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ZnO nanoparticles (ZnO-NPs) can be synthesized by chemical, physical and biological methods; many studies have indicated that biologically synthesized ZnO-NPs have ecofriendly benefits over physically and chemically synthesized ZnO-NPs. This study was carried out to evaluate the differences in characteristics and effects on pathogenic bacteria between ZnO-NPs synthesized by a chemical method and a biological method using the marine green alga Ulva fasciata. Additionally, the synergistic or antagonistic effects of loading ZnO-NPs synthesized by chemical and biological methods on antibiotics are investigated. The results show that there are differences in the characteristics of ZnO-NPs synthesized by the various methods, as determined by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). ZnO-NPs had antibacterial activity against Staphylococcus aureus, Salmonella enterica subsp. salamae (Em.1-EGY015), Aeromonas hydrophila, Escherichia coli O157 (KY797670) and Bacillus cereus SH06; moreover, green-synthesized ZnO-NPs were more effective against pathogenic bacteria than chemically synthesized ZnO-NPs. The minimum inhibitory concentration (MIC) of ZnO-NPs synthesized by the green method was less than that of ZnO-NPs synthesized by the chemical method. The results demonstrated that the synergistic or antagonistic effects of ZnO-NP loading on antibiotics (ampicillin/sulbactam, tobramycin, flucloxacillin, chloramphenicol, amoxicillin, cephalexin, of loxacin, and neomycin) varied according to the type of pathogenic bacteria, antibiotic, and method of synthesis of ZnO-NPs. [ABSTRACT FROM AUTHOR]

This study was carried out to investigate the resistance to some antimicrobial groups among Salmonellae isolated from broilers in Egypt. The prevalence of some virulence and resistance genes among the recovered multidrug resistant (MDR) isolates was also scrutinized. A total of 55 (15·6%) Salmonella isolates were recovered from 353 different samples (liver, yolk sac, gall bladder and caecum), gathered from apparently healthy and diseased broilers suffered from diarrhoea, dehydration and respiratory distress. Thirty Salmonellae strains were serotyped into Salmonella Enteritidis, Salmonella Infantis, Salmonella Kentucky, Salmonella Maloma, Salmonella Bardo, Salmonella Gdansk, Salmonella Typhimurium and Salmonella Blegdame. The resistance pattern of all Salmonella isolates was constructed and 15 MDR Salmonella isolates were subsequently examined for the presence of virulence (invA, ompA and stn) and resistance (qnrS, qnrA, bla TEM and bla CTX ) genes. Of note, invA, ompA and stn virulence genes and bla TEM and qnrS resistance genes were found in all examined isolates. On the other hand, the qnrA gene detection frequency was 20%, whereas bla CTX was not detected at all. Our findings emphasize the wide spread of antimicrobial resistance genes in Salmonella isolates and the importance of effective control measures for the disease. SIGNIFICANCE AND IMPACT OF THE STUDY: This study highlights the possible emergence of widespread resistance to some antimicrobials among Salmonellae isolated from broilers in Egypt. The results also reveal the prevalence of some virulence (invA, ompA and stn) and resistance (qnrS, qnrA, bla CTX and bla TEM ) genes among the recovered multidrug resistant isolates. Clearly, our data emphasize that antimicrobial resistance genes are widely spread in Salmonella isolates which is crucial for developing novel methods for controlling such disease problem of zoonotic concern., (© 2018 The Society for Applied Microbiology.)