Prevalence of the plasmid-mediated quinolone resistance determinants qnrA, qnrB and qnrS in Enterobacteriaceae isolates causing bacteraemia

Abstract number: 1733_531

Sanchez-Cespedes J., Marti S., Ruiz M., Soto S.M., Almela M., Marco F., Vila J.

Objectives: The main objective of this study was to investigate the prevalence of the qnrA, qnrB and qnrS genes in Enterobacteriaceae isolates causing bacteraemia.

Methods: Hundred and ninety-five Enterobacteriaceae isolates from blood samples were collected: 54 Klebsiella pneumoniae (27.7%), 28 Proteus mirabilis (14.4%), 25 Enterobacter cloacae (12.8%), 22 Serratia marcescens (11.3%), 21 Salmonella enteritidis (10.8%), 16 Klebsiella oxytoca (8.2%), 8 Salmonella typhimurium (4%), 6 Enterobacter aerogenes (3%), 5 Citrobacter freundii (2.6%), 4 Citrobacter koseri (2%), 3 Morganella morganii (1.5%), 2 Pantoea agglomerans (1%) and 1 Citrobacter werkmanii (0.5%). Screening of the qnrA, qnrB and qnrS genes was performed by multiplex PCR using a cocktail of specific primers. Bacterial strains positive for each qnr gene were used as positive controls, and were run in each batch of tested samples. Positive reactions were confirmed by direct sequencing of the PCR products. The sequences obtained were compared in the GenBank to determine the correspondent qnr variant. In order to characterise the genetic environment of these QNR determinants a PCR with an universal integron primer and a qnr multiplex primer was also performed.

Results: Five isolates (3%) carrying a qnr gene were found. Four of them corresponded to qnrB and the other one to qnrS; qnrA was not detected. The qnrS determinant corresponded to the variant qnrS2 and was found in K. pneumoniae 46408. Two variants of the qnrB gene were detected: qnrB2 in C. freundii 62778, C. freundii 21112 and 14.0 and qnrB6 in C. freundii 72857. The three isolates of C. freundii were not epidemiologically related by REP-PCR. Results of the PCR with the combination of integron and qnr primers showed that the qnrB2 determinant in the isolate C. werkmanii 14.0 was integrated in a qnr-containing complex sul1-type integron.

Conclusions: In our Hospital, the prevalence of the qnrB gene was higher than for the qnrA and qnrS determinants, differing to the situation in Spain where the qnrB determinant had not been detected until now. Also it is important to mention the high prevalence of the qnr gene in C. freundii (60% of the five studied isolates) and the presence of this gene in C. werkmanii given that this is the first time that the presence of a qnrB determinant has been reported in these species.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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