No abstract

Group A rotaviruses are the major cause of severe gastroenteritis in young children worldwide. Because rotavirus vaccination appeared imminent, a nationwide surveillance program was organized between October 1996 and October 1998 in the largest Argentine cities. Surveillance for disease burden, rotavirus detection, and rotavirus typing was undertaken at nine locations. Results showed rotavirus to be associated with 42% of diarrhea admissions. Although the prevalent G types changed from year to year, common G types were found in 96% of the cases and were usually associated with common P types. Uncommon G types, G9 and G5, were found at low prevalence and uncommon G/P combinations occurred at almost every study site. These data suggest that a rotavirus vaccine could substantially decrease the rotavirus disease burden in Argentina, but that introduction of a vaccine should be accompanied by a concurrent surveillance system.

Shiga-like toxin-producing Escherichia coli have been associated with hemorrhagic colitis and the hemolytic uremic syndrome (HUS). Because Argentina has the highest reported frequency of HUS in the world, Argentine children were prospectively studied during the HUS seasons for evidence of Shiga-like toxin-related diseases. On the basis of serology, fecal cytotoxin neutralization, stool cultures, and DNA hybridization of colony lysates, most children with HUS had evidence of infection with Shiga-like toxin-producing organisms. Children with spring-summer diarrhea also commonly (32%, confidence interval 18%-46%) had clear-cut evidence of such infection. No controls (children without gastrointestinal, renal, or hemolytic disease) had free fecal cytotoxin, positive cultures for E. coli O157:H7, or DNA probe-positive organisms; 20% of them had low serum titers of antibodies to Shiga-like toxins. E. coli O157:H7 was not common in either HUS or diarrhea patients. The high frequency of Shiga-like toxin-induced diarrhea in young children in Argentina probably explains the high incidence of HUS in this country and suggests that HUS is a relatively uncommon complication of Shiga-like toxin-related disease.

No abstract

We analysed the production of nitric oxide (NO) intermediates by cells from BALB/c mice infected with either virulent (Tulahuén or RA) or avirulent (CA-1) strains of Trypanosoma cruzi. Peritoneal or spleen cells from mice infected with T. cruzi released NO when incubated without further stimuli. Cells from mice during the acute stage of infection accumulated higher levels of inducible NO synthase mRNA and produced both, before and after lypopolysaccharide stimulation, higher amounts of NO than cells from mice chronically infected with T. cruzi. NO synthesis showed similar kinetics in connection with all three strains of T. cruzi, but cells from mice inbred with the Tulahuén or RA strains released higher levels of IFN-gamma, an activator of the NO pathways, than cells from mice infected with the CA-1 strain. In vivo administration of L-Ng-monomethyl-L-arginine (L-NMMA), a competitive inhibitor of NO synthase, increased the susceptibility of mice to T. cruzi. We conclude that infection with T. cruzi induces NO production, and suggest that NO plays a role in the resistance against the parasite.