Several components of sheep blood extensively catabolize nucleosides, including thymidine. Part of the radioactivity from tritiated thymidine, in whole blood cultures, is quickly rendered unincorporable as the compound is metabolized to thymine and further breakdown products. Thus, cells continue to proliferate without incorporating radioactivity from the medium. Furthemore, variability in the degree of catabolism varied from animal to animal, so that neither measurement of the depletion of radioactivity from the medium nor measurement of the amount of label incorporated into cultures can be used as a quantitative index of the cell proliferation or immunocompetence.
In this study, we tested the advantages of TaqMan real time PCR technique and compare it to conventional methods using serum samples from patients with different clinical forms of brucellosis. A total of 50 patients were included in the study. Blood culture using BACTEC 9240 system, Standard Wright's tube agglutination, and real time PCR methods were used. Control blood samples from 30 people with no history of brucellosis or exposure to Brucella spp. were examined too. Serological assay was positive for 49 patients (98%). Forty-four (88%) of the 50 patients had a positive PCR result, whereas Brucella spp were isolated from blood cultures of 18 patients (36%). STA test was all positive for focal brucellosis. Real time PCR test was positive in 9 patients with focal disease (90%), whereas blood culture was positive only in 4 patients (40%). The sensitivity, specificity, positive and negative predictive values of the real time PCR method were calculated as 88%, 100%, 100%, and 83%, respectively. Our results suggest that the high sensitivity and specificity of real time PCR method make it a useful tool for diagnosis of brucellosis with different clinical manifestations.
Coagulase-negative staphylococci (CoNS) have become the most often isolated bacteria from blood culture, spinal fluid and respiratory tracts of neonates. These nosocomial strains are often resistant to oxacillin and other antibiotics (macrolides, aminoglycosides and fluorochinolones). 50 multidrug resistant CoNS strains isolated from bloodstream neonatal infections were tested for sensitivity to 23 lytic staphylococcus bacteriophages. No lytic patterns for 19 of the phages were observed. Phages P4, A3R and 676/Z were active against 46%, 54% and 56% of the strains, respectively. In general, 60% of CoNS isolates were susceptible to one or more of the staphylococcus bacteriophages.
The gold standard in microbiological diagnostics of bacteremia is a blood culture in automated systems. This method may take several days and has low sensitivity. New screening methods that could quickly reveal the presence of bacteria would be extremely useful. The objective of this study was to estimate the effectiveness of these methods with respect to blood cultures in the context of antibiotic therapy. Blood samples from 92 children with sepsis were analyzed. Blood cultures were carried out in standard automated systems. Subsequently, FISH (Fluorescent In-Situ Hybridization) and nested multiplex-real-time-PCR (PCR) were performed. Blood cultures, FISH and PCR yielded positive results in 18%, 39.1%, and 71.7% of samples, respectively. Significant differences were found between the results obtained through culture before and after induction of antibiotherapy: 25.5% vs. 9.7%. There was no significant difference in FISH and PCR results in relation to antibiotics. The three methods employed demonstrated significant differences in detecting bacteria effectively. Time to obtain test results for FISH and PCR averaged 4–5 hours. FISH and PCR allow to detect bacteria in blood without prior culture. These methods had high sensitivity for the detection of bacteremia regardless of antibiotherapy. They provide more timely results as compared to automated blood culture, and may be useful as rapid screening tests in sepsis.
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