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Pathogens, Volume 4, Issue 1 (March 2015) – 9 articles , Pages 1-156

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292 KiB  
Review
Phytogenic Compounds as Alternatives to In-Feed Antibiotics: Potentials and Challenges in Application
by Chengbo Yang, M.A. Kabir Chowdhury, Yongqing Huo and Joshua Gong
Pathogens 2015, 4(1), 137-156; https://doi.org/10.3390/pathogens4010137 - 23 Mar 2015
Cited by 215 | Viewed by 13565
Abstract
This article summarizes current experimental knowledge on the efficacy, possible mechanisms and feasibility in the application of phytogenic products as feed additives for food-producing animals. Phytogenic compounds comprise a wide range of plant-derived natural bioactive compounds and essential oils are a major group. [...] Read more.
This article summarizes current experimental knowledge on the efficacy, possible mechanisms and feasibility in the application of phytogenic products as feed additives for food-producing animals. Phytogenic compounds comprise a wide range of plant-derived natural bioactive compounds and essential oils are a major group. Numerous studies have demonstrated that phytogenic compounds have a variety of functions, including antimicrobial/antiviral, antioxidative and anti-inflammation effects and improvement in the palatability of feed and gut development/health. However, the mechanisms underlying their functions are still largely unclear. In the past, there has been a lack of consistency in the results from both laboratory and field studies, largely due to the varied composition of products, dosages, purities and growing conditions of animals used. The minimal inhibitory concentration (MIC) of phytogenic compounds required for controlling enteric pathogens may not guarantee the best feed intake, balanced immunity of animals and cost-effectiveness in animal production. The lipophilic nature of photogenic compounds also presents a challenge in effective delivery to the animal gut and this can partially be resolved by microencapsulation and combination with other compounds (synergistic effect). Interestingly, the effects of photogenic compounds on anti-inflammation, gut chemosensing and possible disruption of bacterial quorum sensing could explain a certain number of studies with different animal species for the better production performance of animals that have received phytogenic feed additives. It is obvious that phytogenic compounds have good potential as an alternative to antibiotics in feed for food animal production and the combination of different phytogenic compounds appears to be an approach to improve the efficacy and safety of phytogenic compounds in the application. It is our expectation that the recent development of high-throughput and “omics” technologies can significantly advance the studies on the mechanisms underlying phytogenic compounds’ functions and, therefore, guide the effective use of the compounds. Full article
(This article belongs to the Special Issue Alternatives to Antibiotics: Current Strategies and Future Prospects)
809 KiB  
Review
Biofilms in Infections of the Eye
by Paulo J. M. Bispo, Wolfgang Haas and Michael S. Gilmore
Pathogens 2015, 4(1), 111-136; https://doi.org/10.3390/pathogens4010111 - 23 Mar 2015
Cited by 108 | Viewed by 9379
Abstract
The ability to form biofilms in a variety of environments is a common trait of bacteria, and may represent one of the earliest defenses against predation. Biofilms are multicellular communities usually held together by a polymeric matrix, ranging from capsular material to cell [...] Read more.
The ability to form biofilms in a variety of environments is a common trait of bacteria, and may represent one of the earliest defenses against predation. Biofilms are multicellular communities usually held together by a polymeric matrix, ranging from capsular material to cell lysate. In a structure that imposes diffusion limits, environmental microgradients arise to which individual bacteria adapt their physiologies, resulting in the gamut of physiological diversity. Additionally, the proximity of cells within the biofilm creates the opportunity for coordinated behaviors through cell–cell communication using diffusible signals, the most well documented being quorum sensing. Biofilms form on abiotic or biotic surfaces, and because of that are associated with a large proportion of human infections. Biofilm formation imposes a limitation on the uses and design of ocular devices, such as intraocular lenses, posterior contact lenses, scleral buckles, conjunctival plugs, lacrimal intubation devices and orbital implants. In the absence of abiotic materials, biofilms have been observed on the capsule, and in the corneal stroma. As the evidence for the involvement of microbial biofilms in many ocular infections has become compelling, developing new strategies to prevent their formation or to eradicate them at the site of infection, has become a priority. Full article
(This article belongs to the Special Issue Biofilm-Based Nosocomial Infections)
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2649 KiB  
Article
TLR-2 Signaling Promotes IL-17A Production in CD4+CD25+Foxp3+ Regulatory Cells during Oropharyngeal Candidiasis
by Natarajan Bhaskaran, Samuel Cohen, Yifan Zhang, Aaron Weinberg and Pushpa Pandiyan
Pathogens 2015, 4(1), 90-110; https://doi.org/10.3390/pathogens4010090 - 17 Mar 2015
Cited by 37 | Viewed by 7598
Abstract
Recent studies show that CD4+CD25+Foxp3+ regulatory cells (Tregs) produce effector cytokines under inflammatory conditions. However, the direct role of microbial agents that serve as toll-like receptor (TLR) ligands in the induction of effector cytokines in T [...] Read more.
Recent studies show that CD4+CD25+Foxp3+ regulatory cells (Tregs) produce effector cytokines under inflammatory conditions. However, the direct role of microbial agents that serve as toll-like receptor (TLR) ligands in the induction of effector cytokines in Tregs is less clear. Here we show that CD4+Foxp3+Tregs produce the effector cytokine IL-17A during oropharyngeal candidiasis (OPC) and inflammatory bowel disease in a TLR-2/Myd88 signaling dependent manner. TLR-2 ligands promote proliferation in Tregs in the presence and absence of TCR signals and inflammatory cytokines in vitro. The proliferation is directly dependent on TLR-2 expression in Tregs. Consistent with this, Tlr2−/− mice harbor fewer thymically derived Tregs and peripheral Tregs under homeostatic conditions in vivo. However, under Th17 inducing conditions, IL-6 and TLR-2 signaling both in Tregs as well as antigen presenting cells (APC) are critical for maximal ROR-γt and IL-17A up-regulation in Foxp3+ Tregs. The minimal and transient loss of Foxp3 expression and suppressive properties are due to the presence of IL-6 in the milieu, but not the direct effect of TLR-2 signaling in Tregs. Taken together, our data reveal that TLR-2 signaling promotes not only proliferation, but also IL-17A in Tregs, depending on the cytokine milieu. These IL-17A producing Tregs may be relevant in mucosal infections and inflammation. Full article
(This article belongs to the Special Issue Candida Albicans Infections)
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458 KiB  
Review
Bacterial Adaptation during Chronic Respiratory Infections
by Louise Cullen and Siobhán McClean
Pathogens 2015, 4(1), 66-89; https://doi.org/10.3390/pathogens4010066 - 02 Mar 2015
Cited by 116 | Viewed by 13044
Abstract
Chronic lung infections are associated with increased morbidity and mortality for individuals with underlying respiratory conditions such as cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD). The process of chronic colonisation allows pathogens to adapt over time to cope with changing selection [...] Read more.
Chronic lung infections are associated with increased morbidity and mortality for individuals with underlying respiratory conditions such as cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD). The process of chronic colonisation allows pathogens to adapt over time to cope with changing selection pressures, co-infecting species and antimicrobial therapies. These adaptations can occur due to environmental pressures in the lung such as inflammatory responses, hypoxia, nutrient deficiency, osmolarity, low pH and antibiotic therapies. Phenotypic adaptations in bacterial pathogens from acute to chronic infection include, but are not limited to, antibiotic resistance, exopolysaccharide production (mucoidy), loss in motility, formation of small colony variants, increased mutation rate, quorum sensing and altered production of virulence factors associated with chronic infection. The evolution of Pseudomonas aeruginosa during chronic lung infection has been widely studied. More recently, the adaptations that other chronically colonising respiratory pathogens, including Staphylococcus aureus, Burkholderia cepacia complex and Haemophilus influenzae undergo during chronic infection have also been investigated. This review aims to examine the adaptations utilised by different bacterial pathogens to aid in their evolution from acute to chronic pathogens of the immunocompromised lung including CF and COPD. Full article
(This article belongs to the Special Issue Respiratory Pathogens)
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754 KiB  
Review
Animal Models of Chronic Hepatitis Delta Virus Infection Host–Virus Immunologic Interactions
by Rafael Aldabe, Lester Suárez-Amarán, Carla Usai and Gloria González-Aseguinolaza
Pathogens 2015, 4(1), 46-65; https://doi.org/10.3390/pathogens4010046 - 12 Feb 2015
Cited by 12 | Viewed by 9691
Abstract
Hepatitis delta virus (HDV) is a defective RNA virus that has an absolute requirement for a virus belonging to the hepadnaviridae family like hepatitis B virus (HBV) for its replication and formation of new virions. HDV infection is usually associated with a worsening [...] Read more.
Hepatitis delta virus (HDV) is a defective RNA virus that has an absolute requirement for a virus belonging to the hepadnaviridae family like hepatitis B virus (HBV) for its replication and formation of new virions. HDV infection is usually associated with a worsening of HBV-induced liver pathogenesis, which leads to more frequent cirrhosis, increased risk of hepatocellular carcinoma (HCC), and fulminant hepatitis. Importantly, no selective therapies are available for HDV infection. The mainstay of treatment for HDV infection is pegylated interferon alpha; however, response rates to this therapy are poor. A better knowledge of HDV–host cell interaction will help with the identification of novel therapeutic targets, which are urgently needed. Animal models like hepadnavirus-infected chimpanzees or the eastern woodchuck have been of great value for the characterization of HDV chronic infection. Recently, more practical animal models in which to perform a deeper study of host virus interactions and to evaluate new therapeutic strategies have been developed. Therefore, the main focus of this review is to discuss the current knowledge about HDV host interactions obtained from cell culture and animal models. Full article
(This article belongs to the Special Issue Animal Model to Study Viral Immunity)
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216 KiB  
Review
The Use of Lactic Acid Bacteria as a Probiotic in Swine Diets
by Fengjuan Yang, Chengli Hou, Xiangfang Zeng and Shiyan Qiao
Pathogens 2015, 4(1), 34-45; https://doi.org/10.3390/pathogens4010034 - 27 Jan 2015
Cited by 105 | Viewed by 12166
Abstract
As the resistance of pathogens to antibiotics and the possibility of antibiotic residues in animal products attract increasing attention, the interest in the use of alternatives to in-feed antibiotics has been growing. Recent research with Lactic acid bacteria (LAB) in pigs suggests that [...] Read more.
As the resistance of pathogens to antibiotics and the possibility of antibiotic residues in animal products attract increasing attention, the interest in the use of alternatives to in-feed antibiotics has been growing. Recent research with Lactic acid bacteria (LAB) in pigs suggests that LAB provide a potential alternative to antibiotic strategies. LAB include Lactobacillus species, Bifidobacterium spp, Bacillus spp, and some other microbes. LAB can adjust the intestinal environment, inhibit or kill pathogens in the gastrointestinal tract and improve the microbial balance in the intestine, as well as regulate intestinal mucosal immunity and maintain intestinal barrier function, thereby benefiting the health of pigs. The related mechanisms for these effects of LAB may include producing microbicidal substances with effects against gastrointestinal pathogens and other harmful microbes, competing with pathogens for binding sites on the intestinal epithelial cell surface and mucin as well as stimulating the immune system. In this review, the characteristics of LAB and their probiotic effects in newborn piglets, weaned piglets, growing pigs and sows are documented. Full article
(This article belongs to the Special Issue Alternatives to Antibiotics: Current Strategies and Future Prospects)
339 KiB  
Article
Aetiology of Acute Lower Respiratory Infections among Children Under Five Years in Accra, Ghana
by Theophilus K. Adiku, Richard H. Asmah, Onike Rodrigues, Bamenla Goka, Evangeline Obodai, Andrew A. Adjei, Eric S. Donkor and George Armah
Pathogens 2015, 4(1), 22-33; https://doi.org/10.3390/pathogens4010022 - 26 Jan 2015
Cited by 7 | Viewed by 6670
Abstract
The study aimed to investigate the aetiological agents and clinical presentations associated with acute lower respiratory infections (ALRI) among children under five years old at the Korle-Bu Teaching Hospital in Ghana. This was a cross-sectional study carried from February to December 2001. Nasopharyngeal [...] Read more.
The study aimed to investigate the aetiological agents and clinical presentations associated with acute lower respiratory infections (ALRI) among children under five years old at the Korle-Bu Teaching Hospital in Ghana. This was a cross-sectional study carried from February to December 2001. Nasopharyngeal aspirates and venous blood specimens obtained from 108 children with features suggestive of ALRI, were cultured and the isolated bacterial organisms were identified biochemically. Nasopharyngeal aspirates were also tested for Respiratory Syncitial Virus (RSV) antigen using a commercial kit (Becton Dickinson Directigen RSV test kit). A multiplex reverse transcription-PCR (RT-PCR) was also used to detect and characterize RSV using extracted RNA. Socio-demographic and clinical data were also obtained from the study subjects. Bronchopneumonia (55.5%), bronchiolitis (25%), lobar pneumonia (10.2), non-specific ALRI (4.6%), TB, bronchitis and respiratory distress (0.67%) were diagnosed. The prevalence of septicaemia was 10% and bacteria isolated were Staphylococcus aureus, Streptococcus pneumoniae and enteric bacteria, including Salmonella spp., Enterobacter spp and Klebsiella spp, were isolated. Out of the 108 cases, 18% tested positive for RSV, with two cases having RSV as the only aetiological pathogen detected. The subtyping analysis of RSV strains by a multiplex RT-PCR showed that subgroups A and B circulated in the season of analysis. Full article
(This article belongs to the Special Issue Respiratory Pathogens)
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125 KiB  
Editorial
Acknowledgement to Reviewers of Pathogens in 2014
by Pathogens Editorial Office
Pathogens 2015, 4(1), 20-21; https://doi.org/10.3390/pathogens4010020 - 08 Jan 2015
Viewed by 3348
Abstract
The editors of Pathogens would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2014:[...] Full article
247 KiB  
Review
Alternatives to Antibiotics in Animal Agriculture: An Ecoimmunological View
by Yongming Sang and Frank Blecha
Pathogens 2015, 4(1), 1-19; https://doi.org/10.3390/pathogens4010001 - 29 Dec 2014
Cited by 5 | Viewed by 7213
Abstract
Ecological immunology (or ecoimmunology) is a new discipline in animal health and immunology that extends immunologists’ views into a natural context where animals and humans have co-evolved. Antibiotic resistance and tolerance (ART) in bacteria are manifested in antibiosis-surviving subsets of resisters and persisters. [...] Read more.
Ecological immunology (or ecoimmunology) is a new discipline in animal health and immunology that extends immunologists’ views into a natural context where animals and humans have co-evolved. Antibiotic resistance and tolerance (ART) in bacteria are manifested in antibiosis-surviving subsets of resisters and persisters. ART has emerged though natural evolutionary consequences enriched by human nosocomial and agricultural practices, in particular, wide use of antibiotics that overwhelms other ecological and immunological interactions. Most previous reviews of antibiotic resistance focus on resisters but overlook persisters, although both are fundamental to bacteria survival through antibiosis. Here, we discuss resisters and persisters together to contrast the distinct ecological responses of persisters during antibiotic stress and propose different regimens to eradicate persisters. Our intention is not only to provide an ecoimmunological interpretation, but also to use an ecoimmunological system to categorize available alternatives and promote the discovery of prospective approaches to relieve ART problems within the general scope of improving animal health. Thus, we will categorize available alternatives to antibiotics and envision applications of ecoimmunological tenets to promote related studies in animal production. Full article
(This article belongs to the Special Issue Alternatives to Antibiotics: Current Strategies and Future Prospects)
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