ABSTRACT A real-time PCR assay previously developed for use on the Roche LightCycler platform was investigated as an alternative to culture for the direct detection of vancomycin-resistant enterococci (VRE) in clinical specimens. PCR primers and fluorescence resonance energy transfer hybridization probes specific for the vanA and vanB genes were combined in a multiplex real-time PCR assay performed directly with fecal material obtained by rectal swabbing and with enrichment broth samples. DNA was prepared from the rectal swabs and enrichment broths with a commercially available DNA preparation column designed specifically for use with fecal specimens. One hundred eighty duplicate rectal swabs were obtained from 42 patients who were previously found to be positive for VRE and who were being monitored for carriage of VRE. Direct and enrichment broth cultures were performed with one swab, while PCR was performed with the other swab as well as any corresponding presumptive positive enrichment broth. In total, 100 specimens from 30 patients remained positive for VRE by at least one method. The multiplex real-time PCR was positive for 88 enrichment broths of rectal swabs from 27 patients but for only 45 rectal swabs from 15 patients. Direct culture was positive for VRE for only 43 specimens from 11 patients, while enrichment broth culture was positive for VRE for 75 specimens from 22 patients. Inhibition studies for the multiplex real-time PCR assay, performed by spiking the DNA extracts from 50 negative rectal swabs and the corresponding enrichment broths with between 1 and 10 CFU of a VanB Enterococcus faecium strain, detected inhibition rates of 55.1 and 10%, respectively. PCR performed directly with enrichment broths was found to be significantly more sensitive than enrichment broth culture ( P < 0.025). Negative samples were identified significantly earlier by PCR than by culture alone.
The relationship between quantitative PCR (COBAS Amplicor CMV Monitor, Roche Diagnostics) and quantitative antigenemia (Monofluor pp65, Sanofi Diagnostics) was examined for monitoring CMV viraemia. A total of 469 specimens from immunocompromised haematology and solid organ transplant patients were tested by quantitative antigenemia and qualitative PCR. Quantitative PCR (QPCR) was performed on the 245 specimens in which CMV DNA was detected by qualitative PCR. To exclude any effect due to specific anti-CMV treatment, analysis of antigenemia and QPCR results was only performed on the 164 of 245 specimens collected from patients not on ganciclovir or foscarnet treatment. Forty seven specimens had <400 CMV copies/mL and a negative antigen result, four specimens were antigen positive (all between 1 to 10 positive CMV cells/2 x 10(5) leucocytes) and had <400 CMV copies/mL. Fifty-one specimens had a CMV viral load > or = 400 copies/mL and a negative antigen result and 62 specimens had a CMV viral load > or = 400 copies/mL and a positive antigen. The viral load was shown to be as high as 43,000 copies/mL in some patients with a negative antigen and occurred in non-neutropenic patients. The correlation coefficient for antigen and QPCR results for specimens from bone marrow transplant patients, was 0.69 with an average CMV viral load of 3,200 copies/mL (SEM = 800) and an average antigen of nine positive CMV cells/2 x 10(5) leucocytes (SEM = 3). In the corresponding solid organ transplant group, the correlation coefficient for antigen and QPCR results was 0.71 with an average CMV viral load of 9,900 copies/mL (SEM = 2,100) and an average antigen of 26 positive CMV cells/2 x 10(5) leucocytes (SEM = 6). Both the average viral load and the average antigen result in specimens from solid organ transplant patients, were significantly higher than the average viral load and antigen result in the corresponding group of bone marrow transplant patients (Two-Sample-for-Means z-Test, P = 0.001 and P = 0.003, respectively). The differences in the kinetics of the two assays in monitoring CMV and their ability to predict CMV disease was also assessed in a sub-group of patients. In conclusion, the two assays used in this study do not always show parallel changes in CMV viral load, but may be complementary for the diagnosis and management of CMV disease. The observation that non-neutropenic patients can have a high viral load in plasma and a negative antigenemia has implications for laboratories using antigenemia alone to monitor patients for CMV disease.
Abstract Objective: The aim of the present study was to determine if the quantification of bacterial 16S rDNA could be clinically useful in predicting patients at increased risk of developing septic shock. Methods: A retrospective study of patients with positive blood cultures taken on arrival to the ED. An EDTA sample was collected simultaneously with blood cultures and assayed by polymerase chain reaction to quantitate the bacterial 16S rDNA load. Descriptive and clinical data were collected from the medical record and this was blinded to the 16S rDNA result. Subsequently, the 16S rDNA result was compared with illness severity markers including septic shock and death to determine the relationship between the 16S rDNA load and illness severity. Results: 98 patients (mean age 61 ± 20 years, range 18–92) with positive blood cultures were studied, most commonly growing Escherichia coli ( n = 25) and Staphylococcus aureus ( n = 23). 16 (16%) died. There were 42 (43%) 16S rDNA positive patients. A high 16S rDNA load was associated with an increased risk of developing delayed septic shock (OR 21.9, 95% CI 2.5–192.6) in comparison with either a low or negative 16S rDNA load; with a mortality OR 4.6 (95% CI 0.9–23.5). Conclusions: The quantitative assay for 16S rDNA might be a useful screening tool to detect severe sepsis in those whom it might not be clinically suspected. However, prospective studies are required to further assess the clinical usefulness of this assay.
Differences in the hepatitis C virus (HCV) genotype influence the severity of HCV related liver disease and response to interferon therapy. HCV infection is frequent in Australian haemophilia patients who have been exposed repeatedly to multiple HCV genotypes through non HCV virally inactivated clotting factor concentrates. The distribution of the various HCV genotypes in Australian haemophilia patients is unknown.To examine the HCV genotype distribution and clinical features of HCV associated liver disease in Australian haemophilia patients.Forty patients with bleeding disorders who were known to be both HCV antibody and polymerase chain reaction (PCR) positive were evaluated by direct sequencing of the PCR products for the HCV genotype.Genotype 1 was found in 65% of patients (26/40), type 2 in 5% (2/40) and type 3 in 30% (12/40). No genotypes 4 to 6 were found. There was no association between the HCV genotype and the severity of haemophilia, alanine transaminase levels, or the presence of portal hypertension. Unlike European, Asian and American studies where the majority of type 1 infection is subclass 1b, in Australian haemophilia patients it is subclass 1a (73%-19/26) which may have a better prognosis and response to interferon.Despite patients with haemophilia being exposed to multiple HCV genotypes, it appears that there is no selection advantage of one genotype over another. Australian haemophilia patients with HCV have a different genotype distribution to that reported in other countries and care should be observed in interpreting non Australian studies concerning HCV.
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