Studies on E. coli-enteropathy in weanling rabbits

Pigs experimentally infected with Serpulina hyodysenteriae can be protected from developing swine dysentery by feeding them a highly digestible diet

Weaner pigs (n = 72) were fed 1 of 4 diets. These were based on either cooked rice and animal protein, cooked rice and lupin, wheat and lupin, or wheat and animal protein. Twenty-six of the pigs were slaughtered after 1 month. Those fed the highly digestible cooked rice and animal protein diet had drier colonic contents and faeces, lighter large intestines, and the contents of their large intestines had increased pH values and decreased total VFA concentrations. The other 46 were orally challenged with broth cultures of Serpulina hyodysenteriae, and were monitored for faecal excretion of the spirochaetes, and for the development of swine dysentery (SD). None of 18 pigs fed the cooked rice and animal protein diet developed colonic changes or disease, whereas most pigs on the other diets developed mucohaemorrhagic colitis and dysentery. The reduced fermentation that occurred in the large intestines of pigs fed cooked rice and animal protein was associated with a subsequent failure of colonization by S. hyodysenteriae, and resultant protection against SD.

Serotypes, toxins and antibiotic resistance of Escherichia coli strains isolated from diarrhoeic and healthy rabbits in Spain

One hundred and ten Escherichia coli strains isolated from diarrhoeic and healthy rabbits from 50 Spanish commercial farms were serotyped and investigated for production of enterotoxins (LT and STa), verotoxins (VT), cytotoxic necrotizing factors (CNF1 and CNF2), alpha-haemolysin (Hly) and enterohaemolysin (EntHly), for necrotic and lethal activities and for antibiotic resistance. Six serogroups (O2, O26, O49, O92, O103 and O128) accounted for 81% (67 of 83) and 26% (7 of 27) respectively of E. coli strains isolated from diarrhoeic and healthy rabbits (P < 0.001). The most common serotypes found among E. coli strains associated with diarrhoeic rabbits in order of frequency were: O103:K-:H2, O49:K?:H2, O26:K-:H-, O26:K-:H11, O128:K?:H-, O92:K-:H2 and O2:K5:H6. E. coli strains belonging to the same serotype but from different farms usually showed a distint antibiotics resistance pattern. Only one strain, of serotype O2:K5:H6 was toxigenic (CNF1+, Hly+, necrotic and lethal).

The role of intestinal volatile fatty acids in the Salmonella shedding of pigs

Factors affecting colonization of the intestinal tract by salmonellas were studied in two pig herds. In herd H 18% of the faecal samples taken from live pigs and 30% of the colon content samples collected at slaughter contained salmonellas. In contrast, the 50 faecal samples taken from pigs of herd L were negative and only 2% of the colon contents collected at the yielded salmonellas. An antibacterial effect inhibiting salmonella multiplication was demonstrable in vitro in colon contents from pigs of herd L. No such effect was found to exist in samples taken from pigs of herd H. The antibacterial effect is due to the non-dissociated volatile fatty acid (VFA) molecules present in the colon content. As the degree of VFA dissociation depends on the pH of the environment, at lower pH values (pH 6.1 +/- 0.2) of the colon contents from herd L the ratio of non-dissociated VFA molecules is higher and the resulting antibacterial effect is stronger than in samples from herd H (pH 7.1 +/- 0.3).

Experimental Escherichia coli enteropathy in weanling rabbits: clinical manifestations and pathological findings

Diarrhoea was reproduced by inoculating 5-week-old New Zealand White rabbits orally with 2 X 10(6) CFU of E. coli 0.15:H-. The strain produced diarrhoea in all the dosed rabbits 6.25 +/- 2.71 (mean +/- S.D.) days after infection (p.i.). Mortality was high. Sequential examination of the intestines by light microscopy showed the strain to attach first to the tips of the lymphoid follicle epithelium of Peyer's patches 24 h p.i., but not to other sites until 3 days p.i. From 3 to 14 days p.i. the strain caused an acute intestinal inflammatory response and large numbers of E. coli adhered to the enterocytes of ileum, caecum and colon. Colonized cells became rounded and were desquamated. Severe oedema of the caecal lamina propria was often present. Colonization of the intestine, as shown by rectal swab cultures, reached a maximum 4 to 7 days p.i. and did not decrease until 14 days p.i.

Pathogenic properties of Escherichia coli strains isolated from diarrheic commercial rabbits

Thirty-two different strains of Escherichia coli isolated from diarrheic commercial rabbits showing intestinal attachment of bacilli were studied. None of the strains produced thermostable or thermolabile enterotoxins, and none was invasive. Strains isolated from suckling rabbits attached in vitro to the brush borders of intestinal villi, whereas strains from weanling rabbits did not. After experimental infection of 5-week-old rabbits, the 26 strains isolated from weaned diarrheic rabbits attached to the epithelium of ileum, cecum, and colon, whereas only slight attachment was found after infection with the six strains isolated from suckling diarrheic rabbits. The former strains induced diarrhea in 87% of the rabbits, whereas the latter induced diarrhea in only 9% of inoculated rabbits. E. coli isolated from healthy rabbits did not cause diarrhea. Strains isolated from diarrheic suckling rabbits all belonged to serotype O109:K-:H2, whereas strains from diarrheic weaned rabbits belonged to at least eight different serogroups. It is suggested that two different mechanisms of E. coli enteropathy might exist in rabbits.