Tuberculosis Exposure Research Articles

Tuberculosis of the parotid lymph nodes: clinical and imaging features.

ObjectivesTo characterize clinical, computed tomography (CT) and magnetic resonance imaging (MRI) features of tuberculosis (TB) of the parotid nodes.Materials and methodsCT (n=21) and MR (n=7) images, and clinical data from 25 patients with TB of the parotid nodes were retrospectively analyzed by two experienced radiologists who reached consensus.ResultsYounger patients (aged <50 years) accounted for 72%. Eighty percent of patients were asymptomatic, and had no history of TB exposure. According to clinical and imaging findings, 64% and 60% patients were misdiagnosed as having tumors, respectively. A total of 43 lesions were identified. Thirty-eight (88.4%) lesions involved the superficial lobe. Fourteen (56%) cases had multiple lesions. There were four types of changes in the parotid fascia: local thickening (40%, n=10); local rupture with thickened adjacent skin (28%, n=7); focal bulge (20%, n=5); and no changes (12%, n=3). Cervical lymphadenopathy was seen in 14 out of 25 cases (56%). The lesions were contrast-enhanced in four patterns on CT images: homogeneous enhancement (37.1%, n=13), irregular cyst-like enhancement (37.1%, n=13), thick-walled ring enhancement (14.2%, n=5), and garland-like enhancement (11.4%, n=4). On MRI, the signal intensity of lesions was isointense on T1-weighted image, hyperintense on T2-weighted image, markedly hyperintense on diffusion-weighted imaging, and low on the apparent diffusion coefficient map. The surrounding parotid parenchymal edema was identified clearly on coronal MR images.ConclusionTB of the parotid nodes tend to simulate tumors clinically and radiologically. Their preferential sites are the superficial lobe. In young patients with positive purified protein derivative skin test and lesions accompanied by cervical lymphadenopathy, changes in the parotid fascia and parotid parenchymal edema adjacent to the lesions on CT and MRI may be helpful in the diagnosis and to facilitate differential diagnosis.

Genetic Resistance to Mycobacterium tuberculosis Infection and Disease.

Natural history studies of tuberculosis (TB) have revealed a spectrum of clinical outcomes after exposure to Mycobacterium tuberculosis, the cause of TB. Not all individuals exposed to the bacterium will become diseased and depending on the infection pressure, many will remain infection-free. Intriguingly, complete resistance to infection is observed in some individuals (termed resisters) after intense, continuing M. tuberculosis exposure. After successful infection, the majority of individuals will develop latent TB infection (LTBI). This infection state is currently (and perhaps imperfectly) defined by the presence of a positive tuberculin skin test (TST) and/or interferon gamma release assay (IGRA), but no detectable clinical disease symptoms. The majority of healthy individuals with LTBI are resistant to clinical TB, indicating that infection is remarkably well-contained in these non-progressors. The remaining 5–15% of LTBI positive individuals will progress to active TB. Epidemiological investigations have indicated that the host genetic component contributes to these infection and disease phenotypes, influencing both susceptibility and resistance. Elucidating these genetic correlates is therefore a priority as it may translate to new interventions to prevent, diagnose or treat TB. The most successful approaches in resistance/susceptibility investigation have focused on specific infection and disease phenotypes and the resister phenotype may hold the key to the discovery of actionable genetic variants in TB infection and disease. This review will not only discuss lessons from epidemiological studies, but will also focus on the contribution of epidemiology and functional genetics to human genetic resistance to M. tuberculosis infection and disease.

Adolescent tuberculosis associated with tuberculosis exposure in classrooms and dorm rooms in Guangxi, China

ObjectiveQuantify tuberculosis (TB) risk attributable to dorm room exposure in addition to classroom exposure. MethodsAdolescent school contact investigations were conducted for every reported index TB case, and similar contact investigations were conducted in selected community-control classes from November 2016 to October 2017 in Guangxi, China. ResultsA total of 6263 contacts of 112 index TB cases and 6130 classmates of 112 controls were investigated. There were 14, 12, and 2 new active TB cases detected among classmates/non-roommates of index cases, classmates/roommates of index cases, and control classmates, respectively. Compared with control contacts, the adjusted relative risk (95% confidence interval (CI)) and population attributable fraction (PAF) for being a classmate/non-roommate of the index case increased the risk of active TB diagnosis to 8.44 (95% CI: 1.31–54.48) and 44.1%. The adjusted RR and PAF for being a classmate/roommate of the index case was 29.37 (95% CI: 3.80, 227.11) and 41.4%. Being classmates/roommates significantly increased the risk of TB compared to a classmate/non-roommate of the index case (RR=3.48, 95% CI: 1.64, 7.40). ConclusionThe additional risk of TB due to exposure in the dorm room should be taken into account in planning of TB prevention and control in boarding schools.

Risk of serious infection in healthcare workers with inflammatory bowel disease: a case-control study of the Groupe d'Etude Thérapeutique des Affections Inflammatoires du tube Digestif (GETAID).

Whether healthcare workers with inflammatory bowel disease (IBD) are at increased risk of severe infection due to daily pathogen exposure is controversial. To assess the risk of severe infection in healthcare workers with IBD in a large multicentre case-control study. The study population comprised 482 healthcare workers with IBD from 17 centres who were matched for gender, age, disease subtype and year of diagnosis to 482 controls (non-healthcare workers with IBD). The study period was between the date of diagnosis of IBD and June 2016. Severe infection was defined as any community-acquired infection that required hospitalisation. With a median follow-up of 9.3 years, 139 severe infections were recorded among cases and controls, including 30 Clostridium difficile infections, 33 severe viral infections, nine tuberculosis infections, 21 community-acquired pneumonia and 46 others. No difference was observed between healthcare workers and controls regarding the overall incidence rates of severe infection. An increased risk of tuberculosis was noted in healthcare workers. In multivariate analysis in the entire study population, severe infection was associated with current exposure to corticosteroids (OR = 3.05, 95% CI [2.06-4.52], P < 0.001), immunosuppressants (OR = 1.98, 95% CI [1.38-2.84], P < 0.001) and anti-TNF agents (OR = 2.93, 95% CI [2.02-4.27], P < 0.001) and reduced with Crohn's disease (OR = 0.63, 95% CI [0.43-0.91], P = 0.01). Healthcare workers with IBD do not have an increased risk of severe infection compared with other patients with IBD, except for tuberculosis. Screening for tuberculosis exposure should be assessed in this high-risk population when treated with anti-TNF agents.

Diagnosis and Management of Childhood tuberculosis in Public health Clinics in a rural Area in the Philippines: results from a Community surveillance

Background. Childhood tuberculosis (TB) remains a significant health problem worldwide despite the increase on its emphasis in national health programs.&#x0D; Objective. This study aimed to describe how TB in children is identified and managed in a routine TB program in a rural setting in a high-burden country.&#x0D; Methods. This is a prospective, community-based surveillance study in public rural clinics in the Philippines. Observations on case finding and management of TB in children as well as contact tracing in an existing TB program are described.&#x0D; Results. Out of 266 children with presumptive TB, 41 (15.4%) were cases of TB, 15 (5.6%) had latent TB infection (LTBI), 81 (30.5%) had TB exposure, and 129 (48.5%) had no TB. There were 37 (90%) TB cases who were clinically diagnosed. Ninety-three per cent (93%) of children with TB disease were cured or completed treatment. Among 25 children targeted for isoniazid preventive therapy (IPT) for LTBI and TB exposure, only 12 (52%) completed the recommended 6 months of IPT. Only 40 (43%) children aged 0 to 4 years exposed to smear-positive TB cases were screened.&#x0D; Conclusion. Barriers in the diagnosis, low IPT completion and problems in contact tracing may hinder successful implementation of TB programs for children.

Tuberculosis prevention knowledge, attitudes, and practices of primary health care nurses.

Tuberculosis (TB) continues to challenge global health systems, especially in South Africa. Nurses are especially vulnerable to TB exposure, because of their prolonged front-line contact with infected patients-especially in primary health care (PHC) clinics. Their infection control practices, influenced by key factors such as knowledge and attitudes towards TB prevention, become an important consideration. The aim of the study was to (1) describe the TB prevention knowledge, attitudes, and practices of PHC nurses in a South African district and (2) explore moderating factors on TB prevention practices. A cross-sectional survey was undertaken at all 41 PHC facilities in Mangaung Metropolitan district, Free State province, South Africa, using self-administered questionnaires. Captured data were analysed to yield descriptive and multivariate statistics. Results suggest several instances of inadequate TB prevention knowledge, attitudes, and practices. Good TB practice was predicted by TB attitudes and knowledge, and the relationship between TB prevention knowledge and practices was not moderated by training, attitudes, or nurse category. Results echo previous indications that nurses often do not exhibit the desired knowledge, attitudes, and practices required to adequately protect themselves and others against TB and suggest further exploration towards understanding the influences on TB prevention practice among nurses.

Screening for Latent Tuberculosis Infection Among HIV-Infected Medicaid Enrollees.

In the United States, universal screening for latent tuberculosis (TB) infection among people with HIV is recommended, but the percentage receiving screening is unknown. This study assessed screening for latent TB infection among people with HIV enrolled in Medicaid during 2006-2010. We used nationwide fee-for-service Medicaid records to identify people with HIV, measure screening for latent TB infection, and examine associated demographic, social, and clinical factors. We used logistic regression analysis to calculate odds ratios (ORs) and 95% confidence intervals (CIs). We created 2 multivariate models to prevent collinearity between variables for length of HIV infection. Of 152 831 people with HIV, 26 239 (17.2%) were screened for latent TB infection. The factor most strongly associated with screening was TB exposure or suspected TB (OR = 3.78; 95% CI, 3.27-4.37). Significant demographic characteristics associated with screening included being African American (OR = 1.28; 95% CI, 1.24-1.32) or ≤20 years of age (OR = 1.35; 95% CI, 1.28-1.42). Significant clinical and social factors associated with screening included poor housing conditions, low body mass index, chemotherapy treatment, and use of certain substances (ORs ranged from 1.24 [95% CI, 1.20-1.27] to 1.47 [95% CI, 1.22-1.76]). The screening rate for latent TB infection was higher among people with newly diagnosed HIV infection than among those with established infection (OR = 1.37; 95% CI, 1.32-1.41) and among people with a longer established HIV infection than among those with shorter HIV infection (OR = 1.24; 95% CI, 1.23-1.26 for each additional year). Screening for latent TB infection among fee-for-service Medicaid beneficiaries with HIV was suboptimal, despite the presence of demographic, social, or clinical characteristics that should have increased the likelihood of screening. The lack of certain data in Medicaid may have resulted in an underestimation of screening.

Missed opportunities for tuberculosis prevention among patients accessing a UK HIV service.

United Kingdom guidelines recommend screening for and treatment of latent tuberculosis infection (LTBI) in HIV-positive patients at high risk of active tuberculosis (TB) disease, but implementation is suboptimal. We investigated potential missed opportunities to identify and treat LTBI among HIV-positive patients accessing a large HIV outpatient service in London. Case records of all adult patients attending our service for HIV care diagnosed with active TB between 2011 and 2015 were reviewed to determine whether they met criteria for LTBI screening and whether screening was undertaken. Twenty-five patients were treated for TB. Of 15 (60%) patients who started TB treatment ≥6 months after HIV diagnosis, 14 (93%) met UK guideline-recommended criteria for LTBI screening and treatment; only one (7%) had been screened for LTBI. Eight of these 15 (53%) patients had additional risk factors for TB which are not reflected in current UK guidelines. Of 15 patients treated for TB ≥6 months after diagnosis of HIV, 14 (93%) had not been screened for LTBI, suggesting missed opportunities for TB prevention. People living with HIV may benefit from a broader approach to LTBI screening which takes into account additional recognised TB risk factors and ongoing TB exposure.

Cross-sectional study associating secondhand smoke exposure and development of tuberculosis in children (Effect of a Smoking Cessation Intervention Program for Families on the Clinical Outcome of Children Diagnosed with TB)

Cross-sectional study associating secondhand smoke exposure and development of tuberculosis in children (Effect of a Smoking Cessation Intervention Program for Families on the Clinical Outcome of Children Diagnosed with TB)

Pediatric tuberculosis consultations across 5 CDC regional tuberculosis training and medical consultation Centers

BackgroundThe U.S. Centers for Disease Control and Prevention (CDC) funds five Regional Tuberculosis Training and Medical Consultation Centers (RTMCCs) that provide training and consultation for tuberculosis (TB) control and management. RTMCC utilization for assistance with diagnosis and management of TB in children has not been described. We analyzed pediatric TB consultations performed across all RTMCCs in terms of question type, provider type, and setting. MethodsThe CDC medical consultation database was queried for consultations regarding patients ≤ 18 years provided between 1/1/13–4/22/15 by all RTMCCs (Curry International TB Center, Heartland National TB Center, Mayo Clinic Center for TB, New Jersey Medical School Global TB Institute, Southeastern National TB Center). Each query was categorized into multiple subject areas based on provider type, setting, consultation topic, and patient age. ResultsThe 5 RTMCCs received 1164 pediatric consultation requests, representing approximately 20% of all consultations performed by the centers during the study period. Providers requesting consults were primarily physicians (46.3%) or nurses (45.0%). The majority of pediatric consult requests were from state and local public health departments (679, 58.3%) followed by hospital providers (199, 17.1%); fewer requests came from clinicians in private practice (84, 7.2%) or academic institutions (40, 3.4%). Consults addressed 14 different topics, most commonly management of children with TB disease (19.1%), latent TB infection (LTBI) (18.2%), diagnosis or laboratory testing (18.7%), and pharmacology (9.2%). DiscussionPediatric consultations accounted for approximately 20% of all consultations performed by RTMCCs during the study period. RTMCCs were utilized primarily by public health departments regarding management of TB disease, LTBI, and diagnosis or laboratory testing. The relative underutilization of the RTMCCs by clinicians in non-public health settings, who often manage children with TB exposure or infection, warrants further study. As US TB case rates decline and providers become less experienced with childhood TB, medical consultation support may become increasingly important.

Lymphnode tuberculosis in a 4-year-old boy with relapsed ganglioneuroblastoma: a case report

BackgroundMycobacterium tuberculosis (M. tuberculosis) disease is a generally well-known problem among immunocompromised adults and children. In pediatric oncology, only few cases of M. tuberculosis disease are reported so far.Case presentationWe report a case of concomitant lymphnode tuberculosis in a 4-year-old German boy with relapsed ganglioneuroblastoma. 18 months after the initial diagnosis, relapse with new paravertebral lesions and new lesions in the left lower lobe of the lung and in the perihilar lymphnodes suspicious of metastases of the ganglioneuroblastoma were detected. While relapse in the tumor was confirmed, unexpectedly, pathologic examination revealed morphological diagnosis of lymphnode tuberculosis. The boy was of German background without previous history of tuberculosis exposure. Both, antituberculostatic and relapse treatment were immediately initiated. Three months on, MRI revealed regressive findings in the lung and lymphnodes and partial response in the tumor. The patient underwent second MiBG therapy and haploidentical stem cell transplantation.ConclusionThe diagnosis of lymphnode tuberculosis in a 4-year-old German boy with relapsed ganglioneuroblastoma was only made by chance, but most likely saved his life. Pediatric oncologist should be aware of tuberculosis as the incidence might increase over time and the timely diagnosis of a potentially preventable M. tuberculosis disease is irreplaceable. Further studies are needed to explore the incidence of M. tuberculosis infections and the value of IGRA, testing for latent tuberculosis infection prior to chemotherapy in children with underlying malignancies.

Polymorphisms in Toll-Like Receptor 10 and Tuberculosis Susceptibility: Evidence from Three Independent Series

The toll-like receptor 2 (TLR2)-mediated immune response is critical for host defense against Mycobacterium tuberculosis. There is evidence that TLR10, a TLR2 signaling modulator, may be involved in progression of tuberculosis (TB). Using a self-validating case-control design, we tested for an association between seven TLR10 polymorphisms and susceptibility to TB in three independent series with two distinct populations. Single-nucleotide polymorphism (SNP) genotypes were determined by the SNPscanTM method. Three genetic models (additive, dominant, and recessive) as well as multiple-SNP score analyses were used to evaluate the risk of TB associated with the TLR10 SNPs. By comparing TB patients with healthy controls, we observed two SNPs (rs11466617 and rs4129009) that were associated with decreased risk of TB in the Tibetan population, but did not in the Chinese Han population. Further analysis demonstrated that the rs11466617 Chengdu cohort genotype served as a protective factor against the progression of latent TB infection (LTBI) to active TB under the recessive model. None of the SNPs were significantly different in comparisons of TB-uninfected people with LTBI individuals. Additionally, when the underlying four TB-associated loci were considered together in a multiple-SNP score analysis, we observed an allele dose-dependent decrease in TB risk in Tibetans. Variants of TLR10 may show an ethnic specificity on susceptibility to TB in Tibetan individuals. rs11466617 affected the susceptibility to progress from LTBI to active TB disease, but was not associated with the establishment of LTBI after M. tuberculosis exposure. More studies are needed to verify this genetic epidemiological result and unravel the role of TLR10 SNPs in the pathogenesis of TB.

Low Indeterminate Rates Associated With Use of the QuantiFERON-TB Gold In-Tube Test in Children With Inflammatory Bowel Disease on Long-term Infliximab.

Tumor necrosis factor alpha (TNF-α) inhibitors are linked with increased risk of reactivation of active tuberculosis. The QuantiFERON-TB Gold In-Tube test is approved for screening latent tuberculosis infection in children and adults. There are limited data on the test performance in children on long-term treatment with TNF-α inhibitors. The objective of this study was to assess the proportion of indeterminate results for the QuantiFERON-TB Gold In-Tube in children with inflammatory bowel disease (IBD) on long-term infliximab treatment and to evaluate the range of interferon-γ responses to mitogen. A single-center prospective study of children 5 to 19 years of age with IBD on long-term infliximab treatment (>3 months). Each child was assessed for tuberculosis exposure risk and had blood drawn for the QuantiFERON-TB Gold In-Tube. Data on the range of interferon-γ responses and final QuantiFERON-TB Gold In-Tube test results were collected. Ninety-three children were included, with a median age of 16 years. The median total duration of infliximab therapy was 34 months (range, 3-119 months). The QuantiFERON-TB Gold In-Tube was indeterminate in 1 patient (1.1%), positive in 2 patients, and negative in 90 patients. The maximum interferon-γ response to mitogen (10 IU/mL) was observed in 82 patients (88%), with only 1 patient having an inadequate response. The proportion of indeterminate results was significantly lower than the prospectively hypothesized rate of 8%, based on prior studies in nonimmunosuppressed patients (P = 0.004). Pediatric patients with IBD on long-term treatment with infliximab had an adequate interferon-γ response to mitogen and a low indeterminate rate when assessed with the QuantiFERON-TB Gold In-Tube test. This study demonstrates a robust interferon gamma response to phytohemagglutinin stimulation in a pediatric population on long-term therapy with infliximab. The QuantiFERON-TB Gold In-Tube test may therefore be useful as a periodic screening tactic for latent TB in children on long-term infliximab therapy.

Tuberculosis Recommendations for Solid Organ Transplant Recipients and Donors.

Tuberculosis Recommendations for Solid Organ Transplant Recipients and Donors.

Prevalence of positive QuantiFERON gold in-tube testing in hidradenitis suppurativa

Aim: Hidradenitis suppurativa (HS) is a chronic, recurrent, inflammatory disease of the apocrine sweat glands. Tumor necrosis factor-alpha (TNF-α) inhibitors are commonly used to treat HS. However, prior to initiating therapy patients must be screened for mycobacterium tuberculosis (mTB) exposure. Several mTB screening tests based on interferon gamma release assays are commercially available, but the performance of these assays in the HS population is unknown. The purpose of this study was to investigate the performance of the QuantiFERON gold in-tube assay (QFT-GIT) in a cohort of patients with HS.Methods: This prospective study was conducted through the Wound Etiology and Healing (WE-HEAL) study. QFTGIT testing was performed using a commercial laboratory. Patients with positive test results underwent follow-up testing to evaluate for latent tuberculosis infection (LTBI). Data were collected on demographics and disease activity scores including Hurley stage, HS Sartorius score (HSS) and active nodule (AN) count.Results: Of the 69 patients with a confirmed diagnosis of HS, seven (10.1%) tested QFT-GIT positive and 5.8% were diagnosed with LTBI.Conclusions: QFT-GIT results did not correlate with demographic characteristics or HS disease activity.

Impact of Choice of Test for Latent Tuberculosis Infection on Treatment Acceptance and Completion.

Objective:The aim of this study is to assess whether choice of test for tuberculosis (TB) infection affects decisions to accept and complete treatment among contacts to TB cases.Methods:Retrospective study is conducted in which TB contacts, ⩾15 years old during 2005 and 2009, were tested for infection with either a tuberculin skin test (TST) or an interferon-gamma release assay test, the QuantiFERON-TB Gold In-Tube (QFT-GIT).Results:Of 658 persons with valid test results, 185 (28%) had positive results, including 128 of 406 (32%) who had TST and 57 of 252 (23%) who received QFT-GIT. Treatment acceptance was 43 of 57 (75%) among QFT-GIT-positive and 97 of 128 (76%) among TST-positive persons (risk ratio [RR] = 1.0, 95% confidence interval [CI], 0.83-1.2). Treatment completion was 56% among QFT-GIT-positive (32 of 57) and 59% (75 of 128) among TST-positive persons (RR = 0.96, 95% CI, 0.73-1.26).Discussion:Our study showed no difference in proportions of TB contacts ⩾15 years old with positive TST results who accepted or completed LTBI treatment compared with those with positive QFT-GIT results. Future studies should include high-risk persons with no known TB exposure, who constitute the main reservoir for TB cases in the United States.

Outdoor air pollution affects tuberculosis development based on geographical information system modeling

Background : Daily intake of air is 30 Ib as compared with 2-Ib of food and 4½ of water. Thereby, breathing-contaminated air is as harmful as drinking or eating contaminated water or food, respectively. Recent research has highlighted the extent of outdoor air pollution in large cities and warranted high-quality studies to clarify the magnitude of the problem. Here, we evaluated the possible association between tuberculosis (TB) development and exposure to outdoor air pollution in a metropolitan city of Tehran. Methods: Extraction and analysis of relevant data. Investigation performed on TB patients (n = 1167) that were residing in Tehran for the past 10 years. The average concentration of sulfur dioxide (SO2), nitrogen dioxide, carbon monoxide (CO), and particles with an aerodynamic diameter of ≤ 2.5μm (PM2.5) and ≤ 10.0 (PM10) was measured from Tehran Air Quality Control Corporation (TAQCC). Patient and ecological informations were analyzed using geographical information system. Results: Based on TAQCC, Tehran had an average of 180–250 polluted days per year for the last 10 years. The high incidence of pulmonary TB (18 to 31/100,000) was detected in populations which were exposed to high concentration of CO (2.7 to 5.2 parts per million, 95% confidence interval [CI]; 1.10 to 1.90) and PM2.5(35 to 42μg/m3; 95% CI 1.03 to 1.80). The level of SO2,NO, and PM10was also high but not significantly related to TB (P > 0.05). Conclusion: The long-term exposure to PM2.5 and CO was positively associated with TB development.

Pulmonary Immune Mechanisms in Tuberculosis

Tuberculosis is transmitted by inhalation of Mycobacterium tuberculosis-containing aerosols; 75 % of all patients show pulmonary manifestation. Immune responses after exposure that lead to clinical symptoms occur mainly in the respiratory tract and are only poorly understood. In most cases, cells of the innate immune system are believed to control the growth of or eradicate inhaled mycobacteria. However, this cannot be verified in vivo using standard methods. Subsequently, CD4+ and CD8+ T cell-driven adaptive immune responses are induced that attempt to control bacterial growth. The humoral defence appears to be less important. This article gives an overview of the current understanding of pulmonary immune mechanisms during exposure, latent infection, active disease and therapy of tuberculosis.

Occupational tuberculosis in South Africa: are health care workers adequately protected?

Setting: A provincial tertiary hospital in Gauteng province, South Africa, with a high burden of tuberculosis (TB) patients and high risk of TB exposure among health care workers (HCWs). Objective: To determine HCWs' adherence to recommended TB infection prevention and control practices, TB training and access to health services and HCW TB rates. Design: Interviews with 285 HCWs using a structured questionnaire as part of a large, international mixed-methods study. Results: Despite 10 HCWs (including seven support HCWs) acquiring clinical TB during their period of employment, 62.8% of interviewees were unaware of the hospital's TB management protocol. Receipt of training was low (34.5% of all HCWs and <5% of support HCWs trained on TB transmission; 27.5% of nurses trained on respirator use), as was use of respiratory protection (44.5% of HCWs trained on managing TB patients). Support HCWs were over 36 times more likely to use respiratory protection if trained; nurses who were trained were approximately 40 times more likely to use respirators if they were readily available. Conclusion: Improved coordination and uptake of TB infection prevention training is urgently needed, especially for non-clinical HCWs in settings of regular exposure to TB patients. Adequate supplies of appropriate respiratory protection must be made available.

Mediating Effect of Repeated Tuberculosis Exposure on the Risk of Transmission to Household Contacts of Multidrug-Resistant Tuberculosis Patients.

.Primary Mycobacterium tuberculosis transmission is an important driver of the global epidemic of resistance to tuberculosis drugs. A few studies have compared tuberculosis infection in contacts of index cases with different drug-resistant profiles, suggesting that contacts of multidrug-resistant (MDR) tuberculosis cases are at higher risk. Repeated tuberculosis exposure in contacts of MDR tuberculosis patients through recurrent tuberculosis may modify this relationship. We compared tuberculosis infection in household contacts of MDR and drug-susceptible (DS) tuberculosis patients from six cities in southeastern China and investigated whether repeated tuberculosis exposure was a mediating factor. Tuberculosis infection was defined as a tuberculin skin test induration ≥ 10 mm. In all, 111 (28.0%) of 397 household contacts of MDR tuberculosis patients and 165 (24.7%) of 667 contacts of DS tuberculosis index cases were infected with tuberculosis. In a multivariate model not including the previous tuberculosis exposure, contacts of MDR tuberculosis patients had a higher likelihood of tuberculosis infection (adjusted odds ratio [AOR] = 1.37; 95% confidence interval [CI] = 1.01–1.84; P = 0.041). In a separate multivariate model adjusted for the previous tuberculosis exposure, the odds ratio of tuberculosis infection flipped and contacts of MDR cases were now at lower risk for tuberculosis infection (AOR = 0.55; 95% CI = 0.38–0.81; P = 0.003). These findings suggest prior tuberculosis exposure in contacts strongly mediates the relationship between tuberculosis infection and the index drug resistance profile. Prior studies showing lower risk of developing tuberculosis among contacts of MDR tuberculosis patients may be partially explained by a lower rate of tuberculosis infection at baseline.