The fresh blooms of the pharynx and trachea range between both ?- and you can ?-haemolytic streptococci as well as numerous anaerobes, staphylococci (and additionally Staph. aureus), Neisseria and you may diphtheroids. The respiratory system often is somewhat sterile, inspite of the typical consumption out of organisms from the respiration. not, good-sized numbers of medically regular individuals may hold the brand new fungus Pneumocystis jirovecii (in earlier times also known as P. carinii) within their lungs.

The stomach normally harbours only transient organisms, its acidic pH providing an effective barrier. However, the gastric mucosa may be colonized by acid-tolerant lactobacilli and streptococci. Helicobacter pylori, which can cause gastric ulcers (see Ch. twenty-two), is carried without symptoms by large numbers of people, the bacterium being in mucus and neutralizing the local acidic environment. The upper intestine is only lightly colonized (10 4 organisms/g), but populations increase markedly in the ileum, where streptococci, lactobacilli, enterobacteriaceae and Bacteroides may all be present. Bacterial numbers are very high (estimated at 10 11 /g) in the large bowel, and many species can be found (Fig. 8.2). The vast majority (95–99%) are anaerobes, Bacteroides being especially common and a major component of faecal material; E. coli is also carried by most individuals. Bacteroides and E. coli are among the species capable of causing severe disease when transferred into other sites in the body. Harmless protozoans can also occur in the intestine (e.g. Entamoeba coli) and these can be considered as part of the normal flora, despite being animals.

dos This new longitudinal distribution, frequency off thickness and you may densities of one’s bacterium getting back together the brand new normal flora of one’s people gastrointestinal tract. (more…)