International Congress of the Society for Microbial Ecology and Disease SOMED 2013, September 2013

摘要

Introduction: In this study, a total of 3694 Gram-negative bacteria,mainly isolated from the feces and saliva, were gathered over 1 yearto determine the effect of four different antibiotic treatments(minocycline, amoxicillin, ciprofloxacin, clindamycin) on the compo-sition of antibiotic resistance genes present in these bacteria inhuman volunteers. Methods: An expanded Gram-negative microarraywas used for detecting antibiotic resistance genes in aerobic andanaerobic Gram-negative bacteria isolated from a range of samplesfrom different treatment and placebo groups. The largest proportionof isolates received from all treatment and placebo groups werefrom feces and were Escherichia coli. Results: Using our microarray,the diversity of resistance genes in aerobic bacteria was muchgreater for aerobic bacteria than for anaerobic bacteria irrespectiveof treatment; up to 50 different genes were detected in aerobicisolates and only up to eight different resistance genes in anaerobes.Also, E. coli generally harbored a much greater number of resistancesthan non-E. coli isolates, with the maximum number being 15. Thearray results also indicated that certain resistance genes were muchmore prevalent than others, with bla TEM being the most prevalentacross all groups, irrespective of treatment. This suggests wide-spread circulation of mobile genetic elements carrying this resistancegene. Anaerobic bacteria were unlikely to harbor resistance genescommon in aerobes, although sul2 was also detected in a smallnumber of anaerobic bacteria. The data showed that the percentageof isolates harboring resistances to three or more classes of antibioticwere similar for all treatment groups including the placebos, atapproximately 36%. Further analysis indicated that in the amoxicillintreatment groups, the percentage of multi-resistant isolates in-creased at day 11 post-treatment. We also noted a dramatic decreasein the percentage of isolates with no resistance genes in theciprofloxacin and clindamycin groups following treatment, indicatinga possible effect of antibiotic treatment on the resident microbiota.In some participants, conserved resistance gene sets were identifiedacross multiple time-points for all treatment groups, includingplacebo. For selected examples, pulse field gel electrophoresis(PFGE) was performed and showed that isolates with the sameresistance genes generally had identical PFGE profiles, even whencollected from visits that were months apart. Discussion: Theseresults indicate multi-drug resistant E. coli to be currently moreprevalent in the individuals studied than other Gram-negative aero-bic bacteria. We also noted the persistence of some isolates harbor-ing resistance genes to multiple antibiotic classes, which wasmaintained in the absence of any antibiotic treatment. We did notdetect any long-term changes to the overall antibiotic resistancegene composition from cultivable Gram-negative bacteria as aconsequence of treatment with these antibiotics.