Prevalence, Antimicrobial Susceptibility, and Molecular Characteristics of Ceftazidime-Avibactam-Resistant Klebsiella pneumoniae in a Chinese Hospital

Jun Li,1,2,* Haolan Wang,1,* Zhaojun Liu,1 Yubing Xia,1 Yongmei Hu,1,2 Haichen Wang,1,2 Fengjun Xia,1,2 Mingxiang Zou1,2 1Department of Clinical Laboratory, Xiangya Hospital, Central South University, Changsha, Hunan, 410008, People’s Republic of China; 2National Clinical Research Center for Geriatric Diseases (Xiangya Hospital), Changsha, Hunan, 410008, People’s Republic of China*These authors contributed equally to this workCorrespondence: Mingxiang Zou, Department of Clinical Laboratory, Xiangya Hospital, Central South University, Changsha, Hunan, 410008, People’s Republic of China, Tel +86 13907496278, Email [email protected]: The mechanisms underlying ceftazidime-avibactam resistance in carbapenem-resistant Klebsiella pneumoniae (CRKPCZA-R) remain to be elucidated.Methods: CRKPCZA-R isolates were screened from non-repetitive CRKP isolates at our hospital from January 1, 2018 to October 30, 2021. The antimicrobial susceptibility and molecular characteristics of CRKPCZA-R were analyzed by broth microdilution method and next-generation sequencing, respectively.Results: In total, 67 of 623 CRKP isolates (10.8%) were identified as CRKPCZA-R. The susceptibility rates of CRKPCZA-R to polymyxin B, tigecycline, aztreonam-avibactam, and cefiderocol were 97.0% (65/67), 83.6% (56/67), 100.0% (67/67), and 94.0% (63/67), respectively. The most prevalent resistance gene was blaNDM-1 (44.8%, 30/67), followed by blaIMP-4 (9.0%, 6/67), blaNDM-5 (7.5%, 5/67), and blaNDM-4 (1.5%, 1/67). Furthermore, 37.3% (25/67) of the CRKPCZA-R isolates co-harbored more than two carbapenemase-encoding genes, mainly blaNDM-1 and blaKPC-2 (31.3%, 21/67). The enzyme inhibitor enhancement method detected carbapenemase activity with high sensitivity, except for isolates carrying two or more carbapenemases. Notably, 21 KL64-ST11 CRKPCZA-R isolates presented blaNDM-1, blaKPC-2, and ompk36 deletion, and 17 co-harbored two or more high virulence gene markers. Patients infected with these 21 isolates were older and experienced more serious illness compared to those infected with other drug-resistant isolates.Conclusion: The detection rate of CRKPCZA-R was relatively high due to the metallo-β-lactamase-producing isolates. Although enzyme inhibitor enhancement method can detect carbapenemases with high sensitivity and specificity, and provide an important reference for drug selection, it is not as effective for isolates carrying two or more carbapenemases. Patients infected with CRKPCZA-R co-harboring both blaKPC-2 and blaNDM-1 should be closely monitored.Plain Language Summary: The resistance mechanisms of CRKPCZA-R remain to be uncovered. In our study, the detection rate of CRKPCZA-R was relatively high due to the metallo-β-lactamase-producing isolates. The sensitivity of CRKPCZA-R to antibacterial agents was evaluated in vitro, and revealed high susceptibility to aztreonam-avibactam, cefiderocol, polymyxin B, and tigecycline. The enzyme inhibitor enhancement method plays an important role in guiding the selection of clinical antibiotics due to its high sensitivity and specificity. Specifically, when the inhibition zone diameter of K-B method CZA is 20-22 mm, CZA can be used alone if it produces serine enzyme, but not if it produces metalloenzyme. Patients infected with CRKPCZA-R harboring both blaKPC-2 and blaNDM-1 were older and experienced more serious illness compared to those infected with other drug-resistant isolates, and should therefore be monitored more closely.Keywords: carbapenem-resistant Klebsiella pneumoniae, ceftazidime–avibactam, resistance mechanism, homology