William Norman Pickles (1885–1969) was, for most of his life, a general practitioner in the village of Aysgarth, Wensleydale in the North of England, a relatively remote area in the early part of this century with many of the doctors' visits made on horseback or on an ancient motorcycle. The story of Pickles' life, how he became, among other honours, the first President of the Royal College of General Practitioners, is told in Pemberton's book Will Pickles of Wensleydale. It may seem curious that Pickles, a country GP, should rank with other great men in epidemiology: Jenner who worked on smallpox, Budd on typhoid fever, Snow on cholera, yet it was the remoteness of his practice combined with his own acute observation and accurate recording that enabled him to contribute so significantly to epidemiology.

The genetically determined inability to secrete the water-soluble glycoprotein form of the ABO blood group antigens into saliva and other body fluids is a recognized risk factor for meningococcal disease. During a community-wide investigation of a prolonged outbreak of disease due to a B15: P1.16 sulphonamideresistant strain of Neisseria meningitidis in Stonehouse, Gloucestershire (the Stonehouse survey), the ABO blood group and secretor status of almost 5000 residents was determined.

The proportion of non-secretors in the Stonehouse population was significantly higher than the proportion of non-secretors among blood donors in the South West Region and in England generally. Seven of 13 Stonehouse residents with meningococcal disease who were tested were found to be non-secretors, a high proportion. The outbreak in Stonehouse cannot be explained solely in terms of the increased proportion of non-secretors. There was no clear correlation between the proportions of non-secretors in different areas within the town and the incidence of cases of meningococcal disease.

Carriers of meningococci, whether outbreak or other strains, were not more likely to be non-secretors. The reasons why non-secretors are more susceptible to meningococcal disease remain to be determined, but they do not appear to be related to carriage of meningococci.

Cryptococcosis is not a commonly diagnosed disease. Records of its occurrence in Britain are virtually non-existent before 1945. when the Mycological Reference Laboratory (MRL) of the Public Health Laboratory Service was first established

Epidemiology in Country Practice by William N. Pickles, published in 1939, has been a source of continuing interest and challenge especially to general practitioners (Watson, 1982; Booth, 1987). Pickles worked for over 50 years as a general practitioner (GP) in rural Wensleydale where there were many isolated villages in which natural immunity against various infections was often lacking. And so the source of infection could usually be traced, and, with little or no immunity, spread was often rapid.

One hundred and nine strains of Haemophilus influenzae type b were subtyped by sodium dodecyl sulphate polyacrylamide gel electrophoresis of whole-cell polypeptides. Twenty-one strains from England, 44 from Scotland, 8 from Sweden, 6 from the Netherlands and 30 from the USA were examined. Some of these strains had been subtyped by outer membrane protein analysis; most of the strains had been isolated from cases of invasive disease.

Comparison of polypeptide profiles using the Dice coefficient of similarity showed that the majority of European strains were closely related and formed a single large group. Four smaller groups were identified; three of these included American and European strains, indicating a world-wide distribution of subtypes. However, the common European and American subtypes fell into different groups, indicating the existence of marked geographical variations in subtype frequency.

The predominance of coagulase-negative staphylococci as normal skin flora is thought to be a factor in their association with episodes of peritonitis in patients undergoing continuous ambulatory peritoneal dialysis. We investigated the prevalence of peritonitis-associated strains on the skin of 28 patients undergoing peritoneal dialysis. Coagulase-negative staphylococci were the most frequently isolated organisms. comprising 47% of peritoncal dialysis fluid isolates and 59% of body site isolates. A total of 142 coagulase-negative staphylococci were speciated. tested for their antimicrobial sensitivity and slime production. and identified by phage typing and plasmid-profile analysis. Staphylococcus epidermidis was the most commonly identified species from both peritoncal dialysis fluid (73%) and body sites (53%). Multiple antibiotic resistance was common, and the greater proportion of isolates were resistant to methicillin: 63·6% of peritoncal dialysis fluid isolates and 61·7% of body-site isolates.isolates. S. haemolyticus isolates were significantly more resistant to methicillin than other species. By phage typing and plasmid-profile analysis it was shown that peritonitis was rarely caused by skincolonizing strains. In only 3 of 14 patients were peritonitis-associated strains isolated as skin colonizers, and no patients developed peritonitis due to organisms previously isolated as skin colonizers.

A collection of 308 clinical isolates of β-haemolytic Lancefield group C streptococci was assembled from laboratories in England. Nigeria and New Zealand. Of these, 276 isolates were Streptococcus equisimilis. 23 S. milleri and nine S. zooepidemicus. Isolates of S. equisimilis in the African collection, though few, gave higher rates of lactose and raffinose fermentation, aesculin hydrolysis and positive α-galactosidase reactions than those from elsewhere. Erythromycin resistance was found in 1·9% of the English isolates of S. equisimilis.Strains from superficial infections accounted for 88 % of the collection and were most commonly isolated from the upper respiratory tract, skin or wounds. Amongst the 36 patients yielding isolates from deep sites S. equisimilis was found in septicaemia, cellulitis, abscess, peritonitis, septic arthritis, pneumonia, mycotic aneurysm and acute epiglottitis. S. milleri was found in abdominal abscesses, peritonitis, pleural empyema and osteomyelitis and S. zooepidemicus was found in septicaemia, pneumonia, meningitis and septic arthritis. Within the collection an unselected general catchment of 214 isolates of group C streptococci from the laboratories in Yorkshire showed the following species: from 199 superficial infections 94% S. equisimilis. 5% S. milleri and 1% S. zooepidemicus and 15 patients withdeeper, more agressive infections 67, 27 and 6·7% of these species respectively.

Many infections, especially viral infections, show a certain periodicity which can be wholly or partly predictable. It is important to be able to recognize these patterns because anticipating changes in incidence should lead to better diagnosis, treatment and control of infection. In this review patterns of some viral and other infections in England and Wales which have been observed from laboratory reports over a period of 21 years, from 1967 to 1987, are described.

Legionella pneumophila serogroup 1 was isolated from post mortem specimens from 13 out of 58 patients with pneumonia diagnosed at autopsy. The results of a study undertaken in the hospital environment showed that the water plumbing system was colonized with L. pneumophila serogroup 1 which could also be isolated from respiratory devices filled with tap water. Control measures instituted are described.

The clinical application of the principles of epidemiological research has become fashionable. Three recent textbooks carry the words ‘Clinical Epidemiology’ in their titles (Feinstein, 1985; Sackett, Haynes & Tugwell, 1985; Weiss, 1986), and a venerable journal has recently changed its name to this effect (Feinstein & Spitzer, 1988). Deans of medical schools, Government Health Officials and editorialists pay tribute to the new science which is expected to steer the medical profession of the third millennium.

Clinical features, treatment and outcome were assessed retrospectively by means of a questionnaire in 174 patients in general practice whose vaginal swabs yielded bcta-haemolytic streptococci. These were compared with 96 patients whose swabs yielded no recognized microbial pathogens. Patients with group B streptococci did not differ in any of these parameters from the control group, but those with group A streptococci were more likely to have vaginal soreness, a purulent discharge. and to respond to anti-streptococcal antibiotics. Implications for laboratory reporting are discussed.

Following the occurrence of five cases of Legionnaires' disease among patients and therapists at a French hot spring spa, a series of cleansing procedures and an epidemiological study were undertaken. During a 3-month period, the spring water was repeatedly sampled. Serum samples were taken from 689 randomly selected patients, 230 therapists, 134 administrative staff and a control group of 904 blood donors.

Legionellaceae were present in the spring water at concentrations of 103–1055 colony forming units/1. Fifteen different species or serogroups were isolated with Legionella pneumophila serogroups 3 and 1 predominating. No clinical cases of Legionnaires disease were observed during the study. However, 11% of the therapists and 5% of the patients either had a high titre of antibody (≥256) to at least one species or serogroup or seroconverted during the study. Mean antibody titres in the three study groups were significantly higher than those in the blood donors against 11 of the 32 legionella antigens tested. Nine of these 11 antigens corresponded to species or serogroups isolated from the spring water. The highest mean antibody titres in all three study groups were against L. pneumophila serogroup 3, the most common legionella in the spring water.

These findings have important implications for the maintenance of adequate standards of hygiene, bacteriological sampling and clinical surveillance in this and similar establishments.

There is a significant role for the practice of epidemiology throughout the world if health professionals are to work effectively towards ‘Health for All’. The status quo leaves a great deal to be desired, as evidenced by recent signals from the premier international health agency, the World Health Organization (WHO). The forty-first World Health Assembly meeting in Geneva, Switzerland, in May 1988 approved a resolution stressing ‘the importance of epidemiology as a tool for the formulation of rational health policy’ (PAHO, 1988). In addition to its key role ‘in studying the causes and means of prevention of disease’, the Assembly noted epidemiology's valuable inputs in ‘health systems research, information support, technology assessment, and the management and evaluation of health service’.

It has been proposed that inhibitory substances produced by viridans streptococci colonizing the upper respiratory tract aid in cradication of established group A streptococcal colonization of that site. We studied the prevalence of inhibitory-substance producing strains of Streptococcus salivarius in throat cultures from three groups of children: 16 children with persistently positive throat cultures for group A streptococci despite receiving recommended therapeutic courses of antibiotics (group I). 26 children from whom group A streptococci were eradicated from the upper respirator tract by antibiotic therapy (group II). and 18 children who never harboured group A streptococci in their upper respiratory tract during the study period (group Ill). An vitro deferred antagonism method was employed to detect inhibitory substances: 5233 strains of S. salivarius were examined. Strains of S. salivarius producing inhibitory substances were isolated from 76−88% of the children in each group on at least one occasion.However, only a small percentage of subjects in each group harboured strains producing these substances in every throat culture. The mean total percentage of S. salivarius strains producing inhibitory substances was 21·8% in children in group 1·22.4 % in children in group II. and 16.4% in children in group III: these percentages were not statistically different (P > 0·1). In this study, we could not confirm a significant role for inhibitory substances produced byS. salivarius in the eradication of group A streptococci from the upper respiratory tract of colonized individuals.

Genetic variation in isolates of Escherichia coli obtained mostly from urinary tract infections in humans and domesticated animals (dogs and cats) was assessed for 16 enzymes using multilocus enzyme electrophoresis to characterize chromosomal genotypes. A total of 148 isolates comprised 63 distinct electrophoretic types (ETs) and about half of the isolates belonged to one of 9 common ETs. A bootstrap analysis of genetic distance between ETs revealed three significant groups of strains. Variation in allele frequencies among groups accounted for 40% of the total genetic diversity. The majority of the common ETs fell into a major cluster of closely related strains. The recovery of multiple isolates of the same electrophoretic types and serotypes from unassociated hosts suggests that these bacteria represent uropathogenic clones that are widely disseminated in humans and animals

A group of 150 Staphylococcus saprophyticus strains isolated from urinary tract infections in women were included in this study. Antimicrobial susceptibility tests showed that these isolates were sensitive to most antimicrobial agents. All strains were sensitive to penicillin. cephalothin. gentamicin. kanamvcin. trimethoprim and nitrofurantoin. Resistance to tetracycline was present in 10·6% of the strains. to chioramphenicol in 4 % to erythromycin in 1·3% and to streptomvcin in 1·3% All strains were resistant to cadmium chloride as well as to novobioein and nalidixic acid. Plasmid analysis showed that 8·2 % of the strains harboured plasmids, some of them with complex plasmid profiles.

To investigate cross-colonization with and persistence of Pseudomonas aeruginosa in cystic fibrosis (CF). 181 isolates from 76 CF patients were typed using a P. aeruginosa -specific DNA probe. Whereas sibling pairs predominantly harboured genotypically identical P. aeruginosa strains, all of the other patients harboured different strains. Seventy-nine per cent (22/31) of the infected CF patients harboured the same strains at the beginning and the end of a summer camp. A change of strains was seen in 10% (3/31) of the patients at the end of the camp. Forty-six per cent (6/13) of the patients who were apparently initially uninfected, acquired P. aeruginosa by the end of the period. Genotyping proved that strain change or acquisition was due to cross-colonization in four of nine cases. Very little P. aeruginosa was isolated from the inanimate environment. Persistence of P. aeruginosa after a temporary loss due to antibiotic therapy was seen in 12/16 paired patient strains before and after antibiotic therapy. Thus, suppression followed a flare-up seemed to occur in these patients rather than eradication and a new infection. When 35 patients were followed over a period of 6 months, 7 (20%) changed the strain in their sputum. Only one of 43 patients harboured two different P. aeruginosa strains simultaneously over a long period.

The presence of different Campylobacter jejuni serotypes in Swedish patients with diarrhoea and in Mexican patients with or without diarrhoea was investigated with special reference to repeated isolations during the course of infection and to symptomatic and asymptomatic episodes. The study included 136 C. jejuni isolates from 62 Mexican children and 173 isolates from 68 Swedish patients. The bacteria were serotyped for heat-stable (HS) and heat-labile (HL) antigen.

One hundred and twenty-five Shigella flexneri strains, isolated during January-December 1984, at the Dhaka treatment centre of the International Centre for Diarrhoeal Disease Research, Bangladesh, were serotyped using absorbed rabbit antisera specific for all type-and group-factor antigens, as well as a group of ten mouse and rat monoclonal antibodies. Electropherotypes of the plasmid deoxyribonucleic acid (DNA) were also determined. S. flexneri 2a was the predominant serotype followed by 3b, 1a, and 2b.The recently described E1037 antigen was also found in three strains of S. flexneri serotype 6. Electropherotyping of the plasmid DNA showed that three plasmids of approximately 140. 2·7. and 2 megadalton (MDa) were present, respectively, in 97, 97 and 94% of the 125 strains. Additional plasmids of various other sizes were also present in different serotypes except in serotype 2a. The additional plasmids again appeared to be specific for that particular serotype. For example, all 12 strains of S. flexneri 2b harboured an additional plasmid of approximately 1 MDa. Thus, electropherotyping of plasmid DNA of different serotypes of S. flexneri might be useful to differentiate S. flexneri from other species of Shigella and in identifying different serotypes of S. flexneri. Therefore, the common plasmids, plus the additional plasmids. could be used to identify epidemic, as well as sporadic, subclones of S. flexneri strains.

Campylobacter jejuni/coli strains from 164 chickens were serotyped by the methods previously described by Penner et al. and Lior et al. The chickens were sampled during breeding from hatching to the age of 42 weeks. The birds were housed, in two separate groups, under different environmental conditions, (for comparison of the effect of hygienic precautions on the transmission of the bacteria during breeding). In the group where the hygienic conditions could be controlled to a greater extent, the chickens became colonized later in the breeding chain and with only one single campylobacter strains.