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Epidemiology of a new population of quinolone-resistant Salmonella enterica

Abstract number: P2090

Lindgren M., Kotilainen P., Mahlamäki V., Huovinen P., Lukinmaa S., Piddock L.J.V., Siitonen A., Hakanen A.J.

Objectives: In 2003, we described a new quinolone resistance phenomenon in Salmonella enterica isolates from Southeast Asia. These isolates show reduced ciprofloxacin susceptibility but are susceptible or only low-level resistant to nalidixic acid. The purpose of the present work was to survey the epidemiology of this new resistance phenotype.

Methods: In this study, 599 Salmonella enterica isolates collected between 2002 and 2007 from Finnish travellers returning from abroad were analysed and the results were compared with 829 Salmonella isolates collected between 1995 and 2001. Annually the first 100 foreign Salmonella isolates were collected. The MICs of the isolates to ciprofloxacin and nalidixic acid were determined by the standard agar dilution method according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. The susceptibility data were analysed by using the WHONET 5.4 computer programme.

Results: From 1995 to 2002, all Salmonella isolates showing reduced ciprofloxacin susceptibility were uniformly resistant to nalidixic acid. From 2003 to 2007, 9 (9.0%), 8 (8.1%), 2 (2.0%), 5 (5.0%) and 13 (13.0%) of the tested isolates, respectively, showed reduced ciprofloxacin susceptibility (MIC geqslant R: gt-or-equal, slanted0.125 mg/L) but were either susceptible (MIC < 32 mg/L) or low-level resistant (MIC=32 mg/L) to nalidixic acid. Epidemiological studies showed that all isolates showing the new resistance phenotype were from Southeast Asia, whereas the isolates exhibiting reduced ciprofloxacin susceptibility and nalidixic acid MIC > 32 mg/L were from different origins, 50% of them being from Southeast Asia. Among the new resistance phenotype, S. Corvallis and S. Stanley were the most prevalent serotypes, whereas among the nalidixic acid resistant isolates, S. Enteritidis and S. Virchow were the most prevalent.

Conclusion: Our study revealed that the new phenotype of quinolone-resistant Salmonella enterica is increasing. Moreover, this phenotype was found in several serotypes being, thus, not restricted to one clone only. Although these strains are clustered in Southeast Asia, they are of concern since the amount of travellers is continuously increasing in that part of the world.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Barcelona, Spain
Presentation type:
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