Because of the paucity of quantitative data on numbers of other enteric pathogens in food, the reliability of the examination of processed foods for Enterobacteriaceae was estimated taking Salmonella as a model. For this purpose an assessment was carried out of the risk of accepting Salmonella contaminated consignments of foods, despite a negative outcome of (i) examination of 1·5 kg samples for Salmonella; (ii) examination of one or two 1 g samples for Enterobacteriaceae; (iii) simultaneous application of both tests. The computations were based on the results of the examination of 6830 samples of dried foods, processed for safety, out of a total of 18170 samples.

Only 69 samples permitted the exact calculation of the factor, defined as c.f.u./g of Enterobacteriaceae/c.f.u./g of Salmonella; 4642 were positive for the former group but ‘free’ from Salmonella, and the rest were negative in both tests. Numbers of c.f.u./g for both groups, and hence the factors, varied widely between commodities and also between different consignments of the same food product. The average for amounted to 5·8 × 103, far from the base-line value of 0·75 × 103 assessed earlier. In only 0·1% of samples did the Enterobacteriaceae test fail to achieve the required consumer protection.

This investigation therefore substantiates that testing foods processed for safety by examining accurately chosen quantities for ecologically well selected and taxonomically thoroughly defined index organisms is a most effective procedure in terms both of consumer protection and simplicity of examination without compelling the food industry to achieve hardly attainable microbiological quality standards.

Tuberculin testing of 176 personnel in a Liverpool hospital showed a total incidence of 68 % negative reactors. This remarkably high percentage was similar for each of the various groups of workers tested. We did not find the Tine test to be a satisfactory method of screening for tuberculin sensitivity because 30% were doubtful reactors. In these, further tuberculin testing by the Mantoux reagent was always positive.

Four hundred and seventy tuberculosis patients were each skin tested with four of a range of 17 mycobacterial reagents in four countries in all of which tuberculosis and leprosy were endemic. Sixteen of the reagents were new tuberculins prepared from extracts of living mycobacteria disrupted by ultrasonic disintegration and the last was PPD, RT23.

The effect that tuberculosis exerted on the delayed-type skin test response to these antigens was assessed by comparing results for tuberculosis patients with those for Tuberculin positive and Tuberculin negative control populations. Tuberculosis patients on Rifampicin therapy showed no difference in their skin test responses to any of the antigens from those patients on other forms of anti-tuberculosis treatment.

Amongst the normal population it was found that possession of Tuberculin positivity was associated with an enhanced response to all the other mycobacterial antigens with the exception of A*-in which demonstrated a reciprocal relationship with Tuberculin in Burma. It was also noted, in Burma particularly, that sensitization to mycobacterial species other than Mycobacterium tuberculosis, especially to the slow growers, plays a role in determining responses to different mycobacterial species.

In tuberculosis patients enhanced skin test responses were also seen but only in those countries, e.g. Libya, where the prevalence of mycobacterial species was low. Where mycobacteria were common, as in Burma, the converse was true and tuberculosis was associated with a diminished skin test response to each antigen. The high prevalence of A*-in positivity in Burma, its reciprocal relationship with Tuberculin there and the results for all the antigens in the tuberculosis patients indicate that the cell mediated skin test response may have a threshold. If this is exceeded the skin test becomes negative so that non-reactors then include those who have been excessively sensitized as well as those who have not been sensitized. Despite this, a greater percentage of tuberculosis patients in each country responded to the specific reagent Tuberculin than did the control populations and their mean positive induration sizes were consistently larger. Nevertheless, amongst the tuberculosis patients in Burma 13% were complete non-reactors to Tuberculim and this apparent anergy also applied to the other reagents with which these individuals were tested.

This differs from lepromatous leprosy where the anergic state pertain exclusively to M. leprae and a few seemingly closely related species. The breadth of anergy in M. ulcerans infection has not been measured but it is known to effect both Burulin and the PPD, RT23.

Just as in leprosy and M. ulcerans infection, tuberculosis can be shown to have a disease spectrum here detected by multiple skin testing. The significance of this spectrum and its similarities with and differences from that of the other mycobacterioses is discussed.

A simple method of breeding large numbers of rabbit fleas in a rabbit house with minimal disruption to the general routine is described.

Group-A streptococci belonging to opacity-factor (OF)-positive M types were poorly haemolytic on horse-blood agar, but members of OF-negative M types, and M-negative variants of OF-positive strains gave good haemolysis. Horse-serum extracts of strains of OF-negative serotypes 6 and 12, and M-negative variant cultures of OF-positive serotypes 4 and 49, had higher titres of streptolysin S than did similar extracts of OF-positive, M-positive cultures of types 4 and 49. However, much larger amounts of streptolysin S could be extracted with ribonuclease (RNAase)-digested yeast ribonucleic acid (RNA) and M-positive OF-positive cultures treated in this way gave extracts at least as strong as did their M-negative variants or the OF-negative strains. Extraction of streptolysin S from OF-negative strains by serum could be inhibited by previous incubation of the serum with extracellular OF, suggesting that the production of diffusable OF by M-positive variants of OF-positive serotypes interferes with the extraction of streptolysin S by serum and leads to poor haemolysis on blood agar.

The haemolysis of all strains on blood agar was greatly improved by the incorporation of 0·1% (w/v) RNAase-digested yeast RNA into the medium, but the improvement was most marked in OF-positive serotypes.

A controlled trial of influenza vaccines in a boys' public school from November 1970 to October 1975 provided an opportunity to study the response to vaccine and the effect on subsequent natural challenge in boys with differing natural experience of influenza A strains. The response to influenza A (H3N2) vaccines was assessed by estimating homotypic and heterotypic antibodies to the surface antigens. Previous natural experience of influenza A was found to influence vaccine response and the effect of natural challenge. The antibody response to revaccination with the same strain showed a progressively poorer response to second and third doses. The protective effect of naturally acquired and vaccine-induced antibodies was assessed during two outbreaks of influenza A which occurred in the trial period.

A microbiological investigation of Black infants suffering from severe acute summer gastroenteritis revealed enteropathogenic agents in 30 out of 37 patients (81%). Enterotoxigenic bacteria were isolated from 15 patients (41%). A total of 16 enterotoxigenic strains were isolated, comprising 9 enterotoxigenic Escherichia coli strains secreting labile and stable toxin on their own and in combination, and labile-toxin secreting strains of Klebsiella pneumoniae (4), Enterobacter cloacae (2) and Proteus vulgaris (1). In the case of the latter three species, however, 6 out of the 7 strains were isolated from patients who were excreting other enteric pathogens, whereas only 2 out of 9 enterotoxigenic E. coli patients had concomitant infections with other pathogens. No invasive bacteria were isolated except for 2 shigella strains. Salmonella and shigella strains were found in four patients. No correlation was found between the enteropathogenicity of E. coli and its serotype. Rotavirus was observed by negative staining electron microscopy in only two patients (6%) but using a reverse complement fixation test rotavirus antigen was detected in the stool of 17 out of 35 patients (49%). The low EM detection rate may well be due to the patients being admitted for treatment late in the course of their illness when the degree of viral shedding has decreased below EM detectability. No significant difference in clinical presentation was noted between the various aetiological agents. Only one patient was being solely breast-fed compared to 16% of control non-diarrhoeic infants. Evidence of malnutrition was noted in over half of our patients.

One hundred and thirty-three vanilla slices, purchased from shops in the West Yorkshire Metropolitan County, were examined to determine the numbers and types of bacteria present at the time of purchase. The surface colony count at 37 °C was > 103/g in 67/133 (50%) of the samples examined, Bacillus cereus being found at that concentration in 21·8%, coliform bacilli including E. coli in 5·3%, Staphylococcus aureus in 3·0% and Streptococcus faecalis in 0·8%. Thirty-four strains of B. cereus were serotyped and 11 (32%) of these were typable with the sera available.

Preparation of custard mixes in the laboratory suggests that the milk or milk powder used in the mix may be the major source of B. cereus in the final product. Many of the present methods of manufacture, distribution and storage allow organisms present in the custard at manufacture the opportunity to multiply and possibly reach numbers which present a risk of food poisoning.

Saturation diving is an important and widely used technique in the Offshore Oil Industry. During 1974–5 two saturation dives in the North Sea were terminated because of outbreaks of incapacitating otitis externa, and others were disrupted. Pseudomonas aeruginosa was consistently isolated from the ears of affected divers. Because complex work schedules were threatened seven subsequent dives were subjected to microbiological monitoring and control. Colonization of the ear canal with P. aeruginosa or with other gram-negative bacilli occurred in 39 (67%) of the 58 divers studied, usually within 7 days of starting the dive. Data obtained by serotyping the isolations of P. aeruginosa suggested that a single infected diver may be the source of organisms which rapidly spread to his colleagues and throughout the living chambers, that the living chambers may constitute a reservoir of infection during and between dives, and that certain serotypes of P. aeruginosa are more likely than others to colonize the ear canal in the conditions of a saturation dive. The control measures used during the dives were only partially effective, but none of the divers suffered severe pain and all the dives were an operational success.

RSV complement fixation antibodies were established in 200 paired maternal and cord blood sera. Geometric mean titres in cord sera were significantly higher than in maternal sera. The differences did not depend on the virus strain used. Half of the paired sera (taken at random) were also submitted to microneutralization tests. No differences were found between geometric mean titres in maternal and cord sera.

Rubella haemagglutination inhibiting (HAI) antibody titres were determined in 54 seronegative women and 31 naturally immune women after vaccination and revaccination with Wistar RA27/3 strain rubella vaccine administered by the intranasal or subcutaneous routes or revaccination with the Cendehill strain administered subcutaneously. In addition, HAI antibody titres were determined in 46 seronegative schoolgirls after vaccination with the Cendehill strain and revaccination with the RA27/3 strain.

All seronegative women vaccinated with the RA27/3 strain developed antibody, peak titres being reached 6 weeks after vaccination. Six months after vaccination with the Cendehill strain, 45 (98%) of the 46 seronegative girls had developed antibody, but 11 (24%) had not reached their peak titre by 6 weeks, suggesting a slower response than that elicited by the RA27/3 strain. Revaccination did not induce significant antibody responses in the seronegative women vaccinated 6 months previously with RA27/3 but 4 naturally immune women developed an eightfold increase in antibody. In 10 (22%) of 46 schoolgirls previously vaccinated with the Cendehill strain a significant rise in antibody followed revaccination with RA27/3. These results provide further evidence of the more rapid antibody responses elicited by the RA27/3 vaccine in comparison with the Cendehill vaccine.

An outbreak of natural rubella occurred in 1972 and 97 cases were confirmed serologically. The clinical disease was more common in older school-children and in adults. More males than females were affected in the 11–15 age group, the sex ratio being 18:12; this may be explained by the routine vaccination of girls of this age group as part of the national programme which began in 1970. The significance of the persistence of high HAI antibody titres after natural infection and the effect of the epidemic on the serological status of the population are discussed.

A comparison of homologous and heterologous rates of neutralization demonstrated that antigenic relationships of foot-and-mouth disease virus strains could be differentiated quantitatively by the kinetics of neutralization method described previously (Rweyemamu, Booth & Pay, 1977). Conventional formulae for r, R and D values could be applied to results obtained by this method. It was demonstrated that results analysed this way gave R values which were similar to those obtained with other neutralization test methods but which were generally smaller than those obtained with complement fixation test results. It was demonstrated that there were wide differences between the vaccine strains tested as demonstrated by R value relationships. An examination of r values, however, demonstrated that antisera to the Moz 1/70 strain were highly reactive with most of the virus strains from Central and Southern Africa. The selection of FMD virus strains with a wide serological range for vaccine production is discussed.

Between 1968 and 1975, well over 3000 samples of pig faeces and 407 samples of pig mesenteric glands were examined for salmonellas. A very wide range of serotypes was isolated. The material from this survey was used to evaluate certain aspects of salmonella isolations. The factors studied were: selective motility enrichment, size of inoculum of faeces, comparison of drain swab with animal sample and comparison of selenite F broth with Muller–Kauffmann tetrathionate broth. The conclusions drawn from these investigations allowed an efficient routine to be developed during the survey.