Rapid Antimicrobial Susceptibility Testing of Isolates from BACTEC Blood Culture Bottles by Direct Inoculation

• Main Author: Zeki YUMUK
• Format: Article
• Language: English
• Published: Bilimsel Tip Yayinevi 2003-03-01
• Series: Flora Infeksiyon Hastalıkları ve Klinik Mikrobiyoloji Dergisi
• Subjects: BACTEC blood culture bottles; Direct antimicrobial susceptibility tests; Weighted kappa
• Online Access: http://www.floradergisi.org/getFileContent.aspx?op=REDPDF&file_name=2003-8-1-058-064.pdf

This study was undertaken to test the accuracy of 5 h and overnight reading of disk diffusion tests that were inoculated directly from positive BACTEC® 9050 blood culture bottles. Ninety six specimens confirmed as monobacterial by Gram staining procedure were included in this study. Eighty seven of the 96 specimens were blood, six were pleural fluid and three of them were belongs to cerebrospinal fluid (CSF). According to the results of the Gram staining procedures 80% the specimens had gram-positive, 20% specimens had gram-negative bacteria. Considering the Gram staining properties of the microorganisms, direct susceptibility tests were performed with 822 antibiotic disks. The results from zone size interpretations of direct susceptibility tests read after incubation for 5 and overnight were compared with the interpretations from standard diffusion test incubated for 18 h. There were two very major discrepancies in tests with gram-positive organisims: One was due to Staphylococcus aureus culture, and other was due to on a Staphylococcus epidermidis culture read after 5 h incubation. Beside, the most discrepancies in gram-positive organisims were seen with coagulase-negative staphylococcus. There were no very major discrepancy in direct tests with cultures read after overnight incubation. In gram-negative organisms, the two very major discrepancies that were observed at the fifth hours of the incubation were related to Enterobacter sakazakii and Serratia marcescens. Moreover, the most of the discrepancy were found at S. marcescens. Regarding to the antibiotic disks that were used in the direct test, the most of the discrepancies were found at 29% in chloramphenicol and 36% in ciprofloxacin. Considering the overall agreement, the 18th hour of incubations seems more reliable than the 5th hours of incubation. By using the advantages of the BACTEC blood culture bottles, direct susceptibility tests could be done time savingly. The agreement were found to be perfect (weighted kappa: 0.891-0.960)