Objective: Mastitis is one of the most costly diseases in dairy cows, which greatly decreases milk production. Use of antibiotics in cattle leads to antibiotic-resistance of mastitis-causing bacteria. The present study aimed to investigate synergistic effect of silver nanoparticles (AgNPs) with neomycin or gentamicin antibiotic on mastitis-causing Staphylococcus aureus. Materials and Methods: In this study, 46 samples of milk were taken from the cows with clinical and subclinical mastitis during the august-October 2015 sampling period. In addition to biochemical tests, nuc gene amplification by PCR was used to identify strains of Staphylococcus aureus. Disk diffusion test and microdilution were performed to determine minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Fractional Inhibitory Concentration (FIC) index was calculated to determine the interaction between a combination of AgNPs and each one of the antibiotics. Results: Twenty strains of Staphylococcus aureus were isolated from 46 milk samples and were confirmed by PCR. Based on disk diffusion test, 35%, 10% and 55% of the strains were respectively susceptible, moderately susceptible and resistant to gentamicin. In addition, 35%, 15% and 50% of the strains were respectively susceptible, moderately susceptible and resistant to neomycin. According to FIC index, gentamicin antibiotic and AgNPs had synergistic effects in 50% of the strains. Furthermore, neomycin antibiotic and AgNPs had synergistic effects in 45% of the strains. Conclusion: It could be concluded that a combination of AgNPs with either gentamicin or neomycin showed synergistic antibacterial properties in Staphylococcus aureus isolates from mastitis. In addition, some hypotheses were proposed to explain antimicrobial mechanism of the combination.

Brucellosis has always been a threat to the health and economics of societies. We report a new colorimetric immunoassay based on colored silica nanoparticles for detection of Brucella abortus. An immunosensor was designed based on blue-SiNPs and paramagnetic nanoparticles (PMNPs). The synthesized immunosensor was conjugated with a polyclonal antibody against B. abortus, which was activated by 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) and N-hydroxysuccinimide (NHS) to form detection and capture probes, respectively. After adding the conjugates to the bacterial suspension, sandwich structure of PMNPs B. abortus-blue-SiNPs was formed and then separated by a magnet. The blue dye was released from the silica structure and its absorbance was measured at 670 nm with a spectrophotometer. Under optimal conditions, results showed a wide dynamic range from 1.5 Â 10 3 to 1.5 Â 10 8 cfu mL À1 with a detection limit of 450 cfu mL À1. The specificity of the sensor was confirmed in comparison with 5 other bacteria. Also, during the 120-days period, the complex was stable. The results suggested that it can be used in real samples (R 2 ¼ .9865). This designed colorimetric immunoassay strategy can be used as an alternative, user-friendly and on-site tool for the rapid detection of Brucella spp. compared to other common methods with high sensitivity and specificity in a short time.

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A molecularly imprinted polymer (MIP) sensor was offered for nevirapine (NVP) analysis based on the electropolymerization of pyrrole (Py) on electrochemically reduced graphene oxide (ErGO) immobilized on a glassy carbon electrode (GCE).

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