Plasmid-mediated quinolone resistance in non-Typhi serotypes of Salmonella enterica

Kathryn Gay*, Ari Robicsek, Jacob Strahilevitz, Chi Hye Park, George Jacoby, Timothy J. Barrett, Felicita Medalla, Tom M. Chiller, David C. Hooper

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

216 Scopus citations

Abstract

Background. Serious infections with Salmonella species are often treated with fluoroquinolones or extended-spectrum β-lactams. Increasingly recognized in Enterobacteriaceae, plasmid-mediated quinolone resistance is encoded by qnr genes. Here, we report the presence of qnr variants in human isolates of non-Typhi serotypes of Salmonella enterica (hereafter referred to as non-Typhi Salmonella) from the United States National Antimicrobial Resistance Monitoring System for Enteric Bacteria. Methods. All non-Typhi Salmonella specimens from the United States National Antimicrobial Resistance Monitoring System for Enteric Bacteria collected from 1996 to 2003 with ciprofloxacin minimum inhibitory concentrations ≥0.06 μg/mL (233 specimens) and a subset with minimum inhibitory concentrations ≤0.03 μg/mL (102 specimens) were screened for all known qnr genes (A, B, and S) by polymerase chain reaction. For isolates with positive results, qnr and quinolone resistance-determining region sequences were determined. Plasmids containing qnr genes were characterized by conjugation or transformation. Results. Conjugative plasmids harboring qnrB variants were detected in 7 Salmonella enterica serotype Berta isolates and 1 Salmonella enterica serotype Mbandaka isolate. The S. Mbandaka plasmid also had an extended-spectrum β-lactamase. Variants of qnrS on nonconjugative plasmids were detected in isolates of Salmonella enterica serotype Anatum and Salmonella enterica serotype Bovismorbificans. Conclusions. Plasmid-mediated quinolone resistance appears to be widely distributed, though it is still uncommon in non-Typhi Salmonella isolates from the United States, including strains that are quinolone susceptible by the criteria of the Clinical and Laboratory Standards Institute (formerly the National Committee for Clinical Laboratory Standards). The presence of this gene in non-Typhi Salmonella that causes infection in humans suggests potential for spread through the food supply, which is a public health concern.

Original languageAmerican English
Pages (from-to)297-304
Number of pages8
JournalClinical Infectious Diseases
Volume43
Issue number3
DOIs
StatePublished - 1 Aug 2006
Externally publishedYes

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