Abstract

Morbidity and mortality of infant infections caused by contaminated powdered infant formula (PIF) have been reported worldwide, and pathogens like Enterobacter sakazakii andKlebsiella pneumoniae are important causative agents. To evaluate the prevalence of antibiotic resistance in E. sakazakii and K. pneumoniae that caused PIF contamination in Chinese market, all the isolates from PIF were analyzed for detecting resistance to antibiotics. 30 PIF samples were randomly purchased in Chinese market in 2009 and 7 E. sakazakii and 6 K. pneumoniae isolates were obtained from 8 samples (26.7%), the isolates were evaluated for antibiotics susceptibility by disk diffusion technique as recommended by the Clinical Laboratory Standards Institute (CLSI). Susceptibility results showed that each isolate had different levels of resistance to β-lactam antibiotics, while sensitive to fluoroquinolones and aminoglycosides. One K. pneumoniae and one E. sakazakii isolate almost resisted all Cephalosporins chosen; the double-disk synergy test (DDST) showed these two isolates producing extended spectrum β-lactamase (ESBL). This is the first report of ESBL-produing in E. sakazakii from powdered infant formula in China.

Key words: Klebsiella pneumonia, Enterobacter sakazakii, disk diffusion, antibiotic resistance, extended spectrum β-lactamase (ESBL).