Virulent strains of Mycobacterium tuberculosis isolated from humans are divisible into five variants by using four tests: oxygen requirement (aerobic or microaerophilic), nitrate reductase activity, susceptibility to pyrazinamide (60 μg/ml) and susceptibility to thiophene-2-carboxylic acid hydrazide (5 μg/ml). The five variants are referred to as Classical human, Asian human, bovine, African I and African II. The relation of these variants to previously described types is discussed. This simple division has been shown to be useful in epidemiological studies.

The events occurring during the time in hospital of 24 babies were recorded in detail, particularly those related to bowel function. The babies were admitted to a general paediatric unit with various diagnoses a total of 27 times during a six month period. The purpose of the study was to fill gaps in the records of a previous study (Scott et al. 1979) and to try to relate excretion of viruses detectable by electron microscopy to disturbances of bowel function (diarrhoea and/or vomiting). The results showed that a variety of viruses were associated with gastroenteropathy, that virus excretion could occur without disease and that hospital acquisition of virus is not uncommon. Antiobiotic treatment did not appear to precipitate diarrhoea in this small number of babies.

The levels of faecal coliforms (FC), indole-positive FC (presumptive Escherichia coli), faecal streptococci (FS), Streptococcus faecalis and Clostridium perfringens in the natural water sources used by 29 rural settlements in Sierra Leone were investigated. Levels of the same indicators in human faeces were also investigated. The incidence of Salmonella spp. in both habitats and the temperature, pH and conductivity of water sources were also recorded. All water sources were contaminated with the indicator bacteria, mean numbers of which occurred in the relationship FC > presumptive E. coli ≏ FS ≏ C. perfringens > S. faecalis. FC were also predominant in human faeces, the relationship of means being FC ≏ presumptive E. coli > FS > S. faecalis > C. perfringens. The need for confirmation of FC counts obtained from water sources was indicated by the large number of positive tubes produced in the FC multiple-tube dilution test from some samples which could not be confirmed as presumptive E. coli. Salmonella spp. were isolated from 13 water sources and 6% of faecal samples. Mean water temperature was high (26·2 °C), pH low (5·04) and conductivity low (34μS cm−1). Presumptive E. coli was considered the most appropriate indicator of faecal pollution of the types of water investigated.

The growth of Vibrio cholerae biotype eltor and biotype classical was studied in a range of cooked foods, shellfish and raw vegetables, incubated at 22°, 30° and 37°C. Both biotypes grew in all cooked foods but growth was not demonstrated on raw shellfish. The organism multiplied on some vegetables to levels of the order of 105/g. The classical biotypes of V. cholerae showed a longer lag period than the eltor biotypes in some foods particularly when incubated at 22°C. The eltor biotypes reached a higher level in the stationary phase than the classical biotypes.

Experimental latent herpes infection of rabbit dorsal root ganglia (DRG) is reported. The simian herpes virus used was derived from fatal natural infection in owl monkeys and has limited neurotropism in the rabbit. Following intradermal injection of the flank it causes a local lesion followed only by dorsal root ganglionitis; segmental paraesthesia and/or sensory loss going on to clinical recovery. Methods were developed for mapping sensory losses.

Virus could be immediately re-isolated from skin or DRG homogenates in the acute (first week) stage but from 8–550 days by DRG organ culture only. Spontaneous recurrence does not occur but reactivation can be provoked.

The system provides an improved analogue model for the study of the pathogenesis and symptomatic treatment of herpes zoster.

Four thousand, five hundred and sixteen rodents of 27 species were captured in widely separated localities in South Africa over a period of ten years. Samples of spleen, lung, heart, liver and rectal tissue with faeces were tested for the presence of zoonotic bacteria and 109 isolations of Pasteurella pneumotropica were made from 11 species. Latent infection with the organism was found to be widespread although there were temporal fluctuations in prevalence. Field and laboratory evidence suggest that P. pneumotropica may be associated with, but not the primary cause of, rodent epizootics in the wild.

The nasal carriage rate of Staphylococcus aureus was significantly higher in hospitalized persons (children, adult females and staff) − 53·8%, – than in similar persons at a local clinic − 29·8% (P < 0·001) – in Ile-Ife, Nigeria. However, unlike studies carried out elsewhere, a higher proportion of S. aureus strains obtained from persons at the clinic were resistant to commonly used antimicrobial agents than were strains isolated in the hospital. This has been attributed to the ease at which these drugs can be obtained by the general population and used unsupervised and indiscriminately. Methicillin was the most effective antimicrobial agent against pathogenic staphylococci (2·2% resistance), followed by erythromycin (16·5% resistance), co-trimaxozole (28·0 % resistance), chloramphenicol (76·9 % resistance), tetracycline (78·6% resistance) and penicillin and ampicillin (97·8% resistance). The widespread resistance of S. aureus to penicillin and ampicillin (and other antimicrobial agents) is of clinical significance in the treatment of post-operative infections, since carriers are reportedly more prone to such infections than are non-carriers.

Four thousand two hundred and thirty-five sera from 2794 patients and 740 sera from 735 tourists domiciled in Scotland recently returned from abroad were examined between 1977 and 1981 for antibodies to Legionella pneumophila and related organisms. In addition, specimens were examined from some patients for cultural or serological demonstration of these organisms in lung or sputum. One hundred and ten cases were diagnosed, 104 serologically, five by immunofluorescence demonstration of legionellas in lung biopsy or autopsy specimens and L. pneumophila serogroup 1 was isolated from a further case. Of patients with pneumonia 6·7% showed evidence of legionella infection. Only 0·4% of healthy tourists had antibodies at a level of ⋝ 256. The majority of cases occurred in patients aged 50–69 and in 36 patients the infection was acquired outside the United Kingdom. Males predominated, the male: female ratio being 2:1. Cases were less frequent in the first quarter of the year but those originating in Scotland were equally common in the remaining three quarters. Cases with disease acquired abroad added to indigenous cases resulted in a summer peak occurring in July, August and September. There were no outbreaks of legionellosis in Scotland.

The epidemiology in the United Kingdom of the influenza A H1N1 subtype which returned in 1977 after an absence of 20 years is described for the four winter seasons from 1977/8 to 1980/1. The age distribution of virus isolates and the evidence for antigenic variation is presented. The impact in the susceptible age groups year by year is shown by the change in the population with specific antibody. There was the expected increase of antibody in those under the age of 21 but also evidence for a significant amount of infection or re-infection in the older adult population.

A purified soluble Vi antigen was used in counterimmunoelectrophoresis (CIE), passive haemagglutination (HA) and solid phase radio-immunoassay (SPRIA) for detection of serum Vi antibody. Serum Vi antibody was detected in 13 of 14 chronic typhoid carriers by both CIE and HA. SPRIA studies showed that Vi antibodies in sera of these carriers were mainly of the IgG class. Successful treatment with amoxycillin in one carrier, who initially showed a positive Vi test, resulted in a reversion in 6 months to seronegativity as measured by Vi CIE. However, Vi antibody was also detected in 10 sera (3%) from 329 control subjects by HA but not by CIE. When the CIE assay was applied to 1030 serum specimens obtained from hospitalized patients, it was able to detect one typhoid carrier, but one (0·1%) non-carrier also gave a positive Vi CIE test. It is thus concluded that Vi CIE is more specific and no less sensitive than Vi HA for the detection of the typhoid carrier state. The finding by SPRIA that the anti-Vi antibodies present in typhoid carriers' sera were mainly of the IgG class further justified the use of CIE as a precipitation test for their detection.

In an attempt to demonstrate the pathogenicity of a newly discovered mycoplasma (strain G37) isolated from the human genital tract, six female marmosets (Callithix jacchus) were inoculated intravaginally. Four of the animals were infected as indicated by repeated recovery of the organisms on vaginal swabbing, and infection persisted for 72–149 days or more. In addition, the infected marmosets exhibited a serum antibody response detected most easily by an immunofluorescence technique, and a persistent vaginal polymorphonuclear leucocyte response not seen in two uninfected and in two uninoculated animals.

Antibacterial drugs (oxytetracycline, streptomycin and sulphonamides) were included in the drinking water of healthy broiler chicks from the sixth to the twentieth day of life to select a resistant gut flora. On the twenty-first day the birds were divided into three groups and reared in separate rooms until 100 days of age. One group was housed in cages with wire floors while the others were reared on litter. Faeces from adult hens were added regularly to the litter of one of these groups to determine its effect on the gut flora of the chicks.

The ecology of Escherichia coli was studied using O-serotyping, biotyping and antibacterial drug resistogram typing. The proportion of E. coli in the dominant faecal flora resistant to two to four antibacterial drugs increased with time to reach a peak several days after the drugs were withdrawn. Thereafter, the level of drug resistance in the E. coli declined equally in all three groups. The majority of organisms with multiple resistance were derived from biotypes of O-serotypes initially resistant to only one drug and were identified before the drugs were administered. The decline in the level of resistance in the dominant faecal flora after the fourth week was due to the appearance of either new O-serotypes or new biotypes of O-serotypes previously shown to be multiply resistant, and which were either sensitive or resistant to only one drug. It is probable that these new strains were derived from the food since several O-serotypes appeared simultaneously in all three groups of birds.

The antibody responses of 194 volunteers were studied for up to 3 years after primary immunization with one, two or three doses of human diploid cell rabies vaccine, administered either in 0·1 ml volumes intradermally (i.d.) or as 1·0 ml intramuscularly (i.m.). Sero-conversion occurred in 95% of subjects after the first injection and in 100% after the second. The highest titres and most durable antibody responses were induced by three injections of vaccine.

Booster doses were administered either by the subcutaneous (s.c.) or i.d. route, after 6, 12 or 24 months to randomly grouped volunteers; these induced responses ≥ 5·0 i.u. per ml in 95% of subjects. The responses were rapid and were neither influenced by the primary regimen nor by the timing and route of the booster dose.

Antibody titres after i.d. immunization were only two-fold lower than those induced by the larger volume of vaccine. The findings suggest that the i.d. route is both effective and economic.

The relation of salmonella isolation efficiency and the size of inoculum introduced from a buffered peptone water culture of sewage polluted water into strontium chloride B medium was investigated. Two separate studies were made, one using enrichment at 37°C, the other at 43°C. From these trials, two inocula suitable for efficient salmonella isolation were determined. Using this information, strontium chloride B medium was compared with modified Rappaport's broth (R25). The inoculum used with R25 was 0·005 ml, determined in an earlier study. Two incubation temperatures were employed with strontium chloride enrichment (37 and 43°C). Rappaport's medium was incubated at 37°C only. Elevated temperature enrichment at 43°C improved the performance of strontium chloride B, but Rappaport's broth still gave significantly better results. This supports earlier studies on simplification of salmonella isolation and standardization of routine technique on a single enrichment medium: Rappaport broth (R25) incubated at 37°C.

It was found that 26 of 127 infants with chlamydial conjunctivitis had previously received chloramphenicol eye drops. This treatment had delayed the onset and reduced the degree of oedema, congestion and discharge compared with infected infants with no ‘first-line’ chemotherapy, but eye swabs remained positive in 22 (85 %) of the chloramphenicol treated infants.

The problems of designing laboratory tests which might accurately forecast the clinical value, or lack of value of antibiotics in chlamydial infections were investigated. The minimum inhibitory concentration (MIC) of chloramphenicol, against Chlamydia trachomatis in McCoy cell cultures varied widely according to the antibiotic preparation used, the timing and duration of its exhibition in relation to the single step growth cycle of C. trachomatis, and, in particular, the method of examination of infected tissue cultures for residual chlamydial growth after incubation with chloramphenicol.

An investigation of the bacterial flora in over 200 homes is reported. The occurrence of potential pathogens and the levels of contamination at individual sites, particularly in the kitchen, toilet and bathroom is described and the implications for hygiene practices in the home discussed.

Thirty-nine strains of klebsiella isolated from ankylosing spondylitis patients were examined by the methods of Cowan & Steel (1974), those described by Edmondson et al. (1980) and by capsular typing. No significant difference was detected by any of these methods between these strains and those examined by other workers from non-ankylosing spondylitis patients and other environments.

As the literature on Haemophilus ducreyi and clinical chancroid is reviewed, it becomes obvious that many significant findings have been forgotten over the years. As a result, from the time of Ducrey's original description of the organism in 1890 until about 1977, both clinical and laboratory experts in the United Kingdom believed that H. ducreyi infections were rare, generally acquired abroad, and almost impossible to confirm in the routine laboratory! In consequence it was a common view that it was not worth looking for H. ducreyi until all other possible causes of genital ulceration had been excluded. Moreover, the search for such an infection stopped as soon as any other cause for the patient's lesions had been found.

A decision to ignore this ‘rule’ in Sheffield led to our looking for H. ducreyi in specimens from an unselected series of patients with genital ulceration including a number with herpes genitalis infections. The surprise finding of H. ducreyi in circumstances suggesting that it was a secondary invader made us re-examine the whole question of H. ducreyi infections and chancroid and wonder if the same organism can act as a primary pathogen and as a secondary invader. An account of the media and methods we used and of the characteristics of the organism is presented. In an attempt to find out more about the characteristic coherent colonies of H. ducreyi we studied them with the scanning electron microscope. It is clear that the whole subject of H. ducreyi infections has been neglected in the United Kingdom, but we believe that interest has now been aroused and progress will surely follow. Some areas for further investigation are suggested.

Trials of rodenticidal baits containing 50 p.p.m. difenacoum, 50 p.p.m. bromadiolone or 20 p.p.m. brodifacoum were carried out on farmsteads against populations of Rattus norvegicus containing difenacoum-resistant individuals. Six difenacoum treatments failed in 14–42 days of baiting. Two treatments with bromadiolone succeeded in 23 and 33 days, but four further treatments lasting 35–56 days failed to eradicate the populations. Brodifacoum gave virtually complete control of six populations in 21–73 days and of the ten residual populations left behind by the other two compounds, after baiting for a further 11–85 days. The performance of both bromadiolone and brodifacoum was well below that reported by previous investigators, indicating the possibility of low-grade resistance to these compounds in the difenacoum-resistant strain.

Colonization of the caeca of newly hatched chicks by Salmonella typhimurium was prevented by oral administration of a mixture of cultures comprising 48 different bacterial strains originating from an adult bird known to be free from salmonellas. The treatment conferred protection to the same degree as that obtained previously with a suspension of adult caecal contents or an undefined anaerobic culture from the same source and was demonstrated in four separate laboratory trials.

Examination of the caecal microflora of chicks one day after being given the protective treatment showed that the presence of high levels of lactobacilli and Bacteroides spp. which are not found usually at two days of age in chicks produced under commercial conditions was indicative of the successful establishment of an adult-type microflora.

Although the usual method of administering the protective organisms was to dose the chicks directly into the crop, it was also found possible to incorporate the organisms in the drinking water given to the birds at dilutions up to one in five, the maximum tested.

When chicks were given the bacterial mixture via the crop and fed on a diet containing 10 mg kg−1 nitrovin and 100 mg kg−1 monensin, the bacteroides failed to establish in the caeca and the birds were not protected against salmonella colonization. However, when the bacterial cultures were incorporated in the drinking water and the chicks given the same feed, normal protection was obtained; possible reasons for these observations are discussed.