Evaluation of the Minitek Gram-Positive Set for identification of streptococci isolated from bovine mammary glands

Discrimination of major and minor streptococci incriminated in bovine mastitis by MALDI-TOF MS fingerprinting and 16S rRNA gene sequencing

The current work investigated the discriminatory potential of MALDI-TOF MS fingerprinting towards most-relevant major (Streptococcus agalactiae, S. dysgalactiae, S. uberis) and minor (S. canis, S. parauberis, S. salivarius, S. equinus and S. gallolyticus) streptococci involved in bovine mastitis (BM), in comparison to 16S rRNA gene sequencing (GS)-based identification. The MALDI-TOF MS-generated spectral fingerprints were recruited for eliciting a detailed proteomic map that demonstrated clear variability for inter- and intra-species-specific biomarkers. Besides, a phyloproteomic dendrogram was evolved and comparatively analyzed against the phylogenetic one obtained from 16S rRNA GS in order to assess the differentiation of streptococci of bovine origin based on variability of protein fingerprints versus the variation of 16S rRNA gene homology. Results showed that the discrimination of BM-implicated streptococci can be obtained by both approaches; however MALDI-TOF MS was superior, achieving more variability at both intra- and sub-species levels. MALDI-TOF MS spectral analytics revealed that Streptococcus spp. exhibited three genus-specific biomarkers (peaks with m/z values at 2112, 4452 and 5955) and all streptococci exhibited spectral variability at both species and subspecies levels. Remarkably, MALDI-TOF MS fingerprinting was found to be at least as robust as 16S rRNA GS-based identification, allowing much cheaper and faster analysis, and additionally exhibiting high reliability for characterization of BM-implicated streptococci, thus proving to be a powerful tool that can be used independently within dairy diagnostics.

Antibacterial activity of selected medicinal plants of northwest Pakistan traditionally used against mastitis in livestock

The present study aimed to investigate the efficacy of traditionally used anti-mastitis plants (Allium sativum, Bunium persicum, Oryza sativa and Triticum aestivum) in northwest Pakistan against bacterial pathogens. Selected plants were phytochemically screened for Alkaloids, Flavonoids, and Saponins and checked for in vitro antibacterial activity at concentration of 50 mg/ml against S. aureus, E. coli and K. pneumoniae by agar well diffusion method. Minimum inhibitory concentration and minimum bactericidal concentration was determined against multidrug resistant bacteria using tube dilution method. All extracts were found to significantly inhibit (p < 0.01, p < 0.05) the activity against bacterial strains examined. Among phytochemicals, alkaloids of all tested antimastitis plants produced significantly higher inhibition zones against bacteria. The minimum inhibitory concentration and minimum bactericidal concentration of phytochemicals and crude methanolic extracts against tested bacterial strains ranged between 12.5–50 mg/ml and 25–50 mg/ml, respectively. Medicinal plants traditionally used against mastitis are therapeutically active against bacterial pathogens. A. sativum and B. persicum were found to be potential candidate species for the development of novel veterinary drugs with low cost and fewer side effects.

Conventional Identification of Streptococcus uberis Isolated from Bovine Mastitis in Argentinean Dairy Herds

The objective of this study was to evaluate a conventional scheme for identifying Streptococcus uberis strains isolated from bovine mastitis. Seventy-five gram-positive, catalase-negative cocci were collected from cows with mastitis from 19 dairy herds located in the east-central region of Argentina. Five American Type Culture Collection strains and bovine isolates were identified by the API 20 Strep system and by restriction fragment length polymorphism analysis of 16S rDNA. A conventional scheme based on 11 biochemical tests was selected for identification of Strep. uberis strains: the Christie-Atkins-Munch-Petersen reaction; hydrolysis of Arg, esculin, and sodium hippurate; growth in inulin, mannitol, raffinose, salicin, and sorbitol; and growth at 45 degrees C and in 6.5% NaCl. Reference strains and 25 bovine isolates were classified accurately to the species level by the conventional scheme in a blind assay. Each reference strain and each bovine isolate were identified as belonging to the same species following these 3 methods. The remaining 50 isolates identified as Strep. uberis by the API 20 Strep system and 16S rDNA RFLP were assayed by the conventional scheme. This scheme correctly identified 47 (94%) of 50 isolates as Strep. uberis by comparing their biochemical profile with that of the reference strain. Three (6%) of the 50 isolates were classified as Strep. uberis by the API 20 Strep system and by 16S rDNA RFLP and were identified as Enterococcus faecalis by the conventional scheme. Thirty percent of the Strep. uberis strains showed biochemical profiles identical to the Strep. uberis American Type Culture Collection 27958 strain. Seventy percent of the Strep. uberis strains demonstrated variability compared with the reference strain, resulting in 19 different biochemical profiles. The conventional scheme proposed in this study resulted in a relatively low number of misidentifications and could biochemically identify not only typical, but also atypical Strep. uberis strains. This conventional scheme can be considered an adequate method for identifying Strep. uberis strains isolated from bovine mastitis because of its affordable cost in developing countries, and it may contribute to determining the frequency of isolation of Strep. uberis strains in Argentinean dairy herds.

Development of a rapid and sensitive test for identification of major pathogens in bovine mastitis by PCR

Bovine mastitis is the most important source of loss for the dairy industry. A rapid and specific test for the detection of the main pathogens of bovine mastitis is not actually available. Molecular probes reacting in PCR with bacterial DNA from bovine milk, providing direct and rapid detection of Escherichia coli, Staphylococcus aureus, Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus parauberis, and Streptococcus uberis, have been developed. Two sets of specific primers were designed for each of these microorganisms and appeared to discriminate close phylogenic bacterial species (e.g., S. agalactiae and S. dysgalactiae). In addition, two sets of universal primers were designed to react as positive controls with all major pathogens of bovine mastitis. The sensitivities of the test using S. aureus DNA extracted from milk with and without a pre-PCR enzymatic lysis step of bacterial cells were compared. The detection limit of the assay was 3.125 x 10(2) CFU/ml of milk when S. aureus DNA was extracted with the pre-PCR enzymatic step compared to 5 x 10(3) CFU/ml of milk in the absence of the pre-PCR enzymatic step. This latter threshold of sensitivity is still compatible with its use as an efficient tool of diagnosis in bovine mastitis, allowing the elimination of expensive reagents. The two PCR tests avoid cumbersome and lengthy cultivation steps, can be performed within hours, and are sensitive, specific, and reliable for the direct detection in milk of the six most prevalent bacteria causing bovine mastitis.

Use of enzyme tests in characterization and identification of aerobic and facultatively anaerobic gram-positive cocci

The contribution of enzyme tests to the accurate and rapid routine identification of gram-positive cocci is introduced. The current taxonomy of the genera of aerobic and facultatively anaerobic cocci based on genotypic and phenotypic characterization is reviewed. The clinical and economic importance of members of these taxa is briefly summarized. Tables summarizing test schemes and kits available for the identification of staphylococci, enterococci, and streptococci on the basis of general requirements, number of tests, number of taxa, test classes, and completion times are discussed. Enzyme tests included in each scheme are compared on the basis of their synthetic moiety. The current understanding of the activity of enzymes important for classification and identification of the major groups, methods of testing, and relevance to the ease and speed of identification are reviewed. Publications describing the use of different identification kits are listed, and overall identification successes and problems are discussed. The relationships between the results of conventional biochemical and rapid enzyme tests are described and considered. The use of synthetic substrates for the detection of glycosidases and peptidases is reviewed, and the advantages of fluorogenic synthetic moieties are discussed. The relevance of enzyme tests to accurate and meaningful rapid routine identification is discussed.

Identification of veterinary pathogens by use of commercial identification systems and new trends in antimicrobial susceptibility testing of veterinary pathogens

Veterinary diagnostic microbiology is a unique specialty within microbiology. Although isolation and identification techniques are similar to those used for human pathogens, many veterinary pathogens require unique cultivation or identification procedures. Commercial identification systems provide rapid, accurate identification of human pathogens. However, the accuracy of these systems with veterinary pathogens varies widely depending on the bacterial species and the host animal from which it was isolated. Increased numbers of veterinary strains or species in the data bases of the various systems would improve their accuracy. Current procedures and interpretive criteria used for antimicrobial susceptibility testing of veterinary pathogens are based on guidelines used for human pathogens. The validity of these guidelines for use with veterinary pathogens has not been established. As with fastidious human pathogens, standardized methodologies and quality control isolates are needed for tests of organisms such as Actinobacillus pleuropneumoniae and Haemophilus somnus. Furthermore, interpretive criteria for veterinary antimicrobial agents based on the MIC for veterinary pathogens, the pharmacokinetics of the antimicrobial agent in the host animal, and in vivo efficacy of the antimicrobial agent are needed. This article reviews both the commercial identification systems evaluated with veterinary pathogens and current methods for performing and interpreting antimicrobial susceptibility tests with veterinary pathogens. Recommendations for future improvements in both areas are discussed.

Evaluation of the Sceptor system for identification of bacteria of veterinary origin

The Sceptor system (Becton Dickinson Diagnostic Instrument Systems, Towson Md.) was assessed for its ability to identify veterinary clinical isolates. A total of 605 bacteria, including 315 isolates of the family Enterobacteriaceae, 191 gram-negative nonenteric bacteria, and 99 gram-positive bacteria, were tested. Overall, 534 (88.3%) were correctly identified, 28 (4.6%) were not identified, 12 (2.0%) were incorrectly identified at the genus levels, and 32 (5.3%) were incorrectly identified at the species level. The Sceptor system correctly identified 292 (92.7%) isolates of Enterobacteriaceae, 165 (86.4%) gram-negative nonenteric bacteria, and 77 (77.8%) gram-positive bacteria. One hundred thirty organisms not contained in the data base were tested with the Sceptor system to assess the possibility of expanding the data base. The Sceptor system was an acceptable method for the identification of isolates of Enterobacteriaceae but not gram-negative nonenteric and gram-positive bacteria of animal origin. Development of a veterinary isolate-specific data base would improve the utility of the Sceptor system in veterinary diagnostic bacteriology.

Evaluation of the Rapid Strep system for identification of gram-positive, catalase-negative cocci isolated from bovine intramammary infections

The Rapid Strep system (Analytab Products, Plainview, NY) was used to identify 199 gram-positive, catalase-negative cocci isolated from bovine intramammary infections. The system accurately identified 88.4% of isolates. The system identified 100% of 46 Streptococcus agalactiae, 100% of 48 Streptococcus dysgalactiae, 54.5% of 11 Streptococcus equinus, and 96.2% of 53 Streptococcus uberis isolates. Enterococcus spp. were identified correctly 83.3% of the time. One of 4 Streptococcus saccharolyticus strains was identified as Streptococcus bovis, the previous classification for this organism, and 8 Streptococcus equi ssp. equi strains were misidentified as Streptococcus dysgalactiae. The Rapid Strep system was determined to be an acceptable alternative to conventional methods for identification of gram-positive, catalase-negative cocci isolated from bovine intramammary infections.