Purpose: The Chinese Meropenem Surveillance Study (CMSS) was conducted every 2 years from 2010 to 2018 to monitor the antimicrobial activity of commonly used antimicrobial agents against nosocomial gram-negative bacilli in China.
Methods: From 2010 to 2018, 6,537 gram-negative bacilli were collected from 14 teaching hospitals. The minimum inhibitory concentrations (MICs) of meropenem and other antimicrobial agents were determined using the agar dilution and broth microdilution methods.
Results: Continuous surveillance indicated that, except for Klebsiella pneumoniae , the susceptibility of Enterobacterales  to carbapenems was relatively stable over time. Carbapenems had the highest activity against the tested isolates, with MIC₉₀ values (MIC for 90% of organisms) ranging from 0.032 mg/L to 8 mg/L. More than 90% of bacteria were susceptible to either meropenem or imipenem; more than 80% were susceptible to ertapenem. The prevalence of extended-spectrum beta-lactamase (ESBL)-producing E. coli, K. pneumoniae , and P. mirabilis  each year was 50.4– 64.3%, 18– 41.2%, and 1.9– 33.8%, respectively. The prevalence of carbapenem-resistant K. pneumoniae  (CRKP) and carbapenem-resistant Acinetobacter baumannii  (CRAB) continued to increase significantly over time, from 7.6% to 21.2% and 64.6% to 69.3%, respectively. The prevalence of CRKP was higher from urinary tract infections (25.4%) than from bloodstream infections (14.2%), intra-abdominal infections (14.5%), and respiratory infections (14.4%). In total, 129 CRKP isolates were evaluated by PCR; of these, 92 (71.3%) carried the bla _KPC-2 gene. Colistin maintained very high in vitro antimicrobial activity against P. aeruginosa  and A. baumannii  (more than 95% of isolates exhibited susceptibility at all timepoints).
Conclusion: The results indicate an increase in K. pneumoniae  resistance to carbapenems over time, mainly owing to KPC-type carbapenemase production. A. baumannii  was severely resistant to carbapenems in China. Ongoing MIC-based resistance surveillance, like CMSS, provides additional data for clinical anti-infective treatment.
Keywords: CMSS, gram-negative bacilli, antimicrobial susceptibility surveillance, carbapenem-resistant