Plasmid Mediated Quinolone Resistance Mechanisms (PMQRs) in Clinical Enterobacteria from Argentina: A View from the Microbiological Practice

PATRICIA ANDRES; ALFONSO SOLER BISTUE; LEONOR GUERREIRO; CELESTE LUCERO

Conferencia; 49th ICAAC; 2009

American Society for Microbiology

PMQRs were already reported worldwide. To date, only qnrB andaac(6´)-Ib-cr were found in Argentina.Aim: to analyze the occurrence and distribution of PMQRs inenterobacteria with decreased quinolone susceptibility (DQS).Methods: 84 enterobacteria [38 Klebsiella spp. (KL); 20 Escherichia coli(EC); 12 Salmonella spp. (SA); 10 Enterobacter spp. (EN); other genera(4)] with DQS [nalidixic acid > 6 mm and ciprofloxacin (CIP) < 29 mm; CLSIdisk diffusion method (DD)] were found during routine microbiological tasksat 26 hospitals [Buenos Aires (BA) and 10 Provinces, 2005 - 2008] andsent to INEI for characterization. Presence of qnr (A, B and S) was testedby standard PCR; aac(6´)-Ib was firstly screened in all isolates by notsusceptibility to kanamycin (DD inhibition zones ≤ 17 mm) and thenaac(6´)-Ib and aac(6´)-Ib-cr were differentiated in selected isolates by 2selective PCRs (results were validated by DNA sequencing).Results: 54/84 isolates (64%; 21 hospitals in BA and 9 Provinces; 2005 -2008) had at least one PMQR (qnrB, qnrS and aac(6´)-Ib-cr, 46, 5 and 21isolates, respectively); 33 isolates showed qnr (B or S) and 3 had aac(6´)-Ib-cr, as the unique PMQR while 18 isolates showed both mechanisms.The occurrence of PMQRs was high among the 4 major species (%): KL(58); EC (65); SA (100); EN (70). The proportion (%) of aac(6´)-Ib-cr wassignificantly higher in KL (39) and EN (50) than in EC (5) and SA (0) (P ≤0.010, Fisher´s test) but there were not significant differences for qnr. Of 56isolates with CIP susceptibility by CLSI breakpoint (≥ 21 mm), 30 (54%)had PMQRs: qnrB alone, 27 isolates (mostly EC and SA, 12 isolates each);aac(6´)-Ib-cr alone, 2 KL, and both mechanisms, 1 EN.Conclusions: This is the first report on qnrS in Argentina where PMQRs arewidely spread. In this work, CLSI CIP breakpoint could not detect morethan 50% of PMQR producing isolates.