Microbiology Research

The global rise of multidrug resistance (MDR) across bacterial pathogens poses a severe threat to public health, with the food chain serving as a critical reservoir and transmission route for resistant clones. This study investigated the genomic epidemiology of Staphylococcus aureus in retail pork from Beijing, China, and Copenhagen, Denmark, with a focus on MDR patterns and associated genetic elements. Among 134 isolates, the livestock-associated clonal complex CC398 was the dominant lineage (24.63%) and exhibited a high burden of MDR (48.48%), carrying resistance genes to β-lactams (blaZ and mecA), tetracyclines (tetM and tetK), and aminoglycosides. Notably, MRSA isolates displayed a significantly higher MDR prevalence (73.53%) compared to MSSA isolates (18.00%), underscoring methicillin resistance as a key marker for broader resistance phenotypes. Phylogenetic analysis revealed the segregation of CC398 into distinct sub-lineages, with the livestock-associated branch consistently linked to a characteristic tetracycline–β-lactam MDR profile. Furthermore, high frequencies of mobile genetic elements, such as the rep16 plasmid, were associated with MDR dissemination in CC398. These findings highlight retail meat as an important reservoir for MDR S. aureus and illustrate how livestock-adapted clones contribute to the environmental burden of antimicrobial resistance. This study underscores the need for integrated One Health surveillance that connects veterinary, food safety, and human health sectors to monitor and contain the spread of MDR bacteria across ecological niches.

The highly destructive pathogenic processes in patients with periodontitis are attributed to the presence of subgingival biofilms comprising key periodontal pathogens, such as Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia, as well as other periodontopathogens including Fusobacterium nucleatum, Selenomonas spp., Centipeda spp., and Campylobacter spp. Considering the vast microbial diversity in periodontitis, we aimed to analyze the presence of various bacterial species in subgingival dental plaque, with a special focus on Selenomonas spp. We first developed a phylogenetic tree for Selenomonas–Veillonella clusters, using in silico analysis followed by fluorescence in situ hybridization (FISH) on subgingival dental plaque samples from 22 patients with a history of chronic periodontitis, by using specific 16S rRNA oligonucleotide probes. These oligonucleotide probes’ specificity and hybridization conditions were determined on previously characterized bacterial strains. Qualitative and quantitative analysis of FISH slides was carried out by using an epifluorescence microscope. The majority of the patient samples showed high fluorescence signals with the oligonucleotide probes SEL1150, Sspu439, and SEL1469 (specific for Selenomonas spp.), ACI623 (identifying Selenomonas, Veillonella, and Dialister spp.), Tfor127 (T. forsythia) and L-Pgin1006-23 (P. gingivalis). SEL1150 showed specificity for bacterial species in the subclusters A, B, and C, namely S. dianae, S. infelix, S. flueggei, C. periodontii, S. artemidis, S. noxia, and S. sputigena; Sspu439 for S. sputigena; SEL1469 for subclusters A and B, and for S. sputigena; ACI623 for bacterial species in subclusters C and F, namely the S. sputigena and Veillonella species. The experimentally observed specificities of the oligonucleotide probes corresponded with our in silico analysis. Selenomonas spp. may play a role in the subgingival microbiome of periodontitis and contribute to the disease process. Targeting Selenomonas spp. with specific therapeutic strategies could offer new insights into the management of periodontitis. However, further studies are needed to determine a definite functional significance.

Obtaining enzymes through bioconversion depends on a complex relationship between the microorganisms and the biomass used. Here, we evaluate xylanase production by diverse actinobacterial species, cultivated using xylan as the sole carbon source and complex media containing sorghum as the substrate. Fifty-three actinobacteria were tested for xylanase production in a solid medium. Seventeen strains produced xylanase and were tested for their ability to produce xylanase, total cellulases (filter paper activity, FPase), and endoglycanase in submerged culture using a defined liquid medium. The best xylanase-producing species was Streptomyces capoamus, yielding 24 IU·mL⁻¹. For FPase, Streptomyces sp. showed the highest yield (1.12 IU·mL⁻¹); for endoglycanase, the best producer was Streptomyces ossamyceticus (0.99 IU·mL⁻¹). When sweet sorghum was used alone, S. curacoi, S. ossamyceticus, and S. capoamus showed xylanase activities of 4.5 IU·mL⁻¹, 4.4 IU·mL⁻¹, and 0.8 IU·mL⁻¹, respectively. However, FPase activity was not detected under the assay conditions. The results showed that there is an intraspecific difference in xylanase, endoglucanase, and FPase production by actinobacteria, with the species S. curacoi, S. ossamyceticus, and S. capoamus able to use sorghum as a carbon source, demonstrating biotechnological potential.