Primer relevamiento de marcadores de resistencia a antibióticos en Enterobacteriaceae en Cochabamba, Bolivia / First survey on antibiotic resistance markers in Enterobacteriaceae in Cochabamba, Bolivia

A molecular survey was conducted in Cochabamba, Bolivia, to characterize the mechanism involved in the resistance to clinically relevant antibiotics. Extended Spectrum β-lactamase encoding genes and plasmid-mediated quinolone resistance (PMQR) markers were investigated in a total of 101 oxyimino-cephalosporin-resistant enterobacteria recovered from different health centers during four months (2012-2013). CTX-M enzymes were detected in all isolates, being the CTX-M-1 group the most prevalent (88.1%). The presence of blaOXA-1 was detected in 76.4% of these isolates. A high quinolone resistance rate was observed among the included isolates. The aac(6′)-Ib-cr gene was the most frequent PMQR identified (83.0%). Furthermore, 6 isolates harbored the qnrB gene. Interestingly, qepA1 (6) and oqxAB (1), were detected in 7 Escherichia coli, being the latter the first to be reported in Bolivia. This study constitutes the first molecular survey on resistance markers in clinical enterobacterial isolates in Cochabamba, Bolivia, contributing to the regional knowledge of the epidemiological situation. The molecular epidemiology observed herein resembles the scene reported in South America.

Se llevó a cabo un relevamiento molecular de la resistencia a antibióticos de importancia clínica en aislamientos recuperados en Cochabamba, Bolivia. Se estudiaron los genes codificantes de β-lactamasas de espectro extendido y de resistencia a quinolonas de localización plasmídica (PMQR) en un total de 101 aislamientos de enterobacterias resistentes a oximinocefalosporinas recuperados en distintos centros de salud, durante 4 meses (2012-2013). En todos ellos se detectó la presencia de cefotaximasas, las CTX-M grupo 1 fueron las más prevalentes (88,1%). La presencia de blaOXA-1 se detectó en el 76,4% de estos aislamientos. Se observó una elevada proporción de aislamientos resistentes a quinolonas. El gen aac(6′)-Ib-cr fue el determinante PMQR más frecuentemente identificado (83%). Además, 6 aislamientos resultaron ser portadores de qnrB. Por otro lado, cabe remarcar que 7 Escherichia coli presentaron qepA1 (6) y oqxAB (1); se documenta así por primera vez la presencia de oqxAB en Bolivia. Este estudio constituye el primer relevamiento de marcadores de resistencia en aislamientos clínicos de enterobacterias en Cochabamba, Bolivia; de este modo se contribuye al conocimiento regional de la situación epidemiológica, la cual presenta un escenario similar al observado en el resto de Latinoamérica.

Prevalence and transmission of oqxAB gene in clinical strains of Escherichia coli and Klebsiella pneumoniae / 中国感染与化疗杂志

Objective To investigate the prevalence and the transmission of oqxAB gene in clinical strains of Escherichia coli and Klebsiella pneumoniae .Methods Nonduplicate clinical isolates of E.coli (n=72)and K .pneumoniae (n=49)were col-lected.The oqxAB gene was amplified by PCR.The product was sequenced.Plasmid conjugation experiments were done in oqxAB-positive E.coli and K.pneumoniae strains to detemine whether oqxAB gene is located in plasmid.The MICs and mu-tant prevention concentrations (MPCs)for ciprofloxacin were determined in transconjugants with oqxAB gene by agar dilution method.Results The oqxA,oqxB and oqxAB were identified in 15,4,and 7 of the 72 strains of Escherichia coli and 4,1,and 34 of the 49 strains of K.pneumoniae,respectively.The oqxAB gene was positive in 2 (2/16)ciprofloxacin sensitive and 5 (5/56)ciprofloxacin resistant E.coli strains,in 8 (8/14)ciprofloxacin sensitive and 26 (26/35)ciprofloxacin resistant K. pneumoniae strains,respectively.The E.coli and K.pneumoniae strains with or without oqxAB did not show different sus-ceptibility to ciprofloxacin.The oqxA and oqxB sequences from E.coli and K.pneumoniae showed 99% similarity to the se-quences of GeneBank accession number AB601773.1 and accession number FJ975561.1,respectively.The oqxAB gene was successfully transferred in 4 of the 5 oqxAB-positive E.coli strains.The MIC of ciprofloxacin was 0.25-0.5 mg/L against the transconjugants,31-62 times higher than the MICs for the recipient strains.The MPC of ciprofloxacin was 8-16 mg/L against the transconjugants,32 times higher than that for recipient strain J53.The oqxAB gene were not transferred in K. pneumoniae. When the MIC of ciprofloxacin was ≤0.062 5 mg/L,the MPC of ciprofloxacin was 0.25-0.5 mg/L for K.pneumoniae strains with or without oqxAB.When MIC was 0.25-0.5 mg/L,the MPC of ciprofloxacin was 2-16 mg/L for K .pneumoniae strains with or without oqxAB .Conclusions oqxAB gene is present in E .coli and K .pneumoni-ae .The oqxAB gene spreads through plasmid in E .coli.The nonsiginificant difference of oqxAB prevalence between ciproflox-acin sensitive and ciprofloxacin resistant strains indicates that oqxAB gene may mediate low level resistance to ciprofloxacin in E.coli.The E.coli transconjugants of oqxAB gene can produce high level resistance under the selection pressure of ciproflox-acin.The high level resistance in K .pneumoniae under selection pressure of ciprofloxacin is not associated with oqxAB gene, but related to the ciprofloxacin MIC against these strains.