Programmpunkt

14:00

Titel: Sepsis caused by enterobacteria: application of MALDI-TOF MS for the rapid detection of ESβL/AmpC and carbapenemases
ID: 51/KMV
Art: Abstractautor
Session: Workshop 10
News from Microbial Detection, Identification, Antimicrobial Susceptibility Testing and Quality Management (StAG DV, FG DKM)

Referent: Miriam Cordovana (Bologna/IT)


Abstract - Text

Question

Enterobacteria are common causative agents of sepsis. β-lactam antibiotics are widely used in empiric therapy, but the spread of cephalosporinase- (ESβL, AmpC) and carbapenemase-producers threats the effectiveness of the treatment. Early detection is crucial for the clinical outcome. Laboratory methods currently available are either costly, or slow, and not applicable directly to positive blood cultures.

In this study we developed a"full MALDI based" approach for the rapid detection of cephalosporinase- and carbapenemase-producing enterobacteria directly from positive blood culture bottles, applying a combination of the most recent applications of the MALDI Biotyper system (Bruker Daltonik),species identification, subtyping for KPC-producing Klebsiella pneumoniae, followed by the evaluation of the carbapenemase- and cephalosporinase-production by hydrolysis assays.

Methods

N=92 blood cultures positive for enterobacteria (different genera and species) were included. The bacterial pellet obtained by the Sepsityper kit was used for the species identification, and for the simultaneous subtyping of KPC-producing K. pneumoniae by the MALDI Biotyper system. The residual pellet was used to investigate the carbapenemase- and cephalosporinase production by MBT STAR-Carba and MBT STAR-Cepha hydrolysis assays. The results of the new approach were compared with phenotypical reference tests (synergy test with inhibitors).

Results

92/92 isolates were identified at species level at high confidence level, 11/12 (91.3%) K. pneumoniae KPC+ strains were detected by MALDI subtyping.

STAR-Carba assay resulted positive for 16/16 carbapenemase-producing (n=12 K. pneumoniae KPC+, n=1 E. coli KPC+, n=3 K. pneumoniae MβL+), and negative for the remaining n=76 strains.

STAR-Cepha assay resulted positive for 16/16 ESβL-producing strains, 3/3 AmpC-producing strains, and for all the carbapenemase-producers but 1 K. pneumoniae MβL+, but negative for the remaining n=57 strains (wild-type, penicillinase- or constitutive AmpCs-producers).

Conclusions

The "full MALDI based" approach proved to be reliable and accurate to detect the most relevant enterobacterial resistances against β-lactam antibiotics. Moreover it is very rapid, enabling to deliver a conclusive result after 30 min-2 h starting from the positive blood culture bottle. The ease of use and the analysis of all assays on the same platform make this approach suitable for the implementation into routine workflow.