In vitro susceptibility of carbapenemresistant enterobacterales to colistin, tigecycline and ceftazidime-avibactam

Abstract

Infections associated with carbapenem-resistant Enterobacterales (CRE) represent a significant public health concern due to their resistance to carbapenems and other commonly prescribed antibiotics. This study focused on assessing the in vitro susceptibility of CRE isolates to colistin, tigecycline and ceftazidime-avibactam (CZA), thus offering valuable insights into resistance mechanisms and potential treatment strategies. From Sultan Ahmad Shah Medical Center@IIUM, 19 clinical CRE isolates were analysed, primarily obtained from adult patients with an approximately equal gender distribution. Identification of the isolates was performed using MALDI -TOF MS, while carbapenemase production was determined using the mCIM method. Antimicrobial susceptibility testing (AST) was conducted using the VITEK 2 system and E-test, with resistance rates assessed following CLSI guidelines. Key risk factors for CRE infection included underlying diseases, recent hospitalizations and the presence of indwelling medical devices. Overall, carbapenemase-producing (CP) CRE demonstrated higher resistance rates compared to carbapenems and CZA compared to non-CP variants. Tigecycline however, remained effective against CP CRE, with low resistance observed among non-CP CRE. Meanwhile, uniform resistance rate was observed in both CP and non-CP isolates to colistin and other β-lactam antibiotics tested. Resistance rates varied significantly across species, emphasizing the complexity of CRE infections. This study highlights the urgent need for robust antimicrobial stewardship programs and routine carbapenemase detection to guide effective therapy. The high prevalence of CP CRE and the observed variability in species-specif ic resistance patterns underscore the importance of tailored treatment strategies to manage and mitigate the threat of CRE infections at SASMEC@IIUM.