In England and Wales human salmonellosis is a major public health problem and, although mortality is low, the disease has important social and economic consequences. All surveillance indicators suggest that an epidemic of unprecedented proportions is occurring. Between 1081 and 1980 the number of strains received for serotyping by the Public Health Laboratory Service (PHLS) Division of Enteric Pathogens has increased by 60% (Table 1). This is predominantly due to strains of Salmonella typhimurium and S. enteritidis. Smaller but significant increases have occurred in the numbers of S. virchow and S. Stanley. With the exception of the latter serotype, which seems to come from a bovine reservoir, the indications aro that poultry is the main source of the increase in infections.

There occurred during the planning and publication of this review: the twentieth anniversary of the start of the intensified WHO Smallpox Eradication Campaign and the tenth anniversary of the last endemic case of smallpox; debate about the fate of smallpox virus and possibly its irrevocable destruction; claims that mass smallpox vaccination campaigns may have helped the spread of AIDS in Africa; publication of the definitive account of Smallpox and its Eradication (Fenner et al. 1988), and the closure of the WHO Smallpox Eradication Unit (SEU). It is therefore perhaps an appropriate moment to assess the current status of human poxvirus infections and their epidemiology; this review concentrates on those viruses antigenically related to smallpox (i.e. orthopoxviruses).

Cytomegalovirus (CMV) is a common infectious agent which is well adapted to its host. Following primary infection, which is almost always asymptomatic in people with normal immunity, the virus establishes latency at sites which are unknown. The virus is probably maintained in this latent state by immune surveillance mechanisms since immunosuppression frequently leads to reactivation of virus.

Cytomegalovirus has been identified in most anatomical areas of the human body. The aim of this article is to define criteria for pathogenicity so that clinical and experimental data can be reviewed to determine if CMV is likely to cause disease at these various clinical sites. Thus, patients have been shown to die frequently with CMV but do they die from it?

A prospective study of faecal colonization with P-fimbriated Escherichia coli between 0 and 18 months of ago was conducted in 751 healthy infants. The influence of breast-feeding and treatment with antibiotics on this colonization was studied. Colonization with P-fimbriatcd E. coli increased with age from 10% at 6 days to 30% at 18 months of ago (P < 0·01). Breast-feeding influenced colonization at 6 weeks of age when breast-fed children harboured fewer bacterial species (P < 0·001) and fewer P-fimbriated E. coli (P = 0·06) than bottle-fed infants. Treatment with antibiotics increased the colonization rate with P-fimbriatcd E. coli at the age of 11 months (P < 0·05). However, this was not true for treatment with ampicillin, which increased colonization rate with Gram-negative species other than E. coli (P < 0·05). Fifty per cent (378) of all children were colonized and a quarter (183) had pure cultures of P-fimbriatcd E. coli in at least one faecal sample. The clinical importance of this colonization remains to be shown.

The predominant causative organism of whooping cough in Australia is of a serotype which has normally been associated overseas with unvaccinated communities. Australian DTP vaccines pass the statutory mouse test for Bordetella pertussis potency but this test is now believed to be relatively insensitive to certain factors, especially the major type-specific agglutinogens, which are presumably also important in the human host-parasite relationship. Because endemic B. bronchiseptica infections make some laboratory animals unsatisfactory for testing B. pertussis agglutinin responses, we have developed a test in which young farm sheep were immunized with vaccines. Type-specific agglutinins in their sera were assayed after absorption of non-specific agglutinins by suspensions of selected bordetella strains. Three well-reputed European DTP vaccines and two recent batches of Australian DTP vaccine were tested and compared thus. All evoked significant agglutinin responses to the main agglutinogens.

Eighty-two chickens purchased at 11 retailers (supplied by 12 wholesalers) in the south of England were cultured for Campylobacter jejuni by a method involving total immersion. The organism was isolated from 22 (48%) of 46 fresh birds, 12 of 12 uneviscerated (New York dressed) birds, but only 1 of 24 frozen birds. Viable counts of up to 1·5 × 106/chicken were obtained from fresh birds and 2·4 × 107/chicken from uneviscerated birds. Surface swabbing of breasts, thighs, wings and vents of fresh chickens showed that contamination was generally distributed over the carcasses. Salmonellas were found in only 2 of 69 of the fresh chickens.

The prevalence of several Lior and Penner C. jejuni serogroups was similar in chickens and sporadic human cases of enteritis. Penner serogroup 4 (mostly of Lior serogroup 1) was found in 26% of human isolates and 14% of chicken isolates.

The rising incidence of campylobacter enteritis during the last 6 years could well be a reflection of the increasing proportion of fresh chickens consumed over that period (32% higher in 1986 than in 1981).

An investigation was undertaken to determine the isolation rate and antibiotic resistance of Haemophilus influenzae from the nasopharynx of young children. The 996 subjects studied were up to 6 years of age. H. influenzae was isolated from 304 (30·5%) and strains of capsular type b from 11 (1·1%). Age, sibling status, season, respiratory infection and antibiotic therapy all influenced isolation rates. The overall prevalence of antibiotic resistance in the strains isolated was ampicillin 5·4% (all β-lactamase producers), cefaclor 0·3%, chloramphenicol 1·3%, erythromycin 38·2%, tetracycline 1·3%, trimethoprim 5·4% and sulphamethoxazole 0%. Ampicillin resistance was more common in type b than non-capsulated strains.

Minimal colonization inocula for two broiler strains of Campylobacter jejuni were determined in broiler chicks aged 2–3 days and 2 weeks. Individually housed chicks were exposed to a single oral or cloacal challenge. Diarrhoeal symptoms were absent in all 380 chicks included in the study. Chick susceptibility to the two C. jejuni strains varied. Colonization was effected by < 102−104 colony forming units (c.f.u.) via cloacal challenge and 104–106 c.f.u. via the oral route. Colonization inocula for 2-to 3-day and 2-week-old chicks were similar. Treatment of 1-day-old chicks with fresh adult caecal flora or an anaerobic broth culture of adult caecal flora did not inhibit colonization after challenge with low-dose C. jejuni. Susceptible chicks were colonized rapidly. C. jejuni was detected in 167 of 189 (88%) colonized chicks within 3 days of challenge and persisted during the 2-week monitoring period. Our data suggest that colonization of broiler chicks with C. jejuni is effected more easily by the cloacal than the oral route and is independent of age.

One hundred and twenty-four strains of non-penicillinase-producing gonococci isolated in Munich in 1986 were characterized in terms of their plasmid content and protein I serovar. Eighty-two per cent of the strains belonged to serogroup 1-B with over half belonging to either serovar 1B-2 or 1B-3. Half of the 22 serogroup 1A strains belonged to serovar 1A-2. Nineteen strains (15·3%) were found to lack the 2·6 Md cryptic plasmid although seven of these strains contained the 24·4 Md conjugative plasmid. Nine of the 105 strains which harboured the cryptic plasmid also contained the conjugative plasmid. The 19 strains which lacked the cryptic plasmid comprised 10 different serovars, indicating the heterogeneous nature of this group of organisms.

During the 5-year (1981–5) surveillance period, 2322 salmonella isolations were recorded from animals and other non-human sources in Peninsular Malaysia. This was an increase of 356% over the preceding 5-year period. The 83 serotypes isolated were recovered from 41 sources. Of these 34 were new serotypes bringing the total number of serotypes isolated from non-human sources to date up 97. Food animals and edible animal products accounted for 92·2% of the total isolations, with cattle and beef accounting for 70% of the total. Salmonella dublin was the most frequently isolated serotype, whereas S. typhimurium had the widest zoological distribution. More than 80% of the non-human salmonella serotypes have also been reported in man in this country.

Poultry-borne salmonellosis is the most common form of foodborne infection in Scotland for which the vehicle can be identified, yet little is known about the costs imposed on society by this disease, or the costs of preventing it. The present study identifies and values the costs of a hospital based outbreak of poultry-borne salmonellosis. Account is taken of costs falling on individuals, the health services and society as a whole. Depending on assumptions made about the value of ‘intangibles’, the cost of the outbreak is estimated to be between £200000 and £900000.

Tachyzoitcs of the RH strain of Toxoplasma gondii were inoculated intravenously into sheep following which serum samples were collected at approximately weekly intervals for 9 months. The sera were examined by the toxoplasma dye test and two enzymc-linkcd immunosorbent assays (ELISA) specifically developed for investigations of ovine toxoplasmosis. One was an antibody class capture assay for the detection of anti-toxoplasma specific IgM, the other an indirect assay which detected anti-toxoplasma IgG.

Some of the sheep had antibodies to toxoplasma prior to inoculation but none had specific IgM. Sera collected 17 days after inoculation showed that all had raised specific antibody levels but the only sheep that produced specific antitoxoplasma IgM were those that were initially without any antibody. Specific IgM could be detected in all these particular sheep for at least 1 month after infection and up to 3 months in some. Specific IgG persisted at high levels for at least 3 months and could still be detected at moderate levels for at least 9 months. The ELISA methods described are simple to perform and could clearly distinguish between previous infection and this experimental infection with Toxoplasma gondii.

In an experimental study on a piggery it was found that haemolytic Escherichia coli of O-scrotypes 138 or 139 proliferated in the intestinal tracts of pigs following weaning, with E. coli of the 0-138 typo also being occasionally recovered from unwearied pigs, and onco from a sow. Organisms of the O-138 typo produced heat labile enterotoxin and their presence in weaned pigs was associated with the development of severe post-weaning diarrhoea. E. coli of O-130 type produced a vero cell cytotoxin and were associated with a milder diarrhoea in weaned pigs. Under various managemental circumstances the O-138 type E. coli almost invariably proliferated after weaning. The O-139 strain of E. coli did however proliferate rather than the O-138 strain following the movement of weaned pigs to new accommodation, after weaned pigs were returned to their sow and then weaning again 5 days later, and very occasionally in pigs weaned at 5 weeks of ago. In all theso cases earlier proliferation of the O-138 E. coli had been detected, suggesting that this may be a prerequisite for proliferation of the O-130 strain.

Between 1969 and 1984, 6564 non-typhoid salmonella strains were isolated at the Liverpool Public Health Laboratory of which 194 (3·0%) were from extraintestinal sites. Blood (34%) and urine (32%) isolates accounted for twothirds of these, with the remainder being recovered from pus and inflammatory tissue (23%), bone (5%), cerebrospinal fluid (5%) and sputum (3%). Certain serotypes tended to cause more invasive disease than others, i.e. Salmonella choleraesuis, S. dublin, S. london, S. virchow and S. panama: this association for S. london has not previously been described. The spectrum of disease caused by non-typhoid strains was broad. This survey confirms the importance of nontyphoid salmonellas as occasional causes of invasive disease and local sepsis outside the gastrointestinal tract.

The treatment of feed given to laying hens with 0·5% formic acid reduced significantly the isolation rate of salmonellas and was associated with a reduction in the incidence of infection in newly hatched chicks. These improvements were not sustained until slaughter, however, as growing birds acquired salmonellas, probably from feed which was not acid treated. The data indicate that formic acid treatment of chicken food could have important benefits for the public health.

Electrophoretic types B1 and B2 of carboxylesterase B produced by strains of Escherichia coli isolated from 100 septicaemia cases were correlated with α-haemolysin and mannose resistant haemagglutinin (MRHA) production and with clinical data including eventual underlying diseases, origin of septicaemia and evolution. Electrophoretic type B2 was phenotypically linked with α-haemolysin and MRHA production. The proportion of type B2 isolates varied significantly with occurrence of an underlying illness (45% for patients without an underlying disease and 22% for compromised patients) and with the site of origin of the septicaemia (40% for those of urinary origin and 18% for infection of digestive origin). In the former infections, type B2 isolates were obtained in the majority from male patients while type B1 isolates predominated in women. The septicaemias associated with type B1 were characterized by a lower proportion of isolates producing α-haemolysin and MRHA and by a greater frequency of septic shock and death than those associated with type B2. These facts emphasize the importance of host-dependent factors in E. coli septicaemia.

A total of 637 strains of Salmonella bareilly received from different parts of India between 1959 and 1985 were phage typed using five locally isolated wild phages. The overall typability was 94·5% and 11 different phagc types could be defined. Phago types 10 and 1 were the most prevalent and the geographical and source distribution is described.

The use of the methylene blue test for the examination of cows milk was investigated in an inter-laboratory survey. A poor relationship was found between results of these tests and total viable counts. Coliforms were detected in a large number of pasteurized milks, indicating frequent post-pasteurization contamination. No relationship was found between the results of the methylene blue test and the presence of coliforms.

Results from this survey highlight the need for reappraisal of the methylene blue test as a statutory method for the examination of milk. A total viable count and coliform test are suggested for providing information regarding dairy hygiene and the quality of the product at the point of retail sale.

Two hundred and forty-eight patients from shared oncology and general medical wards were prospectively studied over a 6-month period for carriage of Clostridium difficile during an outbreak of clinical disease with an epidemic strain of the organism. Risk factors for infection were assessed. Acute leukaemia and/or its treatment were identified as significantly increasing the risk of infection.

The relationship between the type of C. difficile isolated (as defined by a typing system based on the incorporation of [35S]methionine into bacterial proteins followed by gel electrophoresis), the presence of faecal toxins A and B and clinical symptoms were analysed. Carriage of the epidemic strain, type X, had a significant association with symptoms amongst oncology patients, with two thirds of these patients having detectable faecal toxin A and one third detectable faecal toxin B. During an outbreak of C. difficile-associated disease, typing the organism and assaying for both faecal toxins in symptomatic patients may be of benefit in determining which patients require specific, urgent treatment.

Intestinal thermophilic Campylobacter species produce stable patterns when subjected to bacterial restriction endonuclease DNA analysis (BRENDA); this technique is therefore of considerable value in epidemiological studies. BRENDA was used to examine thermophilic Campylobacter species from humans, wild and domestic animals. One hundred and ninety-four (61%) of 316 isolates of Campylobacter jejuni from humans had BRENDA patterns which could be matched to those of animal isolates. Poultry appear to be a major source of nfection for C. jejuni in humans with nearly half (49·7%) of the human isolates giving patterns which were indistinguishable from those isolated from poultry. A total of GO BRENDA types were identified from 316 human isolates and 11 of these had the same pattern as those isolated from poultry. One of the three Campylobacter coli BRENDA types recovered from poultry was indistinguishable from a human isolate type. Pigs appear to be only a minor source of C. coli infection for humans in New Zealand. Rats were found to be infected with strains of C. jejuni with BRENDA patterns indistinguishable from those infecting numans, poultry and a horse. None of the 102 isolates of Campylobacter species from wild birds gave BRENDA patterns similar to those of isolates from humans.