The role of vitek-2 automated system in identification and susceptibility testing of Gram negative rods in an Intensive Care Unit patients in Egypt
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- Category: Vol. 82, June 2014
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The role of vitek-2 automated system in identification and susceptibility testing of Gram negative rods in an Intensive Care Unit patients in Egypt, Dina M. Atef and Rania A. Ghonaim
Abstract
The performance of automated Vitek-2 system was evalu-ated for the identification and antimicrobial susceptibility testing (AST) of most common Gram-negative bacilli in in-tensive care unit patients directly from BacT/ALERT positive blood cultures bottles. Direct inoculation of the positive blood cultures with the Vitek cards ID-GNB and AST-GN71 was compared with the standard inoculation method based on the sub-culture of the positive blood culture to agar. We aimed to give the clinician with early information about the results of blood culture allowing a better prognosis and a reduced mortal-ity rate of the ICU patients. A total of 170 blood cultures from ICU patients’ clinical samples were investigated; of these, 165 (97.06%) strains were correctly identified to the species level, 1 (0.59%) strain was not identified. Results were compared with those of the reference method of API identification systems using a pure culture. It was found that 4 (2.35%) strains had been misidentified. The direct-identification reporting time of Vitek-2 was about 3hrs. Direct testing of susceptibility to 19 antibiotics, i.e., amikacin, ampicillin, ampicillin/sulbactam, az-treonam, cefazolin, ceftriaxone, ciprofloxacin, Extended-Spec-trum Beta-Lactamase (ESBL) (include: Cefepime, cefotaxime, ceftazidime, clavulanic acid), gentamicin, imipenem, mero-penem, moxifloxacin, nitrofurantoin, tigecycline, tobramycin and trimethoprim-sulfamethoxazole. AST was also performed by the broth microdilution (MB) method as a reference method. It was determined that the 3,135 organism-antibiotic combina-tions had an overall correct rate of 95.6%. The error rate was 4.4% overall, Only 22 (0.7%) gave severe errors (i.e., reported as sensitive by the Vitek-2 system but shown to be resistant by the MB method), 10 (0.3%) major errors (i.e., reported as resistant by the VITEK 2 system but shown to be sensitive by the MB method) and 106 (3.4%) minor errors (i.e., reported as sensitive or resistant with the Vitek-2 system and intermediate by the MB method or intermedicate with the Vitek-2 system and sensitive or resistant by the MB method).
Conclusion: Direct identification and antimicrobial sus-ceptibility testing with Vitek-2 system gave rapid and reliable results with shortening the turnaround time of microbiological laboratory by 24hrs which leads to a significant reduction of patient’s morbidity, mortality and medical care cost.