Investigation of Adenoviruses in Children with Lower Respiratory Tract Infections

Abstract

Adenoviruses which are one of the causative agents of acute respiratory tract infections at all age groups worldwide, can lead to epidemic, endemic or sporadic infections year-round. Adenovirus infections in lower respiratory tract can be presented as bronchitis, bronchiolitis and pneumonia. The aim of this study was to investigate the presence of adenoviruses as the etiologic agent of lower respiratory tract infections (LRTIs) in children by cell culture, polymerase chain reaction (PCR) and direct fluorescence antibody (DFA) test. The results of the laboratory tests were evaluated in the light of patients' clinical findings. The study consisted of 206 patients aged between 0-5 years old and who were admitted to the hospital with the complaints of LRTI between January 2011 and April 2012. The clinical, radiological and laboratory findings of the patients were recorded. Nasopharyngeal specimens were taken with flocked swab from all patients and adenoviruses were investigated by shell-vial cell culture, real-time PCR and DFA test, simultaneously. Of all the samples 89.3% were taken in January, February and March and 38% of the patients have one or more chronic underlying diseases as chromosomal abnormalities, congenital heart disease, heart failure, asthma, cystic fibrosis, leukemia, kidney failure and prematurity. Adenovirus was detected in 12 (5.8%) of the samples by PCR, seven (3.4%) of the samples by cell culture method. While seven samples were found positive with both PCR and cell culture, 194 samples yielded negative results in both tests. Five samples, which were found positive by PCR, were not grown in cell culture method. Twelve of the 153 samples examined with DFA test, could not be evaluated due to insufficient amount of cells, however 2.8% (4/141) of the samples were found positive for adenovirus antigens by DFA method. Those samples were also positive ones in the other two methods. Compared with cell culture, the sensitivity, specificity, positive and negative predictive values of PCR were 100%, 97.5%, 58.3% and 100%, respectively; those values were 57%,100%,100% and 97.7%, respectively for DFA testing. Compared to PCR the sensitivity of cell culture is very low (16.6%) after three days of incubation, however, it increased to 58.3% after five days' of incubation. There was no significant relationship between adenovirus positivity and the presence of chronic diseases, the radiological findings and the laboratory findings. Of all adenovirus positive samples 83.3% were obtained in January, February and March. Our data indicated that the etiological agent was adenovirus in approximately 6% of children with LRTI. The most important step for the isolation of adenovirus from respiratory tract, is high quality and sufficient amounts of sample. The flexible flocked swabs made it easy to take nasopharyngeal swab from children. Although cell culture is still the gold standard for the diagnosis of adenovirus infections, PCR which is a fast method with high sensitivity and specificity can also be used. However, specific care should be taken during the DNA extraction stage, since the amount of the nucleic acid in the sample is critical for the best results. Even though the low sensitivity of DFA restricts its use in routine diagnosis of adenovirus infections, it should always be kept in mind that the quality of the clinical samples is most reliably evaluated by this method.