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D Licois

Publications and source records attributed to D Licois.

35 records · Page 2Linked to original sources
PubMed1992

Characteristics and diffusion in the rabbit of a phage for Escherichia coli 0103. Attempts to use this phage for therapy.

A bacteriophage for Escherichia coli 0103 was isolated during a study on E. coli diarrhoea in intensive breeding units of rabbits. The phage had an isometric head and a short tail and resembled coliphage N4 (Podoviridae). It had a very narrow host range and seemed to be specific for serogroup 0103, suggesting that it might be used for preliminary identification of E. coli strains of this serogroup instead of the usual slide agglutination. In view of its possible use as a therapeutic phage, we investigated its dissemination in rabbit organs after oral administration. The phage persisted in the spleen for at least 12 days. However, in vivo studies showed that this phage and a mixture of more virulent phages for E. coli 0103 were ineffective in preventing disease in rabbits inoculated with an enteropathogenic strain of E. coli 0103.

Animals↗
PubMed1992

Susceptibility of the rabbit to an enteropathogenic strain of Escherichia coli 0103: effect of animals' age.

Experimental infections with an enteropathogenic strain of Escherichia coli 0103 were studied in SPF rabbits of different ages. Whatever the age, the weight gains in all animals were reduced more or less significantly. However, mortality differed considerably according to the age. Four to 5-week-old rabbits were most susceptible to the infection, with 80-100% mortality associated with diarrhoea, generally of the hemorrhagic type. Peak mortality was observed between 5-10 days post-inoculation. In general, 21-day-old rabbits died from the second week post-inoculation onwards. After the 6th week of age, mortality was rare. Study of the microflora showed that the colonization of the gut by E coli 0103 occurred whatever the age as 10(6)-10(9) bacteria per g of feces of the inoculated strain were recovered. The role of specific receptors has been discussed.

Aging↗
PubMed1992

Endogenous development of Eimeria intestinalis in rabbits (Oryctolagus cuniculus).

The endogenous life cycle of a pure strain of Eimeria intestinalis was studied by light and electron microscopy in coccidia-free rabbits. Four schizont generations could be observed: the first one, not previously described, was seen between 36 and 144 hr postinoculation (PI), the second one between 64 and 168 hr PI, the third one between 96 and 192 hr PI, and the fourth one between 168 and 240 hr PI. Gamogony apparently started as early as 144 hr PI. Thus, it was possible for oocysts to develop from third generation merozoites, later oocysts developing after the fourth schizont generation. Electron microscopic observation suggested that oocysts were derived mainly from merozoites of the fourth schizont generation. During the first stage of the life cycle, sporozoites were seen in intraepithelial lymphocytes. All asexual generations, except the fourth, were characterized by 2 schizont types: the first, regarded as female, contained mononuclear merozoites and the second, regarded as male, contained polynuclear merozoites.

Animals↗
PubMed1992

[Enteropathogenic Escherichia coli from the rabbit].

Intestinal pathology is the main cause of morbidity and mortality in breeding colonies of commercial rabbits. Among pathogens, some strains of Escherichia coli are widely involved in enteric infections. In France, pathogenic E coli belonging to the 0103 serogroup has been isolated in 30-40% of weanling rabbits with diarrhea. Given these conditions, it was of interest to review the different groups of diarrheogenic E coli and their plasmid-encoded virulence properties, especially adhesion and secretion of enterotoxins or cytotoxins. We attempted to investigate the E coli responsible for diarrhea in the rabbit, particularly those belonging to the 015 and 0103 serogroups. Like E coli 015, the pathogenic strains of the 0103 serogroup adhere to intestinal cells and induce effacement of microvilli with pedestal formation. Thus, these strains which are also non-invasive and do not synthetize classical LT or ST enterotoxins, could be considered as enteropathogenic E coli (EPEC) or enterohemorrhagic E coli (EHEC). In fact, E coli 0103 is often associated with severe hemorrhagic diarrhea. Enteropathogenic E coli 0103 could therefore be a good model for studying intestinal pathology due to EPEC or EHEC in the young rabbit or in other animals and man.

Animals↗
PubMed1991

Scanning and transmission electron microscopic study of adherence of Escherichia coli O103 enteropathogenic and/or enterohemorrhagic strain GV in enteric infection in rabbits.

The GV strain (serotype O103:H2:K-), originally isolated from a diarrheic rabbit, is an enteropathogenic Escherichia coli strain that produces diarrhea without synthesizing the classical enterotoxins and that is not invasive. This strain is characterized by a 117-kb plasmid (pREC-1). Histological study of the gut by scanning electron microscopy and transmission electron microscopy was performed on the GV strain, on a derivative strain cured of pREC-1, and on transconjugants obtained by transfer of pREC-1 to nonpathogenic strains E. coli K-12 and 6100, not belonging to the O103 serogroup. The GV strain adhered to the epithelial cells of the ileum and large intestine, whereas the cured GV strain did not. Transfer of plasmid pREC-1 to E. coli K-12 or 6100 allowed the bacteria to attach to the intestinal mucosa in the same manner as that of the wild-type GV strain. Thus, pREC-1 seems to play an important role in attachment to and colonization of the intestinal tract of rabbits by E. coli serogroup O103. Scanning electron microscopy showed numerous bacteria attached together and closely associated with intestinal villi. Transmission electron microscopy revealed effacing lesions characteristic of enteropathogenic E. coli strains: effacing of microvilli and cuplike projections (pedestal formations) associated with an acute inflammatory and hemorrhagic response. In contrast with the results reported for rabbit pathogenic O15 strains, it appeared that the Peyer's patches were not involved in the early stages of infection with the O103 GV strain. This strain may represent a model for the study of the virulence and pathogenic effects of enteropathogenic and enterohemorrhagic E. coli strains.

Animals↗
PubMed1991

R plasmid in Escherichia coli O103 coding for colonization of the rabbit intestinal tract.

One rabbit pathogenic Escherichia coli strain, belonging to serogroup O103, harbors a self-transferable 117-kb plasmid (pREC-1) encoding resistance to several antibiotics. The role of this R plasmid in the colonization of the digestive tract in specific-pathogen-free (E. coli O103-free) rabbits was studied. Five-week-old rabbits were inoculated with the wild-type strain, with its variant cured of the plasmid, with an E. coli K-12 strain, or with an untypeable E. coli strain from a healthy rabbit. No symptoms and no mortality were observed in animals inoculated with strains without the plasmid pREC-1, but 87.5% of the rabbits infected by the wild strain died, generally with bloody diarrhea, between days 5 and 15 postinfection. The weight gain of animals was strongly reduced. Transfer of the plasmid to the cured strain or to nonvirulent strains led these strains to induce the same pathology but with a lower mortality. Colonization of the gut by the O103 strain and symptoms of bloody diarrhea are thus related to the presence of the pREC-1 plasmid. The GV strain, which does not produce classical heat-labile enterotoxin or heat-stable enterotoxin and is not invasive, could be considered an enteropathogenic E. coli-like strain. The presence of a conjugative plasmid such as pREC-1 encoding both antibiotic resistance and virulence determinants in O103 E. coli from rabbits could represent a prominent epidemiological hazard under selective pressure by antibiotic therapy.

Animals↗
PubMed1990

Selection and characterization of a precocious line of Eimeria intestinalis, an intestinal rabbit coccidium.

A precocious line of Eimeria intestinalis was obtained by selection for early development of oocysts in rabbits and after six consecutive passages in animals. This line (EiP) was derived from a wild strain (EiO) isolated in 1975 from the caecal content of a rabbit with coccidiosis. The prepatent period of the EiP strain was reduced from 215 h to less than 144 h, the result being that the oocyst sporulation time was the same for both lines. The excreted and unsporulated oocysts had exactly the same shape, but microscopical examination of the sporulated oocysts showed a marked difference between EiP and EiO strains. A huge refractile globule was located in each of two sporocysts of the precocious line, whereas no refractile globule was seen in the other two. The EiP line had a reproductive potential much lower (1000 times) than that of its parent strain EiO and, as judged by the weight gain, mortality and lesions that also occurred in the jejunum and above all in the ileum, its pathogenicity was substantially reduced.

Animals↗
PubMed1986

[Tyzzer's disease].

Tyzzer's disease occurs as an epizootic disease in a number of mammals including rabbits and is characterized by sever diarrhoea and high mortality. Lesions consist of necrotic and hemorrhagic enteritis and are observed mainly in the distal digestive tract (ileum-caecum-colon). Congestion and vivid reddening of the caecum and marked serosal and submucosal oedema are present. Typical hepatic lesions, i.e. necrotic and miliary foci of the liver are generally absent in acute phase of the disease in rabbits. The diagnosis of Tyzzer's disease is difficult to establish and is based on the histologic demonstration of the causative agent Bacillus piliformis within the cytoplasm and nucleus of viable cells around necrotic area of the liver or intestine. Cultivation of this pleomorphic organism in cell-free media has been unsuccessful. Hence, taxonomic position of B. piliformis remains questionable. It is possible that Tyzzer's agent is an anaerobic, Extremely Oxygen Sensitive (EOS) bacteria closely similar to Fusobacterium. Failure to cultivate B. piliformis in vitro makes its study difficult and the role of this organism in the outbreaks of diarrhoea remains unclear. We believe that like in "swine dysentery", strong modifications of the intestinal flora facilitated by disorders of some factors particular to the animal--such the impairment of the mechanisms of immunity--or the perturbations of the environmental conditions are important even in the genesis of Tyzzer's disease and that the difficulty of diagnosis probably minimize the incidence of this organism in breeding.

Animals↗
PubMed1982

Intestinal motor and transit disturbances associated with experimental coccidiosis (Eimeria magna) in the rabbit.

Digestive motility has been analyzed in three rabbits chronically fitted with intraparietal electrodes, during 6 days before and 18 days after infection with 100,000 oocysts of E. magna. The rate of flow and the transit time of digesta in the small intestine were determined during the same period by marker dilution techniques in three other rabbits fitted with an intraluminal catheter and a cannula at respectively 1.2 and 0.4 m from the ileo-caecal valve. The main disturbances of small intestine motility consisted in a disorganization of the motor profile from the 4-5th day after infection and in a strong inhibition on the 8-9th days. Gastric motility was inhibited from the 4th to the 8th day while the frequency of caecal contractions increased on the 8-9th days. An increase of the rate of flow of digesta appeared on the 8-9th days with a concomitant increase of the transit time in two rabbits and a decrease of transit time in the third rabbit. Intestinal hypomotility and the increase of digesta flow seemed to be the two primary disturbances, the consequences of which were the changes in the gastric and caecal motility and in the transit time of digesta.

Animals↗
PubMed1980

[Attempt to induce diarrhea in young rabbits with different dietary crude fiber contents (author's transl)].

The influence of five diets containing 14.5, 10, 6.9, 4.6 and 3.3 per cent of crude fiber was studied in 6-week-old rabbits. Two additional groups of animals fed with the rations with 14.5, 6.9 and 3.3 per cent crude fiber were used. The first was inoculated with coccidia, the second was treated with ampicillin. In non-inoculated and untreated rabbits, diarrhea was inconstant, of short duration and low intensity and appeared only for cellulosis rate less than 4.6 per cent. There was no mortality. Decrease in the dietary crude fiber level cannot be considered as directly responsible for digestive ailments, when sanitary conditions are good. In our experimental conditions, it has been shown that a low level of cellulosis in the diet did not increase the pathological phenomena. Inversely pathogenic elements (coccidia) or medicaments used (ampicillin) can change the relations which exist between growth and components of the diet (cellulosis).

Animals↗
PubMed1980

[An hypothesis of the pathogenesis of diarrhoea in the rabbit based on a study of intestinal contents].

Experimental diarrhoea was induced in young rabbits by inoculation with Eimeria intestinalis and E. flavescens. The mineral composition of the intestinal contents was studied and compared to those of control animals. In the jejunum, ileum, caecum, proximal and distal colon, the sum (Na+ + K+) was linearly related to the water content of those segments. The regression lines were the same for all the animals, but the means were different, indicating that the defect in water absorption was due to a lack of sodium reabsorption at the site of coccidia implantation. In the colon, sodium was reabsorbed against potassium secretion. This exchange diffusion mechanism explains the excessive loss of potassium in rabbit diarrhoea as well as the marked hypokalemia.

Animals↗
PubMed1979

Characterization of Eimeria species. I. Isolation and study of pathogenicity of a pure strain of Eimeria perforans (Leuckart, 1879; Sluiter and Swellengrebel, 1912).

Eimeria perforans was isolated in pure strain by utilizing specific biological characters and specific-pathogen free rabbits. The purity of this strain was demonstrated by measurements of oocysts, derived from a line, started by infection from a single oocyst. The parasite, when inoculated in large numbers, causes a mild disease response for only about two days.

Animals↗
PubMed1978

Changes in hydromineral metabolism in diarrhoeic rabbits. 2. Study of the modifications of electrolyte metabolism.

The study of the equilibrium of the main electrolytes (Na+, K+, Cl-), in plasma and intestinal content and the evolution of the partial plasma (Na+, K+, Cl-) in the young rabbit suffering from diarrhoea revealed disturbances of the mineral metabolism. Mineral losses were lower in sick animals than in controls. When the reduction of ingested matter was taken into account, the ion balance showed a deficit. The apparent coefficient of digestive utlization (aCDU) of the electrolytes Na+ and K+ dropped, although the reabsorption of these ions in the last segments of the digestive tract was generally good. The pH remained normal and the proteinaemia fell, suggesting a haemodilution. This was backed up by the presence of a hyponatraemia and a hypochloraemia, but did not account for the large drop in kaliemia. On the other hand, the plasma osmotic pressure increased, very probably in association with a high uraemia. It would therefore seem that the pathogenesis of diarrhoea in the young rabbit differed from that of other known examples, such as diarrhoea in the calf and in the infant. In the young rabbit, the pathogenesis of diarrhoea resulting from coccidiosis would seem to be, as much a result of a nutritional deficiency in particular of potassium, as of a malfunctioning of the digestive tract.

Animals↗
PubMed1976

A comparison of the osmotic pressures along the digestive tract of the domestic fowl and the rabbit.

1. The osmotic pressures of the contents of the alimentary tract from the adult hen and cockerel and rabbit were measured. 2. In the rabbit osmolality of the fluids from the different segments of the digestive tract was similar (331 &/- 12 mOm) and slightly hypertonic to blood plasma (297 &/- 3-12 mOsm). 3. In the hen osmotic pressures were: crop 537, gizzard 312, duodenum 571, proximal jejunum 650, distal jejunum 573, proximal ileum 514 and distal ileum 451 mOsm. Only osmolality of the crop contents was influenced by egg formation. 4. In the cockerel osmotic pressure in the alimentary tract followed the same pattern as the hen and was modified by the time of day. 5. Plasma osmolality in the fowl was about 320 mOsm. Absorption of water across the proximal jejunum is achieved therefore against a gradient of about 330 mOsm in the female and 420 mOsm in the male fowl.

Animals↗
PubMedDate not supplied

Caecal microflora and fermentation pattern in exclusively milk-fed young rabbits.

Thirty-two SPF New Zealand White rabbits of both sexes were used in this experiment. They were sequentially slaughtered at 22, 29, 35 and 42 days of age. The rabbits were only milked by their mother and by foster mothers (no access to solid food) throughout the experiment. They exhibited a caecal fermentation pattern that turned towards a proteolytic metabolic activity (high levels in NH3 and in branched-chain fatty acids and valeric acid: 17 mmol.L-1 and 1 mmol.L-1, on average, respectively). The absence of caecal cellulolytic microflora and the low concentration of the total volatile fatty acids (tVFA) could be explained by the lack of substrate that would have been brought by a solid feed. From day 29 onwards, the low tVFA (12.5 mmol.L-1) and high NH3 concentrations (16.5 mmol.L-1) explained the high pH value (6.8 on average). This could be considered as a pathological value in weaned rabbits, but in our case no clinical signs of diarrhoea were observed. The evolution of the colibacilli flora according to age was similar to that usually described and thus was not correlated with pH, tVFA or cellulolytic flora. The evolution of the colibacilli population (from 10(7) bact/g on day 22 to 10(3) on day 42) seemed dependent on ontogenic factors rather than on the composition of the caecal media (pH, etc.).

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