Antimicrobial susceptibility of anaerobic bacteria from the intestinal microflora of healthy children and antimicrobial-treated children in Nicaragua.

The objective of this study was to determine the antimicrobial susceptibility of anaerobic bacteria from the intestinal microflora of healthy children who had not been treated with antimicrobial agents since birth or at 1, 3, 6, 12, 18 and 24 months of age, as well as from children of the same ages treated with the most commonly used antimicrobial agents in Nicaragua. A total of 947 Bacteroides and 745 Clostridium strains were isolated from 67 healthy and 94 antimicrobial-treated children. The minimal inhibitory concentrations of ampicillin, cefoxitin, imipenem, clindamycin, metronidazole and chloramphenicol were determined by the agar dilution method. Detection of ss-lactamase was made by the nitrocefin assay. No bacterial strains resistant to imipenem, clindamycin, metronidazole or chloramphenicol were found. The susceptibility of Bacteroides species to ampicillin and cefoxitin isolated from antimicrobial-treated children decreased progressively as the children reached 24 months of age, from 88% to 78% and from 94% to 81%, respectively. All the Bacteroides strains isolated from the healthy children were 100% susceptible to cefoxitin when they were <=12 months and 92% susceptible after this age; the susceptibility of Bacteroides strains to ampicillin in these children was from 91% at 1 month to 86% at 24 months of age. All Clostridium strains were susceptible to ampicillin and cefoxitin. The ss-lactamase production was seen only in Bacteroides species. These data indicate that a rational use of antimicrobial agents is needed to avoid the development of resistance in anaerobic bacteria.