Oral vaccination of weaned rabbits against enteropathogenic Escherichia coli-like E. coli O103 infection: use of heterologous strains harboring lipopolysaccharide or adhesin of pathogenic strains.

To test the importance of lipopolysaccharide (LPS) and adhesin as major antigens in vaccination against rabbit enteropathogenic Escherichia coli (EPEC)-like E. coli O103 infection, we used two nonpathogenic wild-type strains to immunize rabbits at weaning. One of these strains (C127) harbors the O103 LPS but does not express the 32,000-molecular-weight adhesin that characterizes the highly pathogenic O103 strains. The other (C6) belongs to the O128 serogroup, which does not cross-react with the O103 serogroup, but expresses the adhesin. These strains were administered orally, either live or after Formalin inactivation. After vaccination, the animals were challenged with highly pathogenic O103 strain B10. Compared with rabbits vaccinated with the Formalin-killed homologous strain, rabbits vaccinated with killed C127 or C6 showed partial but significant protection. When given live, these strains colonized more or less heavily the digestive tract of the animals and provided nearly complete (C127) or complete (C6) protection against challenge. They induced a quick local immune response, as judged by fecal immunoglobulin A anti-LPS kinetics. Furthermore, strain C6 induced an ecological effect of "resistance to colonization" against challenge strain B10. This effect may have been due to the adhesin that is shared by both strains and to the production of a colicin. Strain C6 could inhibit in vitro the growth of highly pathogenic O103 strains. On the whole, our results show that adhesins and LPS are important, although probably not exclusive, protection-inducing components in rabbit EPEC-like colibacillosis and provide insight into possible protection of rabbits against EPEC-like E. coli infection with live strains.

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.

Protection of weaned rabbits against experimental Escherichia coli O103 intestinal infection by oral formalin-killed vaccine.

In an attempt to vaccinate young weaned rabbits against life-threatening enterocolitis caused by Escherichia coli of the O103 serogroup, 32 New Zealand male rabbits were divided into three groups. One group remained unvaccinated as a control (Group C), and each of the other groups received one of two types of vaccine prepared with E. coli strain O103/10 cultured either in trypticase-soy broth (Group A) or in Minca agar (Group B). Bacteria were killed by formalin and administered per os for 10 consecutive days after weaning at a daily dose of 4 X 10(9) organisms. Six days after the last administration, all the animals were challenged with 1 X 10(4) virulent E. coli O103/10 and the experimental infection was monitored for 26 days. All rabbits in Group A were protected from symptoms of disease and remained alive, whereas two rabbits in Group B developed clinical signs and one died. Protection did not correlate with local or general responses to lipopolysaccharide (LPS) O103, as judged by measurement of anti-LPS O103 IgA in faeces or serum, or by serum agglutinating antibodies. Numbers of E. coli and E. coli O103 were significantly lower in vaccinated animals of Group A as compared with animals of the control group. The differences between both vaccine regimens may be partially explained by a different expression of the adhesins of strain O103/10, depending on the medium used to prepare the vaccine.

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.

[Experimental study of diarrhea induced by a strain of Escherichia coli (serogroup O-103) in growing rabbits]. / Reproduction expérimentale chez le lapin en engraissement d'une diarrhée provoquée par une souche de Escherichia coli de sérogroupe O-103.

The experimental infection by mouth of weaned, 6 week old rabbits was performed with Escherichia coli strain O-103/10 without any adjuvant. The quantities of E. coli for the 3 experimental treatments were - none (control) - 10(4) or 10(7) per animal. The 142 rabbits were divided into 2 groups, each including the 3 treatments: A - observation of weight and eventual diarrhea during 25 days after infection; B - killing during the same period of some healthy and diarrheic animals every 2 or 3 days, for physiological, bacteriological, and histological observations. In the A group, mortality after 25 days was 0/24 in the control, 12 and 15/24 for 10(4) and 10(7) treatments respectively, but it was observed earlier for the 10(7) one. Diarrhea has been observed for 90% of infected and 20% of control rabbits, at first on day 7, 12 and 20 post-infection for the 10(7), 10(4) and control treatments respectively. The mean duration of diarrhea was 4 days in infected and only 2 in control rabbits. Always, diarrhea and weight lost were observed before death. Although the slowing down of growth rate during the experimental period, at the end, mean live weight was quite the same for animals surviving in the 3 treatments. Necropsy of killed rabbits of the B group, revealed hemorrhagic damages mainly on cecal and colonic wall, associated with high counts for E. coli (10(7) to 8 X 10(9] in the cecal content. In rabbits with highest counts (9/15), E. coli was also observed in blood. In diarrheic rabbits cecal pH was higher (6.61 vs 5.82) and cecal VFA concentration lower (53 vs 98 mM/l) than in healthy ones; but the proportions of acetic, propionic and butyric acids were not significantly affected. At constant VFA concentration in the cecum, pH and E. coli counts were correlated (r = + 0.35). Histology revealed first, attachment of bacteria to the apex of villi cells, and furthermore destruction of the epithelium with hemorrhages and necrosis. Thus the strain O-103/10 of E. coli is confirmed to be pathogenic and will provide a good experimental model for studies of diarrhea due to E. coli.

Incidence of experimental cirrhosis on hepatic disposition of [3H] levamisole in rats.

Levamisole [phenyl-2 3H] was injected intravenously (4.7 mg kg-1) into anaesthetized controls and rats in which cirrhosis had been induced by a combination of carbon tetrachloride and phenobarbitone. The biliary excretion (6 h) of the parent drug and its metabolites formed a significant part of the administered dose. Although bile flow did not vary, biliary excretion of levamisole and metabolites were respectively increased and decreased in cirrhotic compared with control animals. These differences could be the result of cirrhosis-induced decrease in the hepatic biotransformation of levamisole and also to limited active carrier transport for the output of metabolites into bile canaliculi.

[Effect of route and place of minocycline administration on the zootechnical performance of rabbits]. / Influence de la voie et du lieu d'administration de la minocycline sur les performances zootechniques du lapin.

Minocycline administered to rabbits per os or intramuscularly (30 mg/kg) over a period of three days led neither to digestive problems nor mortality. Administration per os left the growth curve unchanged. Intramuscular administration reduced rate of growth, and on the 15th day weight loss compared to controls was 3.2% or 11.7% depending on whether the place of administration was in the back muscles or in the thigh, and this despite a normal food intake. Minocycline did not modify microbial flora and level of ammonia in the caecum. Level of acetic acid was reduced by 50% on the fourth and 15th day after intramuscular administration of minocycline into the thigh. The depressive effect of minocycline on growth remains unexplained.

Enhancement of spiramycin concentration by bromhexin in the bovine nasal secretions.

Intramuscular injection of bromhexin (Quentan) results in increased bioavailability of spiramycin in nasal secretions. In the presence of a mucolytic agent, the area under the curve calculated according to spiramycin concentrations found in nasal secretions increases by 6%, 41% and 32% respectively in the course of three days of treatment. This potentiation reveals the interest involved in administering a combination of bromhexine and antibiotics in the treatment of infectious diseases of the respiratory tract.

[Sensibility of rabbits to treatment with ampicillin and gentamycin (author's transl)]. / Sur la sensibilité du lapin a l'association ampicilline-gentamicine.

Ampicillin administered to rabbits (20 mg/kg per day) over a period of three days subsequently provoked a death rate of 40%. No deaths were observed after treatment with gentamycin (10 mg/kg per day) or with a combination of ampicillin and gentamycin. On the fourth day weight loss in the three treated groups was 12%, 11% and 9%, respectively, compared to controls. At the same time food intake in the treated groups was only 15% to 20% of the amount consumed by controls. In the caecum, ampicillin treatment resulted in dominance of a strain of Enterobacter aerogenes. Gentamycin had no effect on bacterial flora, although in combination with ampicillin, the number of caecal bacteria (aerobic and anaerobic) was reduced. Flora modification might be responsible for accumulation of NH3 and an unbalance of free acids. Caecotrophy was inhibited by administration of ampicillin. When administered intramuscularly, ampicillin produced results comparable with those obtained orally, although gentamycin was ineffective.

Comparative bioavailability of levamisole in non lactating ewes and goats.

An original HPLC assay enabled the quantitation of levamisole in biological fluids of ewes (n = 4) and goats (n = 4). An open two compartment model showed the development of the drug in animals after oral (10 mg X kg -1) intramuscular (7.5), and subcutaneous (7.5) administrations by veterinary therapeutic forms. Greater efficiency was obtained in both species after intramuscular rather than subcutaneous or oral administrations. After intramuscular injection, levamisole levels in nasal secretion and saliva were five to 20 times higher than in plasma. Because of the high susceptibility of goats to levamisole, the subcutaneous route is preferred in this animal.

Effects of low doses of ochratoxin A after intratesticular injection in the rat.

The toxic effect of various doses of ochratoxin A on the rat testis was investigated after a single intratesticular injection. At time of sacrifice (day 10) degenerating changes occur in the testicular tissues: seminiferous tubules dilatation, cytolysis of the seminiferous epithelium, hyperplasia of the interstitial tissue, vascular thrombosis. The relations between the blood supply disturbances and the observed lesions are discussed.

[Behavioral alterations induced by post-natal exposure of the rat to lead]. / Altérations comportementales produites par l'exposition post-natale du Rat au plomb.

The behaviour of rats exposed to various levels of lead acetate (0.5 ; 1 ; 2 and 4% in dam's diet) before weaning was recorded between 2 and 6 months of age. Higher locomotor and exploratory activities as well as better scores in active avoidance conditioning were observed in the 4% lead-treated rats. For lower doses, no behavioural alterations were recorded despite both detarded growth and increased mortality.

[Toxins of Byssochlamys nivea Westling. I. Preliminary study of toxicity in sheep]. / Toxines de Byssochlamys nivea Westling. I - Etude préliminaire de la toxicité chez le mouton

The acute intoxication in 4 sheep, due to an extract from a Byssochlamys nivea culture containing patulin is attained by administering per os with a syringe or with an esophagal tube doses of patulin varying from 15 to 50 mg per kg of bodyweight. A dose of 20 mg/kg, given with a syringe, brought on the death of a sheep within 5 hours following the administration, while a dose of 50 mg/kg given by an esophagal tube, only led to some temporary and slight problems. Intoxication brings on such symptoms such as nasal discharge, the stoppage of ruminating, a painful sensitivity in the retro-sternal area, weight loss, and prolonged loss of appetite. With an autopsy, a sero-fibrinous peritoneal exsudate and considerable hemorrhaging in the abomasum can be found. Anatomo-pathological examinations pinpoint lesions in the liver and kidneys. Biochemical examinations revealed hemoconcentration followed by anemia, and a considerable drop in serum proteins. The urea level increases 24 hours after and attains a notable maximum at the 30th hour (50 to 200 per cent). During these acute intoxications, no disorder whatsoever in the nervous system was observed.