The isolation and description of Bacillus coli commune by Escherich a hundred years ago marked the start of a series of scientific investigations which have led to some of the most important discoveries in microbial pathogenicity and genetics that have been made since that time. It is not difficult to find the reasons why so much effort has been concentrated on this organism. Escherichia coli is present in the gut of all warm-blooded animals generally forming the predominant aerobic flora; it is of medical and veterinary importance being responsible for a variety of infections in the human and animal populations and it has provided a useful tool for geneticists.

Ever since Escherich (1885) first isolated the organism now known as Escherichia coli from the stools of infants, medical microbiologists have been faced with the problem of distinguishing between those strains capable of causing diarrhoea and those that are harmless gut commensals. Epidemiological investigations were greatly facilitated by the description by Kauffmann (1947) of a serotyping scheme for E. coli, and Taylor (1961) later reported that 17 0 serogroups of E. coli had been implicated as possible causes of epidemic infantile enteritis. These infantile enteropathogenic E. coli (EPEC), having been discovered by epidemiological studies using serotyping, belonged by definition to a restricted range of serogroups. More recently it was shown that other E. coli strains may produce enterotoxins, and these enterotoxigenic E. coli (ETEC) usually belong to particular serogroups which are different from those associated with EPEC. E. coli strains belonging to a third range of serogroups may cause an illness resembling shigella dysentery, and these may be regarded as entero-invasive E. coli (EIEC). E. coli strains that cause diarrhoea may therefore be considered as three groups, as follows.

When Theodor Escherich (1885a, b) first described Escherichia coli he looked on it as a saprophytic organism. Soon several investigators found that colibacteria could be isolated from intestinal infections and from many infections outside the intestine, like urinary tract infections (UTI), cholecystitis, wound infections, meningitis, septicaemia, pulmonary infections, and many more. Uhlenhuth (1897) showed that coli strains from pathological processes were more pathogenic in animal experiments than strains isolated from the normal intestine. Smith (1927), who examined strains from white scours in calves, showed that spontaneous acapsular mutants could be obtained from certain colibacteria, and that such mutants were less virulent when injected intra-peritoneally into guinea-pigs.

It has been known for a considerable time that Escherichia coli, although a normal inhabitant of the intestinal tract, can also be associated with a variety of pathological conditions in man, farm animals and poultry.

When Escherich (1885) isolated from the faeces of a newborn baby an organism which is now accepted as E. coli, he considered it to be a harmless saprophyte. Laruelle (1889) was the first to suggest the possible pathogenicity of this organism, while Jensen (1893) showed that it was the cause of white scour in calves. The development of reliable serological methods facilitated the differentiation of strains and numerous workers have demonstrated an association between certain serological types of E. coli and various disease conditions in animals. Enteric diseases in young animals are an important cause of mortality and economic loss to the farming community.

It is possible to differentiate isolates of Escherichia coli using a number of techniques including the determination of the serotype, biotype and phage type and the profiles for resistance to antibacterial agents and toxic chemicals, intracellular enzymes, outer membrane proteins and plasmids and the production of enterotoxin and colicines. These methods have been used principally for the study of pathogenic E. coli and plasmid-mediated drug resistance. However they can also be used successfully for ecological purposes and the application of several of these techniques for the study of the ecology of E. coli in healthy young animals including man is described.

The study of Escherichia coli and its plasmids and bacteriophages has provided a vast body of genetical information, much of it relevant to the whole of biology. This was true even before the development of the new techniques, for cloning and analysing DNA, that have revolutionized biological research during the past decade. Thousands of millions of dollars are now invested in industrial uses of these techniques, which all depend on discoveries made in the course of academic research on E. coli. Much of the background of knowledge necessary for the cloning and expression of genetically engineered information, as well as the techniques themselves, came from work with this organism.

Seventy-five strains of Mycobacterium fortuitum were inhibited by 3·0 mg/1 ciprofloxacin but 36 strains of M. chelonei were resistant. The results correlated well with those obtained by the nitratase test. The ciprofloxin sensitivity test is a useful supplement to the tests used to identify these two species.

The efficacy of flocoumafen, a novel anticoagulant rodentide, was evaluated in feeding tests on confined and free-living populations of house mice (Mus musculus L.). In four pen trials, family groups of laboratory-reared wild mice were conditioned to feeding on plain foods and then offered flocoumafen at 0.005% in pinhead oatmeal bait. All 68 mice, comprising juvenile and adult animals, died within 10 days.

Ten field trials were carried out, using the same formulated poison bait, against mice infesting farm buildings. Mean treatment success, estimated from live-capture and mortality data, ranged between 87–1 and 100%.

The performance of flocoumafen is compared with that of difenacoum, bromadiolone and brodifacoum used at the same concentration in oatmeal bait. Flocoumafen gave an equally effective but quicker kill of mice. It is concluded that flocoumafen is a promising new rodenticide for the control of M. musculus.

The results of examinations of stools for Bacillus cereus among three unrelated groups of individuals are presented. The groups consisted of (1) healthy schoolchildren aged 6–11 years in a rural region of South Africa examined during each of the four seasons of the year; (2) 15 healthy volunteers comprising staff of a London microbiology laboratory and their families examined on each of 3 consecutive weeks; (3) 75 unrelated young children, 2 months to 5 years of age, in a second rural region of South Africa examined during a pilot study of 1 week's duration on the aetiology of rural gastroenteritis. The stools of the last group were submitted as being related to present or recent diarrhoea in the respective children.

In group 1, B. cereus isolation rates ranged from 24·3% at the autumn visit to 43% at the summer visit with a significantly higher rate of isolation in the summer than at other seasons of the year (P <0·05). B. cereus was isolated from 40% of group 2 volunteers on week 1, none on week 2 and 20% on week 3. The organism was detected in the 12 positive specimens at levels of approximately 102/g and constituted 2·5–30% of the total aerobic spore-forming bacillus population in the stools. In group 3, B. cereuswas recovered from 18·7% of the stool samples and was isolated consecutively with other pathogens (entcropathogenic Escherichia coli and rotavirus) on only five occasions. In groups 1 and 3, < 5% of the stools had ‘3+ ‘levels of B. cereus(> 10 colonies per direct plate culture).

B. cereus was readily isolated from all of 10 food samples, representative of the typical diet of the group 1 individuals, and was present in substantial numbers (104 to 5·5 × 106/g) in half of them.

The isolation results, supported by serotyping, indicated that carriage of B. cereusin stools is transient and its presence at any one time reflects solely its intake with foods.

At least 12 persons contracted clinical, and 4 persons subclinical Brucella melitensis infection during a brucellosis epidemic in the spring and summer of 1983 in Southern Germany, a region which had been free of this disease for the past 20 years. All cases of illness were traced to one infected herd of sheep. The presence of antibodies against B. melitensis was examined in 72 sera of infected patients using the following tests: agglutination, Coomb's test, two complement fixation tests with different antigen preparations (CFT 1 and 2), IgG and IgM enzyme-linked immunosorbent assay (ELISA), and opsonophagocytosis; and the occurrence of cross-reacting antibodies against Yersinia enterocolitca O9 was investigated in the agglutination and complement fixation tests. Sera from 100 blood donors and 112 other people with close contact with sheep were also examined. The results revealed the need to consider an intermediate range in the interpretation of ELISA results – due to elevated values of persons in groups at risk but without clinical signs of illness. In all other tests, however, such persons revealed the same cut-off levels as the general population. Results from all initial sera of infected persons revealed titres of optical densities above the baseline levels determined in the present study, with the exception of the Coomb's and CFT 2 tests. The agglutination test, but not brucella CFT2, revealed complete cross-reactivity between Y. enterocolitica O9 and B. melitensis. ELISA stood out as the only test which is suited to diagnosis of both recent and past infection, since ELISA IgM determination permits conclusions about the time of the onset of illness, and determination of IgG may still yield values above the cut-off level up to G23 days after the onset of illness. In 2 of the 1G infected persons, IgG ELISA was the only test revealing previous infection 424 and 528 days after the onset of illness. A procedural scheme is presented which may help to simplify the diagnosis of brucellosis.

During an average follow-up time of about 2½ years after total hip or knee-joint replacement in 8052 patients, suspected joint infection was recorded in 85 patients whose joints had not been re-operated during that period. The hospital records of 72 of these patients were examined after a further period, averaging about 5 years. Thirty-five of these had suffered continuing major problems with the joint, 18 of which had been revised, and a further 9 joints needed such treatment. Infection was confirmed in 17 of the 35. These numbers are proportionately about three times greater than those observed among a set of matched controls followed-up for a similar period. The evidence from the extended follow-up suggests that the failure rate, unassociated with infection, reached about 5% by 7 years after operation and that late infections, manifested between about 2½ and 7 years after operation, were about as frequent as those confirmed during the first 2½ years.

Two hundred and sixty-nine Staphylococcus aureus cultures isolated from bovine milk were subjected to phagc typing using the International basic set of 16 phages at Routine Test Dilution. In the current study 73·6% of cultures were ‘typable’ compared with 84–89% in 1972 when the set was first recommended. The set remains capable of typing the majority of bovine staphylococci but shows a reduction in lysogenicity of most of its phages.

An outbreak of streptococcal throat infection which took place in a preparatory school for boys (some of whom were choristers) over three terms from November 1983 to June 1984 is described. Typing of the organism revealed that four successive outbreaks, each due to a different type, had occurred. Thirty-nine per cent of the boys were affected, the incidence of infection being higher among boarders than day boys. Infection seemed to spread via the forms, dormitories and choir. Recurrent attacks occurred in 32% of infected boys. The complication rate was 8%. Treatment with penicillin was always effective but did not prevent reinfection. Suggestions for the management of an outbreak of sore throat in a school are given.

In Alice Springs and its vicinity, a single nasal swab was collected from 282 Australian aborigines in May 1981 to determine nasal carriage rates of pneumococci. Each swab was inoculated on blood agar and on gentamicin blood agar. The carriage rates were 89% in children, 39% in adolescents and 34% in adults. In all, 27 serotypes of pneumococci were met with and 15 (4%) of subjects yielded two or more serotypes. In children, types 23, 19, 6, 22 and 6 were predominant (in that order), whereas type 3 was commonest in older subjects. Approximately 25% children and 5% adults yielded drug-insensitive pneumococci. Resistance to benzylpenicillin, tetracycline and co-trimoxazole was met with, resistant pneumococci showed five resistance patterns and belonged to nine serotypes, predominantly types 19 and 23. All isolates were sensitive to chloramphenicol, erythromycin, lincomycin and rifampicin. The carriage rate of drug-insensitive pneumococci was 100-fold higher amongst children sampled than in non-aboriginal children in Australia.

Strains of Staphylococcus aureus isolated from shrimp were examined for phage pattern and enterotoxin production; 63% of the strains isolated from North Sea shrimp were typable with the International and additional set of phages, as were 38% of the strains isolated from South-East Asian shrimp. Staphylococcal enterotoxin(s) (SE) were produced by 48% and 35% of strains isolated from North Sea and South-East Asian shrimp respectively. Growth and enterotoxin production by S. aureus in shrimp was examined in storage experiments at 22 °C. S. aureus increased by 1–2 log units in 24 h when the organism was only a minor part of the total microflora of shrimp. When S. aureus was an equivalent part of the total flora its numbers increased by 3–4 log units in 24 h. Enterotoxins A and B became detectable when the number of S. aureus exceeded 107 per g in aseptically peeled shrimp. Results indicate that S. aureus is able to produce enterotoxin in shrimp, but its production depends upon a number of factors, including the relationship between S. aureus and competitive micro-organisms. It is concluded that the presence of S. aureus on commercially produced shrimp represents a potential hazard to health.

Laboratory studies were performed on 128 children clinically diagnosed as measles when seen at the Infectious Diseases Hospital, Kenyatta National Hospital (IDH), Nairobi (86 cases) and the Rural Health Training Centre, Maragua, Central Province (42 cases) between 9 July and 31 August 1984. A concurrent measles infection was confirmed in 95% of the children seen at IDH and in 85% of those seen at Maragua, with similar proportions of confirmations in children who had, and who had not, received measles vaccine. No differences in the number of sero-conversions nor in the absolute levels of acute or convalescent HI antibody titres could be detected between vaccinated and unvaccinated children. Analysis of the cases seen at Maragua indicates that about two thirds of the children who had received vaccine were protected. A pilot study of vaccinating children at 8 months and again at 12–13 months is suggested in an attempt to eradicate measles.

Studies were made on 33 immunocompetent patients with cryptosporidiosis (31 of them children) to determine how long oocyst shedding continued after the cessation of diarrhoea. The majority (20/33) ceased to shed oocysts in the week following the cessation of diarrhoea. However 5 patients (15%) continued to shed oocysts for 2 weeks or more, and 1 patient was still shedding oocysts when lost to follow-up 3 weeks after the diarrhoea ceased.

There was considerable variation among patients, and some eliminated oocysts more efficiently and quickly than others. The sucrose flotation technique was more useful than direct smear for detecting the low numbers present at the end of the shedding period. Limited information suggested that a carrier state or relapse is probably rare.