A large variety of cheeses can be produced using different manufacturing processes and various starter or adjunct cultures. In this study, we have described the succession of the microbial population during the commercial production and subsequent ripening of smear-ripened cheese using 16S rRNA gene sequencing. The composition of the microbiota during the first 6 days of production was constant and consisted mainly of LAB (lactic acid bacteria) originating from the starter culture. From day 7, the proportion of LAB decreased as other bacteria from the production environment appeared. From the 14th day of production, the relative proportion of LAB decreased further, and at the end of ripening, bacteria from the environment wholly dominated. These adventitious microbiota included Psychrobacter, Pseudoalteromonas haloplanktis/hodoensis, Vibrio toranzoniae, and Vibrio litoralis (Proteobacteria phylum), as well as Vagococcus and Marinilactibacillus (Firmicutes phylum), Psychrilyobacter (Fusobacteria phylum), and Malaciobacter marinus (Campylobacterota phylum), all of which appeared to be characteristic taxa associated with the cheese rind. Subsequent analysis showed that the production and ripening of smear-ripened cheese could be divided into three stages, and that the microbiota compositions of samples from the first week of production, the second week of production, and supermarket shelf life all differed.

The absence of acquired resistance to antimicrobials has become an important criterion in evaluation of the biosafety of lactobacilli used as industrial starter or probiotic cultures. The aim of this study was to assess antibiotic resistance in starter and non-starter lactobacilli of food origin. Minimal inhibitory concentrations of ampicillin, chloramphenicol, clindamycin, erythromycin, gentamicin, kanamycin, streptomycin, tetracycline and vancomycin were established in 81 strains of lactobacilli ( L. acidophilus , L. animalis , L. brevis , L. curvatus , L. delbrueckii , L. fermentum , L. helveticus , L. paracasei , L. plantarum , L. rhamnosus and L. sakei ) by the microdilution method. The strains were classified as susceptible or resistant to antimicrobials based on the cut-off values according to the EFSA guideline. Sixty-two strains (77% food isolates, 76% starter or adjunct cultures) were resistant to at least one antimicrobial agent (the most frequently to aminoglycosides). Adjunct cultures showed a higher antibiotic resistance (80%) than starters (60%). Four multiresistant strains (3 food isolates, 1 adjunct culture) were analyzed by whole genome sequencing. One potentially transferable aad E gene (responsible for streptomycin resistance) was detected only in one multi-drug resistant strain of L. animalis originating from an adjunct culture. Thus, there is a risk of horizontal transmission of this gene. It is necessary to eliminate such strains from use in the food industry. This study provides relevant data concerning the use of lactobacilli in safe food production. To ensure food safety, detailed characterization of resistance to antimicrobials is necessary not only in starter strains but also in non-starter lactic acid bacteria isolated from food products.

Smear-ripened cheeses are distinguished by their complex microbiota, which play an important role in ripening, flavour development, texture and microbiological safety. Although commercial production typically relies on defined starter and adjunct cultures, microorganisms from the production environment may also shape the product’s characteristics. This study examined the microbial composition of smear-ripened cheeses from six commercial manufacturers using culture and culture-independent techniques, including 16S rRNA gene sequencing and sequencing of internal transcribed spacers. A limited number of microorganisms was recovered by culture, with 37 different isolates identified across all samples. Sequencing of the 16S rRNA gene and internal transcribed spacers revealed 75 and 7 distinct operational taxonomic units, respectively. The microbiota composition reflected the contribution of both mesophilic and thermophilic starter and adjunct cultures, alongside microorganisms originating from the production environment. These included various psychrotrophic bacteria, marine (i.e., osmotolerant) bacteria, and other halophiles from Proteobacteria (Psychrobacter, Pseudoalteromonas, Marinomonas, and Vibrio), Firmicutes (Vagococcus and Marinilactibacillus), Actinobacteriota (Glutamicibacter), Bacteroidota (Winogradskyella and Brumimicrobium), Campylobacterota (Malaciobacter) and Fusobacteriota (Psychrilyobacter) specific to the environment of particular manufacturers. The results indicate that, although pasteurised milk and defined starter cultures are used in commercial production, microorganisms originating from the cheese factory environment form a substantial part of the microbiota of smear-ripened cheese.

This study focused on the detection and quantification of selected bacteria and on the presence of enterotoxin genes in milk and dairy products from sheep and goat farms in the Czech Republic using quantitative real-time PCR (qPCR) and multiplex PCR (PCR). The presence of Corynebacterium pseudotuberculosis (CP), Mycobacterium avium subsp. paratuberculosis (MAP), Listeria monocytogenes, Staphylococcus aureus, S. aureus enterotoxin genes and methicillin-resistant Staphylococcus aureus (MRSA) was determined in 18 milk samples, 28 fresh cheeses, 20 ripened cheeses and 14 yoghurts. The serological status of the herds in relation to CP and MAP was taken into account. The most frequently detected bacterium was S. aureus (48.8%), and subsequent PCR revealed 11 MRSA positive samples. The S. aureus enterotoxin genes seg, sei and sec were detected in two goat cheeses. Cheese samples showed a statistically higher risk of SA and MRSA occurrence. CP (8.8%) and MAP (13.8%) were detected by qPCR on two different seropositive farms. Cultivation of qPCR positive CP samples on agar plates supplemented with potassium tellurite showed the presence of viable bacterium. The results obtained confirmed the necessity of monitoring the infectious status of dairy animals and rapid diagnosis of bacterial pathogens in milk and dairy products.