Abstract
A total number of 228 apparently healthy milk samples were collected from individual and bulk tank milk of cows (100 and 86 samples, respectively), goats (30) and she camel (12) for isolation of some lactic acid bacteria (LAB) especially that have coccal form. The preliminary screening LAB community at the genus level depending on the basis of morphological characteristics showed that, the isolates were differentiated into 4 groups; Enterococci, Leuconostocs, Pediococci and Streptococci with a total percentage of 61%. The highest % of LAB was recorded for Enterococcus species in the different animal species especially in camel milk (41.7%). Antibacterial activity of selected 75 LAB strains against S. aureus, S. uberis, E. coli and Yersinia enterocolotica as bovine mastitis pathogens were detected. 53 out of 75 of the selected strains showed antibacterial effect against the tested pathogens. Eighteen Enterococcus isolates have inhibitory effects on all of the tested bacteria with inhibition zone diameter ranged between 10-25 mm. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was used as an aid step for identification of LAB strains. Thus the SDS-PAGE results confirmed the biochemical identification of the isolated cultures for Leuconostoc mesenteroides with a percentage of similarity (90.8%), for Pediococcus acidilactici (92.5%), for Enterococcus hirae (99.84%) and for Streptococcus thermophilus (99.89%). Representative strains of genus Enterococci that had higher antibacterial activity against mastitis pathogens were subjected to sequence-based identification. The obtained sequences of these isolates were submitted to the Gen Bank database with accession numbers KU847974 and KU847975 for E. faecium and E. hirae, respectively and showed 99% 16S rRNA sequence homology. It was concluded that raw animal milk may be a potential source for the isolation of probiotic LAB with antibacterial properties against mastitis pathogens that may be presented as an interesting alternative to antibiotic drugs to overcome the antibiotic resistance of mastitis pathogens as well as antibiotic residues in milk.
Highlights
Probiotic products were proposed as a valid alternative to antibiotic therapies and are useful for the prevention of infectious syndromes (Espeche et al, 2012).Bacteria proposed for probiotic uses are usually categorized as lactic acid bacteria (LAB); commonly used bacteria include various species of Lactobacillus, Bifidobacterium and Streptococcus as well as some Enterococcus species (Morrow et al, 2012)
In Egypt little information exists on lactic acid micro-biota in raw animal milk, for this reason, the objectives of this study were to collect a variety of raw milk samples from different animal species in order to constitute original collection of LAB strains, to pre-select some strains according to their beneficial characteristics that can be used as a source of probiotics for some mastitis pathogens depending on their in vitro antimicrobial properties and to confirm them depending on their whole cell proteins fingerprinting and genetic taxonomic identification
The preliminary screening of milk LAB community at the genus level depending on the basis of various morphological characteristics the isolates were differentiated into 4 groups, Enterococcus, Leuconostoc, Pediococcus and Streptococcus with a total percentage of (61%) that was near to that accounted by Aziz et al (2009) who found that the overall incidence of lactic bacteria in milk was 66 % and the incidence of lactic isolates was the highest in cow milk (75%) that agreed with the present results as LAB were isolated from cows‟ bulk tank milk that reached to 100% in the present study
Summary
Probiotic products were proposed as a valid alternative to antibiotic therapies and are useful for the prevention of infectious syndromes (Espeche et al, 2012).Bacteria proposed for probiotic uses are usually categorized as lactic acid bacteria (LAB); commonly used bacteria include various species of Lactobacillus, Bifidobacterium and Streptococcus as well as some Enterococcus species (Morrow et al, 2012). Probiotic products were proposed as a valid alternative to antibiotic therapies and are useful for the prevention of infectious syndromes (Espeche et al, 2012). Wild LAB strains represent a natural reservoir of strains not exposed to any industrial selection and are potential probiotics and bacteriocin producers (Guessas and Kihal, 2005). Bacteriocins can be either infused into the udder (in the same way as antibiotics), or used in solutions (such as teat dips). These proteins are larger molecules than antibiotics and are expected to persist in the udder longer. The rapid action of bacteriocins reduces the likelihood of an induced resistance in target and non target organisms (Miles et al, 1992)
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