Abstract
Background and aims: Staphylococcus aureus is considered as a frequent cause of infections. Therefore, antibacterial agents including β-lactam are normally used to treat these infections while the emergence of antibiotic resistance is one of the major clinical problems in this respect. Accordingly, combination antibacterial therapy is one way to alleviate this problem. As a result, the present study aimed to investigate the combined effects of vancomycin and methicillin on clinical isolates of methicillin-resistant S. aureus (MRSA) and methicillinsensitive S. aureus (MSSA). In addition, a series of follow-up studies were performed to evaluate the antibacterial activity. Methods: The current cross-sectional study was conducted on 40 hospitalized patients from various clinical samples such as pus/wound swabs, blood, urine and sputum during a 6-month period in 2017. To this end, the antibacterial activities of vancomycin and methicillin, alone and in combination were investigated against MRSA and MSSA. Eventually, the inhibitory effects of vancomycin and methicillin alone and in combination were studied on the growth profile of MRSA and MSSA, as well as the expression of mecA gene. Results: Based on the results, the significant synergistic and partial synergistic activity with fractional inhibitory concentration (FIC) and fractional bactericidal concentration (FBC) indexes ranged from 0.27-0.938 and 0.313-0.844, respectively, in the combination of vancomycin and methicillin in MRSA and MSSA isolates. Further, the obtained data indicated that the combination of vancomycin and methicillin had a synergistic effect against MRSA isolates (P<0.01). The expression levels of the mecA gene were down-regulated by 5.25- fold in the combination of vancomycin and methicillin in MRSA isolate (P<0.001). Conclusion: In general, these events may reflect the potential uses of vancomycin and methicillin combination against MRSA. However, a greater understanding of the underlying molecular mechanisms of vancomycin and methicillin in combination could contribute to the development of therapeutic strategies.
Highlights
Staphylococcus aureus is a human commensal and a widespread cause of life-threatening systemic infections
A number of 30 (75%) out of 40 clinical isolates were documented as the methicillin-resistant S. aureus (MRSA) while 10 (25%) clinical isolates were identified as methicillinsensitive S. aureus (MSSA)
The mechanisms of antibiotic activity of the methicillin against S. aureus possibly act by the inhibitory effects of the PBPs that are involved in the synthesis of peptidoglycan, causing cell wall synthesis and halting cell growth [34]
Summary
Staphylococcus aureus is a human commensal and a widespread cause of life-threatening systemic infections. The β-lactam antibiotics are regarded as the antibacterial drugs of choice for treating the S. aureus infections. Their target mechanisms inhibit the synthesis of bacterial cell walls and lead to bacterial cell death [1,2]. Antibacterial agents including β-lactam are normally used to treat these infections while the emergence of antibiotic resistance is one of the major clinical problems in this respect. Methods: The current cross-sectional study was conducted on 40 hospitalized patients from various clinical samples such as pus/wound swabs, blood, urine and sputum during a 6-month period in 2017 To this end, the antibacterial activities of vancomycin and methicillin, alone and in combination were investigated against MRSA and MSSA.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
