Laboratory studies have provided evidence that the replication of dengue viruses in preparations of primary peripheral blood mononuclear cells of human or simian origin, or in macrophage-like cell lines of human or murine origin, may be enhanced by sub-neutralizing concentrations of homotypic dengue antibody, by heterotypic dengue antibody, or by antibody against heterologous flaviviruses. The mechanism underlying this phenomenon is discussed in the context of dengue haemorrhagic fever and the dengue shock syndrome.

This paper describes virological and epidemiological features of an infection which killed two of three affected cheetahs at Whipsnade Park in 1977. Two animals had profuse skin lesions and the third had an acute haemorrhagic pneumonia. The outbreak was shown to be caused by cowpox virus. Cowpox virus is believed to circulate in small wild animals, but the source of infection was not traced despite virological and serological tests on 93 captive and 102 wild animals.

Sub-clinical infections did not occur in susceptible contact cheetahs. Immune globulin did not influence the outcome and smallpox vaccine does not take in cheetahs. Management of any future outbreak will rely on prompt diagnosis and segregation of infected animals.

The white pock variant of cowpox virus shows limited growth in chick embryo fibroblasts maintained in arginine-deprived culture medium. Since these conditions inhibit the growth of parental virus, there is a marked increase in the frequency of the white variant in the virus population recovered after passage in the absence of arginine. The variants generated in this system have been characterized by restriction endonuclease analysis of virus DNA in the total DNA recovered from infected cell cultures. Such analysis shows that the white variants arise as deletion mutants of the parental virus, but there was considerable heterogeneity in the restriction patterns of different isolates examined shortly after their generation. Further passage selected white cowpox virus populations with a stable genome configuration comparable with the DNA of pock-purified white variants.

White pock variants of cowpox virus give papular lesions on intradermal inoculation of rabbits, without the necrosis and haemorrhage that are produced by wild type cowpox viruses. Rondle & Dumbell (1962) have shown that white pock variants of cowpox virus fail to produce a specific, precipitating antigen which they called ‘d’ substance. In this paper it is shown that ‘d’ is demonstrable in soluble antigen preparations of rabbitpox virus and of neurovirulent strains of vaccinia virus but not in soluble antigens of variola viruses. Two series of recombinant viruses prepared by Dumbell & Bedson (1964) from variola and cowpox and from variola and rabbitpox viruses were tested for the production of ‘d’ substance. These results were compared with the previously recorded effects of these recombinants when inoculated intradermally in rabbits. It is concluded that functional genes determining the production of ‘d’ and of rabbit skin pathogenicity are closely linked on the pox virus genome, but that there is insufficient evidence to say that the two functions are interdependent.

The international reference strains of variola major (Harvey) and of variola minor (Butler) were grown in cultures of skin and muscle cells from human embryos. The development of infective virus, complement-fixing antigen, haemagglutinin and cytological changes were followed at four temperatures between 35 and 40 °C. No significant difference was found in the amount of virus produced by Harvey or Butler viruses at any of the experimental temperatures, but Harvey attained the plateau titre at 16 h, some 4 h ahead of Butler in the cultures incubated at 38 °C. Harvey also produced a higher and more prolonged yield of virus in the extracellular medium of cultures, inoculated at low multiplicity and incubated at 37 °C. At 38 °C small inocula of Harvey produced foci which developed and spread till the whole culture was necrotic; Butler foci did not spread and remained relatively undeveloped at this temperature.

The Virus Reference Laboratory, Colindale, first embarked on laboratory investigations for smallpox early in 1947. From then, in conjunction with the Department of Bacteriology, University of Liverpool, it provided a complete diagnostic service throughout England and Wales until 1962, after which the service became available regionally until eradication was effected. Up to 1970 it had investigated 2696 specimens from suspected cases of smallpox and had recovered 108 strains of variola and 248 of vaccinia virus. These last were from persons suffering the complications of vaccination. Some outbreaks following smallpox importation are discussed but infection among laboratory staff during this period was not demonstrated.

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.

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 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.

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.

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.

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.

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.

Epidemiological data accompanying reports of more than 1000 outbreaks of food poisoning have been studied to determine the factors which most frequently contributed to the outbreaks. Preparation of food in advance of needs combined with improper storage and inadequate cooking, cooling and reheating were the most common factors. Infected food handlers did not play a significant role except in instances of S. aureus food poisoning.

Enterotoxin production by strains of Staphylococcus aureus isolated from clinical specimens of human and animal origin and from healthy human carriers was investigated. All nine patients admitted to hospital with symptoms of toxic shock syndrome (TSS) yielded enterotoxin-producing strains of S. aureus. Eight of these produced staphylococcal enterotoxin F (SEF). A significantly smaller proportion of strains (42% of 50 strains tested) isolated from other clinical specimens of hospitalized patients produced SEF. Production of SEF by strains isolated from clinical specimens of animal origin (48 strains) was not observed. Twenty-nine per cent of 24 S. aureus strains isolated from noses of hospital staff produced SEF. This result was not significantly different from that obtained from strains isolated from clinical specimens other than TSS. A similar percentage of strains isolated from healthy human carriers outside hospital produced SEF (25% of 24 strains tested).

The results indicated that enterotoxin production, especially that of SEF. is associated with S. aureus isolated from patients suspected of TSS. There was no indication of an association between S. aureus isolated from other staphylococcal infections and SEF production.

All strains were phage typed and 79%, of the strains belonging to the international phage-group I produced SEF. All strains lysed by phage 187 were found to produce SEF.

Nineteen of 98 samples of mud or sand taken from the Mersey estuary in 1981 contained Clostridium botulinum type C, the organism almost always responsible for botulism in water birds. In the Dungeon and Score Bank areas, where many dead and dying birds were found during the period September–December 1979, almost half the samples contained type C. Most of the positive samples were essentially muddy rather than sandy. The findings do not prove that botulism contributed to the 1979 mortality but are nonetheless thought-provoking, particularly because type C – unlike type B – is by no means ubiquitous in Britain. Type B was present in 12·2% of samples from the Mersey estuary.

A limited assessment of immunity to diphtheria revealed that only 44·8 % of adults had protective levels (> 0·01 U/ml) of diphtheria antitoxin in their sera. In the light of this information, it was decided to assess the suitability of Adult-type Tetanus-Diphtheria Vaccine as a replacement for Adsorbed Tetanus Vaccine in occupational health schemes. A comparative study of these vaccines showed that a single dose of each produced an equivalent rate and level of tetanus antitoxin responses. Adult-type Td Vaccine elicited more than fourfold increases of diphtheria antitoxin in 76 % of vaccinees. No statistically significant differences were observed in the clinical reactivity of the vaccines under test. However, the combined vaccine caused a slightly higher incidence of local reactions (pain, redness and swelling) while recipients of Adsorbed Tetanus Vaccine more frequently experienced pain.

So-called LC strains of Mycoplasma mycoides subsp. mycoides and, where appropriate, SC strains, were examined, together with M. mycoides subsp. capri strains, by growth, fermentation, and antibiotic-sensitivity tests.

Growth curves in BVF-OS medium showed that, from the 6th until at least the 19th day of incubation, strain Mankefår 2833 had a viable count strikingly higher than that of any other LC strain. Its robust growth properties may explain its ability – unusual among LC strains – to produce mycoplasmaemia readily in mice. Strain 143–A66 Conn, also shown by earlier experiments in mice to possess unusual properties, lost viability more rapidly than any other LC strain between the 13th and 19th days of incubation. The viable count of a subsp. capri strain was considerably lower than that of any LC strain for much of the period between days 6 and 19.

In fermentation tests with 27 substrates and sensitivity tests with 11 antibiotics the strains gave results that, in all but the following respects, were uniform. Sorbitol was fermented to varying degrees by all the LC and subsp. capri strains tested but was unaffected by the SC strains. The LC and subsp. capri strains were in general more resistant than the SC strains to streptomycin. The growth of the LC strains, much more than that of the other strains, was greatly stimulated by the presence of fermentable substrate.

Immunoelectrophoresis of ultrasonically disrupted Haemophilus equigenitalis (contagious equine metritis organism) cells against rabbit and equine antisera disclosed at least 11 precipitating antigens. Two of these, a polysaccharide and a lipopolysaccharide–protein complex, were of high molecular weight and located on the cell surface. The remaining antigens were intracellular and were small- to medium-sized proteins.

The surface antigens were the most significant in relation to the serological response in infected horses. They also reacted with sera from apparently healthy cattle, but the reason for this was not determined. No serological cross-reaction between H. equigenitalis and species of Achromobacter and Moraxella was detected.