Phenotypic characteristics, virulence profile and genetic relatedness of O157 Shiga toxin-producing Escherichia coli isolated in Brazil and other Latin American countries

Shiga toxin-producing Escherichia coli (STEC) in bovine meat and meat products over the last 15 years in Brazil: A systematic review and meta-analysis

We conducted a systematic review and meta-analysis to determine the rate of contamination in bovine meat and meat products with Shiga toxin-producing Escherichia coli (STEC) in Brazil over the last fifteen years. Data were obtained from online databases in February 2020, and 25 papers were selected from 1036 articles identified in the literature search and 13 articles from gray literature, totaling 4286 samples analyzed. The overall rate of STEC was estimated to be 1% in Brazil. The highest rate (9%) was observed in Mato Grosso, followed by Rio Grande do Sul (1%), Goiás (1%), and São Paulo (1%). Regarding the sample type analyzed, hot carcasses had the highest rate (8%) of positive samples for STEC, followed by cold carcasses (2%) and beef samples (1%). As the available data were concentrated in the São Paulo state, the findings of this meta-analysis reveal the need for further studies in Brazil to allow better risk assessment and prevention of human STEC infections.

Shiga toxin-producing Escherichia coli in the animal reservoir and food in Brazil

Shiga toxin-producing Escherichia coli (STEC) is a zoonotic pathotype associated with human gastrointestinal disease that may progress to severe complications. Ruminants, especially cattle, are the main reservoirs of STEC contaminating the environment and foods of animal or vegetable origin. Besides Shiga toxin, other virulence factors are involved in STEC virulence. O157:H7 remains the most frequent serotype associated with disease. In Brazil, the prevalence of STEC reaches values as high as 90% in cattle and 20% in meat products which may impact the Brazilian food export trade. However, only few reports are related to human disease. The stx1 gene prevails in cattle, whereas the stx2 gene is more frequent in food. Several STEC serotypes have been isolated from cattle and food in Brazil, including the O157:H7, O111:NT, NT:H19 as well as O26 and O103 serogroups. O113: H21 STEC strains are frequent in ruminants and foods but with no report in human disease. The virulence profile of Brazilian STEC strains from cattle and food suggests a pathogenic potential to humans, although some differences with clinical strains have been detected. Further studies, employing recent and more discriminative techniques are in need to better clarify their virulence potential.

Comment on "Shiga-Toxin Producing Escherichia coli in Brazil: A Systematic Review. Microorganisms 2019, 7, 137"

A recent article by Castro et al. describes a systematic review of Shiga-toxin producingEscherichia coli (STEC) in Brazil. [...].

Molecular analysis of Shiga toxin-producing Escherichia coli O157:H7 and non-O157 strains isolated from calves

Shiga toxin-producing Escherichia coli (STEC) O157 and non-O157 are food-borne pathogens and contaminants of foods of animal origin. This study was conducted to investigate the presence of virulence and integrase genes in STEC isolates from diarrhoeic calves in Fars Province, Iran. Five hundred and forty diarrheic neonatal calves were randomly selected for sampling. Rectal swabs were collected and cultured for isolation and identification of E. coli following standard methods. The isolates were analysed for the presence of class 1 integrons and bacterial virulence factors using polymerase chain reaction (PCR). Antimicrobial susceptibility testing was performed using the Kirby-Bauer disc diffusion method. Out of 540 diarrhoeic faecal samples, 312 (57.7%) harboured E. coli and 71 (22.7%) of them were identified as STEC: 41(69.5%) carried the stx2 gene, 21 (35.6%) carried the stx1 gene and 3 (5%) carried both. Twenty-six (44%) of the isolates showed the eaegene. Among the STEC isolates examined for susceptibility to eight antimicrobial agents, erythromycin and penicillin (96.8%) resistance were most commonly observed, followed by resistances to ampicillin (71.8%), tetracycline (62.5%) and trimethoprim/sulfamethoxazole (39%). Integrons were detected by PCR in 36% of the STEC tested isolates, 57 (89%) of which showed resistance to at least three antimicrobial agents. Our findings should raise awareness about antibiotic resistance in diarrhoeic calves in Fars Province, Iran. Class 1 integrons facilitate the emergence and dissemination of multidrug-resistance (MDR) among STEC strains recovered from food animals.

Genetic characteristics of Shiga toxin-producing E. coli O157, O26, O103, O111 and O145 isolates from humans, food, and cattle in Belgium

In this study, we characterized 272 Shiga toxin-producing Escherichia coli (STEC) isolates from humans, food, and cattle in Belgium [O157 (n = 205), O26 (n = 31), O103 (n = 15), O111 (n = 10), O145 (n = 11)] for their virulence profile, whole genome variations and relationships on different genetic levels. Isolates of O157 displayed a wide variation of stx genotypes, heterogeneously distributed among pulsogroups (80% similarity), but with a concordance at the pulsosubgroup level (90% similarity). Of all serogroups evaluated, the presence of eae was conserved, whereas genes encoded on the large plasmid (ehx, espP, katP) occurred in variable combinations in O26, O103, and O145. The odds of having haemolytic uraemic syndrome was less for all genotypes stx2a, stx2c, stx1/stx2c, and stx1 compared to genotype stx2a/stx2c; and for patients aged >5 years compared to patients aged ≤ 5 years. Based on the genetic typing and by using epidemiological data, we could confirm outbreak isolates and suggest epidemiological relationships between some sporadic cases. Undistinguishable pulsotypes or clones with minor genotypic variations were found in humans, food, and cattle in different years, which demonstrated the important role of cattle as a reservoir of STEC O157, and the circulation and persistence of pathogenic clones.

Shiga toxin-producing Escherichia coli in Peruvian children with bloody diarrhea

Shiga toxin-producing Escherichia coli (STEC) is not routinely sought in clinical laboratories in developing counties. Among 131 bloody diarrhea samples in Peruvian children <5 years of age, STEC was found in 9.2% and was associated with absence of fever, an observation that may increase suspicion of these pathogens. Because of the significant prevalence of STEC locally, proper diagnostics methods should be implemented in the region.

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.

Virulence factors, antimicrobial resistance, and plasmid content of Escherichia coli isolated in swine commercial farms

Virulence factors and antimicrobial resistance patterns of Escherichia coli isolates were evaluated. A total of 80 E. coli isolates were evaluated, being 64 from clinical samples (intestinal content and fragments of organs from diarrheic piglets), seven from feces of clinically healthy piglets and sows, and nine environmental samples (five from facilities, two from feed, one from insect, and one from waste). Molecular characterization was performed by PCR detection of fimbriae and toxin genes and plasmid content determination. The isolates were also characterized according to their resistance or sensitivity to the following drugs: ampicillin, trimethoprim:sulfamethoxazole, tetracycline, amikacine, colistin, norfloxacin, florfenicol, enrofloxacin, cefalexin, trimethoprim, neomycin, chloramphenicol, and gentamicin. From 80 E. coli isolates, 53.8% were classified as enterotoxigenic E. coli (ETEC), 2.5% were shiga toxin-producing E. coli (STEC), and 43.8% showed a non specific pattern and were unclassified. One fecal isolate from non-diarrheic piglet was classified as ETEC by PCR. Clinical isolates showed resistance mainly for tetracycline and trimethoprim:sulfamethoxazole. Plasmidial DNA was observed in 70 isolates, being 78.5% of clinical isolates, 8.57% of non-diarrheic feces, and 12.8% of environment.

Acquisition of serum antibodies reactive with enterohemorrhagic Escherichia coli virulence-associated factors by healthy Brazilian children and adults

BACKGROUND

Patients with hemorrhagic colitis or hemolytic uremic syndrome due to enterohemorrhagic Escherichia coli (EHEC) develop serum IgM and IgG response to lipopolysaccharide (LPS) and to virulence factors such as intimin. The small numbers of cases of diarrhea associated with EHEC strains in Brazil suggests a pre-existing immunity probably due to previous contact with diarrheagenic E. coli. Our aim was to evaluate the development of the serum antibody repertoire to EHEC virulence factors in Brazilian children and adults.

METHODS

Serum IgM and IgG antibodies were determined by enzyme-linked immunosorbent assay with LPS O111, LPS O26, and LPS O157 in 101 children between 2 months and 10 years of age and in 100 adult sera, by immunoblotting with protein membrane extracts and purified beta intimin; the ability of adult sera to neutralize Shiga toxin2 was also investigated.

RESULTS

Children older than 24 months had IgM concentrations reactive with the 3 LPS equivalent to those seen in the adult group, and significantly higher than the group of younger children (P < 0.05). Anti-O26 and anti-O157 LPS IgG concentrations were equivalent between the 2 groups of children and were significantly different from the adult group (P < 0.05). The anti-O111 LPS IgG levels in older children were intermediate between the younger group, and adults (P < 0.05). Immunoblotting revealed strong protein reactivity, including the conserved and variable regions of beta intimin and more than 50% of the adult samples neutralized Shiga toxin 2.

CONCLUSIONS

Our results demonstrate an increasing anti-LPS and antiprotein antibody response with age, which could provide protection against EHEC infections.

Intimin subtyping ofEscherichia coli: concomitant carriage of multiple intimin subtypes from forage-fed cattle and sheep

The outer membrane protein, intimin (eae), which mediates bacterial attachment to epithelial cells, is associated with enteropathogenic Escherichia coli and some Shiga toxin-producing E. coli. The eae subtype of E. coli strains isolated from healthy cattle and sheep was identified using a rapid PCR-restriction fragment length polymorphism (RFLP) method to produce profiles that were compared with those generated in silico. The 139 eae-positive E. coli strains were separated into 11 different PCR-RFLP profiles. The most common eae PCR-RFLP type was beta (23.7%), followed by zeta (20.1%), theta (16.5%), iota (12.2%), kappa (8.6%), epsilon (7.2%), gamma (2.9%), nu and beta2 (2.2%) and iota2 (1.4%). Four isolates did not yield a PCR-RFLP amplification product but complete sequencing of the eae gene matched subtype rho. Two different eae variants were isolated from the same swab from 18 different animals and subtype iota was the most 'promiscuous', being isolated with four other eae subtypes from seven separate animals. None of the eae-positive STEC were subtype gamma, which is associated with STEC serogroup O157. This method allowed the rapid identification of eae subtypes and indicates that forage-fed animals possessed a wide diversity of bacterial eae subtypes with a low frequency of eae subtype gamma.

Distinct pathotypes of O113 Escherichia coli strains isolated from humans and animals in Brazil

Two distinct diarrheagenic Escherichia coli pathotypes, enteroaggregative E. coli (EAEC) and Shiga toxin-producing E. coli, were observed in association with O113 strains isolated from human and nonhuman sources in Brazil, respectively. The O113 strains from human diarrhea belonged to a diversity of serotypes, and nine (53%) of them harbored virulence traits of typical EAEC.