New enterovirulent Escherichia coli serogroup 64474 showing antigenic and genotypic relationships to Shigella boydii 16

Structural elucidation of the O-antigen polysaccharide from shigatoxin-producing E. coli O179 using genetic information, NMR spectroscopy and the CASPER program

The serological properties of the O-antigen polysaccharide region of the lipopolysaccharides are used to differentiate E. coli strains into serogroups. In this study, we report the structure elucidation of the O-specific chain of E. coli O179 using NMR data, the program CASPER and analysis of biosynthetic information available in the E. coli O-antigen Database (ECODAB). The presence of genes that encode enzymes involved in the biosynthesis of the GDP-Man and UDP-GlcA within the O-antigen gene cluster of the bacteria indicates that the corresponding residues could be present in the polysaccharide. Furthermore, the occurrence of four genes that encode for glycosyltransferases indicates that the polysaccharide is composed of pentasaccharide repeating units; a bioinformatics approach based on predictive glycosyltransferase functions present in ECODAB revealed that the β-d-Manp-(1→4)-β-d-Manp-(1→3)-d-GlcpNAc structural element could be present in the O-specific chain. NMR spectroscopy data obtained from homonuclear and heteronuclear 2D NMR spectra (1H,1H-TOCSY, 1H,13C-HSQC, 1H,13C-H2BC and 1H,13C-HMBC) were analyzed using the CASPER program, revealing the following arrangement of monosaccharide residues as the most probable structure: →4)-α-d-GlcpA-(1→3)-[β-d-Glcp-(1→2)]β-d-Manp-(1→4)-β-d-Manp-(1→3)-β-d-GlcpNAc-(1→, which was further confirmed using 2D homonuclear 1H,1H-COSY and 1H,1H-NOESY spectra. The functions of the α-gluconosyltransferase and the β-glucosyltransferase were predicted using structural alignment of AlphaFold-predicted 3D structures. This O-antigen polysaccharide shares structural similarities with those of E. coli O6 and O188, S. boydii type 16, and the capsular polysaccharide of E. coli K43, explaining the serological cross-reactivities observed with strains belonging these O- and K-antigen groups.

Diversity of Potentially Pathogenic Escherichia coli O104 and O9 Serogroups Isolated before 2011 from Fecal Samples from Children from Different Geographic Regions

In 2011, an outbreak of hemorrhagic colitis and hemolytic uremic syndrome (HUS) was reported in Europe that was related to a hybrid STEAEC of Escherichia coli (E. coli) O104:H4 strain. The current study aimed to analyze strains of E. coli O104 and O9 isolated before 2011. The study included 47 strains isolated from children with and without diarrhea between 1986 and 2009 from different geographic regions, as well as seven reference strains. Serotyping was carried out on 188 anti-O and 53 anti-H sera. PCR was used to identify DEC genes and phylogenetic groups. Resistance profiles to antimicrobials were determined by diffusion in agar, while PFGE was used to analyze genomic similarity. Five serotypes of E. coli O104 and nine of O9 were identified, as well as an antigenic cross-reaction with one anti-E. coli O9 serum. E. coli O104 and O9 presented diarrheagenic E. coli (DEC) genes in different combinations and were located in commensal phylogenetic groups with different antimicrobial resistance. PFGE showed that O104:H4 and O9:(H4, NM) strains from SSI, Bangladesh and México belong to a diverse group located in the same subgroup. E. coli O104 and O9 were classified as commensal strains containing DEC genes. The groups were genetically diverse with pathogenic potential making continued epidemiologic surveillance important.

Identification of Two New Sequences of Flagellin-Encoding Gene in Escherichia coli Using PCR and Sequencing-Based Methods

Escherichia coli has traditionally been serotyped using antisera against the O and H antigens. However, a proportion of E. coli isolates are nonmotile and, in addition, some isolates do not react with the currently available H-typing sera. Alternative molecular methods have been developed based on the detection of genes encoding for H antigens. In this study, we studied 13 serologically nontypable H antigen E. coli strains using polymerase chain reaction (PCR) and sequencing-based methods. We found two new sequences of flagellin-encoding gene, for each of which a specific antiserum was produced to confirm their expression. Sequencing of the flagellin gene offers a rapid determination of E. coli H antigens and could be used to detect potential novel flagellar antigens.

Structural analysis of the O-antigen polysaccharide from Escherichia coli O188

The structure of the O-antigen from Escherichia coli reference strain O188 (E. coli O188:H10) has been investigated. The lipopolysaccharide shows a typical nonrandom modal chain-length distribution and the sugar and absolute configuration analysis revealed d-Man, d-Glc, d-GlcN and d-GlcA as major components. The structure of the O-specific polysaccharide was determined using one- and two-dimensional ¹H and ¹³C NMR spectroscopy experiments, where inter-residue correlations were identified by ¹H,¹³C-heteronuclear multiple-bond correlation and ¹H,¹H-NOESY experiments, which revealed that it consists of pentasaccharide repeating units with the following structure: Biosynthetic aspects and NMR analysis are consistent with the presented structure as the biological repeating unit. The O-antigen of Shigella boydii type 16 differs only in that it carries O-acetyl groups to ~50% at O6 of the branch-point mannose residues. A molecular model of the E. coli O188 O-antigen containing 20 repeating units extends ~100 Å, which is similar to the height of the periplasmic portion of polysaccharide co-polymerase Wzz proteins that regulate the O-antigen chain length of lipopolysaccharides in the Wzx/Wzy biosynthetic pathway.

Molecular and phenotypic characterization of diarrheagenic Escherichia coli isolated from groundwater in rural areas in southern Brazil

Water-borne diseases like diarrheagenic Escherichia coli (DEC)-induced gastroenteritis are major public health problems in developing countries. In this study, the microbiological quality of water from mines and shallow wells was analyzed for human consumption. Genotypic and phenotypic characterization of DEC strains was performed. A total of 210 water samples was analyzed, of which 153 (72.9%) contained total coliforms and 96 (45.7%) E. coli. Of the E. coli isolates, 27 (28.1%) contained DEC genes. The DEC isolates included 48.1% Shiga toxin-producing E. coli (STEC), 29.6% enteroaggregative E. coli (EAEC), 14.9% enteropathogenic E. coli (EPEC), 3.7% enterotoxigenic E. coli (ETEC), and 3.7% enteroinvasive E. coli (EIEC). All the STECs had cytotoxic effects on Vero cells and 14.8% of the DEC isolates were resistant to at least one of the antibiotics tested. All DEC formed biofilms and 92.6% adhered to HEp-2 cells with a prevalence of aggregative adhesion (74%). We identified 25 different serotypes. One EPEC isolate was serotype O44037:H7, reported for the first time in Brazil. Phylogenetically, 63% of the strains belonged to group B1. The analyzed waters were potential reservoirs for DEC and could act as a source for infection of humans. Preventive measures are needed to avoid such contamination.

Virulence Genes and Antimicrobial Resistance in Escherichia coli from Cheese Made from Unpasteurized Milk in Brazil

Cow raw milk cheese is widely eaten in Brazil. These products may be contaminated with pathogenic bacteria. In this work, we investigated the presence of Escherichia coli in raw milk cheese from different States in Brazil. From 147 "Minas" cheese samples, 28 cheeses were positive for E. coli. Among 39 E. coli isolates of the cheeses, one was positive for eae and negative for bpfA and efa1/lifA using PCR, and so was classified as atypical Enteropathogenic E. coli (aEPEC). Two other isolates were positive for extraintestinal pathogenic E. coli (ExPEC) genes. The aEPEC isolate belongs to serogroup O127 and was classified in A phylogenetic group, and ExPEC isolates were found in O73:H12 (EC-2 strain) and O64474:H8 (EC-9 strain) serotype. This ExPEC belongs to A and C phylogenetic group, respectively. Most of E. coli strains belonged to Clermont phylogenetic groups A (28.2%), C, and E (23.1%). Six strains (15.4%) of E. coli were positive for group B1 and two (5.1%) for B2. E. coli isolates presented an aggregative (46.0%) and diffuse (12.6%) adherence pattern to HeLa cells, and the other isolates did not show adhesion (41.4%). Four E. coli isolates (10.3%) were shown to produce moderate biofilm. The antimicrobial resistance rate was tetracycline (25.6%), followed by ampicillin (17.9%), cefoxitin (7.7%), nalidixic acid (5.1%), and amoxicillin-clavulanic acid (2.6%). One strain was resistant to three antimicrobials (tetracycline, ampicillin, and nalidixic acid). The presence of these microorganisms, the O127 strain, and a new serogroup in Brazil is a potential risk for public health.

Enteropathogens associated with acute diarrhea in children from households with high socioeconomic level in uruguay

Infectious diarrhea, a common disease of children, deserves permanent monitoring in all social groups. To know the etiology and clinical manifestations of acute diarrhea in children up to 5 years of age from high socioeconomic level households, we conducted a descriptive, microbiological, and clinical study. Stools from 59 children with acute community-acquired diarrhea were examined, and their parents were interviewed concerning symptoms and signs. Rotavirus, adenovirus, and norovirus were detected by commercially available qualitative immunochromatographic lateral flow rapid tests. Salmonella, Campylobacter, Yersinia, and Shigella were investigated by standard bacteriological methods and diarrheagenic E. coli by PCR assays. We identified a potential enteric pathogen in 30 children. The most frequent causes of diarrhea were enteropathogenic E. coli (EPEC), viruses, Campylobacter, Salmonella, and Shiga-toxin-producing E. coli (STEC). Only 2 patients showed mixed infections. Our data suggest that children with viral or Campylobacter diarrhea were taken to the hospital earlier than those infected with EPEC. One child infected with STEC O26 developed “complete” HUS. The microbiological results highlight the importance of zoonotic bacteria such as atypical EPEC, Campylobacter, STEC, and Salmonella as pathogens associated with acute diarrhea in these children. The findings also reinforce our previous communications about the regional importance of non-O157 STEC strains in severe infant food-borne diseases.

Molecular characterization of diarrheagenic Escherichia coli from Libya

Diarrheagenic Escherichia coli (DEC) are important enteric pathogens that cause a wide variety of gastrointestinal diseases, particularly in children. Escherichia coli isolates cultured from 243 diarrheal stool samples obtained from Libyan children and 50 water samples were screened by polymerase chain reaction (PCR) for genes characteristic of enteroaggregative E. coli (EAEC), enteropathogenic E. coli (EPEC), enterotoxigenic E. coli (ETEC), enterohemorrhagic E. coli (EHEC), and enteroinvasive E. coli (EIEC). The DEC were detected in 21 (8.6%) children with diarrhea; 10 (4.1%) cases were identified as EAEC, 3 (1.2%) as EPEC, and 8 (3.3%) were ETEC; EHEC, and EIEC were not detected. All DEC were grouped phylogenetically by PCR with the majority (> 70%) identified as phylogenetic groups A and B1. The EAEC isolates were also tested for eight genes associated with virulence using PCR. Multi-virulence (≥ 3 virulence factors) was found in 50% of EAEC isolates. Isolated EAEC possessed different virulence traits and belonged to different phylogenetic groups indicating their heterogeneity.