Sixteen cases of verotoxin producing Escherichia coli (VTEC) O 157:H7 Phage Type 49 infection were identified in the North West of England from 1 September to 1 November 1991, eight of whom lived in or around the same large town. Eleven of the cases were aged 10 years or less, and five of the affected children developed haemolytic uraemic syndrome. A case control study demonstrated a strong association between VTEC O 157: H7 PT 49 infection and the consumption of a locally produced live yoghurt. This is the first time that an outbreak of VTEC O 157 infection has been linked to the consumption of yoghurt and this vehicle of infection should be considered when investigating such outbreaks in future.

For Salmonella typhimurium from humans in England and Wales, the incidence of multiple resistance more than doubled over the 8-year period 1981–8 and, over the next 2 years, increased by a further 7%. From 1981 to 1988 both resistance and multiple resistance also increased significantly in S. virchow and although multiple resistance did not increase over the next 2 years, the overall incidence of resistance has continued to rise. In 1990 the majority of S. typhimurium from cattle were multiply-resistant and the occurrence of such resistance has quadrupled since 1981. Multiple resistance has also increased in S. typhimurium from pigs and, to a lesser extent, from poultry. In contrast, multiple resistance has remained uncommon in the poultry-associated serotype S. enteritidis. For S. virchow, multiple resistance was common in a phage type frequently associated with poultry meat imported from France.

The continuing use of a range of different antimicrobials in calf husbandry has been an important factor in promoting the emergence of multiply-resistant strains of S. typhimurium in cattle. In contrast, multiple resistance has remained rare in those serotypes associated with poultry, where the use of such antimicrobials has been less intensive.

It is hoped that recent recommendations discouraging, in veterinary medicine, the prophylactic use of antibiotics with cross resistances to those used in human medicine will result in a reduction in the occurrence of multiresistant strains in food animals and subsequently in humans.

The Phene Plate system for typing Salmonella serotypes (PhP-S) is a simple automated typing method based on biochemical fingerprinting. It gives a quantitative value of the metabolism of various substrates by measuring the speed and intensity of each reaction. The ‘biochemical fingerprint’ of each isolate is used to calculate similarities among the tested strains with a personal computer program. We used this system to examine a collection of 86 strains of Salmonella enteritidis isolated from human sporadic cases in Germany between 1980 and 1992. Twenty-three biochemical phenotypes (BPTs) consisting of 9 common (C) and 14 single (S) BPTs were identified. BPTs C2 and C4 containing 20 and 36 strains respectively accounted for 65% of the isolates. Strains of BPT C2 were found over a wide period of time whereas strains of BPT C4 were isolated during the period between 1988 and 1992. With phage typing, 11 discrete phage types (PTs) and 18 strains designated as non-specific type (NST) were identified. PTs 4 and 8 with 39 and 17 strains respectively were the dominant PTs. Strains of PT 8 were isolated over a wide period of time whereas all (except one) strains of PT 4 were isolated between 1988 and 1992. Combination of biochemical fingerprinting and phage typing divided the strains into 25 phenotypes (BPT:PTs). Whilst phenotype C2:8 was found over a number of different years, phenotype C4:4 was isolated only between 1988 and 1992. These findings indicate the presence of one persistent and one recently emerged phenotype among S. enteritidis strains in Germany. Although both methods identified the presence of both major and less common types, biochemical fingerprinting with the PhP-S system also provided information about relationships between the strains.

The growth of Salmonella enteritidis PT4 in albumen around an intact yolk was governed by the age of the egg on inoculation. In the majority of eggs, held at 20° C, the bacterium was unable to grow rapidly until eggs had been stored for approximately 3 weeks. The multiplication of S. enteritidis in stored eggs appeared to be associated with alterations to the yolk membrane which allowed the bacterium to either invade the yolk or obtain nutrients from it. The rate at which egg contents change to permit the growth of S. enteritidis would appear to be temperature related and took place more rapidly when eggs were stored under conditions where temperatures fluctuated and, on occasions, reached 30° C.

Between January and March 1992, 361 faecal specimens were collected from the healthy black population in the Transvaal Province of South Africa. Each specimen was examined for the prevalence of antimicrobial resistance in commensal bacteria. Volunteers, from both rural and urban dwellings, were divided into four age groups. The overall carriage rate of resistance varied from 88.6% for ampicillin, 74.2% for trimethoprim, 52.6% for chloramphenicol, 10.2% for nalidixic acid to 7.5% for gentamicin. The carriage of resistance found to each individual antimicrobial agent was slightly higher in the rural population rather than the urban population but there was no correlation between the prevalence of antimicrobial resistance and the age group.

Escherichia coli and salmonella strains with plasmids conferring resistance to gentamicin and apramycin have been isolated with increasing frequency both from cattle and hospital patients in Belgium. The apramycin-gentamicin resistance plasmids were characterized in recipient strains by their profiles and molecular weights using agarose gel electrophoresis, by their antimicrobial resistance patterns and by replicon typing using a series of DNA probes specific for the genes controlling their systems of replication. Overall, most of the plasmids differed in their DNA electrophoretic patterns. Seventeen different antimicrobial resistance profiles were observed, and there were six different types of replicons. However, two replication genes predominated and had a preferential distribution in different bacterial species. The rep FIC.a plus rep Q multireplicon was found mainly in plasmids recovered from gentamicin- and apramycin-resistant E. coli while replicon of the type rep FIC.b largely prevailed in S. typhimurium. Identical replication genes were found in most animal and human strains, hence suggesting a high homology between apramycin- gentamicin plasmids in these communities. Finally, our results indicate that the rapid spread of apramycin-gentamicin-resistance in several species of Enterobacteriaceae isolated from animals and from humans in Belgium is not due to a single plasmid, but rather that the gene encoding AAC(3)-IV is carried by various replicons.

Plasmid analysis of Salmonella enteritidis isolates from human gastroenteritis cases and from two commercial egg-producing poultry flocks was performed to determine if the poultry flocks were the source of the human infections. The plasmid profile and restriction fragment pattern (fingerprint) of five S. enteritidis isolates from human cases matched those of nine isolates from internal organs of egg-laying hens in one flock which was the source of eggs consumed by the cases. Another commercial flock was epidemiologically associated as the source of eggs consumed by affected persons in four separate gastroenteritis outbreaks from which S. enteritidis isolates were available. Five S. enteritidis isolates from human cases in these four outbreaks had the same profile and fingerprint, and they all matched those of the 24 isolates from hens in this flock. These results provide further documentation of egg-borne transmission of S. enteritidis to humans.

An epidemiological investigation was conducted to identify risk factors related to hygiene and husbandry practices which determine the introduction of Campylobacter spp. into broiler chicken flocks. All 176 broiler farms in an area in southeastern Norway participated in the study. Each farm was represented by one flock selected at random during a one-year period. The flocks were examined for Campylobacter colonization at slaughter, and the flock managers were sub-sequently interviewed about hygiene and husbandry practices. Campylobacter spp. were recovered from 32 (18%) of the flocks. The proportion of colonized flocks varied geographically and seasonally with a peak in the autumn. The following variables were found to be independently associated with an increased risk of Campylobacter colonization using logistic regression analysis: (i) feeding the broilers undisinfected water (odds ratio (OR) = 3·42, P = 0·045), (ii) tending other poultry prior to entering the broiler house (OR = 6·43, P = 0·007), (iii) tending pigs before entering the house (OR = 4·86, P = 0·037), (iv) geographic region (Hedmark versus Østfold county) (OR = 2·91), P = 0·023, (v) season (autumn versus other seasons) (OR = 3·43, P = 0·008). Presence of rats on the farm was associated with an increased risk, but this factor did not reach statistical significance (OR = 3·96, P = 0·083). Preventive measures should include dis-infection of drinking water and strict hygienic routines when the farm workers enter the rearing room. The results indicated that disinfection of drinking water is the preventive measure most likely to have the greatest impact on the prevalence of Campylobacter among broiler chicken flocks in the study area (population attributable fraction = 0·53).

It is generally accepted that most patients with Clostridium difficile-associated diarrhoea acquire the organism from the environment. Recently we demonstrated that household pets may constitute a significant reservoir of C. difficile through gastrointestinal carriage in up to 39% of cats and dogs. These findings suggested that direct transmission from household pets, or contamination of the environment by them, may be a factor in the pathogenesis of C. difficile-associated diarrhoea. To investigate this possibility, we examined isolates of C. difficile from humans, pets and the environment by restriction enzyme analysis (REA) and restriction fragment length polymorphism (RFLP) typing using enhanced chemiluminescence. Both REA and RFLP typing methods used Hind III digests of chromosomal DNA. A total of 116 isolates of C. difficile from pets (26), veterinary clinic environmental sites (33), humans (37) and hospital environmental sites (20) was examined. REA was far more discriminatory than RFLP typing and for all isolates there were 34 REA types versus 6 RFLP types. There was good correlation between the REA types found in isolates from pets and from the veterinary clinic environment, and between isolates from humans and from those found in the hospital environment. There was, however, no correlation between REA type of C. difficile found in pets and isolates of human origin. We conclude that there may still be a risk of humans acquiring C. difficile from domestic pets as these findings may be the result of geographical variation.

The use of polyclonal antibodies in differentiating between samples of faecal microflora derived from ten healthy volunteers was assessed. The distribution of FITC-labelled antibodies (of the IgA, IgG and IgM isotype) over 144 morphologically distinct subsets of faecal bacteria (‘morphotypes’) was quantified by means of digital morphometry and quantitative immunofluorescence. Furthermore, a new dataprocessing algorithm was developed which makes objective quantitation of the antibody distributions over the faecal morphotypes possible. The results of this study imply that the antibody binding capacity of faecal morphotypes is a unique characteristic of faecal microflora.

Healthy persons were shown to possess circulating antibodies of both IgA, IgG and IgM isotype directed against the bacteria of their faecal microflora, assessed by immunomorphometry. After removal, by absorption, of the fraction of antibodies directed against the autochthonous faecal bacteria or cross-reacting with allogenous faecal bacteria, there were still antibodies left directed against allogenous faecal bacteria of both the IgA, IgG and IgM isotype. However, relatively more antibodies of the IgA isotype appeared to be directed against allogenous bacteria than against indigenous faecal bacteria. Persons who reacted with specific antibodies to many bacteria of their own flora also tended to react specifically to bacteria in the allogenous microflora of the other volunteers. The patterns of antibodies directed to faecal bacteria of different morphologies (morphotypes) were unique for each individual.

Cooling towers have been demonstrated to be amplifiers and disseminators of legionella, the causative organism of Legionnaires' disease. Community outbreaks associated with cooling towers have been reported with several common factors. Small towers (< 300 kW) have predominantly been implicated in outbreaks. Cooling tower-associated outbreaks are most frequent in autumn, and frequently implicated systems have been operated after a period of shutdown.

This paper reports field study data relating system operation to legionella colonization of systems. Operating systems have been shown to be more frequently colonized by legionella than shutdown systems. In some cases operation of systems after periods of shutdown raised legionella concentrations from below detection limits to between 50 and 950 c.f.u./ml within 10 min.

These data and previously reported data relating to biofilm and sediment colonization of the systems, and community outbreaks of Legionnaires' disease, have been used to develop a model explaining the seasonal nature of outbreaks associated with irregularly operated, small cooling tower systems.

Although human visceral leishmaniasis (VL) is a notifiable disease in Italy, there is evidence that the actual number of cases is far higher than that notified. A programme for active surveillance of VL in the 14 Italian endemic regions was launched by the Istituto Superiore di Sanità. We report data collected during a 3-year period of active surveillance in Campania, a south Tyrrhenian region covering 4·5% of the Italian territory. Out of 120 clinically suspected cases referred to medical and diagnostic references centres, there were 52 confirmed VL cases (17·3/year), i.e. 10-fold more than previously notified. Most of the infection sites were in rural areas or peripheral districts of towns in hilly parts of Naples province. An epidemic cluster of 10 cases was identified in a microfocus of Caserta province. The biochemical analysis of 23 Leishmania stocks showed a zymodeme composition indicating Campania as an old and well-established focus of VL. The data obtained emphasize that the present notification system for VL in Italy is inadequate.

Intranasal inoculation of 12 young adult mice (strain TO) with Mycoplasma pulmonis protected all of them against vaginal colonization when they were challenged intravaginally 60 days later with the same mycoplasmal strain. In contrast, all 15 mice without a respiratory infection became colonized vaginally (geometric mean titre [GMT] 4·6 × 106 colour-changing units [c.c.u.]) when challenged in the same way. The GMT of serum antibody, measured by a micro-immunofluorescence technique, prior to challenge was 200 and 8 for the oropharyngeally infected and unexposed mice, respectively. The GMT of antibody in vaginal washings from the two groups was 6 and 3, respectively. All four nude BALB/c mice were susceptible to vaginal colonization (GMT 5·6 × 106 c.c.u.) after oropharyngeal infection (GMT 5·1 × 104 c.c.u.) resulting from intranasal inoculation, as were all six nude mice (vaginal GMT 1·4 × 107 c.c.u.) that had not been inoculated intranasally. In contrast, all ten of their immunocompetent counterparts were resistant to vaginal colonization after oropharyngeal infection (GMT 1·3 × 103 c.c.u.), whereas all nine such mice that had not been infected oropharyngeally were susceptible to vaginal colonization (GMT 7·6 × 106 c.c.u.). These results show the important role that a respiratory infection has in protecting the vagina against colonization and that protection is dependent on a functioning T-lymphocyte system.

In order to study the effect of antichlamydial antibodies in ocular secretions on resistance to ocular chlamydial infection and clearance of this infection, we have performed linked longitudinal studies in a Gambian village in which trachoma is endemic. We have measured IgG and IgA antibody levels to a local serotype B isolate of Chlamydia trachomatis by amplified enzyme immunoassay, and chlamydial antigen levels in conjunctival swabs using a commercially available immunoassay which detects chlamydial glycolipid. Having previously demonstrated that sharing a bedroom with a case of active trachoma is a risk factor for acquisition of the disease, we have analysed the effect of IgG and IgA antibody on the acquisition and persistance of clinical trachoma after controlling for age, sex, exposure to infection and for the presence of chlamydial antigen using a Poisson regression model. We have found that the presence of antichlamydial IgG in ocular secretions of disease-free subjects is associated with an increased incidence of trachoma. IgA antibody shows an opposite trend, but this is not statistically significant. One possible explanation of these findings is that antichlamydial IgG antibodies enhance the infectivity of C. trachomatis for the human eye; this could have major implications for the development of a chlamydial vaccine.

A study was undertaken to examine the feasibility of using naturally-occurring bacteriophages to assess the impact of re-laying on levels of viral contamination in Crassostrea gigas, the Pacific oyster. Two phages were chosen. One, male-specific (F+), was enumerated using Salmonella typhimurium. The other, a somatic phage, was detected using an, as yet, uncharacterized Escherichia coli. Investigations, using a variety of re-laying sites, demonstrated that numbers of F+ phage in oyster tissue declined more rapidly than those of somatic phage. For example, in oysters placed in commercially-used sea water ponds, F+ phage reached undetectable levels within 2–3 weeks, whereas somatic phage could still be detected 5 weeks after re-laying. The studies suggest that F+ phage may not be a suitable indicator for virus removal and that somatic phage may be better suited to this role.

This study investigated the morbidity associated with respiratory virus infections in patients with well-documented chest disease, and the risk of transmission between close contacts. Patients informed the study team if they were exposed to a family member or colleague with a cold. Patients and symptomatic index cases recorded respiratory symptoms during the study period. Acute nasopharyngeal swabs and paired sera were obtained for viral diagnosis.

Twenty-five (43%) of 58 recorded exposures resulted in a symptomatic illness and 16 (28%) patients developed lower respiratory tract symptoms. Sixteen (64%) of the 25 symptomatic patients contacted their general practitioner, 14 (56%) received antibiotics and 4 (16%) were hospitalized. Mean duration of illness was 10·6 days in symptomatic patients and 5·7 days in their corresponding index cases (P < 0·005). Mean symptom scores were 100·6 in symptomatic patients and 62.2 in index cases (P < 0·01). Respiratory viruses were identified in 19 (33%) episodes. Rhinovirus, coronavirus and respiratory syncytial virus infections were all associated with lower respiratory tract exacerbations.

Respiratory tract symptoms following exposure to a cold were comparatively severe in these patients with chronic chest disease. This group of patients might gain particular benefit from the introduction of effective vaccines or antiviral therapy.

Current levels of influenza vaccine uptake in patients considered to be at high risk have been determined by means of a questionnaire survey. During March–April 1992, information was sought from 624 patients in Leicestershire, UK with either chronic cardiovascular or respiratory disease, or diabetes; questions related to current health status and the request, offer and receipt of influenza vaccine in the current and three previous seasons. Ninety-eight percent of all offers of immunization were made in the primary care setting, and vaccine was well tolerated as judged by the fact that 86% of vaccinees between 1988/9–1990/1 returned for immunization in the following year. However in the 1991/2 season the overall level of vaccine uptake was only about 41% which is at variance with the stated policies and practices of general practitioners. Opportunities were missed, in both hospitals and general practices, to publicise and offer immunization to individuals with vaccine indications. Future attempts to improve vaccine uptake should focus on increasing the role of hospital staff in influenza prevention, in addition to promoting better vaccine delivery through primary care.

Nine years accumulated laboratory data derived from the culture of the cerebrospinal fluid of 11 360 aseptic meningitis cases were retrospectively reviewed to establish the epidemiology of viral meningitis in Cape Town. Virus was isolated from 3406 of the cases (91% enteroviruses and 9% mumps).

Five major summer viral meningitis episodes were documented: two of echovirus 4 (706 and 445 cases), echovirus 9 (223), coxsackie A9 (104) and one of unidentified enterovirus (324 cases – probably echo 9). Although coxsackie B was endemic, clusters of one or other type were dominant at any one time. Mumps was endemic. Sixty-two percent of all viral cases were <5 years old. The median ages of 4 and 5 years in echoviruses 9 and 4 (the epidemic strains) contrasted with that of 1 year in coxsackie B (with many cases <3 months old). Mumps peaked at 3–4 years of age. Males dominated overall, particularly in mumps.

Cases of western equine encephalitis in horses in 1987 in western USA and Manitoba, Canada were examined by backward trajectory analysis of winds. Culex tarsalis mosquitoes infected with western equine encephalitis virus could have been carried on southerly winds from Texas and Oklahoma to northern LTSA and from there to Manitoba. The presence of the Polar front over North Dakota and Minnesota at the end of July would have led to the landing of Cx. tarsalis in Montana and Wisconsin and prevented further carriage into Manitoba. Temperatures in southern Texas during the winter months (average daily maximum temperatures 19.7 °C and higher) would have permitted continuous transmission of western equine encephalitis virus by Cx. tarsalis in this area.

Weather factors involved in outbreaks from 1975–88 were analysed to see if epidemics in Manitoba (23 or more cases in horses) could be predicted. The conditions for epidemics could be defined as follows: (a) the number of cases in horses in LTSA was 98 or more, (b) winds were southerly with speeds 45 kmh-1 or higher, and (c) counts of Cx. tarsalis females/light trap per day were 3·2 or higher. There were 3 or fewer cases in Manitoba, when the number of cases in USA was 27 or less, even when Cx. tarsalis counts were higher than 3·2. With Cx. tarsalis counts below 3 and/or unsuitable winds, or the Polar front further south, the number of cases in Manitoba was between 0 and 17, even when the number of cases in USA was from 38–172. Without information on the extent of infection further south, the weather variables would probably be more useful in excluding the possibility of an epidemic in Manitoba than in predicting one.