Commensal bacteria

The optimum temperature varies widely from species to species but in general the common moulds will grow better at 22-25 °C than most human pathogenic and commensal bacteria. It is customary, therefore, to incubate mould cultures at lower temperatures than bacterial cultures. 

Lactic acid in the vagina gives it an acidic pH (5.0) which together with other products of metabohsm inhibits colonization by most bacteria, except some lactobacilli, which constitute the commensal flora. Other types of baeteria are unable to establish themselves in the vagina unless they have become extremely specialized. These species of microorganism tend to be associated with venereal infeetions. 

Macpherson A.J., Geuking M.B. and McCoy K.D. (2005). Immune responses that adapt the intestinal mucosa to commensal intestinal bacteria . Immunology, 115, 153-163. 

Although the mucus layer acts as a barrier to some invading pathogens, it also supports the growth and maintenance of a number of commensal bacteria in the GIT. It acts as an initial binding site, a source of nutrients for growth, and is a niche where these bacteria can replicate and potentially compete with other newly introduced bacteria (Laux et ah, 2005). Therefore, tissues that produce mucus have the potential to provide the host... 

Municipal waste water treatment plants receive daily considerable amounts of non-metabolized antibiotics and metabolites thereof, as well as other environmental pollutants. Moreover, domestic waste water is a complex mixture of human commensal and environmental bacteria, which get in contact with considerable amounts of antimicrobial agents and other substances with unknown effects on bacterial metabolism and microbial communities [38,54-57]. The free movement of bacteria between different environmental niches and the easiness with which bacteria become adapted to new conditions contribute to a rapid dissemination of antibiotic... 

Environmental bacteria Human/Animal commensal bacteria... 

Over the last years, a renewed interest on the antibiotic resistance phenotypes in municipal waste water treatment plants became apparent in the scientific literature. The underlying hypothesis of these smdies is that urban sewage treatment plants are potential reservoirs of antibiotic resistance, and, in general, it is aimed at contributing to assess the risks of dissemination, posed by the treated effluents discharged into natural water courses. As a general trend, these studies focus on human/animal commensal and environmental bacteria, frequently disseminated via faecal contamination, and which can survive in waters. The relevance of these bacteria, which may exhibit clinically relevant resistance phenotypes, as possible nosocomial agents seems also to be a motivation behind these smdies. 

Table 2 Examples of studies on antibiotic resistance patterns in human commensal and environmental bacteria in urban waste water treatment plants. Unless otherwise stated,... 

Thaller MC, Migliore L, Marquez C et al (2010) Tracking acquired antibiotic resistance in commensal bacteria of Galapagos land iguanas no man, no resistance. PLoS One 5(2) e8989... 

Sharma R, Munns K, Alexander T et al (2008) Diversity and distribution of commensal fecal Escherichia coli bacteria in beef cattle administered selected subtherapeutic antimicrobials in a feedlot setting. Appl Environ Microbiol 74(20) 6178-6186... 

Commensal bacteria, capable of colonizing mucosal surfaces, which are genetically engineered to express viral, bacterial, or eukaryotic antigens to produce an immune response... 

A range of different vaccine vectors has been developed over time to provoke an immune response within the body [127,142], However, it has only been comparatively recently that they have been applied to inducing mucosal immunity within the uterovaginal tract. The general vector platforms that have been used include attenuated viruses, live viruses, commensal bacteria, DNA vectors, and protein subunit/peptide or virus-like particles (Table 21.9). The choice of vector is dependent on a number of factors such as the pathogenic virus and bacterial type and the length of duration of immunity required. 

Medaglini, D., et al. 1997. Commensal bacteria as vectors for mucosal vaccines against sexually transmitted diseases Vaginal colonization with recombinant streptococci induces local and systemic antibodies in mice. Vaccine 15 1330. 

Bratbak, G., and T. F. Thingstad. 1985. Phytoplankton-bacteria interactions An apparent paradox Analysis of a model system with both competition and commensalism. Marine Ecology Progress Series 25 23-30. 

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