Table 3.
Categorization of carbapenem susceptibility phenotypes.
| Category | Carbapenem susceptibility phenotypes | MHT (E. coli) |
MHT-PAO1 | PCR-genotyping | Implication | Examples |
|---|---|---|---|---|---|---|
| I | S | – | – | + | The carbapenemase gene detectable by genotyping does not produce carbapenemase | 14 carbapenem sensitive A. baumannii strains harboring the blaOXA-51 like gene |
| II | R | – | – | – | Carbapenem resistance not due to carbapenemase | 21 carbapenem resistant P. aeruginosa strains |
| III | R | +/– | + | – | Carbapenem resistance due to a combination of resistance mechanisms including an unknown carbapenemase or overexpression of AmpC | Seven P. aeruginosa strains |
| IV | R | + | + | + | Carbapenem resistance due to carbapenemase encoded by the gene detectable by genotyping | Various P. aeruginosa and A. baumannii strains |
| V | R | – | + | + | Carbapenem resistance due to a combination of resistance mechanisms including a weakly detected carbapenemase | P. otitidis and A. baumannii strains with a meropenem MIC ≥32 μg/ml |
| VI | I | – | + | + | Carbapenem resistance due to a weakly detected carbapenemase encoded by the gene detectable by genotyping | Three A. baumannii strains harboring the ISAba1+ blaOXA-51like elements |
Categorization according to results of the two-tiered MHT tests and genotyping of carbapenemase genes. S, carbapenem sensitive; R, carbapenem resistant; I, intermediate or low level carbapenem resistance.