DiarrhoeagenicEscherichia coli(DEC) is a leading cause of infectious diarrhoea worldwide. In recent years,Escherichia albertiihas also been implicated as a cause of human enteric diseases. This study describes the occurrence ofE. colipathotypes and serotypes associated with enteric illness and haemolytic uremic syndrome (HUS) isolated in Brazil from 2011 to 2016. Pathotypes isolated included enteropathogenicE. coli(EPEC), enteroaggregativeE. coli(EAEC), enterotoxigenicE. coli(ETEC), enteroinvasiveE. coli(EIEC) and Shiga toxin-producingE. coli(STEC). PCR of stool enrichments for DEC pathotypes was employed, andE. albertiiwas also sought. O:H serotyping was performed on all DEC isolates. A total of 683 DEC and 10E. albertiistrains were isolated from 5047 clinical samples. The frequencies of DEC pathotypes were 52.6% (359/683) for EPEC, 32.5% for EAEC, 6.3% for ETEC, 4.4% for EIEC and 4.2% for STEC. DEC strains occurred in patients from 3 months to 96 years old, but EPEC, EAEC and STEC were most prevalent among children. Both typical and atypical isolates of EPEC and EAEC were recovered and presented great serotype heterogeneity. HUS cases were only associated with STEC serotype O157:H7. TwoE. albertiiisolates belonged to serogroup O113 and one had thestx2f gene. The higher prevalence of atypical EPEC in relation to EAEC in community-acquired diarrhoea in Brazil suggests a shift in the trend of DEC pathotypes circulation as previously EAEC predominated. This is the first report ofE. albertiiisolation from active surveillance. These results highlight the need of continuing DEC andE. albertiisurveillance, as a mean to detect changes in the pattern of pathotypes and serotypes circulation and provide useful information for intervention and control strategies.

(1) Background: Pathogenic Escherichia coli are divided into two groups: diarrheagenic (DEC) and extraintestinal pathogenic (ExPEC) E. coli. ExPEC causing urinary tract infections (UTIs) are termed uropathogenic E. coli (UPEC) and are the most common cause of UTIs worldwide. (2) Methods: Here, we characterized 112 UPEC in terms of phylogroup, serotype, the presence of virulence factor-encoding genes, and antimicrobial resistance. (3) Results: The majority of the isolates were assigned into the phylogroup B2 (41.07%), and the serogroups O6 (12.5%) and O25 (8.9%) were the most frequent. Five hybrid UPEC (4.5%), with markers from two DEC pathotypes, i.e., atypical enteropathogenic (aEPEC) and enteroaggregative (EAEC) E. coli, were identified, and designated UPEC/aEPEC (one isolate) and UPEC/EAEC (four isolates), respectively. Three UPEC/EAEC harbored genes from the pap operon, and the UPEC/aEPEC carried ibeA. The highest resistance rates were observed for ampicillin (46.4%) and trimethoprim/sulfamethoxazole (34.8%), while 99.1% of the isolates were susceptible to nitrofurantoin and/or fosfomycin. Moreover, 9.8% of the isolates were identified as Extended Spectrum β-Lactamase producers, including one hybrid UPEC/EAEC. (4) Conclusion: Our data reinforce that hybrid UPEC/DEC are circulating in the city of Botucatu, Brazil, as uropathogens. However, how and whether these combinations of genes influence their pathogenicity is a question that remains to be elucidated.

In the past two decades, Shiga toxin-producing Escherichia coli (STEC) has been responsible for multiple large-scale outbreaks worldwide, affecting thousands of individuals. While surveillance systems in developed countries such as the United States, the United Kingdom, Europe, Australia, Japan, and Canada are well-established, data on STEC prevalence in developing nations remain sparse, partly due to the absence of well-structured molecular diagnostic networks or surveillance systems. This review analyzed 250 studies published between 2014 and 2024 across 39 developing countries in Africa, Asia, Latin America, and the Caribbean, yielding 8986 STEC isolates. Detailed serogroup and serotype data were available for 55.9% of these, with O111, O157, and O26 being most common in humans. In animals, O157:H7 was most frequent, while food isolates mirrored global trends with O157 and O111 dominance. Notably, O145, a serogroup frequently reported in the U.S. and Europe, was absent from the ‘’Top Seven’’ serogroups. Shiga toxin subtypes stx1a and stx2a were most prevalent in human cases. In animal isolates, stx2e was the most prevalent subtype, while stx2c was most commonly found in food samples. We recommend establishing reference laboratories in these regions to improve data quality, strengthen monitoring efforts, and reduce the burden of STEC infections globally.

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.

Enteroaggregative Escherichia coli (EAEC) is an enteropathogen that harbors a set of adhesins responsible for mediating adherence to epithelial cells in a stacked brick-like arrangement termed aggregative adherence (AA) pattern and is one of the main pathogens isolated from diarrheal patients worldwide. In the present study, we characterized 140 EAEC isolates, obtained from stool samples of individuals with diarrhea in Brazil, based on their phylogeny, adherence properties, and presence of major pilin-encoding genes for aggregative adherence fimbriae (AAF) and aggregate-forming pili (AFP). The majority of the EAEC isolates were assigned into the phylogroups A (57.9%), B1 (18.6%), and D (17.1%), while the serotypes O86:H2 (7.9%), O153:H2 (6.4%), O168:H4 (4.3%), O175:H28 (4.3%), and O73:H18 (3.6%) were the most frequent. A total of 78.6% of the isolates produced the AA pattern on HeLa cells and/or on the glass coverslips, and 69.3% were classified as biofilm producers on polystyrene. Interestingly, three isolates (2.1%) produced chain-like adherence (CLA), which is characterized by the formation of bacterial cell chains on the surface of epithelial cells. Major pilin-encoding genes were detected with the following frequencies: aggA (37.8%), agg3A (14.3%), agg4A (13.6%), agg5A (13.6%), aafA (9.3%), and afpA (8.6%). Additionally, four isolates (2.8%) harbored agg3A and agg5A concomitantly. Of note, all EAEC isolates producing CLA harbored agg4A . Our data indicate that the EAEC isolates studied have originated from several E. coli backgrounds, leading to the emergence of a heterogeneous group of enteropathogen. Moreover, we highlighted a distinct EAEC subgroup that produces CLA on infected cells. IMPORTANCE: Enteroaggregative Escherichia coli (EAEC) is a major cause of both acute and persistent diarrhea worldwide, with a particularly high prevalence in developing countries. In this study, we performed a comprehensive molecular and phenotypic characterization of 140 EAEC isolates obtained from both pediatric and adult patients with diarrheal disease. Our findings support the knowledge that EAEC represents a heterogeneous group of isolates that have emerged from distinct E. coli genetic backgrounds, primarily within phylogroups A, B1, and D. Although most isolates exhibited the characteristic aggregative adherence (AA) pattern on infected epithelial cells, a subset displayed the chain-like adherence (CLA) phenotype and carried the aatA , aggR , and agg4A genes. This scenario highlights the need for continuous surveillance to monitor the emergence of novel virulence strategies employed by EAEC to adhere to host cells and cause disease.