Study of drug resistance of Staphylococcus aurous and Pseudomonas aeruginosa strains isolated from environmental samples of Hamadan educational hospitals in 2017 using disk diffusion and minimum inhibitory concentration

Background: Staphylococcus aureus and Pseudomonas aeruginosa are the most important bacteria causing the nosocomial infections, which are resistant to most of the antibiotics. The aim of this study was to evaluate the drug resistance of S. aureus and P. aeruginosa strains isolated from environmental samples of Hamedan educational hospitals using disk diffusion and minimum inhibitory concentration (MIC) methods. Materials and Methods: In this descriptive cross-sectional study, 400 samples were collected from Hamedan educational hospitals. To assess the antibiotic susceptibility of 10 common antibiotics, the agar dilution (Kirby-Bauer) method was used. Also, to determine the MIC of S. aureus and P. aeruginosa, vancomycin and ciprofloxacin antibiotics were used. Results: From a total of 400 samples, 39 (9.7%) isolates were P. aeruginosa and 28 (7%) were S. aureus. Staphylococcus aureus showed the highest resistance to ofloxacin (82.1%) and the highest drug resistance to P. aeruginosa was related to meropenem (82%). Also, the highest MIC and maximum bactericidal concentration (MBC) for S. aureus to vancomycin were 128 and 256, respectively. In P. aeruginosa, the highest MIC and MBC to ciprofloxacin were 128 and 256, respectively. Conclusion: Staphylococcus aureus and P. aeruginosa showed the highest resistance to ofloxacin and meropenem, respectively. Considering the rapid increase of antibiotic resistance, accurate evaluation of the antibiotic resistance pattern of the bacteria is required