The radioimmunoassay for brucellosis previously reported from this laboratory was a sensitive and useful method for detecting antibody against Brucella abortus in bovine serum. Changes in the procedure have improved sensitivity, have apparently increased interassay precision, and have made the assay easier to perform.

Antibodies have been used for the last five decades in the laboratory diagnosis of a wide range of diseases caused by viruses and in detailed investigations of virus structure. However, immunological and serological assays have always had problems of interpretation, reproducibility and standardization, resulting partly from the unavoidable heterogeneity of the antibodies in the test. When a mouse, for example, is immunized with a virus, the animal may easily recognise 10–20 different antigenic determinants. As many as five distinct antibodies can be produced by the mouse against each determinant and these will often differ from antibodies made by another mouse against the same antigenic determinant. The method of lymphocyte fusion and the subsequent generation of monoclonal antibodies (Kohler & Milstein, 1975; Kohler, 1980) overcomes these limitations.

Serum samples were obtained from 281 heifers vaccinated with Brucella abortus strain 19, and from 50 heifers that had received two injections of killed B. abortus strain 45/20 adjuvant (K45/20A) vaccine. The serological response measured by the brucellosis radioimmunoassay (RIA) was compared with responses measured by other tests.

The serological responses of cattle during the first weeks after strain 19 vaccination were found to give little guide to the frequency of persistent reactions.

In the case of strain 19, persistent reactions were considered to be those occurring 12 or more months after vaccination. In heifers vaccinated at the recommended age, small numbers of persistent reactions were given by the RIA (four in 374 sera), the complement fixation test using warm fixation (CFTW) (six in 383) and cold fixation (one in 185), the serum agglutination test (two in 222) and the indirect haemolysis test (IHLT) (two in 369). The Rose Bengal plate test gave 74 persistent reactions in 374 sera.

Five of the 50 heifers gave particularly prolonged responses to K45/20A vaccine. In these animals the RIA and IHLT remained positive for longer than the CFTW.

Fourteen recirculating cooling water systems were surveyed during the summer, 1981, to see what factors might influence the prevalence of Legionella pneumophila. The effect on the organism of three anti-microbials was studied, each in two systems, by intermittent treatment at two week intervals.

L. pneumophila was isolated from six of the 14 cooling systems at the beginning of the trial but by the end was present in ten. An association was found between the presence of the organism and the concentration of dissolved solids, and chlorides and the pH. There also appeared to be associations with exclusion of light and higher water temperatures.

Repeated tests on eight untreated systems showed that two were consistently infected, three became and remained infected, one was infected on a single occasion and two were never infected with L. pneumophila. Treatment of a contaminated system, either with a 10 p.p.m mixture of a quaternary ammonium compound and tributyltinoxide or slow release chlorine briquettes (maximum recorded free chlorine level 1·2 p.p.m.), did not eliminated legionellae. Treatment of two infected towers with a chlorinated phenol (100 p.p.m.) eliminated legionellae for at least three days, but after 14 days the organism was again found.

The incidence and clinical features of campylobacter enteritis were studied in a defined general practice population over a period of three years. Specimens of faeces were cultured from a representative sample of patients suffering from acute enteritis. Of 168 patients submitting a specimen to the laboratory 34 (20·2%) were positive for thermophilic Campylobacter species. The projected campylobacter infection rate varied from 5·4% per annum in infancy to 0·3% per annum in the 5- to 14-year-olds with a mean of 1·1% per annum for the whole study population.

During the same period campylobacters were isolated from 484 (14·9%) of 3250 patients suffering from acute enteritis whose general practitioners had sent faecal specimens to the laboratory, confirming the importance of this organism in the aetiology of acute enteritis in the community.

Good antibody responses usually follow infection with Campylobacter jejuni. A comparison of agglutination, complement fixation and immunofluorescence tests was done on 55 sera from 40 sporadic patients with diarrhoeal disease and positive cultures for C. jejuni. Results showed 82 % positive with immunofluorescence, 62 % by complement fixation but only 38 % by agglutination, using two reference strains COP and MEL as antigens. Overall 90 % of the 40 patients were positive by one or more serological tests. Paired sera from 15 patients showed a fourfold or greater rise in only five, confirming previous observations that antibody formation occurs early in the course of infection. Results also suggest that different test systems may be detecting antibodies of different specificities. Results confirm the value of serological tests, but further information on serotypes is required for selection of suitable reference strains.

The serology of 27 heifers found to be positive to culture after inoculation with Brucella abortus strain 544, was studied. Eighteen heifers had previously been vaccinated with strain 19 or strain 45/20 and nine were unvaccinated. Post-infection serum samples were tested for Brucella antibodies by radioimmunoassay (RIA), complement fixation test (CFT), indirect haemolysis test (IHLT) and Rose Bengal plate test (RBPT).

All of the unvaccinated heifers showed strong humoral responses to experimental infection in the RIA, CFT, IHLT and RBPT. The CFT and RBPT became positive sooner after infection than the other tests in the unvaccinated heifers. However, in vaccinated heifers the RIA was the most sensitive test early in infection and the results of the RBPT were variable. Three of the vaccinated heifers showed weak and inconsistent humoral responses and, in these animals, the RIA gave fewer false negative reactions than the other tests.

Between January 1968 and December 1977, 635 cases of acute bacterial meningitis were admitted to hospitals in the Birmingham Area Health Authority. The epidemiology of these cases was analysed and compared with the 270 cases which were admitted to the regional infectious diseases unit at East Birmingham Hospital (E.B.H.). In children and young adults the meningococcus was the commonest causative organism while over the age of 25 pneumococcal meningitis predominated. Although Haemophilus influenzae was the second commonest infecting organism it was a rare cause of meningitis in school children and adults, only four cases presenting in these age groups in the Birmingham Area.

A detailed analysis was made of the symptoms, signs, laboratory investigations and clinical course of the 270 cases treated at E.B.H.

The mortality in the patients with pneumococcal meningitis was 30%. In the meningococcal group it was 3·5% and in the haemophilus groups 7·7%.

An analysis of the various treatment regimes employed in the 270 E.B.H. patients supports the view that a single antibiotic is sufficient for the therapy of most forms of bacterial meningitis. Intrathecal antibiotic administration is unnecessary in pyogenic meningitis caused by meningococci, pneumococci or H. influenzae.

The exotoxins produced by ten strains of C. ulcerans (two human, six bovine and two equine) have been studied. On the criteria of toxin–antitoxin neutralisation and immunoprecipitation tests using highly specific diphtheria and C. ovis antitoxins with crude toxic filtrates, (NH4)2SO4 concentrates, and partially purified chromatographic preparations of these, together with the presence or absence of inhibition of the action of staphylococcal beta-haemolysin, and the reaction produced when injected intradermally into rabbits, two toxins could be identified, namely diphtheria toxin and C. ovis toxin. There was no evidence for the production of a third toxin specific for C. ulcerans. Five strains produced both diphtheria and C. ovis toxins. In four diphtheria toxin predominated, but in the fifth C. ovis toxin predominated. Two strains produced only diphtheria toxin and two only C. ovis toxin, though there was good but not complete evidence that a third strain (Revell) also fell into this latter group. Considerable variation occurred in the concentration of each toxin and, where both were present, in the proportion of each.

A retrospective survey was carried out for isolations of salmonellas from humans, foods and sewer swabs from food-handling premises for the period 1976–80.

The predominant serotypes isolated from humans were S. typhimurium, S. hadar, S. virchow and S. agona.

Salmonellas were found in less than 1% of cooked pork and poultry products and were not detected in cooked beef or lamb. The isolation rates for cooked offal and cooked open pet foods were 2·1% and 19·7% respectively. Isolation rates for uncooked meats ranged from 5% for beef to 36% for poultry. Most of the uncooked meats were sausages in which the predominant serotypes were S. derby, S. typhimurium, S. heidelberg and S. panama.

An attempt was made to investigate the relationship between serotypes isolated from humans and from sausages and sewer swabs. S. typhimurium and S. bredeney were predominant in humans, sausages and sewer swabs whilst S. derby, S. panama and S. give were predominant only in sausages and sewer swabs.

Thirty-one laboratories examined a total of 6169 meat samples, 1236 from abattoirs and 4933 from retail and other outlets. Campylobacter jejuni was isolated from 98 (1·6%). A higher isolation rate of 49/1236 (4·0%) was found among abattoir than among retail and other samples (49/4933–1·0%). Twenty-two of the laboratories looked for salmonella; although 94/4002 (2·3%) were positive, in only one sample of minced beef were campylobacter and salmonella found together. Isolation rates for salmonellae were 75/3576 (2·1%) from retail and 19/426 (4·5%) from abattoir samples.

Analysis of the results revealed that (1) the contamination rate of raw red meat by C. jejuni is, in general, very low; (2) when contaminated, numbers of organisms are generally also very low; (3) enrichment procedures were of some value; 41/98 (42%) isolates were detected by enrichment only, but, on the other hand 8 (8%) were direct plate positive/enrichment negative; (4) practice at looking for the organism and increased seasonal temperatures over the survey period did not result in a noticeable increase in isolations; (5) there was no apparent correlation between campylobacter and salmonella isolations.

Twelve strains of Bordetella pertussis, of various serotypes, were tested by agglutination with serial dilutions of six antisera which were thought by their donor to be monospecific for six distinct agglutinogens.

The first three sera were shown, by agglutination of the twelve donated strains and of standard pertussis serotypes, to be monospecific for the three well-recognized major agglutinogens (factor 1, factor 2, factor 3).

The ‘factor 4’ serum gave weak agglutination, but only of strains that possessed factor 2, though not all of such strains. This suggested that it may be a distinct minor component of factor 2.

The ‘factor 5’ serum was very weak, and gave agglutination only with a few of the factor 2 strains.

The titres of the ‘factor 6’ serum were very closely parallel to those of the factor 3 serum, and it may be inferred that these ‘factors’ probably constitute a single antigenic entity.

Seven of the twelve donated strains were shown to be mixtures of two or more serotypes, offering an explanation for discrepancies in serological tests involving the use of these strains on different occasions.

It seems likely that ‘factors 5 and 6’ do not actually exist; and, since ‘factor 4’ is only a minor component of factor 2, any protective role that it may have would probably be covered by the presence of factor 2 in vaccine.

An international collection of 419 isolates of Salmonella agona was phage typed, biotyped and colicine typed. Of 16 recognized phage types, 15 were represented. Three phage types (I, V and XVI) accounted for 84% of all isolates, were widely distributed and may be interconvertible. Biotyping afforded little type differentiation; thus 92·6% of the isolates belonged to biotype 1 a. A rhamnose non-fermenting variant line (of biotype 5a) became established in Zaire from 1979 to 1980. A maltose late-fermenting line of biotype 1 a, isolated in Scotland in 1974, did not thereafter become established. Two Col+ lines (producing colicine I b) accounted for 45 of 68 colicinogenic isolates. The implication of type diversification and the phylogenetic significance of these findings are discussed.

Hospital outbreaks of severe gastroenteritis caused by multi-resistant Salmonellatyphimurium have occurred in a number of cities throughout India since 1977. The strains involved belong to phage types 66 or 122, or are untypable; the latter are derived from types 66 or 122 by acquisition of one or more of a number of temperate bacteriophages. Types 66 and 122 are closely related and react with the same phages of the S. typhimurium typing scheme.

A plasmid belonging to compatibility group FIme encoding resistance to ampicillin, chloramphenicol, kanamycin, streptomycin, sulphonamides, spectinomycin, tetracyclines, gentamicin and trimethoprim (R-type ACKSSuSpTGTm) is present in all of the multi-resistant strains. Several other plasmids have been identified including an SSu resistance determinant, a group I2, transfer factor and an R factor coding for resistance to kanamycin, streptomycin and sulphonamides which is compatible with plasmids of all the standard compatibility groups. These plasmids are only present in a proportion of the strains examined.

Examination of strains from other sources has identified a paediatric hospital outbreak in Saudi Arabia and a number of sporadic infections in Great Britain which have been caused by the same organisms. These studies show that, despite differences in phage type and plasmid content, this group of strains belongs to a single clone which has become widespread in India with some extension to other countries.

One hundred and five shigella isolates from Addis Ababa were studied to determine serogroup frequency and in vitro antibacterial drug sensitivity.

About 70 % of the isolates were Shigella Flexneri followed by Sh. dysenteriae (15%), Sh. boydii (10%) and Sh. sonnei (5%). All or most of the strains were susceptible to cephalothin, gentamicin, kanamycin, polymyxin B and trimetho-primsulphamethoxazole. Frequencies of susceptibility to ampicillin, carbenicillin and chloramphenicol were, respectively, 79, 80 and 75%. Only 37, 23 and 58% were susceptible to streptomycin, sulphadiazine and tetracycline, respectively.

Resistance to one or more drugs was detected in 85 % while 72 % were multiply resistant. There were 24 different resistance patterns, varying from resistance to one drug to resistance to seven drugs.

The findings have been compared with reports from other countries. This study and several others cited support the view that trimethoprim-sulphamethoxazole is the best alternative drug for treatment of shigellosis particularly in regions with multiple drug-resistant strains.

The microbiological quality of eight halogenated and two u.v.-treated hydrotherapy pools in hospitals was investigated. The microbiological quality of halogenated hydrotherapy pools was comparable to halogenated public swimming pools, although in some Pseudomonas aeruginosa and faecal pollution indicators were more frequent due to bad management.

On the other hand u.v.-treated hydrotherapy pools had very bad microbiological quality. Apart from faecal pollution indicators, P. aeruginosa was present in very high numbers.

Halogenated hydrotherapy pools were not highly contaminated with amoebae, and Naegleria spp. were never detected. On the other hand u.v.-treated pools contained very high numbers of thermophilic Naegleria. The Naegleria isolates were identified as N. lovaniensis, a species commonly found in association with N. fowleri.

Isoenzyme analysis showed a different type of N. lovaniensis was present in each of two u.v.-treated pools.

Nasal swabs were taken from 369 four-year-old children in two South Wales towns and cultured for Streptococcus pneumoniae. The organism was isolated in 34% of the specimens, similar rates being found in boys and girls in the two towns. The children were swabbed again a year later, when the prevalence of nasal pneumococci had fallen to 25%. There was no association between the presence of the organism on the two occasions. Types 6 and 23 were most often isolated. After excluding children who had received an antibiotic, the proportion carrying a pneumococcus was higher in those who had recently had a respiratory infection than in the rest, although the difference was not quite statistically significant. There was a significant negative association between the presence of Staphylococcus aureus and Strep. pneumoniae.

Nasal carriage of Staphylococcus aureus was studied in a cohort of infants born to the residents of two towns in South Wales. The children were followed up to the age of 5 years, nasal swabs being taken annually after a more detailed survey during the first year. The carriage-rate of S. aureus reached a minimum of 10–15% at one year and then rose steadily to 41% at five years. From the age of two years about 90% of the organisms isolated were resistant to penicillin. There was a marked tendency for children to carry the same strains from year to year, but carriage during the first year of life did not predict carriage at the age of five.

A number of scombrotoxin poisoning incidents which have recently occurred in the UK following the consumption of canned fish have been investigated. Symptoms are described and the relationship between the histamine content of incriminated samples and toxicity is discussed.