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.

No abstract

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).

No abstract

Background and Objectives: Carotenoid pigments are among the most important pigments and have many applications in various food, cosmetics, hygiene industries and biotechnology. These pigments are produced by plants and microorganisms including Rhodotorula spp. This research intended to study the antimicrobial and antibiofilm effects of the carotenoid pigment from Rhodotorula glutinis on food spoilage bacteria (Staphylococcus aureus and Salmonella Typhimurium). Materials and Methods: The R. glutinis was isolated from milk samples of cows with mastitis and ITS sequence-based typing was performed on them. After extracting the pigment from R. glutinis, its purity was examined using thin-layer chromatography. Following that, the broth microdilution method was used to evaluate antimicrobial effects of the pigment and MtP assay and subsequently scanning electron microscopy were used to assess the antibiofilm effects. In addition, the sub-MIC effects of the pigment on expression of quorum-sensing (QS) genes in S. Typhimurium isolates (sdiA and luxS) and S. aureus isolates (hld) were studied. Finally, the degree of toxicity of the pigment was analyzed using the MTT assay. Results: ITS sequence analysis of R. glutinis revealed that the recently separated isolates exhibited strong differences with the strains recorded in NCBI database in genetic structure. The pigment produced by R. glutinis had strong antimicrobial effects and its mean MIC against S. Typhimurium isolates (17.0 μl.ml-1) was higher than the mean MIC against the S. aureus isolates (4.1 μl.ml-1). Electron microscope images and real-time observations indicated that the sub-MIC values of the pigment suppressed biofilm formation by suppressing expression of QS genes. In addition, the mentioned pigment at high MIC concentrations did not have toxic effects on Vero cells. Conclusion: This research suggests that R. glutinis pigment is effective in destroying the planktonic form of food spoilage bacteria and degrading food spoilage biofilm-forming bacteria. Moreover, considering the low toxicity level of R. glutinis pigment for eukaryotic cells, we can suggest its use as a natural antibacterial preservative in various food materials.

Rabies is a viral disease causing acute encephalitis in humans or animals. Rabies virus belongs to the genus Lyssavirus, family Rabdoviridea. The virus has a single, negative-stranded RNA genome encoding five structural proteins, including nucleoprotein (N), phosphoprotein (P), matrix protein (M), glycoprotein (G) and RNA dependent RNA polymerase gene (L). All of the provinces of Iran are infected with rabies. Although there is no cure for rabies, it is totally preventable by proper vaccination. Effective vaccine can be used for pre-and post-exposure prophylaxis. Glycoprotein has a main role in pathogenicity and immunogenicity thus variation in genetic sequence of this gene leads to variation in antigenic and pathogenic properties of rabies virus. Therefore, in this study, we analyzed the antigenic sites of the glycoprotein from rabies virus strains used in vaccine manufacture and compared their epitope sequences to wild type strain. We have used RT-PCR technique to determine the genetic sequence of these strains. Phylogenetic analysis showed that the wild type street virus isolate found in Iran were related to genotype 1 (classical rabies virus) and shared a high homology with the vaccine strains. Furthermore comparison of amino acid sequences of major and minor antigenic sites between the wild type and several vaccinal strains showed that the virus had a higher homology with the vaccinal strain PV that is used to manufacture vaccines in the country.

No abstract