Resumen

BLANCO, María Alejandra; CASIMIR, Lidia  y  LOPARDO, Horacio Angel. Identification and antimicrobial susceptibility of gram-negative bacilli: Evaluation of the use of automatic system directly from blood culture bottles. Acta bioquím. clín. latinoam. [online]. 2008, vol.42, n.1, pp.5-10. ISSN 0325-2957.

Reducing the turnaround time of laboratory diagnosis of bacteremia by means of blood cultures is of paramount importance to perform an appropriate clinical management of septic patients. In the present study, the performance of Vitek system for identification and antimicrobial susceptibility and disk diffusion antibiotic susceptibility method, directly from positive blood culture bottles, were evaluated. During one year, 101 positive bottles with gram-negative bacilli (71 Enterobacteriaceae and 26 non-fermenting gram-negative rods) were selected at random, and identification and antimicrobial susceptibility were studied. Identification obtained using Vitek system directly from the bottles has been compared to conventional biochemical tests with previously isolated bacteria. In a similar way, results of antimicrobial susceptibility have been compared to those obtained by agar dilution method. A good identification at species level was obtained for 86% of Enterobacteriaceae while 14% could not be identified. Almost ninety three percent of non-fermenting gram-negative rods were correctly identified with 3.8% badly identified, and 3.8% not identified. Global concordance with the reference method in susceptibility was 92.7% for Vitek system and 89.9 for disk diffusion method. very major (0.1% and 0.4%), major (2.4% and 1.3%) and minor (7.6% and 5.5%) errors were found for the disk diffusion method and Vitek system respectively. Vitek results obtained from direct inoculation of blood culture bottles containing gram-negative bacilli were satisfactory for identification as well as for antimicrobial susceptibility. The disk diffusion method directly performed from the bottles also showed acceptable results. However the advantage of Vitek system was its ability to significantly reduce the turnaround time.

Palabras clave : Identification; Antimicrobial susceptibility; Blood cultures; Vitek.

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