Abstract The most important microorganisms contaminating milk, such as staphylococci, exert their influence by producing toxins and biogenic amines (BA). The purpose of this study was to evaluate the influence of cell-free supernatants (CFS) related to the probiotic strains of Lactococcus lactis and Bifidobacterium bifidum on the expression of BA-producing genes, histamine decarboxylase, and tyramine decarboxylase in staphylococci isolated from milk. Staphylococci isolates of cow raw milk were identified and isolated using standard methods. Samples containing these strains were analyzed by HPLC for BA production. Bacteria with target genes were treated with L. lactis and B. bifidum CFS, and the expression of target genes was measured by Real time PCR. Generally, 60 strains of Staphylococcus were isolated, and 90% of strains had HDC and TDC genes in genome. The levels of BAs were significantly higher on the second and third days after sampling compared with the first day (p <0.02). The analysis RT-PCR indicated that the under expression of target genes was statistically significant (P<0.05). This study showed that the use of probiotic bacteria can reduce the production of these amines and increase the quality of milk through reducing the expression of tyramine and histamine producing genes.

Release of antibiotics to the environment as a result of wastewater effluent discharge is a cause for concern worldwide, as they pose a potential threat to human health and the earth ecosystem. Penicillin and amoxicillin are widely used antibiotics. Despite their rapid hydrolysis in aqueous matrices, their presence in the environment is widely investigated. The current study reported and analysed the current state of four hospital wastewater treatment plants (WWTPs) in Gonbad Kavous, Iran, during 2019, from the perspective of amoxicillin and penicillin G removals. WWTPs were sampled at various stages of the treatment process to determine at which stage the antibiotics are being removed. Concentrations of amoxicillin and penicillin G in raw wastewater, analysed by HPLC, varied from 0.35 to 1.02 and 0.02-0.31 /AgL-1, respectively. These values reduced in the final effluent, corresponding to overall efficiency in removing the studied antibiotics of 20-60.5%. Anaerobic processes (i.e. septic tank) slightly outperformed aerobic biological processes for both antibiotics' removal, and penicillin G was removed more efficiently than amoxicillin. Effects of wastewater physicochemical properties, including chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total suspended solids (TSS) on antibiotics removal, were also studied. Whereas statistically significant correlations were noticed between COD, amoxicillin and penicillin G removals, their decline showed no correlation with TSS removal. Our study shows that despite the deployment of treatment plants, a considerable amount of antibiotics is released into receiving water bodies, resulting in significant amounts of these pharmaceuticals entering the environment. There is abundant room for further progress in the detection and quantification of pharmaceuticals and other emerging contaminants in hospital wastewaters and their metabolites and biodegradation products.