Jolanta G. Rola, Weronika Korpysa-Dzirba and Jacek Osek
The aim of the study was to identify the potential sources of contamination of traditionally made cheeses during their production with Staphylococcus aureus . The samples were collected at nine dairy farms at different points of manufacturing the cheeses. Isolation and enumeration of coagulase positive staphylococci (CPS) on Baird- Parker RPF agar was conducted, and detection of staphylococcal enterotoxins (SEs) was performed using ELISA and ELFA. The genes encoding SEs were identified by PCR. CPS were isolated from 51 samples with the highest level of contamination in mature cheese up to 107 CFU g-1. No SEs were detected in tested samples; however, enterotoxic CPS strains were found.
Weronika Korpysa-Dzirba, Jolanta G. Rola and Jacek Osek
This study describes preparation of test samples composed of freeze-dried strain of S. aureus and powdered milk as a matrix. In the first part of the study, the number of S. aureus cells freeze-dried in skim milk or horse serum were compared at two levels of contamination (104 and 105 cfu g-1). The analysis of the samples was performed three times within a week. The preliminary results showed that the samples composed of S. aureus freeze-dried in horse serum were more stable and homogeneous than those prepared with skim milk. These results were further confirmed after analysing a higher number of such samples. Therefore, this procedure was then chosen for preparation of the samples for proficiency tests (PTs). Homogeneity and stability of these samples were checked according to ISO 13528. The results obtained showed that the samples met the criteria of stability and homogeneity required for PTs and were used in PT for enumeration of S. aureus in powdered milk.
Piotr Jedziniak, Małgorzata Olejnik, Jolanta G. Rola and Teresa Szprengier-Juszkiewicz
A multiresidue method (LC-MS/MS) for determination of wide range of anthelmintics was developed. The method covered benzimidazoles: albendazole (and metabolites), cambendazole, fenbendazol (and metabolites), flubendazole (and metabolites), mebendazole (and metabolites), oxibendazole, thiabendazole (and metabolites), triclabendazole (and metabolites); macrocyclic lactones: abamectin, doramectin, emamectin, eprinomectin, ivermectin, moxidectin; salicylanilides: closantel, ioxynil, nitroxynil, oxyclosamide, niclosamide, rafoxanid and others: clorsulon, derquantel, imidocarb, monepantel (and metabolites), morantel, praziquantel, and pyrantel. The method was used to examine the potential presence of anthelmintics in goat and sheep milk and dairy products from the Polish market. A total of 120 samples of milk, yoghurt, cottage cheese, cream cheese, and curd were analysed. None of the samples were found positive above CCα (1-10 μg/kg) except for one cottage cheese in which traces of albendazole sulfone were detected (5.2 ug/kg) and confirmed. The results of the study showed negligible anthelmintic residues in the goat and sheep milk and dairy products and confirm their good quality.