Diagnostic Performance of rep-PCR as a Rapid Subtyping Method for Listeria monocytogenes

Safety assessment of the indigenous probiotic strain Lactiplantibacillus plantarum subsp. plantarum Kita-3 using Sprague-Dawley rats as a model

Lactiplantibacillus plantarum subsp. plantarum Kita-3 is a candidate probiotic from Halloumi cheese produced by Mazaraat Artisan Cheese, Yogyakarta, Indonesia. This study evaluated the safety of consuming a high dose of L. plantarum subsp. plantarum Kita-3 in Sprague-Dawley rats for 28 days. Eighteen male rats were randomly divided into three groups, such as the control group, the skim milk group, and the probiotic group. Feed intake and body weight were monitored, and blood samples, organs (kidneys, spleen, and liver), and the colon were dissected. Organ weight, hematological parameters, serum glutamic oxaloacetic transaminase (SGOT), and serum glutamic pyruvic transaminase (SGPT) concentrations, as well as intestinal morphology of the rats, were measured. Microbial analyses were carried out on the digesta, feces, blood, organs, and colon. The results showed that consumption of L. plantarum did not negatively affect general health, organ weight, hematological parameters, SGOT and SGPT activities, or intestinal morphology. The number of L. plantarum in the feces of rats increased significantly, indicating survival of the bacterium in the gastrointestinal tract. The bacteria in the blood, organs, and colon of all groups were identified using repetitive-polymerase chain reaction with the BOXA1R primers and further by 16S rRNA gene sequencing analysis, which revealed that they were not identical to L. plantarum subsp. plantarum Kita-3. Thus, this strain did not translocate to the blood or organs of rats. Therefore, L. plantarum subsp. plantarum Kita-3 is likely to be safe for human consumption.

Detection, identification, and typing of Listeria species from baled silages fed to dairy cows

Anaerobiosis, critical for successful ensilage, constitutes a challenge in baled silages. The loss of complete anaerobiosis causes aerobic deterioration and silages undergo dry matter and nutrient losses, pathogen growth, and mycotoxin production. Silage may represent an ideal substrate for Listeria monocytogenes, a pathogen of primary concern in several cheeses. The aim of this research was to investigate the occurrence of Listeria in baled silage fed to cows producing milk for a protected designation of origin cheese, and to characterize isolates by repetitive sequence-based PCR. Listeria spp. were detected in 21 silages and L. monocytogenes in 6 out of 80 of the analyzed silages; 67% of positives were found in molded zones. Results of the PCR typing showed genotypic homogeneity: 72.9 and 78.8% similarity between strains of Listeria spp. (n=56) and L. monocytogenes (n=24), respectively. Identical profiles were recovered in molded and nonmolded areas, indicating that contamination may have occurred during production. The application of PCR allowed the unambiguous identification of Listeria isolated from baled silages, and repetitive sequence-based PCR allowed a rapid and effective typing of isolates. Results disclose the potential of the systematic typing of Listeria in primary production, which is needed for the understanding of its transmission pathways.