Assessment of prevalence and changing epidemiology of extended-spectrum beta-lactamase-producing Enterobacteriaceae fecal carriers using a chromogenic medium.

Five hundred fecal samples from 462 patients (68.4% ambulatory) (February-April, 2007) from Madrid (Spain) were screened for extended-spectrum beta-lactamase (ESBL) producers using ceftazidime and cefotaxime (1 mg/L) MacConkey (MAC) agar plates and a chromogenic media (chromID ESBL; bioMérieux, Marcy-l'Etoile, France). bla(ESBL), qnr, aac(6')Ib-cr, and 16S rRNA methylase genes were assessed. A prevalence of 8.2% of ESBL fecal carriers was observed (8.9% hospitalized, 7.9% nonhospitalized patients), higher than that previously observed (1991, 0.6%; 2003, 7.0%). Sensitivity, specificity, and positive and negative predicted values were 100%, 94.8%, 63%, and 100% for chromID ESBL and 87.8%, 89.8%, 43.4%, and 98.9% for MAC, respectively. ESBL distribution was as follows: CTX-M-9-group, 40% (mainly CTX-M-14); CTX-M-1-group, 26.6% (mainly CTX-M-15); SHV-type, 29% (mainly SHV-12); and TEM-type, 4.4%. These enzymes were found in pulsed-field gel electrophoresis nonclonally related Escherichia coli and Klebsiella pneumoniae isolates. Transferable quinolone resistance was confirmed in CTX-M-9 (qnrS1), CTX-M-15 [aac(6')Ib-cr, qnrS1], and SHV-12 (qnrB7, qnrS1) producers but not 16S rRNA methylase genes. The chromID ESBL medium was reliable to screen ESBL fecal carriers with a general decrease in the laboratory workload. Time-to-time monitoring of ESBL fecal carriers is useful to ascertain current trend of ESBL epidemiology.

Paniagua R ，Valverde A ，Coque TM ，Baquero F ，Cantón R ... -  《-》

Molecular characteristics of extended-spectrum β-lactamases in clinical isolates of Enterobacteriaceae from the Philippines.

β-Lactamases, including extended-spectrum β-lactamases (ESBLs) and AmpC β-lactamases, are major resistance mechanisms of Enterobacteriaceae. Emergence of plasmid-mediated quinolone resistance (PMQR) determinants in ESBL-producing isolates poses a global threat. The molecular characterisitcs of ESBL and PMQR determinants in the Philippines are not well characterized. In this study, we investigated ESBLs and AmpC β-lactamases in clinical isolates of Enterobacteriaceae from the Philippines, and analyzed the association between ESBL and PMQR genes. A total of 91 amoxicilin non-susceptible Enterobacteriaceae were collected at the Research Institute for Tropical Medicine of the Philippines from 2006 to 2008. AmpC- or ESBL-producing isolates were screened by detecting a zone diameter for cefoxitin ≤ 14 mm or cefpodoxime ≤ 20 mm, respectively. Possible ESBL-producing strains were assessed by the ESBL confirmation test of the Clinical and Laboratory Standards Institute. PCR and sequencing were performed to detect the ESBL and PMQR genes. The number of ESBL-producers and AmpC-producers confirmed phenotypically was 17 (18.7%) and 61 (67.0%), respectively. Of 17 phenotypic ESBL-producers, 14 isolates had ESBL genes, including 6 of Escherichia coli, 3 of Enterobacter cloacae, 2 of Enterobacter aerogenes, 2 of Klebsiella pneumoniae, and 1 of Klebsiella ozaenae. Among these isolates, there were 13, 4, and 12 with bla(CTX-M), bla(SHV), and bla(TEM), respectively. Of the bla(CTX-M)-positive isolates, bla(CTX-M-15) shows the highest prevalence, followed by bla(CTX-M-3) and bla(CTX-M-14). Of 14 ESBL-producers identified by PCR, 4, 6, and 7 isolates were positive for qnrB, qnrS, and aac(6')-Ib-cr, respectively. The frequency of aac(6')-Ib-cr positivity was significantly higher among CTX-M-15-producing isolates. Thus, we identified bla(CTX-M), aac(6')-Ib-cr, and qnr in ESBL-producing Enterobacteriaceae from the Philippines, and revealed a significant association between bla(CTX-M-15) and aac(6')-Ib-cr. Local epidemiological data are important for implementing appropriate antimicrobial therapy and effective infection control measures. Continuous monitoring of antimicrobial resistance genes in the Philippines will be required.

Kanamori H ，Navarro RB ，Yano H ，Sombrero LT ，Capeding MR ，Lupisan SP ，Olveda RM ，Arai K ，Kunishima H ，Hirakata Y ，Kaku M ... -  《-》

Prevalence of plasmid-mediated quinolone resistance determinants in ESBL Enterobacteriaceae clinical isolates over a 1-year period in a French hospital.

The prevalence of plasmid-mediated quinolone resistance (PMQR) determinants (qnrA, qnrB, qnrS, aac(6')-Ib-cr, and qepA) was investigated in a collection of 47 extended-spectrum β-lactamase (ESBL) producing enterobacterial isolates with reduced susceptibility to fluoroquinolones, recovered at Nantes University hospital, in 2006. qnr, aac(6')-Ib-cr, and qepA genes were screened by PCR, and positive results were subsequently confirmed by sequencing. The epidemiological relationship between positive isolates was studied by pulsed-field gel electrophoresis (PFGE). qnr-positive isolates were analyzed for antimicrobial susceptibility and presence of mutations in the quinolone resistance-determining region (QRDR) of gyrA and parC genes. ESBL genes were characterized by PCR and sequencing. Conjugation experiments were performed to determine whether the qnr-carrying plasmids were self-transferable. Two Klebsiella pneumoniae isolates (4.3%), not clonally related, harboured a qnrS1 gene, whereas no qnrA- or qnrB-positive isolate was detected. The aac(6')-Ib-cr gene was detected in 11 Escherichia coli and one K. pneumoniae isolates. None of the 47 isolates carried the qepA gene. ESBLs associated with QnrS1 were CTX-M-14 and CTX-M-15. The CTX-M-15 producing isolate was highly resistant to fluoroquinolones and harboured three mutations in the QRDR and two PMQR determinants (qnrS1 and aac(6')-Ib-cr). The CTX-M-14-producing isolate exhibited reduced susceptibility or resistance to fluoroquinolones without resistance to nalidixic acid. This strain harboured only a qnr gene on a single 170 kb transferable plasmid, without any mutation in the QRDR. In conclusion, our study showed that aac(6')-Ib-cr gene had occurred in multiclonal ESBL-producing enterobacterial isolates collected at Nantes University hospital in 2006, with a higher prevalence than qnr genes.

Crémet L ，Caroff N ，Dauvergne S ，Reynaud A ，Lepelletier D ，Corvec S ... -  《-》

Surveillance of extended-spectrum beta-lactamases from clinical samples and faecal carriers in Barcelona, Spain.

Miró E ，Mirelis B ，Navarro F ，Rivera A ，Mesa RJ ，Roig MC ，Gómez L ，Coll P ... -  《JOURNAL OF ANTIMICROBIAL CHEMOTHERAPY》

Evaluation of CHROMagar CTX, a novel medium for isolating CTX-M-ESBL-positive Enterobacteriaceae while inhibiting AmpC-producing strains.

Randall LP ，Kirchner M ，Teale CJ ，Coldham NG ，Liebana E ，Clifton-Hadley F ... -  《-》