Short communication, Note

Composition of raw cow’s milk microbiota and identification of enterococci by MALDI-TOF MS - short communication.

Vesna Dobranić ; Department of Hygiene, Technology and Food Safety, Faculty of Veterinary Medicine, University of Zagreb, Zagreb, Croatia
Snježana Kazazić ; Laboratory for Chemical Kinetics and Atmospheric Chemistry, Division of Physical Chemistry, Ruđer Bošković Institute, Zagreb, Croatia
Ivana Filipović ; Department of Hygiene, Technology and Food Safety, Faculty of Veterinary Medicine, University of Zagreb, Zagreb, Croatia
Nataša Mikulec ; Department of Dairy Science, Faculty of Agriculture, University of Zagreb, Zagreb, Croatia
Nevijo Zdolec orcid.org/0000-0001-7413-8115 ; Department of Hygiene, Technology and Food Safety, Faculty of Veterinary Medicine, University of Zagreb, Zagreb, Croatia

Abstract

Raw milk consumption could present a potential risk for public health due to the presence of foodborne pathogens and spoilage bacteria. In this research, microbiota or raw cow’s milk was studied with particular reference to the presence of enterococcal opportunistic pathogens. Total viable count, psychrophilic bacteria, lactic acid bacteria, staphylococci, Escherichia coli, enterococci, enterobacteria, Listeria spp. and sulfitereducing clostridia were evaluated using standard culture methods. Milk samples originated from healthy (n = 17) and antibiotic-treated cow’s udders (n = 19). Presumptive enterococci (n = 43) were randomly selected from chromogenic media and subjected to phenotypic identification by API 20 Strep, followed by Matrix- Assisted Laser Desorption Ionization - Time of Flight Mass Spectometry (MALDI-TOF MS). Statistically significant differences (P<0.05) regarding the udder status were found in the total viable count and lactic acid bacteria. MALDI-TOF MS determination showed 100% concordance with API 20 Strep in the identification of Enterococcus faecalis. Strains determined to the genus level only, or non-determined strains by API 20 Strep were successfully identified using MALDI-TOF MS to the strain level as E. faecalis, E. faecium and E. durans. Results showed that MALDI-TOF MS could be applied as a reliable method in the routine identification of enterococcal species from raw milk.

Keywords

milk; enterococci; MALDI-TOF MS

Hrčak ID:

166060

URI

https://hrcak.srce.hr/166060

Publication date:

12.8.2016.

Article data in other languages: croatian

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