An epidemiological study of Sonne dysentery in Dundee during the years 1971–6 was made by examining, in respect of 1420 isolates of Shigella sonnei, the discriminating power of colicine typing, antibiogram testing, biotyping and resistotyping and the stability of the markers they provided.

Colicine typing identified nine colicine types, including four not previously described. However, because types 4 and 4 var., determined by col Ib, and type U, producing no colicines, accounted for 96 % of the isolates, discrimination with colicine typing was poor. In antibiotic sensitivity tests, 13 different antibiogram patterns were noted. Less than 1 % of the isolates were sensitive to all of the eight antibiotics tested; most were multiply drug-resistant. Resistance to kanamycin, neomycin and paromomycin (KNP) was apparently due to a single resistance determinant, widely distributed in a majority (53%) of the isolates. When definitive times were chosen for reading each biotyping test, only maltose and rhamnose of the 13 ‘sugars’ tested differentiated isolates into prompt- and late-fermenting types. Though the ability to ferment rhamnose was a stable property, it discriminated only 1·5% of the minority, late-fermenting type. Resistotyping with six chemicals discriminated eight epidemiologically valid resistotypes, including three new types. However, 93 % of the isolates belonged to only three resistotypes.

Analysis of the data for isolates from 286 epidemiologically distinct episodes showed that the variability of colicine and antibiogram characters, found among isolates within, respectively, 40 and 28 % of the episodes, was generally associated with loss or gain of a plasmid (‘col Ib-KNP’) which determined production of colicine Ib and KNP resistance. These characters varied both in vivo and in vitro. Variability of resistotype characters, on the other hand, was observed in only 28 (9%) episodes, 14 of which possibly represented examples of mixed or sequential infections.

For accurate epidemiological tracing of strains of Sh. sonnei in a community, resistotyping, the technique showing the greatest discrimination and least variability of the four tested, should be included as the principal typing method.

Different strains of Shigella sonnei present in Dundee from 1971 to 1976 were identified by a ‘multiple typing’ method in which resistotyping, used as the main method of differentiation, was supplemented by colicine typing, antibiogram testing and biotyping. At least 19 different ‘multiple types’ (MTs) were identified by combining information from the four typing techniques. The relation of the different types and their possible derivation from each other are discussed.

The practical value of multiple typing was demonstrated in a study of 247 isolates, of three distinct MTs, recovered from 178 persons involved in an extended outbreak centred primarily on day nurseries.

A few episodes that yielded isolates of different resistotypes were analysed to determine whether the cultures were: isolates of the same strain different in resistotype as a result of in vivo or in vitro variation of resistotype characters, or isolates of distinct strains of different resistotypes.

The multiple typing approach clarified the way in which different MTs emerged, persisted, disappeared or co-existed in the community during the 6 years of the study.

Gas production by coliform organisms and Escherichia coli from lauryl tryptose lactose broth (LTLB) was compared with that from brilliant green (lactose) bile broth (BGB). These media were compared with lauryl tryptose mannitol broth (LTMB) with and without added tryptophan for both gas and indole production. At 37 °C, LTLB and BGB were both satisfactory for gas production, but at 44 °C, LTLB gave fewer false-negative results and was thus significantly less inhibitory than BGB. However when LTLB and LTMB were compared as single-tube confirmatory media, LTLB give a high proportion of false-negative reactions in the indole test at 44 °C. The substitution of mannitol for lactose and the addition of tryptophan yielded a satisfactory medium for both confirmation of gas production and the demonstration of indole at 44 °C.

Unadsorbed, regular production pertussis vaccine was treated with polymyxin B sulphate at concentrations of 25,50 and 100 μg/ml. The toxic activity of treated and untreated vaccines was compared using both the limulus amoebocyte lysate test and the mouse-weight-gain test. Protective efficacy was also assessed by the mouse protection test. No discernible effect on either toxicity or efficacy of the pertussis vaccine was observed. When the vaccine was treated with 5000 μg/ml of polymyxin, endotoxic activity assessed by the limulus lysate test appeared to be abolished.

Antibody responses to influenza virus immunizations were examined among junior high school students. The students received two doses of a commercial split-product vaccine containing influenza A H1N1 during a 2-year period following the first appearance of H1N1 virus in the winter of 1977–78. In haemagglutination-inhibition (HI) tests, the students who had been infected with H1N1 virus in 1977–78 showed a better response and wider cross-reactivity to the drift strain than the students who had not experienced earlier H1N1 influenza infection. Neuraminidase-inhibition (NAI) antibody titres after immunization depended upon a history of natural infection with H1N1 virus, since students not previously infected showed no significant NAI antibody rise after immunization.

Parainfluenza viruses were isolated 165 times during 14 years surveillance of the illnesses of a general practice population of around 3700. Type 1 isolations numbered 57, type 2 isolations 22 and type 3 isolations 86, representing annual rates of 33, 13 and 50 infections respectively per 10000 of population. Type 4 parainfluenza virus was not isolated. Three major classes of illness gave the following rates: sore throats (Throats) nine, acute febrile respiratory diseases (FRD) 23, acute non-febrile respiratory diseases (non-FRD) 71. The illnesses caused by the three types isolated were similar. Type 1 infections were most abundant in November and type 2 infections in December, and only 11.4 % of these types were isolated in the warm semester April through September. Type 3 infections were seasonally bi-modal, with a winter peak in January and an even greater prevalence (66% of the total) in the warm semester. Type 3 infections in the warmer months and in the later years of the Survey were usually more severe. Type 3 virus may therefore be heterogeneous, one subtype possessing and the other lacking the genetic mechanism of ‘cold-season’ prevalence. Geographical discontinuity between summer and winter isolations strengthens the case for the existence of the two subtypes of type 3 parainfluenza virus.

Type 3 infections caused the majority of the infections in very young infants. Type 2 infections were widely distributed at all ages. Females were attacked more often than males: type 1, 68.4%; type 2,636%; type 3, 53.5%. Type 3 infections in males outnumbered those in females up to 60 years of age, whereas female predominance became apparent in types 1 and 2 before 10 years of age.

All types were widely and sparsely distributed, areas of prevalence changing from year to year. Recurrences occurred only twice, both with type 3 infections. Six persons suffered both a type 1 and a type 3 infection, and one person suffered both a type 2 and a type 3 infection.

Ninety-five patients with recurrent pyogenic cholangitis had a range of specimens taken at laparotomy for bacterial culture. Bacteria were isolated from 68 % of cases. Escherichia coli was the predominant pathogen. Other aerobic and anaerobic intestinal bacteria were also isolated. Liver biopsy, bile and gallstones were the most rewarding specimens for culture. Infection was usually localized, but systemic infection occurred occasionally. The site of infection is probably in the liver parenchyma; however, the route by which intestinal bacteria invade the liver is not known. Sixty per cent of the cases of recurrent pyogenic cholangitis had gallstones and 20% were infected with Clonorchis sinensis.

A study of stool Escherichia coli in 60 children with gastroenteritis and 18 control children was carried out in Auckland, New Zealand in 1977. Toxigenic strains, heat labile and heat stable, predominated in the stools of only three children, all of whom had concomitant rotavirus. Classical enteropathogenic E. coli (EPEC) were found in patients and controls. Only one patient had many EPEC in the stool (086. H2), they were variably toxigenic and rotavirus was also present. No toxigenic serotype was isolated. Two potential pathogens were sometimes found. Overall there was no evidence for a substantial causative role for disease producing E. coli in these children.

Campylobacter jejuni was an almost regular finding in chickens and in minced meat from pigs and cattle sold in ordinary food stores. The bacteria survived on the food at 4 °C for one week and frozen at – 20 °C for three months. None of the stains tested survived heat treatment at 60 °C for longer than 15 min. C. jejuni is apparently a frequent guest in most kitchens. Correct food handling and heat treatment to at least 60 °C for 15 min should be enough to prevent infection.

Epidemiological aspects of infection with leptospires of the Ballum serogroup in black rats (Rattus rattus) and brown rats (Rattus norvegicus) are described. Rats inhabiting a variety of habitats were investigated and isolates identified as belonging to the Ballum serogroup were obtained from 21 of 61 black rats (34%) and 63 of 243 brown rats (26%). The high level of endemic Ballum serogroup infection in these species reported here has not been described in other countries.

A statistical relationship was shown between the prevalence of infection in brown rat populations and population density but this was not evident for black rats. Epidemiological data indicates that the black rat is a maintenance host for leptospires of the Ballum serogroup in New Zealand. The brown rat does not appear to be an efficient maintenance host for these leptospires, however endemic infection can be maintained in high-density populations inhabiting synanthropic foci.

An hypothesis of ‘competitive exclusion’ (preferential maintenance of a particular serovar by a host species) is introduced with regard to leptospiral infection in brown rats. It is concluded that the establishment and maintenance of an endemic focus of leptospirosis is dependant on: introduction of a particular serovar; a suitable host; and a suitable host habitat. Within a maintenance population direct transmission appears to be more important than indirect transmission via the environment.

The so-called SC (small colony) and LC (large colony) strains of Mycoplasma mycoides subsp. mycoides are said to be indistinguishable by the in vitro serological tests generally used in mycoplasmology. In mice the immunity given by a single dose of killed LC-strain vaccine against challenge with SC strains is – unlike that given by SC-strain vaccine – only partial.

When multiple doses of killed or living vaccines were given, the majority of 13 LC strains still failed to immunize completely against a SC strain. This suggests that, although some protective antigens are shared between both types of strain, at least one of importance is present in the SC strains but absent from the majority of LC strains. The difference between the protective-antigen content of SC and most LC strains is thus qualitative, and not merely quantitative.

A prospective study of hepatitis that began in 1968 and continues to include more than half the dialysis units in the United Kingdom shows that type B infection has been completely controlled in such units since the last outbreak ended in 1973. Though occasionally a single patient has developed hepatitis B surface antigenaemia in the course of dialysis or after transplantation, the infection has not spread to other patients or staff in the survey units.

A detailed analysis of the results in 1974–75 shows clustering of patients with raised aminotransferase levels in about one-fifth of the units but, unlike past outbreaks of hepatitis B, these clusters are not accompanied by clinical hepatitis among staff. The possibility that some of the clusters are caused by hepatitis viruses other than type A or B is discussed. It is concluded that, when reliable tests for type non-A non-B infections become available, the continued existence of the survey will allow prompt assessment of any viral hepatitis problems that may still exist in UK units.

Inactivated vaccines prepared from influenza virus strains obtained by the recombination of A/PR/8/34 (H1N1) or A/FM/1/47 (H1N1) viruses with A/Victoria/3/75 (H3N2) virus, were tested for their antigenicity in hamsters. The parental origin of the genes of each cloned recombinant virus was determined by polyacrylamide gel electrophoresis, and vaccines prepared from each strain by concentration, purification on sucrose density gradients and inactivation with formalin. All the recombinant strains used in these studies possessed surface haemagglutinin and neuraminidase antigens derived from the A/Victoria/75 parent strain.

On inoculation into hamsters, at equivalent concentrations, these vaccines varied in their ability to induce haemagglutination-inhibiting (HI) antibodies in the serum. This variation was not dependent on concentration and was observed using neutralization and single radial haemolysis, as well as HI. The possible reasons for the findings are discussed.

Outbreaks of wound infection with Streptococcus pyogenes and Staphylococcus aureus occurred in an abattoir and a pork-processing factory in Autumn 1980. Investigations showed that staff handling the meat before de-boning were particularly affected and that bone was the cause of 48 % of the wounds which became clinicially infected. Of the total isolates of Strep. pyogenes and Staph. aureus from wounds of known cause 75% were from lesions caused by bone. In one outbreak streptococcal infection was seen principally in newly-employed staff. Group L streptococci were found in several sites in the pork factory and were isolated from infected lesions in two workers. Strep. pyogenes and Staph. aureus were cultured from tap handles in the lavatories.

Sixty-six workers were examined in a non-epidemic period and 59 % were found to have current wounds on the hand or wrist; 13% of wounds were infected but Strep. pyogenes was not isolated. Bone was the commonest of the many causes of injury, accounting for 31 % of all wounds. Butchers had the highest rates of wounding and most bone-inflicted injury was seen in this group. Packers were the only group to wear protective gloves regularly. Damaged fingernails were found in 50% of workers, including a high proportion of nail-biters (33% of all workers). The epidemic strain of Staph. aureus was cultured from bitten fingernails. Three of four infected workers carrying epidemic organisms in the throat were examined and all were nail-biters. Sharp-edged bone was produced by rotary saws early in the production line and bone dust contaminated the carcasses and adjacent surfaces. It is suggested that bone fragments could contaminate wounds and that this might have implications for the initiation of infection and the development of outbreaks.

A survey conducted in 1980, 9 years after the banning of the use of tetracyclines as feed additives in the U.K., indicated that table chickens and pigs were still a large reservoir of tetracycline-resistant Escherichia coli; the incidence of transferable tetracycline resistance was greater in chicken E. coli strains (68%) than in pig E. coli strains (20%). Large amounts of sulphonamide-resistant and of furazolidone-resistant E. coli were found in the faeces of chickens; E. coli resistant to both sulphonamides and streptomycin were common in the faeces of chickens and pigs. E. coli with transferable or mobilizable trimethoprim resistance were present in the faeces of most pigs and in the faeces of 10 % of chickens.

The incidence of Vibro parahaemolyticus in products of the Malaysian export shrimp processing industry was investigated through the stages from the catch to that of the cooked, peeled and frozen product. The organism was commonly found in freshly caught and landed shrimp, and could be detected by enrichment culture at all stages of processing. The numbers of V. parahaemolyticus in shrimp varied from nil to 4 × 104, and 19 of the 50 serotypes in the current antigenic scheme were found, O1-K38 and O1-K32 occurring most often. All the isolates were Kanagawanegative; one strain was a sucrose-positive variant. The study indicated that specifications of 102 g−1 for V. parahaemolyticus in raw tropical shelfish are too stringent but that the Malaysian shrimp industry should be able to meet this requirement for cooked shrimp.

The India-ink Immuno-reaction (IIR) was used as a simple, convenient procedure for the detection of carriers of enteric organisms in an unselected sample of patients attending a mission clinic at Kubacha in a remote area of Kaduna State, northern Nigeria. To assess the reliability of this procedure in difficult working conditions a similar population from the same clinic was subsequently examined by routine bacteriological culture techniques. Because of a temporary shortage of suitable anti-sera we were unable also to examine specimens from this second group by IIR.

A further group of patients attending the out-patients clinic of the General Hospital in Kaduna with symptoms of acute enteric disease was investigated using both IIR and routine culture.

Proportionally more positive results were obtained for Salmonellae, Shigellae and Vibrios with IIR than with routine culture. A larger scale controlled survey is desirable to evaluate the procedure further.

Small numbers of Salmonella dublin were used to infect calves in an attempt to simulate natural infection on the farm.

Twenty calves were exposed to S. dublin by one or more of the following methods:

Sucking cows which were excreting S. dublin in their faeces (⋜ 102–105 organisms/g).

Housing on S. dublin contaminated bedding.

Drinking S. dublin contaminated water (102–104 organisms/ml). During this experiment some calves were given therapeutic doses of oxytetracycline.

After exposure the calves were examined for faecal excretion of S. dublin (in some instances mouth swabs and blood samples were also examined) and for clinical signs of illness. Most of the calves became infected with S. dublin but excretion was usually sporadic and the numbers of salmonellas excreted were small. No clinical signs of salmonellosis were observed by S. dublin was isolated from one calf at post-mortem.

Another six calves, dosed orally with either 106 or 108S. dublin, showed signs of mild illness and although three calves had diarrhoea excretion of salmonellas was intermittent. S. dublin was isolated from one of these calves at post-mortem.

An investigation was undertaken to see if cooking or cold storage would destroy or decrease the level of biologically active antibiotic in tissues from animals given therapeutic doses of antibiotic on three occasions prior to slaughter. The effects of cooking and cold storage on the biological activity of the residues of ampicillin, chloramphenicol, oxytetracycline, streptomycin and sulphadimidine were varied; in some instances the effects were minimal, in others nil.

In August, 1980 a rare serotype S. zanzibar was isolated in the North of Scotland from a man home on leave from Malaysia, whence he returned in November having been bacteriologically negative 2 months previously. In December however, S. Zanzibar was isolated from a bulk milk sample taken at a nearby dairy farm. No illness occurred among milking cows which had been brought inside from pasture in mid-October. Since 1972 a variety of different salmonella serotypes had been identified in cattle, milk and other samples at this farm, with seagulls being implicated as the vector transmitting infection from the sewage of a local town on to farmland and an adjacent loch. Although water from this source has not been used in recent years for drinking by cattle, it is utilized for washing floors within the dairy premises. Since 1979, following an outbreak affecting consumers, all milk produced at the farm has been pasteurized.