Molecular epidemiology and antimicrobial susceptibility of Salmonella enterica serotype Stanley isolates in Taiwan.

BACKGROUND AND PURPOSE: Salmonella enterica serotype Stanley became the third most common non-typhoidal Salmonella serotype among human isolates in 2004. The present study was conducted to gain further understanding of the epidemiology and antimicrobial suseptibility of S. Stanley. METHODS: A total of 20 culture-confirmed cases were retrieved from the Center for Disease Control collection and analyzed. Clinical features and demographic data of the cases were analyzed. Laboratory investigation of the isolates included antimicrobial susceptibility testing and molecular typing by pulsed-field gel electrophoresis. Ceftriaxone-non-susceptible isolates were further examined by polymerase chain reaction, sequencing, and Southern blot hybridization. RESULTS: The cases studied were distributed widely across Taiwan, suggesting that the infection was an island-wide problem. S. Stanley predominantly caused infections in patients under the age of 5 years (75%). The most common type of illness was uncomplicated enterocolitis. Molecular typing showed 1 predominant genotype with 5 subtypes among these isolates. Antimicrobial resistance to ampicillin (75%), chloramphenicol (95%), and trimethoprim-sulfamethoxazole (95%) was common. Two isolates expressed non-susceptibility to ceftriaxone, and a bla(CMY-2) gene was identified on an 80-kb plasmid in both isolates. CONCLUSION: The increase in S. Stanley infections may be associated with the spread of an epidemic clone, although this requires further epidemiological surveillance. In view of the high rate of antimicrobial resistance, especially the emergence of resistance to third-generation cephalosporins, continued surveillance of the infections caused by this bacterium should be undertaken.