The effectiveness of different culture media in the isolation of enteric microörganisms

Abstract

An investigation was carried out concerning the usefulness of various culture media in the isolation of enteric pathogens from feces of children and infants with diarrheal disease. The following results were obtained: (1) Among 500 consecutive stool specimens 324 contaned organisms other than B. coli, B. aerogeiies. and intermediates. The following species were encountered: B. typhosus, B. paradysenteriae (Flexner), B. schmitzii, B. castelanii, B. paratyphi B, B. typhi muriurn, B. thompson, B. proteus, B. norgami type I, paracolon bacilli, B. pyocyaneus, B. alcaligenes, and B. coli anaerogenes. (2) Among the culture media used Shigella-Salmonella and desoxycholate-citrate agar proved to he superior to enriching fluid, and enriching fitud superior to Endo and MacConkey agar in the isolation of thec organisms. (3) B. morganii and paracolon bacilli were present in 207 out of 500 specimens. (4) Twenty-six specimens, aside from B. coli, B. aerogenes, and intermediates, contained more than one species of aerobic, non-spore-bearing, gram-negative bacilli. (5) In the presence of B. proteus these organisms are more readily recovered from SS and DC agar than from Endo and MacConkey agar. (6) Isolation of any of these organisms from only one out of five culture media was accomplished in seventy-three instances. Enriching fluid proved to be more valuable than SS and DC agar and these latter better than MacConkey and Endo agar in these cases. (7) It is concluded that no single culture medium allows for the optimal isolation of these organisms and that the simultaneous use of several culture media yields the best results.