JAC Advance Access published online on November 4, 2008
Journal of Antimicrobial Chemotherapy, doi:10.1093/jac/dkn452
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Original research |
Characterization of Salmonella enterica isolates from infants and toddlers in Wuhan, China
1 The National Center for Surveillance of Antimicrobial Resistance, The State Food and Drug Administration, Beijing, People’s Republic of China 2 Tongji Hospital, Huazhong University of Science and Technology, Wuhan, People’s Republic of China 3 The Institute of Nutrition and Food Safety, Chinese Center for Disease Control and Prevention, Beijing, People’s Republic of China
Received 17 July 2008; returned 2 September 2008; revised 6 October 2008; accepted 6 October 2008
* Corresponding author. Tel: +86-10-67095616; Fax: +86-10-65115148; E-mail: nicpbp{at}263.net
Background: Extended-spectrum cephalosporins and fluoroquinolones are important antimicrobials for treating invasive salmonellosis, and emerging resistance to these antimicrobials is of paramount concern. This study reports on the antimicrobial susceptibility and molecular characterization of Salmonella enterica isolates recovered in 2006 from 0- to 3-year-old outpatients in China.
Methods: The isolates were subjected to serotyping, antimicrobial susceptibility testing, screening for β-lactamase genes, mutations in the quinolone resistance determining regions (QRDRs), qnr alleles and aac-(6')-Ib-cr by PCR followed by DNA sequence analysis. All Salmonella Typhimurium isolates and 43 selected non-Typhimurium isolates were further characterized by PFGE to determine the genetic relatedness.
Results: From 3746 paediatric outpatient stool samples, 221 (5.9%) S. enterica isolates of 29 distinct serotypes were recovered. The antimicrobial resistance profiles differed among serotypes. Ciprofloxacin-resistant isolates were concentrated in serotype Typhimurium that were resistant to at least four additional non-quinolone antimicrobials. Nineteen out of 22 ciprofloxacin-resistant Salmonella Typhimurium isolates were grouped into one PFGE cluster. Plasmid-mediated quinolone resistance determinant aac-(6')-Ib-cr was detected in 18 S. enterica isolates and 4 isolates also carried qnr alleles. Plasmid-mediated blaCTX-M-14-like genes were found in seven ceftriaxone-resistant isolates, and two isolates also exhibited reduced susceptibility to ciprofloxacin.
Conclusions: Based on these results, fluoroquinolones should not be used to treat the invasive Salmonella Typhimurium infections in this local community. The monitoring programme should stay vigilant for ceftriaxone-resistant S. enterica isolates with reduced fluoroquinolone susceptibility.
Key Words: quinolones , ESBLs , antimicrobial resistance , qnr , CTX-M
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