SUMMARYA total of 316 samples of nasopharyngeal aspirate from infants up to two years of age with acute respiratory-tract illnesses were processed for detection of respiratory syncytial virus (RSV) using three different techniques: viral isolation, direct immunofluorescence, and PCR. Of the samples, 36 (11.4%) were positive for RSV, considering the three techniques. PCR was the most sensitive technique, providing positive findings in 35/316 (11.1%) of the samples, followed by direct immunofluorescence (25/316, 7.9%) and viral isolation (20/315, 6.3%) (p < 0.001). A sample was positive by immunofluorescence and negative by PCR, and 11 (31.4%) were positive only by RT-PCR. We conclude that RT-PCR is more sensitive than IF and viral isolation to detect RSV in nasopharyngeal aspirate specimens in newborn and infants.
Reimmunization guidelines have recommended the inactivated HAV vaccine for hematopoietic stem cell transplant (HSCT) recipients living in or traveling to areas where hepatitis A is endemic. As a shift from high to medium hepatitis A endemicity has been observed in several countries in Latin America, we conducted a retrospective study to evaluate the prevalence of hepatitis A pre-bone marrow transplant (BMT) and the loss of specific antibodies in consecutive stored serum samples from 77 BMT recipients followed up from 82 to 1530 days. The prevalence of HAV antibodies was 92.2% before BMT. As vaccine was not available in Brazil when the samples were taken, it was assumed that this prevalence reflects natural infection. Survival analysis showed that the probability of becoming seronegative was 4.5% (72.6%), 7.9% (73.4%), 10.1% (74.0%), 23.4% (79.6%) at 1, 2, 3 and 4 years after transplant, respectively. The loss of HAV antibodies was significantly associated with longer follow-up (P ¼ 0.0015), younger age (P ¼ 0.049) and acute graft-versus-host disease (P ¼ 0.035). As most reimmunization protocols start around day þ 365, in developing countries with similar HAV endemicity, BMT recipients should have serological screening before HAV vaccination and the inactivated vaccine should be advised to those seronegative.
In the past 2 decades, dengue has reemerged in Brazil as a significant public health problem. Clinicians demand a diagnostic test with high sensitivity that is applicable during the early symptomatic phase. We aimed to test two distinct molecular methods on samples from suspected dengue cases during an outbreak in Central Brazil. Acute-phase serum specimens from 254 patients suspected of having dengue were collected during 2005 in the city of Goiânia, Central Brazil. Samples were blindly evaluated by real-time and multiplex PCR in addition to routine immunoglobulin M serology and virus culture. Overall, acute dengue was confirmed by serology, multiplex PCR, or virus isolation for 80% of patients (203/254). Another four patients presented real-time PCR-positive results as the unique marker of dengue. Higher real-time PCR positivity levels and viral loads were observed in the early symptomatic phase of disease (<5 days) than after this period. Multiplex and real-time PCR assays presented a high kappa agreement (0.85). According to multiplex PCR, 60 samples harbored dengue virus type 3 (DEN-3), 4 samples harbored DEN-2, and 1 sample displayed a pattern compatible with a double infection with DEN-2 and -3. The dengue virus real-time kit was found to be practical and adjustable for high throughput, to display the best performance in the early symptomatic phase of dengue cases, and to be valuable for confirming dengue diagnosis in a timely manner.Dengue reemerged in Brazil in the 1990s as a significant public health problem, with thousands of cases, the introduction of new serotypes (dengue virus type 2 [DEN-2] and DEN-3), and hemorrhagic cases, including casualties (7,8,10).The confirmatory diagnosis of dengue is routinely performed by an immunoglobulin M (IgM) test on samples collected 1 week after the onset of symptoms. This is an "a posteriori" analysis, of limited use for prompt diagnosis of the patient during the early symptomatic phase. In theory, molecular tests are able to fulfill this purpose during the window period, by directly assessing the presence of viral RNA in plasma/serum samples from subjects with suspected dengue. Actually, reverse transcriptase PCR (RT-PCR) was found extremely practical in the recent outbreak of severe acute respiratory syndrome, when medical staff could quickly avoid the adoption of quarantine measures for dengue RNA-positive patients (1).Several RT-PCR methods for dengue RNA detection, including both conventional and real-time PCR, have been described in the literature (11). "In-house" methods usually show excellent performance but are hard to transfer to other laboratories successfully. This variability in results derives from the differences in suppliers, thermocyclers, and technician skills among laboratories. Commercial kits represent an alternative that can guarantee a certain homogeneity in results, which is important in establishing testing procedures to be adopted by many centers. Also, it is impossible for in-house assays to achieve the level of quality control of comm...
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