The epidemiology of bacterial infection is investigated by the use of identification procedures at a sub-species level by such techniques as serotyping, phage typing, various antigen recognition tests, plasmid profiling and DNA probes. Fungal epidemiology has tended to lag behind in the use of this technology, particularly with the filamentous fungi, though several techniques have been developed for yeasts and especially for Candida albicans. This review will briefly describe the application of these methods to outbreaks of C. albicans infection, describe the limited methods available for the investigation of filamentous fungal infection and indicate the necessity for increased research in this area.

Samples of ground beef (225), pork (235) and chicken (200) were randomly selected from meat processing plants in the southwestern Ontario area. Supernatants of broth cultures of the samples were tested for verocytotoxins using a Vero cell assay. Neutralization of cytotoxic activity using antisera specific for three types of verocytotoxin (Verotoxin 1, Verotoxin 2 and Shiga-like toxin II) was performed on positive samples. Isolation of verocytotoxigenic Escherichia coli (VTEC) was attempted from positive samples. VTEC were confirmed as E. coli biochemically, tested for drug resistance, and serotyped. Based on neutralization studies, the prevalance of VTEC in beef and pork was at least 36·4% and 10·6%. respectively. This is much higher than has been reported from a survey of retail meats in which a method designed to detect only E. coli O 157.H7 was used. Isolations of VTEC were made from 10·4 % of the beef samples and 3·8 % of the pork samples. No VTEC were recovered from the chicken samples. The majority of VTEC isolates were susceptible to commonly used antimicrobial agents. A number of the serotypes of the VTEC isolates recovered have been associated with human disease; however, no VTEC of serotype O 157.H7 were isolated.

Over the past 5 years Salmonella enteritidis infections in humans have increased on both sides of the Atlantic ocean. The WHO salmonella surveillance data for 1979–87 were reviewed and show that S. enteritidis appears to be increasing on at least the continents of North America, South America, and Europe, and may include Africa. S. enteritidis isolates increased in 24 (69%) of 35 countries between 1979 and 1987. In 1979, only 2 (10%) of 21 countries with reported data reported S. enteritidis as their most common salmonella serotype; in 1987, 9 (43%) of 21 countries reported S. enteritidis as their most common serotype; 8 (89 %) of 9 were European countries. Although the reason for the global increase is not yet clear, investigations in individual countries suggest it is related to consumption of eggs and poultry which harbour the organism.

During the 3-year period 1985–7, all strains of Shigella sonnei isolated in Catania, Sicily, showed a high level of resistance to trimethoprim (Tp) which was invariably associated with resistance to other antibiotics.

Plasmid analysis showed 18 different electropherotypes: 35 of 37 strains harboured a plasmid of 70 Megadaltons (MDa), and 29 of 37 strains a plasmid of 130 MDa.

Restriction endonuclease fingerprinting of purified 70 MDa plasmid DNA from different strains demonstrated that these plasmids were similar but not identical.

In some strains with transferable Tp resistance, DNA hybridization analysis demonstrated the presence of genes coding for the production of dihydrofolate reductase (DHFR) type V. In contrast, there was no detectable hybridization with DNA probes specific for genes coding for DHFR types I, II and IV. This is the first report of the DHFR type V gene outside Sri Lanka.

The epidemiological data on shigellosis in Teknaf, a coastal area of Bangladesh, were reviewed for a 10-year period (1975–84). Certain similarities and differences were observed in the epidemiology of the disease in Teknaf when compared with urban Dhaka and rural Matlab. Similarities included: round-the-year infection with two peaks, one in the monsoon period and the other in the winter period; high male to female attendance ratio at the treatment centre: the predominance of infection in the under-15-year age group; high mortality rate in the under-5-year age group of both sexes and in females of all age groups; the multiple drug resistance of organisms. Differences included the higher isolation rate of organisms in Teknaf (42·1 % as against 11–12% in Dhaka and Matlab) and the preponderance of Shigella dysenteriae 1 infection in females in Teknaf. The unusually high isolation rate of shigella makes Teknaf the area with the highest incidence of shigellosis in Bangladesh.

Shigellosis is endemic in Central Australia and the infections are predominantly due to Shigella flexneri 6, Shigella flexneri 2a and Shigella sonnei. Plasmid profiles of isolates collected from 1985–9, suggested that infections caused by Shigella flexneri 6 were predominantly due to a single clone, whereas those caused by Shigella flexneri 2a and Shigella sonnei were due to several genetically diverse strains, although strains with identical plasmid profiles were found in widely separated geographical areas and in different years.

In an epidemiological survey, plasmid profiles and antimicrobial susceptibility testing of 100 shigella isolates in Lagos, Nigeria was done. All the isolates were sensitive to nalidixic acid, nitrofurantoin and ciprofloxacin. The commonest antimicrobial susceptibility pattern was resistance to ampicillin, colistin sulphate, co-trimoxazole, streptomycin and tetracycline. All but 4 of 100 isolates screened contained one or more plasmids. Plasmid profile analysis distinguished more strains than did antimicrobial susceptibility patterns. A total of 36 isolates was able to transfer resistance plasmids to Escherichia coli K-12 by conjugation. Using in vitro transformation, seven isolates transferred resistance. These plasmids specified resistance to tetracycline, streptomycin, sulphonamide, trimethoprim and ampicillin.

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.

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.

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.

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.

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.

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.

From 1979 to August 1987, there have been 178 cases of meningococcal disease in Iquique, Chile, a city of about 140000. The attack rate for the last 5 years has been in excess of 20/100000 per year, more than 20 times greater than for the country overall. The mortality rate was 6%. The disease occurred in patients with ages from 4 months to 60 years, but 89% of cases were in patients <21 years. The largest number of cases were in the age group 5–9 years (n = 54), but the highest incidence occurred in children less than 1 year of age (72·8/100000 per year). The male/female ratio was 1·2. Cases occurred all year round with little seasonal variation. Of the 178 cases, 173 were biologically confirmed. Serogroup analysis of strains from 135 patients revealed A = 1, B = 124, C = 10. Forty-four group B strains from 1985–7 were serotyped: 15:P1.3 = 36, 15:NT = 4, 4:P1.3 = 2, NT:NT = 2. Ten of 11 of the outbreak strains tested were sulfadiazine-resistant. This is the first recognized outbreak caused by a Gp B:15 strain in South America. It shares many of the characteristics of outbreaks caused by closely related strains in Europe, such as a predilection for older children and adolescents, sulfadiazine-resistance, and sustained high attack rates. The Iquique strain (B:15:P1.3) belongs to the same genetic clone (ET-5 complex) as the Norway (B:15:P1.16) and the Cuban (B:4:P1.15) strains.

Forty-two cultures of pseudomonas comprising 28 clinical isolates from a pseudo-outbreak on a Special-Care Baby Unit and 14 reference strains, including 9 type strains, of various Pseudomonas 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 for a numerical analysis which divided the strains into 9 phenons. Two of the 28 clinical isolates were identified by biochemical tests as P. pickettii and their identification was confirmed by SDS–PAGE as they fell in the same phenon as the type strain of the species. The remaining 26 isolates, which could not be identified on phenotypic tests, fell in the same phenon as three reference strains of ‘P. thomasii’. The protein patterns provided the first clear evidence that P. pickettii and ‘P. thomasii’ were separate taxa and that the ‘outbreak’ was polymicrobial in origin, in line with the probable aqueous source of contamination. We conclude that high-resolution SDS–PAGE of proteins provides an effective method of identifying and differentiating pseudomonads, especially where this cannot be done adequately using conventional biochemical tests.

Prospective epidemiological studies of beach water pollution were conducted in Hong Kong in the summers of 1986 and 1987. For the main study in 1987, a total of 18741 usable responses were obtained from beachgoers on nine beaches at weekends. The study indicated the overall perceived symptom rates for gastrointestinal, ear, eye, skin, respiratory, fever and total illness were significantly higher for swimmers than non-swimmers; and the swimming-associated symptom rates for gastrointestinal, skin, respiratory and total illness were higher at ‘barely acceptable’ beaches than at ‘relatively unpolluted’ ones. Escherichia coli was found to be the best indicator of the health effects associated with swimming in the beaches of Hong Kong. It showed the highest correlation with combined swimming-associated gastroenteritis and skin symptom rates when compared with other microbial indicators. A linear relationship between E. coli and the combined symptom rates was established. Staphylococci were correlated with ear, respiratory and total illness, but could not be used for predicting swimming-associated health risks. They should be used to complement E. coli. The setting of health-related bathing-water quality standards based on such a study is discussed.

Twenty progesterone-treated TO mice were infected intravaginally with Mycoplasma pulmonis. One month later, ten of the mice were given oestradiol which changed the reproductive cycle to the oestrous phase and within a week resulted in eradication of the organisms from six of them; vaginal persistence in the other mice may have been due, at least in part, to reinoculation of organisms from the oropharynx, a site heavily infected in all the mice. The majority of the mice not treated with oestradiol continued to shed the organisms from the vagina for at least 91 days. In another experiment, 19 oestradiol-treated BALB/c mice were infected intravaginally with M. hominis. One month later, nine of the mice were given progesterone which changed the reproductive cycle to the dioestrous phase and eradicated the organisms from seven within 2 weeks and from all of them within about a month. This was in contrast to the mice not given progesterone, the majority of which continued to shed the organisms for at least 167 days.

The Oxford panel of monoclonal antibodies was used to subtype 83 strains of Legionella pneumophila serogroup 1 of human and environmental origin. The International panel was also used to subtype 50 of them. All the 18 patients' isolates were of the Pontiac subgroup, and 40/43 of the environmental strains of the Pontiac subgroup were associated with human infection. The remaining environmental strains were subgroups Olda (15 strains), Camperdown (5 strains), and Bellingham (2 strains). The Philadelphia subgroup was the commonest among the environmental strains tested with the international MABs panel.

This study confirms previous findings that L. pneumophila serogroup 1 isolates with the Pontiac (Oxford panel) or MAB-2 (international panel) reacting antigen marker seem to be more virulent than the other subgroups.

Serum samples from individuals of a wide age range, collected in northwest England in 1984 and 1986, provide the basis for an analysis of the epidemiology of mumps virus infection. A radial haemolysis test yielding quantitative antibody measurements was used to screen samples for mumps-specific IgG. Analyses of resultant age-seroprevalence profiles, using statistical models, revealed an age-related pattern in the rate of infection per susceptible similar to that observed for other childhood infections. This rate, or force of infection, was low in young children, high in older children, and low in adults. In addition, the serological surveys provide evidence for time-dependent changes (both epidemic and longer-term) in the rate of mumps virus transmission. The longer-term changes, reflected in the pattern of the age-acquisition of specific antibodies, are supported by evidence from case notification data. The implications of temporal changes in incidence to the interpretation and design of serological surveys are considered.

Two DNA clones were obtained from faecal specimens containing a parvovirus-like small round virus from a 1977 outbreak of gastroenteritis, and their nucleotide sequences were determined and found to be essentially identical with parts of the published sequence of serum parvovirus B19 and with a B19 isolate (JB) partially sequenced in this study. The clones corresponded mainly to genome regions coding for non-structural proteins, but also include a sequence of some 160 bp coding for structural proteins. Southern blotting experiments with a full-length B19 probe revealed a virion-sized 5·5 kbp DNA band in specimens from gastroenteritis cases in both 1977 and 1986. Thus the nucleotide sequence and hybridization results suggest that the virus seen in these studies is very similar to B19. Further work is necessary to clarify the antigenic relationship of these viruses.