An outbreak of tuberculosis caused by Mycobacterium avium type 2 is described which resulted in the total condemnation of 26 carcasses and partial condemnation of tissues and organs of a further 200 animals. Circumstantial evidence is presented that hens running in the farmyard were the source of the infection.

Examinations of the carcasses and organs of the diseased pigs suggested that the accepted pathogenesis of the disease is incorrect and a new hypothesis is presented. The problems for the meat inspector in differentiating tuberculosis from ‘milk-spot liver’ are discussed and recommendations made.

The findings of the study are discussed in the light of ‘The Meat Inspection Regulations 1963’ and it is recommended that where tuberculosis is suspected there is no longer any necessity to split the carcasses. The public health implications of this study are discussed.

Experimental infection of the vagina of TO and CBA mice with Mycoplasma pulmonis was enchanced greatly by progesterone treatment. Almost all treated animals became infected, whereas only two-thirds of the untreated TO mice and less than half of the untreated CBA mice did so. Almost 1000-fold more organisms were recovered from treated than from untreated mice and the duration of infection was more than doubled. The enhanced infection in the hormone-treated animals was accompanied by a more severe vaginal polymorphonuclear leucocyte response which reached a maximum two weeks after inoculation of M. pulmonis. In the to mice the eventual decline in cellular response coincided with the gradual disappearance of the mycoplasmal infection. The implications of these findings for genital infections of other animal species are discussed.

Two solid selective media, xylose deoxycholate citrate agar (XDCA) and bile salts brilliant green agar (BBG) and an enrichment broth–alkaline peptone water, were evaluated for the isolation of Aeromonas hydrophila and Plesiomonas shigelloides. Alkaline peptone water and XDCA are useful for recovery of Aeromonas but not Plesiomonas, whereas BBG is satisfactory for both organisms.

The majority (85%) of shigella isolated in 1980 and 1981 in Korea were Shigella flexneri, the others were Sh. sonnei (14%) with only a small number of Sh. dysenteriae. Only 14 of the 459 strains of shigella isolated were susceptible to all 12 drugs tested, and 445 were resistant to three or more drugs. Strains multiply resistant to the six drugs, chloramphenicol (Cm), tetracycline (Tc), streptomycin (Sm), sulfisomidine (Su), ampicillin (Ap) and trimethoprim (Tp) were most frequently encountered, followed by those resistant to Cm, Tc, Sm, Su and Tp. The complete patterns of resistance to drugs except nalidixic acid and rifampin in approximately 73% of drug-resistant strains were co-transferred to Escherichia coli by conjugation, indicating that the resistance was R plasmid-mediated. Randomly selected R plasmids conferring various patterns of resistance markers were tested for the incompatibility groups, and almost all of them were classified into Inc FII. Two of three R plasmids conferring resistance to Cm, Tc, Sm and Su were classified into Inc B and one to Inc FII. Two R types with resistance markers of Cm, Tc, Sm and Ap were not classified with our standard plasmids used.

A case of Corynebacterium ulcerans sore throat in a community that drank raw milk from its own farm led to the discovery of another symptomless human infection. Eight cows in the herd were found to be infected and the intermittent pattern of excretion was demonstrated in another cow followed through its lactation. Further evidence of milk infected by C. ulcerans was found by examining all raw milk samples submitted to the laboratory. Two other human cases were diagnosed in Devon during the period of this investigation.

Intracerebral inoculation was more effective than intraperitoneal, intravenous or subcutaneous inoculation as a means of producing lethal infections with Fusobacterium necrophorum in mice. Strains varied in virulence but, of five examined, two had LD50 values as low as ca. 8000 and 14000 viable organisms. Profuse bacterial multiplication in the brain was demonstrated. Intravenous vaccination with a single large dose of heat-killed whole culture or washed bacterial cells failed to protect against intracerebral challenge.

Intracerebral injection of other fusobacteria (F. nucleatum, F. varium and F. necrogenes) and of 22 strains belonging to 10 Bacteroides spp. was without apparent effect on mice, except for a slight transient illness in some animals given B. fragilis. This organism (five strains) differed from the other Bacteroides spp. tested, which included eight strains belonging to the fragilis group, in being eliminated more slowly from the mouse brain – a point that may be relevant to the special pathogenicity of B. fragilis in endogenous infections in man. There was no evidence that B. fragilis multiplied in the brain or that intravenous vaccination with a large dose of heat-killed homologous culture affected the rate at which it was eliminated.

The distribution of specific phage types of Salmonella typhimurium within the Australian chicken industry has been studied and documented on an Australia wide and state-by-state basis. A total of 1799 strains of S. typhimurium were obtained from Australia-wide sources and phage typing categorized 1498 of these isolates into 30 distinct phage types, with the remaining 301 strains untypable. Five phage types, 6, 26, 31, 135 and 179, accounted for 76% of the total strains typed, with the remaining 24% of strains being distributed among 25 phage types.

Of the major phage types, type 31 was restricted to Victoria and Western Australia, but the other types were distributed throughout Australia.

In addition, the antibiotic resistance pattern of the various phage types was determined and only five of the 30 phage types showed appreciable levels of resistance.

The mechanisms whereby staphylococcal strains grown in plasma assume increased resistance to polymorph bactericidins were investigated. Observations reported here showed that cultural conditions could determine the path of conversion to resistance. Staphylococcal strains and mutants lacking either free coagulase or clumping factor or both all showed enhanced resistance after 10 h incubation in plasma proteins, thus giving no clear indication that these factors were involved in the interactions. In fact, prolonged incubation in bovine serum albumin (22 h) and ordinary broth medium (24 h) also resulted in increased resistance. A distinction between staphylococcal factors interacting specifically with plasma proteins and such non-specific conversions was obtained in two different ways. Stripping of a hypothetical surface protein by treatment with trypsin or 2 M potassium bromide rendered plasma- but not 24 h-broth organisms susceptible, indicating protein coating of plasma-grown organisms. Also free coagulase-positive strains and mutants incubated in plasma for 30 min were converted while those lacking both or possessing clumping factor alone were not. It therefore appears that one of the mechanisms of acquiring resistance involves a rapid interaction between staphylococcal-free coagulase and fibrinogen, resulting in the deposition of fibrin or fibrin derivatives on the bacterial surface.

An ‘in use’ test was developed to investigate effectiveness of disinfectant application and of detergent of hot water cleaning at kitchen, bathroom and toilet sites in the domestic environment. Detergent and hot water cleaning produced no observable reduction in microbial contamination. Single and daily application tests demonstrated that hypochlorite and phenolic disinfectants can be used to produce substantial reductions in bacterial contaminationin the home. Results indicate that maximum protection afforded by disinfection is relatively brief; 3–6 h after disinfection, contamination levels were only marginally less than those observed at pretreatment. Some suggestions are made for improvements in home hygiene.

In recent years widespread circulation of salmonella and shigella strains resistantto multiple antibiotics has become an international problem. Accordingly the bacterial sensitivity to a range of antibiotics has been assessed in vitro and recorded for the period 1979–83 for patients from the Al Qassimi Hospital. A total of 229 enteric pathogens from 148 children and 59 adult patients were isolated and studied. Most of the enterobacteria were sensitive to colistin, gentamicin, trimethoprim and chloramphenicol (Salmonella typhi approached 100% sensitivity). High rates of sensitivity were also found to ampicillin in S. typhi (96%) and other salmonella serotypes (85%), whilst only 57% of Shigella species and 14% of Escherichia coli were sensitive to this antibiotic. Low rates of sensitivity to sulphamethoxazole, streptomycin and tetracycline were found in shigella and E. coli (ranging from 7 to 14%). Approximately 50% of S. typhi and other salmonella serotypes were sensitive to sulphamethoxazole and streptomycin and 80% to tetracycline. Resistance to three or more antibiotics was very common in shigella and enteropathogenic strains of E. coli (74–85%), less common in non-typhoid salmonella (29%) and exceptional in S. typhi strains. In general, shigella and E. coli isolates showed a high rate of resistance to several antibiotics, whilst S. typhi and other salmonella serotypes retained their original sensitivity to most of the antibiotics used in clinical practice.

The molecular epidemiology of rotavirus infections in Glasgow and the west of Scotland during 1981/82 and 1982/83 was investigated by electron microscopy, ELISA testing and RNA migration pattern analysis. In 1981/82, rotaviruses of both the ‘long’ and the ‘short’ electropherotype (in different variants) co-circulated from the onset throughout the winter peak of the outbreak. Approximately 80 % of the children were infected during the first year of life. No differences in incidence were found between sexes. In 1982/83 the isolated rotaviruses were almost exclusively of the ‘long’ electropherotype (in different variants) and 36% of the children were infected beyond the first year of life. Rotaviruses of the ‘long’ electropherotype serologically were of subgroup II and serotype 1 and those of the ‘short’ electropherotype of subgroup I and serotype 2.

A newly developed lectin neuraminidase test (LNT) and a panel of mouse monoclonal and post-infection ferret antibodies have been used to analyse antigenic drift in N1 neuraminidases of influenza A viruses isolated between 1933 and 1957 and also between 1977 and 1980. Significant antigenic differences were detected among the ‘early’ (1933–57) viruses since the NA of viruses isolated one year apart could be distinguished serologically. The NA ofthe ‘re-emerged’ virus A/USSR/92/77 (H1N1) was antigenically related but not identical to influenza A viruses isolated in 1949 (A/Paris/49 (H1N1), A/Geneva/49 (H1N1)) which thus predates the previously observed antigenic similarity of A/USSR/77 with A/FW/50 (H1N1) virus.

A cold-adapted influenza A virus, CR-37 (H1N1), derived from genetic reassortment between A/Ann Arbor/6/60 (H2N2) cold-adapted variant virus and A/California/10/78 (H1N1) wild-type virus, was tested in Japanese adult volunteers. The CR-37 live virus preparation induced only low-grade clinical reactionsin volunteers for the first 3–4 days after inoculation. Two vaccinees who did not show any antibody changes became febrile (over 38–0 °C). Skin tests using the vaccine preparation and uninfected allantoic fluid were performed, and indicated that one of these two vaccinees was positive for the CR-37 vaccine preparation. A high proportion of the vaccinees whose sera had a haemagglutination-inhibition (HI) antibody titre against thevaccine strain of ≤ 64 before inoculation, seroconverted in both HI and neuraminidase-inhibition (NA1) antibody titrations, and only a few seroconverted in the titration of antibody against type-specific internal antigens. The serological examinations against heterotypic H1N1 variants indicated that the cold-adapted live influenza virus vaccine could induce a broad spectrum of HI antibody reactivity and immunity of long duration.

Four antigenic variants of the neuraminidase (NA) of A/Texas/77 (H3N2) virus were selected using monoclonal antibody at a frequency of one variant in 105 parental virions. The antigenic variants failed to react serologically with the monoclonal antibody used for their selection in vitro. The antigenic variants failed also to react serologically with a proportion of sera from children and adults although all of the sera reacted with the parental A/Texas/77 virus. Thus, certain human sera have a restricted antibody repertoire to influenza NA antigen which might enable virus antigenic variants to avoid anti-NA antibody-mediated neutralization in nature.

A small epidemic of nursery-associated hepatitis A (HA), in which silently infected children played a cryptic role in transmitting the illness to adult contacts, was investigated. It was found that a male nurse had transmitted HA to four children before he fell ill. He was not heard from for about two months as he was a part-time worker and was admitted to a local hospital in another prefecture. Two of the four silently infected children transmitted HA to their parents who then revealed the presence of nursery-associated HA. The epidemic was terminated by injection of human gamma globulin to nursery children and to antibody-negative parents, nursery staff and other contacts except for two breakthrough cases.