First isolation of ciprofloxacin-resistant Salmonella enterica serovar Typhi in Taiwan

Typhoid fever is a major cause of disease burden in developing countries. The use of fluoroquinolones, once considered the drugs of choice, should be re-evaluated due to the emergence of quinolone-resistant Salmonella enterica serovar Typhi. In Taiwan, typhoid fever is rare but constitutes an important public health concern.

In August 2011, two ciprofloxacin-resistant S. Typhi isolates were identified from one patient who had recently travelled to India. The two isolates together with four other ciprofloxacin-susceptible S. Typhi isolates were subjected for molecular investigation. Polymerase chain reaction (PCR) and sequencing were used to analyze the resistance mechanisms. Pulsed-field gel electrophoresis (PFGE) was performed to delineate the genetic relatedness among the isolates.

In 2011, a total of 49 typhoid fever cases were reported to the Center for Disease Control in Taiwan, with a significant increase in indigenous cases in northern Taiwan from August to November. In the two S. Typhi isolates with complete resistance to ciprofloxacin [minimum inhibitory concentration (MIC) >32 μg/mL], multiple point mutations in the quinolone resistance-determining regions (QRDRs) of gyrA and parC genes were identified. A unique PFGE pattern was found in the resistant isolates and was different from the other representative susceptible isolates.

The first ciprofloxacin-resistant S. Typhi infection in Taiwan is reported. The emergence and spread of antimicrobial-resistant S. Typhi infection as a result of international travel may become a threat to public health in Taiwan. Clinicians should be well alert when treating patients who may have acquired resistant infections associated with international travel among endemic regions.