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Showing 2 results for Vajdi Hokmabad
Volume 20, Issue 139 (September 2023)
Abstract
Excessive use of antibiotics in the animal husbandry causes the accumulation of their residual amounts in food of animal origin such as dairy products. Since the consumption of these foods has a negative effect on human health, authorized organizations such as the European :union: have set maximum residue limits (MRLs) for antibiotics in food of animal origin. This research aimed to present a magnetic ionic solvent based extraction procedure for preparation and preconcentration of tetracycline, oxytetracycline and enrofloxacin residues in cheese samples and their determination by high-performance liquid chromatography equipped with a diode array detector. For this, the effect of various parameters on the extraction efficiency was investigated and optimized. The results showed that the residual amounts of oxytetracycline and tetracycline in 4 and 5 samples of the tested cheeses, respectively, were determined above the permissible limits. Enrofloxacin residue was not found in any of the samples. From the advantages of the proposed extraction method, we can point out the high separation power and the possibility of highly sensitive analyzing of mixed analytes, so that under optimized conditions, the recovery percentage ranges were 80-91. The limits of detection and quantification were respectively less than 1.8 and 6 ng/g, which is much lower than the MRLs set for target antibiotics in cheese (100 ng/g).
Volume 22, Issue 158 (April 2025)
Abstract
The main reason for the presence of specific microbiota, particularly lactic acid bacteria in dairy products made from raw milk, such as Lighvan cheese, is the traditional methods of preparing these products. A large number of these bacteria are probiotic microorganisms, and for example, many species of Lactobacillus, Enterococcus and Pediococcus bacteria presented in foods have shown probiotic properties. In the current study, genus-specific PCR detection for the Lactobacillus, Enterococcus, and Pediococcus genera was used to confirm the isolates of lactic acid bacteria that had been phenotypically isolated from 25 samples of traditional Lighvan cheese. Subsequently, the probiotic properties of the isolates, including resistance in simulated gastrointestinal tract conditions, antagonistic properties, auto-aggregation and co-aggregation attributes, antibiotic resistance and hemolytic activities of the selected strains were evaluated. Based on biochemical and molecular detection tests, among the 84 selected strains, 58 isolates were identified as Lactobacillus (29 isolates), Enterococcus (18 isolates) and Pediococcus (11 isolates). Screening of these isolates for survival in human GI tract conditions showed that 26.1% of the isolates (14 isolates) had resistance levels above 50%. Also, nine isolates of the selected strains showed potent antibacterial activity against Listeria monocytogenes and Staphylococcus aureus, as well as Aspergillus flavus and Penicillium citrinum molds. Moreover, based on the ability of auto-aggregation and co-aggregation features, four isolates LS106, LS71, LS33 and LS6 (belonging to Lactobacillus and Enterococcus genera) were selected. Finally, the investigation of antibiotic resistance revealed the sensitivity of these isolates to majority of the used antibiotics, so that all isolates were susceptible to tetracycline and ampicillin. Also, not one of these four isolates exhibited hemolytic properties. As a result, these isolates are recommended as suitable candidates for usage in fermented food products, taking advantage of their beneficial properties.
