A standard technique for ascertaining the survival characteristics of bacteria after being environmentally stressed is to incubate the bacteria on both selective and non-selective media and count the colonies produced. Based on these colony counts, indexes of injury and persistence of the bacteria are calculated. To compare the stress of two different environments, a persistence ratio is calculated. In this paper, methods of statistical inference concerning these indexes and ratios are presented. These statistical methods use well-known procedures for analysis of binomial data and 2 × 2 table data, and are appropriate when the colony counts follow a Poisson distribution.

The role of viruses and M. pneumoniae in episodes of acute respiratory illness in childhood has been studied in a London general practice. The total isolation rate was 31·7%, but the rate varied from 32·6% in upper respiratory infections to 64·0% in pneumonia. The clinical features associated with infection were influenced not only by the type of agent but also by age and other host factors in the infected children. Rhinoviruses were more commonly isolated than any other agent and were frequently associated with wheezy bronchitis.

The response to passive cutaneous anaphylaxis, dermal hypersensitivity and intravenous provocation tests has been compared in 30, 40, 31 and 24 cattle injected with foot-and-mouth disease vaccine 0, 1, 2 and 3 times respectively, using vaccine components and other substances as test materials. Reaginic antibodies, demonstrated by passive cutaneous anaphylaxis in goats, were directed against BHK 21 cell extracts (20), hydroxypropylmethylcellulose (3) and an unidentified vaccine component (3), and distributed in 0, 5, 19 and 75% of the cattle vaccinated 0, 1, 2 and 3 times. None of the animals showed clinical signs of allergy after vaccination. When BHK 21 cell extract was injected intradermally a significant correlation was noted between the development of large weals and the presence of reagins although the size of the weals was not correlated with the reagin titres. In the case of hydroxypropylmethylcellulose a similar trend was evident. The majority of cattle with large dermal weals possessed reagins but the number of reactions was too small for statistical evaluation. Dermal reactions to sodium penicillin, sodium carboxymethylcellulose, saponin and whole vaccine occurred in both unvaccinated and vaccinated cattle but BHK 21 cell lysate and normal bovine serum provoked weals which increased in frequency according to the number of vaccinations experienced. Intravenous hydroxypropylmethylcellulose elicited a response in all the animals previously injected with certain batches of vaccine but none in those injected with other batches or in unvaccinated controls. BHK 21 cell extract intravenously produced a clinical response in half the tested animals which was uncorrelated with the results of the passive cutaneous anaphylaxis or dermal hypersensitivity tests.

Results are presented of the laboratory examination of faeces specimens from 20,273 patients with acute diarrhoea. These were household index cases seen in general practice in a London borough during the years 1953–68. An annual average of about 2% of households in the area were affected, but there was considerable fluctuation with year and season. Half the patients were children although only one-fifth of the population at risk was under 15 years of age. The greatest incidence of diarrhoea was among children under 5 years old. Male children, but female adults predominated.

Specimens were sent for laboratory diagnosis at the discretion of the general practitioner. The laboratory found some abnormality in nearly a third and there were indications that transmissible infection was involved in about one-fifth of patients. The most common diagnosis was Sonne dysentery (9%) which came in epidemic waves and made its greatest impact among young school children. Microscopy was useful, and giardiasis was diagnosed in 1·4% of index patients. Other parasites were less commonly found. Fatty globules characteristic of an infectious condition we have called ‘fatty diarrhoea’ were frequently observed by microscopy in stools from young children and occasionally from older persons. Blood or pus cells were seen in less than half the shigella and salmonella infections and in a much smaller proportion of the remainder. A test for occult blood performed on specimens from all patients of 40 years or older was positive, in the absence of visible red cells, in a tenth of these cases.

Other studies on the bacteriology of diarrhoea in general practice are referred to and some epidemiological comparisons made. The possible place of unidentified infective agents in the aetiology of undiagnosed diarrhoeas and of ‘fatty diarrhoea’ is discussed.

Outbreaks of salmonellosis caused by serotypes other than S. dublin and S. typhimurium were investigated on 41 farms in north-west England. Of these, 37 (90%) were in dairy cows. There was strong circumstantial evidence that contaminated dairy cake was the source of infection in at least four herds and probably many more. Twenty-six serotypes were encountered with S. newport, the commonest, causing the most severe disease. Most cattle seemed to rid themselves of infection during the following months whether or not they were at pasture, housed in cubicles or in byres. Some cows excreted salmonellas for up to 11 months after the disease outbreak. Associated human salmonellosis was confirmed on 3/41 (7%) of the farms.

A total of 50 duplicate Moore swabs were placed for 2 days, on five different dates, in 9–12 points of the Athens sewage disposal system.

Three methods of enrichment were used for the isolation of salmonellas. In the first method, one half of the duplicate swabs was incubated in Muller–Kauffmann's tetrathionate broth at 43° C. for one day. For the second method, a secondary enrichment was carried out in Rappaport's broth, made from the Muller–Kauffmann's broth and for the third method, the other half of the duplicate swab was cultured in Heart Infusion broth at 43° C. for 16–18 hr. after which a secondary enrichment was made in Rappaport's medium.

By use of these 3 enrichment procedures, 96% of the swabs were found to be positive for salmonellas. A total of 178 strains were isolated (an average of 3·7 strains per positive swab), belonging to 53 different serotypes (an average of 1·1 different serotypes per positive swab).

With the simple enrichment in Muller–Kauffmann's broth, only 72% of the swabs were found positive, and 68 strains of salmonellas belonging to 30 different serotypes were isolated. The secondary enrichment in Rappaport's medium made from the Muller–Kauffmann's broth produced 88% positive samples, and yielded 82 strains belonging to 34 different serotypes. Finally, with the secondary enrichment in Rappaport's broth made from the heart infusion broth, 92% of the swabs were positive and yielded 67 strains of salmonellas belonging to 27 different serotypes.

Although the last procedure yielded the greatest number of positive swabs, the method involving secondary enrichment in Rappaport's broth made from Muller–Kauffmann's broth led to the isolation of the greatest number of strains and different serotypes, while the other two procedures were approximately equal in this respect.

Of the 178 strains isolated, 110 were recovered only by the procedures involving secondary enrichment in Rappaport's broth. The most frequently isolated serotypes were Salmonella senftenberg (33 strains), S.typhimurium including var-copenhagen (18 strains), S.poona (11 strains), S.montevideo (10 strains), etc. The following 23 serotypes were isolated for the first time in Greece: S. adelaide, S. alachua, S. allerton, S. binza, S. bobo, S. butantan, S. gnesta, S. goelzau, S. haelsingborg, S. havana, S. hofit, S. ibadan, S. indiana, S. irumu, S. jodhpur, S. nienstedten, S. panama, S. pomona, S. poona, S. reading, S. schwarzengrund, S. stockholm, S. tournai. Moreover, a new serotype, S. athinai was described.

Two FMDV strains which had been previously differentiated by complement-fixation were compared by guinea-pig protection test, kinetic neutralization and micro-neutralization tests. It was found that these tests, which have not been previously applied by the methods described, were all capable of FMDV strain differentiation. Similar differences were found by all methods, which suggests that comparisons made by cross-CF, cross-neutralization or cross-protection involve measurement of the same antigen/antibody interactions.

Sixteen foot-and-mouth disease virus (FMDV) strains of type SAT 1 were compared in complement-fixation tests. With the test used, the range of antigenic variation within a type appeared to be greater than previously described. The concept of a sub-type group within which all strains are more closely related to each other than to any strain outside the group was not supported. Considering the group of strains studied, it is suggested that the classification of strains is best achieved by nominating a reference strain for each sub-type. Others are classified as related strains in one or more sub-type groups according to their relationships with the reference strains.

Animal experiments have shown that respiratory administration of pertussis antigen induces a protective immune response. In this study pertussis antibody in human respiratory secretions was measured and the response to aerosol and intramuscular pertussis immunization investigated. Substantial increases in this antibody occurred after aerosol immunization but no changes were found in serum antibody. The reverse was observed after intramuscular immunization. Severe side effects are frequently seen after intramuscular pertussis vaccine in adults but not with aerosol immunization. The latter method may be of value for paediatric medical and nursing personnel exposed to the risk of pertussis infection.

A method for typing ECHO and Coxsackie B viruses using counter-electrophoresis has been developed using stock strains of 15 different ECHO types and 5 Coxsackie B viruses. Work is continuing to see whether the method is a practical one to use for typing of strains from patients infected with ECHO or Coxsackie B viruses.

After experimental inoculation of Cytoecetes ondiri, the agent of bovine petechial fever (BPF), multiplication occurred in impala, bushbuck, Thomson's gazelles and wildebeest, as shown by infectivity studies and clinical findings. Similar attempts to infect one eland failed.

As a sequel to this, blood and spleen samples were collected from four species of wild ruminants in an area where BPF was endemic. Isolations of C. ondiri were made from three of five bushbuck, but not from any other species.

A comparison was made of the antibody response and subjective reactions to zonally-purified influenza vaccine in aqueous suspension and in peanut oil adjuvant 65-4. Both preparations contained 700 CCA units of A/Aichi/2/68, and 300 CCA units of B/Mass/1/71.

Subjective reactions were recorded by asking the volunteers to complete a record daily for 5 days. Pain at the injection site was recorded by 64% of the recipients of the oil adjuvant vaccine compared with 35% of the aqueous recipients, but local redness was more frequent after aqueous vaccine. Systemic symptoms were recorded a little more frequently after aqueous than oil adjuvant vaccine.

When measured 7½ weeks after a single dose of vaccine, the HAI geometric mean antibody titre (G.M.T.) to the A/Hong Kong/1/68 antigen (antigenically similar to the A/Aichi/2/68 antigen in the vaccine) increased 2·7-fold after aqueous and 16·4-fold after adjuvant vaccine. Sixty-two weeks after vaccination the antibody titres remained higher in those given adjuvant vaccine. The G.M.T. to B/Mass/1/71 increased 1·9-fold 7½ weeks after aqueous vaccine and 3·7-fold after adjuvant vaccine.

The antibody response to both influenza A and B antigens was broader in the recipients of adjuvant vaccine. The G.M.T. to A/England/42/72 increased 2·8-fold after aqueous and 13-fold after adjuvant vaccine; and to B/England/847/73 it increased 1·3-fold after aqueous and 1·9-fold after adjuvant vaccine.

Most normal bovine whey samples contain a fraction that survives heating at 56° C. for 30 min., passes through a dialysis membrane and kills a maximum of seven out of ten of the different bovine mycoplasma species tested. Some whey samples appear more active than others but not all affect the same strains of mycoplasma indicating some specificity in their action. Absorption of the active factor from whey by heterologous and homologous mycoplasmas and by erythrocytes was observed. Binding of the factor to mycoplasmas appears to be temperature-dependent and non-specific, but subsequent mycoplasmacidal action shows some specificity.

Cattle and pig herds and flocks of domestic fowl have formed the main reservoir of human salmonella food poisoning in England and Wales from 1941 to 1972.

Changes in the incidence of human salmonella food poisoning and in the serotypes of salmonellas isolated from human infections are shown to have been associated with the introduction of new foods, with changes in animal husbandry, and with changes in the relative proportions of flesh food from different species consumed. New foods, dried powdered egg, liquid egg and frozen liquid egg were introduced during the period of food rationing which extended from 1940 to 1953. Changes in animal husbandry, in particular the intensive production of pigs, poultry and eggs, followed the re-establishment of pig herds and fowl flocks after the derationing of animal feed in 1953. The changes in the proportions of flesh foods consumed followed the introduction of frozen oven-ready fowl in the late 1950s and early 1960s which by 1964 became cheaper than traditional flesh foods.

A total of 292 children's sera and 706 antenatal sera from different parts of England were tested for the presence of poliovirus neutralizing antibodies. Little variation was found between different areas and types of community, but a lower proportion of the 5–14 year old children had antibody than younger children and young adult women. The proportion of the young population with antibody, and the current acceptance rates for oral poliovirus vaccine are barely satisfactory.

Transferable chloramphenicol resistance has become common in the typhoid bacillus in countries such as Mexico, India, Vietnam and Thailand. Situations such as this, and others analogous to it in many parts of the world, are the result of the long-term indiscriminate use of chloramphenicol and other antibiotics in the affected areas. They can be rectified only by more rational antibiotic usage.