Evaluation of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for species identification of bacteria of genera Arcanobacterium and Trueperella

In the present study matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) was evaluated for species identification of 98 bacteria previously classified phenotypically and genotypically to genera Arcanobacterium and Trueperella. Species identification was carried out by comparing the main spectra of each strain with the main spectra of reference strains of both genera and 3740 database entries included in the MALDI Biotyper 2.0 software package (Bruker Daltonik GmbH, Bremen, Germany). MALDI-TOF MS correctly identified (log (score) values ≥ 2.0) all investigated strains of the species A. (T.) bialowiezense (n=3), A. (T.) bonasi (n=7), A. haemolyticum (n=10), A. pluranimalium (n=1) and A. (T.) pyogenes (n=77). According to the present results MALDI-TOF MS had a comparable discriminating power than previously conducted tests on DNA level. Further studies with strains isolated from human infections would show the robustness of MALDI-TOF MS for identification of bacteria of these genera.     

Identification of Arcanobacterium (Trueperella) abortisuis, a novel species of veterinary importance, by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS)

In the present study A. (T.) abortisuis isolated from pigs and bovines could be reliably identified by determination of phenotypic properties, genotypically by polymerase chain reaction with the help of A. (T.) abortisuis 16s-23S rDNA intergenic spacer region specific oligonucleotide primer and by Matrix-Assisted Laser Desorption Ionization-Time Of Flight mass spectrometry (MALDI-TOF MS). The latter appeared to be a promising tool for fast and cost effective identification of this species and might help to elucidate the role A. (T.) abortisuis plays in infections of pigs, bovines, possibly other animals or humans.     

Identification of Arcanobacterium pluranimalium by matrix-assisted laser desorption ionization-time of flight mass spectrometry and,as novel target,by sequencing pluranimaliumlysin encoding gene pla

In the present study 13 Arcanobacterium pluranimalium strains isolated from various animal origin could successfully be identified phenotypically by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and genotypically by sequencing 16S rDNA and the pluranimaliumlysin encoding gene pla. The detection of mass spectra by MALDI-TOF MS and the novel genotypic approach using gene pla might help to identify A. pluranimalium in future and might elucidate the role this species plays in infections of animals.     

Identification through MALDI-TOF mass spectrometry and antimicrobial susceptibility profiling of bacterial pathogens isolated from sow urinary tract infection

Background: Urinary tract infection (UTI) is a common disease in sows due to intensification of pig production. Despite direct economic losses, UTI prevalence and respective microbial identification are still poorly studied.

Objective: The aims of this study were to identify the causative agents of UTI in sows through MALDI-TOF MS and to characterize their antimicrobial resistance profiles.

Materials and Methods: Urine samples from 300 sows of three herds from São Paulo State (Brazil) were screened for UTI; suggestive samples were submitted to bacterial isolation. Species identification was performed by MALDI-TOF MS and susceptibility profiles were determined using disc diffusion method.

Results: 128 samples suggestive of UTI were analyzed; 48% of the animals presented UTI caused by a single pathogen, while the remaining 52% presented mixed infection. Escherichia coli stood out with the highest frequency among both single and mixed infections. The Gram-positive were exclusively associated with 27% of single infections. The mixed infections were further classified into 49 profiles. The high frequency of multiresistant profiles stood out for most of the studied isolates.

Conclusions: MALDI-TOF MS enabled the identification of rare pathogens related to UTI which may represent higher risk for porcine health, especially considering high frequency of multiresistant profiles.     

Analysis of the bovine plasma proteome by matrix-assisted laser desorption/ionisation time-of-flight tandem mass spectrometry

In this study, the bovine plasma proteome was analysed using a three step protocol: (1) plasma was treated with a combinatorial peptide ligand library (CPLL) to assimilate the differences in concentrations of different proteins in raw plasma; (2) CPLL-treated material was fractionated by three standard electrophoretic separation techniques, and (3) samples were analysed by nano-liquid chromatography (nLC) matrix-assisted laser desorption/ionisation (MALDI) time-of-flight tandem (TOF/TOF) mass spectrometry. The efficiencies of three fractionation protocols for plasma proteome analysis were compared.After size fractionation by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE), resolution of proteins was better and yields of identified proteins were higher than after charge-based fractionation by preparative gel-free isoelectric focussing. For proteins with isoelectric points >6 and molecular weights ?63 kDa, the best results were obtained with a ‘shotgun’ approach, in which the CPLL-treated plasma was digested and the peptides, rather than the proteins, were fractionated by gel-free isoelectric focussing. However, the three fractionation techniques were largely complementary, since only about one-third of the proteome was identified by each approach.