G.M. Scott

Prophylaxis with a nevirapine-containing triple regimen after exposure to HIV-1

Evidence suggests that nevirapine, a non-nucleoside reverse-transcriptase inhibitor, might be very effective in the prevention of HIV-1 integration and the reduction of risk of HIV-1 acquisition after exposure. We used a triple combination regimen, including nevirapine, for prophylaxis after occupational or sexual exposure to HIV-1 infection. Of 57 individuals who started therapy, only 41 returned for follow-up. Five had a grade three or four drug-induced hepatitis, two of whom also had a rash. This high rate of major adverse events raises concerns over the safety of such a regimen for its use in this population.

An Augmented Data Method for the Analysis of Nosocomial Infection Data

The analysis of nosocomial infection data for communicable pathogens is complicated by two facts. First, typical pathogens more commonly cause asymptomatic colonization than overt disease, so transmission can be only imperfectly observed through a sequence of surveillance swabs, which themselves have imperfect sensitivity. Any given set of swab results can therefore be consistent with many different patterns of transmission. Second, data are often highly dependent: the colonization status of one patient affects the risk for others, and, in some wards, repeated admissions are common. Here, the authors present a method for analyzing typical nosocomial infection data consisting of results from arbitrarily timed screening swabs that overcomes these problems and enables simultaneous estimation of transmission and importation parameters, duration of colonization, swab sensitivity, and ward- and patient-level covariates. The method accounts for dependencies by using a mechanistic stochastic transmission model, and it allows for uncertainty in the data by imputing the imperfectly observed colonization status of patients over repeated admissions. The approach uses a Markov chain Monte Carlo algorithm, allowing inference within a Bayesian framework. The method is applied to illustrative data from an interrupted time-series study of vancomycin-resistant enterococci transmission in a hematology ward.

Comparison of wound scoring methods for use in audit.

Accurate information on the prevalence of surgical wound infection is difficult to obtain; outpatient follow-up is often inadequate. For two months in 1993 and again in 1995, surgical wounds throughout one hospital were examined by the same observer with the intention of comparing different methods for assessing wound infection. Two standard definitions [Centers for Disease Control (CDC), USA and National Prevalence Survey (NPS), UK] were compared with ASEPSIS and the Southampton method. In 1993, 325 wounds in 230 patients were examined with follow-up of 203 (88%) patients. In 1995, 559 wounds were surveyed in 375 patients with follow-up in 364 (97%). Patient groups in the two years were similar. ASEPSIS identified 92 (13%) wounds as having scored over 20 points indicating infection, and another 16.5% having disturbance of healing. There was no significant difference between the two surveys. The two scoring methods were more sensitive than the standard definitions but CDC and NPS did not differ significantly from each other. Between 44 and 47% of clean wounds identified as infected by standard definitions were classed as disturbance of healing by ASEPSIS. All methods were labour-intensive and to implement any one of them on a regular basis would require a full-time investigator. The first surveillance program with feedback of results to the surgeons did not significantly affect the rates two years later.

Bacterial contamination of autologous bone marrow during processing

As part of an audit of the processing of autologous bone marrow, we found that marrow was often contaminated with organisms potentially pathogenic to neutropenic recipients. One of 14 marrows studied was found to be contaminated before the processing stage and five others became contaminated during processing. The organisms isolated at these stages were Propionibacterium sp., coagulase-negative staphylococci, Staphylococcus aureus and coryneforms, suggesting that the skin was the likely source of contamination. Five out of the 11 marrows returned to patients were found to be contaminated after thawing. Two of these were marrows previously shown to be contaminated with coagulase-negative staphylococci before freezing, and from these coagulase-negative staphylococci were isolated again, in one case the strains were indistinguishable. New organisms isolated after thawing included Bacillus sp. and Corynebacterium sporogenes suggesting contamination from the environment. No infections attributable to these organisms were demonstrated in any of the patients studied.

Sharps injury! A review of controversial areas in the management of sharps accidents

* I6a Rochester Square, London, NW/ 9SA, -fSenior Medical O@cer; Department of Health, Room 724, Wellington House, I33-I55 Waterloo Road, London SE I 8UG, fDeputy Director for Clinical Care, Warren G Magnusson Clinical Center, National Institutes of Health, Bethesda Md, §Science Dept., British Medical Association, BMA House, London, WC I H 9je jj8 Burlington Road, Bristol, BS6 6TL, j[Clinical Microbiology, University College London Hospitals,London, WC I E 6DB

A nosocomial outbreak due to non-encapsulated Haemophilus influenzae: analysis of plasmids coding for antibiotic resistance

An outbreak of infections with non-encapsulated Haemophilus influenzae, resistant to ampicillin, chloramphenicol, sulphonamide and tetracycline involved 13 elderly patients and three nurses on acute admission and care of the elderly wards. Thirty-two isolates were found to be indistinguishable on analysis of biotype, antibiogram, serotype and major outer membrane proteins (MOMP). Plasmids could not be identified in the original isolates but after mating with a Rec A H. influenzae recipient, the resultant transconjugates were found to harbour either a 72 kilobase pair (kB) plasmid coding for resistance to chloramphenicol, ampicillin, sulphonamide and tetracycline or a 65 kB plasmid coding for resistance to chloramphenicol, ampicillin and sulphonamide. Both plasmids yielded virtually indistinguishable restriction digest patterns. This suggests that the tetracycline resistance gene (Tc gene) is a non-essential component of one basic plasmid responsible for the multiple antibiotic resistances seen in the strains recovered during the outbreak. This illustrates the value of plasmid profiles to compare strains of non-encapsulated H. influenzae, and suggests that plasmid restriction enzyme analysis is critical.

An audit of first generation cephalosporin usage.

Cefadroxil is a semi-synthetic first generation oral cephalosporin with advantages of almost 100% excretion in the urine within six hours and low cost. It was freely available in the formulary and we undertook an audit of its usage, the indications cited, underlying clinical conditions and relevant microbiology in 106 cases. Following the audit, cefadroxil was restricted, available only on the advice of a microbiologist. Subsequently, another survey was carried out to document the reasons for requesting cefadroxil by clinical staff and the alternatives suggested in each case. The first survey revealed that in 91% cases, cefadroxil had been used inappropriately. The second suggested that the reasons for requesting it were based upon misunderstanding by clinicians as to its value. The only useful indication identified was the treatment of susceptible bacteruria in pregnancy. A suitable oral alternative could be identified for all other cases where an antibiotic was indicated. We believe that first generation cephalosporins such as cefadroxil have little role in hospital practice and should therefore be restricted.

Is the detection of Mycobacterium tuberculosis DNA by ligase chain reaction worth the cost: experiences from an inner London teaching hospital.

Aims—To evaluate the clinical usefulness and the costs of using a rapid, commercial ligase chain reaction test (LCx) to detect Mycobacterium tuberculosis directly from clinical samples. Methods—A prospective study of 2120 routine clinical specimens from 1161 patients over a 13 month period. Investigations for mycobacterial disease by microscopy, culture, and the Abbott LCx assay were performed. Sequential LCx assays were monitored in a cohort of patients undergoing treatment. The costs of the assay were calculated using the WELCAN system. Sensitivity, specificity, and positive and negative predictive values of the LCx assay were compared with conventional tests. The performance of the assay in patients undergoing treatment and cost in terms of WELCAN units converted to pounds/annum was studied. Results—The assay was 85%/88% sensitive and 98%/100% specific in culture confirmed/clinically confirmed cases of tuberculosis, respectively. The assay was not useful for the measurement of treatment outcomes. The test cost approximately £42 500/annum. Conclusions—The assay is a rapid, sensitive, and specific adjunct to clinical diagnosis, especially in differentiating non-tuberculous mycobacteria. However, it does not differentiate old and treated tuberculosis from reactivated disease, it is not useful to monitor adherence to treatment, and it is expensive.

Use of corticosteroids to suppress drug toxicity in complicated tuberculosis.

Four cases of tuberculosis complicated by allergic or toxic reactions to antibiotic treatment are presented. In each, it was considered essential to suppress the reactions in order to give effective chemotherapy. This was achieved by using prednisolone generally in a dose of 40 mg/day or less during the continuation phase of therapy. Reactions to essential treatment are an important indication for corticosteroid treatment in tuberculosis.