Indirect resistance to several classes of antibiotics in cocultures with resistant bacteria expressing antibiotic-modifying or -degrading enzymes
2016 (English)In: Journal of Antimicrobial Chemotherapy, ISSN 0305-7453, E-ISSN 1460-2091, Vol. 71, no 1, 100-110 p.Article in journal (Refereed) PublishedText
Objectives: The detection of indirect resistance in vitro suggests that coinfecting bacteria from the normal microbial flora may have a more important negative impact during antimicrobial therapy than is generally appreciated.Indirect resistance (IR), the ability of an antibiotic-resistant population of bacteria to protect a susceptible population, has been previously observed for beta-lactamase-producing bacteria and associated with antimicrobial treatment failures. Here, we determined whether other resistance determinants could cause IR in the presence of five other classes of antibiotics. Methods: A test was designed to detect IR and 14 antibiotic resistance genes were tested in the presence of 13 antibiotics from six classes. A bioassay was used to measure the ability of resistance-causing enzymes to decrease the concentration of active antibiotics in the medium. Results: We confirmed IR in the presence of beta-lactam antibiotics (ampicillin and mecillinam) when TEM-1A was expressed. We found that bacteria expressing antibiotic-modifying or -degrading enzymes Ere(A), Tet(X2) or CatA1 caused IR in the presence of macrolides (erythromycin and clarithromycin), tetracyclines (tetracycline and tigecycline) and chloramphenicol, respectively. IR was not observed with resistance determinants that did not modify or destroy antibiotics or with enzymes modifying aminoglycosides or degrading fosfomycin. IR was dependent on the resistance enzymes decreasing the concentration of active antibiotics in the medium, hence allowing nearby susceptible bacteria to resume growth once the antibiotic concentration fell below their MIC. Conclusions: IR was not limited to beta-lactamase-producing bacteria, but was also caused by resistant bacteria carrying cytoplasmic antibiotic-modifying or -degrading enzymes that catalyse energy-consuming reactions requiring complex cellular cofactors. Our results suggest that IR is common and further emphasizes that coinfecting agents and the human microflora can have a negative impact during antimicrobial therapy.
Place, publisher, year, edition, pages
2016. Vol. 71, no 1, 100-110 p.
IdentifiersURN: urn:nbn:se:uu:diva-282653DOI: 10.1093/jac/dkv312ISI: 000371238100017OAI: oai:DiVA.org:uu-282653DiVA: diva2:917442
FunderSwedish Research Council