Prevalence of enteric bacteria that inhibit growth of enterohaemorrhagic Escherichia coli O157 in humans

• Published in: Epidemiology and infection Vol. 135; no. 1; pp. 110 - 117
• Main Authors: TOSHIMA, H., HACHIO, M., IKEMOTO, Y., OGASAWARA, J., HASE, A., TAKAHASHI, K., MASAKI, H., NISHIKAWA, Y.
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.01.2007
• Subjects: Adult; Adults; Aging - physiology; Antibiosis; Antibodies; Bacteria; Bacteriocins; Bacteriology; Biological and medical sciences; Child; Child, Preschool; Children; Colicins - biosynthesis; Colicins - classification; Colicins - genetics; Colicins - pharmacology; E coli; Escherichia coli; Escherichia coli - classification; Escherichia coli - growth & development; Escherichia coli - isolation & purification; Escherichia coli - metabolism; Escherichia coli O157 - drug effects; Escherichia coli O157 - growth & development; Feces - microbiology; Flora; Fundamental and applied biological sciences. Psychology; Health care; Humans; Immunology; Infant; Infant, Newborn; Infections; Inflammatory bowel disease; Intestines - microbiology; Investigations; Klebsiella oxytoca - classification; Klebsiella oxytoca - growth & development; Klebsiella oxytoca - isolation & purification; Klebsiella oxytoca - metabolism; Life sciences; Microbiology; Middle Aged; Miscellaneous; Older adults; Older people; Polymerase Chain Reaction; Prevalence; United Kingdom > UK; Japan; Human; Prevalence; Microbiology; Escherichia coli; Bacteria; Epidemiology; Enterobacteriaceae
• ISSN: 0950-2688; 1469-4409
• DOI: 10.1017/S0950268806006510

Enterohaemorrhagic Escherichia coli O157 (O157) is infectious to humans, particularly children, at very low doses and causes not only haemorrhagic colitis but also other serious symptoms. To investigate an association between intestinal bacterial flora and resistance to such infections, we screened faecal samples for the presence of enteric bacteria that are able to suppress the growth of O157. Samples from 303 individuals, 35 children (aged [les ]6 years) and 268 adults (aged 20–59 years), were examined. Colonies with different appearances on sorbitol MacConkey agar medium were screened for the production of bacteriocins inhibitory for O157 in an overlay agar plate assay. O157-inhibiting strains were isolated from 52 individuals. The prevalence of these bacteria tended to rise with age, and was significantly higher among 40- to 59-year-old adults (23/101, 22·8%) than among children (3/35, 8·6%; P<0·05). To test the hypothesis that these bacteriocin-producing strains contribute to resistance against O157 in human adults, we examined faecal samples of 25 healthy O157 carriers. Inhibitory bacteria were more prevalent among the latter (9/25, 36·0%) than among age-matched subjects who did not carry O157 (49/268, 18·3%). It appears, therefore, that inhibitory bacteria in the human gut may play a role in inhibiting propagation of O157 and/or suppressing expression of virulence factors by this pathogen.