Molecular characterization of clinical Streptococcus pneumoniae isolates with reduced susceptibility to fluoroquinolones emerging in Italy

Microbial Drug Resistance : MDR : Mechanisms, Epidemiology, and Disease
Maria Pia MontanariPietro Emanuele Varaldo

Abstract

Fifteen Streptococcus pneumoniae clinical isolates with reduced fluoroquinolone susceptibility (defined as a ciprofloxacin MIC of > or = 4 microg/ml), all collected in Italy in 2000-2003, were typed and subjected to extensive molecular characterization to define the contribution of drug target alterations and efflux mechanisms to their resistance. Serotyping and pulsed-field gel electrophoresis analysis indicated substantial genetic unrelatedness among the 15 isolates, suggesting that the new resistance traits arise in multiple indigenous strains rather than through clonal dissemination. Sequencing of the quinolone resistance-determining regions of gyrA, gyrB, parC, and parE demonstrated that point mutations producing single amino acid changes were more frequent in topoisomerase IV (parC mutations in 14 isolates and parE mutations in 13) than in DNA gyrase subunits (gyrA mutations in 7 isolates and no gyrB mutations observed). No isolate displayed a quinolone efflux system susceptible to carbonyl cyanide m-chlorophenylhydrazone; conversely, four-fold or greater MIC reductions in the presence of reserpine were observed in all 15 isolates with ethidium bromide, in 13 with ulifloxacin, in 9 with ciprofloxacin, in 5 with norfloxaci...Continue Reading

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Citations

Apr 28, 2005·Antimicrobial Agents and Chemotherapy·Ewa SadowyWaleria Hryniewicz
Jun 28, 2005·Antimicrobial Agents and Chemotherapy·Ralf René ReinertPeter Appelbaum
Nov 26, 2005·BMC Infectious Diseases·Andrea EndimianiAntonio Q Toniolo
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Aug 8, 2017·Microbial Drug Resistance : MDR : Mechanisms, Epidemiology, and Disease·Serena SimoniMarina Mingoia
May 26, 2005·The Journal of Antimicrobial Chemotherapy·Keith Poole
May 21, 2013·European Journal of Clinical Microbiology & Infectious Diseases : Official Publication of the European Society of Clinical Microbiology·D E KarageorgopoulosM E Falagas

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