Journal of Medical Microbiology and Infectious Diseases

en In vitro Synergistic Activity of Ceftazidime-Avibactam and Aztreonam Against Carbapenem-resistant Enterobacterales Anti-microbial agents, resistance and treatment protocols Anti-microbial agents, resistance and treatment protocols Original article Original article <div style="text-align: justify;">Introduction: Infections caused by multidrug-resistant Enterobacterales pose a significant global health challenge, thus necessitating novel therapeutic strategies. The increasing prevalence of carbapenem-resistant Enterobacterales has led to reliance on colistin and polymyxins as last-resort antibiotics. However, emerging colistin resistance and associated polymyxin toxicity have significantly limited their use. Aztreonam is effective against metallo-β-lactamase (MBL)-producing pathogens but requires protection from co-produced enzymes such as extended-spectrum β-lactamases (ESBLs), AmpC cephalosporinases, and other carbapenemases. Avibactam, a non-β-lactam β-lactamase inhibitor, inhibits ESBLs, Klebsiella pneumoniae carbapenemase (KPC), certain oxacillinase (OXA)-48-like enzymes, and AmpC cephalosporinases but is ineffective against metallo-β-lactamases. This study evaluated the in vitro synergy of ceftazidime-avibactam with aztreonam as a potential colistin-sparing strategy for carbapenem-resistant Enterobacterales infections. Methods: In a prospective cross-sectional study from July 2022 to June 2023, 97 carbapenem-resistant Gram-negative clinical isolates (prevalence: 97/8876 =1.09%) were obtained from 8876 samples tested for aerobic bacterial culture and antimicrobial susceptibility at a tertiary care hospital in Pune, India. For 69 Enterobacterales isolates resistant to ertapenem, imipenem, and meropenem, synergy between ceftazidime-avibactam and aztreonam was tested using disk diffusion and modified E-test/disk diffusion method, interpreted as per the guidelines of the Clinical and Laboratory Standards Institute (CLSI). Results: Enterobacterales comprised 69 (71.13%) of isolates, with 35 (50.73%) of these demonstrating synergy between ceftazidime-avibactam and aztreonam. Klebsiella pneumoniae (33/69; 47.83%) was the predominant species, followed by Escherichia coli (26/69; 37.68%) and Citrobacter species (10/69; 14.49%). Conclusion: In vitro synergy between ceftazidime-avibactam and aztreonam was observed in 50.73% of carbapenem-resistant Enterobacterales isolates, suggesting a possible colistin-sparing alternative for infections such as complicated urinary tract infections, intra-abdominal infections, and hospital-acquired pneumonia; however, further clinical studies are needed to validate its efficacy. </div> Aztreonam, Ceftazidime-avibactam, Carbapenem-resistant Enterobacterales, Colistin, Metallo-β-lactamases, Synergy testing 197 205 http://jommid.pasteur.ac.ir/browse.php?a_code=A-10-441-11&slc_lang=en&sid=1 Chetana Joshi chetana.joshi91@gmail.com 0000-0001-8400-6773 No Department of Microbiology, PCMC Postgraduate Institute and Yashwantrao Chavan Memorial Hospital, Pimpri, Pune, India Swati Mudshingkar drswati2006@gmail.com 0000-0002-6388-7441 Yes Department of Microbiology, PCMC Postgraduate Institute and Yashwantrao Chavan Memorial Hospital, Pimpri, Pune, India Jaishree Petkar info@ycmhpgi.org 0000-0001-6097-8535 No Department of Microbiology, PCMC Postgraduate Institute and Yashwantrao Chavan Memorial Hospital, Pimpri, Pune, India Sachin Deorukhkar sdeorukhkar@pmtpims.org 0000-0001-6204-9393 No Department of Microbiology, PCMC Postgraduate Institute and Yashwantrao Chavan Memorial Hospital, Pimpri, Pune, India Kiran Kakade kargar.mh@gmail.com No Department of Microbiology, PCMC Postgraduate Institute and Yashwantrao Chavan Memorial Hospital, Pimpri, Pune, India