Increasing quinolone resistance and multidrug resistant isolates among Salmonella enterica in Hong Kong.

OBJECTIVES

To study the antimicrobial susceptibility and molecular epidemiology of Salmonella enterica isolates from 2005 to 2010 in Hong Kong.

METHODS

S. enterica isolates from 2005 to 2010 in one of the hospital clusters were serotyped and studied their antimicrobial susceptibility by determining the minimal inhibitory concentration of 17 antimicrobial agents and their relatedness by pulsed-field gel electrophoresis (PFGE).

RESULTS

A total of 60 S. enterica serovars were identified among the 963 strains of Salmonella from 2005 to 2010. Enteritidis (47.3%) and Typhimurium (17.2%) were the two most common serovars. Ciprofloxacin non-susceptibility increased significantly from 39.3% in 2005 to 63% in 2010 (p < 0.05) and the percentage of multidrug resistant strains increased from 17.8% in 2005 to 36.2% in 2010 (p < 0.05). However, resistance to the third generation cephalosporins (1.4%) remained low. More strains of S. Typhimurium than other Salmonella serovars were resistant to the antimicrobial agents tested than S. Enteritidis. PFGE analysis showed there were predominant clones of S. Enteritidis, S. Typhimurium and S. Stanley circulating in the community, and two outbreaks caused by S. Enteritidis and S. Virchow during the study period.

CONCLUSIONS

The study showed both a worrying percentage of Salmonella strains resistant to quinolone and of multidrug resistant strains. PFGE identified two outbreaks in the study period.