Introduction: Carbapenem resistant Enterobacterales (CRE) is a rapidly unfolding concern in the realm of public health. Ceftazidime-Avibactam combination has excellent in vitro activity against Gram negative pathogens showing promising results with Aztreonam. Objective: To determine the phenotypic synergy of Ceftazidime-Avibactam with Aztreonam in Carbapenem resistant Enterobacterales. Methodology: 100 Carbapenem resistant Enterobacterales were included in the study and tested for Ceftazidime-Avibactam (CZA) sensitivity by Vitek2 using Critical Alert cards. Phenotypic synergy testing of CZA resistant isolates with Aztreonam (ATM) was done by Disc-E strip method. ATM discs were placed 15mm away from centre of CZA strip and incubated overnight at 37°C. Reduction in MIC of CZA by ≥3 folds and zone of inhibition around ATM >21mm was reported as synergy positive. Isolates were further tested for presence of genes coding for bla-NDM and bla-OXA-48 by conventional PCR. Results: 62/100 (62%) isolates were Klebsiella pneumoniae and 38/100 (38%) were Escherichia coli. 61/62 (98%) Klebsiella pneumoniae and 36/38 (94%) Escherichia coli isolates were synergy positive. 1 (2%) Klebsiella pneumoniae and 2 (6%) Escherichia coli were synergy negative. PCR identified bla-NDM gene in 46(46%), bla-OXA-48 in 21(21%), co-production of both in 27(27%) isolates. 6(6%) isolates were negative for both genes. Conclusion: Multidrug resistance is a threat to mankind and this combination of Ceftazidime-Avibactam with Aztreonam will help in combating this problem.

Introduction: Carbapenem resistant Enterobacterales (CRE) is a rapidly unfolding concern in the realm of public health. Ceftazidime-Avibactam combination has excellent in vitro activity against Gram negative pathogens showing promising results with Aztreonam. Objective: To determine the phenotypic synergy of Ceftazidime-Avibactam with Aztreonam in Carbapenem resistant Enterobacterales. Methodology: 100 Carbapenem resistant Enterobacterales were included in the study and tested for Ceftazidime-Avibactam (CZA) sensitivity by Vitek2 using Critical Alert cards. Phenotypic synergy testing of CZA resistant isolates with Aztreonam (ATM) was done by Disc-E strip method. ATM discs were placed 15mm away from centre of CZA strip and incubated overnight at 37°C. Reduction in MIC of CZA by ≥3 folds and zone of inhibition around ATM >21mm was reported as synergy positive. Isolates were further tested for presence of genes coding for bla-NDM and bla-OXA-48 by conventional PCR. Results: 62/100 (62%) isolates were Klebsiella pneumoniae and 38/100 (38%) were Escherichia coli. 61/62 (98%) Klebsiella pneumoniae and 36/38 (94%) Escherichia coli isolates were synergy positive. 1 (2%) Klebsiella pneumoniae and 2 (6%) Escherichia coli were synergy negative. PCR identified bla-NDM gene in 46(46%), bla-OXA-48 in 21(21%), co-production of both in 27(27%) isolates. 6(6%) isolates were negative for both genes. Conclusion: Multidrug resistance is a threat to mankind and this combination of Ceftazidime-Avibactam with Aztreonam will help in combating this problem.