Antimicrobial susceptibility of nonfermenting gram-negative bacteria: results from China Antimicrobial Resistance Surveillance Trial Program, 2013-2014

Abstract

Objective To investigate the antimicrobial susceptibility of nonfermenting gram-negative bacteria in nationwide's tertiary hospitals and understand the trend of antimicrobial resistance. Methods The clinical isolates were collected from 19 tertiary hospitals in 19 cities nationwide over the period from July 2013 to June 2014 according to the same protocol. About 100 strains were collected from each hospital. The minimal inhibitory concentrations (MICs) were tested using agar dilution method recommended by Clinical and Laboratory Standards Institute (CLSI) in the central laboratory (Institute of Clinical Pharmacoloty, Peking University First Hospital). The susceptibilities of isolates to antimicrobial agents were determined using CLSI or European Committee on Antimicrobial Susceptibility Testing (EUCAST) 2015 guideline. SPSS 17.0 was used to caculated MIC50, MIC90, MICrange, susceptible rate and resistance rates. Results A total of 1 535 pathogenic isolates were studied. Based on the MIC results, resistance rate of Pseudomonas aeruginosa and Acinetobacter baumannii to imipenem were 28.0% (180/644) and 70.5% (456/647) . Multidrug resistance rate of P. aeruginosa and A. baumannii were 34.9% (225/644) and 79.6% (515/647), and extensively drug-resistance rate were 9.8% (63/644) and 72.2% (467/647), respectively. Resistance rate of strains isolated from intensive care unit (ICU) were higher than those from non-ICU, especially in A. baumannii (about 52.4%-90.9% vs 34.0%-73.3%, t=2.209, P=0.032). Relevance ratio and resistance rate of nonfermenting gram-negative bacteria in children (≤14 years) were significantly lower than those from adults and old people (≥65 years) (about 3.2%-50.0% vs 7.1%-81.3%, t=-2.800--5.671, P<0.01). Resistance rate of P. aeruginosa isolated from sputum were higher than those isolated from blood and drainage fluid (about 18.7%-74.2% vs 0.0%-75.4%, t=2.337-2.707, P<0.05), and resistance rate of A. baumannii isolated from drainage fluid were higher than urine (about 19.7%-88.2% vs 6.0%-66.0%, t=2.884, P=0.006). Conclusions Compared with past surveillance results, resistance rates of.P. aeruginosa, Stenotrophomonas maltophilia, and Burkholderia cepacia were steady. Sustained growth of resistance rate of A. baumannii was identified, especially to some antibiotics showing good in vitro activity former, such as minocyclin et al. Multidrug resistance nonfermenting gram-negative bacterial has been a worldwide challenge for healthcare management.(Chin J Lab Med, 2016, 39: 130-138) Key words: Drug Resistance, Microbial; Gram-Negative Bacteria; Microbial Sensitivity Tests; Drug Monitoring