IS6110-mediated deletions of wild-type chromosomes of Mycobacterium tuberculosis

The ipl locus is a site for the preferential insertion of IS6110 and has been identified as an insertion sequence, IS1547, in its own right. Various deletions around the ipl locus of clinical isolates of Mycobacterium tuberculosis were identified, and these deletions ranged in length from several hundred base pairs up to several kilobase pairs. The most obvious feature shared by these deletions was the presence of an IS6110 copy at the deletion sites, which suggested two possible mechanisms for their occurrence, IS6110 transposition and homologous recombination. To clarify the mechanism, an investigation was conducted; the results suggest that although deletion transpositionally mediated by IS6110 was a possibility, homologous recombination was a more likely one. The implications of such chromosomal rearrangements for the evolution of M. tuberculosis, for IS6110-mediated mutagenesis, and for the development of genetic tools are discussed. The deletion of genomic DNA in isolates of M. tuberculosis has previously been noted at only a few sites. This study examined the deletional loss of genetic material at a new site and suggests that such losses may occur elsewhere too and may be more prevalent than was previously thought. Distinct from the study of laboratory-induced mutations, the detailed analysis of clinical isolates, in combination with knowledge of their evolutionary relationships to each other, gives us the opportunity to study mutational diversity in isolates that have survived in the human host and therefore offers a different perspective on the importance of particular genetic markers in pathogenesis.

The management of pulmonary tuberculosis in adults notified in Scotland in 1993

The management of pulmonary tuberculosis (TB) in Scotland in 1993 was studied by asking the physicians responsible for all 321 adult cases of the disease notified that year to complete a standardized questionnaire relating to drug treatment and bacteriology. The response rate to the questionnaire was 100%. Isoniazid and rifampicin were used together in initial therapy in 98.4% of cases, while pyrazinamide was prescribed in 90.3% of cases, broadly in keeping with existing treatment guidelines. However, considerable variability was observed both in the drug regimens employed, and in the duration of initial and continuation phases of chemotherapy. Treatment regimens were therefore frequently at variance with published recommendations. Among patients prescribed drug regimens other than those recommended satisfactory completion of therapy was less common. Microbiological confirmation was provided for 84% of cases in which clinical samples were submitted. However, in approximately 11% of cases, no clinical samples were submitted. Closer adherence to existing treatment guidelines and more rigorous pursuit of microbiological confirmation should further improve the overall management of pulmonary TB in Scotland.

Palliative care at home: an audit of cancer deaths in Grampian region

BACKGROUND

Ninety per cent of the last year of life of cancer patients is spent at home. Some studies have suggested that care in this setting is often suboptimal. Information on the standard of palliative care delivered at home by general practitioners (GPs) and their teams is limited, and clarification of the problems faced is needed.

AIM

To audit the home-based palliative care of patients dying of cancer.

METHOD

Matched postal questionnaires were sent to the GPs and nurses of 1086 successive patients dying of cancer in whatever setting in the Grampian region of Scotland some six weeks after the death to establish the professionals' perception of symptom control, communication problems, use of services, and information given to patients and relatives.

RESULTS

Response rates were 88.8% for GPs (964 out of 1086) and 87.1% for nurses (325 out of 375 that were passed on to nurses). Two-thirds of patients received palliative care at home. Pain was poorly controlled in 15.7%, and poor control of other symptoms ranged from 13.8% (nausea and vomiting) to 21% (depression and dyspnoea). Communication difficulties were present in 93.7% of cases, although only 5.2% of these were of a major nature. District nurses were involved in 76.7% of cases and Macmillan nurses in 28.0%. Twenty-six per cent of referrals to district nurses were assessed as being late in the course of the illness. Patients were fully informed about the diagnosis in 66.3% of cases and about the prognosis in 55.4%. General practitioners were more likely to report the presence of communication problems between themselves and the patient (when compared with nurses: 43.9% versus 28.0%), more likely to report that patients were 'not at all informed' about self-help groups (57.5% versus 36.3%), and were less likely to report the involvement of occupational therapists (21.8% versus 39.7%).

CONCLUSIONS

Levels of reporting of poor symptom control by professionals was much lower than levels reported by relatives in other studies, but there was no difference between the reporting of GPs and nurses. However, a number of areas were identified where care could be enhanced by improved teamwork and further education and training in symptom control, as well as in communication, use of services, and information provision.

IS6110 transposition and evolutionary scenario of the direct repeat locus in a group of closely related Mycobacterium tuberculosis strains

In recent years, various polymorphic loci and multicopy insertion elements have been discovered in the Mycobacterium tuberculosis genome, such as the direct repeat (DR) locus, the major polymorphic tandem repeats, the polymorphic GC-rich repetitive sequence, IS6110, and IS1081. These, especially IS6110 and the DR locus, have been widely used as genetic markers to differentiate M. tuberculosis isolates and will continue to be so used, due to the conserved nature of the genome of M. tuberculosis. However, little is known about the processes involved in generating these or of their relative rates of change. Without an understanding of the biological characteristics of these genetic markers, it is difficult to use them to their full extent for understanding the population genetics and epidemiology of M. tuberculosis. To address these points, we identified a cluster of 7 isolates in a collection of 101 clinical isolates and investigated them with various polymorphic genetic markers, which indicated that they were highly related to each other. This cluster provided a model system for the study of IS6110 transposition, evolution at the DR locus, and the effects of these on the determination of evolutionary relationships among M. tuberculosis strains. Our results suggest that IS6110 restriction fragment length polymorphism patterns are useful in grouping closely related isolates together; however, they can be misleading if used for making inferences about the evolutionary relationships between closely related isolates. DNA sequence analysis of the DR loci of these isolates revealed an evolutionary scenario, which, complemented with the information from IS6110, allowed a reconstruction of the evolutionary steps and relationships among these closely related isolates. Loss of the IS6110 copy in the DR locus was noted, and the mechanisms of this loss are discussed.

In-vitro sensitivities and treatment of less common mycobacteria

There are very few new agents available for the treatment of infections due to the less common mycobacteria. There have been very few systematic studies of in-vitro activity and fewer clinical trials. Yet such mycobacteria are an important cause of serious disease and often conventional antimycobacterial agents are unsuitable either because of in-vitro resistance of the pathogen concerned, or toxicity of one of the components of drug regimens. At present, newer macrolides and quinolones offer promise, but there is a need to extend the in-vitro studies already under way of newer agents against Mycobacterium avium and/or Mycobacterium tuberculosis, to the other, less common mycobacteria. The benzoxazinorifampicins, the oxazolidinones and the acridinones may prove to be of clinical value. In addition to more information on the in-vitro activity of newer agents, alone and in combination, based on systematic studies involving larger numbers of mycobacterial strains, we need clearer clinical information to enable therapeutic regimens to be formulated and validated. The British Thoracic Society study is but a first step. There need to be more.

Antimicrobial treatment of fish tank granuloma

Three patients with fish tank granuloma of the hand and forearm are reported. Each patient was treated with antimicrobial regimes which have rarely or never been previously used in this condition. Two patients responded well to treatment, one who received ciprofloxacin plus clarithromycin and another who was given clarithromycin plus ethambutol. The third patient received six different antimicrobial regimes before responding to a combination of rifabutin and ciprofloxacin. Our experience suggests that there now exist a number of effective alternatives to antimicrobials which have been traditionally used in the treatment of cutaneous Mycobacterium marinum infection.

Comparative activity of azithromycin against clinical isolates of mycobacteria

Azithromycin exhibited in-vitro activity against 20 clinical isolates of Mycobacterium avium complex for which the MIC90 was 32 mg/L and 22 clinical isolates of other mycobacteria but showed no activity against 20 isolates of Mycobacterium tuberculosis (MIC90 > 128 mg/L) nor against the single isolate of Mycobacterium marinum tested (MIC 128 mg/L). These results suggest that the drug may prove useful for the prophylaxis and treatment of infections due to non-tuberculous mycobacteria, including M. avium complex in patients with AIDS.

A double-blind comparative study of norfloxacin versus placebo in hospitalised elderly patients with asymptomatic bacteriuria

Patients over the age of 65 years with clear catch specimens of urine containing organisms sensitive to norfloxacin were blindly randomised to receive either norfloxacin in a dose of 400 mg twice daily for 7 days or a placebo for the same period. Urine cultures were repeated immediately prior to treatment, at the end of treatment and at 7 days, 1 month and 3 months after treatment. Physical and mental function were assessed by performing a Crighton Behavioural Rating Scale at the same time intervals. Observations were made on 29 each of subjects on norfloxacin and placebo. The proportions of patients abacteriuric at the end of treatment, 7 days and 3 months post- treatment were 16/24 (66%), 12/24 (50%) and 5/24 (21%) in the norfloxacin group and 10/26 (38%), 8/26 (31%) and 8/25 (32%) in the placebo group. Percentage calculations (and denominators) exclude those patients withdrawn or for whom there were no specimens available at the sampling interval in question. Means and 95% intervals for the Crighton Behaviour Rating Scales initially and at 3 months in subjects on norfloxacin were 18.1 (15.1-20.7) and 19.1 (16.2-21.9) respectively. The same figures for the placebo group were 15.7 (12.6-18.8) and 16.6 (13.7-19.5). It is concluded that a 7 day course of norfloxacin for the treatment of asymptomatic bacteriuria had no effect on the physical and mental function of elderly continuing care patients, and that one explanation for this is that there was a high rate of urinary re-infection.

Scottish national survey of tuberculosis notifications 1993 with special reference to the prevalence of HIV seropositivity

BACKGROUND

The study sought to determine the contribution of HIV seropositivity to the arrest of decline in tuberculosis notifications in Scotland.

METHODS

Survey forms relating to each tuberculosis notification in 1993 were completed by the notifying consultant. Voluntary anonymous HIV testing of tuberculosis cases aged under 65 was requested. Age, sex, ethnic status, country of birth, employment status, occupation, previous tuberculosis, contact status, risk factors for HIV infection, HIV serostatus of cases aged under 65, site, radiological extent, and bacteriological status of tuberculous disease were determined.

RESULTS

Five hundred and seventy four cases of tuberculosis were originally notified, of which 77 (14%) subsequently proved to be non-tuberculous and were therefore denotified. Of the 497 cases 423 (85%) were white and 58 (12%) were from the Indian subcontinent. Eighty five per cent of patients from the Indian subcontinent were aged < 55 years whereas 64% of white patients were aged > 55 years. Pulmonary disease was found in 74%, non-pulmonary in 22%, and combined disease in 4% of patients. Of 242 HIV tests performed, three were positive and five other HIV positive patients were known, giving an HIV positivity rate of 1.6% of all tuberculosis notifications in 1993. Annual notification rates for Scotland were 9.7 per 10(5) before and 8.7 per 10(5) after exclusion of previously treated cases; rates were 8.4 per 10(5) for the white population and 179 per 10(5) for those from the Indian subcontinent.

CONCLUSIONS

The study documents the distribution of tuberculous disease in Scotland by age, sex, site, and ethnic group for the first time. Notification practices, with respect to denotification, need to be improved. Infection with HIV is presently uncommon in cases of tuberculosis in Scotland but continued vigilance is essential.

Haemophilus parainfluenzae: an unusual case of psoas abscess

A case of Haemophilus parainfluenzae psoas abscess in a previously healthy 36-year-old man is reported here. The absence of any bowel pathology indicates that abscess formation occurred secondary to haematogenous spread of the organism.

Disseminated disease due to Mycobacterium avium complex in AIDS

We retrospectively analysed 46 cases of disseminated infection with Mycobacterium avium complex (MAC) within a cohort of 702 HIV-infected patients in Edinburgh. Clinical features were compared with case-matched controls (AIDS cases without disseminated MAC), and survival and progression times were controlled for confounding variables that influence survival. Disseminated MAC was diagnosed antemortem in 18% of AIDS patients, and was the AIDS-defining diagnosis in 6% of all AIDS cases. Concomitant colonization of respiratory and gastrointestinal tracts was common (61% and 48%, respectively). In 58% of cases, CD4+ counts were < 10 cells/mm3 (median 6 cells/mm3). Weight loss, anaemia, leucopenia, and elevated liver transaminases and alkaline phosphatase were significantly more common among cases than controls. Therapy was given in 74%, and not tolerated in 32%. Following AIDS diagnosis, disseminated MAC incidence was 14% at one year, 25% at 2 years and 36% at 3 years. Median survival after disseminated MAC diagnosis was 6 months, with shorter survival in untreated cases. However, overall survival from AIDS diagnosis was not significantly different between patients who did or did not develop disseminated MAC. Disseminated MAC contributes significantly to AIDS morbidity, and its incidence increases with prolonged AIDS survival. Although survival following diagnosis is short, the development of disseminated MAC in AIDS probably does not affect overall survival. In cohorts with a low incidence, an alternative to prophylaxis might be surveillance and early diagnosis.

Why disease due to Mycobacterium tuberculosis is less common than expected in HIV-positive patients in Edinburgh

By December 1993, only five cases of tuberculosis were observed in the 1030 HIV-positive patients in Edinburgh, U.K., although, on the basis of historical tuberculin skin test data, between four and eight new cases of tuberculosis were expected per year. Of 310 HIV-positive patients, none of the 19 (6.1%) who were tuberculin skin test positive had developed tuberculosis after 87 months (average) of follow-up. It is suggested that new or re-infection is a more common cause of tuberculosis in HIV-positive patients than reactivation. Restriction fragment length polymorphism typing of Mycobacterium tuberculosis strains could confirm this hypothesis and support currently suggested additional infection control procedures.

Commercially available versus home produced egg media for isolation of mycobacteria

AIMS

To compare the growth of clinical isolates of mycobacteria on in-house and commercial egg media.

METHODS

Fresh test media were inoculated with dilutions of the test organisms and growth, colonial morphology and microscopic appearance were compared blindly by two observers. The process was repeated after the test media had been stored for three months. The user friendliness of each of the test media was also assessed.

RESULTS

There was no difference in the microscopic appearance of any given mycobacterial species between different media. All of the test media grew the test species, although Mycobacterium bovis required four weeks on BioMerieux media, compared with two weeks on the other media. There was little obvious effect of storage on any of the media, except with M kansasii. Individual species gave characteristic colonial appearances on inhouse media; all of the commercial media gave non-specific colonial appearances that made presumptive identification very difficult. There were clear differences in the user friendliness of different media.

CONCLUSIONS

Although commercially available egg media in general gave good growth of mycobacteria, only in-house media combined good growth with useful colonial features.

Population genetics of Mycobacterium tuberculosis complex in Scotland analysed by pulsed-field gel electrophoresis

The results of typing of 121 strains in the Mycobacterium tuberculosis complex by PFGE are presented. Every isolate from patients in Scotland over a 3-month period for M. tuberculosis and for 1 year for M. bovis were included along with several laboratory strains including those of BCG. The PFGE results suggest that the population structure of all the strains in this complex is distinctly simple with limited genetic diversity and also suggest that M. bovis is not a distinct species.

Non-tuberculous pulmonary infections in Scotland: a cluster in Lothian?

BACKGROUND

A retrospective study was carried out to confirm the clinical impression that, in Lothian, non-tuberculous mycobacterial infections are as common as pulmonary tuberculosis.

METHODS

All pulmonary isolates of Mycobacterium tuberculosis/bovis and non-tuberculous mycobacteria in Scotland from April 1990 to March 1993, and the notes of all patients with M malmoense isolates in Lothian, were reviewed. Information on mycobacterial culture procedures in Scottish laboratories was obtained as part of an audit project.

RESULTS

Of all pulmonary isolates of mycobacteria in Lothian 53% (108/205) were non-tuberculous strains compared with 18% (140/800) for Scotland outside Lothian. Although comparable in population size and laboratory techniques, Lothian (108) had almost twice as many isolates of non-tuberculous mycobacteria as Glasgow (56), but the proportions of M malmoense and M avium intracellulare complex were similar in both areas. Of 41 patients with M malmoense isolates in Lothian 30 (75%) had clinically significant lung disease; only one was HIV positive.

CONCLUSIONS

Non-tuberculous mycobacteria pose an increasing clinical problem in Scotland as a cause of pulmonary disease. There is a cluster of cases with M malmoense infection in Lothian which cannot be attributed to the high local prevalence of HIV.

Pulmonary tuberculosis in overseas students of higher education is increasing in Edinburgh

In Edinburgh in 1991 a relative excess of pulmonary TB cases in the 15-34 year age group was recorded. Five of 17 notifications in this age group were of overseas students of higher education: three aged 21-29 from Central Africa, one 27-year-old Asian and one 26-year-old Western European. One of the African students was seropositive for HIV infection. Disease presented clinically on average 31 months after entry to the U.K. (range 6-48 months). Four students had smear positive disease. Two patients had had normal chest radiographs 1 and 2 years previously on entry to the U.K.; three students had not previously been radiologically screened. We suggest that students from countries with a high prevalence of tuberculosis should be screened on entry to their course of education and that student health services should develop and maintain a high index of suspicion for tuberculosis in these students.

Comparison of techniques for antimicrobial susceptibility testing of mycobacteria

AIMS

To evaluate adenosine triphosphate (ATP) bioluminescence as a rapid technique for antimicrobial susceptibility testing of Mycobacterium spp by comparing it with conventional and radiometric methods, and to assess its potential for use in clinical microbiology laboratories.

METHODS

115 clinical isolates from a wide range of mycobacterial species and four control organisms of known susceptibility were tested against six antimicrobial agents. Minimum inhibitory concentrations (MICs) were determined after 4-6 weeks' incubation on Middlebrook 7H10 agar. Susceptibility was also determined radiometrically using a Bactec 460, and by bioluminescent assay of ATP using a 1250 luminometer (LKB-Wallac).

RESULTS

Susceptibility results after 7 days showed excellent correlation with conventionally determined MICs. 714 susceptibility tests were performed by both techniques, with seven major discrepancies between the two systems. For pyrazinamide, agreement was 100%, but five strains of M tuberculosis, including one control, and 11 mycobacteria other than M tuberculosis (MOTT) failed to grow on Middlebrook agar at pH 5.5. 606 tests were performed by radiometry, with four major discrepancies between this technique and ATP bioluminescence. No particular species of Mycobacterium gave aberrant results. Contamination was a problem; 12 of the 119 strains tested were contaminated at day 1 and had to be repeated before results were obtained. Contamination of individual tests increased significantly after 7 days of incubation.

CONCLUSIONS

ATP bioluminescence can be used to monitor mycobacterial growth in fluid culture media; the technique has considerable potential for rapid susceptibility testing. Advantages include lower initial cost of analytical equipment, lower reagent cost per test, and the use of non-radioactive substrates.

Perceived exertion. Antecedents and applications

The field of perceived exertion has largely concerned itself with the problem of identifying the primary antecedents to this psychophysiological phenomenon. A vast literature has evolved addressing this problem, but it is fraught with contradictions. At this stage a comprehensive theory of perceived exertion does not exist. It is generally accepted that perception of exertion is dominated by physiological determinants. Physiological sensory cues have been separated into 2 categories: local factors (sensations from the working muscles and joints), and central factors (sensations from the cardiopulmonary system). Major reviews in this area generally agree that local factors dominate perception of exertion. Recent work in perceived exertion has placed an emphasis on examining the contributing psychological factors. Research into the psychological factors affecting perceived exertion has been highly fragmented with no apparent theoretical framework as a base. At the same time it is clear that an integration of psychological and physiological variables is required to obtain theoretically meaningful knowledge of this multidimensional construct. The assumed dominance of physiological factors has been challenged by the contention that in field situations, in which a variety of social psychological influences operate, psychological determinants of perceived exertion may be vastly more influential than previously estimated. Identification of the primary determinants of perceived exertion and knowledge of how these factors are integrated is vital for a concrete theory of perceived exertion to evolve.