Phenotypic and genotypic identification of streptococci and related bacteria isolated from bovine intramammary infections.

Raemy, Andreas; Meylan, Mireille; Casati, Simona; Gaia, Valeria; Berchtold, Beat; Boss, Renate; Wyder, Anja Barbara; Graber, Hans Ulrich (2013). Phenotypic and genotypic identification of streptococci and related bacteria isolated from bovine intramammary infections. Acta Veterinaria Scandinavica, 55(53), p. 53. BioMed Central Ltd. 10.1186/1751-0147-55-53

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BACKGROUND Streptococcus spp. and other Gram-positive, catalase-negative cocci (PNC) form a large group of microorganisms which can be found in the milk of cows with intramammary infection. The most frequently observed PNC mastitis pathogens (major pathogens) are Streptococcus uberis, Strep. dysgalactiae, and Strep. agalactiae. The remaining PNC include a few minor pathogens and a large nonpathogenic group. Improved methods are needed for the accurate identification and differentiation of PNC. A total of 151 PNC were collected from cows with intramammary infection and conclusively identified by 16S rRNA sequencing as reference method. Nine phenotypic microbiological tests (alpha-hemolysis, CAMP reaction, esculin hydrolysis, growth on kanamycin esculin azide agar and on sodium chloride agar, inulin fermentation, hippurate hydrolysis, leucine aminopeptidase and pyrrolidonyl peptidase activity), multiplex PCR for the three major pathogens (target genes for Strep. uberis, Strep. dysgalactiae and Strep. agalactiae: pauA, 16S rRNA, and sklA3, respectively), and mass spectroscopy using the matrix-assisted laser desorption ionization-time of flight (MALDI-TOF MS) were evaluated for the diagnosis and discrimination of the three clinically most relevant PNC. RESULTS The probability that a strain of Strep. uberis, Strep. dysgalactiae and Strep. agalactiae was correctly identified by combining the results of the 9 phenotypic tests was 92%, 90%, and 100%, respectively. Applying the multiplex PCR, all strains of the three major pathogens were correctly identified and no false positive results occurred. Correct identification was observed for all strains of Strep. uberis and Strep. agalactiae using MALDI-TOF MS. In the case of Strep. dysgalactiae, some variability was observed at the subspecies level, but all strains were allocated to one single cluster. CONCLUSIONS The results of the present study show that reliable identification of the clinically most relevant PNC (Strep. uberis, Strep. agalactiae and Strep. dysgalactiae) can be obtained by use of a combination of colony morphology, hemolysis type and catalase reaction, and a multiplex PCR with specific primers restricted to these 3 pathogens. The MALDI-TOF MS is a fast method that shows promising results, although identification of Strep. dysgalactiae at the subspecies level is not yet satisfactory.

Item Type:

Journal Article (Original Article)

Division/Institute:

05 Veterinary Medicine > Research Foci > Veterinary Public Health / Herd Health Management
05 Veterinary Medicine > Department of Clinical Veterinary Medicine (DKV)
05 Veterinary Medicine > Department of Clinical Veterinary Medicine (DKV) > Clinic for Ruminants

UniBE Contributor:

Raemy, Andreas; Meylan, Mireille; Berchtold, Beat; Boss, Renate; Wyder, Anja Barbara and Graber, Hans Ulrich

Subjects:

600 Technology > 630 Agriculture

ISSN:

1751-0147

Publisher:

BioMed Central Ltd.

Language:

English

Submitter:

Susanne Portner

Date Deposited:

18 Jul 2014 12:09

Last Modified:

26 Jun 2016 01:49

Publisher DOI:

10.1186/1751-0147-55-53

PubMed ID:

23866930

BORIS DOI:

10.7892/boris.45826

URI:

https://boris.unibe.ch/id/eprint/45826

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