TABLE 1.
Isolates tested and Carba NP resultsa
| Group | No. | Species | Carbapenemase gene (additional β-lactamase gene) | Carba NP test result |
Rate of hydrolysis of imipenem measured UV-spectrophotometricallyb | |
|---|---|---|---|---|---|---|
| No antibiotic | IPM + Zn2+ | |||||
| Carbapenem nonsusceptible | Pseudomonas aeruginosa (n = 51) | Not found | − | − | Negative | |
| Enterobacteriaceae (n = 46) | Not found (various) | − | − | Negative | ||
| Imipenem hydrolysis positive/ambiguous (spectrophotometry method) | Enterobacteriaceae (n = 14) | Not found | − | − | Varying positive | |
| Metallo-β-lactamases | 2,174 | P. aeruginosa | IMP | − | + | Moderate |
| 2,186 | P. aeruginosa | IMP | − | + | Moderate | |
| 2,219 | P. aeruginosa | IMP | − | + | Moderate | |
| 2,269 | P. aeruginosa | IMP | − | + | Moderate | |
| 2,342 | P. aeruginosa | IMP | − | + | Moderate | |
| 2,422 | P. aeruginosa | IMP | − | + | Moderate | |
| 1,648 | P. aeruginosa | IMP-15 | − | + | Moderate | |
| 1,871 | P. aeruginosa | IMP-15 | − | + | Moderate | |
| 2,003 | P. aeruginosa | IMP-15 | − | + | Moderate | |
| 2,310 | P. aeruginosa | IMP-15 | − | + | Moderate | |
| 3,413 | E. coli | NDM | − | + | High | |
| 2,347 | E. coli | NDM (CTX-M, TEM) | − | + | High | |
| 2,491 | E. coli | NDM (CTX-M, TEM) | − | + | High | |
| 3,582 | E. coli | NDM (CTX-M, TEM, CMY) | − | + | High | |
| 2,775 | E. coli | NDM (TEM, CIT) | − | + | High | |
| 4,049 | E. coli | NDM (CIT) | − | + | ND | |
| 4,091 | E. coli | NDM (TEM, SHV) | − | + | High | |
| 3,583 | K. pneumoniae | NDM (CTX-M, TEM, CMY) | − | + | High | |
| 2,050 | K. pneumoniae | NDM-1 (CTX-M) | − | + | High | |
| 4,047 | K. pneumoniae | NDM (CTX-M, CIT, DHA, TEM) | − | + | High | |
| 2,098 | K. pneumoniae | VIM | − | + | High | |
| 2,187 | K. pneumoniae | VIM | − | + | ND | |
| 2,398 | K. pneumoniae | VIM | − | + | High | |
| 2,089 | K. pneumoniae | VIM | − | + | Moderate | |
| 2,126 | P. aeruginosa | VIM | − | + | Moderate | |
| 2,203 | P. aeruginosa | VIM | − | + | ND | |
| 2,506 | P. aeruginosa | VIM | − | + | Moderate | |
| 3,327 | K. oxytoca | VIM (ACC) | − | + | High | |
| 3,127 | A. baumannii | VIM, OXA-58 | − | + | High | |
| 1,653 | P. aeruginosa | VIM-2 | − | + | ND | |
| 1,872 | P. aeruginosa | VIM-2 | − | + | Moderate | |
| Class A carbapenemase | 3,697 | E. cloacae | GES-5 | − | − | Low |
| 2,049 | K. pneumoniae | GES-14 | − | − | Low | |
| 2,168 | E. cloacae | IMI-1 | − | + | Moderate | |
| 1,468 | E. cloacae | IMI-2 | − | −/+ | High | |
| 3,810 | E. cloacae | KPC | − | + | High | |
| 2,015 | K. pneumoniae | KPC (CTX-M) | − | + | High | |
| 3,523 | K. pneumoniae | KPC (CTX-M, TEM) | − | + | High | |
| 4,013 | K. pneumoniae | KPC (TEM) | − | + | High | |
| 2,801 | K. pneumoniae | KPC (TEM, CTX-M) | − | + | High | |
| 1,592 | K. pneumoniae | KPC-2 (TEM) | − | + | High | |
| 1,597 | K. pneumoniae | KPC-2 (TEM) | − | + | High | |
| 1,618 | K. pneumoniae | KPC-2 (TEM) | − | + | High | |
| 1,620 | K. pneumoniae | KPC-2 (TEM) | − | + | High | |
| 2,247 | E. cloacae | NMC-A | − | + | Moderate | |
| 2,779 | Serratia marcescens | SME | − | − | High | |
| Class D carbapenemase | 2,279 | K. pneumoniae | OXA-181 (CTX-M, TEM) | − | +/− | Moderate |
| 2,485 | K. pneumoniae | OXA-181 (CTX-M, TEM) | − | − | Moderate | |
| 3,328 | K. pneumoniae | OXA-181 (CTX-M, TEM) | − | − | Moderate | |
| 2,287 | E. coli | OXA-181 (TEM) | − | − | Moderate | |
| 2,536 | K. pneumoniae | OXA-181 (TEM, CTX-M) | − | − | Moderate | |
| 3,993 | Acinetobacter sp. | OXA-23 | − | − | Low | |
| 3,977 | E. coli | OXA-48 | − | + | High | |
| 2,350 | K. pneumoniae | OXA-48 | − | + | High | |
| 3,979 | K. pneumoniae | OXA-48 | − | + | High | |
| 2,005 | Raoultella planticola | OXA-48 | − | + | High | |
| 2,270 | E. coli | OXA-48 (CTX-M) | − | + | High | |
| 1,604 | E. coli | OXA-48 (TEM) | − | +/− | Low | |
| 2,663 | E. coli | OXA-48 (TEM, CTX-M) | − | −/+ | Moderate | |
| 2,493 | K. pneumoniae | OXA-48 (TEM-1) | − | + | High | |
| 3,728 | E. coli | OXA-48-like (CTX-M, TEM) | − | +/− | Moderate | |
a
IPM, imipenem; −, negative; +, positive; +/− and −/+, weakly positive and very weakly positive, respectively; ND, not determined.
b
The relative rates of hydrolysis were arbitrarily defined as high (all imipenem broken down by all three dilutions of bacterial lysate in less than 10 min), moderate (all imipenem broken down by all dilutions in less than 30 min), and low (imipenem not cleared completely in 30 min). Negative, drop in (lysate-plus-imipenem) OD of <0.25 to 0.3 over 30 min.