Emergence of Qnr determinants in human Salmonella isolates in Taiwan

The aim of this study was to determine the prevalence and characteristics of qnr-carrying Salmonella isolates from humans in southern Taiwan. A total of 446 Salmonella isolates collected between 2003 and 2006 were screened for qnrA, qnrB and qnrS by PCR experiments. Genetic structures of qnr were determined by PCR-based methods or direct sequencing of plasmid DNA. qnrB2 and qnrS1 were detected in two serovar Enteritidis isolates and two serovar Typhimurium isolates, respectively. One qnrS1-positive isolate was found to produce the CMY-2 AmpC enzyme. qnrS1 was identified on a 10 kb plasmid, which exhibited > 99% nucleotide sequence identity with plasmid TPqnrS-1a reported from the UK. qnrB2 was found in a complex sul1-type class 1 integron on a > 100 kb plasmid. This study demonstrated the occurrence of qnrB2 and qnrS1 in Salmonella for the first time in Taiwan and characterized their genetic structures.