Surveillance for antimicrobial resistance trends over time provides important information for governments, industry, scientists and clinicians, thereby improving the use of antibiotics appropriately, increasing public awareness and enhancing infection prevention and control methods [7, 8]. Study research has been the impetus for the development of several national and global antimicrobial resistance strategies that have focused on treatments for antimicrobial-resistant ESBL-producing E. coli and K. pneumoniae [9]. Herein, we observed a continued increasing trend toward multiple drug-resistant ESBL-producing rates in E. coli and K. pneumoniae.
Various studies have reported increased resistance rates among bacterial organisms worldwide, especially ESBL-producing strains, with ESBL-producing E. coli and K. pneumonia as the two predominant strains [10]. Several significant trends were noted in this 6-year surveillance study. The number of E. coli strains increased, while the proportion of E. coli strains was stable, which suggested that the overall number of strains increased. However, the concerning finding is the increase in the numbers and proportion of ESBL-producing E. coli and K. pneumoniae strains, which were similar to those reported in CHINET and CARSS [4]. This trend has also been reported and most likely represents the global expansion of ESBL-producing strains [11].
The spread of ESBL genes in E. coli or Klebsiella spp. is a huge challenge to hospitals and the government [11]. Carbapenem antibiotics are the treatment of primary choice for serious infections caused by ESBL-producing strains; however, carbapenem resistance has increased recently and globally [12]. ESBL-producing Klebsiella strains have been susceptible to carbapenems in the early years, which include imipenem and meropenem [13]. The prevalence of carbapenem-resistant ESBL-producing K. pneumonia showed a markedly increasing trend, as did K. pneumonia strains, while non-ESBL-producing K. pneumonia showed a decreasing trend. Carbapenems are recommended as first-line therapy for serious infections caused by ESBL-producing E. coli and K. pneumonia [14]. Furthermore, the inappropriate and excessive use of carbapenems in clinical practice has accelerated the emergence and extensive spread of carbapenem-resistant strains [15]. Various surveillance programs have reported that the resistance rate of carbapenem strains has increased during the last decade, with the predominant pathogens being E. coli and K. pneumonia [1, 2, 4].
The most concerning finding of this study is the increase in antibiotic resistance to multiple antimicrobial agents in K. pneumoniae and ESBL-producing K. pneumoniae isolates. Because the main genotypes of ESBL in China are CTX-M groups and almost all ESBL-producing strains are resistant to cefazolin, cefuroxime, cefotaxime, and ceftriaxone, cefotaxime resistance has been recommended as a marker of ESBL-producing isolates [16]. The resistance rates to cefoperazone-sulbactam, piperacillin-tazobactam, ciprofloxacin, and fosfomycin showed an increasing trend from 2016 to 2021, which was consistent with the marked increase in ESBL-producing K. pneumonia. This trend also exists in amikacin. Furthermore, the prevalence of cefepime-, cefoperazone-sulbactam-, piperacillin-tazobactam-, cotrimoxazole-, amikacin-, ciprofloxacin- and fosfomycin-resistant ESBL-producing E. coli also showed a markedly increasing trend. In China, K. pneumoniae carbapenemase-2 (KPC-2) is the dominant genotype of carbapenem-resistant K. pneumoniae (CRKP) [17]. The dominant clone is ST11, which usually harbors multiple plasmids and carries multiple resistance genes. The spread of ST11 may contribute to the increasing trend of multiple drug resistance and extensive drug resistance in K. pneumoniae [18].
There are some limitations of this study. Because the study was retrospective, we could not classify hospital- and community-acquired infections and evaluate the duration of hospital stay and patient transfers between different services [19, 20]. Molecular methods and a combination of biochemical methods were not used to determine the resistance mechanisms of multidrug resistant strains [16]. Second, the majority of our strains were ESBL-producing E. coli and K. pneumonia, which may not apply to other Enterobacteriaceae [14].
In conclusion, this study revealed a number of increasing and decreasing trends in antimicrobial resistance. The marked increase in carbapenem-resistant K. pneumoniae was the most remarkable change in antimicrobial resistance observed from 2016 to 2021 in China.