Antimicrobial Susceptibility Trends Among Gram-Negative Bacilli Causing Bloodstream Infections: Results from the China Antimicrobial Resistance Surveillance Trial (CARST) Program, 2011-2020

The antimicrobial resistance profiles of gram-negative bacilli causing bloodstream infections have changed over time, while comprehensive and real-time surveillance data are limited in China. This study aimed to review the antimicrobial susceptibility trends among main gram-negative bacilli isolated from blood specimens in China.

From 2011 to 2020, a total of 4352 non-duplicate isolates were collected from 21 tertiary hospitals in 18 provinces or cities across China. Antimicrobial susceptibility testing was conducted by the agar dilution method recommended by the Clinical and Laboratory Standards Institute (CLSI), and the results were interpreted using CLSI criteria.

During this 10-year surveillance period, meropenem and imipenem were the most effective agents against Escherichia coli (resistance remaining <5%). The proportion of ESBL-producing isolates in carbapenem-susceptible E. coli displayed a decreasing trend (from 72.9% to 51.2%). The resistance rates of Klebsiella pneumoniae to meropenem and imipenem increased from 3.3% and 1.6% in the 2011-12 period to 15.0% and 15.4% in the 2019-20 period, respectively. Carbapenems and amikacin were the most active agents against Enterobacter cloacae. The resistance rates of Pseudomonas aeruginosa to meropenem and imipenem increased from 13.1% and 17.7% in the 2015-16 period to 24.5% and 21.0% in the 2019-20 period, respectively. Few agents showed activity against Acinetobacter baumannii. The frequency of imipenem-non-susceptible A. baumannii remained stable (remaining ~70%).

The rapid spread of carbapenem-resistant K. pneumoniae has been serious in recent years. Conversely, the prevalence of ESBL-producing isolates was decreased. Carbapenems are still effective against gram-negative bacilli causing BSIs, except for A. baumannii. More attention should be given to A. baumannii, considering its high resistance against different classes of antimicrobials.