1 – Centro Hospitalar Lisboa Central 2 – Laboratório de Patologia Clínica 3 – Secção de Microbiologia
- Congresso Internacional – poster
Objective: In this study, we describe an alternative bacterium identification approach from positive blood cultures incubated after a short period on solid medium, using VITEK MS.
Methods: For the purpose of this study, we considered only the blood cultures that became positive in BactalertTM equipment between 8h00 and 13h00 on each working day. These positive blood cultures were plated onto Columbia Agar 5% sheep blood and incubated immediately (n=95). VITEK MS bacterial isolates were performed at up to 3 different periods: 11h00, 13h00 and 15h00, trying a reliable identification to the
species level (99%). Bacterial isolates were picked up from the first section of the Petri dish even if macroscopic growth could not be seen. The control reading time was the overnight incubation (16h-18h) for definitive identification.
Results:The bacterial population was represented by more than 10 different species, being E.coli and K. pneumonia the most prevalent Gram negative, andS. hominis and S. epidermidis the most prevalent Gram positive. 80% (n= 76) of the samples were correctly identified on an average time around 3h of incubation. No extraction process was necessary to be performed in order to achieve these results. 20% (n=19) of samples didn’t achieve any identification or got a wrong identification. 95% of those (n= 18) were Gram positive, being 8 samples S. epidermidis. Four (n=4) of the samples were actually polymicrobial culture. Enterobactereacea had a reliable identification on VITEK MS after an average of 2h55 of plate incubation. P. aeruginosa were faster, having a reliable identification after 1h40 of plate incubation. For Gram positive, incubation time (3h-3h30) was very similar amongst the 3 big groups: Streptococci, Staphylococci and Enterococci.
|
Bacteria |
Samples with Correct Identification (n) |
Average incubation time on solid medium |
|
Enterobactereaceae |
34 |
2h55 |
|
Non Fermenteurs |
6 |
1h38 |
|
Staphylococci |
25 |
3h31 |
|
Enterococci |
4 |
3h13 |
|
Streptococci |
5 |
2h54 |
| Other Gram Positive | 2 | 6h02 |
| Total | 76 |
Conclusions: In conclusion, VITEK MS performed well, on positive blood cultures, after a short-term incubation on solid agar plates, providing very early and reliable identification without additional hands-on processing time and costs, both for Gram negative and Gram positive bacteria. Rapid identification of pathogens in the laboratory is important to guide treatment of the patient as early as possible. For this purpose, VITEK MS (MALDI-TOF) applied directly to positive blood cultures, after a short incubation period, represents a promising and simple approach to any Microbiology Lab.
Palavras Chave: BCG Vaccine; BCGitis, Low-level Isoniazid resistance