Detection of respiratory syncytial virus in clinical specimens by viral culture, direct and indirect immunofluorescence, and enzyme immunoassay

Genetic diversity in the G protein gene of group A human respiratory syncytial viruses circulating in Riyadh, Saudi Arabia

Human respiratory syncytial virus (HRSV) is a frequent cause of hospitalization and mortality in children worldwide. The molecular epidemiology and circulation pattern of HRSV in Saudi Arabia is mostly uncharted. In the current study, the genetic variability and phylogenetic relationships of HRSV type A strains circulating in Riyadh Province were explored. Nasopharyngeal aspirates were collected from hospitalized children with acute respiratory symptoms during the winter-spring seasons of 2007/08 and 2008/09. Among 175 samples analyzed, 39 (22.3 %) were positive for HRSV by one-step RT-PCR (59 % type A and 41 % type B). Propagation of positive samples in HEp-2 cells permitted the recovery of the first Saudi HRSV isolates. Genetic variability among Saudi HRSV-A strains was evaluated by sequence analysis of the complete attachment (G) protein gene. The nucleotide sequence was compared to representatives of the previously identified HRSV-A genotypes. Sequence and phylogenetic analysis showed that the strains examined in this study were very closely related at both the nucleotide and amino acid level, and all of them are clustered in the GA2 genotype (and mostly belonged to the NA-1 subtype). A total of 23 mutation sites, 14 of which resulted in an amino acid change, were recorded only in Saudi strains. This is the first report on genetic diversity of HRSV-A strains in Saudi Arabia. Further analysis of strains on a geographical and temporal basis is needed to fully understand HRSV-A circulation patterns in Saudi Arabia.

Rapid detection of oculopathogenic adenovirus in conjunctivitis

Ocular adenovirus (Ad) infections occur throughout the world in both sporadic and epidemic forms. Accurate laboratory diagnosis of Ad in conjunctival samples is always valuable. The present study was carried out to explore the presence of Ad as a causative agent in clinically suspected viral conjunctivitis and to compare the performance of conventional virus isolation on cell cultures, direct detection of Ad antigens in conjunctival cells by a direct fluorescence assay, Ad DNA detection by polymerase chain reaction (PCR), and specific IgM measurement by ELISA. Samples included scrapes from conjunctiva. Scrapes were subjected to study by direct immunofluorescence stain, culture on the Hep-2 cell line, and PCR for Ad detection. Blood samples were also taken and subjected to study for specific anti-Ad IgM determination. The culture for Ad was positive in 77.8%, direct antigen detection by fluorescent stain was positive in 72.2%, PCR was positive in 83.3%, and serology was positive in 88.9% of patients. Both determination of antibody IgM and PCR correctly identified a larger group of patients compared to cell culture. The most sensitive and specific method for diagnosis of Ad compared to culture was PCR (100%), followed by IgM detection (92.9%) then direct antigen detection by fluorescent stain (85.8%). From this study, we conclude that Ad is a common pathogen in sporadic cases of conjunctivitis. Screening of adenoviral conjunctivitis is possible by using specific IgM due to its high sensitivity. A confirmatory test can be done by PCR for diagnosis of Ad, as it is a rapid, specific, and accurate method.

Comparison of HeLa-I, HEp-2 and NCI-H292 cell lines for the isolation of human respiratory syncytial virus (HRSV)

Generally, laboratory diagnosis of viral respiratory infections utilizes virus isolation in cell culture and immunofluorescence assays. In this study, three cell lines (HEp-2, NCI-H292 and HeLa-I) were used for HRSV isolation of strains obtained from patients admitted at HU-USP with respiratory tract disease. HRSV was isolated in 46% (37) of 80 specimens inoculated in HeLa-I, 48% (39) in HEp-2, and 36.3% (29) in NCI-H292. Immunofluorescence was considered the gold standard and yielded 53% positive (43). The results from both methods combined had better sensitivity (73.2%) compared to either method alone. Comparing results between the cell lines with HEp-2 cells as the benchmark, the greatest sensitivity (72.2%) was observed in HeLa-I. This data shows that HeLa-I is adequate for HRSV isolation, giving results similar to the HEp-2 cells. The combined use of the HEp-2, HeLa-I and NCI-H292 cells improve the detection of HRSV.

Enzyme immunoassay for respiratory syncytial virus: rapid detection in nasopharyngeal secretions and evaluation of isolates representing different RSV subgroups

The presence of respiratory syncytial virus (RSV) was investigated by immunofluorescent antibody (IFA) technique and by an enzyme immunoassay (EIA) in 169 samples of nasopharyngeal secretions of infants and children with acute respiratory infections. Of 31 samples positive by EIA, 25 were positive by IFA. In 24 samples from a retrospective study, RSV positive by IFA and/or tissue culture isolation (TCI), 22 were also positive by EIA. The EIA was also evaluated with 111 RSV isolates in Hep2 cell cultures representing different RSV subgroups. All were positive by EIA.

RSV outbreak in a paediatric intensive care unit

The Royal Liverpool Children's Hospital-Alder Hey paediatric intensive care unit (PICU) usually has a low rate of nosocomial respiratory syncytial virus (RSV) infection. We report and analyse a major outbreak of nosocomial (acquired) RSV infection on the PICU during a RSV season. All children admitted to the PICU were studied during the six-month winter period 1 October 2002 to 31 March 2002. Nasopharyngeal aspirates were tested using an in vitro enzyme-linked immunoassay (ELISA) membrane test for RSV antigen. PICU-acquired RSV infection was considered to have occurred when a child admitted to the PICU was RSV negative, or from whom no samples were taken as they did not exhibit signs of bronchiolitis, but was RSV positive five or more days after the admission. Fifty-four patients tested RSV positive using the ELISA on the PICU. All the patients were ventilated. Thirty-nine children were RSV positive using the ELISA on admission to the PICU ('imported' cases) and 15 became RSV positive whilst on the PICU ('acquired' cases). The source of the acquired RSV infection accounting for the first peak/outbreak in nosocomial cases were RSV-positive children in isolation cubicles. Acquired cases of RSV infection subsided with reinforcement of traditional methods of barrier precautions. The source of the second peak in nosocomial cases were persistent shedders of RSV. Seventy-three percent (11/15) of the acquired RSV cases had one or more of the following co-morbidities: congenital heart disease, chronic lung disease, airways abnormalities or immunosuppression. Droplet precautions (strict handwashing, use of gloves if handling body fluids, single-use aprons, education) rather than the physical barrier of the cubicle itself played a more important role in curtailing nosocomial spread. Persistent shedders of RSV are an important potential source of nosocomial RSV infection within a PICU. Patients with co-morbidities are at increased risk of nosocomial RSV infection.

Lack of sensitivity of rapid antigen tests for the diagnosis of respiratory syncytial virus infection in adults

The diagnosis of respiratory syncytial virus (RSV) infection in older individuals and adults with cardiopulmonary diseases using available rapid antigen detection tests may be difficult due to the low virus shedding in this population. These tests have been extensively evaluated in hospitalized infants, but there is only limited data on their usefulness in adult populations. We evaluated the performance of three different rapid antigen detection tests: Becton Dickinson Directigen RSV (BD), Bartels RSV Direct Fluorescent Antibody Test (DFA) and the VIDAS RSV assay (VIDAS) in nasopharyngeal specimens from 60 older persons with RSV infection documented by cell culture, serology or reverse transcription polymerase chain reaction (RT-PCR). The three rapid antigen assays tested on all 60 samples performed poorly. DFA detected 14 (23%), VIDAS detected 12 (20%) and BD detected only 6 (10%) of the RSV infected persons. Rapid antigen detection tests for the diagnosis of RSV respiratory illness in adults are of limited value.

Acute viral bronchiolitis and its sequelae in developing countries

Acute viral bronchiolitis (AVB) is a common disease found throughout the world. Various aspects of it are being studied: its epidemiology, diagnosis, prognosis and treatment. Most of these studies are being conducted in developed countries, with only a few taking place in developing countries. Risk factors such as poor nutrition, an adverse environment and early weaning should be studied where these features are common. Treatment aspects such as cost-effectiveness in low income settings need further study. Use of ribavirin and respiratory syncytial virus (RSV)-immunoglobulin are good examples. Post-bronchiolitic sequelae also need to be studied in low income countries. There is evidence that bronchiolitis obliterans is unusually frequent in some Latin-American countries such as Argentina and Brazil. It will be helpful to undertake combined studies in countries with the same socio-economics, investigating the preventive and management aspects of AVB and its sequelae to reduce the morbidity and mortality.

New approaches to respiratory infections in children. Bronchiolitis and croup

Croup is a disease that is commonly seen in children younger than the age of 6 years. The cause is viral, with parainfluenza viruses and RSV being the two most common pathogens. Treatment consists primarily of supportive care, and parents usually have tried humidification and cool air exposure before the child presents to the ED. Children with moderate to severe croup are usually seen in the ED. The use of steroids in an oral preparation results in a clinical improvement of outpatients with mild to moderate croup and reduces the need for hospitalization. The dosage range for oral dexamethasone is 0.15 mg/kg to 0.6 mg/kg. Nebulized budesonide may also be used. Racemic or L-epinephrine, both of which are equally effective, can be used for symptomatic treatment in severe croup. After administration of racemic or L-epinephrine, hospitalization is not automatic and patients can be discharged safely from the ED after a 3-hour of observation period. There should be no respiratory distress, and the patient should have access to follow-up and emergency care if needed.

The use of palivizumab monoclonal antibody to control an outbreak of respiratory syncytial virus infection in a special care baby unit

An outbreak of respiratory syncytial virus (RSV) infection affected seven premature infants in a special care baby unit during November and December 1999. Conventional infection control measures (cohorting infected babies, strict reinforcement of the use of gloves and aprons, emphasis on hand disinfection) failed to prevent spread. Palivizumab, a respiratory syncytial virus monoclonal antibody, was given to eight high-risk preterm infants. There were no further cases of RSV in the unit and none of the babies given palivizumab developed RSV. One baby who acquired RSV during the outbreak (and who was not given palivizumab) was subsequently admitted to hospital with another episode of RSV bronchiolitis. The role of palivizumab in the control of hospital outbreaks of RSV infection merits further investigation.

Induction immunosuppression for lung transplantation with OKT3

BACKGROUND

The use of OKT3, an anti-CD3 monoclonal antibody, for immunosuppressive therapy for lung transplantation has been restricted because of concerns regarding infectious risk and cardiopulmonary instability after its administration.

METHODS

Fifty-two patients received OKT3 (5 mg/d intravenously for 10 days) for induction of immunosuppressive therapy, along with azathioprine (1.5 mg x kg(-1) x d(-1) intravenously) and enteral cyclosporine (12 mg x kg(-1) x d(-1)). Maintenance steroid therapy was begun on postoperative day 8. Prophylactic antifungal therapy (fluconazole or amphotericin B) and ganciclovir was used in all patients. Serial transbronchial biopsy and measurements of pulmonary function were used to assess patients for evidence of infection or rejection. Cytomegalovirus infection was diagnosed by biopsy or the presence of cytomegalovirus antigenemia.

RESULTS

The 30-day mortality rate was 4%; the in-hospital mortality rate was 8%. Acute graft failure was seen in 6 patients. The median length of intubation was 5 days, and the median hospital stay was 30 days. Systemic and pulmonary artery systolic pressures, cardiac index, and ratio of arterial partial oxygen pressure to fraction of inspired oxygen showed no significant alteration after OKT3 dosage. Gram-negative pulmonary infections were identified in 12 patients. Aspergillus infection was seen in 7 patients. Cytomegalovirus infection in 8 patients responded to ganciclovir and did not affect mortality. Respiratory syncytial viral infection was seen in 7 patients. Acute rejection was never seen during OKT3 administration. No episodes of acute rejection were identified in 14 patients at any time postoperatively. In the remainder, episodes of acute rejection responded to steroid or antithymocyte globulin therapy. At a median length of follow-up of 31 months, freedom from obliterative bronchiolitis was 69%+/-9% at 36 months. The overall survival rate was 88%+/-5% at 12 months, 82%+/-6% at 24 months, and 74%+/-7% at 36 months after transplantation.

CONCLUSIONS

OKT3 is a safe and effective agent for induction immunosuppressive therapy in lung transplant recipients that limits the incidence of acute rejection and may decrease the incidence of obliterative bronchiolitis.

Comparison of three monoclonal antibody pools for the detection of respiratory viral antigen in respiratory secretions

The aim of this study was to compare the sensitivities of commercial monoclonal antibody pools to be used as an initial rapid screen for detection of viral antigens in respiratory secretions. The availability of commercial monoclonal antibodies has dramatically improved the detection of viruses by immunofluorescence techniques in exfoliated cells obtained from respiratory secretions. Several companies have recently introduced monoclonal antibody pools to detect the presence of respiratory viruses in a single preparation. Ninety-four stored slide preparations that had previously been examined by individual monoclonal antibodies were tested using three commercial monoclonal antibody pools produced by Sanofi (UK), Dako (UK), and Quadratech (UK). These monoclonal antibody pools had a sensitivity of 79.6%, 90.9%, and 100%, respectively, when compared with the original results. The overall intensity of immunofluorescence was also examined.

Respiratory syncytial virus infection in children with congenital heart disease: a review

This paper reviews recent changes in morbidity and mortality of respiratory syncytial virus (RSV) infection in infants with congenital heart disease. Mortality since the late 1970s has declined substantially, from approximately 37% to 3%. Although the frequency of admission to intensive care units has declined from approximately 60% to 30%, the frequency for mechanical ventilatory support has not changed significantly. Because mortality dropped prior to the widespread use of ribavirin, it is difficult to ascribe the improvement to this therapy. In infants with congenital heart disease (CHD), nosocomial infection remains a significant problem, accounting for approximately 33% of the RSV cases. Some authors report significant reductions in hospital-acquired RSV by use of gloves and gowns for contacts with infectious cases. Efforts at primary prevention have encountered problems with development of an RSV vaccine. Preliminary data from studies of passive immunization using immune globulins with high RSV antibody titers suggest that this therapy may reduce the severity of RSV infection in infants with serious heart disease.

Bronchiolitis. Origins and optimal management

There is currently no prospect of an end to the annual epidemics of acute bronchiolitis, which cause considerable morbidity in previously healthy infants and are a major threat to the well-being of infants with underlying cardiac, respiratory or immunological disease. The respiratory syncytial virus remains the major cause of this condition, and prospects of developing a vaccine remain bleak while our understanding of the viral-host interaction remain incomplete. Treatment of patients with this condition has remained essentially unchanged for more than 30 years. Correction of hypoxia with oxygen, minimal handling to reduce the risk of exhaustion and careful noninvasive monitoring for complications such as apnoea and respiratory failure are the mainstays of management. Mortality in at-risk groups has fallen substantially during the past 10 years. This appears to be due to improved supportive and intensive care. The role of the antiviral agent ribavirin in the improved outcome, if any, is unclear. Other novel therapies have been tried, but none have been shown to significantly alter the natural history of the condition. The only effective preventive intervention currently available is strict adherence to measures designed to prevent nosocomial infection. This condition is likely to remain a continuing challenge to paediatricians for the foreseeable future.

Validation of respiratory syncytial virus enzyme immunoassay and shell vial assay results

The Pathfinder respiratory syncytial virus (RSV) enzyme immunoassay (EIA) (Kallestad), the shell vial (SV) technique, and conventional cell culture (CC) were compared for detection of RSV in nasopharyngeal aspirates. We found sensitivities, specificities, and positive and negative predictive values of 58.4, 100, 100, and 68.2%; 80.7, 97.2, 97.0, and 81.9%; and 77.6, 97.2, 96.9, and 79.5% for the CC, EIA, and SV methods, respectively. The SV and EIA techniques were both more sensitive than CC (P < 0.001). Finally, 29 respiratory viruses other than RSV were identified by CC.

Antigen detection in human respiratory Coronavirus infections by monoclonal time-resolved fluoroimmunoassay

BACKGROUND

The diagnosis of respiratory infections by detecting viral antigens has received considerable attention using immunofluorescent assays (IFA) and enzyme immunoassays (EIA). Time-resolved fluoroimmunoassay (TR-FIA) has been developed for several viruses.

OBJECTIVES

To prepare monoclonal antibodies to coronavirus strains, to incorporate them into a TR-FIA, and test the assay on clinical specimens.

STUDY DESIGN

Monoclonal antibodies were prepared to the N nucleoprotein of the two human respiratory coronaviruses, HCV strains 229E and OC43. Monoclonals to both viruses were completely type-specific; they did not cross-react between themselves or with multiple strains of other respiratory viruses. These antibodies were configured into optimized EIA and TR-FIA tests. The all-monoclonal tests were then compared to polyclonal EIA tests in terms of their ability to detect virus in clinical specimens.

RESULTS

The all-monoclonal TR-FIA was uniformly the most sensitive, detecting virus in all 13 229E-positive specimens compared to 69% for the monoclonal EIA and 54% for the polyclonal EIA test. Similar results were obtained for 10 OC43-positive specimens: 100% in TR-FIA, 90% in monoclonal EIA, and 80% in polyclonal EIA. For 229E in TR-FIA, mean positive/negative (P/N) ratios were 143 for 229E-positive human embryonic lung fibroblast (HLF) cell culture fluids and 10 for positive nasopharyngeal aspirate specimens; for OC43 in TR-FIA, mean P/N values were 964 for OC43-positive rhabdomyosarcoma (RD) cell culture fluids and 174 for positive NPA specimens. The sensitivities of the TR-FIA were determined with purified virions to be 0.308 ng virus per well for HCV-229E and 0.098 ng virus per well for HCV-OC43.

CONCLUSIONS

This rapid and sensitive test appears to be much more sensitive than traditional antigen detection assays but will require more extensive field testing on clinical specimens.

Mixed viral infections: detection and management

An analysis was done of the incidence and nature of mixed virus infections diagnosed in the same clinical specimen from immunocompetent patients; respiratory viruses were emphasized. Few studies have addressed mixed viral infections in any systematic fashion. The relevant studies reviewed focused on clinical relationships or diagnostic methods. Data relating to multiple infections were usually derived incidentally to the purpose of the investigations. Sixty-three percent of the reports with data on mixed infections identified them in < 5% of the total number of viral infections. Respiratory syncytial virus was the most common coinfecting virus, and respiratory syncytial virus and influenza virus were the most common virus pair identified. In considering rapid diagnostic techniques, in 87% of the reports with available data a virus was diagnosed in > 10% of specimens that were negative for the virus targeted by one method. There was no indication that mixed infections were associated with increased disease in immunocompetent patients or in certain immunocompromised patients. Immunocompromised patients, however, appeared to have a greater incidence of multiple infections. Mixed infections of single cells also occur and may have important clinical implications relative to reactivation of latent viruses and enhanced disease. The requirement for a comprehensive strategy for viral diagnosis involving multiple techniques was indicated by these findings.

Time-resolved fluoroimmunoassays with monoclonal antibodies for rapid identification of parainfluenza type 4 and mumps viruses

Monoclonal antibodies were prepared to the F and M proteins of parainfluenza 4A and 4B and to mumpsvirus to obtain reagents that could be configured into type-specific yet broadly-reactive IFA, EIA, and TR-FIA tests. Several antibodies to parainfluenza 4A also detected subtype 4B, although to a somewhat lower signal, and thus were well suited to generic parainfluenza type 4 tests that were comparable to similar tests previously described for parainfluenza types 1, 2, and 3. Monoclonals to subtype 4B were less able to detect 4A because of high background problems in one or another test. Monoclonals to mumpsvirus F protein were completely type-specific. These antibodies were screened by IFA and EIA for broad reactivity with diverse strains of each virus and were configured into optimized EIA and TR-FIA tests. The all-monoclonal tests were then compared to polyclonal tests in terms of their ability to detect virus in clinical specimens. The all-monoclonal TR-FIA was uniformly the most sensitive, detecting virus in 80% of culture-positive parainfluenza 4A specimens, 67% of parainfluenza 4B specimens, and 90% of mumps specimens, compared to 40-67% for the monoclonal EIA tests and 33-60% for the polyclonal EIA tests. For parainfluenza 4 TR-FIA, mean P/N values were 379 for subtype 4A cell culture fluids (228 for subtype 4B cultures) and 57 for 4A clinical specimens (43 for 4B specimens). For mumpsvirus TR-FIA, mean P/N values were 27 for culture fluids and 32 for clinical specimens. The sensitivities of the TR-FIA were determined with purified virus to be 0.28 ng virus per well for parainfluenza 4A and 0.70 ng virus per well for mumpsvirus.

Isolation of seven respiratory viruses in shell vials: a practical and highly sensitive method

The isolation of respiratory viruses in shell vials was compared with isolation in tube cultures in order to determine the sensitivity of the former, rapid method. Twenty of 21 influenza virus and 15 of 15 parainfluenza virus isolates were recovered in shell vials. One hundred twenty-seven of 138 respiratory syncytial virus isolates were detected in shell vials, but only 10 of 21 adenovirus isolates were positive by the rapid method. Shell vials are very effective for the diagnosis of respiratory viral infections, except for those caused by adenovirus.

Evaluation of Abbott TestPack RSV for the diagnosis of respiratory syncytial virus infections

Abbott TestPack RSV, a 20-minute enzyme immunoassay, is available for the rapid diagnosis of respiratory syncytial virus (RSV) infections. We have compared TestPack with a "gold standard" method of virus isolation in traditional tube cultures and shell vials to determine the sensitivity and specificity of this rapid method. Respiratory specimens were collected prospectively from 402 children and assayed by the rapid antigen detection method and isolation in culture. Virus was isolated by inoculation of specimen in a total of eight tubes and 2-3 shell vials. Isolation of RSV was confirmed by characteristic cytopathic effect and immunofluorescence using monoclonal antibodies to RSV. Of the 402 specimens tested, there were only 18 discrepant results (seven TestPack-positive, culture-negative, and 11 TestPack-negative, culture-positive specimens). The sensitivity of TestPack RSV versus culture was 93.6% (162 of 173) and the specificity was 97.0% (222 of 229). Using a very rigorous culture system, we have obtained high values for the sensitivity and specificity of TestPack RSV. This assay is an excellent method for the rapid diagnosis of RSV infections in young children.

Rapid detection of respiratory viruses by shell vial culture and direct staining by using pooled and individual monoclonal antibodies

The Bartels respiratory virus panel detection kit is an indirect fluorescent-antibody (IFA) method that uses pooled and individual antisera for tissue culture confirmation of seven respiratory viruses. We evaluated these reagents for detecting viral antigen in shell vial cultures and by direct staining of cells from respiratory specimens. The isolation from 254 specimens of respiratory viruses in shell vial cultures compared with standard tube cultures was highly sensitive (94%) and specific (97.3%). The numbers of viral isolates detected in three consecutive years of testing with shell vial cultures were 68 of 254 (26.8%), 101 of 381 (26.5%), and 122 of 430 (28.4%). IFA direct staining of all 1,065 specimens resulted in 183 (17.2) being uninterpretable because of inadequate numbers of cells or interfering fluorescence. The sensitivity and specificity of the interpretable IFA direct stains in comparison with shell vial cultures were 85.9 and 87.1%, respectively. For detection of 881 adequate specimens, Bartels respiratory syncytial virus IFA direct staining compared with an Ortho Diagnostics Systems direct fluorescent-antibody test for respiratory syncytial virus RSV was highly sensitive (95.5%) and specific (97%). Shell vial cultures combined with Bartels IFA reagents are a rapid alternative to standard tube cultures. Bartels IFA direct staining with individual antisera provides useful same-day screening of respiratory specimens, but the antiserum pool was not effective in screening for positive specimens because of excessive amounts of nonspecific fluorescence.

Evaluation of a commercial enzyme immunomembrane filter assay for detection of respiratory syncytial virus in clinical specimens

A commercial enzyme immunomembrane filter assay (EIFA) for respiratory syncytial virus (RSV) was compared prospectively with isolation in cell culture and an enzyme immunoassay. A total of 595 respiratory specimens, mostly from pediatric patients, were examined. The EIFA was 70.96% sensitive and 72.40% specific in comparison with cell culture. Results for 40 specimens (6.72%) were uninterpretable, mainly due to filtration difficulties. Twenty-one (25%) of 84 specimens whose results were initially considered false-positive were subsequently confirmed positive after a blocking test with bovine anti-RSV serum. On the basis of the total number of confirmed positive results, the sensitivity and the specificity of the test were 87.90% and 75.77%, respectively.

Respiratory syncytial virus infection among intubated adults in a university medical intensive care unit

Respiratory syncytial virus is the major cause of lower respiratory tract infection in children. Adults who are immunocompromised, aged, institutionalized, and/or have underlying medical diseases may be at risk for severe RSV infection. Intubated adults in an MICU were evaluated for evidence of RSV infection. Respiratory secretions were analyzed by cell culture and RSV EIA. Serologic testing was obtained. Respiratory secretions from MICU personnel with acute respiratory symptoms and patients admitted for pneumonia, asthma, or COPD also were screened. Five of 11 intubated patients had evidence of RSV infection. One of seven MICU employees and four of 48 ward patients had RSV-positive respiratory secretions. During community outbreaks of RSV infection, adults admitted to an MICU already may be infected with RSV; those admitted for other reasons are at risk for nosocomial infection. Patients occupying other hospital units and personnel may be instrumental in the nosocomial dissemination of RSV.

Rapid identification of respiratory syncytial virus infections by direct fluorescent antibody testing: reliability as a guide to patient cohorting

This study compared the results of a commercially available, direct fluorescent antibody (DFA) test with viral culture in 880 specimens obtained from 690 patients by means of nasopharyngeal swabs. The two tests were congruent in 92.5% (814) of the specimens. The sensitivity of the DFA was 0.95, the specificity was 0.91, the positive predictive value was 0.82, and the negative predictive value was 0.98. Among 548 inpatients, there were 3 mixed infections (RSV and another virus), 8 RSV infections not identified by the DFA, and 35 positive DFA results not confirmed by cell culture. Use of the DFA test alone would have resulted in 502 (92%) correct patient-placement decisions. We conclude that the DFA test provides reliable evidence on which to base patient-placement decisions but that the error rate is too high to permit safe cohorting of high-risk patients, such as those with bronchopulmonary dysplasia.

Detection of respiratory syncytial virus in nasopharyngeal secretions by shell vial technique

A shell vial technique was used to recover respiratory syncytial virus (RSV) from frozen nasopharyngeal specimens previously tested by rapid diagnostic methods. With specimens determined to be positive by direct fluorescence assay (DFA), the shell vial technique was at least as sensitive as conventional tissue culture (92 versus 90%). The majority of RSV isolates were detected within 16 h postinoculation, versus an average of 4.5 days by conventional techniques. Also, the shell vial method recovered RSV from 16 of 17 specimens (94%) which had previously tested positive by enzyme immunoassay (EIA). In addition, the shell vial method detected RSV in 4 and 11% of specimens previously determined to be negative by DFA and EIA, respectively. Therefore, we recommend the use of the shell vial technique for specimens testing negative by the rapid methods of DFA or EIA.

Comparison of enzyme-linked immunosorbent assay, indirect immunofluorescence assay, and virus isolation for detection of respiratory viruses in nasopharyngeal secretions

Nasopharyngeal secretions obtained from 94 children with acute respiratory illness were examined for the presence of respiratory syncytial virus (RSV), adenovirus, and influenza virus type A by virus culturing (virus isolation technique [VIT]), immunofluorescence assay (IFA), and enzyme-linked immunosorbent assay (ELISA). Similar results were obtained in at least two tests for RSV, influenza virus type A, and adenovirus in 92 (97.9%), 88 (93.6%), and 88 (93.6%) cases, respectively. Both rapid virus detection methods showed good specificity for the diagnosis of these virus infections (greater than or equal to 90.7%) and were more sensitive than was VIT for RSV detection. In a more accurate statistical analysis, the indexes of agreement between VIT and ELISA were substantial for RSV (kappa = 0.69; zeta = 5.5; P less than 0.0001), influenza virus type A (kappa = 0.67; zeta = 5.3; P less than 0.0001), and adenovirus (kappa = 0.71; zeta = 6.0; P less than 0.0001), while it was almost perfect for RSV when ELISA was compared with IFA (kappa = 0.88; zeta = 5.7; P less than 0.0001). Although the observed agreement was good in the comparison of these two tests for these three viruses (89%0, the indexes of agreement were moderate in the comparison of IFA and VIT for RSV (K = 0.55; Z = 2.0; P < 0.05), influenza virus type A (K = 0.42; Z = 9.7; P < 0.0001), and adenovirus (K = 0.41; Z = 6.5; P < 0.0001) and of ELISA and IFA for influenza virus type A (K = 0.55; Z = 7.0; P < 0.0001) and adenovirus (K = 0.59; Z = 6.8; P < 0.0001). All of the statistical evaluations demonstrated better agreement between ELISA and VIT for influenza virus type A and adenovirus.

Evaluation of direct immunofluorescence, enzyme immunoassay, centrifugation culture, and conventional culture for the detection of respiratory syncytial virus

Four methods of detecting respiratory syncytial virus (RSV) from clinical specimens were evaluated. A total of 410 specimens consisting of nasopharyngeal washes, aspirates, and swabs were simultaneously tested for the presence of RSV by direct immunofluorescence assay (DFA), enzyme immunoassay (EIA) (Kallestad Pathfinder), shell vial centrifugation culture (SVC), and conventional culture. DFA identified 146 (83%) of the 175 positive cases, EIA detected 153 (87%), SVC detected 127 (73%), and conventional culture detected 70 (40%). Conventional culture isolated an additional 19 respiratory viruses other than RSV. DFA and EIA were able to detect nonviable virus not isolated by a culture method, and SVC isolated low-titer virus not detected by conventional culture. DFA and EIA gave similar results; however, the EIA system was less dependent on technical expertise. The use of SVC enhanced the conventional culture system with 63 RSV isolates not recovered from the tube culture. We recommend complementary use of both culture and nonculture methods in the detection of RSV.

Detection of respiratory syncytial virus antigen after seventy-two hours of culture

Between September, 1987, and April, 1989, three techniques for the detection of respiratory syncytial virus (RSV) were compared: indirect immunofluorescence (IF) on the sample, indirect immunofluorescence after 72 h of MRC-5 cell culture (IF 72h), and detection of the cytopathic effect (CPE) by MRC-5 and HEp-2 cell culture. A study of 383 nasal aspirates from young children admitted to the Centre Hospitalier de Nantes (CHR) showing miscellaneous respiratory symptoms produced the following results: 143 samples (37%) were RSV positive by IF, 119 (31%) were positive by IF 72h, and 117 (31%) showed RSV-induced CPE. In comparison with tissue culture isolation (TC), the sensitivities of IF and IF 72h were 89% and 80% and their specificities 85% and 91%, respectively. During the winter of 1988-1989, of the 110 RSV-positive nasal aspirates (104 by IF, 89 by IF 72h, 83 by CPE detection), 109 were identified by IF and/or IF 72h. IF 72h affords rapid detection of RSV.

Rapid detection of respiratory syncytial virus and influenza A virus in cell cultures by immunoperoxidase staining with monoclonal antibodies

Peroxidase-labeled monoclonal antibodies against respiratory syncytial virus (RSV) and influenza A virus were used for immunoperoxidase staining (IPS) of cell cultures inoculated with nasopharyngeal aspirates. Cells were grown in 24-well plates, and specimens were inoculated by low-speed centrifugation. Cultures were incubated for 2 days at 37 degrees C and then fixed, stained, and observed by light microscopy. IPS was compared with standard virus isolation by using cultures of human diploid fibroblasts and Vero, HEp-2, and HeLa cell lines for RSV and Madin-Darby canine kidney cells for influenza A virus; these cultures were inoculated with specimens that were previously stored at -70 degrees C. Of 40 known RSV-positive specimens, 30 were found to be positive on reinoculation by both methods, and an additional 5 specimens were found to be positive by IPS only. Of 190 specimens tested for influenza A virus, 14 were positive by IPS and in tubes, and a further 8 specimens were positive by IPS only. IPS was also compared with direct detection of viral antigens in nasopharyngeal aspirates by a time-resolved fluoroimmunoassay (TR-FIA). Fresh nasopharyngeal aspirates were inoculated into human diploid fibroblasts and Madin-Darby canine kidney cells and tested for RSV and influenza A virus, respectively, by IPS. Of 110 specimens tested for RSV, 37 were positive in total, 32 were positive by IPS, and 33 were positive by TR-FIA. Of 150 specimens tested for influenza A virus, 39 were positive in total, 35 were positive by IPS, and 34 were positive by TR-FIA. IPS of cultures inoculated by centrifugation and incubated for 2 days is a sensitive method for the diagnosis of respiratory virus infections, and 24-well plates allow for the easy processing of a large number of specimens.

Evaluation of five methods for respiratory syncytial virus detection

A total of 117 nasal aspirates were cultured for respiratory syncytial virus (RSV) and tested for RSV antigen by a direct fluorescent-antibody (DFA) test (Bartels Immunodiagnostic Supplies, Inc., Bellevue, Wash.), the Directigen enzyme immunoassay (EIA; Becton Dickinson Microbiology Systems, Cockeysville, Md.), the TestPack EIA (Abbott Laboratories, North Chicago, Ill.), and RSV EIA (Abbott). Agreement of two of five methods or a positive RSV culture were required to validate a result. A total of 57 of 117 (48.7%) specimens were culture positive in HEp-2 cells, A549 cells, or both. A total of 5 of 117 (4.3%) additional specimens met the criteria of a positive specimen; i.e., 62 of 117 (53.0%) specimens were positive. Results obtained from 77 of 117 (65.8%) specimens were concordant for all five methods. The sensitivities, specificities, and positive and negative predictive values for the culture and DFA methods were 91.9, 100, 100, and 91.7% and 91.9, 96.4, 96.6, and 91.4%, respectively. The sensitivities, specificities, and positive and negative predictive values for the three EIA procedures, Directigen, TestPack, and RSV EIA, were 75.8, 80.0, 81.0, and 74.6%; 93.6, 100, 100, and 93.2%; and 71.0, 100, 100, and 75.3%, respectively. New self-contained EIA configurations and the DFA method offer attractive alternatives to the culture method. Technical simplicity, rapid turnaround time, performance, and cost must all be considered when selecting a system for RSV detection.

Respiratory virus infection as a cause of prolonged symptoms in acute otitis media

We studied respiratory viruses in 22 children with acute otitis media who had failed to improve after at least 48 hours of antimicrobial therapy. The mean duration of preenrollment antimicrobial therapy was 4.8 days. For comparison we studied 66 children with newly diagnosed acute otitis media. Respiratory viruses were isolated from middle ear fluid or from the nasopharynx, or both, significantly more often in the patients unresponsive to initial antimicrobial therapy than in the comparison patients (68% vs 41%, p less than 0.05). Viruses were recovered from the middle ear fluid in 32% of the study patients and from 15% of the comparison group. Bacteria were isolated from the middle ear fluid of four (18%) children in the study group; one child had an isolate resistant to initial antimicrobial therapy. All four children with bacteria in the middle ear fluid had evidence of concomitant respiratory virus infection. Our results indicate that respiratory virus infection is often present in patients with acute otitis media unresponsive to initial antimicrobial therapy, and may explain the prolongation of symptoms of infection. Resistant bacteria seem to be a less common cause of failure of the initial treatment.

Detection of respiratory syncytial virus in nasopharyngeal secretions by DNA-RNA hybridization

We have developed an RNA-cDNA hybridization assay for the detection of respiratory syncytial virus (RSV) RNA in nasopharyngeal samples. We chose to use as probe a cDNA complementary to the nucleocapsid protein gene of RSV, integrated into the plasmid vector pBR322. The lower limit of sensitivity of the assay is 8.2 X 10(2) PFU of the Long strain of RSV. In throat washes with added cell-free virus, the assay can detect 3.3 X 10(3) PFU of RSV. Respiratory secretions were collected from a group of 104 infants in New Orleans, and 73 of the samples were tested for RSV by immunofluorescence (IF). All were then frozen at -70 degrees C for later testing by hybridization, and 67 were tested for RSV antigens by enzyme immunoassay (EIA). A second set of respiratory secretions from 48 infants in Denver were cultured for virus, assayed for RSV antigen by EIA, and then frozen for later testing by hybridization. For those samples on which IF was performed, hybridization, compared with IF, had a sensitivity of 49% and a specificity of 66%. For samples tested by EIA, hybridization had a sensitivity of 60% and a specificity of 81% compared with EIA. Compared with virus isolation, hybridization assay had a sensitivity of 73% and a specificity of 92%. With clinical samples, the sensitivity and specificity of the assay were improved with the addition of a control blot, which was hybridized to the plasmid vector (pBR322). The performance of the hybridization assay can be expected to improve when the assay is used with fresh clinical material rather than frozen samples.

Nasopharyngeal swabs and nasopharyngeal aspirates equally effective for the diagnosis of viral respiratory disease in hospitalized children

Paired nasopharyngeal swab and nasopharyngeal aspirate specimens from 125 patients were compared for viral diagnosis. The viral isolation rates were comparable for the two types of specimens. There was a high level of agreement between the two specimens in overall positivity rate by immunofluorescence and positivity in culture-confirmed patients.

Comparison of monoclonal antibody time-resolved fluoroimmunoassay with monoclonal antibody capture-biotinylated detector enzyme immunoassay for respiratory syncytial virus and parainfluenza virus antigen detection

An all-monoclonal antibody, time-resolved fluoroimmunoassay was compared with several enzyme immunoassays for the detection of respiratory syncytial virus and parainfluenza virus type 1, 2, and 3 antigens in clinical specimens. The most sensitive enzyme immunoassay for parainfluenza virus type 1 was an all-monoclonal antibody assay with biotin-labeled detector antibody and streptavidin-peroxidase conjugate, but for respiratory syncytial virus and parainfluenza virus types 2 and 3 the most sensitive assay was a polyclonal antibody assay with horse capture antibodies and bovine or rabbit detector antibodies with anti-species peroxidase. All tests were evaluated with nasopharyngeal aspirate specimens from respiratory illnesses and with cell culture harvests of multiple strains of each virus isolated over many years. The time-resolved fluoroimmunoassay detected respiratory syncytial virus antigen in 92% of the specimens positive by culture, which was a decidedly higher sensitivity than either the monoclonal or polyclonal antibody enzyme immunoassay format (62 and 76%, respectively). For the parainfluenza viruses the time-resolved fluoroimmunoassay detected type-specific antigen in 94 to 100% of culture-positive specimens and again was more sensitive than the all-monoclonal antibody enzyme immunoassays (75 to 89%) or all-polyclonal antibody enzyme immunoassays (66 to 95%). Combined with results from a previously reported adenovirus time-resolved fluoroimmunoassay, these tests identified respiratory antigens in large numbers of clinical specimens.

Evaluation of a monoclonal antibody pool for rapid diagnosis of respiratory viral infections

A pool of monoclonal antibodies (MAbP) was evaluated both as a method of cell culture confirmation and as a rapid diagnostic screen for viral infection in respiratory secretions. The MAbP was used in a two-step fluorescent staining procedure on cells harvested from cultures (phase 1) and on exfoliated nasopharyngeal or tracheal cells (phase 2). Antibodies in the MAbP were directed against respiratory syncytial virus, adenoviruses, parainfluenza virus types 1, 2, and 3, and influenza viruses A and B. Individual antiviral antibody stains were used to identify specific viruses from MAbP-positive specimens. In phase 1 (cell culture confirmation only), 241 respiratory specimens were tested. MAbP sensitivity and specificity were 91 and 94%, respectively. In phase 2, 376 respiratory specimens were evaluated by direct staining of exfoliated cells, and these results were compared with results of cell culture isolation. The sensitivity and specificity of the MAbP used in direct specimen testing were 69 and 97%, respectively. These results indicate that the MAbP is highly specific and fairly sensitive for detection of seven different respiratory viruses in one testing procedure. The MAbP is a rapid screening technique for respiratory secretions and is potentially a cost-effective approach to viral detection.

Use of high-speed rolling to detect respiratory syncytial virus in cell culture

We examined the effect of motion on respiratory syncytial virus (RSV) growth in cell culture. Infected cultures were incubated stationary, rolling, or on an orbital shaker. Enzyme immunoassay (EIA) results for cultures infected with high concentrations of a laboratory strain of RSV were similar for all incubation conditions. However, cultures infected with low concentrations of virus and rolled at 96 rpm had a significantly greater mean EIA optical density (1.78 +/- 0.22) than cultures rolled at 2 rpm (1.42 +/- 0.08) (P less than 0.05). The mean EIA optical density of high-speed-rolled cultures was also significantly greater than for cultures on an orbital shaker (1.25 +/- 0.08) or for stationary cultures (0.21 +/- 0.17) (P less than 0.01). The amount of virus measured by EIA from cultures infected with clinical specimens was also found to be significantly greater at 96 rpm than for stationary cultures. Cultures infected with cell culture isolates were detected significantly earlier at 96 rpm than when stationary. We suggest that high-speed-rolling can be used to enhance the detection of RSV in clinical specimens, especially if the virus is present in low concentrations.