Investigation of <i>Staphylococcus</i> spp. and Coliform Bacteria Contamination Sources after Cleaning-in-Place in Production Lines of Dairy Factories in Türkiye

Microorganisms detected on dairy factory surfaces after disinfection can cause product contamination, leading to economic losses and health hazards for consumers. In this study, the presence of <i>Staphylococcus</i> spp. and Coliform in a total of 450 samples taken from food-contact and non-contact surfaces (stainless steel, plastic, cloth, and tiles surfaces), raw milk and final product (white cheese, kashar cheese, butter, yogurt, and cream) samples in five dairy factories was investigated by conventional techniques. The isolates obtained were identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry. In this study, a total of 54 <i>Staphylococci</i> (16.7% <i>S. aureus</i> and 81.5% coagulase-negative <i>Staphylococci</i> [CNS]) and 44 coliform isolates were identified at the species level. The most common CNS isolated by samples was <i>S. epidermidis</i> followed by <i>S. saprophyticus, S. capitis, S. succinus S. carnosus</i>. <i>S. xylosus, S. sciuri, S. equorum, S. warneri,</i> and <i>S. hominis</i>. Eighteen of the coliform isolates (41%) were identified as <i>E. coli</i>; 13 (29.5%) as <i>E. cloacae</i>; 3 (6.9%) as <i>E. kobei, C. freundii,</i> and <i>K. oxytoca</i>; 2 (4.5%) as <i>K. pneumoniae</i>; 1 (2.3%) as <i>E. ludwigii</i> and <i>C. farmeri</i>. The contamination rate of non-food contact surfaces (71.3%) was found to be higher than food contact surfaces (10.4%), and contaminated surfaces were found to be effective in product contamination. Study results show that some bacterial species obtained from raw milk, surfaces, and final products are factory specific and surface-associated bacteria are prominent in the product microbial profile.