Outbreak of multidrug-resistant Klebsiella pneumoniae carrying qnrB1 and bla CTX-M15 in a French intensive care unit
© Filippa et al.; licensee Springer. 2013
Received: 15 March 2013
Accepted: 4 June 2013
Published: 1 July 2013
The prevalence of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae is increasing globally and is a major clinical concern. Between June 2008 and September 2009, 4% of patients in an intensive care unit (ICU) were found to be colonized or infected by strains of Klebsiella pneumoniae multiresistant to ceftazidime, ciprofloxacin, and tobramycin; an investigation was initiated and isolates were characterized by molecular typing and resistance patterns.
Antibiotic susceptibilities were determined by Vitek2®, Etest®, and agar dilution. Gene encoding beta-lactamases and plasmid-mediated quinolone resistance PMQR determinants (qnr, aac(6′)-Ib) were characterized by PCR, sequencing, and transfer assays. DiversiLab® fingerprints were used to study the relatedness of isolates.
Fourteen isolates co-expressing blaCTX-M15, qnrB1, and aac(6′)-Ib-cr were identified. Genotypic analysis of these isolates identified 12 clonally related strains recovered from 10 patients. The increased prevalence of blaCTX-M15-qnrB1-aac(6′)-Ib-cr-producing K. pneumoniae coincided with the presence in the ICU of a patient originally from Nigeria. This patient was infected by a strain not clonally related to the others but harbouring qnrB1 and aac(6′)-Ib-cr genes, a finding not hitherto observed in France. We suspected transmission of resistance plasmids followed by rapid dissemination of the multiresistant K. pneumoniae clone by cross-transmission.
This study highlights the importance of microbiological screening for multidrug-resistant strains in ICUs, particularly among patients from regions in which multidrug-resistant bacteria are known to exist.
The increasing prevalence of infections caused by multidrug-resistant organisms is a cause for grave concern among healthcare professionals, in particular within intensive care units (ICU). The wide spread of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae is increasing globally and poses a major clinical problem in many countries . Plasmid-mediated quinolone resistance (PMQR), especially involving Qnr proteins and the aminoglycoside acetyltransferase variant determinant (AAC(6′)-Ib-cr), has emerged and is now described worldwide . PMQR determinants are generally reported in association with ESBL-producing enterobacteria, in particular the CTX-M type [2, 3]. Herein, we describe the investigation of an outbreak in a French ICU of a strain of Klebsiella pneumoniae producing QRN-B and CTX-M-15-type enzymes.
Between June 2008 and September 2009, the incidence of colonization or infection with K. pneumoniae strains multiresistant to ceftazidime (MIC > 4 mg/l), ciprofloxacin (MIC > 1 mg/L), and tobramycin (MIC > 4 mg/l) increased to 4% in the medical ICU of the Clinique Mutualiste, a 195-bed hospital centre equipped with 12 ICU beds (220 patients admitted annually). The medical files and microbiological data of patients colonized or infected with K. pneumoniae were reviewed. PCR amplification of blaCTX-M, aac(6′)-Ib, qnrA, qnrB, and qnrS sequences was performed as described by other authors [2, 4, 5]. All PCR products positive for aac(6′)-Ib were further analyzed by digestion with Bts CI (New England Biolabs, Ipswich, MA) to identify aac(6′)-Ib-cr, which lacks the Bts CI restriction site found in the wild-type gene . All other PCR products obtained were sequenced. Transferability of qnr and bla-CTX-M genes was studied by means of a conjugation assay using streptomycin-resistant E. coli J53 as the recipient. After 40 minutes of incubation, mating mixtures were plated onto agar containing streptomycin (100 mg/l) and ceftazidime (1 mg/l). The presence of qnr and bla CTX-M in the transconjugants was confirmed by PCR as described above. Clonal relationships also were investigated using the DiversiLab® fingerprinting system (bioMérieux), a commercially available repetitive-element (rep)-PCR tool successfully used for the typing of ESBL-producing E. coli isolates . This study was conducted only on bacterial samples without changing the medical care of patients. It does not therefore fall within the French law on biomedical research and has not received notice of an ethics committee.
Results and Discussion
In conclusion, we report an outbreak in a French ICU of a multiresistant K. pneumoniae strain possibly introduced from Africa. In France, very recent recommendations call for routine screening for multidrug-resistant bacteria in patients admitted to ICUs, particularly those repatriated from abroad (http://www.sf2h.net) (http://hcsp.fr). In practice, rectal swabbing or stool culture must be performed for such patients, with concomitant implementation of additional contact precautions to prevent cross-transmission. The results of our investigation clearly support the value of these new recommendations in preventing the diffusion of multiresistant strains among debilitated patients.
The authors thank Prof. P. Nordmann and Dr. L. Poirel for their gift of isolates of E. coli Lo positive for qnrA1, of K. pneumoniae B15 positive for qnrB1, of E. cloacae 287 positive for qnrS1, of E. coli DIT positive for aac(6′)-Ib-cr, and of E. coli BicA positive for qepA.
The authors are indebted to the following contributors at the Clinique Mutualiste: Monique Brun, infection control nurse, and Dr. Pascal Pain, head of the infection control committee.
This research has received funding support (No. 0808070) from the University Hospital of Saint Etienne.
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