Identification of Diverse Integron and Plasmid Structures Carrying a Novel Carbapenemase Among Pseudomonas Species.

A novel carbapenem-hydrolyzing beta-lactamase, called IMP-63, was identified in three clonally distinct strains of Pseudomonas aeruginosa and two strains of Pseudomonas putida isolated within a 4 year timeframe in three French hospitals. The bla IMP-63 gene that encodes this carbapenemase turned out to be located in the variable region of four integrons (In1297, In1574, In1573, and In1572) and to coexist with novel or rare gene cassettes (fosM, gcu170, gcuF1) and insertion elements (ISPsp7v, ISPa16v). All these integrons except one (In1574) were flanked by a copy of insertion sequence ISPa17 next to the orf6 putative gene, and were carried by non-conjugative plasmids (pNECK1, pROUSS1, pROUSS2, pROUE1). These plasmids exhibit unique modular structures and partial sequence homologies with plasmids previously identified in various non-fermenting environmental Gram-negative species. Lines of evidence suggest that ISPa17 promoted en bloc the transposition of IMP-63-encoding integrons on these different plasmids. As demonstrated by genotyping experiments, isolates of P. aeruginosa harboring the 28.9-kb plasmid pNECK1 and belonging to international "high-risk" clone ST308 were responsible for an outbreak in one hospital. Collectively, these data provide an insight into the complex and unpredictable routes of diffusion of some resistance determinants, here bla IMP-63, among Pseudomonas species.

Rapid identification of Candida sp. by MALDI-TOF mass spectrometry subsequent to short-term incubation on a solid medium.

Rapid identification of Candida species is important for appropriate antifungal therapy of fungemia. The matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) system is a useful tool to identify bacteria and yeasts. In this study, we evaluated the feasibility of identifying yeasts after a short-term incubation on a solid medium. We tested 24 strains of eight Candida species. Blood culture bottles were spiked with a calibrated suspension of each Candida strain. Three different culture media, two types of blood culture bottles and three different incubation time points were tested. A multivariable random-effects logistic regression analysis was performed for determining factors independently associated with a successful MALDI-TOF MS identification. One-hundred and thirty-one out of 432 MALDI-TOF MS analyses (30%) exhibited a score ≥ 1.7. The performance of the technique varied across Candida species. Factors associated with a successful identification were the use of a chromogenic Candida medium and the time points 4 and 5 h. Using the factors 'chromogenic Candida medium' and time point 5 h the global performance of identification reached 60% and a mean MALDI-TOF score of 1.78. Identifying yeasts after a short-term incubation on a solid medium seems possible, especially when using a chromogenic Candida medium and respecting at least 5 h of incubation. This assay was a first step and needs to be completed using more strains, various chromogenic Candida medium and maybe also testing a longer culture time such as 6 h.