Elsevier

Anaerobe

Volume 18, Issue 1, February 2012, Pages 103-109
Anaerobe

Molecular biology, genetics and biotechnology
Lactic acid bacteria from raw milk as potentially beneficial strains to prevent bovine mastitis

https://doi.org/10.1016/j.anaerobe.2012.01.002Get rights and content

Abstract

Bovine mastitis produces a wide variety of problems in the dairy farm. The treatment of this disease is based on the use of antibiotics which are not always effective. These drugs are also responsible for the presence of residues in the milk and the increase of antibiotic-resistant strains. Probiotic products were proposed as a valid alternative to antibiotic therapies and are also useful for the prevention of infectious syndromes. With the aim of designing a probiotic product to prevent bovine mastitis, lactic acid bacteria (LAB) were isolated from foremilk samples from different dairy farms in Córdoba-Argentina. One hundred and seventeen LAB were isolated and their beneficial characteristics such as the production of inhibitory substances, surface properties and production of exopolysaccharides (EPS) were assessed. Most of them displayed low degree of hydrophobicity, autoaggregation, EPS negative phenotype and were identified as Enterococcus hirae and Pediococcus pentosaceus. Nine LAB strains inhibited three indicator bacteria. Some isolates were pre-selected and genetically identified according to the results obtained. Antibiotic resistance and virulence factors were studied for the assessment of the safety of the strains. The results obtained were compared to those reported previously from samples obtained in the North-western area of the country and some differences were found.

Introduction

BM is the most frequent disease in dairy farms and produces a great impact on dairy farming business [1]. Antibiotics are usually applied during lactation and also in dry cow therapies with the risk of antibiotic resistance and the presence of residues in the milk. Besides, treatments are not always successful [2].

An alternative therapy against infections is the administration of probiotics, defined as “live microorganisms which when administered in adequate amounts confer a health physiological benefit on the host” [3]. LAB is one of the most representative groups of prokaryotes used with this purpose and are part of the indigenous microbiota of the teat canal. They are optimal candidates to design a species-specific probiotic product to prevent BM [4], [5]. In the field of bovine health, probiotics are mainly applied to prevent gastrointestinal infections and for nutritional purposes [6], [7]. For these reasons, the objectives of the present work were to isolate and characterize the lactic acid microbiota from raw milk samples from the central region of Argentina, to pre-select some strains by their beneficial characteristics and later to perform their genetic taxonomic identification. These results were compared with those previously obtained in cows from a different ecological place (Northern Argentina).

Section snippets

Sampling

Samples were taken from 51 clinically healthy or mastitic Holstein cows, belonging to eight different dairy farms in Southern Córdoba, Argentina. Teat ends were cleaned with 70% ethanol and dried with individual paper towels. The health status of each animal was registered. Foremilk was received in sterile plastic tubes, immediately refrigerated and transported to the laboratory.

Udder health status

Udder health status was defined by clinical examination, SCC in a fluoro-opto-electronic counter (Fossomatic method)

Milk characterization

Around forty percent of the milk samples were obtained from healthy quarters (43.1%), while 39.3% from quarters with subclinical BM. A low number of samples came from quarters with clinical BM (data not shown).

Microbiological evaluation of the samples

The number of mesophilic microorganisms was lower than 100,000 CFU/ml in all the samples. LAB were isolated from thirty three of the fifty one samples examined, with a mean value of 5.62 × 102 ± 4.1 × 102 CFU/ml.

LAB isolation

Out of fifty one foremilk samples, one hundred and seventeen LAB were

Discussion

BM is one of the most common and expensive diseases in dairy farms due to the production losses, discarded milk, applied therapy, veterinary services, culling and risk of other diseases such as decrease of fertility [1], [23]. The main etiologic agents are S. aureus and coagulase-negative Staphylococcus [24], [25], [26]. There are some novel applications or alternatives to the antibiotic therapy, as the use of vaccines [27], bacteriocins and probiotics that are being currently studied [5], [28]

Conclusion

Although some differences, mainly in the diversity of the microbiota and the species isolated, were detected, the results obtained in the studies performed in LAB from the central area of Argentina support in some way those obtained previously in the North-western region. A new group of potentially probiotic strains are available after this work, selected by different criteria based on their functional properties and their safety, which will be further assayed in in vivo studies.

Acknowledgements

This work was supported by CONICET PIP 632 and ANPCYT PICT 543 grants. The results obtained are included in the project “Design of a probiotic product for bovine mastitis prevention” signed between CONICET and UNRC Res.2907.

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