Pulsed-field gel electrophoresis and mutation typing of gyrA gene of quinolone-resistant Salmonella enterica serovar Paratyphi A isolated from outbreak and sporadic cases, 1998-2002, Korea

In early 2002, over 200 people in the city of Pusan. Korea suffered from paratyphoid fever resulting from Salmonella Paratyphi A infection. Antimicrobial susceptibility tests and XbaI pulsed-field gel electrophoresis (PFGE) were conducted to 54 Salmonella Paratyphi A isolated from humans during the period of 1998 to 2002. Most of the isolates (83%) were only nalidixic acid-resistant and 78% were X 1 PFGE patterns. Also, we measured the MIC of ciprofloxacin and screened gyrA mutation(s) using allele-specific PCR and restriction fragment length polymorphism (AS-PCR-RFLP). The representative 5 isolates in 2002 and 1 isolate in 2000 were 1 μg/ml of MIC and had mutation at the 83rd codon in gyrA. These data suggest that the outbreak in the early 2002 might have been due to dissemination of the strain present in 2000. Also, decreased susceptibility to ciprofloxacin was partly due to the mutation at the 83rd codon in gyrA.