Applicability of an in-house saponin-based extraction method in Bruker Biotyper matrix-assisted laser desorption/ionization time-of-flight mass spectrometry system for identifying bacterial and fungal species in positively flagged pediatric VersaTREK blood cultures

BACKGROUND/PURPOSE

Early identification of pathogens causing bloodstream infection (BSI) is critical for prompt administration of appropriate antimicrobial therapy.

METHODS

We used an in-house saponin-based extraction method to evaluate the performance of Bruker Biotyper MALDI-TOF MS system (MALDI Biotyper) for bacterial and fungal identification in 2013 positively-flagged VersaTREK blood culture bottles.

RESULTS

A total of 180 monomicrobial and 23 polymicrobial positive blood cultures were investigated. Among monomicrobial positive blood cultures, the MALDI Biotyper recognized 90.6% and 81.7% of organisms directly from the flagged blood culture bottles to the genus and species levels, respectively. The MALDI Biotyper also correctly characterized one of the polymicrobial organisms to the species level in 20 (87%) bottles and to the genus level in 21 (91.3%) bottles. The overall identification rate using our protocol was 90.6% (184/203) and 82.3% (167/203) for genus and species levels, respectively. Identification accuracy was higher for Gram-positive than Gram-negative organisms and was the lowest for yeasts. Score values of identification were ≥1.500 for 200 (98.5%) bottles, ≥1.700 for 195 (96.1%) bottles and ≥2.000 for 182 (89.7%) bottles. Moreover, 83.5% and 92% of the isolates were identified precisely to species and genus level with the lower cutoff score of 1.500. Using our protocol also helped identifying BSI pathogens 18-24 h earlier compared to the sub-cultured colonies.

CONCLUSION

Using Bruker MALDI Biotyper for identification of isolates directly from positive VersaTREK blood culture bottles, our in-house saponin-based protocol provided a more rapid turn-around time for correct identification of BSI pathogens than the conventional methods.

Evaluation of the automated Becton Dickinson MAX real-time PCR platform for detection of Pneumocystis jirovecii

AIM

We evaluated the performance of the automated quantitative BD MAX (Becton Dickinson) real-time PCR platform for detecting Pneumocystis jirovecii.

MATERIALS & METHODS

A total of 34 retrospective and 137 prospective samples were included.

RESULTS

Retrospectively, all (100%) positive samples were correctly detected by this platform compared with a nested PCR. Among prospective samples, the overall sensitivity, specificity, positive likelihood ratio and negative likelihood ratio were 92.6%, 94.5%, 17.0 and 0.1, respectively. All bronchoalveolar lavage fluid (BALF)/bronchial washing samples were correctly identified by this platform. Samples from patients with colonization had significantly higher median amplification cycle threshold values than patients with P. jirovecii pneumonia.

CONCLUSION

The quantitative BD MAX real-time PCR is a rapid and highly sensitive modality for detecting P. jirovecii, especially in samples from bronchoalveolar lavage fluid/bronchial washing fluid.

Distinct regulation of gene expression by prostaglandin F(2alpha) (PGF(2alpha)) is associated with PGF(2alpha) resistance or susceptibility in human granulosa-luteal cells

The effects of human chorionic gonadotrophin (HCG) and prostaglandin F(2alpha) (PGF(2alpha)) on regulation of human granulosa-luteal cell (GLC) function at different stages of differentiation (day 2 versus day 8 of culture) were studied. Expression of LH receptor mRNA and biosynthesis of progesterone were HCG dependent in human GLC at all stages (n = 6, P < 0.05). Steady-state concentrations of mRNA encoding for FP (a specific high-affinity plasma membrane receptor for PGF(2alpha)) were not dependent on, but were stimulated by, addition of HCG (10 IU/ml) or 8-bromo-cAMP (0.5 mmol/l) (n = 6, P < 0.05). Treatment with PGF(2alpha) (100 nmol/l) decreased FP mRNA concentration, but had no effect on LH receptor and cyclo oxygenase-2 (COX-2) expression on day 2 of cultured GLC (n = 8). As a result, the progesterone biosynthesis by GLC was not affected. On day 8, PGF(2alpha) induced FP and PGHS-2 expression and at the same time decreased LH receptor expression, resulting in inhibition of progesterone output by GLC. Our data demonstrated that early stage GLC (day 2 of culture) are resistant to PGF(2alpha)-induced inhibition of progesterone synthesis but underwent further differentiation and acquired luteolytic capacity after 8 days culture in vitro. We conclude that, via distinct gene regulation at different stages of differentiation, human GLC may become resistant or susceptible to PGF(2alpha)-induced luteolysis.