NUMERICAL TAXONOMY OF PSYCHROTROPHIC BACTERIA ISOLATED FROM RAW EWES MILK

A total of 204 psychrotrophic isolates from raw ewes' milk (hand and machine milked) were identified by conventional methods. In addition, a numerical taxonomic study was conducted on 180 of these isolates and 19 reference strains. Three of the isolates were yeasts. Using identification schemes, 54 isolates were assigned to genera of Gram-negative aerobic rods (Pseudomonas, Acinetobacter, Flavobacterium, Moraxella and Psychrobacter), 48 were Enterobacteriaceae (Enterobacter, Hafnia, Klebsiella, Citrobacter and Serratia) and one was identified as Aeromonas hydrophila. The 98 Gram-positive isolates were identified as Enterococcus, Streptococcus, Leuconostoc, Lactococcus, Bacillus, Staphylococcus, Micrococcus, Aureobacterium, Kurthia and Microbacterium. At the 82 % similarity level (S(SM)), 18 clusters were formed. Cluster I included 34 strains of Lactococcus, Streptococcus and Leuconostoc. Most of the 35 strains in cluster II were Enterococcus. Clusters III and IV were identified as Kurthia and Microbacterium respectively. Cluster V was identified as Aureobacterium and cluster VI consisted of coagulase-negative staphylococci. Gram-negative isolates formed 12 clusters: Aeromonas (one cluster), Enterobacteriaceae (two clusters), Flavobacterium (two clusters), Pseudomonas and Psychrobacter immobilis (three clusters) and Acinetobacter (four clusters). Non-motile variants of Ps. fragi were found. Enterococcus and Enterobacteriaceae did not have significant spoilage properties. As expected, Gram-negative aerobic rods were proteolytic and/or lipolytic even at low temperature. Contamination with certain types of psychrotrophs (Gram-negative aerobic rods and enterococci) seemed to be associated with the milking method. The isolate of Aes. hydrophila had properties associated with virulence.