Plasmid-mediated quinolone resistance in non-typhi serotypes of Salmonella enterica in Ireland in 2001–May 2006

Abstract number: 1732_242

O'Connor J., Morris D., DeLappe N., Doran G., Cormican M.

Objectives: To screen non-typhoid Salmonella enterica isolates for plasmid encoded quinolone resistance determinant qnrA, qnrB and qnrS.

Methods: All 5340 isolates of non-typhoid Salmonella enterica received from humans and animals between 2001 and May 2006 were included. Susceptibility to nalidixic acid and ciprofloxacin was performed in accordance with the disk diffusion methods of the Clinical Laboratory Standards Institute. Ciprofloxacin MICs were determined by Etest for all nalidixic acid resistant isolates, and isolates with an MIC of >0.25 ug/mL were screened for the presence of qnrA, qnrB and qnrS by PCR using specific primers previously described. A positive control for qnrA was included and all samples were confirmed as amplifiable using universal primers for 16SrRNA.

Results: Eighty-one (1.5%) isolates had a ciprofloxacin MIC > 0.25 ug/mL. The qnrA positive isolate yielded a product of expected size. All isolates tested were negative for the qnrA gene. One isolate of Salmonella enterica ssp. houtenae (IV or 4) tested positive for qnrB on PCR and sequencing confirmed a qnrB 5. The qnrS gene was identified in 9 salmonella isolates. Of these, 4 were serovar (S.) Corvallis, 2 S. Virchow, 1 S. Typhimurium, 1 S. Enteritidis and 1 S. Schwarzengrund. Sequences for 8 isolates were 100% homologous to published sequences for qnrS1 and 1 isolate (S. Virchow) differed from the published qnrS sequence by a single nucleotide. A history of foreign travel was reported for one isolate (the S. Schwarzengrund).

Conclusion: The plasmid mediated quinolone resistance determinants qnrB (1) and qnrS (9) were identified in 10 of 81 Salmonella enterica isolates with raised ciprofloxacin MICs. S. Corvallis is an uncommon serovar in our experience (0.2% of all isolates) and is remarkable that this serovar represents a high proportion of all qnrS positive isolates detected. There is no evidence of an epidemiological link between the S. Corvallis isolates.

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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