In-vitro and in-vivo characterisation of resistance to colonisation with Clostridium difficile.

In hamsters, resistance to colonisation by Clostridium difficile appears to be mediated by micro-organisms that are present in the gut in relatively low concentrations. Small amounts of normal caecal contents inhibited the growth of C. difficile when added to cultures in vitro or given to animals which had been treated with clindamycin. Filtrates of caecal contents, frozen and thawed contents and contents diluted to 0.1% wet weight lost their inhibitory properties. However, caecal contents retained their protective capacity after culture for 7 days in vitro. Antibiotic treatment altered resistance to colonisation by only a few species of clostridia. Faeces of animals treated with ampicillin but not clindamycin recovered colonisation resistance after incubation at 37 degrees C in vitro. Since human faeces could also restore colonisation resistance to hamsters, the hamster model may be useful for the study of resistance to colonisation by C. difficile in man.

Multiple episodes of bacterial endocarditis occurring over 9 years.

We present a patient who was treated for bacterial endocarditis on 10 occasions in 9 years. In all but one of these episodes blood cultures were positive and the last two recurrences occurred on an aortic valve homograft. The pathogenesis of recurrent infective endocarditis in non-intravenous drug abusers is unclear and prevention of recurrences poses a difficult problem.

Quantitative study of antibiotic-induced susceptibility to Clostridium difficile enterocecitis in hamsters.

Commonly used antibiotics were compared for their ability to induce Clostridium difficile enterocecitis and death in hamsters. Susceptibility to infection with C. difficile was measured by calculating 50% lethal doses (in CFU) for hamsters for various intervals after antibiotic treatment. Infection occurred after very small doses of C. difficile were given to hamsters treated with clindamycin, ampicillin, flucloxacillin, and cefuroxime; there was little difference between the antibiotics in the degree of susceptibility that they induced. A large difference in the duration of susceptibility was observed, however, with susceptibility being temporary following ampicillin, flucloxacillin, and cefuroxime administration but long-lived following clindamycin administration. A larger dose of ampicillin, multiple doses of ampicillin, and a combination of antibiotics had comparatively small effects on the duration of susceptibility. C. difficile growth and toxin production in in vitro suspensions of cecal contents were found to correlate closely with in vivo hamster infectivity. A persisting loss of colonization resistance following antibiotic treatment may be a type of postantibiotic effect. Although these results cannot be applied directly to humans, they suggest lines of further investigation into how antibiotics may differ in producing risks of C. difficile infection and pseudomembranous colitis in patients.

Compliance with anti-tuberculous therapy: a field trial of a pill-box with a concealed electronic recording device.

We have conducted a field trial of a pill-box containing a concealed electronic device for monitoring compliance in 23 consecutive adult out patients taking a rifampicin/isoniazid combination once daily. In 22 cases, the times when the box was opened were successfully recorded for the entire period (mean (SD) 26 (5) days) between successive clinic visits. In the other patient the record terminated after one week, a broken box being returned. Both totality of compliance (as assessed by box openings) and consistency of compliance (the proportion of the total number of intervals between openings which were of 22 to 26 h in length) were significantly greater in those studied in the intensive than in the maintenance phase of therapy. Patients may have taken the reduction in medication at the end of the intensive phase as signalling cure. A computer program has been developed to display the recorded data. This allowed the physician responsible to assimilate at a glance the patient's tablet-taking habits. In routine practice knowledge of the presence of the device may improve compliance and a discussion of the graphical display may prove of value in counselling.

Antitoxin activity of human polymorphonuclear leucocytes.

Human polymorphonuclear leucocytes (PMNL) inactivate Clostridium difficile cytotoxin and C. perfringens phospholipase C, but not C. perfringens enterotoxin. Both whole cells and sonicated suspensions possess activity, but mononuclear cell fractions of peripheral blood do not. Antitoxin activity closely correlates with cell concentration. The highest cell concentrations tested completely inactivated C. difficile cytotoxin by 2 min. Sucrose density gradient fractionation of PMNL showed antitoxin activity to be associated with myeloperoxidase, locating it in the primary or azurophil granules. Toxin inactivation was prevented by protease inhibitors suggesting that it is due to one of the neutral proteases present in these granules. PMNL are more active against C. difficile cytotoxin than purified chymotrypsin. PMNL may be a primary defence against certain bacterial exotoxins.

Enterotoxigenic Clostridium perfringens: a possible cause of antibiotic-associated diarrhoea.

Free Clostridium perfringens enterotoxin was detected in the stools of 11 patients with diarrhoea. All had high faecal counts of enterotoxigenic strains of C perfringens, mostly of serotypes not commonly associated with food poisoning. 10 of these 11 patients had severe or prolonged diarrhoea which had developed after antibiotic treatment. Enterotoxigenic C perfringens appears to be one of the causes of antibiotic-associated diarrhoea.

Epidemiology of Clostridium difficile in infants.

The epidemiology of Clostridium difficile was studied prospectively in 451 newborn infants by daily screening of fecal samples. Colonization rates in three postnatal wards ranged from 2% to 52%. Many colonizations were sporadic, but on two wards there was evidence of clustering. On one of these occasions prospective environmental sampling yielded C. difficile organisms from a potential common source. Mothers were shown not to be the sources of their infants' organisms. Both toxin-producing and non-toxigenic strains were common; differentiation according to toxin type was epidemiologically useful. Cross contamination is the most likely explanation of the spread of C. difficile among hospitalized infants; the organism could spread among adults who are at risk of developing antibiotic-associated colitis in a similar manner.

Aetiology of acute diarrhoea in adults.

We have studied 73 adults with acute diarrhoea and identified a micro-organism or toxin likely to be the cause in 58%. In addition to routinely cultured bacteria, Campylobacter coli/jejuni and Clostridium difficile were important pathogens in the community. Patients who developed diarrhoea after antibiotic use had a distinctive clinical syndrome and comprised the third largest group of cases. Clinical, epidemiological, and histological features in an additional group with negative cultures and no antibiotic history suggest that an additional bacterial pathogen remains to be identified as a cause of acute diarrhoea in adults.

Epidemiology of experimental enterocecitis due to Clostridium difficile.

Hamsters can survive a course of clindamycin if they are held in a protected environment. Inoculation of Clostridium difficile regularly results in fatal enterocecitis in such animals but is without effect in untreated animals. These findings suggest that in the development of enterocecitis, clindamycin treatment and infection with C. difficile are separate events, and they imply that hamsters usually acquire C. difficile from environmental sources. Environments appear to differ in the risk of exposure to C. difficile, high-, medium-, and low-risk areas being recognizable. Once introduced, C. difficile may spread from animal to animal. Parallel with the incidence and epidemiology of human antibiotic-associated pseudomembranous colitis are discussed.

Isolation of rhinoviruses and coronaviruses from 38 colds in adults.

Nasal washings were collected from 27 normal adults during 38 naturally acquired colds. The washings were exhaustively tested using tissue cultures, organ cultures and electron microscopy. Washings yielding no identifiable agent were inoculated into human volunteers, and further specimens obtained from the latter were examined by the same techniques in vitro. Viruses were identified in association with 25 of the original 38 colds (65.7%). Fifteen were rhinoviruses (39.5%), seven coronaviruses (18.4%), two were para-influenza viruses, and one was influenza virus. Use of organ cultures and of volunteers significantly increased the isolation rate. No agent was cultivated from the remaining 13 specimens, although tests in volunteers showed that cold-producing agents were present in five of them (13%). Three specimens gave doubtful results in volunteers, and five others, all collected within a period of six weeks in December and January, apparently contained no infectious agent.