Table 3.
Comparison of common antimicrobial resistance mechanisms in KPC-Kp resistant to CAZ–AVI and/or IMI–REL
| Strains | Mutationa | Increased expression of blaKPCb | Efflux pump inhibitor testsc | ||||
|---|---|---|---|---|---|---|---|
| KPC | OmpK35 | OmpK36 | PBP2 | PBP3 | |||
| Only CAZ–AVI-resistant (n = 16) |
D179Y (n = 3;729, CR059, CR063) A172V (n = 1;ZSS072) |
– | – | – | – | n = 10 (CR059, CR063, ZSS072, ZSS048, 617, 430, 794, A398, A206, 795) | n = 2 (794,795) |
| CAZ–AVI- and IMI–REL-resistant (n = 5) | – | – |
Q296*(n = 1;A125) K196E(n = 1;ZSS129) S125fs(n = 1;A301) Lack(n = 1;744) |
– | D343N(n = 1;ZSS129) | n = 4 (CR067, ZSS129, A125, A301) | n = 2 (ZSS129,744) |
| Only IMI–REL-resistant (n = 1) | – | Lack(n = 1;478) | – | – | n = 0 | n = 0 | |
a”–” indicates that no mutations were detected in KPC or PBP2/3 and no additional mutations were detected in OmpK35/36, except for a common mutation (a premature stop codon at amino acid position 63 in OmpK35, 134 to 135 GD insertion in OmpK36)
bIndependent two-sample t-tests were conducted to determine the differences in blaKPC expression between resistant and sensitive strains, and p < 0.05 considered to be statistically significant
cMICs of CAZ–AVI and IMI–REL in combination with CCCP at a concentration of 10 mg/L were determined. A four-fold decrease in the MIC after the addition of CCCP was considered significant