O157:H7 Shiga toxin-producing Escherichia coli strains associated with sporadic cases of diarrhea in Sao Paulo, Brazil. (Letters).

To the Editor: Shiga toxin-producing Escherichia coli (STEC) strains are associated with a spectrum of diseases ranging from mild to severe bloody diarrhea and complications such as hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (1). Since STEC was linked with hemorrhagic colitis in 1982 (2), strains--particularly serotype O157:H7--have been associated with numerous outbreaks and many sporadic cases of infections worldwide. STEC is now a major cause of foodborne disease, primarily in the United States, Canada, Japan, and Europe (1,3). Although most sporadic cases and outbreaks have been reported from developed countries, human infections associated with STEC strains have also been described in Latin American countries, including Argentina and Chile (3). In Brazil, STEC infections have been related to sporadic cases of nonbloody diarrhea caused by non-O157 strains (4,5); serotype O157:H7 has not been previously isolated from human infections in our country.

We report the characterization of three O157:H7 strains isolated in Sao Paulo State, Brazil. The first strain was identified among a laboratory collection of 2,573 E. coli strains that were retrospectively analyzed and isolated from patients with diarrhea in Sao Paulo State, from 1976 through 1999, at the Central Laboratory of Instituto Adolfo Lutz (IAL). This strain was isolated in 1990 from an 18-year-old patient with diarrheal disease who had AIDS. The two other O157 strains were recently isolated from a 4-year-old girl with bloody diarrhea and from an adult with severe diarrhea. Both patients were admitted to the same hospital at Campinas, Sao Paulo State, in June and July 2001, respectively. The strains, isolated by routine diagnostic procedures on MacConkey agar plates, were presumptively identified as E. coli O157 by standard methods with specific O157 antiserum. These last two strains were confirmed as sorbitol-negative E. coli O157 at the IAL Regional Laboratory at Campinas and were sent to the IAL Central Laboratory for further characterization.

The three O157 E. coli strains underwent biochemical identification and serotyping by standard methods, Enterohemolysin production was determined according to Beutin et al. (5). Polymerase chain reaction assays were used to detect the stx1 and stx2 genes (6), and colony hybridization assays with specific DNA probes for stx1, stx2 and eae genes were performed as described (7). Cytotoxicity to Vero cells was assayed as described (4). The strains were characterized as sorbitol-negative O157:H7, containing the stx2 and eae sequences. The enterohemolytic phenotype and production of Stx were also observed in all isolates.

To our knowledge, these O157:H7 STEC strains are the first to be associated with human diseases in Brazil. Cultivation of stool specimens in sorbitol MacConkey agar is strongly recommended for screening O157 strains, and, indeed, all three strains were isolated from MacConkey agar plates. Laboratories should attempt to examine stool specimens from all patients (children and adults) with HUS, severe diarrhea (nonbloody and bloody stools) requiring hospitalization, or both, as well as from patients reporting a history of bloody diarrhea.

Despite the importance of O157:H7 serotype in causing life-threatening complications such as HUS and the isolation of this serotype from clinical specimens in Sao Paulo State, the relatively low prevalence of this serotype in healthy dairy and beef cattle in Brazil (8), as well as the occurrence of other non-O157 STEC strains associated with human infections (4,5,9), suggest that E. coli O157:H7 may be not as frequent as non-O157 STEC strains in our country.

Kinue Irino, * Tania M. Ibelli Vaz, *
Maria A.M.F. Kato, * Zita V.F. Naves, ([dagger])
Raquel Russo Lara, ([dagger])
Maria Elza Carvalho Marco, ([dagger])
Marilu M.M. Rocha, ([double dagger])
Tania P. Moreira, ([double dagger])
Tania A. T. Gomes, ([section])
and Beatriz E.C. Guth ([section])

* Instituto Adolfo Lutz, Sao Paulo,
Brazil; ([dagger]) Laboratorio de Analises
Clinicas Dr Joao Antonio Vozza,
Campinas, Sao Paulo, Brazil;
([double dagger]) Instituto Adolfo Lutz, Campinas, Sao
Paulo, Brazil; and ([section]) Universidade
Federal de Sao Paulo, Escola Paulista
de Medicina, Sao Paulo, Brazil

References

(1.) Riley LW, Remis RS, Helgerson SD, McGee H.B, Wells JC, Davis BD, et al. Hemorrhagic colitis associated with a rare Escherichia coli O157:H7 serotype. N Engl J Med 1983;308:681-5.

(2.) Nataro JP, Kaper JB. Diarrheagenic Escherichia coll. Clin Microbiol Rev 1998;11:142-201.

(3.) Giraldi R, Guth BEC, Trabulsi LR. Production of Shiga-like toxin among Escherichia coli strains and other bacteria isolated from diarrhea in Sao Paulo, Brazil. J Clin Microbiol 1990;28:1460-2.

(4.) Guth BEC, Ramos SRTS, Cerqueira AMF, Andrade JRC, Gomes TAT. Characterization of Shiga toxin-producing Escherichia coil (STEC) strains isolated from children in Sao Paulo, Brazil. 4th International Symposium and Workshop on Shiga toxin (Verocytotoxin)-producing Escherichia coli infections --VTEC 2000. Kyoto, Japan, 2000. p. 149.

(5.) Beutin L, Prada J, Zimmermann S, Stephan R, Orskov I, Orskov F. Enterohemolysin, a new type of hemolysin produced by some strains of enteropathogenic E. coli (EPEC). Zentralbl Bakteriol Mikrobiol Hyg [A] 1988;267:576-88.

(6.) Pollard DR, Johnson W., Lior H, Tyler SD, Rozee KR. Rapid and specific detection of verotoxin genes in Escherichia coli by the polymerase chain reaction. J Clin Microbiol 1990;28:540-5.

(7.) Goncalves AG, Campos LC, Gomes TAT, Rodrigues J, Sperandio V, Whittam T, et al. Virulence properties and clonal structure of strains of Escherichia coli O119 serotypes. Infect Immun 1997;652034-40.

(8.) Cerqueira AMF, Guth BEC, Joaquim RM, Andrade JRC. High occurrence of Shiga toxin-producing Escherichia coli (STEC) in healthy cattle in Rio de Janeiro State, Brazil. Vet Microbiol 1999;70:111-21.

(9.) Irino K, Gomes TAT, Vaz TMI, Kano E, Kato MAMF, Dias AMG, et al. Prevalence of Shiga toxin and intimin gene sequences among Escherichia coli of serogroups O26, O55, O111, O119 and O157 isolated in Sao Paulo, Brazil. In: Abstracts of the 4th International Symposium and Workshop on Shiga toxin (Verocytotoxin)-producing Escherichia coli infections. Kyoto, Japan, 2000. p. 107.

Guidelines for Letters. Letters discussing a recent Emerging Infectious Diseases article (400-500 words, 5-10 references) should be received within 4 weeks of the article's publication. Letters reporting preliminary data (500-1,000 words, 10 references) should not duplicate other material published or submitted for publication, should not be divided into sections, and should avoid figures or tables. All letters have the same authorship, financial disclosure, and acknowledgment requirements as full articles and should include a word count. For more guidance on manuscript preparation, see Emerging Infectious Diseases Instructions to Authors. Send letters to the Editor, Emerging Infectious Diseases, Centers for Disease Control and Prevention, 1600 Clifton Rd., MS D 61, Atlanta, GA 30333, USA, or e-mail: [e-mail].

Letters Editor: Patricia M. Quinlisk, Des Moines, Iowa, USA