Biotypes of enteropathogenic Escherichia coli strains from rabbits

Acute renal injury from thrombotic microangiopathy associated with enteritis in New Zealand white rabbits

Over a 3-y period, 12 adult New Zealand white (NZW) rabbits were presented for postmortem examination following variably long periods of inappetence and soft-to-liquid stool production. Postmortem findings included serosanguineous fluid in abdominal and thoracic cavities, dark-red-to-white renal foci, reddened intestinal serosa, and pulmonary edema. Microscopically, mesangial changes and thrombi were observed in renal glomeruli, and mild-to-severe enteritis was observed. These findings resemble hemolytic uremic syndrome, which typically follows enterocolitis associated with Shiga toxin (Stx)-producing Escherichia coli infection. In our case series, various gram-negative bacteria, most commonly E. coli, were isolated from the intestinal tracts; however, Stx production was not demonstrated. Evidence of Encephalitozoon cuniculi infection, a common cause of renal disease in rabbits, was also not found. Our cases suggest that gram-negative enteric bacteria should be included in the differential diagnosis of renal disease in NZW rabbits, especially in cases with an accompanying clinical history of gastrointestinal disorder.

Sequence analysis of the Escherichia coli O15 antigen gene cluster and development of a PCR assay for rapid detection of intestinal and extraintestinal pathogenic E. coli O15 strains

A collection of 33 Escherichia coli serogroup O15 strains was studied with regard to O:H serotypes and virulence markers and for detection of the O-antigen-specific genes wzx and wzy. The strains were from nine different countries, originated from healthy or diseased humans and animals and from food, and were isolated between 1941 and 2003. On the basis of virulence markers and clinical data the strains could be split into different pathogroups, such as uropathogenic E. coli, enteropathogenic E. coli, Shiga toxin-producing E. coli, and enteroaggregative E. coli. H serotyping and genotyping of the flagellin (fliC) gene revealed 11 different H types and a close association between certain H types, virulence markers, and pathogroups was found. Nucleotide sequence analysis of the O-antigen gene cluster revealed putative genes for biosynthesis of O15 antigen. PCR assays were developed for sensitive and specific detection of the O15-antigen-specific genes wzx and wzy. The high pathotype diversity found in the collection of 33 O15 strains contrasted with the high level of similarity found in the genes specific to the O15 antigen. This might indicate that the O15 determinant has been spread by horizontal gene transfer to a number of genetically unrelated strains of E. coli.

Prevalence and characteristics of enteropathogenic Escherichia coli with the eae gene in diarrhoeic rabbits

A field study was carried out with the objective of investigating the prevalence of enteropathogenic Escherichia coli (EPEC) with the eae gene in diarrhoeic rabbits. EPEC eae+ were isolated from 60 (74%) of 81 diarrhoeic rabbits sampled in 30 industrial fattening farms localized in the four provinces of Galicia (northwestern Spain). Attaching and effacing lesions were found in 44 of 50 animals processed for histology. The 111 E. coli strains identified belonged to 19 different O serogroups and 13 biotypes. However, 53 (48%) of the strains belonged to serogroup O103 and 36 (32%) showed the serobiotype O103:B14. The eae gene was significantly more frequent (100%; 47 of 47) among the highly pathogenic rhamnose-negative strains of serobiotypes O103:B6 and O103:B14 than among the E. coli strains belonging to other serobiotypes (36%; 23 of 64) (P < 0.001). In this first report about the prevalence of EPEC with the eae gene in rabbits, we conclude that the class of E. coli strains observed is a common cause of diarrhoea in Galician rabbit farms, and that highly pathogenic rhamnose-negative strains of serotype O103:K-:H2 and biotype B14 are specially predominant.

O serogroups, biotypes, and eae genes in Escherichia coli strains isolated from diarrheic and healthy rabbits

A total of 305 Escherichia coli strains isolated from diarrheic and healthy rabbits in 10 industrial fattening farms from different areas of Spain were serotyped, biotyped, and tested for the presence of the eae gene and toxin production. The characteristics found in strains isolated from healthy rabbits were generally different from those observed in E. coli strains associated with disease. Thus, strains with the eae gene (74% versus 22%); strains belonging to serogroups O26, O49, O92, O103, and O128 (64% versus 12%); rhamnose-negative strains (51% versus 5%); and rhamnose-negative O103 strains with eae genes present (41% versus 1%) were significantly (P < 0.001 in all cases) more frequently detected in isolates from diarrheic animals than in those from healthy rabbits. Whereas a total of 35 serogroups and 17 biotypes were distinguished, the majority of the strains obtained from diarrheic rabbits belonged to only four serobiotypes, which in order of frequency were O103:B14 (72 strains), O103:B6 (16 strains), O26:B13 (12 strains), and O128:B30 (12 strains). These four serobiotypes accounted for 48% (112 of 231) and 5% (4 of 74) of the E. coli strains isolated from diarrheic and healthy rabbits, respectively. Only six strains were toxigenic (three CNF1+, two CNF2+, and one VT1+). We conclude that enteropathogenic E. coli strains that possess the eae gene are a common cause of diarrhea in Spanish rabbit farms and that the rhamnose-negative highly pathogenic strains of serotype O103:K-:H2 and biotype B14 are especially predominant. Detection of the eae gene is a useful method for the identification of enteropathogenic E. coli strains from rabbits. However, a combination of serogrouping and biotyping may be sufficient to accurately identify the highly pathogenic strains for rabbits.

Microbiological status of rabbit carcases in Egypt

A total of 40 New Zealand white rabbits, 20 freshly slaughtered rabbits from an experimental farm and 20 processed rabbit carcases from grocery stores in Beni-Suef city, were examined bacteriologically. The mean values of aerobic plate counts at 37 degrees C and 1 degrees C, Enterobacteriaceae counts, Pseudomonas counts and Staphylococcus counts of freshly slaughtered rabbits were 10(4) +/- 2 x 10(3), 8 x 10(2) +/- 10(2), 6 x 10(2) +/- 10(2), 3 x 10(2) +/- 10(2), and 10(2) +/- 60 organisms per gram respectively, whereas the equivalent values were 8 x 10(5) +/- 3 x 10(4), 2 x 10(5) +/- 10(4), 4 x 10(4) +/- 8 x 10(3), 2 x 10(4) +/- 6 x 10(3), and 4 x 10(3) +/- 4 x 10(2) organisms per gram of processed rabbit carcases from grocery stores, respectively. The freshly slaughtered rabbits showed a low bacterial load compared with processed rabbit carcases from grocery stores. Escherichia coli and Listeria monocytogenes could be isolated from the rabbit carcases examined in addition to Salmonella typhimurium, Pseudomonas aeruginosa and Staphylococcus aureus from processed rabbit carcases. Yersinia enterocolitica could not be isolated from any sample examined. Suggested measures to reduce the microbial load in rabbit carcases are discussed.

Evaluation of numerical typing systems for Escherichia coli using the API 50 CH and the PhP-EC systems as models

Reproducible and discriminating typing methods are required for epidemiological investigations. Numerical typing systems analyse patterns obtained in various ways by calculating similarity coefficients between isolates. In the present study, various measures of the efficiency of a numerical typing system are quantified. These include reproducibility, accuracy, and discrimination power. Three different numerical typing methods for Escherichia coli were compared using these measures: (a) Biotyping with API 50 CH system, (b) Biochemical fingerprinting with the API 50 CH system and (c) Biochemical fingerprinting with the PhP-EC system. Biotyping qualitatively measures the results of a set of biochemical reactions as + or -. Biochemical fingerprinting also uses biochemical reactions, but the tests are scored quantitatively by measuring the kinetics and intensity of each reaction. It was found that biotyping yielded poor reproducibility. When biochemical fingerprinting analysis was used with the API 50 CHE system the reproducibility and the discrimination was good. The PhP-EC system for biochemical fingerprinting showed equal reproducibility but was superior to the API 50 CH system with regard to discrimination power.

Escherichia coli populations from diabetic and non-diabetic patients with bacteraemia and faecal samples from healthy subjects--a comparative study

Biochemical reactions, using the PhP-EC system of biochemical fingerprinting, were evaluated in order to group strains into different clusters and to investigate whether a biochemical typing system may be used to distinguish between randomly selected Escherichia coli strains obtained from bacteraemic patients and healthy controls. Fifty epidemiologically unrelated strains isolated from blood of non-diabetic patients and 46 faecal control strains were studied. Separately, 70 E. coli strains from 64 diabetic patients with bacteraemia were investigated. Diversity index was 0.977, 0.969 and 0.941 respectively. The strains were clustered at a similarity level of 0.95. The bacteraemic and control strains were subdivided into 14 different clusters with 2-12 strains each and 40 'outliers'. The largest cluster was dominated by bacteraemic strains (9/12, 75%). Two other clusters were dominated by control strains. In the remaining groups blood and faecal isolates were evenly distributed. No biochemical test was able to distinguish between bacteraemic and faecal control strains. Strains from patients with diabetes mellitus were grouped in 11 clusters containing 2-14 strains and 22 'outliers'. The low diversity index of bacteraemic strains obtained from diabetic patients as compared to other strains indicated a greater homogenicity. However, no correlation was observed between the examined host factors and the clusters.

Adhesion of Escherichia coli strains isolated from diarrheic weaned rabbits to intestinal villi and HeLa cells

Thirty-eight strains, representative of 575 Escherichia coli isolates from weaned diarrheic rabbits, were tested for their ability to adhere in vitro to rabbit intestinal villi and to HeLa 229 cells. The O103 rhamnose-negative, highly pathogenic strains, which are epidemiologically predominant in France, attached to intestinal villi prepared from 8-day-old as well as 6-week-old rabbits and gave a diffuse adhesion pattern with HeLa cells. These adhesion properties were associated with the presence of a protein with a molecular weight of 32,000 in surface extracts of the strains. The expression of the adhesion was dependent on culture medium and temperature, and the adhesion was D-mannose resistant. Antisera raised against the 32,000-molecular-weight protein inhibited adhesion. This adhesion was not expressed in two nonpathogenic O103 strains, indicating its implication in virulence. However, the same adhesin was expressed by two O128 non- or moderately pathogenic strains. Therefore, adhesion to enterocytes is not the only factor involved in the pathogenicity of O103 strains.

Biotypes and O serogroups of Escherichia coli involved in intestinal infections of weaned rabbits: clues to diagnosis of pathogenic strains

A total of 575 Escherichia coli strains isolated from weaned rabbits experiencing diarrhea in 119 French commercial farms were tested for O serogroups. The results showed a strong predominance of serogroup O103 strains. A sample of 126 strains were further checked for simplified biotypes by using five carbohydrate fermentation reactions. Of 72 O103 strains, 70 were shown to belong to biotypes characterized by a rhamnose-negative reaction. Four of nine serogroup O68 strains also showed this type of reaction. Thirty-nine strains, representative of the serotypes and biotypes found, were further tested for experimental pathogenicity in weaned rabbits and for antibiotic susceptibility. All the rhamnose-negative strains produced life-threatening watery or hemorrhagic diarrhea, whereas rhamnose-positive strains induced only mild diarrheic syndrome without any mortality or no clinical signs at all. Rhamnose-negative, highly pathogenic strains did not belong to related antibiotypes. We think that O serogrouping together with biotyping, or even rhamnose fermentation testing, may be an important clue in the diagnosis of enteropathogenic strains from rabbits in France, permitting rapid identification of highly pathogenic strains and leading to improved prognosis and treatment.

Biotype, serotype, and pathogenicity of attaching and effacing enteropathogenic Escherichia coli strains isolated from diarrheic commercial rabbits

A total of 568 strains of Escherichia coli isolated from healthy and diarrheic rabbits were separated into 11 different biotypes according to the fermentation patterns of four carbohydrates. Strains belonging to biotypes 1 to 3, 6, and 8 induced lesions characteristic for attaching and effacing E. coli (AEEC). They attached to the intestinal epithelium of the terminal small intestine and the large intestine of 5-week-old rabbits after experimental infection and caused effacement of the microvillous brush border. However, pathogenicity for weaned rabbits, as judged by diarrhea score, anorexia, and reduced weight gain, varied according to the biotypes of the strains. Strains belonging to biotypes 1 and 6 produced only discrete clinical signs, strains belonging to biotypes 2 and 3+ (motile) induced diarrhea and growth depression, whereas strains belonging to biotypes 3- (immotile) and 8 caused severe clinical signs and high mortality. This confirms evidence from the field. Biotypes 3- and 8, accounting for 35.5 and 7.1% of AEEC strains in weaned diarrheic rabbits, respectively, were not detected in weaned healthy rabbits, while biotype 2 was the predominant strain in weaned healthy rabbits (62.3%). Finally, serotyping showed a close relationship between biotype and serotype of the AEEC examined. Most strains of biotypes 1+ and 2+ tested were O109:K-:H2 and O132:K-:H2, respectively, whereas all strains tested of biotype 3- were O15:K-:H- and those of biotype 8 were O103:K-:H2. These data indicate that specific clones of AEEC might be involved in juvenile rabbit enteritis. It was concluded that determination of biotypes allows the screening of highly pathogenic AEEC in weaned rabbits (biotypes 3- and 8).

Enteric infections caused by non-enterotoxigenic Escherichia coli in animals: occurrence and pathogenicity mechanisms. A review

Not all E. coli that cause diarrhoea in farm animals act by elaborating the classical heat-labile or heat-stable enterotoxins. These newly recognised animal enteropathogenic E. coli (EPEC) attach to and efface the microvilli of the gut epithelium and resemble the well known human EPEC. In rabbits, only this type of E. coli enteritis is known to be important and a similar disease has been shown to occur in cattle also. There is no doubt that adherence factors are important in the pathogenesis of animal EPEC, but they are not well understood when compared with the adhesion of human EPEC, or to the adhesion of animal ETEC. The enteropathogenic effect is probably due to Shiga-like toxin, a cytotoxin that is active on Vero cells and has also been called Verotoxin. A different type of Verotoxin is produced by most serotypes that are associated with post-weaning diarrhoea and oedema disease in pigs. This toxin is suspected to play a role in the pathogenesis of the latter.