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Background: pseudomonas aeruginosa as an opportunistic pathogen is the most important infectious agent in hospital and has resistance to the common antibiotics. In this study, susceptibility of pseudomonas aeruginosa to quinolones and beta-lactams, and also relation of bacterial capsule and antibiotic resistance were assessed.
Material and methods: In this experimental study, 100 strains of pseudomonas aeruginosa from Imam Khomeini hospital were collected and its susceptibility to some of quinolones and beta lactams was determined on the basis of the minimum inhibitory concentration on agar. In order to detection mucoid and non-mucoid strain, capsule was detected by India- ink staining and alginate precipitation methods, and then relation of bacterial capsule and antibiotic resistance was evaluated.
Results: MIC method demonstrated 90% susceptibility to ofloxacin, 89% to ciprofloxacin, 59% to nalidixic acid, 43% to ceftizoxime and 39% to ceftriaxone. The susceptibility of these strains was also examined on the basis of disk diffusion agar on moler Hinton medium, and susceptibility to used antibiotics was as following: co-amoxiclave 0%, ceftizoxime 23%, ceftriaxone 29%, carbenicillin 48%, nalidixic acid 50%, Ticarecillin 53%, Ciprofloxacin 36%, ofloxacin 70% and norfloxacin 89%. All strains had alginate capsule and only diameter of capsules was different between strains.
Conclusion: This study showed that the method of disc diffusion has less accuracy compared to MIC in determining susceptibility to antibiotics.