Normal flora of the mouth and nasopharynx and upper respiratory tract The upper respiratory tract is heavily colonized by normal flora but the lower respiratory tract is sterile.
Mouth . Viridans streptococci . Non-pathogenic Neisseria spp. . Diphtheroids .Anaerobes like Capnophaga spp. . Commensal Neisseria . Spirochetes . Actinimyces Prevotella
Nasopharynx and upper respiratory tract . Staphylococcus epidermidis . Diphtheroids . Alph-hemolytic streptococci . Commensal Neisseria . Pneumococci . Haemophilus spp.
Normal flora of the gastrointestinal tract The normal flora of the stomach, duodenum, jejunum and upper ileum is scanty but the large intestine is very heavily colonized with bacteria.