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).
Highlights
Considerable attention has been directed at the microbiological safety of powdered infant formula (PIF) (FAO/WHO, 2004; FAO/WHO, 2006)
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)
A total of 13 Enterobacteriaceae isolates were obtained from 8 samples (26.7%) in Nanchang, 6 isolates of K. pneumoniae and 7 isolates of E. sakazakii were isolated from the samples in the laboratory
Summary
Considerable attention has been directed at the microbiological safety of PIF (FAO/WHO, 2004; FAO/WHO, 2006). This has primarily been due to neonatal infections by Enterobacteriaceae include E. sakazakii and K. Pneumoniae which were associated with contaminated PIF (Caubilla-Barron et al, 2007; Forsythe et al, 2005) These products are not sterile, but are expected to comply with international microbiological standards. An increased resistance to antibiotics has been reported in K. Pneumoniae to cephalosporins is mediated by extended spectrum -lactamases (ESBLs) ESBLs are encoded by transferable conjugative plasmids which often encode resistant determinants to other classes of antibiotics (Bonnet, 2004). Recent reports have highlighted the emergence of ESBL producing strains endowed with an extremely wide spectrum of antibiotic
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