Vitek GPS card susceptibility testing accuracy using direct inoculation from Bactec 9240 blood culture bottles

The emergent need for antimicrobial susceptibility testing (AST) data for the therapy of bacteremic patients has led to the development of rapid methods and local procedure modification of some commercial AST products such as the direct inoculation from blood culture systems. We compared the Vitek G...

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Bibliographic Details
Published in:Diagnostic microbiology and infectious disease 1996-02, Vol.24 (2), p.109-112
Main Authors: Howard, Wanita J., Buschelman, Barry J., Bale, Martha J., Pfaller, Michael A., Koontz, Frank P., Jones, Ronald N.
Format: Article
Language:English
Subjects:
Antibacterial agents
Antibiotics. Antiinfectious agents. Antiparasitic agents
Bacteremia - microbiology
Biological and medical sciences
Humans
Medical sciences
Microbial Sensitivity Tests - methods
Pharmacology. Drug treatments
Staphylococcus aureus - drug effects
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Summary:The emergent need for antimicrobial susceptibility testing (AST) data for the therapy of bacteremic patients has led to the development of rapid methods and local procedure modification of some commercial AST products such as the direct inoculation from blood culture systems. We compared the Vitek GPS card results using direct and standardized inoculation with a reference broth microdilution method for 112 consecutive staphylococcal bloodstream infections (seven drugs). Among the 28 Staphylococcus aureus strains, 0%–3.6% total error/drug was observed with both Vitek inoculation procedures. However, the only oxacillin-resistant strain was not detected (100% true very-major error). For 84 coagulase-negative staphylococci (CNS), the direct inoculation procedure had an 11.9% very-major error rate for oxacillin, ampicillin-sulbactam, and cephalothin, plus 4.8% very-major error rate for ciprofloxacin and trimethoprim-sulfamethoxazole (total error rate 4.8%–16.7% for five of seven drugs compared). The Vitek direct inoculation procedure routinely missed 20.4% of oxacillin-resistant CNS strains. The use of Vitek direct inoculation procedures for staphylococcal bloodstream infection isolates (from Bactec 9240 cultures) produced serious false-susceptible results; this procedure should be avoided in favor of routine package insert-recommended Vitek procedures or other reference-quality overnight incubation susceptibility tests.
ISSN:0732-8893
1879-0070
DOI:10.1016/0732-8893(95)00273-1