Evaluation of negative results of BacT/Alert 3D automated blood culture system.
Although automated continuous-monitoring blood culture systems are both rapid and sensitive, false-positive and false-negative results still occur. The objective of this study, then, was to evaluate negative results occurring with BacT/Alert 3D blood culture systems. A total of 1032 samples were cultured with the BacT/Alert 3D automated blood culture system, using both aerobic (FA) and anaerobic (FN) [corrected] media, and 128 of these samples yielded positive results. A total of 904 negative blood samples were then subcultured in 5% sheep blood agar, eosin methylene blue, chocolate agar, and sabouraud-dextrose agar. Organisms growing on these subcultures were subsequently identified using both Vitek32 (bioMerieux, Durham, NC) and conventional methods. Twenty four (2.6%) of the 904 subcultures grew on the subculture media. The majority (83.3%) of these were determined to be gram-positive microorganisms. Fourteen (58.3%) were coagulase-negative staphylococci, two (8.3%) were Bacillus spp., one (4.2%) was Staphylococcus aureus, and one (4.2%) was identified as Enterococcus faecium. Streptococcus pneumoniae and Neisseria spp. were isolated together in two (8.3%) vials. Gram-negative microorganisms comprised 12.5% of the subcultures, of which two (8.3%) were found to be Pseudomonas aeruginosa, and one (4.2%) was Pseudomonas fluorescens. The other isolate (4.2%) was identified as Candida albicans. We conclude that the subculture of negative results is valuable in the BacT/Alert 3D system, especially in situations in which only one set of blood cultures is taken.
Department of Microbiology and Clinical Microbiology, Faculty of Medicine, Gaziantep University, Gaziantep, Turkey. kocogluesra@yahoo.com
M Esra
ME
Kocoglu
Aysen
A
Bayram
Iclal
I
Balci
D001331:Automation; D016470:Bacteremia / Q000175:diagnosis*; D001419:Bacteria / Q000254:growth & development / Q000302:isolation & purification*; D001431:Bacteriological Techniques; D001769:Blood / Q000382:microbiology*; D003470:Culture Media; D005188:False Negative Reactions; D006801:Humans; D011933:Reagent Kits, Diagnostic
D003470:Culture Media; D011933:Reagent Kits, Diagnostic