Comparison of MALDI-ToF MS with the Rapidec Carba NP test for the detection of carbapenemase-producing Enterobacteriaceae.

Although carbapenemase-producing Enterobacteriaceae (CPE) have become a serious public health issue, their detection remains challenging. The aim of this study was to implement a test based on imipenem hydrolysis by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF MS), using 65 strains producing or not a carbapenemase. Then, we compared its performance to that of the Rapidec Carba NP test using 20 additional strains. The MS-based test effectively discriminated between CPE and other non-carbapenem-susceptible strains compared to the Rapidec Carba NP test (sensitivity 100% and 92%, specificity 94% and 92%, respectively). The MS-based test gave less difficulty in interpretation than the colorimetric Rapidec Carba NP test. MALDI-ToF gave a result in less than one hour and limited the use of expensive molecular assays. In conclusion, the hydrolysis test based on MALDI-ToF MS can detect clinically relevant CPE isolates in routine practice. This technology, also described to screen for carbapenem resistance in Pseudomonas aeruginosa and Acinetobacter baumannii complex strains, also seems to be interesting in routine practice for these pathogens.

Place of diagnostic tools in the identification of Anaerobiospirillum succiniciproducens bacteraemia.

Anaerobiospirillum succiniciproducens is a rare but potentially lethal pathogen. We report a case of A. succiniciproducens bloodstream infection in a 55-year-old man hospitalized for pelvic trauma. The strain was identified by 16sRNA sequencing after several failures of identification by MALDI-TOF MS. The strain was susceptible to beta-lactam antibiotics and ciprofloxacin, but resistant to macrolides and clindamycin. Identification tools must be improved to enhance our knowledge on this rare pathogen and to define optimal therapy.

Limited efficacy of nontreponemal test combined with treponemal test in the initial syphilis screening algorithm.

PURPOSE: Various syphilis screening algorithms have been proposed and are now used by many clinical laboratories following the introduction of automated treponemal tests (TTs). In France, the diagnosis of syphilis is based on a TT combined with a nontreponemal test (NTT). The objective of this study was to evaluate the diagnostic impact of NTT on initial syphilis screening at the Amiens University Hospital between January 2013 and December 2016. METHODOLOGY: Serum samples sent for syphilis testing were analysed using a treponemal enzyme immunoassay (Siemens IMMULITE 2000 Syphilis Screen) combined with a nontreponemal test. Enzyme immunoassay (EIA)-reactive and/or nontreponemal-reactive samples were titrated to endpoint using the Treponema pallidum particle agglutination test (TPHA). Complementary tests, such as line immunoassay, and medical charts were reviewed to categorize reactive samples into positive or negative syphilis contacts. RESULTS: Among 15 523 initial screening samples, 148 samples (0.95 %) were reactive with the combined TT and NTT, and 335 (2.16 %) and 66 (0.42 %) were reactive with TT or NTT only. Analysis of the 66 discordant results between TT and NTT showed that only 4 sera were reactive with a second-line TPHA, but these results were not confirmed by line immunoassay and patient characteristics. CONCLUSION: The results of this study show that the combination of NTT and TT for initial screening does not provide any diagnostic gain, but represents additional laboratory work time.

Characterization of a multidrug-resistant Klebsiella pneumoniae ST607-K25 clone responsible for a nosocomial outbreak in a neonatal intensive care unit.

PURPOSE: Multidrug-resistant Klebsiella pneumoniae strains are regularly involved in hospital outbreaks. This study describes an ESBL-producing K. pneumoniae clone (ST607-K25) responsible for a nosocomial outbreak in a neonatal intensive care unit. METHODOLOGY: Fourteen strains isolated from 13 patients were included. Antimicrobial susceptibility testing was performed by the agar diffusion method. A clonal link was first investigated by fingerprinting (ERIC-PCR and REP-PCR) then confirmed by MLST. Characterization was performed by molecular detection and identification of several drug resistance and virulence determinants. RESULTS: All strains expressed the same antibiotype, combining ESBL production, fluoroquinolones and aminoglycoside resistance, except for one which remained susceptible to fluoroquinolones. Fingerprinting methods confirmed the clonal link and MLST identified a ST607 clone. Molecular investigations revealed: (I) genes encoding for two narrow-spectrum beta-lactamases (SHV-1 and TEM-1) and an ESBL (CTX-M-15); (II) absence of any chromosomal mutation in quinolone resistance-determining- regions (QRDR) of gyrA/gyrB and parC/parE genes; (III) genes encoding for three plasmid-mediated quinolone-resistance (PMQR) determinants: oqxAB (14/14), aac(6')-Ib-cr (14/14) and qnrB (13/14); (IV) production of a K25 capsule; and (V) carriage of three genes encoding for virulence factors: mrkD (type 3 fimbriae) (14/14), ybts (yersiniabactin) (12/14) and entB (enterobactin) (14/14). CONCLUSION: We described a multidrug-resistant Kp ST607 clone responsible for a nosocomial outbreak in vulnerable and premature newborns. Molecular investigations allowed us to identify several resistance factors responsible for ESBL production (CTX-M-15) and quinolone resistance (three PMQR determinants). The detection of a gene (ybtS) belonging to the high-pathogenicity island yersiniabactin could partly explain its high colonization and diffusion potential.