Tânia M. I. Vaz

Emerging enteropathogenic Escherichia coli strains

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.

Virulence Properties and Characteristics of Shiga Toxin-Producing Escherichia coli in São Paulo, Brazil, from 1976 through 1999

ABSTRACT Twenty-nine Shiga toxin-producing Escherichia coli (STEC) strains were identified in a collection of 2,607 isolates from patients with diarrhea in São Paulo, Brazil, from 1976 to 1999. The STEC strains belonged mainly to serotypes O111:HNM (HNM, nonmotile) (13 of 29 [44.8%]), O111:H8 (7 of 29 [24%]), and O26:H11 (4 of 29 [13.8%]); stx1eae (26 of 29 [89.6%]), in combination with either enterohemorrhagic E. coli hlyA (11 of 26 [42%]) or astA (24 of 26 [92.3%]), prevailed. The O111 STEC strains were distinguished by their inability to decarboxylate lysine. The predominance of STEC O111 and O26 since the late 1970s and the identification of STEC serotypes O55:H19, O93:H19, and O118:H16 in association with human infections in Brazil are described for the first time.

Multiclonal Outbreak of Klebsiella pneumoniae Producing Extended-Spectrum β-Lactamase CTX-M-2 and Novel Variant CTX-M-59 in a Neonatal Intensive Care Unit in Brazil

ABSTRACT An outbreak of cephalosporin-resistant Klebsiella pneumoniae occurred in a neonatal intensive care unit in São Paulo, Brazil. Of the 10 pulsotypes identified during the outbreak and follow-up periods, nine produced CTX-M-2 or its new variant CTX-M-59 and one produced SHV-5. blaCTX-M-2/59 genes were located on closely related plasmids that were transferable.

First Shiga toxin-producing Escherichia coli isolate from a patient with hemolytic uremic syndrome, Brazil.

To the Editor: Infection by Shiga toxin (Stx)-producing Escherichia coli (STEC), particularly strains of serotype O157:H7, can cause sporadic cases and outbreaks of diarrhea, hemorrhagic colitis (HC), and hemolytic uremic syndrome (HUS) (1). Some other serotypes (e.g., O26:H11, O111:H8, O111:NM, and O113:H21) share a similar pathogenic potential. STEC are distributed worldwide, but most of the HC and HUS cases were reported from industrialized nations of the Northern and Southern hemisphere (2). In South America, HUS is a major cause of acute renal failure in infants in Argentina (3) and Chile (4). However, in Brazil human STEC infections have been restricted to sporadic cases of nonbloody diarrhea (5,6). Although a high frequency of STEC strains was recently found in foods and animal reservoirs (7,8), only some of the serotypes identified in animals (8) were recognized as causes of human illness (e.g., O157:H7, O22:H16, O82:H8, and NT:H21). Moreover, there is currently no nationwide surveillance system for HUS in Brazil, and STEC-associated HUS has not been previously reported in our country. We describe the case of an 8-month-old boy from a northeastern state in Brazil, who was admitted to the emergency room of Hospital Sao Paulo, Sao Paulo, on March 17, 2001; the boy had anemia, oliguria, and edema of lower extremities. He had an acute diarrheal prodromal illness 3 weeks before hospital admission. On the same day as admission, respiratory failure developed, and the child was transferred to the pediatric intensive-care unit of the hospital. The boy had hemolytic anemia (hemoglobin level 11.9 g/dL at admission, and 9.1 g/dL several days later), renal failure (blood urea nitrogen 43.8 mg/dL and serum creatinine 1.5 mg/dL), and thrombocytopenia (platelet count of 70,000/mm3), leading to a diagnosis of HUS. The patient received treatment with fresh frozen plasma and needed renal support (peritoneal dialysis) for 7 days. Once renal function was reestablished, the patient’s outcome was good. Feces were collected as soon as HUS was suspected and plated onto MacConkey Sorbitol Agar (Difco, Becton Dickinson Microbiology Systems, Sparks, MD). Only sorbitol-positive colonies grew and were biochemically identified as E. coli by standard procedures. The E. coli isolates expressed Stx1, as identified by cytotoxicity and neutralization assays on Vero cells (5). Presence of stx1 and intimin (eae) gene sequences was confirmed by polymerase chain reaction (9,10). The E. coli strain belonged to serotype O26:H11 and produced enterohemorragic E. coli hemolysin (enterohemolysin). This report is the first on the isolation of an STEC strain in a HUS patient in Brazil. The serotype O26:H11 has been described as agent of HC and HUS in other countries and was the second most frequent serotype found in STEC strains isolated from diarrheal cases in our settings (6). Moreover, expression of Stx1 and enterohemolysin and the presence of eae are virulent characteristics usually found in the human STEC strains isolated so far in Brazil. These findings show the importance of looking for non-O157 STEC strains besides O157:H7 in patients with HC and HUS in Brazil. Surveillance for HUS, either nationally or in sentinel population-based studies, should be performed in Brazil, and studies on the occurrence of HUS and its association with STEC infections are under investigation in our laboratory.

Diversity of virulence profiles of Shiga toxin-producing Escherichia coli serotypes in food-producing animals in Brazil

The prevalence, serotypes and virulence profiles of Shiga toxin-producing Escherichia coli (STEC) were investigated in 205 healthy beef and dairy cattle, and 106 goats reared in the southeastern region of Minas Gerais State, Brazil. The prevalence of STEC was 57.5% (61/106) in goats, 39.2%, (40/102) in beef cattle and 17.5% (18/103) in dairy cattle. Among the 514 STEC isolates, 40 different serotypes were found and some of them were identified in a specific host. STEC isolates harboring stx1 corresponded to 15.6% (28/180), 26.7% (16/60) and 24.1% (66/274) in beef cattle, dairy cattle and goats, respectively. stx2 was found in 30% (54/180), 53.3% (32/60) and 34.7% (95/274) of beef and dairy cattle, and goats. stx1 plus stx2 sequences were harbored by 54.4% (98/180), 20% (12/60) and 41.2% (113/274) of beef cattle, dairy cattle and goats, respectively. The eae sequence was found in 15% (9/60) and 0.6% (1/180) of STEC isolates from dairy and beef cattle, respectively, and the toxB gene was found only in one O157:H7 strain isolated from beef cattle. Strains with the genetic profiles stx2 ehxA iha saa and stx1 stx2 ehxA iha saa were the most prevalent among STEC isolates from cattle. Profiles stx1 stx2 ehxA iha, stx2, and stx1 iha accounted for 75.5% (207 /274) of the STEC isolates from goats. While STEC strains carrying either stx2 alone or associated with stx1 were found more frequently in cattle, those harboring sequences stx1c and stx2d alone or associated with stx1c predominated in goats. Our data show a diversity of STEC strains in food-producing animals, most of them carrying genes linked to severe forms of human diseases.

Virulence markers and serotypes of Shiga toxin-producing Escherichia coli, isolated from cattle in Rio Grande do Sul, Brazil

Aims:  To determine the prevalence of Shiga toxin‐producing Escherichia coli (STEC) and serotypes and virulence markers of the STEC isolates from beef and dairy cattle in Rio Grande do Sul, Brazil.

Prevalence and Characteristics of the O122 Pathogenicity Island in Typical and Atypical Enteropathogenic Escherichia coli Strains

ABSTRACT The presence of the pathogenicity island (PAI) O122 genes, efa1 (lifA), sen, pagC, nleB, and nleE, in typical and atypical enteropathogenic Escherichia coli (EPEC) strains was investigated. The simultaneous occurrence of all genes was statistically associated with diarrhea due to atypical EPEC. Detection of the complete PAI O122 could aid in the identification of potential pathogenic strains of atypical EPEC.

Water Buffaloes (Bubalus bubalis) Identified as an Important Reservoir of Shiga Toxin-Producing Escherichia coli in Brazil

ABSTRACT The presence of Shiga toxin-producing Escherichia coli (STEC) in water buffaloes is reported for the first time in South America. The prevalence of STEC ranged from 0 to 64% depending on the farm. STEC isolates exhibiting the genetic profiles stx1stx2ehxA iha saa and stx2ehxA iha saa predominated. Of the 20 distinct serotypes identified, more than 50% corresponded to serotypes associated with human diseases.

Subtilase Cytotoxin-Encoding subAB Operon Found Exclusively among Shiga Toxin-Producing Escherichia coli Strains

ABSTRACT The presence of subAB was investigated for 3,453 Escherichia coli strains of various pathogenic categories. The occurrence of other virulence genes in subAB-positive strains was investigated. The subAB operon was detected among some Shiga toxin-producing E. coli (STEC) serotypes devoid of eae and carrying ehxA. Most subAB-positive strains also harbored stx 2, iha, saa, and lpfA O113.

Escherichia coli Strains of Serotype O51:H40 Comprise Typical and Atypical Enteropathogenic E. coli Strains and Are Potentially Diarrheagenic

ABSTRACT Escherichia coli strains of serotype O51:H40 were studied with regard to the presence of several virulence properties and their genetic diversity and enteropathogenicity in rabbit ileal loops. This serotype encompasses potential enteropathogenic strains mostly classified as being atypical enteropathogenic E. coli (EPEC) strains, which are genetically closer to enterohemorrhagic E. coli than to typical EPEC strains.