Background: Agr systems, is responsible for control and coordination in production of virulence factors, exotoxins secretory and hemolysins in Staphylococcus aureus. The aim of this study was to determine and identify the frequency of agr genes in susceptible and methicillin-resistant Staphylococcus aureus strains in clinical samples and carriers employed in remedial centers.

Materials and Methods: This descriptive study was done among a total of 200 strains of Staphylococcus aureus isolated from clinical samples and healthy carriers in Hamadan. Antibiotic susceptibility pattern of all isolates was determined by disk diffusion methods. After DNA extraction, the presence of mecA and agr genes was investigated using PCR. SPSS software package version 20 was used to perform statistical tests.

Results: All 200 Staphylococcus aureus strains were susceprible to vancomycin. The prevalence of mecA was 50%. The PCR results showed that agrA was the most perevalent gene followed by the agrC in all isotated Staphylococcus aureus strains. None of the isolates harbored the agrB and agrD gene.

Conclusion: Pathogenesis of Staphylococcus is dependent on some proteins other superficial or excreted which under controlling of agr system. In the present study, the feequency of agrA gene in the methicillin-resistant strains, methicillin-sensitive strains isolated from clinical samples and carriers employed in remedial centers was higher than the other agr types. Therefore, presumably, agrA gene plays an important role Staphylococcal infections.

Background: Brucellosis is one of the most important diseases among humans and animals. Clinical management of brucellosis due to an increased rate of treatment failure and recurrence is extremely worrying. The aim of this study was to determine the antimicrobial susceptibility pattern of the brucella isolates.

Materials and Methods: From April to September 2014 a total of 30 brucella isolates that were cultured on brucella agar has been studied. The species identification was carried out and to determine the effect of antibiotics on bacteria antibiogram testing was performed by disk diffusion.

Results: In this study, 30 brucella strains were isolated from cultured specimens and antibiogram testing was performed. All microbial positive specimens were sequenced by PCR. All isolates were Brucella melitensis. According to the tests, suceptibility to tetracycline, minocycline, gentamicin, tigecyclin was 100%, to doxycycline 93.3%, co-amoxiclave 66.7%, rifampin 44.7%, streptomycin 86.7%, ciprofloxacin 80%, cotrimoxazole 76.7% and ceftriaxone 73.3%.

Conclusion: This study shows that the predominant strain in our patients was Brucella melitensis. Also, due to high levels of resistance to rifampin to use the other effective drugs like gentamicin, streptomycin, ciprofloxacin or cotrimoxazole in combination with doxycycline or tetracycline.