The 16S-23S RNA gene intergenic spacers of isolates of Streptococcus equi (n=5), S. zooepidemicus (n=5), S. equisimilis (n=3) and S. dysgalactiae (n=2) were sequenced and compared. There were distinct regions within the spacer, arranged in the order 1–9 for all S. equi and one S. zooepidemicus isolate and 1,2 and 4–9 for the remaining isolates. Region 4 was identical to the tRNAala gene found in the 16S-23S intergenic spacers of other streptococci. Regions 1, 5, 6 and 7 had distinct variations, each conserved in different isolates. However, amongst the intergenic spacers there were different combinations of variant regions, suggesting a role for DNA recombination in their evolution. The intergenic spacer of all isolates of S. equi and one S. zooepidemicus isolate were almost identical. Primers derived from the variant sequences of regions 1 and 5 to 6 were used to group all S. zooepidemicus (n=17) and S. equi (n=5) into 1 of 8 types by polymerase chain reaction; three S. zooepidemicus isolates typed the same as S. equi. S. equi and S. zooepidemicus were clearly distinguishable from S. equisimilis and S. dysgalactiae which had shorter regions 5 and 6 and no region 7. Most homology for the group C sequences was found in previously published sequences for the 16S-23S intergenic spacers of S. anginosis, S. constellatus, S. intermedius, S. salivarius and S. agalactiae. A 75-90 nucleotide length shared with S. anginosus and S. intermedius in opposite orientations in the two main variants of region 6 supported the role for DNA recombination in the evolution of the spacer. The 16S-23S intergenic spacers indicate that S. zooepidemicus was the archetypal species for S. equi and that both are genetically more distant from S. equisimilis and S. dysgalactiae. The intergenic spacer can be used to identify specifically the group C. streptococci and as an epidemiological marker for S. zooepidemicus.

Previous reports in the literature suggest that Burkholderia pseudomallei strains can be differentiated on the basis of animal virulence. Twenty environmentally and clinically derived isolates of Burkholderia pseudomallei were examined for the production of exoenzymes, morphological and biochemical phenotypes and virulence for Syrian golden hamsters. The partial sequence of the 16S ribosomal RNA [rRNA] genes from a number of these strains was also determined. Based upon these observations, it is suggested that highly virulent Burkholderia pseudomallei strains are true Burkholderia pseudomallei strains. The DNA sequences of the 16S rRNA genes of the true Burkholderia pseudomallei strains were identical to the published sequences for Burkholderia pseudomallei while differences were revealed between the published sequences and those of the lowly virulent strains. Thus, these latter strains have been designated as Burkholderia pseudomallei-like organisms since they demonstrate significant differences in exoenzyme production, hamster virulence and 16S rRNA gene sequences.

Cattle were vaccinated with differing doses of an equal mixture of capripox-rinderpest recombinant viruses expressing either the fusion protein (F) or the haemagglutinin protein (H) of rinderpest virus. Animals vaccinated with 2 × 104 p.f.u. or greater of the combined viruses were completely protected against challenge, 1 month later, with both virulent rinderpest and lumpy skin disease viruses. Vaccination with any of the doses did not induce any adverse clinical response in the animals or transmission of the vaccine virus between animals. All cattle challenged 6 or 12 months after vaccination with 2 × 105 p.f.u. of the mixture of recombinant viruses were protected from severe rinderpest disease. Ten out of 18 were completely protected while the remaining 8 developed mild clinical signs of rinderpest. Cattle vaccinated with the recombinant vaccines after prior infection with the parental capripox virus showed more marked clinical signs of rinderpest after challenge with virulent rinderpest, but 9 out of 10 recovered, compared with 80% mortality in the unvaccinated controls.

An outbreak of rubella in April 1996 involved four male British soldiers deployed to Bosnia–Herzegovina. All were helicopter ground crew who were members of the same unit and who periodically travelled to and worked at forward air refuelling stations in Bosnia. There was a potential for spread of the infection to adjacent British units, to troops of other nations in the peacekeeping force, and also to the local civilian population. The British force included 620 female personnel, some of whom may have been non-immune to rubella. One pregnant British servicewoman was repatriated to UK for her own protection. There was a potential health risk, including the possibility of congenital rubella syndrome, in the non-immune wives and partners of deployed male personnel, as a result of contact during the mid-tour home leave of the husbands or partners. The outbreak was monitored through a medical surveillance system known as ARRC 97, and was contained by prompt and rigorous control measures. This outbreak shows the importance of effective surveillance and of good microbiology laboratory support during military operations. The role of immunization against rubella during future military deployments is discussed.

The relationship, in 539 individuals infected with the human immunodeficiency virus (HIV), between two prognostic markers, the CD4 count and beta-2-microglobulin (B2M), and the development of the acquired immunodeficiency syndrome (AIDS) and death was investigated. Cox proportional hazards models were used to determine the risk of AIDS or death. In a multivariate model which adjusted for demographic factors and treatment, the most recent measurements of B2M (relative hazard (RH) 1·37 per g/l higher) and CD4 count (RH 2·17 per log-unit lower) were both significantly associated with the development of AIDS. Similarly, in a multivariate model which additionally adjusted for the development of AIDS as a time dependant covariate, there was a strong relationship with risk of death for the most recent measurements of B2M (RH 1·34 per g/l higher), and CD4 lymphocyte count (RH 1·91 per log-unit lower). A difference in the level of B2M could be used among patients with similar CD4 counts as an indicator of increased risk of progression to AIDS or death. Using the most recent values of these markers provides a better estimate of the risk of AIDS or death, compared to the more common method of analysis, where baseline values of the markers are used.

Ten antisera were produced in rabbits by two or three intravenous injections of inactivated whole influenza type A virions. All contained haemagglutination-inhibition (HI) antibody directed predominantly to an epitope in antigenic site B and, in addition, various amounts of antibodies to an epitope in site A and in site D. The ability of untreated antisera to select neutralization escape mutants was investigated by incubating virus possessing the homologous haemagglutinin with antiserum adjusted to contain anti-B epitope HI titres of 100, 1000 and 10000 HIU/ml. Virus-antiserum mixtures were inoculated into embryonated hen's eggs, and progeny virus examined without further selection. Forty percent of the antisera at a titre of 1000 HIU/ml selected neutralizing antibody escape mutants as defined by their lack of reactivity to Mab HC10 (site B), and unchanged reactivity to other Mabs to site A and site D epitopes. All escape mutant-selecting antisera had a ratio of anti-site B (HC10)-epitope antibody[ratio ]other antibodies of [ges ]2·0[ratio ]1. The antiserum with the highest ratio (7·4[ratio ]1) selected escape mutants in all eggs tested in four different experiments. No antiserum used at a titre of 10000 HIU/ml allowed multiplication of any virus. All antisera used at a titre of 100 HIU/ml permitted virus growth, but this was wild-type (wt) virus. We conclude that a predominant epitope-specific antibody response, a titre of [ges ]1000 HIU/ml, and a low absolute titre of other antibodies ([les ]500 HIU/ml) are three requirements for the selection of escape mutants. None of the antisera in this study could have selected escape mutants without an appropriate dilution factor, so the occurrence of an escape mutant-selecting antiserum in nature is likely to be a rare event.

In order to evaluate prophylaxis and therapy for individuals infected with pathogens by the airborne route, we have designed and built a simple apparatus in which small laboratory animals may be exposed to aerosols of infectious microorganisms. Animals are kept in a chamber closed by a HEPA filter and exposed to the pathogen aerosolized using a Collison nebulizer. Air in the exposure chamber may be sampled to show that the infectious agent is present but the dose of agent must be expressed as 50% effective doses determined by titration. An effective dose may be defined by whatever criteria are chosen to judge disease. Using this apparatus we have shown that St Louis encephalitis (SLE) virus is infectious for mice by the airborne route. These data support the idea that there may be significant hazard to personnel exposed to aerosols of infectious SLE after a laboratory accident.

The prevalence of chronic Chlamydia pneumoniae infection was assessed in 54 patients with established chronic obstructive pulmonary disease (COPD), 41 of these with severe COPD (group I), 13 with mild to moderate COPD (group II), and in 23 patients with community-acquired pneumonia (controls, group III). Specific IgG and IgA antibody levels and circulating immune complexes (ICs) were measured in paired sera, and specific secretory IgA (sIgA) levels in sputum specimens. A polymerase chain reaction (PCR) test was used for the detection of C. pneumoniae in sputum. According to our definite diagnosis criterion, 65% of the COPD patients showed evidence of suspected chronic C. pneumoniae infection and the prevalence was still higher (71%) in patients with severe disease. The occurrence of specific markers of infection was invariably highest in patients with severe COPD, next-highest in patients with mild to moderate COPD and lowest in pneumonia patients. The association between COPD and C. pneumoniae infection persisted after controlling for the potential confounding factors.

A prospective longitudinal study of diseases of lambs born in December and January and housed through to slaughter was carried out on three flocks (A, B and C) between 1989 and 1991. In the first year of the investigation (1989–90) three cohorts of approximately 80 lambs were examined in detail on a regular (weekly or fortnightly) basis. This involved over 2000 examinations and at least one clinical abnormality was observed in each lamb. In the second year (1990–1) the farmers were asked to present sick lambs for treatment on the farm. Farmers from flocks A and B participated in this part of the study; a total of 97/1295 lambs that were slaughtered received at least one treatment.

The carcases and visceral organs of lambs from each flock were observed after slaughter. There was no association between the abnormalities observed during routine examination of the cohort lambs (year 1) and those observed at post mortem meat inspection. However, in year 2, in lambs from flock A, there was a significant association between lambs treated for arthritis or pneumonia on the farm and the presence of arthritic or pleuritic lesions, respectively, post mortem. In both years of the study lambs which were older when slaughtered were significantly more likely to have pleuritic, pneumonic or arthritic lesions at meat inspection.

It was concluded that routine examination of groups of lambs is an inefficient and possibly ineffective method to identify lambs with lesions at slaughter. However, lambs which have been treated for disease, and the older lambs in a flock, had an increased prevalence of lesions post mortem and hence more detailed inspection of these animals would increase the efficiency of meat inspection.

In this study, we investigated the frequency of co-existence of cerebral cysticercosis (CC) in Japanese encephalitis (JE) cases with special emphasis on its role in predicting the final clinical outcome. Amongst the 163 confirmed cases of JE, 37·42% (61/163) had co-existent CC. This was confirmed by antibody detection in the CSF of 45 cases, CT scan of the brain in 6 cases and at autopsy in 3 cases. In 2 cases confirmation was possible by CT scan as well as at autopsy, in 4, CSF antibody levels and CT scan were suggestive of CC while in 1, CSF antibodies and autopsy were suggestive of CC. The co-occurrence of Cysticercus cellulosae in the brain emerged as a prognosticator of poor outcome in JE cases (P<0·03).

Bovine tuberculosis remains a significant problem in some parts of Great Britain and Ireland largely because of a reservoir of infection in badgers. Little is currently known about the immunopathology of Mycobacterium bovis infection in the badger. Badgers, from 31 social groups, in a study area of the Cotswold escarpment, have been trapped and sampled from 1981 to 1995. Serum antibody responses directed against the 25 kDa antigen (MPB83) of M. bovis have been studied in detail in a selected social group (JM) which has endemic infection. Sequential sera from 44 badgers were studied and results compared with culture from faeces, urine, tracheal aspirates, bite wound swabs and at post mortem. The results indicate that some badgers (about 10%) remain uninfected despite exposure to endemic M. bovis infection within the social group. In culture-positive animals active excretion of organisms is not necessarily concomitant with seropositivity. Conversely, seropositivity is not an indicator that culture positivity is present or imminent. This is particularly true in cubs when a transient seropositivity can occur within the first 6–8 months of life but these animals can remain culture-negative for up to 5 years. Western blotting confirms that at least some of these antibodies, detectable by ELISA in the culture-negative cubs, are directed against the 25 kDa M. bovis antigen. In contrast antibodies detectable in the culture-positive animals do not Western blot prior to a positive culture. Thus, differential reactivity in Western blotting may distinguish between serum antibodies indicative of potentially culture-positive animals and animals which will remain culture-negative.

Cattle persistently infected with foot-and-mouth disease virus were treated with dexamethasone to suppress the immune system in an attempt to influence the level of virus recovery from oesophageal–pharyngeal (probang) samples. Twelve carrier cattle were assigned to one of three groups: control; 0·1 mg/kg dexamethasone; and 0·5 mg/kg dexamethasone. Groups 2 and 3 were injected intramuscularly three times weekly for 3 weeks with dexamethasone between days 33 and 56 post-infection with foot-and-mouth disease virus (FMDV). Cattle in both groups developed a leucocytosis, neutrophilia and lymphopenia. The secretory IgA response to FMDV infection was inhibited following, but not during, dexamethasone treatment between days 70 and 98 post-infection (P<0·05). FMDV recovery from probang samples was reduced between days 40 and 64 post-infection (P<0·05) during treatment with either 0·1 or 0·5 mg/kg dexamethasone. Following cessation of dosing with dexamethasone virus recovery returned to control levels. These observations suggest dexamethasone inhibits shedding of FMDV in a reversible manner which may be related to its immunosuppressive, anti-inflammatory or physiological actions.

Diluted dried blood drops on filter paper were compared with serum samples as a specimen source for qualitative anti-HAV antibody determination by ELISA. A total of 298 serum samples and dried blood drops were collected from a population of healthy adolescents (15·3±1·2 years old). The prevalence of anti-HAV antibody obtained by testing serum samples was 7·7% (95% CI: 4·8–10·1). Compared with serum sampling the sensitivity and specificity of diluted dried blood drops were 91·3 and 99·3%. The positive and negative predictive values were 91·3 and 99·3%, respectively, and the likelihood ratios of positive and negative results were 91 and 0·09. It is proposed that this test represents a reliable procedure for anti-HAV antibody testing.