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Genomic analysis of adenovirus isolated from Argentinian children with acute lower respiratory infections

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Abstract

Background: Adenoviruses are the second cause of acute lower respiratory infection (ALRI) of viral origin in small children from Buenos Aires, Argentina. Objective: The aim of this study was to characterize, by restriction enzyme analysis, 17 adenovirus strains isolated from the nasopharyngeal aspirates of children under 2 years of age hospitalized due to ALRI. Study design: Seventeen adenovirus strains isolated between May 1991 and December 1992 in one hospital of Buenos Aires were studied. Adenoviruses were amplified in HEp-2 cells and viral DNA was studied with the restriction enzymes Bam HI and Sma I. Results and conclusions: Eighty two percent (14/17) of the isolates were classified as adenoviruses from subgenus b and 17.7% (3/17) belonged to subgenus c. Genome type 7 h was detected in 85.7% (12/14) and 7 i in 14.3% (2/14) of the strains from subgenus b. The case lethality associated with adenovirus genome type 7 was 28.6% (4/14 cases). Three fatal cases corresponded to Ad 7 h and one to Ad 7i. Ad 7h shows a high prevalence in small children hospitalized with ALRI and is associated with a high fatality rate.

Introduction

Adenoviruses play an important role in the etiology of severe acute lower respiratory infection (ALRI) in infants and young children. The occurrence of fatal outcome and chronic pulmonary sequelae in association with adenovirus infection has been reported (Sharp and Wadell, 1995). Respiratory diseases are caused by adenoviruses from subgenus b (serotypes 3 and 7); subgenus c (serotypes 1, 2 and 5) and subgenus e (serotype 4) (Sharp and Wadell, 1995).

The frequency of adenoviruses as a cause of ALRI in civilian populations is low in developed countries. In the USA, these viruses are the third viral agent (3%) in children under 5 years of age (Taussing et al., 1989), after respiratory syncytial virus (RSV) (32–36%) and parainfluenza (17%). In Sweden, adenoviruses are responsible for 5% of ALRI in hospitalized children (Sharp and Wadell, 1995).

In Argentina, adenoviruses are the second most common viral agent in children under 5 years of age hospitalized due to ALRI, after RSV. Weissembacher et al. (1990) showed a 2.7% rate of adenovirus detection (27/1003 cases) and Carballal et al. (1996) reported a 2.5% rate (31/1234) in inpatients from primary care centers in Buenos Aires. In contrast, the frequency of adenovirus associated with pneumonia or necrotizing bronchiolitis is higher (14.3–34%) in specialized hospitals (Videla et al., 1998) (Mistchenko 1996, personal communication).

Restriction enzyme analysis of viral DNA provides an essential tool for epidemiologic studies, allowing the identification and typing of adenoviruses to subgenus level and the distinction of genome variants within a given serotype.

The objective of this study was to characterize, by restriction enzyme analysis, 17 adenovirus strains isolated from the NPAs of children with ALRI in a hospital of Buenos Aires.

Section snippets

Population

Seventeen children under 2 years of age, hospitalized due to pneumonia or bronchiolitis with adenovirus diagnosis were selected for this retrospective study. These children represented the 70% (17/24) of all detected cases of adenoviruses in a population of 168 children under 2 years of age, admitted to one ward of the ‘P. de Elizalde’ hospital, between May 1991 and December 1992. Adenoviruses were studied in the nasopharyngeal aspirates (NPA) by indirect immunofluorescence (IIF) and isolation

Results

The characterization by restriction enzyme analysis of 17 adenovirus strains isolated from NPAs showed that 82.3% (14/17) belonged to subgenus b and the remainder, 17.7% (3/17), to subgenus c.

Within subgenus b, genome type 7 h was the predominate type being detected in 85.7% (12/14 strains). Two strains were classified as Ad 7 i (14.3%). Genome types Ad 2 D7 (one case) and Ad 1 D1 (two cases) were detected within subgenus c.

Fig. 1, Fig. 2 show the restriction profiles with Bam HI and Sma I,

Discussion

The genomic analysis of 17 adenovirus strains showed a predominance of subgenus b (82.3%). The genome type 7 h was the most frequent, corresponding to 85.7% of all isolates in that subgenus. Only two cases (14.3%) were assigned to genome type 7 i.

Ad 7 h had been previously identified in the South cone of America associated with severe and fatal pneumonia and necrotizing bronchiolitis in small children (Kajon and Wadell, 1992, Kajon and Wadell, 1994, Murtagh et al., 1993).

The predominance of a

Acknowledgements

This study was partially supported by Grant no. 33-81500/92 from CONICET. We thank M. Aguilar and A. Mirsiglian for collecting the samples and providing access to clinical histories, and Cristina Juarez, Carmen Ricarte and Beatriz Ebekian for technical assistance.

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