Staphylococcus aureus is recognized worldwide as one of the major agents of dairy cow intra-mammary infections. This microorganism can express a wide spectrum of pathogenic factors used to attach, colonize, invade and infect the host. The present study evaluated 120 isolates from eight different countries that were genotyped by RS-PCR and investigated for 26 different virulence factors to increase the knowledge on the circulating genetic lineages among the cow population with mastitis. New genotypes were observed for South African strains while for all the other countries new variants of existing genotypes were detected. For each country, a specific genotypic pattern was found. Among the virulence factors, fmtB, cna, clfA and leucocidins genes were the most frequent. The sea and sei genes were present in seven out of eight countries; seh showed high frequency in South American countries (Brazil, Colombia, Argentina), while sel was harboured especially in one Mediterranean country (Tunisia). The etb, seb and see genes were not detected in any of the isolates, while only two isolates were MRSA (Germany and Italy) confirming the low diffusion of methicillin resistance microorganism among bovine mastitis isolates. This work demonstrated the wide variety of S. aureus genotypes found in dairy cattle worldwide. This condition suggests that considering the region of interest might help to formulate strategies for reducing the infection spreading.
Porous Mn-doped ZnO (ZnO:Mn) nanoparticles with an average diameter of ca. 21 nm were prepared by a simple and cheap solvothermal process involving no templates, post-synthetic annealing or etching. The particles produced were characterized by XRD, Raman spectroscopy, SEM, TEM, XPS, diffuse reflectance spectroscopy and BET surface area measurements and the effects of Mn 2+-doping on the structural, optical and photocatalytic properties of ZnO particles were investigated. The particles doped with 3 mol% Mn 2+ were found to exhibit the highest catalytic activity toward the photodegradation of the Orange II dye under solar light irradiation. Our results demonstrate that Mn 2+-doping shifts the optical absorption to the visible region, increases the specific surface area of the photocatalyst and reduces the recombination of electron-hole pairs. The influence of various operational parameters (amount of catalyst, concentration of dye and pH) on the photodegradation and the photocatalytic mechanism were studied. Finally, we demonstrated that the ZnO:Mn photocatalyst is stable and can be easily recycled up to ten times without any significant decrease in photocatalytic activity.
This paper describes the characteristics of Staphylococcus aureus isolated from bulk tank and individual cow milk in Tunisia. All strains were genotyped by spa typing and RS-PCR, a method based on the amplification of the 16S-23S rRNA intergenic spacer region, and multiplex PCRs for 22 virulence genes. A selected subsample of strains was also genotyped by multilocus sequence typing. All strains were tested for antimicrobial resistance. Our study evidences a predominance of strains belonging to Clonal Complex 97. Methicillin-resistant strains were not detected, and overall low level of antimicrobial resistance was reported.
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