Background: Staphylococcus aureus has a huge armory of virulence factors which are under the control of the quorum-sensing accessory gene regulator (agr) system. agr dysfunctional strains usually have a higher ability to form biofilm. The aim of the work was to detect the association of agr groups, agr functionality and biofilm formation among methicillin resistant and methicillin sensitive Staphylococcus aureus (MRSA/MSSA) isolated from clinical and nasal carrier specimens. Methods: Antibiotic susceptibility testing (AST) was performed to 100 clinical samples and 50 nasal carriers. Isolates were then characterized by agr typing using multiplex PCR. agr activity was evaluated using agr CAMP assay. Biofilm formation was determined phenotypically by microtiter plate method and genotypically by amplifying icaA and icaD genes. Results: A high level of resistance to different classes of antibiotics was detected. Methicillin resistant Staphylococcus aureus was more prevalent among clinical samples than nasal samples. No vancomycin resistant Staphylococcus aureus was detected. The percentage of agr dysfunctional isolates and the ability to form biofilm were higher in clinical samples than in nasal swabs, and more prevalent in MRSA than in MSSA. agr I was the most predominant allele among all isolates. The percentage of biofilm formation was higher among non-functioning agr isolates. icaD gene was the most prevalent biofilm formation gene detected. Conclusion: The formation of the biofilm in MSSA depends on ica genes, while in MRSA a biofilm can be formed in absence of both genes. The agrII allele was statistically significant associated with strong biofilm formation (p =0.001) and with agr dysfunction (p =0.030).

Purpose Rising Antibiotic Resistance has put the world in real threat. Methicillin resistant Staphylococcus aureus (MRSA), is a predominant cause of suppurative chronic skin and soft-tissue infections. Novel insights have focused the light on plant extracts. In this study, Ruta graveolens ethanolic active extract was tested for its potential anti-virulence activities in MRSA. Materials and Methods A total of 100 MRSA strains causing skin and soft tissue infections were isolated and antibiotic susceptibility testing was done. Ability to form biofilm was tested phenotypically. Furthermore, the antimicrobial activity of Ruta graveolens was evaluated followed by detection of its Minimum inhibitory concentration (MIC). The inhibitory activity of this extract on biofilm formation was investigated. Afterwards, we investigated its effect on the transcription of biofilm-related genes and mecA gene. Results All tested isolates were sensitive to Vancomycin and Linezolid while high resistance was noted with both Fusidic acid (83%) and Gentamicin (68%). (83%) of the isolates were biofilm producers. Ruta graveolens extract showed strong antimicrobial activity against the MRSA strains with MIC 0.78 mg/mL. At subinhibitory concentration (1/2 MIC), the extract had high biofilm inhibitory effects with mean inhibition (70%). Moreover, transcriptional analysis results showed that the mean percentages of inhibition in expression of mecA, icaA and icaD genes were 52.3%, 34.8% and 33.7%, respectively, in which all showed statistically significant difference ( p ≤ 0.05). Conclusion The current study proposes the ability of Ruta graveolens extract to reduce the biofilm formation and antibiotic resistance of MRSA through downregulation of some biofilm forming genes and mecA gene which confers resistance to B-lactam antibiotics. This may decrease our reliance on antibiotics and improve our ability to effectively treat biofilm-related skin and soft-tissue infections caused by MRSA.