Escherichia coli strains of nonenteropathogenic serogroups carrying eae but lacking the enteropathogenic E. coli adherence factor plasmid and Shiga toxin DNA probe sequences were isolated from patients (children, adults, and AIDS patients) with and without diarrhea in Brazil. Although diverse in phenotype and genotype, some strains are potentially diarrheagenic.

SummaryThe resurgence of tuberculosis and the emergence of multidrug-resistant mycobacteria necessitate the development of new antituberculosis drugs. The biosynthesis of mycolic acids, essential elements of the mycobacterial envelope, is a good target for chemotherapy. Species of the Mycobacterium tuberculosis complex synthesize oxygenated mycolic acids with keto and methoxy functions. In contrast, the fastgrowing Mycobacterium smegmatis synthesizes oxygenated mycolic acids with an epoxy function. We describe the isolation and sequencing of a cluster of four genes from Mycobacterium bovis bacillus Calmette-Gué rin (BCG), coding for methyl transferases, and which, when transferred into M. smegmatis, allow the synthesis of ketomycolic acid, in addition to an as yet undescribed mycolic acid, hydroxymycolic acid. These oxygenated mycolic acids, unlike the regular mycolic acids of M. smegmatis, and similar to the mycolic acids of M. bovis, are highly cyclopropanated. Furthermore, there is a perfect match between the structures of the keto-and the hydroxy-mycolic acids. We propose a biosynthetic model in which there is a direct relationship between these two types of mycolic acid.

In high prevalence settings, histoplasmosis often revealed AIDS in severely immunodeficient and poorly followed patients. In the absence of a quick sensitive technique, skin smear and fungal tissue cultures are contributive. Nevertheless, given the diagnostic delays and the poor prognosis, presumptive treatment with amphotericin B-containing regimens should be recommended when clinical and epidemiological contexts are evocative.

Twenty-nine Shiga toxin-producingShiga toxin-producing Escherichia coli (STEC) can cause a broad spectrum of human illness ranging from uncomplicated diarrhea to hemorrhagic colitis (HC) and hemolytic-uremic syndrome (HUS) (14). E. coli O157:H7 is by far the most important STEC serotype in the world and has been associated with numerous outbreaks and many sporadic cases of HC and HUS (20). However, infections with other non-O157 STEC serotypes have been increasingly reported in many countries (2,3,22). Currently more than 100 different non-O157 STEC serotypes have been isolated from human infections. Unlike with O157:H7, outbreaks caused by non-O157 STEC have rarely been reported, and these strains have been more frequently associated with sporadic cases of diarrhea, HC, and HUS. Moreover, in many countries, non-O157 strains are more commonly isolated from patients with diarrhea or HUS than are O157 STEC strains (3, 5, 23). The major virulence trait of these bacteria is the production of one or more Stx types (Stx1, Stx2, or Stx2 variants) (20). Additional factors, produced mainly by strains in straight association with human disease and collectively referred to as enterohemorrhagic E. coli (EHEC), include intimin and enterohemolysin (1,20). Other putative virulence factors include the enteroaggregative E. coli heat-stable enterotoxin (EAST-1), encoded by astA (25), particularly in O157:H7 and O26:H11 strains and in some other STEC serotypes. In Brazil, the studies conducted so far that searched for STEC in human diarrheal disease have investigated a limited number of strains and have described the isolation of a few non-O157 STEC strains (7,12,16). The isolation of O157:H7 strains from patients with bloody diarrhea as well as one with HUS related to O26:H11 infection was only recently reported in Brazil (15,19).The purpose of this study was to search for STEC in a collection of 2,607 E. coli isolates, most of them belonging to important serogroups increasingly associated with HUS and HC in other countries. The main virulence factors, biotypes, and susceptibility to antimicrobial agents of the STEC strains identified were characterized.The E. coli strains studied belonged to the collection of Instituto Adolfo Lutz, a Central Public Health Laboratory in São Paulo, Brazil, and national center for E. coli serotyping, and were isolated between 1976 and 1999, mainly from children (0 to 5 years old) with diarrhea (2,549 strains); the remaining 58 E. coli strains were isolated from immunocompromised adult patients with diarrhea (mainly human immunodeficiency virus positive) over the same period. Each strain was derived from one patient. Except for diarrhea, no other information regarding the clinical aspects of the patients were available. None of the strains belonging to the enteropathogenic E. coli (EPEC) serogroups carried the EAF sequence (EPEC adherence factor) as assayed by hybridization assays with a specific DNA probe (13). The remaining strains outside the EPEC serogroups did not belong to the enteroinvasive ...