Evaluation of the presence of the bap gene in Staphylococcus aureus isolates recovered from human and animals species.

The implication of biofilm in chronic bacterial infection in many species has triggered an increasing interest in the characterization of genes involved in biofilm formation. The bap gene is a newly identified gene that encodes the biofilm-associated protein, BAP, which is involved in biofilm formation in Staphylococcus aureus. So far the bap gene has only been found in a small proportion of S. aureus strains from bovine mastitis in Spain. In order to study the presence of the bap gene in S. aureus isolates obtained from other species and various locations, a collection of 262 isolates was tested by PCR, using published primers and dot-blot. The results indicated that none of the isolates carried the bap gene suggesting that the prevalence of this gene among S. aureus isolates should be very low.

Serological and molecular comparison of Mannheimia haemolytica and Pasteurella trehalosi strains isolated from wild and domestic ruminants in the French Alps.

Over a period of 17 years, 84 bacterial isolates identified as Mannheimia haemolytica or M. glucosida, and 52 isolates identified as Pasteurella trehalosi were detected in the lungs of domestic and wild ruminants in the French Alps. The isolates were serotyped according to their surface capsular antigens, and those sharing common antigens were further characterized by pulsed field gel electrophoresis. The results showed that the bacterial isolates included in the study clustered according to the host species from which they were isolated. These findings indicate that the transmission of serotypes of M. haemolytica, M. glucosida or P. trehalosi from an animal host in which they are common to another species sharing the same geographical space may be a rare epidemiological event.

Nasal carriage of Staphylococcus aureus in dairy sheep.

The purpose of this study was to assess the prevalence of Staphylococcus aureus nasal carriage of dairy sheep in farms producing cheeses manufactured with raw ewe's milk. The study showed that 29% of ewes carried S. aureus in their nares. The genetic diversity of the 136 isolates recovered from the anterior nares of the ewes, from the ambient air of the milking parlour and from cheeses was investigated using pulsed-field gel electrophoresis (PFGE) of DNA SmaI digests. The genotyping results showed that 75 out of 106 isolates recovered from nasal carriage in dairy sheep belonged to a dominant pattern (previously named OV) and a genetically related pattern (named OV'). The same profile (OV or OV') was found in the ambient air and cheeses, suggesting a continuum between isolates within these different compartments.

Genotyping of Staphylococcus aureus isolated from various sites on farms with dairy sheep using pulsed-field gel electrophoresis.

We investigated the genetic diversity of 179 Staphylococcus aureus isolates recovered from various sites in 10 farms producing cheeses manufactured with raw ewe's milk. Isolates were collected from handcrafted cheeses, bulk tank milk, milk from half-udders, skin abscesses on the udder if present, hands and anterior nares of farmers, and air of the milking area. The isolates were typed using pulsed-field gel electrophoresis (PFGE) of DNA SmaI digests and compared to other isolates of S. aureus isolated in different hosts or in different locations. The results showed that nine farms were contaminated by S. aureus isolates with identical banding patterns (named OV) or by genetically related isolates (named OV'). These dominant banding patterns were found in a variable proportion of the samples from each farm (range: 11-100%). Most of the strains isolated from nasal carriage or strains isolated from other regions or from other animal species had different PFGE patterns to OV or OV', except for three strains. These results show that a single clone of S. aureus is widely distributed both in infected mammary glands and in cheese produced from raw milk. This study confirms that infected mammary glands are the main source of the contamination of dairy products in sheep.

Inoculation of lactating ewes by the intramammary route with Mycoplasma agalactiae: comparative pathogenicity of six field strains.

Contagious agalactia affects goats and sheep. In most infected sheep, the causal agent, Mycoplasma agalactiae, induces mastitis and/or agalactia, keratoconjunctivitis and arthritis. However, a few strains of M. agalactiae were isolated from tank milk from flocks without any clinical signs. The present study was undertaken to compare these apparently "asymptomatic" strains to classical virulent strains in order to assess the pathogenicity of four "asymptomatic" strains. Six groups of lactating ewes were inoculated by the intramammary route with 10(8) viable mycoplasmas of each strain. The clinical signs were regularly evaluated; the excretion of bacteria in milk and the serological response were measured. Ewes were necropsied 7 weeks after inoculation and the level of infection in retromammary lymph nodes was determined. Among the 4 apparently "asymptomatic" strains, 2 were fully virulent as were the strains isolated from discased animals, and the other 2 induced somewhat less severe clinical symptoms. The other parameters, in particular the level of excretion in milk and the level of infection of regional lymph nodes following necropsy were similar for all strains. Mean antibody response was also comparable between the apparently "asymptomatic" and virulent strains, in spite of great individual variability. This observation shows that flocks without any clinical sign from which M. agalactiae is isolated in bulk milk, must be kept under strict control since mycoplasmas may induce severe outbreaks later with changing conditions of breeding.

Subcutaneous and conjunctival vaccination with a live attenuated strain of Salmonella Abortusovis: effect of gestation on serological response of ewes.

Annual serological testing of flocks vaccinated by the subcutaneous route with a live, attenuated strain of Salmonella Abortusovis has previously demonstrated the persistence of agglutinating antibodies. It has however been impossible to determine whether the antibodies originated from the vaccination or from an enzootic infection. The serological response, as measured by a microtechnique of seroagglutination using a stained antigen, was studied in an isolated flock of 30 adult ewes. The trial period after the subcutaneous vaccination was 34 months, which included 3 lambings. Ten female offspring of these ewes were also studied. They were vaccinated by the conjunctival route and were studied for 18 months, which included 1 lambing. As is common for natural or experimental infection, high antibody titers were obtained 10-15 d after vaccination in both groups. The values then decreased and rose again to significant levels at each subsequent pregnancy. The vaccinal strain was never isolated from vaginal swabs taken at each lambing and there was no suggestion of stimulation by an external antigen. Gestation may therefore stimulate the antibody response. This suggests that the immunity conferred by this vaccination may last for at least 3 lambing periods. The consequences of these observations on vaccination protocols and serological diagnosis are discussed.

Salmonella Abortusovis experimental infection induced by the conjunctival route: clinical, serological and bacteriological study of the dose effect in female lambs.

The aim of this work was to explore the first stages of infection with Salmonella Abortusovis after a mucosal inoculation, and to establish an experimental model limiting the bacteriological investigations to the inoculation site. Four groups of 6 ewe-lambs were infected by the conjunctival route with decreasing doses of Salmonella Abortusovis. The clinical and serological survey was completed by a daily bacteriological examination of nasal swabs and faeces. Enumeration of viable bacteria was performed on liver, spleen, lungs and lymph nodes harvested 1, 8, and 22 d after inoculation. A rapid colonization of the cephalic lymph nodes was observed, associated with a transient spreading to prescapular and subiliac lymph nodes without dissemination to the liver and spleen. An irregular and low level faecal excretion was associated with the colonization of mesenteric lymph nodes. The infection by the conjunctival route may either systemically propagated or be locally restricted by the lymphoid system in relation to doses administered. This model uses low infective doses similar to those occurring in field conditions and offers the possibility of limiting the bacteriological control to the regional lymph nodes. It confirms that live attenuated Salmonella strains may be used as vaccinal vectors by the mucosal route.

Abortion and serological reaction of ewes after conjunctival instillation of Salmonella enterica subsp enterica ser abortusovis.

The aim of the experiment was to evaluate in pregnant ewes the clinical, bacteriological and serological effects of conjunctival instillation of S abortusovis. An individual dose of 1 x 10(10) viable S abortusovis were administered to 20 ewes 92 d after mating. Among 18 pregnant ewes, 8 aborted 110 +/- 13 d after mating, 4 had stillborn lambs and 6 a clinically normal lambing (114 +/- 1.3 d). S abortusovis was isolated from placentas, swabs and foetuses of the 12 lambings. Evolution of "H" agglutination titers measured by means of a microtechnique using a coloured antigen was found to be independent of the clinical results. Instillation by conjunctival route could constitute an experimental model closer to a natural mode of infection than the subcutaneous route.

[Experimental infection with Salmonella abortus ovis in rams]. / Infection expérimentale du bélier par Salmonella abortus ovis.

The susceptibility of rams to experimental challenge with Salmonella abortus ovis was investigated by subcutaneous, conjunctival or preputial administration of 1 X 10(10) viable salmonella to 3 groups of 6 adult Préalpes rams. Slaughter and autopsy of 15 rams were made 83 days after challenge. Each of the 3 remaining rams was introduced in 3 groups of 6 salmonellosis-free ewes. The subcutaneous injection caused a significant hyperthermia, a rapid increase in antibody titers without detectable genital excretion of salmonella. The conjunctival or preputial challenge caused a significant serological response without fever; S. abortus ovis was isolated from samples taken 1 to 13 days after challenge only in rams challenged by the preputial route. No salmonella was isolated from organs of the 15 slaughtered rams. Ewes made pregnant by the 3 remaining rams showed no signs of infection. In our experimental conditions, a genital colonization was not observed; a passive genital carriage of S. abortus ovis was shown to be possible; its hypothetical epidemiological role was discussed.