M.-F. Prère

Performances of the Vitek MS Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry System for Rapid Identification of Bacteria in Routine Clinical Microbiology

ABSTRACT Rapid and cost-effective matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS)-based systems will replace conventional phenotypic methods for routine identification of bacteria. We report here the first evaluation of the new MALDI-TOF MS-based Vitek MS system in a large clinical microbiology laboratory. This system uses an original spectrum classifier algorithm and a specific database designed for the identification of clinically relevant species. We have tested 767 routine clinical isolates representative of 50 genera and 124 species. Vitek MS-based identifications were performed by means of a single deposit on a MALDI disposable target without any prior extraction step and compared with reference identifications obtained mainly with the VITEK2 phenotypic system; if the identifications were discordant, molecular techniques provided reference identifications. The Vitek MS system provided 96.2% correct identifications to the species level (86.7%), to the genus level (8.2%), or within a range of species belonging to different genera (1.3%). Conversely, 1.3% of isolates were misidentified and 2.5% were unidentified, partly because the species was not included in the database; a second deposit provided a successful identification for 0.8% of isolates unidentified with the first deposit. The Vitek MS system is a simple, convenient, and accurate method for routine bacterial identification with a single deposit, considering the high bacterial diversity studied and as evidenced by the low prevalence of species without correct identification. In addition to a second deposit in uncommon cases, expanding the spectral database is expected to further enhance performances.

Identification of Clinical Streptococcus pneumoniae Isolates among other Alpha and Nonhemolytic Streptococci by Use of the Vitek MS Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry System

ABSTRACT Discrimination between Streptococcus pneumoniae and its close relatives of the viridans group is a common difficulty in matrix-assisted laser desorption ionization–time of flight (MALDI-TOF) mass spectrometry-based identification. In the present study, the performances of the Vitek MS MALDI-TOF mass spectrometry system were assessed using 334 pneumococci, 166 other S. mitis group streptococci, 184 non-S. mitis group streptococci, and 19 related alpha- and nonhemolytic aerobic Gram-positive catalase-negative coccal isolates. Pneumococci had been identified by means of optochin susceptibility and bile solubility or serotyping, and other isolates mainly by use of RapidID32 Strep strips. In case of discordant or low-discrimination results, genotypic methods were used. The sensitivity of the Vitek MS for the identification of S. pneumoniae was 99.1%, since only three bile-insoluble isolates were misidentified as Streptococcus mitis/Streptococcus oralis. Conversely, two optochin-resistant pneumococci were correctly identified (specificity, 100%). Three Streptococcus pseudopneumoniae isolates were also correctly identified. Among nonpneumococcal isolates, 90.8% (n = 335) were correctly identified to the species or subspecies level and 2.4% (n = 9) at the group level. For the remaining 25 isolates, the Vitek MS proposed a bacterial species included in the list of possible species suggested by genotypic methods, except for 4 isolates which were not identified due to the absence of the species in the database. According to our study, the Vitek MS displays performance similar to that of the optochin susceptibility test for routine identification of pneumococcal isolates. Moreover, the Vitek MS is efficient for the identification of other viridans group streptococci and related isolates, provided that the species are included in the database.

Rapid molecular genetic assay for direct identification of Bordetella from patients specimens.

Biological diagnosis of whooping cough is increasingly necessary to confirm respiratory tract infection. Indeed, clinical symptoms are variable especially in adolescents and adults who contaminate newborns too young to be vaccinated. The PCR assay was proven highly sensitive for the diagnosis of pertussis. In this study, we reported the use of a new test (GenoQuick Bordetella [GQB], Hain Life Science, Germany) which permits the fast molecular genetic identification of Bordetella pertussis and parapertussis directly from patients specimens, i.e. swabs from nose or throat. The test was performed over a three months period on 40 specimens from patients (1 month to 65 years old), most of them were young children admitted in paediatric emergency with paroxysmal cough or prolonged cough.

Evaluation of an immunochromatographic assay for detection of PBP2a on non-Staphylococcus aureus clinical isolates.

We evaluated the immunochromatographic assay PBP2a Culture Colony Test (Alere™) on 50 samples of methicillin resistant and sensitive non-Staphylococcus aureus isolates belonging to ten species. Because it is rapid and reliable, this test should be advantageous as routine test in place of mecA/C PCR.

Révision de la prévalence des souches afa+ dans les Escherichia coli responsables de pyélonéphrites aiguës de l’enfant

Two hundred E. coli strains isolated from children with pyelonephritis were investigated for the presence of six virulence factors. The used primers amplified adhesin pap and sfa, toxin haemolysin (hly) and cytotoxic necrotizing factor 1 (cnf1) and aerobactin (aer). For afimbrial adhesin, the previously used set of primers could not allow to detect the newly reported afa operons (Le Bouguenec et al., 2001). With a new set of primers specific for the afa operon family the prevalence of afa+ strains increased from 3.5% to 13.5%. Combinations of three or more factors in a same strain were found in 48.5%. Thirty two different urovirulent genotypes were observed; two strains contained the six studied factors.

Évaluation de trois tests de diagnostic rapide de Campylobacter jejuni et coli à partir d’échantillons fécaux

Biological diagnosis of campylobacteriosis is increasingly necessary to confirm gastroenteritis infection. In this study, we reported the comparison of two new immunoenzymatic tests Ridascreen Campylobacter (r-biopharm(®)), premier Campy (Méridian(®)), and one immunochromatographic test, Immunocard Stat !Campy (Méridian(®)) which allow the fast detection of C. jejuni and C. coli directly from stool specimens, and culture on selective medium. The study was performed on 30 specimens from children. The three tests had the same performance. The ImmunoCard Stat !Campy could be an advantageous alternative to conventional culture.

blaNDM-1-positive Citrobacter sedlakii: emergence after horizontal gene transfer from Klebsiella pneumoniae in the human intestinal tract.

Since the first reports of bacteria producing New Delhi metallo-lactamase (NDM) [1], NDM-producing isolates have been found ore and more frequently among various Enterobacteriaceae in any countries throughout the world [2]. Klebsiella pneumoniae nd Escherichia coli have been described as the most frequent pecies possessing NDM-mediated resistance [3]. In June 2014, a 14-year-old French boy was admitted to he resuscitation unit of Toulouse Hospital, France, with multile severe traumatic injuries following an accident on a public ighway. Although no history of infection or of living outside rance was known, routine surveillance for carriage of multiresisant bacteria was performed at admission. A faecal sample was creened for extended-spectrum -lactamase (ESBL)-producing nd carbapenem-resistant Enterobacteriaceae using a panel of hromogenic agar plates (chromID®; bioMérieux, Marcy-l’Étoile, rance). The entire search was negative on the first sample. The atient received empirical therapy combining ceftriaxone, van-