Impact of Fluoroquinolone Resistance Mutations on Gonococcal Fitness and In Vivo Selection for Compensatory Mutations

Abstract

Background. Quinolone-resistant Neisseria gonorrhoeae (QRNG) arise from mutations in gyrA (intermediate resistance) or gyrA and parC (resistance). Here we tested the consequence of commonly isolated gyrA 91/95 and parC 86 mutations on gonococcal fitness.Methods. Mutant gyrA 91/95 and parC 86 alleles were introduced into wild-type gonococci or an isogenic mutant that is resistant to macrolides due to an mtrR −79 mutation. Wild-type and mutant bacteria were compared for growth in vitro and in competitive murine infection.Results. In vitro growth was reduced with increasing numbers of mutations. Interestingly, the gyrA 91/95 mutation conferred an in vivo fitness benefit to wild-type and mtrR −79 mutant gonococci. The gyrA 91/95 , parC 86 mutant, in contrast, showed a slight fitness defect in vivo, and the gyrA 91/95 , parC 86 , mtrR −79 mutant was markedly less fit relative to the parent strains. A ciprofloxacin-resistant (Cip R ) mutant was selected during infection with the gyrA 91/95 , parC 86 , mtrR −79 mutant in which the mtrR −79 mutation was repaired and the gyrA 91 mutation was altered. This in vivo-selected mutant grew as well as the wild-type strain in vitro.Conclusions. gyrA 91/95 mutations may contribute to the spread of QRNG. Further acquisition of a parC 86 mutation abrogates this fitness advantage; however, compensatory mutations can occur that restore in vivo fitness and maintain Cip R .Neisseria gonorrhoeae is a Gram-negative diplococcus that plays a major role in urogenital tract and perinatal infections [1]. Gonorrhea is the second most frequently reported bacterial sexually transmitted infection (STI) in the United States, with an estimated 700 000 new cases each year. The rate of gonorrhea is

Identification of Amino Acids Conferring High-Level Resistance to Expanded-Spectrum Cephalosporins in the penA Gene from Neisseria gonorrhoeae Strain H041

“…However, H041 and similar strains might also contain compensatory mutations that mitigate the fitness cost, which are frequently obtained in the laboratory (35,36) and are likely occur in nature as well. Studies to address these questions are currently in progress.…”

Origin and Proliferation of Multiple-Drug Resistance in Bacterial Pathogens

“…As an example, the fitness costs of resistance mutations in the genetic background of Beijing lineage M. tuberculosis are smaller than those in other genetic backgrounds, or compensatory mutations are in easier reach for them, possibly explaining the association between Beijing TB genotype and MDR (100). In a mouse model of gonococcal infection, the fitness cost of fluoroquinolone resistance mutations depends on genetic background (101).…”

Molecular Background of Fluoroquinolone Resistance in Pathogenic Human Mycoplasmas

“…Мутации в генах gyrA и parC в участках, соответствую-щих сайтам связывания фторхинолонов в ами-нокислотной последовательности, не влияют на жизнеспособность кишечной палочки [54]. С другой стороны, мутации в тех же локусах приводят к замедлению роста N. gonorrhoeae [43], S. typhimurium (в данном случае одновре-менно снижается штамма) и P. aeruginosa [54].…”

“…Возможно, что снижение жизнеспособности и скорости роста, связанные с возникновени-ем мутаций в генах гиразы и топоизомеразы IV, компенсируется за счет изменений за пре-делами геномных локусов, связанных с раз-витием устойчивости к фторхинолонам [43], поскольку и для E. coli и P. aeruginosa показано снижение активности гиразы после возник-новения мутаций, приводящих к резистент-ности [54].…”

“…Для возникновения устойчивых вариантов E. coli, Campylobacter jejuni, Salmonella spp. и N. gonorrhoeae необходимо накопление нескольких мутаций [16,43,50]. Паттерн на-копления мутаций отражает особенности воз-действия фторхинолонов на микроорганизм конкретного вида.…”