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Indian Journal of Medical Microbiology, Vol. 25, No. 4, October-December, 2007, pp. 435-436 Correspondence A report of Pseudomonas aeruginosa antibiotic resistance from a multicenter study in Iran Boroumand MA, Esfahanifard P, Saadat S, Sheihkvatan M, Hekmatyazdi S, Saremi M, Nazemi L Clinical Laboratory and Pathology Department, Tehran Heart Center, Medical Sciences/University of Tehran, Jalal Al Ahmad and North Kargar Cross, Tehran Correspondence Address: Clinical Laboratory and Pathology Department (MAB, PEF, SS, MS, LN), Tehran Heart Center, Medical Sciences/ University of Tehran, Jalal Al Ahmad and North Kargar Cross; and Reference Laboratories of Iran Research Center (SHY, MS), 1411713138 Tehran, Iran. Email: maboroumand@yahoo.com. Date of Submission: 14-Mar-2007 Code Number: mb07127 Dear Editor, The importance of the microbiology laboratory in hospital-based infection control programmes is well established. The role of the laboratory in infection surveillance, in the management of antimicrobial resistance and in outbreak investigation is also highlighted. Many different methods are available for bacterial susceptibility testing, including disk diffusion, E -test and microdilution procedures. The E -test is a new, continuous gradient diffusion test for MIC determination, [1] which has gained acceptance as a method for MIC determination and is less labour-intensive than the microdilution methodology. [2] Imipenem is a potent agent for the treatment of infections due to multidrug resistant Pseudomonas aeruginosa . Currently, resistance to imipenem is an increasing problem among these bacterial isolates. [3] According to the importance of antibiotic resistance of P. aeruginosa as one of the most important causes of healthcare-associated infection in our country, we tested the activity of imipenem by E -test against P. aeruginosa and compared the outcome with ciprofloxacin and ceftazidime. In this study, a total of 142 recent clinical isolates from three university hospitals with more than 400 beds each, located in Tehran were tested against a wide a range of imipenem, ciprofloxacin and ceftazidime. The strains were tested for antibiotic susceptibility by three methods: E -test, disk diffusion and microdilution broth technique. The percentages of P. aeruginosa isolates susceptible to ciprofloxacin and ceftazidime by disc diffusion test were 69 and 58.5%, respectively, compared to 64.8 and 64.1% with E -test and 56.5 and 55.6% with microdilution test, whereas the percentage of bacteria susceptible to imipenem by disk diffusion and E -test were 94.4 and 90.1%, respectively. Fifty percentile MIC (MIC 50 ) for imipenem, ciprofloxacin and ceftazidime in E -test were 2, 0.35 and 3, whereas 90 percentile MIC (MIC 90 ) for these antibiotics in E -test were 5.4,> 32 and> 256, respectively. A significant relationship between susceptibility of P. aeruginosa and type of antibiotic was seen in E -test (imipenem, 90.1%; ciprofloxacin, 64.8%; ceftazidime, 64.1%; P < 0.0001). Considering microdilution broth technique as a gold standard test, sensitivity and specificity of E -test were 89.24 and 95.00%, respectively. Interpretation of microdilution and E -test results showed almost perfect agreement, with kappa value of 0.8466 (95% CI: 0.7743-0.9188). This study has assessed the use of three different tests for determining imipenem, ciprofloxacin and ceftazidime MICs, namely: disk diffusion, microdilution and E -test. In this study, we found a difference between three antibiotics in determining susceptibility of P. aeruginosa in E -test. We found lower susceptibility to ciprofloxacin and ceftazidime than other studies; [4],[5] however, we also showed high susceptibility of P. aeruginosa to imipenem in E -test. In our study, the outcome of E -test as opposed to disk diffusion showed that susceptibility of P. aeruginosa to any selective antibiotic (imipenem, ciprofloxacin or ceftazidime) in E -test was higher than disk diffusion. We also obtained almost perfect agreement between E -test and microdilution. Similar to our study, in the Bonaventura study, overall qualitative agreement between these tests was 81.2% for ceftazidime, 93.7% for ciprofloxacin and 88.7% for imipenem. [5] Kelly et al , found the similar results with 95% agreement for cephalosporin. [1] P. aeruginosa shows high antimicrobial resistance in this multicentre study; therefore, it is necessary to implement certain policies to prevent antimicrobial resistance and establish a national programme and strategy to gather data centrally and use sensitive and specific tests to detect this bacterium. This research has supported by a grant from Medical sciences/ University of Tehran. References
Copyright 2007 - Indian Journal of Medical Microbiology |
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