients with CA and 382 with HA septic shock, those with CA had higher severity scores but lower ICU and in-hospital mortality. Patients with HA exhibited a higher prevalence of multidrug-resistant organisms and more comorbidities. Immunologically, CA survivors showed increasing lymphocyte counts over time, whereas HA survivors mainly demonstrated recovery in T helper cells. Therapeutic strategies were similar between groups; however, continuous renal replacement therapy was more frequent in patients with HA. Neither appropriate empiric antibiotics nor steroids or immunoglobulin therapy independently improved mortality in the multivariate analyses. Conclusions: CA and HA septic shock differ significantly in terms of clinical severity, microbiological aetiology, immune recovery patterns, and outcomes. The lack of mortality benefit from standard treatments highlights the need for personalised management strategies that integrate clinical, immunological, and microbiological data to optimise care in septic shock subpopulations. Full article

(This article belongs to the Special Issue Antimicrobial Resistance in the Community Setting: The Other Side of the Coin)

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20 pages, 3501 KB

Open AccessArticle

Target Fidelity and Failure: Structure–Activity Relationship of High-Molecular-Mass Penicillin-Binding Proteins (HMM-PBPs) in Refractory Granulicatella adiacens Endocarditis

by Paola Conti, Alberto Pagotto, Sebastiano A. Fortuna, Alessandra Giardina, Grete F. Privitera, Ester Rosa, Assunta Sartor, Carlo Tascini and Floriana Campanile

Antibiotics 2026, 15(2), 168; https://doi.org/10.3390/antibiotics15020168 - 5 Feb 2026

Abstract

Background/Objectives: Granulicatella adiacens infective endocarditis is conventionally managed with penicillin, ampicillin, or ceftriaxone in combination with gentamicin, although double beta-lactam regiments have been proposed a safer alternative to reduce aminoglycoside-associated nephrotoxicity. To date, the High-Molecular-Mass Penicillin-Binding Proteins (HMM-PBPs) of G. adiacens and [...] Read more.

Background/Objectives: Granulicatella adiacens infective endocarditis is conventionally managed with penicillin, ampicillin, or ceftriaxone in combination with gentamicin, although double beta-lactam regiments have been proposed a safer alternative to reduce aminoglycoside-associated nephrotoxicity. To date, the High-Molecular-Mass Penicillin-Binding Proteins (HMM-PBPs) of G. adiacens and their affinities for beta-lactam antibiotics have not been previously characterized. This study investigated the HMM-PBP profile of G. adiacens, with particular interest on sequence alterations and beta-lactam binding properties, both as single agents and in combination. Methods: Beta-lactam activity, synergistic interactions and PBP binding affinities were evaluated in a clinical isolate (IS 48) and compared with those in the reference strain ATCC 49175. Binding of PBPs to ampicillin, ceftriaxone, and ceftobiprole, alone or in combination, was investigated by Bocillin-FL labeling. PBP homology and conserved active-sites motifs were assessed by sequence alignment, and pbp gene mutations were identified by whole-genome sequencing. Results: The clinical isolate was non-susceptible to ampicillin, resistant to ceftriaxone and exhibited higher minimum inhibitory concentrations (MICs) for ceftobiprole relative to the fully susceptible ATCC reference strain. Five HMM PBPs with high enterococcal homology, were identified. In the IS 48 isolate, the class A PBP showed distinct amino acid substitutions in proximity to the catalytic centers. Despite these alterations, PBP1A and PBP2A were strongly inhibited by the tested beta-lactams, whereas PBP2 and PBP2B demonstrated low acylation rates. Combination of ampicillin with either ceftobiprole or ceftriaxone resulted in enhanced acylation of the three bifunctional HMM PBPs compared with monotreatment. IC₅₀ values were consistently higher for the IS 48 clinical isolate, suggesting decreased target availability and/or reduced beta-lactam affinity under clinical conditions. Conclusions: The resistance phenotype of G. adiacens clinical isolate appears to be primarily associated with altered PBP beta-lactam interactions. Nonetheless, beta-lactam combination regimes remain effective by achieving substantial inhibition of key HMM-PBPs involved in peptidoglycan synthesis, thereby supporting the rationale for dual beta-lactam therapy in this setting. Full article

(This article belongs to the Special Issue Progress and Challenges in the Antibiotic Treatment of Infections)

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37 pages, 1823 KB

Open AccessArticle

Phenotypic Antimicrobial Resistance of Some Bacterial Strains Isolated from Red Foxes (Vulpes vulpes) in Western Romania

by Alex-Cristian Moza, Iulia-Maria Bucur, Kalman Imre, Sebastian Alexandru Popa, Alexandra Adriana Grigoreanu, Ana-Maria Plotuna, Andrei Alexandru Ivan, Narcisa Geanina Mederle, Andreea-Talida Tîrziu and Emil Tîrziu

Antibiotics 2026, 15(2), 167; https://doi.org/10.3390/antibiotics15020167 - 4 Feb 2026

Abstract

Background/Objectives: Recent investigations point to red foxes (Vulpes vulpes) as a very potent sentinel species for monitoring the dissemination of antimicrobial bacteria in wildlife habitats. Methods: This study investigated antimicrobial resistance in red foxes from 16 hunting grounds (peri-urban and peri-rural) [...] Read more.

Background/Objectives: Recent investigations point to red foxes (Vulpes vulpes) as a very potent sentinel species for monitoring the dissemination of antimicrobial bacteria in wildlife habitats. Methods: This study investigated antimicrobial resistance in red foxes from 16 hunting grounds (peri-urban and peri-rural) in western Romania, between 2022 and 2024, in order to evaluate the species as “One Health” sentinels at the wildlife–human–animal interface. During this period, 137 bacterial strains previously identified from 216 samples were phenotypically tested using both the Kirby–Bauer disk diffusion method and the Vitek 2 Compact system. Results: Among the Gram-negative isolates, particularly Escherichia coli and Salmonella enterica, notable antimicrobial resistance and multidrug-resistant (MDR) phenotypes were observed, including resistance to third-generation cephalosporins (ceftazidime) and reduced susceptibility to carbapenems. Resistance patterns observed in Proteus spp. largely reflected intrinsic resistance traits. Methicillin-resistant and MDR staphylococci (Staphylococcus aureus, S. pseudintermedius and S. sciuri) were detected in both peri-urban and peri-rural hunting grounds, with higher frequencies observed in peri-rural areas. Although MDR prevalence was slightly higher in peri-urban compared to peri-rural sites, no statistically significant association was identified between area of isolation and antimicrobial resistance or MDR status. Antimicrobial susceptibility results obtained by disk diffusion and the Vitek 2 Compact system showed a high level of concordance for antibiotics tested in common. Conclusions: Overall, these findings support the use of red foxes as effective One Health sentinels for monitoring environmental antimicrobial resistance occurrence across wildlife, domestic animals, and human-impacted habitats. Full article

(This article belongs to the Special Issue A One Health Approach to Antimicrobial Resistance, 2nd Edition)

14 pages, 454 KB

Open AccessArticle

Risk Factors and Outcomes of Extensively Drug-Resistant Gram-Negative Bacilli in Neonates with Late-Onset Sepsis

by Sanchat Sanchainara, Anucha Thatrimontrichai, Praew Chareesri, Pattima Pakhathirathien, Manapat Praditaukrit, Gunlawadee Maneenil and Supaporn Dissaneevate

Antibiotics 2026, 15(2), 166; https://doi.org/10.3390/antibiotics15020166 - 4 Feb 2026

Abstract

Background/Objective: To identify the risks and outcomes of extensively drug-resistant Gram-negative bacilli (XDR-GNB) in neonates. Methods: This retrospective case–control study (1995–2024) included neonates with late-onset sepsis (n = 132) and XDR-GNB bacteremia (n = 26) compared with those without [...] Read more.

Background/Objective: To identify the risks and outcomes of extensively drug-resistant Gram-negative bacilli (XDR-GNB) in neonates. Methods: This retrospective case–control study (1995–2024) included neonates with late-onset sepsis (n = 132) and XDR-GNB bacteremia (n = 26) compared with those without XDR-GNB (n = 106). Results: Median gestational age was 31 weeks and birth weight 1540 g. The prevalence of XDR-GNB was 19.7%. The most common XDR-GNB and non-XDR-GNB pathogens were Acinetobacter baumannii and Klebsiella pneumoniae. Sepsis onset occurred earlier in the XDR-GNB group than in the non-XDR-GNB group (7.0 vs. 12.5 days, p = 0.005). In multivariable analysis using Firth’s penalized likelihood method, the XDR-GNB group was more likely to have gastrointestinal anomalies (adjusted odds ratio 3.81, 95% confidence interval 1.24–12.01, p = 0.02) and history of umbilical arterial catheterization (adjusted odds ratio 3.04, 95% confidence interval 1.21–7.95, p = 0.02) compared to the non-XDR-GNB group. The XDR-GNB group had higher rates of septic shock (50.0% vs. 18.9%, p = 0.002) and inadequate empiric antimicrobial therapy (34.6% vs. 13.2%, p = 0.02). The non-susceptibility rates to third-generation cephalosporins, gentamicin, carbapenems, amikacin, and colistin were 83.3%, 58.3%, 48.1%, 30.4%, and 4.4%, respectively. Conclusions: Empirical colistin treatment is warranted for neonates in high-XDR environments who exhibit septic shock and have specific risk factors, such as gastrointestinal anomalies or the presence of an umbilical arterial catheter. Multimodal interventions, including antimicrobial stewardship programs, have been used to prevent or reduce the incidence of neonatal XDR-GNB sepsis. Full article

(This article belongs to the Special Issue Antimicrobial Stewardship in Neonatal Intensive Care)

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10 pages, 307 KB

Open AccessArticle

Cutibacterium acnes Culture Isolation Following Total Hip and Total Knee Arthroplasty

by Benjamin Levy, Alton Daley, Tracy Borsinger, Paul Werth and Wayne Moschetti

Antibiotics 2026, 15(2), 165; https://doi.org/10.3390/antibiotics15020165 - 4 Feb 2026

Abstract

Introduction: Cutibacterium acnes, a component of normal skin flora and a common commensal Gram-positive bacterium, presents a diagnostic challenge for arthroplasty surgeons. While Cutibacterium acnes (C. acnes) as a source of infection has been well characterized in shoulder surgery, its presentation and [...] Read more.

Introduction: Cutibacterium acnes, a component of normal skin flora and a common commensal Gram-positive bacterium, presents a diagnostic challenge for arthroplasty surgeons. While Cutibacterium acnes (C. acnes) as a source of infection has been well characterized in shoulder surgery, its presentation and clinical significance in total hip (THA) and total knee arthroplasty (TKA) remain less understood. Methods: A retrospective chart review identified patients with C. acnes culture positivity following THA or TKA. Demographics, laboratory values, and microbiologic data were collected. Statistical comparisons were performed using t-tests and chi-squared analysis. One-year outcomes were evaluated using the Musculoskeletal Infection Society Outcome Reporting Tool (MSIS ORT) criteria among patients undergoing further surgical intervention. Results: Twenty-nine patients with C. acnes-positive cultures were identified (21 THA, 8 TKA); 15 (52%) were polymicrobial. Ten THA patients (47.6%) and seven TKA patients (87.5%) met MSIS criteria for infection at the time of presentation. Mean time to culture positivity was similar between THA (6.8 days) and TKA (7.4 days; p = 0.57). Sonicated cultures were positive in 24% of THA and 12.5% of TKA cases. Mean ESR was 36.4 mm/h for THA and 51.5 mm/h for TKA (p = 0.21); mean C-reactive protein (CRP) was 35.2 and 36.8 mg/dL, respectively (p = 0.95). Mean synovial cell counts were 27,055 for THA and 22,194 for TKA, with polymorphonuclear cells (PMN) percentages of 68% and 73.9% (p = 0.72, 0.70). Monomicrobial infections demonstrated a mean cell count of 24,143 with 58.9% PMNs, compared to 25,903 and 78.8% in polymicrobial cases. At one year, 72% of patients undergoing subsequent surgery achieved successful outcomes. Higher ASA classification was the only significant predictor of failure (mean 3.0 vs. 2.75). Conclusions: C. acnes-associated THA and TKA infections often present with delayed culture growth, mild inflammatory markers, and frequent polymicrobial involvement. At one-year, patients with available follow-up who undergo surgical management experience favorable outcomes, with 72% achieving MSIS ORT success. Full article

(This article belongs to the Special Issue Periprosthetic Joint Infection: Understanding the Epidemiology, Pathogenesis, Diagnosis and Treatment Options)

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