Abstract 1036 Poster Session IV, Tuesday, 5/4 (poster 148)

Aims: Human astrovirus (HAstV) infections cause 5-17% of sporadic diarrheal episodes in young children as detected by enzyme immunoassay (EIA). Our aims were to compare the incidence of HAstV infections detected by EIA and reverse transcriptase-polymerase chain reaction (RT-PCR), to compare the sensitivity and specificity of EIA to RT-PCR, and to determine HAstV antigenic types in diarrhea episodes of infants by type-specific RT-PCR and sequence analysis.

Methods: From November 1989 through December 1991, 214 children in a periurban area in Mexico City were monitored prospectively for diarrhea from birth to 18 months of age. Stool samples from diarrhea episodes previously tested for all HAstV types by EIA were tested by RT-PCR using type-common primers from ORF1a (nts 1182-1470, HastV-1). HAstV-positive samples were genotyped using type-specific primers for HAstV-1, 2, 3, and 4. Sequence analysis of the 3′ end of ORF2 was used to confirm the type assignment.

Results: Stool samples (N=251) from 232 diarrheal episodes were tested. HAstV was detected in 16 (7%) samples by RT-PCR. Two EIA-negative samples were RT-PCR-positive and one EIA-positive sample was PCR-negative. EIA was 87.5% sensitive and 99.6% specific compared to RT-PCR. Type-specific EIA typed nine (60%) of the 15 samples; type-specific RT-PCR typed ten (67%) samples. Sequence analysis confirmed eight of the nine EIA typed samples (89%) and nine of the ten samples (90%) typed by RT-PCR. Sequence analysis determined the type of the five samples. (Table)

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Conclusion: The 7% incidence of HAst V diarrhea in this community is similar to that observed in other developing countries by EIA. RT-PCR was slightly more sensitive and equally specific when compared to EIA, for detection of HAstV infection. Type-specific RT-PCR combined with sequence analysis provided more information for types than typing EIA.