MBLs, Rather Than Efflux Pumps, Led to Carbapenem Resistance in Fosfomycin and Aztreonam/Avibactam Resistant Elizabethkingia anophelis

OBJECTIVE: To assess the risk factors associated with infections and in-hospital mortality, antimicrobial susceptibility patterns and carbapenem resistance mechanisms in E. anophelis. METHODS: This retrospective case–control study was conducted to reveal the risk factors associated with Elizabethkingia anophelis (E. anophelis) infection and in-hospital mortality in a university tertiary hospital in southwest China, using multivariable logistic-regression analyses. Complete 16S rRNA gene sequencing was used to reconfirm the identity of all isolates. We employed the broth microdilution method to investigate the antimicrobial susceptibility profiles. The presence of resistance genes was confirmed by polymerase chain reaction and DNA sequencing. Full-length resistance genes were cloned into the pET-28a vector for further functional studies. RESULTS: Our multivariate analysis indicated that coronary artery disease, chronic obstructive pulmonary disease, surgery in the past 6 months, anemia and systemic steroid use were independent risk factors for the acquisition of E. anophelis. Additionally, anemia was the only independent risk factor associated with in-hospital mortality in patients with E. anophelis infections. E. anophelis isolates showed high in-vitro susceptibility towards minocycline (100%) and piperacillin/tazobactam (71.8%), but were resistant to colistin, fosfomycin, ceftazidime/avibactam and aztreonam/avibactam. The PCR revealed the presence of blaGOB and blaBlaB in 37 isolates, and blaCME β-lactamase genes in 36 isolates out of 39 E. anophelis isolates. Additionally, we showed that two metallo-β-lactamases (MBLs) BlaB and GOB, were responsible for carbapenem resistance and the serine-β-lactamase, CME, was functionally involved in resistance to cephalosporins and monobactams. Interestingly, the various putative efflux pumps in E. anophelis were not responsible for resistance. CONCLUSION: Our findings will help clinicians to identify high-risk patients and suggests that minocycline should be considered as a therapeutic option for E. anophelis infections. Additionally, carbapenem resistance in E. anophelis is mainly associated with the MBLs, BlaB and GOB, rather than various putative efflux pumps.