Review of established and innovative detection methods for carbapenemase-producing Gram-negative bacteria

The minimal antibiotic options for carbapenemase-producing Gram-negative bacteria necessitate their rapid detection. A literature review of a variety of phenotypic and genotypic methods is presented. Advances in culture methods and screening media are still subject to long incubation hours. Biochemical methods have shorter turnaround times and higher sensitivities and specificities, but cannot differentiate between various types and variants. Spectrophotometric methods are cheap and efficient, but are uncommon in many clinical settings, while the MALDI-TOF MS is promising for species identification, typing and resistance gene determination. Although next generation sequencing (NGS) technologies provide a better platform to detect, type and characterize carbapenem-resistant bacteria, the different NGS platforms, the large computer memories and space needed to process and store genomic data and the nonuniformity in data analysis platforms are still a challenge. The sensitivities, specificities and turnaround times recorded in the various studies reviewed favours the use of the biochemical tests (Carba NP or Rapid Carb screen tests) for the detection of putative carbapenemase-producing isolates. MALDI-TOF MS and/or molecular methods like microarray, loop-mediated isothermal amplification and real-time multiplex PCR assays could be used for further characterization in a reference laboratory. NGS may be used for advanced epidemiological and molecular studies.