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Antibiotic Resistance and the Frequency of Extended-Spectrum B-Lactamase in Acinetobacter baumannii Isolated from Clinical Samples through Phenotypic Methods

Author(s): Somayeh Vafaei | Reza Mirnejad | Nour Amirmozafari | Abbasali Imani Fooladi | Faramarz Masjedian

Journal: Iranian Journal of Infectious Diseases and Tropical Medicine
ISSN 1680-0192

Volume: 18;
Issue: 61;
Start page: 39;
Date: 2013;
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Keywords: Acinetobacter baumannii | Extended-spectrum β-Lactamase (ESBL) | Drug resistance | Antibiogram | Combined disk

AbstractBackground and objectives: Nowadays Acinetobacter baumannii is as one of the problematic opportunistic pathogens, especially in intensive care because of the incidence of drug-resistant strains in the world. The purpose of current study was to define the antibiotic susceptibility patterns and detect the prevalence of producing strains of extended-spectrum β-lactamase (ESBL) in A. baumannii isolates which had been isolated from clinical samples with combined disk test.Materials and methods: This study was conducted in 3 major hospitals in Tehran on 500 clinical samples during 6 months. After identification of isolates in species level using cultural and biochemical methods, in order to determine sensitivity of 100 isolates of A. baumannii to 11 antibiotics, the susceptibility tests were carried out according to CLSI guidelines using disk diffusion method. Also MIC (Minimum inhibitory concentrations) was determined for cefepime and ceftazidime, and finally to identify of producing strains of ESBL was applied phenotypic method of combined disk. Results: In this survey, 100 A. baumannii strains, 30 A. lwoffii strains and other Acinetobacter species were isolated from patients. The majority of isolates were from blood specimens. Isolates of A.baumannii revealed the highest resistance to cefepime, ceftriaxone, amikacin, imipenem, piperacillin - tazobactam, meropenem, gentamicin, tobramycina and tetracycline, respectively. Ampicillin - sulbactam and polymyxin B considered as effective drugs in this study. Multi-drug resistance in these strains was 70%. The Total isolates studied the Minimum inhibitory concentrations of ceftazidime in 84% samples was MIC ≥ 128 μg/ml and Minimum inhibitory concentrations of cefepime in 91% samples was MIC≥ 128 μg/ml. According to the results of combined disk test, 20% of total samples were demonstrated to be ESBL positive.Conclusion: Regarding to produce of ESBL in this bacterium and possibility of transformation of coding genes to the other bacteria, reconsideration in antibiotics consumption patterns and as well as more attention to nosocomial infections control criteria are inevitable.
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