In vitro activity of essential antimicrobial agents, including ceftazidime/avibactam, imipenem/relebactam, and cefiderocol, against carbapenem-resistant Gram-negative bacteria primarily harboring the IMP-type carbapenemase gene in the Kinki region of Japan.

OBJECTIVE

In cases of infections caused by multidrug-resistant Gram-negative bacilli (MRGNB), the efficacy of various antimicrobial agents may be limited due to antimicrobial resistance. This study evaluated the antimicrobial activity of various antimicrobials, principally novel beta-lactam beta-lactamase inhibitor combinations, against MRGNB prevalent in the Kinki region of Japan.

METHODS

A total of 207 strains were utilized in the study, encompassing 108 carbapenemase-producing Enterobacterales (CPE) strains, 9 carbapenemase-non-producing carbapenem-resistant Enterobacterales (non-CP-CRE) strains, 73 carbapenem-resistant Pseudomonas aeruginosa (CRPA) strains, and 17 carbapenem-resistant Acinetobacter spp. (CRA) strains. These strains were obtained from the Study of Bacterial Resistance in the Kinki Region of Japan. Antimicrobial susceptibility testing was assessed via broth microdilution, with MICs determined according to the Clinical and Laboratory Standards Institute standards.

RESULTS

The MIC50/MIC90 values (in μg/mL) for each antimicrobial agent were determined for the CPE, non-CP-CRE, CRPA, and CRA strains. The following agents demonstrated activity: ceftazidime/avibactam (CAZ/AVI) (16/>16, 2/8, 8/16, 16/>16), piperacillin/tazobactam (8/>64, >64/>64, 64/>64, 8/>64), ceftolozane/tazobactam (CTLZ/TAZ) (>32/>32, 16/>32, 8/>32, >32/>32), imipenem/relebactam (IPM/REL) (0.25/4, 1/2, 8/>8, >8/>8), tigecycline (≤0.5/2, 1/8, >8/>8, ≤0.5/1), colistin (1/2, 1/8, 1/1, 1/2), and cefiderocol (0.25/2, 1/16, 1/8, 0.5/32).

CONCLUSION

The MIC distributions for colistin, tigecycline, and cefiderocol were narrow across resistant strains, indicating consistent activity. Furthermore, the MIC distributions of CAZ/AVI and IPM/REL exhibited a narrow range of concentrations against non-CP-CRE and non-CP-CRPA, respectively. In contrast, CTLZ/TAZ exhibited a similarly narrow distribution against non-CP-CRPA. These findings suggest that these antimicrobials effectively treat infections caused by MRGNB.