Molecular Typing of Mastadenoviruses in Simultaneously Collected Nasopharyngeal Swabs and Stool Samples from Children Hospitalized for Acute Bronchiolitis, Acute Gastroenteritis, and Febrile Seizures

Abstract

This study determines and compares the frequency of human mastadenovirus (HAdV) presence in children with acute bronchiolitis (AB), acute gastroenteritis (AGE), and febrile seizures (FS), ascertains types of HAdVs associated with each individual syndrome and contrasts the findings with a control group of children. The presence of HAdVs was ascertained in simultaneously collected nasopharyngeal (NP) swabs and stool samples amplifying the hexon gene by RT-PCR; these were sequenced to determine the types of HAdVs. HAdVs were grouped into eight different genotypes. Of these, three (F40, F41, and A31) were found solely in stool samples, whereas the others (B3, C1, C2, C5, and C6) were found in both stool samples and NP swabs. The most common genotypes in NP swabs were C2 (found in children with AGE and FS) and C1 (only in children with FS), whereas in stool samples genotypes F41 (in children with AGE) and C2 (in children with AGE and FS) prevailed, and C2 was simultaneously present in both samples. HAdVs were more often detected in stool samples than in NP swabs in patients (with the highest estimated viral load in stool samples in children with AB and AGE) and healthy controls and were more common in NP swabs in children with AGE than in children with AB. In most patients, the characterized genotypes in NP swabs and stool samples were in concordance.

Keywords: acute bronchiolitis; acute gastroenteritis; clinical study; control group; febrile seizures; follow-up; mastadenoviruses; simultaneously collected nasopharyngeal swabs and stool samples.

Figure 1

Box and whisker plots of estimated viral load of HAdVs (Ct value) in NP swabs (A) and stool samples (B) among patients with AB, AGE, and FS, and controls. HAdV = human mastadenovirus, NP = nasopharyngeal swab, AB = acute bronchiolitis, AGE = acute gastroenteritis, FS = febrile seizures, Ct-value = cycle threshold value for participants with positive results, circles represent outlier or single data point.

Figure 2

Seasonal distribution of HAdV-positive and -negative results in NP swabs and stool samples, estimated in patients with AB, AGE, and FS, and controls.

Figure 3

Seasonality of HAdV-positive results in NP swabs and stool samples, estimated separately in patients and controls. Estimates (solid lines) were obtained using periodic restricted cubic splines; dashed lines are pointwise 95% CI. p-values test the overall association between time and probability of positive result.

Figure 4

Scatter plots of estimated viral load (Ct-values) of simultaneously detected HAdVs in NP swabs and stool samples in the control and patient groups (AB, AGE, FS). The gray line is the identity line, and the blue line estimates the association between Ct-values in NP swabs using a smooth function.

Figure 5

Differences in Ct-value in simultaneously detected HAdVs in both NP swabs and stool samples in the control and patient groups (AB, AGE, FS), circles represent outlier or single data point.

Figure 6

Individual transition in test results between baseline and the follow-up visit for patient groups (AB, AGE, FS).

Figure 7

Neighbor-joining phylogenetic tree based on 675-nucleotide-long sequences of a partial hexon gene with 79 representatives of Slovenian HAdV strains detected in nasopharyngeal samples (ο) or stool samples (∆) and eight different HAdV strains from the GeneBank database (with name of HAdV strains and accession numbers). The different colors of the shapes from the Slovenian HAdV strains represent different clinical observations of children: black (AB), red (AGE), blue (FS), and yellow (CO).