Antimicrobial susceptibility of Gram-negative bacteria causing intra-abdominal infections in China: SMART China 2011

Background The Study for Monitoring Antimicrobial Resistance Trends program monitors the activity of antibiotics against aerobic and facultative Gram-negative bacilli(GNBs) from intra-abdominal infections(IAIs) in patients worldwide.Methods In 2011, 1 929 aerobic and facultative GNBs from 21 hospitals in 16 cities in China were collected. All isolates were tested using a panel of 12 antimicrobial agents, and susceptibility was determined following the Clinical Laboratory Standards Institute guidelines.Results Among the Gram-negative pathogens causing IAIs, Escherichia coli(47.3%) was the most commonly isolated, followed by Klebsiella pneumoniae(17.2%), Pseudomonas aeruginosa(10.1%), and Acinetobacter baumannii(8.3%). Enterobacteriaceae comprised 78.8%(1521/1929) of the total isolates. Among the antimicrobial agents tested, ertapenem and imipenem were the most active agents against Enterobacteriaceae, with susceptibility rates of 95.1% and 94.4%, followed by amikacin(93.9%) and piperacillin/tazobactam(87.7%). Susceptibility rates of ceftriaxone, cefotaxime, ceftazidime, and cefepime against Enterobacteriaceae were 38.3%, 38.3%, 61.1%, and 50.8%, respectively. The leastactive agent against Enterobacteriaceae was ampicillin/sulbactam(25.9%). The extended-spectrum β-lactamase(ESBL) rates among E. coli, K. pneumoniae, Klebsiella oxytoca, and Proteus mirabilis were 68.8%, 38.1%, 41.2%, and 57.7%, respectively.Conclusions Enterobacteriaceae were the major pathogens causing IAIs, and the most active agents against the study isolates(including those producing ESBLs) were ertapenem, imipenem, and amikacin. Including the carbapenems, most agents exhibited reduced susceptibility against ESBL-positive and multidrug-resistant isolates.