Leukotoxic factors produced by staphylococci of ovine origin.

Leukotoxins produced by staphylococci, especially Staphylococcus aureus, have long been considered important virulence determinants. The present assay examined 26 strains of staphylococci isolated from sheep for their ability to produce factors leukotoxic to polymorphonuclear leukocytes deriving from ovine mammary glands. Twenty one strains were coagulase-negative staphylococci and five coagulase-positive. Of the coagulase-negative staphylococci 17 were isolated from subclinical mastitis and four from the teat skin. The coagulase-positive strains were isolated from clinical mastitis and caused death to 91-100% of the cells. The coagulase-negative strains isolated from subclinical mastitis caused death to less than 50% of cells, while those from the skin did not affect any cells. The concentration of active leukotoxins is an important staphylococcal virulence factor. Low production of leukotoxins or no production by coagulase-negative staphylococci may determine their ability to survive the mammary gland defenses or cause clinical mastitis.

Use of exfoliative cytology in the diagnosis of ovine keratoconjunctivitis.

The cells present in the conjunctival sacs of 142 healthy sheep and 87 sheep with ovine keratoconjunctivitis were examined. The most numerous cells in the healthy conjunctival sacs were epithelial cells and occasionally lymphocytes; neutrophils were rarely present. Ovine keratoconjunctivitis was characterised by a rapid onset of acute inflammation of the conjunctiva, followed by hyperaemia of the sclera and pannus, and opacity of the cornea. The most numerous cells in the acute phase were neutrophils, and the presence of plasma cells was also suspected. The use of cytological methods to aid the detection of Mycoplasma conjunctivae, the organism most commonly isolated from cases of ovine keratoconjunctivitis in Britain are discussed.

An investigation of colonization of the conjunctival sac of sheep by bacteria and mycoplasmas.

The conjunctival sacs of 100 healthy adult ewes and 20 lambs and 76 adult ewes affected by ovine keratoconjunctivitis (OKC) were examined microbiologically. Branhamella ovis was the only organism regularly isolated from healthy ewes and lambs, Mycoplasma conjunctivae was isolated from the conjunctival sac of nine ewes but its occurrence was not associated with clinical signs of ovine keratoconjunctivitis. Mycoplasma conjunctivae and Branhamella ovis were isolated significantly more often from eyes affected by OKC than from unaffected eyes.

The role of Branhamella ovis, Mycoplasma conjunctivae and Chlamydia psittaci in conjunctivitis of sheep.

Smooth (S) and rough (R) types of Branhamella ovis were used alone and in conjunction with Mycoplasma conjunctivae and Chlamydia psittaci in attempts to produce conjunctivitis in lambs. This was only successful with one S-type previously isolated from a clinical case of conjunctivitis. In experimental mixed infection, B. ovis contributed to the severity of ovine keratoconjunctivitis attributable to infection with Mycoplasma conjunctivae. When B. ovis and C. psittaci were inoculated into the conjunctival sac mild conjunctivitis was produced but C. psittaci could not be re-isolated.

Some cultural characteristics of Branhamella ovis isolated from the conjunctival sac of sheep.

The colonial morphology and other cultural characteristics of Branhamella ovis were studied. The current investigation showed that colonies could be designated R (rough) and S (smooth) dependent on their appearance on agar. The colonial variants were apparently stable and each produced distinct types of pitting when grown on agar. A CAMP-like reaction was also shown to be a characteristic of B. ovis.

Experimental infection of the conjunctival sac of lambs with Mycoplasma conjunctivae.

Ovine keratoconjunctivitis (OKC) identical to that seen in field cases was produced experimentally with 10(6) colony forming units of an isolate of Mycoplasma conjunctivae which had been passaged three times in vitro. Cytological studies showed that the peak neutrophil count in conjunctival exudate occurred 8 days after inoculation of the conjunctival sac. Rapid onset of clinical signs in the uninoculated eye showed the ease with which the organism could be transferred from affected to unaffected eyes.

The use of fluorescein-conjugated monoclonal antibodies, cell culture and transmission electron microscopy to detect Chlamydia psittaci and associated lesions in experimentally infected mice.

An immunofluorescence test based on a monoclonal antibody (mAb) was used to demonstrate chlamydiae in formalin-fixed and paraffin wax-embedded tissues from 10 adult mice experimentally infected by the oral route with Chlamydia psittaci isolated from the fetal membranes of an aborted ovine fetus. Samples of lung, jejunum and spleen were examined by bright-field microscopy, immunofluorescence and transmission electron microscopy, and were cultured for chlamydia in McCoy cells. These tissues were compared with those of two control mice. All infected mice had splenic hyperplasia and two had pneumonia. The lung appeared to be the target organ for C. psittaci administered by the oral route. Chlamydiae were identified in the lungs of five mice by immunofluorescence, bright-field and transmission electron microscopy. Chlamydiae were cultured from the jejunum of two mice and the spleen of one, but could not be identified at these sites by other methods. Immunofluorescence with an anti-chlamydia mAb was useful for detecting chlamydial antigen in formalin-fixed paraffin wax-embedded samples.

Experimental conjunctival infection of lambs with a strain of Chlamydia psittaci isolated from the eyes of a sheep naturally affected with keratoconjunctivitis.

Five ram-lambs were inoculated into the left conjunctival sac with the 15R isolate of Chlamydia psittaci, recovered from a sheep with keratoconjunctivitis. A sixth ram-lamb was kept in contact with them. The five lambs developed varying degrees of acute conjunctivitis and 14 days later C psittaci could be recovered from the inoculated eyes, from which Branhamella ovis was also isolated. The eyes were examined regularly for four months; C psittaci could not be re-isolated but the eyes developed varying degrees of follicular conjunctivitis. After four months the sheep were treated with corticosteroids in an attempt to reactivate a latent chlamydial infection but no chlamydiae could be isolated. Five months after the start of the experiment the six lambs were inoculated with 15R into the left conjunctival sacs. Acute conjunctivitis developed which was not as severe as after the first inoculation, but C psittaci could only be recovered from the left eyes of three sheep three days after inoculation. The eyes remained chronically affected by follicular conjunctivitis. Six months after the start of the experiment the left eyes were again inoculated with 15R; on this occasion acute conjunctivitis did not develop and chlamydiae could not be isolated. Chronic follicular conjunctivitis persisted until the experiment was terminated three months later.

Clinical and immunological responses of ewes following vaccination with an experimental formalin-inactivated Chlamydia psittaci (ovis) vaccine and subsequent challenge with the live organism during pregnancy.

The protection afforded by an experimental, killed, adjuvanted vaccine derived from the A22 strain of Chlamydia psittaci (ovis) against ovine enzootic abortion was studied. The vaccine was used undiluted (group A), at a dilution of 10(-3) (group B) and at a dilution of 10(-6) (group C). A fourth control group (group D) was inoculated with all components of the vaccine except the chlamydial antigen. A group of rams (group R) was also vaccinated with the chlamydial antigen diluted to 10(-3). Animals were challenged 70 days after mating with the A22 strain of C. psittaci (ovis) and were studied throughout pregnancy and the subsequent lambing period. Their cell-mediated immune responses were examined using a skin test and their humoral immune responses were studied using an ELISA. Tests for excretion of chlamydiae in their faeces and genital tract during pregnancy and after parturition and in the faeces of their lambs were made. The reproductive performance of the ewes was assessed by calculating the average weight of lambs produced per ewe in each group. The experimental vaccine protected the ewes in groups A and B against challenge with C. psittaci (ovis) as none showed clinical signs of OEA or excreted chlamydiae. The average weight of lambs produced per ewe in both groups was greater than 4 kg. Both groups seroconverted after vaccination but not all of them were positive to the skin test. The experimental vaccine at 10(-6) dilution of antigen did not protect the ewes as three of 10 ewes displayed clinical OEA and excreted chlamydiae in the products of parturition.(ABSTRACT TRUNCATED AT 250 WORDS)

Protection of ewes vaccinated with A22 strain Chlamydia psittaci (ovis) against challenge in pregnancy with homologous and heterologous strains of the organism.

Fifty ewes were randomly divided into four groups. Groups A and B were vaccinated with an experimental vaccine derived from the A22 isolate of Chlamydia psittaci (ovis), an isolate known to cause ovine enzootic abortion (OEA). Groups C and D were unvaccinated controls. In mid-pregnancy, animals in group A and C were challenged with live A22 C. psittaci (ovis) and those in B and D were challenged with a field isolate of the organism (BS) against which the commercially available A22 vaccine appeared to offer poor protection. In group A, three animals showed clinical signs of OEA and six excreted chlamydiae. In group B, five ewes showed clinical signs of OEA and excreted chlamydiae. In group C, three ewes had clinical signs of OEA but seven excreted chlamydiae. In group D, all 11 ewes showed clinical signs of OEA and excreted chlamydiae in the products of parturition. This group produced only four live lambs with an average weight of viable lamb per ewe of 1.4 kg, whereas the other groups each produced 12 or 13 lambs with an average weight of viable lamb per ewe of more than 4 kg. The BS isolate was much more virulent than the A22 isolate for unvaccinated, pregnant ewes. However, the A22 vaccine offered significant protection against the heterologous BS isolate although on this occasion it did not appear to alter the course of disease produced by the less pathogenic A22 isolate.

A simple staining method for the identification of chlamydial elementary bodies in the fetal membranes of sheep affected by ovine enzootic abortion.

A dark-ground methylene blue (DGMB) staining method was used to demonstrate chlamydial elementary bodies in fetal membranes of sheep affected by Chlamydia psittaci. Before evaluation on material from clinically affected animals, the DGMB method was compared with modified Ziehl-Neelsen (MZN) and dark-ground Giemsa (DGG) staining methods for its ability to demonstrate chlamydial elementary bodies in hens' eggs which had been experimentally infected with C. psittaci. DGMB was more specific in its staining of chlamydial elementary bodies than DGG or MZN. The DGMB method was found to be a more reliable technique for the examination of fetal membranes from sheep affected with C. psittaci than DGG or MZN. Those samples diagnosed as positive using the DGMB showed a good correlation with those diagnosed as positive on macroscopic examination.

The carriage of Corynebacterium suis in male pigs.

This investigation was designed to determine the prevalence of Corynebacterium suis in the preputial diverticulum of pigs of various age groups, located in different parts of the U.K., and to demonstrate whether the organism is transmissible between male pigs. C. suis was isolated from almost 90% of 224 adult males, distributed among 25 pig units in widely separated regions of the country and in 96% of 66 pigs aged 5-6 months originating from six different herds in East Anglia. The rate of isolation of C. suis from younger pigs depended, at least in part, on the system of husbandry practised. Thus, in one herd, A, in which young pigs were maintained in comparative isolation, none of 26 pigs aged 5-8 weeks harboured C. suis; however, in the same herd, the organism was isolated from 77% of 64 pigs aged 9-15 weeks which were in close contact with male pigs aged up to 6 months. In another herd, B, in which individual litters were housed in the same pen from birth to 5 months of age, C. suis was isolated once from only one of 36 pigs in the age range 5-17 weeks, sampled on two occasions, with an interval of 5 weeks between each sampling.(ABSTRACT TRUNCATED AT 250 WORDS)