Aims: This study was designed to determine the virulence genes and antibiotic resistance profiles of Staphylococcus aureus isolated from dogs, cats, chickens and horses. Methodology and results: A total of 15 S. aureus isolates were used in this study. Antibiogram and screening of virulence genes was carried out using disc diffusion method and polymerase chain reaction. The results obtained showed that a total of 9 S. aureus isolates were resistant towards oxacillin (60%), 9 isolates were resistant towards neomycin (60%) and 8 isolates were resistant towards tilmicosin (53%). Resistance to amoxicillin, tetracycline and vancomycin was also observed in 6 (40%) of the isolates. Additionally, 5 (33%) of the isolates showed resistance towards streptomycin and linzolide while 4 (27%) of the isolates were resistant towards rifampin, erythromycin and mupirocin. Lastly, 3 (20%) of the isolates were resistant towards doxycycline. Intermediate resistance to amoxicillin and doxycycline was also observed. Virulence gene profiling showed that 4 (26.7%) of the isolates were positive for hlβ and SspA, 9 of the isolates (60%) showed positive for geh and 12 of the isolates (80%) showed positive for Set-1. Similarly, 2 (13.3%) of the isolates showed positive for etA and Seu while only 1 isolate (6.7%) showed positive for PVL and hlα. None of the isolates were positive for tst-1 and etB. Conclusion, significance and impact of study: This study revealed reduced susceptibility and multiple drug resistance (MDR) in four isolates, and susceptibility to all antibiotics in two isolates in addition to low carriage rate of virulence gene in all isolates. Thus, indicating resistance development in majority of the isolates and the need to regulate indiscriminate use of antibiotics in animals.
Staphylococcus aureus

Pasteurella multocida serotype B:2 causes hemorrhagic septicemia in cattle and buffalo. The invasion mechanism of the bacterium when invading the bloodstream is unclear. This study aimed to characterize the effects of immunomodulatory molecules, namely dexamethasone and lipopolysaccharide, on the invasion efficiency of P. multocida serotype B:2 toward bovine aortic endothelial cells (BAECs) and the involvement of actin microfilaments in the invasion mechanism. The results imply that treatment of BAECs with lipopolysaccharide at 100 ng/mL for 24 h significantly increases the intracellular bacteria number per cell (p < 0.01) compared with those in untreated and dexamethasone-treated cells. The lipopolysaccharide-treated cells showed a significant decrease in F-actin expression and an increase in G-actin expression (p < 0.001), indicating actin depolymerization of BAECs. However, no significant differences were detected in the invasion efficiency and actin filament reorganization between the dexamethasone-treated and untreated cells. Transmission electron microscopy showed that P. multocida B:2 resided in a vacuolar compartment of dexamethasone-treated and untreated cells, whereas the bacteria resided in cellular membrane of lipopolysaccharide-treated cells. The results suggest that lipopolysaccharide destabilizes the actin filaments of BAECs, which could facilitate the invasion of P. multocida B:2 into BAECs.
Actin Cytoskeleton ; Actins ; Animals ; Bacteria ; Buffaloes ; Cattle ; Dexamethasone ; Endothelial Cells ; Hemorrhagic Septicemia ; In Vitro Techniques ; Membranes ; Microscopy, Electron, Transmission ; Pasteurella multocida ; Pasteurella ; Serogroup