Acquisition of plasmids from Shiga toxin-producing Escherichia coli strains had low or neutral fitness cost on commensal E. coli.

Although it has been hypothesized that the acquisition of plasmids-especially those bearing virulence factors and antimicrobial resistance genes-increases the energetic burden and reduces the fitness of a bacterium in general, some results have challenged this view, showing little or no effect on fitness after plasmid acquisition, which may lead to change in the view that there are evolutionary barriers for a wide spread of such plasmids among bacteria. Here, to evaluate the fitness impact of plasmid-encoded antibiotic resistance and virulence genes, plasmids from O26:H11, O111:H8, and O118:H16 Shiga toxin-producing Escherichia coli (STEC) human and bovine isolates were transferred to the non-virulent E. coli HS and K-12 MG1655 strains. Sequencing and PCR were used to characterize plasmids, and to identify the presence of antimicrobial resistance and/or virulence genes. The fitness impact of plasmids encoding virulence and antimicrobial resistance upon bacterial hosts was determined by pairwise growth competition. Plasmid profile analysis showed that STEC strains carried one or more high and low molecular weight plasmids belonging to the B/O, F, I, K, P, Q, and/or X incompatibility groups encoding virulence genes (SPATE-encoding genes) and/or antimicrobial resistance genes (aadA1, strAB, tetA, and/or tetB). Competition experiments demonstrated that the biological cost of carriage of these plasmids by the commensal E. coli strain HS or the laboratory strain E. coli K-12 MG1655 was low or non-existent, ranging from - 4.7 to 5.2% per generation. This suggests that there are few biological barriers-or, alternatively, it suggests that there are biological barriers that we were not able to measure in this competition model-against the spread of plasmid encoding virulence and resistance genes from STEC to other, less pathogenic E. coli strains. Thus, our results, in opposition to a common view, suggest that the acquisition of plasmids does not significantly affect the bacteria fitness and, therefore, the theorized plasmid burden would not be a significant barrier for plasmid spread.

Acquisition of plasmids from Shiga toxin-producing Escherichia coli strains had low or neutral fitness cost on commensal E. coli

Although it has been hypothesized that the acquisition of plasmids—especially those bearing virulence factors and antimicrobial resistance genes—increases the energetic burden and reduces the fitness of a bacterium in general, some results have challenged this view, showing little or no effect on fitness after plasmid acquisition, which may lead to change in the view that there are evolutionary barriers for a wide spread of such plasmids among bacteria. Here, to evaluate the fitness impact of plasmid-encoded antibiotic resistance and virulence genes, plasmids from O26:H11, O111:H8, and O118:H16 Shiga toxin-producing Escherichia coli (STEC) human and bovine isolates were transferred to the non-virulent E. coli HS and K-12 MG1655 strains. Sequencing and PCR were used to characterize plasmids, and to identify the presence of antimicrobial resistance and/or virulence genes. The fitness impact of plasmids encoding virulence and antimicrobial resistance upon bacterial hosts was determined by pairwise growth competition. Plasmid profile analysis showed that STEC strains carried one or more high and low molecular weight plasmids belonging to the B/O, F, I, K, P, Q, and/or X incompatibility groups encoding virulence genes (SPATE-encoding genes) and/or antimicrobial resistance genes (aadA1, strAB, tetA, and/or tetB). Competition experiments demonstrated that the biological cost of carriage of these plasmids by the commensal E. coli strain HS or the laboratory strain E. coli K-12 MG1655 was low or non-existent, ranging from − 4.7 to 5.2% per generation. This suggests that there are few biological barriers—or, alternatively, it suggests that there are biological barriers that we were not able to measure in this competition model—against the spread of plasmid encoding virulence and resistance genes from STEC to other, less pathogenic E. coli strains. Thus, our results, in opposition to a common view, suggest that the acquisition of plasmids does not significantly affect the bacteria fitness and, therefore, the theorized plasmid burden would not be a significant barrier for plasmid spread.

Virulence Profiling and Molecular Typing of Shiga Toxin-Producing E. coli (STEC) from Human Sources in Brazil.

Since no recent data characterizing Shiga toxin-producing E. coli (STEC) from human infections in Brazil are available, the present study aimed to investigate serotypes, stx genotypes, and accessory virulence genes, and also to perform pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST) of 43 STEC strains recovered from 2007 to 2017. Twenty-one distinct serotypes were found, with serotype O111:H8 being the most common. However, serotypes less frequently reported in human diseases were also found and included a hybrid STEC/ETEC O100:H25 clone. The majority of the strains carried stx1a as the sole stx genotype and were positive for the eae gene. Regarding the occurrence of 28 additional virulence genes associated with plasmids and pathogenicity islands, a diversity of profiles was found especially among the eae-harboring strains, which had combinations of markers composed of up to 12 distinct genes. Although PFGE analysis demonstrated genetic diversity between serotypes such as O157:H7, O111:H8, O26:H11, O118:H16, and O123:H2, high genetic relatedness was found for strains of serotypes O24:H4 and O145:H34. MLST allowed the identification of 17 distinct sequence types (STs) with ST 16 and 21 being the most common ones. Thirty-five percent of the strains studied were not typeable by the currently used MLST approach, suggesting new STs. Although STEC O111:H8 remains the leading serotype in Brazil, a diversity of other serotypes, some carrying virulence genes and belonging to STs incriminated as causing severe disease, were found in this study. Further studies are needed to determine whether they have any epidemiological relevance.

Novel Hybrid of Typical Enteropathogenic Escherichia coli and Shiga-Toxin-Producing E. coli (tEPEC/STEC) Emerging From Pet Birds.

Exotic psittacine birds have been implicated as reservoir of diarrheagenic Escherichia coli (E. coli), including enteropathogenic E. coli (EPEC) and Shiga-toxin producing E. coli (STEC). Here, we present a genotypic and phenotypic characterization of typical EPEC/STEC hybrid strains isolated from exotic psittacine birds. The strains were positive for eae, bfpA, and stx2f genes, belong to serotype O137:H6 and ST2678. Two strains were subject to whole genome sequencing, confirming the presence of the virulence factors of both E. coli pathotypes. Phenotypical in vitro tests confirmed their ability to adhere to HeLa cells and cause cytotoxicity to Vero cells. The rabbit ileal loop assays showed the attaching and effacing lesion, in addition to inflammatory process and overproduction of intestinal mucus. This is the first report of hybrid typical EPEC/STEC (O137:H6/ST2678) strains isolated from companion psittacine birds and the results suggest zoonotic risks.

Novel hybrid of Typical Enteropathogenic Escherichia coli and Shiga-Toxin-Producing E. coli (tEPEC/STEC) emerging from pet birds

Exotic psittacine birds have been implicated as reservoir of diarrheagenic Escherichia coli (E. coli), including enteropathogenic E. coli (EPEC) and Shiga-toxin producing E. coli (STEC). Here, we present a genotypic and phenotypic characterization of typical EPEC/STEC hybrid strains isolated from exotic psittacine birds. The strains were positive for eae, bfpA, and stx2f genes, belong to serotype O137:H6 and ST2678. Two strains were subject to whole genome sequencing, confirming the presence of the virulence factors of both E. coli pathotypes. Phenotypical in vitro tests confirmed their ability to adhere to HeLa cells and cause cytotoxicity to Vero cells. The rabbit ileal loop assays showed the attaching and effacing lesion, in addition to inflammatory process and overproduction of intestinal mucus. This is the first report of hybrid typical EPEC/STEC (O137:H6/ST2678) strains isolated from companion psittacine birds and the results suggest zoonotic risks.

Novel hybrid of Typical Enteropathogenic Escherichia coli and Shiga-Toxin-Producing E. coli (tEPEC/STEC) emerging from pet birds

Exotic psittacine birds have been implicated as reservoir of diarrheagenic Escherichia coli (E. coli), including enteropathogenic E. coli (EPEC) and Shiga-toxin producing E. coli (STEC). Here, we present a genotypic and phenotypic characterization of typical EPEC/STEC hybrid strains isolated from exotic psittacine birds. The strains were positive for eae, bfpA, and stx2f genes, belong to serotype O137:H6 and ST2678. Two strains were subject to whole genome sequencing, confirming the presence of the virulence factors of both E. coli pathotypes. Phenotypical in vitro tests confirmed their ability to adhere to HeLa cells and cause cytotoxicity to Vero cells. The rabbit ileal loop assays showed the attaching and effacing lesion, in addition to inflammatory process and overproduction of intestinal mucus. This is the first report of hybrid typical EPEC/STEC (O137:H6/ST2678) strains isolated from companion psittacine birds and the results suggest zoonotic risks.

Diversity of Shiga toxin-producing Escherichia coli in sheep flocks of Paraná State, southern Brazil.

Sheep constitute an important source of zoonotic pathogens as Shiga toxin-producing Escherichia coli (STEC). In this study, the prevalence, serotypes and virulence profiles of STEC were investigated among 130 healthy sheep from small and medium farms in southern Brazil. STEC was isolated from 65 (50%) of the tested animals and detected in all flocks. A total of 70 STEC isolates were characterized, and belonged to 23 different O:H serotypes, many of which associated with human disease, including hemolytic-uremic syndrome (HUS). Among the serotypes identified, O76:H19 and O65:H- were the most common, and O75:H14 and O169:H7 have not been previously reported in STEC strains. Most of the STEC isolates harbored only stx1, whereas the Stx2b subtype was the most common among those carrying stx2. Enterohemolysin (ehxA) and intimin (eae) genes were detected in 61 (87.1%) and four (5.7%) isolates, respectively. Genes encoding putative adhesins (saa, iha, lpfO113) and toxins (subAB and cdtV) were also observed. The majority of the isolates displayed virulence features related to pathogenesis of STEC, such as adherence to epithelial cells, high cytotoxicity and enterohemolytic activity. Ovine STEC isolates belonged mostly to phylogenetic group B1. PFGE revealed particular clones distributed in some farms, as well as variations in the degree of genetic similarity within serotypes examined. In conclusion, STEC are widely distributed in southern Brazilian sheep, and belonged mainly to serotypes that are not commonly reported in other regions, such as O76:H19 and O65:H-. A geographical variation in the distribution of STEC serotypes seems to occur in sheep.

Humoral immune response to Shiga Toxin 2 (Stx2) among Brazilian urban children with hemolytic uremic syndrome and healthy controls.

BACKGROUND: Shiga toxin (Stx)-producing Escherichia coli (STEC) infection is associated with hemolytic uremic syndrome (HUS), the main cause of acute renal failure in early childhood. Stx is essential in the pathogenesis of HUS, which has been mostly related to Stx2-producing isolates. Very limited data exist on the immune response to STEC in the Brazilian population. In this study, the prevalence of immunoglobulin G (IgG) antibodies to Stx2 was investigated in sera of children diagnosed with HUS and of healthy children in the city of São Paulo, Brazil. METHODS: IgG-antibody reactivity to Stx2 was determined by immunoblotting (WB) and enzyme-linked immunosorbent assay (ELISA) in sera from 13 children with HUS aged 8 months to 6 years and 54 healthy urban children aged 5 months to 7 years. RESULTS: A positive immune response to the A and B subunits of Stx2 was observed in 46.1% HUS patients and in 16.6% healthy individuals by WB. All HUS patients and 62.9% healthy children showed IgG antibodies to the Stx2 A subunit. The frequency of antibodies to both subunits or only to the A subunit of Stx2 was significantly higher in HUS patients than controls (p<0.05). Also, the mean OD value obtained by ELISA was higher in that group. Considering children's age, the frequency of reactivity to either the A subunit or both subunits of Stx2 was considerably higher in HUS children up to three years old compared to controls in the same age range. Moreover, in almost 37% of healthy children, no immune response to Stx2 was detected independently of the child's age. CONCLUSIONS: The seroepidemiolgy of anti-Stx2 antibodies was described for the first time in healthy children and children with HUS in Brazil. The percentage of individuals showing antibodies against Stx2 was higher among HUS patients than controls, and in spite of the low number of notified HUS cases, STEC strains are circulating in our settings. In addition, the results obtained also corroborated previous data on the increased sensitivity and specificity of WB compared to toxin-based enzyme immunoassays.

Shiga toxigenic and atypical enteropathogenic Escherichia coli in the feces and carcasses of slaughtered pigs.

Escherichia coli is a pathogen of major importance in swine and public health. To determine the prevalence of Shiga toxigenic E. coli (STEC) and enteropathogenic E. coli (EPEC), samples were collected from the feces and carcasses of swines. In total, 441 samples were collected in four samplings, of which 141 samples tested positive for either the stx1, stx2, and/or eae genes. From the positive samples, one STEC and 15 atypical EPEC (aEPEC) isolates were obtained, and all originated from the same sampling. In addition to eae, lpfA(O157/OI-141), ehxA, toxB, and lpfA(O113) were present in the aEPEC isolates. The only stx2-containing isolate carried stx2e and belonged to serotype O103:HNT. Resistance to four or more antimicrobials was found in almost half of the isolates, and some isolates shared the same fingerprint patterns by enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR). The presence of certain virulence genes and the high level of resistance to antimicrobials, as well as the possible fecal contamination of carcasses showed that some of the isolates are of public health concern.

Determination of adhesin gene sequences in, and biofilm formation by, O157 and non-O157 Shiga toxin-producing Escherichia coli strains isolated from different sources.

Biofilm formation by Shiga toxin-producing Escherichia coli (STEC) has been associated with the expression of different adhesins (type 1 fimbria, curli, Ag43, Cah, and EhaA). In this study, biofilm formation and the presence of adhesin-related gene sequences were determined by PCR in 18 O157 strains and 33 non-O157 strains isolated from different sources (human, animal, food, and water). The expression of different adhesins was also assessed by reverse transcription-PCR (RT-PCR), Congo red agar plates, and mannose-sensitive hemagglutination (MSHA) assay. Biofilm formation occurred in 5/18 (28%) O157 STEC strains and 17/33 (51%) non-O157 STEC strains from different serotypes and sources, when the assays were performed at 28°C for 48 h. Among the non-O157 biofilm-producing isolates, 12/17 (71%) expressed type 1 fimbriae and 11/17 (65%) expressed curli and produced cellulose, while 8/17 (47%) were considered to be Ag43(+) by RT-PCR. Among O157 strains, a close correlation was observed between biofilm formation and expression of curli and cellulose. In non-O157 strains, it seems that, in addition to the presence of curli, the ability to form biofilm is associated with the presence of other factors such as type 1 fimbriae and autotransporter proteins, which may contribute to the persistence of these organisms in the environment.

Determination of Adhesin Gene Sequences in, and Biofilm Formationby, O157 and Non-O157 Shiga Toxin-Producing Escherichia coli Strains Isolated from Different Sources

Biofilm formation by Shiga toxin-producing Escherichia coli (STEC) has been associated with the expressionof different adhesins (type 1 fimbria, curli, Ag43, Cah, and EhaA). In this study, biofilm formation and thepresence of adhesin-related gene sequences were determined by PCR in 18 O157 strains and 33 non-O157strains isolated from different sources (human, animal, food, and water). The expression of different adhesinswas also assessed by reverse transcription-PCR (RT-PCR), Congo red agar plates, and mannose-sensitivehemagglutination (MSHA) assay. Biofilm formation occurred in 5/18 (28%) O157 STEC strains and 17/33(51%) non-O157 STEC strains from different serotypes and sources, when the assays were performed at 28°Cfor 48 h. Among the non-O157 biofilm-producing isolates, 12/17 (71%) expressed type 1 fimbriae and 11/17(65%) expressed curli and produced cellulose, while 8/17 (47%) were considered to be Ag43 by RT-PCR.Among O157 strains, a close correlation was observed between biofilm formation and expression of curli andcellulose. In non-O157 strains, it seems that, in addition to the presence of curli, the ability to form biofilm isassociated with the presence of other factors such as type 1 fimbriae and autotransporter proteins, which maycontribute to the persistence of these organisms in the environment.

Molecular typing of antimicrobial-resistant Shiga-toxin-producing Escherichia coli strains (STEC) in Brazil.

Antimicrobial resistance patterns and molecular characteristics were determined in thirty-two Shiga-toxin-producing Escherichia coli (STEC) strains previously identified in São Paulo State associated with human infections (n = 21) and in cattle feces (n = 11). The highest resistance rates were identified for tetracycline (100%), streptomycin (78%) and trimethoprim-sulfamethoxazole (56%). Eleven STEC strains showed resistance to ampicillin and carried bla(TEM) that was confirmed as bla(TEM-1) in one representative isolate. The class 1 integrase gene (intI1) was detected in seven (22%) strains, and most of them belonged to the O111:H8 serotype. The class 1 integron was located on plasmids in five of the seven STEC strains, and conjugation assays confirmed the plasmid support of those resistant determinants. STEC strains were genetically classified into the B1 group, and PFGE analysis showed that most of the strains in each serogroup were grouped into the same cluster (80-97% similarity). The presence of a class 1 integron and bla(TEM-1) genes is described for the first time among STEC isolates in Brazil and clearly represents a public health concern.

Set of virulence genes and genetic relatedness of O113 : H21 Escherichia coli strains isolated from the animal reservoir and human infections in Brazil.

Escherichia coli strains of serotype O113 : H21 are commonly described as belonging to a Shiga toxin (Stx)-producing E. coli (STEC) pathotype worldwide. Albeit this STEC serotype is frequently identified among cattle and other domestic animals, to the best of our knowledge no human infections associated with STEC O113:H21 have been registered in Brazil to date. Here, we report the virulence profile and genetic relatedness of a collection of O113:H21 E. coli strains mainly isolated from the animal reservoir aimed at determining their potential as human pathogens. The strains from the animal reservoir (n=34) were all classified as STEC, whereas the few isolates recovered so far from human diarrhoea (n=3) lacked stx genes. Among the STEC, the stx2d-activatable gene was identified in 85% of the strains that also carried lpfAO113, iha, saa, ehxA, subAB, astA, cdt-V, espP, espI and epeA; the human strains harboured only lpfAO113, iha and astA. All the strains except one, isolated from cattle, were genetically classified as phylogenetic group B1. High mass plasmids were observed in 25 isolates, but only in the STEC group were these plasmids confirmed as the STEC O113 megaplasmid (pO113). Many closely related subgroups (more than 80% similarity) were identified by PFGE, with human isolates clustering in a subgroup separate from most of the animal isolates. In conclusion, potentially pathogenic O113:H21 STEC isolates carrying virulence markers in common with O113:H21 clones associated with haemolytic uraemic syndrome cases in other regions were demonstrated to occur in the natural reservoir in our settings, and therefore the risk represented by them to public health should be carefully monitored.

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.

Prevalence and characteristics of Shiga toxin-producing Escherichia coli (STEC) strains in ground beef in São Paulo, Brazil

This study aims to assess the prevalence of Shiga toxin-producing Escherichia coli (STEC) in ground beef collected in two cities located in the State of São Paulo, Brazil. A total of 250 samples of raw ground beef were collected in local grocery stores during the period of March to December 2002 in the cities of Ribeirão Preto (114 samples) and Campinas (136 samples), São Paulo State, Brazil. The samples were processed according to standard methods. The resulting 591 E.coli colonies were screened for STEC by hybridization assays using the specific DNA probes, stx1,stx2 and eae. Further characterization of STEC isolates included the search for the ehxA sequence, detection of enterohemolysin and expression of Shiga toxin using the Vero cell assay. STEC isolates belonging to serotypes O93:H19, ONT:HNT, ONT:H7, and O174:HNT we recovered from four samples (3.5 percent) collected in Ribeirão Preto. All samples from Campinas were negative for STEC. Three of the strains carried stx2 and ehxA sequences while one harbored stx1,stx2 and ehxA sequences. Considering that among foods of animal origin, ground beef is an important vehicle for STEC transmission, these data emphasize the need of a closer surveillance of these microorganisms. They can survive in unfavorable conditions specially when the products are refrigerated or frozen for long periods of time and can be the cause of outbreaks affecting a great number of consumers.

O objetivo deste estudo foi verificar a ocorrência de Escherichia coli produtora de toxina Shiga (STEC) em amostras de carne moída crua comercializadas em duas cidades do Estado de São Paulo, Brasil. Um total de 250 amostras de carne moída crua foi coletado de açougues locais durante o período de Março a Dezembro de 2002, nas cidades de Ribeirão Preto (114 amostras) e de Campinas (136 amostras), Estado de São Paulo, Brasil. As amostras foram processadas de acordo com os métodos de referência. Um total de 591 colônias de E.coli foi submetido à técnica de hibridização de colônias usando sondas específicas de DNA para a detecção das seqüências stx1,stx2 e eae. Caracterizações adicionais das cepas STEC incluíram a pesquisa da seqüência ehxA, a detecção da enterohemolisina e a pesquisa da expressão de toxina Shiga utilizando testes com células Vero. Em quatro amostras (3,5 por cento) coletadas em Ribeirão Preto, foram encontradas cepas STEC, mas todas aquelas da região de Campinas foram negativas. As cepas de STEC pertenciam aos sorotipos O93:H19, ONT:HNT, ONT:H7, e O174:HNT. Três cepas tinham o perfil stx2 ehxA e uma era portadora das seqüências stx1,stx2 e ehxA. Considerando que entre os alimentos de origem animal, a carne moída ainda representa um importante veículo de transmissão de STEC, estes dados alertam para a necessidade de uma vigilância da presença destes microrganismos capazes de sobreviver em condições desfavoráveis, especialmente quando os produtos são refrigerados ou congelados por longos períodos, podendo ser causas de importantes surtos afetando grande número de consumidores.

Production and release of heat-labile toxin by wild-type human-derived enterotoxigenic Escherichia coli.

Production and release of heat-labile toxin (LT) by wild-type enterotoxigenic Escherichia coli (ETEC) strains, isolated from diarrheic and asymptomatic Brazilian children, was studied under in vitro and in vivo conditions. Based on a set of 26 genetically diverse LT(+) enterotoxigenic E. coli strains, cell-bound LT concentrations varied from 49.8 to 2415 ng mL(-1). The amounts of toxin released in culture supernatants ranged from 0% to 50% of the total synthesized toxin. The amount of LT associated with secreted membrane vesicles represented <5% of the total toxin detected in culture supernatants. ETEC strains secreting higher amounts of LT, but not those producing high intracellular levels of cell-bound toxin, elicited enhanced fluid accumulation in tied rabbit ileal loops, suggesting that the strain-specific differences in production and secretion of LT correlates with symptoms induced in vivo. However, no clear correlation was established between the ability to produce and secrete LT and the clinical symptoms of the infected individuals. The present results indicate that production and release of LT by wild-type human-derived ETEC strains are heterogeneous traits under both in vitro and in vivo growth conditions and may impact the clinical outcomes of infected individuals.

Human colostrum contains IgA antibodies reactive to colonization factors I and II of enterotoxigenic Escherichia coli.

Diarrhea is an important cause of morbidity and mortality amongst infants of low socio-economic levels in developing countries and in travelers who visit such areas. Enterotoxigenic E. coli strains express two sets of virulence-associated factors: enterotoxins (heat-stable toxins or heat-labile toxins) and colonization factors. Studies have shown that breast-feeding protects infants against infectious diseases, such as diarrhea, as it presents a great variety of immunological components. The aim of this study was to analyze the reactivity of immunoglobulin A from human colostrum to colonization factor antigens I and II. The colostrum ability in preventing enterotoxigenic E. coli adhesion to Caco-2 cells was also evaluated. Colostrum samples were collected from 32 healthy women, and a human colostrum pool was prepared. Enterotoxigenic E. coli strains expressing colonization factor antigens I and II were utilized. The colostrum pool and individual samples showed variable antienterotoxigenic E. coli immunoglobulin A titers, that were reactive with colonization factor antigen I and CS1/CS3 (colonization factor antigen II). The human colostrum pool and individual samples inhibited enterotoxigenic E. coli colonization factor antigen I and II adhesion to Caco-2 cells, at variable levels, and this ability was a result of immunoglobulin A antibodies reactive to these colonization factors. The immunoglobulin A-depleted pool lost this inhibitory ability. As bacterial adhesion is the initial mechanism of enterotoxigenic E. coli infection, breast-feeding could protect the offspring against diarrhea caused by this agent.

Enterotoxigenic Escherichia coli: An overview

Enterotoxigenic Escherichia coli is an important cause of traveler's diarrhea and diarrheal illnesses in children in the developing world. In this presentation we will focus on the main virulence attributes of this pathogenic category of E. coli, and discuss the evolution of studies conducted in our laboratory