Outbreak of isoniazid resistant tuberculosis in north London

Isoniazid-monoresistant tuberculosis in France: Risk factors, treatment outcomes and adverse events

OBJECTIVES

Isoniazid-monoresistant tuberculosis (HR-TB) is the most prevalent form of drug-resistant TB worldwide and in France and is associated with poorer treatment outcomes compared with drug-susceptible TB (DS-TB). The objective of this study was to determine the characteristics of HR-TB patients in France and to compare outcomes and safety of treatment for HR-TB and DS-TB.

METHODS

We performed a case-control multicenter study to identify risk factors associated with HR-TB and compare treatment outcomes and safety between HR-TB patients and DS-TB patients.

RESULTS

Characteristics of 99 HR-TB patients diagnosed and treated in the university hospitals of Paris, Lille, Caen and Strasbourg were compared with 99 DS-TB patients. Female sex (OR = 2.2; 1.0-4.7), birth in the West-Pacific World Health Organization region (OR = 4.6; 1.1-18.7) and resistance to streptomycin (OR = 77.5; 10.1-594.4) were found to be independently associated with HR-TB. Rates of treatment success did not differ significantly between HR-TB and DS-TB.

CONCLUSIONS

Factors associated with HR-TB are not significant enough to efficiently screen TB patients at risk of HR-TB. The systematic implementation of rapid molecular testing on clinical samples remains the only effective way to make the early diagnosis of HR-TB and adapt treatment.

Transmission analysis of a large tuberculosis outbreak in London: a mathematical modelling study using genomic data

Outbreaks of tuberculosis (TB) - such as the large isoniazid-resistant outbreak centred on London, UK, which originated in 1995 - provide excellent opportunities to model transmission of this devastating disease. Transmission chains for TB are notoriously difficult to ascertain, but mathematical modelling approaches, combined with whole-genome sequencing data, have strong potential to contribute to transmission analyses. Using such data, we aimed to reconstruct transmission histories for the outbreak using a Bayesian approach, and to use machine-learning techniques with patient-level data to identify the key covariates associated with transmission. By using our transmission reconstruction method that accounts for phylogenetic uncertainty, we are able to identify 21 transmission events with reasonable confidence, 9 of which have zero SNP distance, and a maximum distance of 3. Patient age, alcohol abuse and history of homelessness were found to be the most important predictors of being credible TB transmitters.

Management and control of tuberculosis control in socially complex groups: a research programme including three RCTs

Background

Socially complex groups, including people experiencing homelessness, prisoners and drug users, have very high levels of tuberculosis, often complicated by late diagnosis and difficulty in adhering to treatment.

Objective

To assess a series of interventions to improve tuberculosis control in socially complex groups.

Design

A series of observational surveys, evaluations and trials of interventions.

Setting

The pan-London Find&Treat service, which supports tuberculosis screening and case management in socially complex groups across London.

Participants

Socially complex groups with tuberculosis or at risk of tuberculosis, including people experiencing homelessness, prisoners, drug users and those at high risk of poor adherence to tuberculosis treatment.

Interventions and main outcome measures

We screened 491 people in homeless hostels and 511 people in prison for latent tuberculosis infection, human immunodeficiency virus, hepatitis B and hepatitis C. We evaluated an NHS-led prison radiographic screening programme. We conducted a cluster randomised controlled trial (2348 eligible people experiencing homelessness in 46 hostels) of the effectiveness of peer educators (22 hostels) compared with NHS staff (24 hostels) at encouraging the uptake of mobile radiographic screening. We initiated a trial of the use of point-of-care polymerase chain reaction diagnostics to rapidly confirm tuberculosis alongside mobile radiographic screening. We undertook a randomised controlled trial to improve treatment adherence, comparing face-to-face, directly observed treatment with video-observed treatment using a smartphone application. The primary outcome was completion of ≥ 80% of scheduled treatment observations over the first 2 months following enrolment. We assessed the cost-effectiveness of latent tuberculosis screening alongside radiographic screening of people experiencing homelessness. The costs of video-observed treatment and directly observed treatment were compared.

Results

In the homeless hostels, 16.5% of people experiencing homelessness had latent tuberculosis infection, 1.4% had current hepatitis B infection, 10.4% had hepatitis C infection and 1.0% had human immunodeficiency virus infection. When a quality-adjusted life-year is valued at £30,000, the latent tuberculosis screening of people experiencing homelessness was cost-effective provided treatment uptake was ≥ 25% (for a £20,000 quality-adjusted life-year threshold, treatment uptake would need to be > 50%). In prison, 12.6% of prisoners had latent tuberculosis infection, 1.9% had current hepatitis B infection, 4.2% had hepatitis C infection and 0.0% had human immunodeficiency virus infection. In both settings, levels of latent tuberculosis infection and blood-borne viruses were higher among injecting drug users. A total of 1484 prisoners were screened using chest radiography over a total of 112 screening days (new prisoner screening coverage was 43%). Twenty-nine radiographs were reported as potentially indicating tuberculosis. One prisoner began, and completed, antituberculosis treatment in prison. In the cluster randomised controlled trial of peer educators to increase screening uptake, the median uptake was 45% in the control arm and 40% in the intervention arm (adjusted risk ratio 0.98, 95% confidence interval 0.80 to 1.20). A rapid diagnostic service was established on the mobile radiographic unit but the trial of rapid diagnostics was abandoned because of recruitment and follow-up difficulties. We randomly assigned 112 patients to video-observed treatment and 114 patients to directly observed treatment. Fifty-eight per cent of those recruited had a history of homelessness, addiction, imprisonment or severe mental health problems. Seventy-eight (70%) of 112 patients on video-observed treatment achieved the primary outcome, compared with 35 (31%) of 114 patients on directly observed treatment (adjusted odds ratio 5.48, 95% confidence interval 3.10 to 9.68; p < 0.0001). Video-observed treatment was superior to directly observed treatment in all demographic and social risk factor subgroups. The cost for 6 months of treatment observation was £1645 for daily video-observed treatment, £3420 for directly observed treatment three times per week and £5700 for directly observed treatment five times per week.

Limitations

Recruitment was lower than anticipated for most of the studies. The peer advocate study may have been contaminated by the fact that the service was already using peer educators to support its work.

Conclusions

There are very high levels of latent tuberculosis infection among prisoners, people experiencing homelessness and drug users. Screening for latent infection in people experiencing homelessness alongside mobile radiographic screening would be cost-effective, providing the uptake of treatment was 25–50%. Despite ring-fenced funding, the NHS was unable to establish static radiographic screening programmes. Although we found no evidence that peer educators were more effective than health-care workers in encouraging the uptake of mobile radiographic screening, there may be wider benefits of including peer educators as part of the Find&Treat team. Utilising polymerase chain reaction-based rapid diagnostic testing on a mobile radiographic unit is feasible. Smartphone-enabled video-observed treatment is more effective and cheaper than directly observed treatment for ensuring that treatment is observed.

Future work

Trials of video-observed treatment in high-incidence settings are needed.

Trial registration

Current Controlled Trials ISRCTN17270334 and ISRCTN26184967.

Funding

This project was funded by the National Institute for Health Research (NIHR) Programme Grants for Applied Research programme and will be published in full in Programme Grants for Applied Research; Vol. 8, No. 9. See the NIHR Journals Library website for further project information.

Challenges posed by COVID-19 to people who inject drugs and lessons from other outbreaks

INTRODUCTION

In light of the COVID-19 pandemic, considerable effort is going into identifying and protecting those at risk. Criminalization, stigmatization and the psychological, physical, behavioural and economic consequences of substance use make people who inject drugs (PWID) extremely vulnerable to many infectious diseases. While relationships between drug use and blood-borne and sexually transmitted infections are well studied, less attention has been paid to other infectious disease outbreaks among PWID.

DISCUSSION

COVID-19 is likely to disproportionally affect PWID due to a high prevalence of comorbidities that make the disease more severe, unsanitary and overcrowded living conditions, stigmatization, common incarceration, homelessness and difficulties in adhering to quarantine, social distancing or self-isolation mandates. The COVID-19 pandemic also jeopardizes essential for PWID services, such as needle exchange or substitution therapy programmes, which can be affected both in a short- and a long-term perspective. Importantly, there is substantial evidence of other infectious disease outbreaks in PWID that were associated with factors that enable COVID-19 transmission, such as poor hygiene, overcrowded living conditions and communal ways of using drugs.

CONCLUSIONS

The COVID-19 crisis might increase risks of homelessnes, overdoses and unsafe injecting and sexual practices for PWID. In order to address existing inequalities, consultations with PWID advocacy groups are vital when designing inclusive health response to the COVID-19 pandemic.

Isoniazid-resistant tuberculosis: a cause for concern?

The drug isoniazid (INH) is a key component of global tuberculosis (TB) control programmes. It is estimated, however, that 16.1% of TB disease cases in the former Soviet Union countries and 7.5% of cases outside of these settings have non-multidrug-resistant (MDR) INH resistance. Resistance has been linked to poorer treatment outcomes, post-treatment relapse and death, at least for specific sites of disease. Multiple genetic loci are associated with phenotypic resistance; however, the relationship between genotype and phenotype is complex, and restricts the use of rapid sequencing techniques as part of the diagnostic process to determine the most appropriate treatment regimens for patients. The burden of resistance also influences the usefulness of INH preventive therapy. Despite seven decades of INH use, our knowledge in key areas such as the epidemiology of resistant strains, their clinical consequences, whether tailored treatment regimens are required and the role of INH resistance in fuelling the MDR-TB epidemic is limited. The importance of non-MDR INH resistance needs to be re-evaluated both globally and by national TB control programmes.

An audit of tuberculosis health services in prisons and immigration removal centres

Background

Tuberculosis (TB) is the second leading cause of death worldwide due to a single infectious agent. Rates of active TB in places of prescribed detention (PPD), which include Prisons, Young Offender Institutions and Immigration Removal Centres, are high compared with the general population. PPD therefore present an opportunity to develop targeted health programmes for TB control. This audit aims to assess current service provisions and identify barriers to achieving best practice standards in PPD across London.

Methods

Twelve healthcare teams within PPD commissioned by NHS England (London Region) were included in the audit. Services were evaluated against the National Institute for Health and Care Excellence standards for TB best practice.

Results

None of the health providers with a digital X-ray machine were conducting active case finding in new prisoners and no health providers routinely conduct Latent TB infection testing and preventative treatment. Barriers to implementing standards include the lack of staff skills and staff skills mix, structural and technical barriers, and demands of custodial and health services.

Conclusions

This audit restates the importance of national public health TB strategies to consider healthcare provisions across PPD.

Twenty years and counting: epidemiology of an outbreak of isoniazid-resistant tuberculosis in England and Wales, 1995 to 2014

An outbreak of isoniazid-resistant tuberculosis first identified in London has now been ongoing for 20 years, making it the largest drug-resistant outbreak of tuberculosis documented to date worldwide. We identified culture-confirmed cases with indistinguishable molecular strain types and extracted demographic, clinical, microbiological and social risk factor data from surveillance systems. We summarised changes over time and used kernel-density estimation and k-function analysis to assess geographic clustering. From 1995 to 2014, 508 cases were reported, with a declining trend in recent years. Overall, 70% were male (n = 360), 60% born in the United Kingdom (n = 306), 39% white (n = 199), and 26% black Caribbean (n = 134). Median age increased from 25 years in the first 5 years to 42 in the last 5. Approximately two thirds of cases reported social risk factors: 45% drug use (n = 227), 37% prison link (n = 189), 25% homelessness (n = 125) and 13% alcohol dependence (n = 64). Treatment was completed at 12 months by 52% of cases (n = 206), and was significantly lower for those with social risk factors (p < 0.05), but increased over time for all patients (p < 0.05). The outbreak remained focused in north London throughout. Control of this outbreak requires continued efforts to prevent and treat further active cases through targeted screening and enhanced case management.

Multiple large clusters of tuberculosis in London: a cross-sectional analysis of molecular and spatial data

Large outbreaks of tuberculosis (TB) represent a particular threat to disease control because they reflect multiple instances of active transmission. The extent to which long chains of transmission contribute to high TB incidence in London is unknown. We aimed to estimate the contribution of large clusters to the burden of TB in London and identify risk factors.

We identified TB patients resident in London notified between 2010 and 2014, and used 24-locus mycobacterial interspersed repetitive units–variable number tandem repeat strain typing data to classify cases according to molecular cluster size. We used spatial scan statistics to test for spatial clustering and analysed risk factors through multinomial logistic regression.

TB isolates from 7458 patients were included in the analysis. There were 20 large molecular clusters (with n>20 cases), comprising 795 (11%) of all cases; 18 (90%) large clusters exhibited significant spatial clustering. Cases in large clusters were more likely to be UK born (adjusted odds ratio 2.93, 95% CI 2.28–3.77), of black-Caribbean ethnicity (adjusted odds ratio 3.64, 95% CI 2.23–5.94) and have multiple social risk factors (adjusted odds ratio 3.75, 95% CI 1.96–7.16).

Large clusters of cases contribute substantially to the burden of TB in London. Targeting interventions such as screening in deprived areas and social risk groups, including those of black ethnicities and born in the UK, should be a priority for reducing transmission.

Large clusters contribute substantially to the burden of tuberculosis in London, indicating ongoing transmissionhttp://ow.ly/3xk23068P6w

Tuberculosis in migrants moving from high-incidence to low-incidence countries: a population-based cohort study of 519 955 migrants screened before entry to England, Wales, and Northern Ireland

BACKGROUND

Tuberculosis elimination in countries with a low incidence of the disease necessitates multiple interventions, including innovations in migrant screening. We examined a cohort of migrants screened for tuberculosis before entry to England, Wales, and Northern Ireland and tracked the development of disease in this group after arrival.

METHODS

As part of a pilot pre-entry screening programme for tuberculosis in 15 countries with a high incidence of the disease, the International Organization for Migration screened all applicants for UK visas aged 11 years or older who intended to stay for more than 6 months. Applicants underwent a chest radiograph, and any with results suggestive of tuberculosis underwent sputum testing and culture testing (when available). We tracked the development of tuberculosis in those who tested negative for the disease and subsequently migrated to England, Wales, and Northern Ireland with the Enhanced Tuberculosis Surveillance system. Primary outcomes were cases of all forms of tuberculosis (including clinically diagnosed cases), and bacteriologically confirmed pulmonary tuberculosis.

FINDINGS

Our study cohort was 519 955 migrants who were screened for tuberculosis before entry to the UK between Jan 1, 2006, and Dec 31, 2012. Cases notified on the Enhanced Tuberculosis Surveillance system between Jan 1, 2006, and Dec 31, 2013, were included. 1873 incident cases of all forms of tuberculosis were identified, and, on the basis of data for England, Wales, and Northern Ireland, the estimated incidence of all forms of tuberculosis in migrants screened before entry was 147 per 100 000 person-years (95% CI 140-154). The estimated incidence of bacteriologically confirmed pulmonary tuberculosis in migrants screened before entry was 49 per 100 000 person-years (95% CI 45-53). Migrants whose chest radiographs were compatible with active tuberculosis but with negative pre-entry microbiological results were at increased risk of tuberculosis compared with those with no radiographic abnormalities (incidence rate ratio 3·2, 95% CI 2·8-3·7; p<0·0001). Incidence of tuberculosis after migration increased significantly with increasing WHO-estimated prevalence of tuberculosis in migrants' countries of origin. 35 of 318 983 pre-entry screened migrants included in a secondary analysis with typing data were assumed index cases. Estimates of the rate of assumed reactivation tuberculosis ranged from 46 (95% CI 42-52) to 91 (82-102) per 100 000 population.

INTERPRETATION

Migrants from countries with a high incidence of tuberculosis screened before being granted entry to low-incidence countries pose a negligible risk of onward transmission but are at increased risk of tuberculosis, which could potentially be prevented through identification and treatment of latent infection in close collaboration with a pre-entry screening programme.

FUNDING

Wellcome Trust, UK National Institute for Health Research, UK Medical Research Council, Public Health England, and Department of Health Policy Research Programme.

Whole Genome Sequence Analysis of a Large Isoniazid-Resistant Tuberculosis Outbreak in London: A Retrospective Observational Study

BACKGROUND

A large isoniazid-resistant tuberculosis outbreak centred on London, United Kingdom, has been ongoing since 1995. The aim of this study was to investigate the power and value of whole genome sequencing (WGS) to resolve the transmission network compared to current molecular strain typing approaches, including analysis of intra-host diversity within a specimen, across body sites, and over time, with identification of genetic factors underlying the epidemiological success of this cluster.

METHODS AND FINDINGS

We sequenced 344 outbreak isolates from individual patients collected over 14 y (2 February 1998-22 June 2012). This demonstrated that 96 (27.9%) were indistinguishable, and only one differed from this major clone by more than five single nucleotide polymorphisms (SNPs). The maximum number of SNPs between any pair of isolates was nine SNPs, and the modal distance between isolates was two SNPs. WGS was able to reveal the direction of transmission of tuberculosis in 16 cases within the outbreak (4.7%), including within a multidrug-resistant cluster that carried a rare rpoB mutation associated with rifampicin resistance. Eleven longitudinal pairs of patient pulmonary isolates collected up to 48 mo apart differed from each other by between zero and four SNPs. Extrapulmonary dissemination resulted in acquisition of a SNP in two of five cases. WGS analysis of 27 individual colonies cultured from a single patient specimen revealed ten loci differed amongst them, with a maximum distance between any pair of six SNPs. A limitation of this study, as in previous studies, is that indels and SNPs in repetitive regions were not assessed due to the difficulty in reliably determining this variation.

CONCLUSIONS

Our study suggests that (1) certain paradigms need to be revised, such as the 12 SNP distance as the gold standard upper threshold to identify plausible transmissions; (2) WGS technology is helpful to rule out the possibility of direct transmission when isolates are separated by a substantial number of SNPs; (3) the concept of a transmission chain or network may not be useful in institutional or household settings; (4) the practice of isolating single colonies prior to sequencing is likely to lead to an overestimation of the number of SNPs between cases resulting from direct transmission; and (5) despite appreciable genomic diversity within a host, transmission of tuberculosis rarely results in minority variants becoming dominant. Thus, whilst WGS provided some increased resolution over variable number tandem repeat (VNTR)-based clustering, it was insufficient for inferring transmission in the majority of cases.

Genetic variation in Mycobacterium tuberculosis isolates from a London outbreak associated with isoniazid resistance

BACKGROUND

The largest outbreak of isoniazid-resistant (INH-R) Mycobacterium tuberculosis in Western Europe is centred in North London, with over 400 cases diagnosed since 1995. In the current study, we evaluated the genetic variation in a subset of clinical samples from the outbreak with the hypothesis that these isolates have unique biological characteristics that have served to prolong the outbreak.

METHODS

Fitness assays, mutation rate estimation, and whole-genome sequencing were performed to test for selective advantage and compensatory mutations.

RESULTS

This detailed analysis of the genetic variation of these INH-R samples suggests that this outbreak consists of successful, closely related, circulating strains with heterogeneous resistance profiles and little or no associated fitness cost or impact on their mutation rate.

CONCLUSIONS

Specific deletions and SNPs could be a peculiar feature of these INH-R M. tuberculosis isolates, and could potentially explain their persistence over the years.

Systematic review, meta-analysis and economic modelling of molecular diagnostic tests for antibiotic resistance in tuberculosis

BACKGROUND

Drug-resistant tuberculosis (TB), especially multidrug-resistant (MDR, resistance to rifampicin and isoniazid) disease, is associated with a worse patient outcome. Drug resistance diagnosed using microbiological culture takes days to weeks, as TB bacteria grow slowly. Rapid molecular tests for drug resistance detection (1 day) are commercially available and may promote faster initiation of appropriate treatment.

OBJECTIVES

To (1) conduct a systematic review of evidence regarding diagnostic accuracy of molecular genetic tests for drug resistance, (2) conduct a health-economic evaluation of screening and diagnostic strategies, including comparison of alternative models of service provision and assessment of the value of targeting rapid testing at high-risk subgroups, and (3) construct a transmission-dynamic mathematical model that translates the estimates of diagnostic accuracy into estimates of clinical impact.

REVIEW METHODS AND DATA SOURCES

A standardised search strategy identified relevant studies from EMBASE, PubMed, MEDLINE, Bioscience Information Service (BIOSIS), System for Information on Grey Literature in Europe Social Policy & Practice (SIGLE) and Web of Science, published between 1 January 2000 and 15 August 2013. Additional 'grey' sources were included. Quality was assessed using quality assessment of diagnostic accuracy studies version 2 (QUADAS-2). For each diagnostic strategy and population subgroup, a care pathway was constructed to specify which medical treatments and health services that individuals would receive from presentation to the point where they either did or did not complete TB treatment successfully. A total cost was estimated from a health service perspective for each care pathway, and the health impact was estimated in terms of the mean discounted quality-adjusted life-years (QALYs) lost as a result of disease and treatment. Costs and QALYs were both discounted at 3.5% per year. An integrated transmission-dynamic and economic model was used to evaluate the cost-effectiveness of introducing rapid molecular testing (in addition to culture and drug sensitivity testing). Probabilistic sensitivity analysis was performed to evaluate the impact on cost-effectiveness of diagnostic and treatment time delays, diagnosis and treatment costs, and associated QALYs.

RESULTS

A total of 8922 titles and abstracts were identified, with 557 papers being potentially eligible. Of these, 56 studies contained sufficient test information for analysis. All three commercial tests performed well when detecting drug resistance in clinical samples, although with evidence of heterogeneity between studies. Pooled sensitivity for GenoType® MTBDRplus (Hain Lifescience, Nehren, Germany) (isoniazid and rifampicin resistance), INNO-LiPA Rif.TB® (Fujirebio Europe, Ghent, Belgium) (rifampicin resistance) and Xpert® MTB/RIF (Cepheid Inc., Sunnyvale, CA, USA) (rifampicin resistance) was 83.4%, 94.6%, 95.4% and 96.8%, respectively; equivalent pooled specificity was 99.6%, 98.2%, 99.7% and 98.4%, respectively. Results of the transmission model suggest that all of the rapid assays considered here, if added to the current diagnostic pathway, would be cost-saving and achieve a reduction in expected QALY loss compared with current practice. GenoType MTBDRplus appeared to be the most cost-effective of the rapid tests in the South Asian population, although results were similar for GeneXpert. In all other scenarios GeneXpert appeared to be the most cost-effective strategy.

CONCLUSIONS

Rapid molecular tests for rifampicin and isoniazid resistance were sensitive and specific. They may also be cost-effective when added to culture drug susceptibility testing in the UK. There is global interest in point-of-care testing and further work is needed to review the performance of emerging tests and the wider health-economic impact of decentralised testing in clinics and primary care, as well as non-health-care settings, such as shelters and prisons.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42011001537.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Prevalence and correlates of latent tuberculosis infection among employees of a high security prison in Malaysia

OBJECTIVES

Although prison employees share the same tuberculosis (TB) risk environment with prisoners, the magnitude of TB problems among prison employees is unknown in most resource-limited prisons. This survey was conducted to investigate the prevalence and correlates of tuberculin skin test (TST) positivity among employees in Malaysia's largest prison.

METHODS

Consented, full-time prison employees were interviewed using a structured questionnaire that included sociodemographic data, history of working in the correctional system and TB-related risk. TST was placed intradermally and read after 48-72 h. Induration size of ≥10 mm was considered positive. Logistic regression analyses were conducted to explore associations with TST positivity.

RESULTS

Of the 445 recruited prison employees, 420 (94.4%) had complete data. Most were young (median=30.0 years) men (88.8%) who had only worked at this prison (76.4%) for a median total employment period of 60 months (IQR 34.5-132.0). The majority were correctional officers, while civilian employees represented only 7.6% of the sample. Only 26 (6.2%) reported having ever been screened for TB since employment. Prevalence of TST positivity was 81% and was independently associated with longer (≥12 months) prison employment (AOR 4.9; 95% CI 1.5 to 15.9) and current tobacco smoking (AOR=1.9, 95% CI 1.2 to 3.2).

CONCLUSIONS

Latent TB prevalence was high in this sample, approximating that of prisoners in this setting, perhaps suggesting within prison TB transmission in this facility. Formal TB control programmes for personnel and prisoners alike are urgently needed within the Malaysian correctional system.

Correlates between models of virulence for Mycobacterium tuberculosis among isolates of the Central Asian lineage: a case for lysozyme resistance testing?

Virulence factors (VFs) contribute to the emergence of new human Mycobacterium tuberculosis strains, are lineage dependent, and are relevant to the development of M. tuberculosis drugs/vaccines. VFs were sought within M. tuberculosis lineage 3, which has the Central Asian (CAS) spoligotype. Three isolates were selected from clusters previously identified as dominant in London, United Kingdom. Strain-associated virulence was studied in guinea pig, monocyte-derived macrophage, and lysozyme resistance assays. Whole-genome sequencing, single nucleotide polymorphism (SNP) analysis, and a literature review contributed to the identification of SNPs of interest. The animal model revealed borderline differences in strain-associated pathogenicity. Ex vivo, isolate C72 exhibited statistically significant differences in intracellular growth relative to C6 and C14. SNP candidates inducing lower fitness levels included 123 unique nonsynonymous SNPs, including three located in genes (lysX, caeA, and ponA2) previously identified as VFs in the laboratory-adapted reference strain H37Rv and shown to confer lysozyme resistance. C72 growth was most affected by lysozyme in vitro. A BLAST search revealed that all three SNPs of interest (C35F, P76Q, and P780R) also occurred in Tiruvallur, India, and in Uganda. Unlike C72, however, no single isolate identified through BLAST carried all three SNPs simultaneously. CAS isolates representative of three medium-sized human clusters demonstrated differential outcomes in models commonly used to estimate strain-associated virulence, supporting the idea that virulence varies within, not just across, M. tuberculosis lineages. Three VF SNPs of interest were identified in two additional locations worldwide, which suggested independent selection and supported a role for these SNPs in virulence. The relevance of lysozyme resistance to strain virulence remains to be established.

Prospective evaluation of a complex public health intervention: lessons from an initial and follow-up cross-sectional survey of the tuberculosis strain typing service in England

Background

The national tuberculosis strain typing service (TB-STS) was introduced in England in 2010. The TB-STS involves MIRU-VNTR typing of isolates from all TB patients for the prospective identification, reporting and investigation of TB strain typing clusters. As part of a mixed-method evaluation, we report on a repeated cross-sectional survey to illustrate the challenges surrounding the evaluation of a complex national public health intervention.

Methods

An online initial and follow-up questionnaire survey assessed the knowledge, attitudes and practices of public health staff, physicians and nurses working in TB control in November 2010 and March 2012. It included questions on the implementation, experience and uptake of the TB-STS. Participants that responded to both surveys were included in the analysis.

Results

248 participants responded to the initial survey and 137 of these responded to the follow-up survey (56% retention).

Knowledge: A significant increase in knowledge was observed, including a rise in the proportion of respondents who had received training (28.6% to 67.9%, p = 0.003), and the self-rated knowledge of how to use strain typing had improved (‘no knowledge’ decreased from 43.2% to 27.4%).

Attitudes: The majority of respondents found strain typing useful; the proportion that reported strain typing to be useful was similar across the two surveys (95.7% to 94.7%, p = 0.67).

Practices: There were significant increases between the initial and follow-up surveys in the number of respondents who reported using strain typing (57.0% to 80.5%, p < 0.001) and the proportion of time health protection staff spent on investigating TB (2.74% to 7.08%, p = 0.04).

Conclusions

Evaluation of a complex public health intervention is challenging. In this example, the immediate national roll-out of the TB-STS meant that a controlled survey design was not possible. This study informs the future development of the TB-STS by identifying the need for training to reach wider professional groups, and argues for its continuation based on service users’ perception that it is useful. By highlighting the importance of a well-defined sampling frame, collecting baseline information, and including all stakeholders, it provides lessons for the implementation of similar services in other countries and future evaluations of public health interventions.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2458-14-1023) contains supplementary material, which is available to authorized users.

The re-emergence of tuberculosis: what have we learnt from molecular epidemiology?

Tuberculosis (TB) has re-emerged over the past two decades: in industrialized countries in association with immigration, and in Africa owing to the human immunodeficiency virus epidemic. Drug-resistant TB is a major threat worldwide. The variable and uncertain impact of TB control necessitates not only better tools (diagnostics, drugs, and vaccines), but also better insights into the natural history and epidemiology of TB. Molecular epidemiological studies over the last two decades have contributed to such insights by answering long-standing questions, such as the proportion of cases attributable to recent transmission, risk factors for recent transmission, the occurrence of multiple Mycobacterium tuberculosis infection, and the proportion of recurrent TB cases attributable to re-infection. M. tuberculosis lineages have been identified and shown to be associated with geographical origin. The Beijing genotype is strongly associated with multidrug resistance, and may have escaped from bacille Calmette-Guérin-induced immunity. DNA fingerprinting has quantified the importance of institutional transmission and laboratory cross-contamination, and has helped to focus contact investigations. Questions to be answered in the near future with whole genome sequencing include identification of chains of transmission within clusters of patients, more precise quantification of mixed infection, and transmission probabilities and rates of progression from infection to disease of various M. tuberculosis lineages, as well as possible variations in vaccine efficacy by lineage. Perhaps most importantly, dynamics in the population structure of M. tuberculosis in response to control measures in high-prevalence areas should be better understood.

Tuberculosis in UK cities: workload and effectiveness of tuberculosis control programmes

Background

Tuberculosis (TB) has increased within the UK and, in response, targets for TB control have been set and interventions recommended. The question was whether these had been implemented and, if so, had they been effective in reducing TB cases.

Methods

Epidemiological data were obtained from enhanced surveillance and clinics. Primary care trusts or TB clinics with an average of > 100 TB cases per year were identified and provided reflections on the reasons for any change in their local incidence, which was compared to an audit against the national TB plan.

Results

Access to data for planning varied (0-22 months). Sputum smear status was usually well recorded within the clinics. All cities had TB networks, a key worker for each case, free treatment and arrangements to treat HIV co-infection. Achievement of targets in the national plan correlated well with change in workload figures for the commissioning organizations (Spearman's rank correlation R = 0.8, P < 0.01) but not with clinic numbers. Four cities had not achieved the target of one nurse per 40 notifications (Birmingham, Bradford, Manchester and Sheffield). Compared to other cities, their loss to follow-up during treatment was usually > 6% (χ² = 4.2, P < 0.05), there was less TB detected by screening and less outreach. Manchester was most poorly resourced and showed the highest rate of increase of TB. Direct referral from radiology, sputum from primary care and outreach workers were cited as important in TB control.

Conclusion

TB control programmes depend on adequate numbers of specialist TB nurses for early detection and case-holding.

Please see related article: http://www.biomedcentral.com/1741-7015/9/127

Mycobacterium tuberculosis cluster with developing drug resistance, New York, New York, USA, 2003-2009

In 2004, identification of patients infected with the same Mycobacterium tuberculosis strain in New York, New York, USA, resulted in an outbreak investigation. The investigation involved data collection and analysis, establishing links between patients, and forming transmission hypotheses. Fifty-four geographically clustered cases were identified during 2003–2009. Initially, the M. tuberculosis strain was drug susceptible. However, in 2006, isoniazid resistance emerged, resulting in isoniazid-resistant M. tuberculosis among 17 (31%) patients. Compared with patients with drug-susceptible M. tuberculosis, a greater proportion of patients with isoniazid-resistant M. tuberculosis were US born and had a history of illegal drug use. No patients named one another as contacts. We used patient photographs to identify links between patients. Three links were associated with drug use among patients infected with isoniazid-resistant M.tuberculosis. The photographic method would have been more successful if used earlier in the investigation. Name-based contact investigation might not identify all contacts, particularly when illegal drug use is involved.

A geographically-restricted but prevalent Mycobacterium tuberculosis strain identified in the West Midlands Region of the UK between 1995 and 2008

Background

We describe the identification of, and risk factors for, the single most prevalent Mycobacterium tuberculosis strain in the West Midlands region of the UK.

Methodology/Principal Findings

Prospective 15-locus MIRU-VNTR genotyping of all M. tuberculosis isolates in the West Midlands between 2004 and 2008 was undertaken. Two retrospective epidemiological investigations were also undertaken using univariable and multivariable logistic regression analysis. The first study of all TB patients in the West Midlands between 2004 and 2008 identified a single prevalent strain in each of the study years (total 155/3,056 (5%) isolates). This prevalent MIRU-VNTR profile (32333 2432515314 434443183) remained clustered after typing with an additional 9-loci MIRU-VNTR and spoligotyping. The majority of these patients (122/155, 79%) resided in three major cities located within a 40 km radius. From the apparent geographical restriction, we have named this the “Mercian” strain. A multivariate analysis of all TB patients in the West Midlands identified that infection with a Mercian strain was significantly associated with being UK-born (OR = 9.03, 95%CI = 4.56–17.87, p<0.01), Black Caribbean (OR = 5.68, 95%CI = 2.96–10.91, p<0.01) resident in Wolverhampton (OR = 9.29, 95%CI = 5.69–15.19, p<0.01) and negatively associated with age >65 years old (OR = 0.25, 95%CI = 0.09–0.67, p<0.01). A second more detailed investigation analyzed a cohort of 82 patients resident in Wolverhampton between 2003 and 2006. A significant association with being born in the UK remained after a multivariate analysis (OR = 9.68, 95%CI = 2.00–46.78, p<0.01) and excess alcohol intake and cannabis use (OR = 6.26, 95%CI = 1.45–27.02, p = .01) were observed as social risk factors for infection.

Conclusions/Significance

The continued consistent presence of the Mercian strain suggests ongoing community transmission. Whilst significant associations have been found, there may be other common risk factors yet to be identified. Future investigations should focus on targeting the relevant risk groups and elucidating the biological factors that mediate continued transmission of this strain.

Genomic stability over 9 years of an isoniazid resistant Mycobacterium tuberculosis outbreak strain in Sweden

In molecular epidemiological studies of drug resistant Mycobacterium tuberculosis (TB) in Sweden a large outbreak of an isoniazid resistant strain was identified, involving 115 patients, mainly from the Horn of Africa. During the outbreak period, the genomic pattern of the outbreak strain has stayed virtually unchanged with regard to drug resistance, IS6110 restriction fragment length polymorphism and spoligotyping patterns. Here we present the complete genome sequence analyses of the index isolate and two isolates sampled nine years after the index case as well as experimental data on the virulence of this outbreak strain. Even though the strain has been present in the community for nine years and passaged between patients at least five times in-between the isolates, we only found four single nucleotide polymorphisms in one of the later isolates and a small (4 amino acids) deletion in the other compared to the index isolate. In contrast to many other evolutionarily successful outbreak lineages (e.g. the Beijing lineage) this outbreak strain appears to be genetically very stable yet evolutionarily successful in a low endemic country such as Sweden. These findings further illustrate that the rate of genomic variation in TB can be highly strain dependent, something that can have important implications for epidemiological studies as well as development of resistance.

Associations between Mycobacterium tuberculosis strains and phenotypes

This population-based study was used to investigate strong associations between phenotypes and genotypes.

To inform development of tuberculosis (TB) control strategies, we characterized a total of 2,261 Mycobacterium tuberculosis complex isolates by using multiple phenotypic and molecular markers, including polymorphisms in repetitive sequences (spoligotyping and variable-number tandem repeats [VNTRs]) and large sequence and single-nucleotide polymorphisms. The Beijing family was strongly associated with multidrug resistance (p = 0.0001), and VNTR allelic variants showed strong associations with spoligotyping families: >5 copies at exact tandem repeat (ETR) A, >2 at mycobacterial interspersed repetitive unit 24, and >3 at ETR-B associated with the East African–Indian and M. bovis strains. All M. tuberculosis isolates were differentiated into 4 major lineages, and a maximum parsimony tree was constructed suggesting a more complex phylogeny for M. africanum. These findings can be used as a model of pathogen global diversity.

A Mycobacterium tuberculosis cluster demonstrating the use of genotyping in urban tuberculosis control

Background

DNA fingerprinting of Mycobacterium tuberculosis isolates offers better opportunities to study links between tuberculosis (TB) cases and can highlight relevant issues in urban TB control in low-endemic countries.

Methods

A medium-sized molecular cluster of TB cases with identical DNA fingerprints was used for the development of a visual presentation of epidemiologic links between cases.

Results

Of 32 cases, 17 (53%) were linked to the index case, and 11 (34%) to a secondary case. The remaining four (13%) could not be linked and were classified as possibly caused by the index patient. Of the 21 cases related to the index case, TB developed within one year of the index diagnosis in 11 patients (52%), within one to two years in four patients (19%), and within two to five years in six patients (29%).

Conclusion

Cluster analysis underscored several issues for TB control in an urban setting, such as the recognition of the outbreak, the importance of reinfections, the impact of delayed diagnosis, the contribution of pub-related transmissions and its value for decision-making to extend contact investigations. Visualising cases in a cluster diagram was particularly useful in finding transmission locations and the similarities and links between patients.

Mycobacterium tuberculosis ecology in Venezuela: epidemiologic correlates of common spoligotypes and a large clonal cluster defined by MIRU-VNTR-24

BACKGROUND

Tuberculosis remains an endemic public health problem, but the ecology of the TB strains prevalent, and their transmission, can vary by country and by region. We sought to investigate the prevalence of Mycobacterium tuberculosis strains in different regions of Venezuela. A previous study identified the most prevalent strains in Venezuela but did not show geographical distribution nor identify clonal genotypes. To better understand local strain ecology, we used spoligotyping to analyze 1298 M. tuberculosis strains isolated in Venezuela from 1997 to 2006, predominantly from two large urban centers and two geographically distinct indigenous areas, and then studied a subgroup with MIRU-VNTR 24 loci.

RESULTS

The distribution of spoligotype families is similar to that previously reported for Venezuela and other South American countries: LAM 53%, T 10%, Haarlem 5%, S 1.9%, X 1.2%, Beijing 0.4%, and EAI 0.2%. The six most common shared types (SIT's 17, 93, 605, 42, 53, 20) accounted for 49% of the isolates and were the most common in almost all regions, but only a minority were clustered by MIRU-VNTR 24. One exception was the third most frequent overall, SIT 605, which is the most common spoligotype in the state of Carabobo but infrequent in other regions. MIRU-VNTR homogeneity suggests it is a clonal group of strains and was named the "Carabobo" genotype. Epidemiologic comparisons showed that patients with SIT 17 were younger and more likely to have had specimens positive for Acid Fast Bacilli on microscopy, and patients with SIT 53 were older and more commonly smear negative. Female TB patients tended to be younger than male patients. Patients from the high incidence, indigenous population in Delta Amacuro state were younger and had a nearly equal male:female distribution.

CONCLUSION

Six SIT's cause nearly half of the cases of tuberculosis in Venezuela and dominate in nearly all regions. Strains with SIT 17, the most common pattern overall may be more actively transmitted and SIT 53 strains may be less virulent and associated with reactivation of past infections in older patients. In contrast to other common spoligotypes, strains with SIT 605 form a clonal group centered in the state of Carabobo.

Penitentiary population of Mycobacterium tuberculosis in Kyrgyzstan: exceptionally high prevalence of the Beijing genotype and its Russia-specific subtype

Here, we present results of the first study of the Mycobacterium tuberculosis genotypes circulating in Kyrgyzstan. We focused on the incarcerated population known to be at high-risk for tuberculosis (TB) and with a significant impact on TB incidence in the general population. Beijing genotype was detected in 42 of 56 M. tuberculosis sputum-extracted DNA samples from newly-diagnosed adult pulmonary TB patients. RIF and INH resistance was genotypically detected in 28% and 55% samples; 13 of 15 MDR strains belonged to Beijing genotype. 12-locus MIRU-VNTR typing showed 8 of 56 samples to be mixed cases; 7 of them contained a Beijing strain. MIRU analysis demonstrated a high homogeneity of the studied collection (HGI=0.66) while 28 of 56 strains had a profile 223325153533 corresponding to Beijing/M2 subtype highly prevalent in different Russian settings. Three hypervariable loci, QUB-3232, VNTR-3820 and VNTR-4120, permitted to further subdivide 28 Beijing/M2 strains into 11 subtypes shared by 1 to 9 strains. To conclude, all markers taken together, the penitentiary population of M. tuberculosis in Kyrgyzstan exhibited a strong genetic affinity to Russia and a weak relatedness to East Asia.

High rate of transmission among contacts in large London outbreak of isoniazid mono-resistant tuberculosis

BACKGROUND

For a continuing London outbreak of isoniazid mono-resistant tuberculosis (TB), we aimed to determine transmission rates and risk factors for contacts of early cases, in order to inform future guidance on contact tracing.

METHODS

Paper-based proformas were completed by TB nurses, and then analysed using EpiInfo/SAS statistical software.

RESULTS

Forty community contacts (11%) became cases, 45 (13%) were recommended chemoprophylaxis and 270 (76%) were discharged clear of infection. The highest transmission rate was among contacts exposed to two or more cases (29% became cases) and close contacts of sputum smear-positive cases (22%). Other risk factors were being male and exposure to drug-using cases or cases with prison links. The number needed to be screened (NNS) to detect one case was lowest [5 (95% CI: 4-8)] for contacts of sputum smear-positive pulmonary cases, although the NNS was still only 20 (95% CI:8-72) for casual contacts of smear-positive cases.

CONCLUSIONS

Transmission of disease to contacts was high (11%) compared with other documented outbreaks (0.7-2%). The results support recommended guidelines for contact tracing but also provide grounds to recommend, for outbreak cases, screening of casual contacts of smear-positive cases and contacts exposed to more than one case, drug users or prisoners.

Investigating tuberculosis trends in England

OBJECTIVE

To investigate the factors associated with the increasing incidence of tuberculosis in England.

DESIGN

Prospective national surveillance study.

METHODS

Measurement of relative trends in demographic, clinical and microbiological characteristics of tuberculosis cases reported in England between 1999 and 2003.

RESULTS

Between 1999 and 2003, the number of tuberculosis cases reported in England increased by 19% from 5539 to 6608. Significant increases in tuberculosis cases were seen in the non-UK-born population who were recent entrants to the UK (arrival less than 5 years prior to diagnosis) relative to cases in the UK-born population, both in London [1.08; 95% confidence interval (CI) 1.02-1.14] and outside London (1.22; 95% CI 1.16-1.28). Cases of tuberculosis co-infected with human immunodeficiency virus (HIV) increased significantly both in London (1.19; 95% CI 1.12-1.27) and outside London (1.22; 95% CI 1.12-1.33) relative to cases not known to be co-infected with HIV. Small increases in the number of cases living in less-deprived areas were observed relative to those in the most-deprived areas (1.11; 95% CI 1.02-1.21) in London. The number of cases of isoniazid-resistant (1.09; 95% CI 1.02-1.16) and multi-drug-resistant tuberculosis (1.22; 95% CI 1.02-1.45) increased relative to drug-susceptible cases in London.

CONCLUSIONS

Tuberculosis remains strongly associated with deprivation, but no real change in the distribution of tuberculosis cases by deprivation was observed over the study period. The proportion of tuberculosis cases co-infected with HIV has increased, but migration explains most of the recent trends in tuberculosis in England. Measures that target latent tuberculosis infection could have an increased role to play alongside measures against active disease in reducing the incidence of tuberculosis in the UK.

Increasing antituberculosis drug resistance in the United Kingdom: analysis of National Surveillance Data

OBJECTIVE

To identify recent trends in, and factors associated with, resistance to antituberculosis drugs in England, Wales, and Northern Ireland.

DESIGN

Cohort of tuberculosis cases reported to the enhanced tuberculosis surveillance system matched to data on drug susceptibility and national strain typing data.

SETTING

England, Wales, and Northern Ireland 1998-2005.

MAIN OUTCOME MEASURES

Unadjusted and adjusted odds ratios for drug resistance and associated factors. Proportion of multidrug resistant tuberculosis cases clustered.

RESULTS

28 620 culture confirmed cases were available for analysis. The proportion of cases resistant to isoniazid increased from 5% to 7%. Rifampicin resistance increased from 1.0% to 1.2% and multidrug resistance from 0.8% to 0.9%. Ethambutol and pyrazinamide resistance remained stable at around 0.4% and 0.6%, respectively. Regression analyses showed a significant increase in isoniazid resistance outside London (odds ratio 1.04, 95% confidence interval 1.01 to 1.07, a year, associated with changes in age (0.98, 0.98 to 0.99, a year), place of birth (1.49, 1.16 to 1.92), and ethnicity (P<0.05). In London, the rise (1.05, 1.02 to 1.08, a year) was related mainly to an ongoing outbreak. Increases in rifampicin resistance (1.06, 1.01 to 1.11, a year) and multidrug resistance (1.06, 1.00 to 1.12, a year) were small. A fifth of patients with multidrug resistant tuberculosis in 2004-5 had indistinguishable strain types, and one case was identified as extensively drug resistant.

CONCLUSIONS

The rise in isoniazid resistance reflects increasing numbers of patients from sub-Saharan Africa and the Indian subcontinent, who might have acquired resistance abroad, and inadequate control of transmission in London. The observed increases highlight the need for early case detection, rapid testing of susceptibility to drugs, and improved treatment completion.

Knowledge of tuberculosis transmission among recently infected patients in Glasgow

OBJECTIVES

To examine perceptions and understanding of disease causation in tuberculosis patients with few epidemiological links detected by contact tracing.

STUDY DESIGN

An exploratory qualitative study using semi-structured interviews was undertaken. Patients' beliefs were explored against a background of medical thinking about tuberculosis transmission and the current approach to contact tracing.

METHODS

Interviews were undertaken with patients (n=23) or suitable next of kin (n=3). Study patients were diagnosed with tuberculosis in Glasgow, an urban area of Scotland, between 1997 and 2004. All had a genetically indistinguishable 15-banded IS6110 restriction fragment length polymorphism pattern of the Beijing family of Mycobacterium tuberculosis, suggestive of recently transmitted infection, yet few had epidemiological links detectable as a result of contact tracing (30.8%).

RESULTS

Interviewees had varying levels of knowledge, but most believed that tuberculosis was caused by a pathogen, spread by person-to-person contact. Modes of transmission were thought to include airborne transmission, sharing utensils with an infected individual, consumption of contaminated foods/liquids, and exchange of bodily fluids. Prolonged contact was not thought to be required for transmission to occur. Impaired immunity, social factors and environmental factors were believed to enhance the potential for transmission.

CONCLUSIONS

Patients have complex beliefs about tuberculosis transmission and causation, which do not always mirror those of health professionals. Adopting and implementing an approach to contact identification that is aligned with lay beliefs may result in improved contact tracing outcomes.

Impact of Mobile Radiographic Screening on Tuberculosis among Drug Users and Homeless Persons

RATIONALE

In 2002, a mobile radiographic screening program was started in Rotterdam to respond to high rates of tuberculosis (TB) among illicit drug users and homeless persons.

OBJECTIVES

We studied trends and characteristics of TB among these risk groups and assessed the impact of the screening program on transmission, using molecular typing.

METHODS

Description of trends, and of demographic and disease-related characteristics of tuberculosis cases among these risk groups between 1993 and 2005. TB was considered to result from recent transmission if the mycobacterial DNA fingerprints of cases were identical to those of other cases in the risk groups in the previous 2 years.

MEASUREMENTS AND MAIN RESULTS

During the study period, 206 individuals with TB among illicit drug users and homeless persons were notified, representing 11.4% of the total case load of 1,811 in Rotterdam. The annual number of tuberculosis cases declined from 24 at the start of the screening program to 11 cases in 2005. The screening program identified 28 cases (a prevalence rate of 327 per 100,000 radiographs), of which 12 were smear positive. In 1997-2002, more than 80% of the illicit drug users or homeless persons with TB were infected with one of the Mycobacterium tuberculosis strains prevalent among these risk groups. After nearly 4 years of systematic radiographic screening this proportion declined to 45% in 2005.

CONCLUSIONS

DNA fingerprinting can be a useful tool to evaluate the impact of a TB screening program. We advocate that screening of illicit drug users and homeless persons should be continued to prevent a resurgence of TB.

The impact of social factors on tuberculosis management

AIM

This paper is a report of a study to examine the impact of social factors on the management of tuberculosis including engagement with services, hospitalization and extended treatment.

BACKGROUND

Rates of tuberculosis in major European cities have increased greatly in the last 10 years. The changing epidemiology of the disease, concentrated in marginalized groups, presents new challenges to the control of tuberculosis.

METHODS

A prospective cohort study of 250 newly diagnosed tuberculosis patients was conducted in London between January 2003 and January 2005. Data were collected by means of a risk assessment tool and from medical records. Outcome measures included missed appointments, frequency and duration of hospitalization and length of treatment.

RESULTS

The median age of the study sample was 33.82 (range 16.4-92.5) and 56.8% were male. Thirty-two per cent were hostel/street homeless or temporarily sharing accommodation with friends or relatives. Thirty-nine per cent were in receipt of welfare benefits and 13.2% had no income. Over a third anticipated difficulties taking their medicines and 30.3% had noone to remind them of this. Increased hospitalization was associated with hostel/street homelessness, drug or alcohol use and having noone to remind them to take their medicines (all P <or= 0.01). Missed appointments were associated with drug/alcohol use and previous tuberculosis treatment. Extended treatment was also associated with drug/alcohol use; previous tuberculosis treatment, drug resistance and those anticipating difficulties taking medication (all P <or= 0.001).

CONCLUSIONS

The development of a social outreach model of care with an emphasis on prevention and support is an essential aspect of modern, international tuberculosis care.

Ileoscopy in patients with ileocolonic tuberculosis

AIM: To study the role of retrograde terminal ileoscopy in patients suspected to have ileocolonic tuberculosis.

METHODS: A retrospective analysis was performed for patients undergoing colonoscopy for suspected ileocolonic tuberculosis between January 2000 and June 2004, in whom retrograde ileoscopy had been performed. Only patients diagnosed with tuberculosis on the basis of histological findings of either a caseating granuloma or those having non-caseating granuloma or a collection of epithelioid cells at a minimum of one endoscopic lesion (either in the colon or the terminal ileum) on histology with good responses to conventional anti-tuberculous drugs were enrolled for the study.

RESULTS: Fifty-three patients were included. The terminal ileum was involved in only 11 patients. Eight of these patients had involvement of the cecum too. Two patients had ileal lesions without cecal involvement; however, lesions were noted in the ascending colon. In one patient the whole colon was normal and only the terminal ileum showed nodularity and ulceration. Histological examination of the ileal biopsies obtained from the ileal lesions showed noncaseating granulomas in five, collection of epithelioid cells in four and nonspecific histology in two patients. Mucosal biopsies obtained from the lesion in the terminal ileum, in the patient in whom mucosal abnormality was observed to be confined to the ileum, showed noncaseating granulomas. In two other patients the ileal biopsies alone showed histological evidence of tuberculosis with biopsies from the colonic lesions showing non-specific inflammatory changes only.

CONCLUSION: Retrograde ileoscopy should be performed in all patients undergoing colonoscopy for suspected ileocolonic tuberculosis. In some patients only the terminal ileum may be involved and histological examination may reveal evidence of tuberculosis only from the lesions in the terminal ileum. This approach would lead to additional lesions being picked up and increasing the chances of well-timed diagnosis of tuberculosis.

Tuberculosis in London: the importance of homelessness, problem drug use and prison

BACKGROUND

The control of tuberculosis (TB) is founded on early case detection and complete treatment of disease. In the UK, TB is concentrated in subgroups of the population in large urban centres. The impact of homelessness, imprisonment and problem drug use on TB control in London is reviewed.

METHODS

A cohort study was undertaken of all patients with TB in Greater London to determine the point prevalence of disease in different groups and to examine risk factors for smear positivity, drug resistance, treatment adherence, loss to follow-up and use of directly observed therapy (DOT).

RESULTS

Data were collected on 97% (1941/1995) of eligible patients. The overall prevalence of TB was 27 per 100,000. An extremely high prevalence of TB was seen in homeless people (788/100,000), problem drug users (354/100,000) and prisoners (208/100,000). Multivariate analysis showed that problem drug use was associated with smear positive disease (OR 2.2, p<0.001), being part of a known outbreak of drug resistant TB (OR 3.5, p = 0.001) and loss to follow-up (OR 2.7, p<0.001). Imprisonment was associated with being part of the outbreak (OR 10.3, p<0.001) and poor adherence (OR 3.9, p<0.001). Homelessness was associated with infectious TB (OR 1.6, p = 0.05), multidrug resistance (OR 2.1, p = 0.03), poor adherence (OR 2.5, p<0.001) and loss to follow-up (OR 3.8, p<0.001). In London, homeless people, prisoners and problem drug users collectively comprise 17% of TB cases, 44% of smear positive drug resistant cases, 38% of poorly compliant cases and 44% of cases lost to follow-up. 15% of these patients start treatment on DOT but 46% end up on DOT.

CONCLUSIONS

High levels of infectious and drug resistant disease, poor adherence and loss to follow-up care indicate that TB is not effectively controlled among homeless people, prisoners and problem drug users in London.

Tuberculosis in London: a decade and a half of no decline [corrected]

BACKGROUND

London accounts for nearly half of the national burden of tuberculosis. The incidence of tuberculosis has more than doubled in London in the past 15 years.

METHODS

Data from the enhanced tuberculosis surveillance 1999-2003, the national tuberculosis surveys of 1993 and 1998, and tuberculosis notifications were compared and analysed.

RESULTS

In 2003, 3048 patients with tuberculosis were reported in London, 45% of the national total. This represents an incidence of 41.3/100,000, five times higher than the rest of England and Wales, and in parts of London the incidence of tuberculosis is nine times the national average. 75% of people with tuberculosis in London are born abroad; nearly half have lived in the UK for <5 years, but a third for >10 years. 86% are from an ethnic minority group, and the incidence is highest in black Africans at 283/100,000 compared with 141, 141 and 8/100,000 for Pakistanis, Indians and whites, respectively. In absolute terms, a third of patients with tuberculosis in London are from Africa and nearly a third from the Indian subcontinent. Specific groups affected also include the homeless, prisoners, and hard drug and alcohol users as well as the immunosuppressed.

CONCLUSIONS

London reflects the worldwide rise in tuberculosis, with increasing incidence in ethnic minorities. Work has been carried out to combat this rise, but more is needed. Tuberculosis control and prevention strategies should be mindful of the changing epidemiology of tuberculosis in London, and provide information, diagnosis and treatment tailored to the specific needs of the capital and its at-risk groups.

Ileoscopy in 39 hematochezia patients with normal colonoscopy

AIM: To assess the role of retrograde terminal ileoscopy in hematochezia patients with normal colonoscopy.

METHODS: Between January 1997 and March 2005, 39 hematochezia patients (males 36, females 3, mean age 44.7 years) with a reported normal colonoscopy underwent a repeat colonoscopy. After reaching the cecum, attempt was made to localize the ileocecal valve and intubate the terminal ileum. Any abnormality in the mucosa of the terminal ileum was carefully recorded and biopsies were obtained from suspicious-looking lesions.

RESULTS: During the study period there were 39 patients admitted for hematochezia in whom colonoscopy till cecum did not reveal any abnormality. Full-length colonoscopy till the cecum could be performed in all the patients. The terminal ileum could be intubated in 36 patients. No abnormality was noted in 31 patients. Ileal ulcers were noted in two patients. Nodularity along with ulceration of the ileal mucosa, a Dieulafoy’s lesion, and an angiomatous malformation were noted in one patient each. Histological examination of the biopsies obtained from the ulcers revealed typical tuberculous lesion in the patient with nodularity and ulceration. One of the patients had typhoid ulcers and another had non-specific ulcers.

CONCLUSION: Retrograde terminal ileoscopy gives limited but valuable information, in patients with hematochezia and should be attempted in all such patients.

Rifampicin resistance in tuberculosis outbreak, London, England

Mycobacterium tuberculosis isolates cultured from 6 patients associated with an isoniazid-resistant M. tuberculosis outbreak acquired rifampicin resistance. The rpoB gene sequence showed that resistance was associated with rare mutations in each isolate. Three isolates had a mutation outside the rifampicin resistance–determining region.

Impact of statewide program to promote appropriate antimicrobial drug use

The Wisconsin Antibiotic Resistance Network (WARN) was launched in 1999 to educate physicians and the public about judicious antimicrobial drug use. Public education included radio and television advertisements, posters, pamphlets, and presentations at childcare centers. Physician education included mailings, susceptibility reports, practice guidelines, satellite conferences, and presentations. We analyzed antimicrobial prescribing data for primary care physicians in Wisconsin and Minnesota (control state). Antimicrobial prescribing declined 19.8% in Minnesota and 20.4% in Wisconsin from 1998 to 2003. Prescribing by internists declined significantly more in Wisconsin than Minnesota, but the opposite was true for pediatricians. We conclude that the secular trend of declining antimicrobial drug use continued through 2003, but a large-scale educational program did not generate greater reductions in Wisconsin despite improved knowledge. State and local organizations should consider a balanced approach that includes limited statewide educational activities with increasing emphasis on local, provider-level interventions and policy development to promote careful antimicrobial drug use.

Tuberculosis in contacts need not indicate disease transmission

BACKGROUND

Traditional contact investigation is an important tool for controlling tuberculosis. It may also help to indicate drug susceptibility patterns when Mycobacterium tuberculosis cultures are not available. Such investigations often underestimate the degree of transmission found by genotyping, but overestimation may also occur. This report is the result of a routine successive DNA restriction fragment length polymorphism (RFLP) analysis of M tuberculosis isolated in Norway.

METHOD

Fifteen immigrants belonging to the same community were notified with tuberculosis during February to September 2003. The mycobacterial isolates were analysed by RFLP.

RESULTS

All 15 patients had social contact with each other and 13 belonged to the same church community. A total of 14 cultures were positive for M tuberculosis. Among these isolates, six different genotypes were found. Five patients had not acquired the infection from the putative source.

CONCLUSIONS

Reactivation of tuberculosis may occur in contacts during the development of an outbreak. In such situations, traditional contact investigations may overestimate the rate of transmission found by genotyping of M tuberculosis. When cultures are unavailable and presumed drug susceptibility patterns are based on that of contacts, such overestimation may lead to incorrect treatment of a patient. Contact investigations must be combined with genotyping of M tuberculosis to conclude how tuberculosis is transmitted. This is especially important in persons with several risk factors for infection.