Potentially pathogenic bacteria isolated from Paipa cheese and its susceptibility profiles to antibiotics and biocides

The objective of this work was to evaluate the microbiological quality of cheese produced by formal and informal micro-enterprises in Paipa, Colombia, to isolate potentially pathogenic bacteria and to determine their prevalence and resistance to antimicrobials such as antibiotics and biocides. Sixteen micro-enterprises of the seventy existing in the region were sampled during 3 years. Viable concentrations of aerobic mesophiles, total and fecal coliforms, Salmonella sp., Listeria monocytogenes , Staphylococcus sp., yeasts, and molds were determined. Seventy-three bacterial isolates were identified by 16S rRNA gene sequencing. The susceptibility of the isolates to antibiotics and biocides was determined. The results indicated that between 98 and 100% of the cheese samples ( n = 48 samples) of formal and informal micro-enterprises presented populations of total and fecal coliforms and Staphylococcus sp. above the limits established by Colombian regulations and varied according to the micro-enterprise. The results also indicated that 56% of Staphylococcus isolates were S. aureus . L. monocytogenes was positive in 38% of the samples. Salmonella sp. was not detected. The coliforms that prevailed were Escherichia coli (25%), Citrobacter freundii (14%), and Proteus mirabilis (8%). All L. monocytogenes were sensitive to ampicillin but resistant to erythromycin and trimethoprim-sulfamethoxazole. S. aureus isolates were susceptible to most antibiotics, except tetracycline and erythromycin (7% resistance). Likewise, 30% of coliforms ( n = 36) were multidrug-resistant to antibiotics but susceptible to biocides.