Exploring the MALDI Biotyper for the Identification of Corynebacterium pseudotuberculosis biovar Ovis and Equi.

Biochemical, serological, and molecular methods have been developed for the laboratory diagnosis of diseases caused by C. pseudotuberculosis (CP), but the identification of the pathogen and biovars differentiation may be time-consuming, expensive, and confusing compared with other bacteria. This study aimed to evaluate MALDI Biotyper and Overall Genome Relatedness Index (OGRI) analysis to optimize the identification and differentiation of biovars of C. pseudotuberculosis. Out of 230 strains isolated from several hosts and countries, 202 (87.8%) were precisely classified using MALDI Biotyper and the BioNumerics platform. The classification accuracies for the Ovis and Equi biovars were 80 (88.75%) and 82 (92.68%), respectively. When analyzing a sampling of these strains by Average Nucleotide Identity based on BLAST and TETRA analyses using genomic sequence data, it was possible to differentiate 100% of the strains in Equi and Ovis. Our data show that MALDI Biotyper and OGRI analysis help identify C. pseudotuberculosis at the species and biovar levels.

Severe outbreak of Centrocestus formosanus (Trematoda: Heterophyidae) in farm-raised ornamental platies Xiphophorus maculatus.

This report describes a severe outbreak of the gill fluke Centrocestus formosanus in farm-raised platies Xiphophorus maculatus in Brazil, with mortality rate approaching 95%. Typical clinical signs of infection were observed, with microscopic examinations of fresh gills revealing multiple cysts containing a once-folded metacercaria with an X-shaped excretory bladder. The 18S subunit of the metacercariae (BR1) was amplified by PCR, sequenced and analyzed by BLAST. Subsequent phylogenetic analyses revealed that the BR1 isolate was closely related to C. formosanus from Thailand. This is the first report of C. formosanus in ornamental fish in Brazil. Our observations suggest that platies are highly sensitive to this digenetic parasite. Controlling population densities of the parasite's intermediate host, the snail Melanoides tuberculata, would help to reduce outbreaks.

Use of MALDI-TOF Mass Spectrometry for the Fast Identification of Gram-Positive Fish Pathogens.

Gram-positive cocci, such as Streptococcus agalactiae, Lactococcus garvieae, Streptococcus iniae, and Streptococcus dysgalactiae subsp. dysgalactiae, are found throughout the world, particularly in outbreaks in farmed fish, and are thus associated with high economic losses, especially in the cultivation of Nile Tilapia. The aim of this study was to evaluate the efficacy of matrix-assisted laser desorption ionization (MALDI)-time of flight (TOF) mass spectrometry (MS) as an alternative for the diagnosis of these pathogens. One hundred and thirty-one isolates from Brazilian outbreaks assisted by the national authority were identified using a MALDI Biotyper from Bruker Daltonics. The results showed an agreement with respect to identification (Kappa = 1) between this technique and 16S ribosomal RNA gene sequencing for S. agalactiae and L. garvieae. However, for S. iniae and S. dysgalactiae subsp. dysgalactiae, perfect agreement was only achieved after the creation of a custom main spectra profile, as well as further comparisons with 16S ribosomal RNA and multilocus sequence analysis. MALDI-TOF MS was shown to be an efficient technology for the identification of these Gram-positive pathogens, yielding a quick and precise diagnosis.