New technologies now enable virologists to study small genetic and antigenic differences between field isolates of animal viruses at a higher level of discrimination than has been possible using conventional serological techniques. The most important of the laboratory techniques revolve around the use of monoclonal antibodies, peptide mapping, fingerprinting of whole RNA virus genomes, RNA:RNA hybridization, ‘electropherotyping’ of virus RNA or polypeptides, restriction enzyme analysis of virus DNA genomes, cloning of genes and rapid sequencing of viral DNAs and RNAs, in the latter case using primer extension techniques (reviewed by Palese & Roizman, 1980). From a practical point of view, genetic and phenotypic heterogeneity among viruses may be of considerable importance in attempts to control certain virus diseases by chemo- or immunoprophylaxis.

Human strains of Mycobacterium tuberculosis were divided into the ‘Classical’ and ‘Asian’ types according to their sensitivity to thiophen-2-carboxylic acid hydrazide. The isolation of these two types in South-East England was studied during a seven-year period (1977–1983). The ‘Asian’ type was more prevalent among ethnic Asian patients than among ethnic Europeans. Among Europeans there was a decline in the isolation rate of ‘Classical’ strains and a small but significant increase in ‘Asian’ strains during the study period, so that the proportion of the latter type in this group is increasing. The type of bacillus was unrelated to the site of isolation except that the incidence of lymphadenitis due to the ‘Asian’ type among European females was significantly higher than expected. In general, European patients tended to be older than Asian patients, and the differences in age distribution according to site of isolation and type of bacillus in each ethnic group were small. A notable exception occurred with European females infected with the ‘Asian’ type, whose age distribution was similar to the Asians.

In view of the differences in behaviour of the two types of human tubercle bacilli in this country there is a need to cintinue a bacteriological surveillance and also to determine whether the nature of the host–pathogen interaction varies according to the type of bacillus.

Staphylococci from 22 cases of toxic shock syndrome with onsets between 1981 and March 1983 have been studied. Another four cases were detected by abstract surveillance. Three of these patients died. The case histories show that the syndrome occurs in women during menstruation as well as in males and in children, and is associated with Staphylococcus aureus infections.

The production of enterotoxins (A, B, C) and toxic shock toxin by S. aureus isolates from toxic shock syndrome was investigated. Twenty-two of the 23 isolates were found to be toxigenie: 7 produced enterotoxin A, 8 produced enterotoxin B, 3 produced enterotoxin C and 13 produced toxic shock toxin. The latter was found with enterotoxin A in five cases, and with enterotoxins A and B in only one case.

Sixty-three percent of 40 S. aureus strains isolated from the vagina of patients with diseases other than toxic shock syndrome produced toxin; eight of these strains produced toxic shock toxin.

In a 12-month survey (June 1982–May 1983) 41 laboratories examined 2493 samples of goat's milk for colony counts and the presence of pathogens. The statutory tests for cow's milk were also applied.

Surface counts of < 105 organisms per ml of raw milk were given by 79% of samples at 37 °C and by 76% at 22 °C. There were < 100 coliforms per ml in 71% of samples, < 10 Escherichia coli per ml in 91%. Staphylococcus aureus was not detected in countable numbers in 96% of samples. Only one isolation of campylobacter was made and two of Yersinia enterocolitica. Salmonella was not detected in 2462 samples. The methylene blue test was carried out on 2368 samples and 86·7% were deemed satisfactory. No sample was Brucella ring-test-positive.

Experiments on the survival and growth of six food poisoning organisms in stored goat's milk showed that Bacillus cereus, Staph. aureus, Salmonella typhimurium and Y. enterocolitica survived quite well and multiplied at the higher storage temperature of 30 °C. Clostridium perfringens only increased 10- to 100-fold while Campylobacter jejuni did not grow.

The results of the survey indicate that any problems with goat's milk relate to poor hygiene during production rather than transmission of organisms from the goat herself.

The virulence of Campylobacter jejuni and C. coli isolated from various water sources was compared with that of clinical strains by in vitro assays of adhesion, invasion and cytotoxicity to HeLa cells. Variation in degree of attachment was observed, but this did not appear to be related to strain source, However, water strains were less invasive and less cytotoxic to HeLa cells than clinical strains as shown by immunofluorescence and electron microscopy.

These differences were particularly evident between clinical and water isolates of the same serotype and biotype implicated in an outbreak of campylobacter enteritis in a school. The enhanced virulence of the clinical isolates, possibly induced by passage, was confirmed by colonization tests on infant mice.

The following enteropathogens were isolated from the faeces of 769 (10·2%) of 7,545 patients of whom 5,704 had diarrhoea or abdominal pain, attending a teaching hospital in Hong Kong during one year: salmonellae 458 (6·1%); Vibrio parahaemolyticus 125 (1·7%); campylobacters 108 (1·4%); shigellae 83 (1·1%); others 19 (0·3 %). Further identification of the campylobacter isolates showed that 63 (58%) were Campylobacter jejuni biotype 1, 44 (41%) were C. coli and only one was C. jejuni biotype 2. Seventy-five (69%) of the 108 campylobacters were isolated from children under two years of age, mostly during the second year of life. Faecal specimens from 1,841 children under the age of two years without gastrointestinal symptoms yielded almost the same percentages of salmonellae, campylobacters and shigellae as children with diarrhoea.

Salmonellae, shigellae and vibrios were isolated most often in the hot late summer months (August to October), but, contrary to the pattern in Europe and North America, both C. jejuni and C. coli were most prevalent in the coolest months of the year (January to March). The reasons for this ‘reversed’ trend are unknown.

The group G streptococcus has generally not been considered a prominent pathogen. In a 1982 study of the colonization rate by β-haemoly tic streptococci in apparently healthy children, age 5–11 years, 25 of 69 isolates belonged to group G. This surprisingly high rate of group G colonization (14·3%) led to a retrospective study of school surveys in 1967 which showed that the colonization rate with this organism was 2·3% (range 1·3–3·5%). A review of bacitracin-sensitive streptococcal isolates from hospital admissions of patients with acute glomerulonephritis (AGN), rheumatic fever, and their siblings, between January 1967 and July 1980, was conducted. Of 1063 bacitracin-sensitive isolates, 63 were group G, and 52 of these were isolated from AGN patients and their siblings, i.e. 7 from skin lesions of AGN patients, 40 from the throats of siblings and only 5 from the skins of the siblings. The other 11 group G isolates were from rheumatic-fever patients and their siblings. Thus, the group G colonization rate fluctuates in the population. The isolation of only group G streptococci from skin lesions of patients with AGN suggests a possible association between group G streptococcal pyoderma and acute post-streptococcal glomerulonephritis.

A collection of 50 bacteriocins was assembled and used to type 802 isolates of Clostridium perfringens from food poisoning outbreaks and a variety of other sources. It was found that strains of the same serotype within an outbreak showed similar patterns of susceptibility to bacteriocins, and the use of a ‘one difference’ rule is proposed for interpretation of the typing patterns of epidemiologically related strains. Isolates of different serotype or of the same serotype isolated from different sources produced many variations in bacteriocin susceptibility patterns.

Two computer programs were developed to assist in the interpretation of bacteriocin typing patterns. Their use showed that related and unrelated strains formed different clusters and enabled a range of the 20 most discriminatory bacteriocins to be selected.

Isolates of C. perfringens from a wide range of sources were screened for their ability to produce bacteriocins. A much greater proportion of the strains from food poisoning outbreaks was bacteriocinogenic than were isolates from human and animal infections, various foods and the environment. The relevance of these findings to the occurrence of C. perfringens food poisoning is discussed.

Less than one per cent of serum samples taken from 257 fish farmers in 1981 had agglutinating antibodies to strains of Leptospira interrogans of serogroup Icterohaemorrhagiae at a titre of 30 or greater. Compared with the results from other serological surveys, this agglutinating antibody prevalence suggests that fish farming does not have a high occupational risk for leptospirosis. Between 1961 and 1981 the incidence in fish farmers was about 33 per 100000 person years at risk. During the same period the incidence in the general adult male population was 0·137 per 100000 person years at risk, so that fish farming had a moderately increased risk of Icterohaemorrhagiae serogroup infection (relative risk = 243). No one particular risk factor within fish farming could be reliably identified and therefore recommendations to reduce the risk can only be general.

The serum antibody responses and 50% protective levels (PL50) of antibody were determined, using the SRH test, at one and twelve months post-vaccination in a group of student volunteers immunized with one of three dosages of a trivalent surface-antigen influenza virus vaccine, or with placebo.

It was found that, for the H3, H1 and B haemagglutinin components present in the vaccine, a dose of 6 μg HA elicited high serum antibody responses at one month post-immunization. High mean antibody levels and a high incidence of volunteers with PL50 values of antibody against each of the HA components of the vaccine remained in the volunteer group twelve months later. The results are discussed in relation to the vaccine dosage used and the nature of the population immunized.

Fourteen influenza A(H3N2) field isolates, mainly obtained during the first weeks of the 1982/83 influenza epidemic in The Netherlands, and nine influenza A(H3N2) reference strains were examined by means of haemagglutination inhibition (HI) tests with 23 potyclonal ferret sera. The resulting HI patterns were subjected to various methods of numerical taxonomy using, among others, taxonomic distance and correlation between strains for resemblance coefficients. Marked differences between distance and correlation coefficients were found in strains which differed in avidity only. The field isolates could be divided into four groups in respect of their taxonomic resemblance to the reference strains. The same grouping was found for five of the field isolates by testing these against 200 human sera.

Seven virus strains antigenically related to the California encephalitis (CE) virus group were isolated from Norwegian Aedes spp. mosquitoes collected in 1976. So far CE viruses have been isolated from five different Aedes spp. in Norway. Furthermore, two virus strains related to the Bunyamwera group were isolated from Anopheles claviger.

Antibodies to CE viruses were demonstrated in 22% of 1014 military recruits tested. Among 91 soldiers who were monitored by monthly blood samples during the mosquito season, seroconversions were detected in 11 individuals. Specific IgM antibodies were found in seven of them. Disease symptoms in connexion with the CE virus infections were not seen. The prevalence of CE antibodies in patients with CNS or respiratory infections was not higher than in control groups. Seroconversions were not seen in any of the groups.

Screening of sheep sera from six different areas in northern Norway indicated significantly different degrees of CE virus activity. Passerine birds may be important CE virus hosts, while small rodents seem unimportant. Specific IgM antibodies were detected in the sera of one of three hares and one of two squirrels.

Of the methods used, single radial haemolysis (SRH) and immuno-electroosmophoresis (IEOP) seemed to be well suited for serological screenings. However, an indirect immunofluorescence antibody test (IFAT) which was used may be an attractive alternative if high-quality anti-species conjugates are available. The haemagglutination-inhibition (HI) test used gave a high number of false positive results.

Small rodents were collected live in two different locations within a nephropathia epidemica (NE) endemic area, and tested for both antiviral serum antibodies and viral antigens in lung sections. In one location, only Apodemus sylvaticus (woodmice) were found in the traps, in the other, both A. sylvaticus and Clethrionomys glareolus (bank voles) were collected.

Among the woodmice from the former location the prevalence of NE virus markers was significantly lower than for either woodmice or bank voles from the other location, and no NE antigen-positive animals was found. The woodmice co-existing with bank voles had a lower prevalence of NE antigen and antibodies than the bank voles, and fewer woodmice had both antibodies and antigen. The results emphasize the important role of bank voles as a major NE virus reservoir and probable source of human infections.

Formalin-fixed samples from 221 animal brains received for rabies diagnosis in Nigeria were digested in 0·1% trypsin in phosphate buffered saline, pH 7·4, and smears stained for rabies antigen by direct immunofluorescence (IF). The results were compared with those obtained using fresh material from the same animals for Negri body staining, mouse inoculation (MI) and occasionally immunofluorescent staining.

From 191 specimens examined for Negri bodies and by mouse inoculation 51 and 64 respectively proved positive. The IF smear technique under investigation failed to detect 5 of these but showed up as positive 30 which had been recorded as Negri-negative and 19 that had gone undetected by MI too. In a direct comparison with IF staining of fresh tissue from 23 known rabies positive animals the similar staining of trypsin-digested formalized smears failed to give a positive result in 2 out of 23 cases.

Some problems were encountered with smears not sticking to slides. When gelatinized slides were used fluorescence was sometimes poorer.

Where transport and refrigeration are difficult and section-cutting equipment is lacking the technique of IF staining of smears prepared from formalized brain tissue after treatment with trypsin can be a useful adjunct to other diagnostic methods. It also makes for safer working where special facilities are absent.