Naslov
Optimizing the method omitting cell lysis and protein extraction for identification of bacteria from positive blood cultures by matrix-assisted laser desorption/ionization time-of-fligt mass-spectrometry
(Optimizing the method omitting cell lysis and protein extraction for identification of bacteria from positive blood cultures by matrix-assisted laser desorption/ionization time-of-fligt mass-spectrometry)

Autori
Perše, Gabrijela ; Bošnjak Zrinka ; Mareković, Ivana

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, neobjavljeni rad, stručni

Skup
32nd European Congress of Clinical Microbiology and Infectious Diseases

Mjesto i datum
Lisabon, Portugal, 23.04.2022. - 26.04.2022

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
blood culture ; identification ; MALDI-TOF MS

Sažetak
Background Matrix-assisted laser desorption/ionization time-of-flight mass- spectrometry (MALDI-TOF MS) is widely used for fast identification of bacteria from blood cultures (BC). Several studies evaluated identification methods omitting blood cell lysis and protein extraction to reduce cost, hands-on time and to provide simplicity. We developed our own in-house method and made comparison to previously published protocols that used the same score criteria for species level identification (Table 1). Materials Total of 64 BC's flagged as positive in either BACTECTM FX system or BACT/Alert® VIRTUO® were collected between September and November 2019 at the University Hospital Centre Zagreb, Croatia, Zagreb. The positive BC's were processed according to our in- house method as described in Figure 1. Each sample was analyzed with MALDI Biotyper Microflex LT/SH in duplicate and the higher score was used for the analysis. Identification was considered succesful to the species and the genus level when the score of at least one of the spots was ≥2.0 and ≥1.7, respectively. Confirmation of identification was done using our routine diagnostic protocol with positive BC's subcultured on blood and chocolate agar and growing biomass used for MALDI-TOF MS identification. Results Our in-house protocol identified 67.2% (43/64) and 81% (52/64) of isolates to the species and genus level, respectively. Identification rate to the species level was higher for Gram- negative (83.3%) than for Gram-positive (53.0%) bacteria, expectedly. Among Enterobacterales all but one isolate of Salmonella spp. were identified to the species level (95.5%). For two samples no identification was found at either the species or the genus level (Staphylococcus capitis and Streptococcus dysgalactiae) (Table 2). There were no misidentifications in comparison to routine diagnostic identification. Conclusions In comparison to similar in-house protocols omitting cell lysis and protein extraction, we demonstrated a similar performance for the identification of Gram-negative and better performance for the identification of Gram- positive bacteria from positive BC's. This could be explained by including the additional wash step in the procedure. Although in-house protocols are fast, easy and inexpensive, extraction with methods as Sepsityper are the solution if we want to provide greater rate of precision for identification of Gram-positive bacteria.

Izvorni jezik
Engleski

Znanstvena područja
Kliničke medicinske znanosti

POVEZANOST RADA