In Canada, the number of human isolates of verotoxigenic (VT +ve) Escherichia coli 0157:H7 from diarrhoeal cases and haemolytic uraemic syndrome and haemorrhagic colitis has increased from 25 in 1982 to 2384 in 1989. A total of 3273 VT + ve E. coli 0157:H7 strains (3255 strains isolated in Canada and 18 isolates from other countries) were phage typed. The phage typing scheme has been extended from 14 to 62 phage types. Of these, five types occurred exclusively in other countries (type 47 in Japan; and types 49, 50, 51 and 52 in the U.K.). Thirty-five different phage types were identified in Canada; only nine of these (1, 2, 4, 8, 14, 21, 23, 31 and 32), each accounted for more than 1 % of the cases from human sources. The same nine types were the only ones observed among the isolates from non-human sources (meat and slaughter houses) suggesting a food-borne transmission in most of the human cases. Phage types 1 (30·5%); 4 (21%); 8 (13·5%); 31 (8·9%) and 14 (8%) were encountered in varying frequencies in most of the provinces; infrequently occurring phage types also showed regional variation. Thirteen different phage types were identified among 151 outbreaks representing 556 isolates of E. coli 0157:H7. More than one phage type were encountered in 12 outbreaks whereas in 141 outbreaks, all strains in each, had the same phage type.

Plasmid profile analysis by agarose gel electrophoresis was carried out on 37 drug-resistant strains of Shigella dysenteriae types 2, 3, 4, 6 and 7. These strains were collected between 1976 and 1985 in Addis Ababa, Ethiopia.

The plasmid profile of S. dysenteriae type 2 strains with R-type CSSuT did not show middle-sized plasmids likely to code for CSSuT resistance. All strains contained a large plasmid of about 120 megadaltons (MDa), and a cryptic plasmid of about 2·2 MDa. The plasmid profiles of S. dysenteriae type 3 with R-types ACSSuT, SSuT and SSu showed a 4·2 MDa SSu-determinant, which was demonstrated in Escherichia coli K12 recipients resulting from triparental crosses. The ACT determinant in S. dysenteriae type 3 with R-type ACSSuT is probably chromosomally mediated. Cryptic plasmids of about 3·0 and 2·2 MDa were found in all S. dysenteriae type 3 isolates. The 4·2 MDa plasmid featured prominently in the plasmid profiles of S. dysenteriae types 4, 6 and 7 with R-types SSuT and SSu. However, this plasmid was not mobilizable by triparental crosses. There was a relative paucity of transferable plasmids in non-Shiga bacillus isolates. However, incompatibility group N plasmids, coding for tetracycline resistance, were detected.

Reproducible and discriminating typing methods are required for epidemio-logical investigations. Numerical typing systems analyse patterns obtained in various ways by calculating similarity coefficients between isolates. In the present study, various measures of the efficiency of a numerical typing system are quantified. These include reproducibility, accuracy, and discrimination power.

Three different numerical typing methods for Escherichia coli were compared using these measures: (a) Biotyping with API 50 CH system, (b) Biochemical fingerprinting with the API 50 CH system and (c) Biochemical fingerprinting with the PhP-EC system. Biotyping qualitatively measures the results of a set of biochemical reactions as + or −. Biochemical fingerprinting also uses biochemical reactions, but the tests are scored quantitatively by measuring the kinetics and intensity of each reaction.

It was found that biotyping yielded poor reproducibility. When biochemical fingerprinting analysis was used with the API 50 CHE system the reproducibility and the discrimination was good. The PhP-EC system for biochemical fingerprinting showed equal reproducibility but was superior to the API 50 CH system with regard to discrimination power.

Salmonellas were detected in the environment of 10 of the 12 calf dealers' premises studied. The cleaning and disinfection routines were often ineffective and salmonellas were isolated from 7·6 % and 5·3 % of the wall and floor samples before disinfection and 6·8% and 7·6% afterwards. Eight different salmonella serotypes were detected, of which the commonest were Salmonella typhimurium, predominantly phage type DT204C, and S. dublin. Plasmid profiles were used to fingerprint S. typhimurium DT204C and the results indicated that with the exception of one of the premises, prolonged salmonella-persistence in the environment was not occurring.

Three separate epidemics of salmonellosis in calves were studied by use of plasmid profile analysis. The results illustrated the role of dealers, and their subcontractors, in the dissemination of salmonellas. The study concludes with suggestions for methods to reduce the spread of salmonellas in the calf marketing chain.

A case-control study aimed at comparing the incidence of campylobacter infection with that of other enteropathogens in infants was performed in Oran, Western Algeria. During a one-year period, infants consulting in a health centre were included if they had acute diarrhoea. The controls comprised infants going to the same centre for vaccination. Butzler medium Virion was used to look for thermophilic campylobacters. Campylobacters were isolated in 17·7% of the 411 patients and in 14·9% of the 247 controls. No statistically significant difference was found after stratification by age. In contrast, other enteropathogenic bacteria were rarely present. Among the potential factors of clinical expression of infection, breast feeding appeared to have a protective effect which was higher for campylobacter diarrhoea than that observed for other causes of diarrhoea. These data contrast with those previously published in Bangladesh and could be an incentive for promoting breast feeding in this country, where the tradition is decreasing far below the standard which is generally accepted.

Biochemical reactions, using the PhP-EC system of biochemical fingerprinting, were evaluated in order to group strains into different clusters and to investigate whether a biochemical typing system may be used to distinguish between randomly selected Escherichia coli strains obtained from bacteraemic patients and healthy controls. Fifty epidemiologically unrelated strains isolated from blood of non-diabetic patients and 46 faecal control strains were studied. Separately, 70 E. coli strains from 64 diabetic patients with bacteraemia were investigated. Diversity index was 0·977, 0·969 and 0·941 respectively. The strains were clustered at a similarity level of 0·95. The bacteraemic and control strains were subdivided into 14 different clusters with 2–12 strains each and 40 ‘outliers’. The largest cluster was dominated by bacteraemic strains (9/12, 75%). Two other clusters were dominated by control strains. In the remaining groups blood and faecal isolates were evenly distributed. No biochemical test was able to distinguish between bacteraemic and faecal control strains. Strains from patients with diabetes mellitus were grouped in 11 clusters containing 2–14 strains and 22 ‘outliers’. The low diversity index of bacteraemic strains obtained from diabetic patients as compared to other strains indicated a greater homogenicity. However, no correlation was observed between the examined host factors and the clusters.

An epidemiological survey was conducted on two commercial turtle farms in southern Louisiana to determine the reason for an apparent increase in the prevalence of Salmonella spp. in turtle hatchlings at the time of pre-export certification examination.

Pond water was consistently found to be contaminated (6/36 samples) with either Salmonella newport, S. arizonae, or S. poona. Environmental specimens obtained from eggs and turtle hatcheries (204 specimens) failed to yield Salmonella spp. A sample comprising 197 hatchlings, derived from a batch previously demonstrated to be contaminated, showed a salmonella prevalence of 12%, with S. arizonae and S. poona the only serotypes isolated. Four serotypes of Salmonella sp. isolated by a certifying laboratory in 1988, and 20 salmonella isolates obtained from hatchling turtles, were all resistant to gentamicin. The emergence of gentamicin resistance in Salmonella spp. isolated from turtles will reduce the effectiveness of preventive measures in use in Louisiana since 1984.

Thirty-eight Salmonella typhimurium strains isolated from December 1987 to March 1988 in Isernia, Central Italy, were characterized on the basis of their phage type, resistance to antimicrobials and plasmid profiles. According to their phage types, the isolates could be assigned to one of six groups, the prevalent one being PT 195 which accounted for 73·6% of isolates.

On the basis of their plasmid content, the isolates could be assigned to one of ten groups. The prevalent plasmid profile (60·0; 6·0; 4·3; 4·0; 3·2 megadaltons) was found in 60·4% of isolates.

All the isolates from a particular food (salsicce), and as most of isolates from humans who had consumed this food belonged to phage type 195 and were of the same plasmid profile.

The combined use of phage typing and DNA plasmid analysis proved to be a useful tool in identifying epidemiologically related isolates in this investigation.

Two Australian isolates of Treponema hyodysenteriae which did not fit within the current serological grouping system for these bacteria wrere examined by agarose gel double immunodiffusion tests (AGDP). Isolate Vic1 was serologically unique, and we propose that it becomes the type organism for a new sixth serological group of T. hyodysenteriae (Group F). Isolate Q1 was unusual in that lipopolysaccharide (LPS) extracted from it reacted strongly in AGDP with serum raised against the type organism for serogroup D (A1), and also weakly with serum raised against the type organism for serogroup B (WA1). The nature of this cross-reactivity was examined by using cross-absorbed antisera in AGDP, and by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analysis.

The pattern of serological cross-reactivity between Q1, A1 and WA1 was complex and was not fully defined, but the isolate Q1 apparently shared low molecular weight ‘serogroup’ LPS antigens with A1, and shared higher molecular weight LPS antigens with WA1. On this basis Q1 was designated as belonging to serogroup D, although it was recommended that this be qualified as D (B) to indicate the presence of weak cross-reactivity with serogroup B. Such serological cross-reactivity may have significance in relation to the development of immunity to T. hyodysenteriae. Isolate Q1 may be a potentially useful organism for vaccine development because of its ability to induce a good serological response to LPS of treponemes from both serogroups D and B.

Variation amongst Achromobacter-like strains was examined by DNA restriction endonuclease digestion and rDNA gene patterns generated using a non-radioactive probe. Chromosomal DNA was extracted from 12 cultures representing Achromobacter groups B, E and F, all from human blood cultures. DNA fingerprinting using EcoRI, HaeIII or HindIII sub-divided the strains in a similar manner to that obtained by their protein patterns. The HaeIII patterns, with their small number of bands, were the easiest to interpret. The EcoRI patterns included a species-specific triplet of bands but minor band patterns allowed further differentiation. The Achromobacter group F strains comprised a separate taxon and were distinct from the group B and E strains by all techniques examined. The study demonstrates that, in addition to total DNA digest analysis, rDNA gene restriction patterns provide a simple but discriminatory electrophoretic method for distinguishing within Achromobacter groups B and E.

The blood culture records during the 6-year period 1984–9 were reviewed to compare the performance of the BACTEC aerobic (6B) and aerobic-hypertonic (8B) media for the recovery of Candida spp. and Torulopsis glabrata from blood. There were 137 positive blood culture sets that contained both a 6B and an 8B bottle. Sixty-eight different yeasts were recovered from 65 patients including 35 Candida albicans, 19 C. tropicalis, 6 C. parapsilosis, 4 C. krusei, 1 C. pseudotropicalis and 3 Torulopsis glabrata. The 8B medium detected 120 of the positive cultures (87·6%) and was the only positive medium in 35 (25·6%) sets, while the 6B medium detected 102 positive cultures (74·4%) and was the only positive medium in 17 (12·4%) sets (P < 0·04). For those sets in which both bottles were positive, radiometric detection occurred first in the 8B bottle in 39 sets and first in the 6B bottle in 11 sets (P < 0·001). The superior performance of the 8B bottle was not related to the administration of amphotericin B. Cultures of stock strains of C. albicans, C. tropicalis, and C. parapsilosis in 6B and 8B media with and without added blood confirmed the finding that 8B was substantially superior to 6B for the detection of candidaemia. It is concluded that an 8B bottle should be included in the blood culture set whenever candidaemia is suspected.

Certain strains of group A streptococci are known to bind IgA and/or IgG via a cell surface receptor, which may act as a virulence factor. The distribution of such receptors among routine clinical isolates was studied, using a total of 225 strains and an assay based on the binding of radiolabelled immunoglobulins. Among 194 throat strains isolated during three different time periods in two different geographical areas of Sweden, 82% showed significant binding of IgA and/or IgG. Studies on 31 septicaemia strains, isolated over a period of more than 8 years, showed binding for 84% of the isolates. The binding strains were of several different T-types and could be subdivided into two groups, those binding both IgA and IgG and those binding IgG only. These data show that binding of IgA and/or IgG is a very common property among clinical isolates of group A streptococci.

Infection with potential bacterial enteropathogens was studied prospectively in 94 Swedish travellers. Three faecal samples were collected, regardless of diarrhoeal symptoms, after each of three 1-week stays in Singapore, Hong Kong and Japan. The specimens were analysed for salmonella, shigella, yersinia, campylobacter and different enterotoxin-producing bacteria. A potential enteropathogen was identified in 30% (28/94) of the participants, i.e. in 26% of the healthy and in 39% of the travellers with diarrhoea. The most common isolates were enterotoxigenic bacteria of different species (14%), salmonella (11%) and campylobacter (7%). By performing enterotoxin-tests on six different colonies from the primary culture of each specimen enterotoxigenic Escherichia coli (ETEC) as well as enterotoxin-producing Klebsiella sp., Citrobacter sp. and Morganella morganii were identified. The latter strains were as prevalent as ETEC. In the 33 participants with diarrhoea enterotoxigenic bacteria (18%) and campylobacter (18%) were the most common isolates. Campylobacter-infected travellers developed symptomatic disease (6/7) significantly (P>0·02) more often than those infected with salmonella (3/10) or enterotoxigenic bacteria (6/13; 2 ETEC, 4 other species).

This paper reviews epidemiological data to see if there are sex differentials in prevalence, density and clinical pathology due to lymphatic filariasis. Of 53 studies from Africa, South East Asia, the Indian Subcontinent and The Americas, 43 showed a lower mean prevalence of infection in females than in males. Prevalence is consistently lower in women of reproductive age and this is statistically significant in 16 of 32 studies classified by age and sex. Density of infection is also lower in the reproductive age but may be higher in children and in older women. Clinical disease is also lower in women and pathology has a later age of onset and rise to peak prevalence than in males. The paper assesses the evidence that lower rates of infection and clinical pathology are due to less exposure of females to infective vectors. It seems unlikely that exposure alone could account for these differences which are observed for both bancroftian and brugian filariasis, irrespective of periodicity. Several investigators have suggested that females have increased resistance to infection and this is supported by serological studies showing high antibody positivity to adult worm antigens in females. The review concludes that the association with the reproductive years suggests a pregnancy-associated mechanism. This has important implications for maternal – fetal interactions and maternal filarial infection may influence the development of immunity in children.

Drug-resistant coagulase-negative staphylococci (DRCNS) in orthopaedic patients and ward staff were studied. A significant increase in the DRCNS carriage rate was observed among the 16 patients studied after 14 days of hospitalization with levels approaching that of the staff. Patients receiving dicloxacillin prophylaxis (n=9) were more likely to be colonized with methicillin-resistant CNS, while patients receiving no antibiotics (n= 7) became to a larger extent colonized with multiple DRCNS. The combined data from species determination, biochemical, plasmid, and antibiogram typing revealed a considerable diversity among DRCNS;64 types were distinguished among 112 DRCNS isolates selected for study after exclusion of apparently duplicate isolates. Plasmid plus antibiogram typing yielded almost as many types (61); whereas species determination plus antibiogram distinguished only 33 types. Although a novel computerized 96-reaction boityping method alone enabled differentiation of 17 biotypes, most DRCNS isolates belonged to one of three major biotypes limiting the usefulness of this method. Ten of the 64 (16%) DRCNS types identified comprised 50 of the 112 (45%) isolates. These were isolated from staff and from patients on day 14, suggesting a nosocomial origin.

Neisseria cuniculi was isolated, between March 1987 and March 1989, from 38 cases of respiratory disease in small and large ruminants. In all but five cases N. cuniculi was cultured together with other potential respiratory pathogens. A survey was conducted to assess the prevalence of N. cuniculi in the pharyngeal region of Merino and Awassi purebred sheep, Awassi/East-Friesian and Merino/Romanov crossbred sheep and one exotic cross breed (goat/ibex).

N. cuniculi was isolated from 80–88% of the animals under 1 month of age. Among older animals, the microorganism was isolated from 20·5% of the pure bred animals and 79·3% of the crossbred ones. This difference was significant (P < 0·001) by the χ2 test. The prevalence of N. cuniculi in the second age group coincides with the susceptibility of the breeds to respiratory pathology.

This, we believe, is the first report of N. cuniculi involved in multiple cases of respiratory pathology and of a survey assessing the prevalence of this microorganism in small ruminants.

Twenty-five cultures comprising 18 clinical isolates of Serratia marcescens from two hospitals, the type strain of S. marcescens, two reference strains of S. marinorubra, the type or a reference strain of three other Serratia species and a reference strain of undetermined species, were characterized by one-dimensional sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE) of whole-cell proteins. The protein patterns were highly reproducible and were used as the basis of a numerical analysis which divided the clinical isolates into eight protein types. Comparison with O-serotyping indicated that the level of discrimination by SDS–PAGE was similar. As with O-serotyping, a secondary scheme, such as phage typing, is necessary to differentiate strains of the same protein type. We conclude that high-resolution SDS–PAGE of proteins provides an effective adjunct to other methods for typing isolates of S. marcescens.

In studies concerning the effect of antibiotics on faecal microflora, Colonization Resistance is an important parameter. Colonization Resistance correlates inversely with the number of different biotypes of Enterobacteriaceae isolated from faecal samples. Nine healthy volunteers were studied during 6 weeks, in order to determine the natural variation in the number of different biotypes of Enterobacteriaceae per faecal sample. The numbers of biotypes ranged from 1–15 per faecal sample, the mean number of biotypes varied between 2·6 and 7·3 different biotypes per faecal sample per healthy volunteer. Inter-individual variations of five biotypes in the mean number of biotypes per faecal sample are normal. We assessed the minimal number of faecal samples that should be taken for comprehensive biotyping so as to determine reliably the mean number of different biotypes representative for the Colonization Resistance of an individual. It was found that a minimum of four faecal samples was required.

Evidence of past zoonotic infection was investigated serologically in randomly selected Northern Ireland farmers. The percentage of farmers with antibody was: Brucella abortus (0·7), Leptospira interrogans serovars (8·1), Borrelia burgdorferi (14·3), Toxoplasma gondii (73·5), Coxiella burnetii (28·0), Chlamydia psittaci (11·1) and Hantavirus (1·2).

The results show that Northern Ireland farmers have been exposed in the past to zoonotic infections. It is not known if these infections contributed to ill health in farmers but it is now time for the health of farm workers and their medical services to be reassessed.

In the search to find discriminative serological markers to differentiate between patients with acute brucellosis and those with chronic brucellosis, an enzyme-linked immunosorbent assay (ELISA) was used to determine and compare the brucella-specific IgE response in 80 sera from patients with acute brucellosis, 37 sera from patients with chronic brucellosis, 26 sera from patients with positive blood cultures for bacteria other than brucella and 51 sera from healthy controls. The IgE findings were compared to brucella-specific IgG, IgM, IgA and IgG1–4 demonstrated by ELISA, and to microagglutination test (MAT) results. Elevated (positive) antibrucella IgE titres were detected in 89 and 81 % of sera from patients with acute and chronic brucellosis respectively. The predominant antibodies found in patients with acute brucellosis were of the IgG, IgM, IgA, IgE, IgG1 and IgG3 types while in chronic brucellosis IgG, IgA, IgE and IgG4 were found. Although IgE can be detected in patients with brucellosis, it does not discriminate between the acute and chronic stages of the disease.