Interactions in milk psychrotrophic bacterial populations

Raw milk samples (n = 104) were collected from healthy cows at different seasons in the North East part of Algeria. Cold storage of samples at 4 degrees C was used to promote psychrotrophic microbial growth. The isolates obtained from Sterile Standard Plate Count (SPC) were characterized by phenotypic means using cultural, morphological, biochemical criteria; and genotypicaly using partial 16S rRNA gene sequencing. The psychrotrophic community was diversified and made of 13 bacterial populations, constituted of both spoilage and pathogenic bacteria, with the dominant population Enterococcus spp. (19.23 %). Principal Component Analysis was used to study interactions in psychrotrophic bacterial populations. Enterococcus registered low correlation values for the majority of the microorganisms detected. Listeria was correlated positively with Bacillus (r = 0.564) and negatively with Enterococcus (r = -0.468). Factorial Correspondence Analysis was used to study seasonal bacterial incidence. Listeria showed an association with winter and spring seasons. The most associated bacteria in time to Listeria were Stenotrophomonas, Pseudomonas and Bacillus. The data obtained allow the understanding of interactions in psychrotrophic bacterial populations, and is useful for preventing the risk of emergence of pathogenic bacteria at different months of the year.