Epidemiology of a tuberculosis outbreak in a rural Missouri high school

Diagnostic performance of a novel ESAT6-CFP10 skin test for tuberculosis infection in school tuberculosis outbreak in China

Background

The ESAT6-CFP10 (EC) skin test is recommended by the World Health Organization for latent tuberculosis infection (LTBI). However, it is still unknown how the EC skin test performs in students during a school tuberculosis outbreak.

Methods

We conducted an epidemiological investigation to assess the performance of the EC skin test in this high-risk population.

Results

A total of 9 active student patients were confirmed in the same class as the index case, with an incidence rate of 18.0% (9/50). Among the 50 close contacts, 14 (28%) were over 15 years old and had a chest X-ray (CXR), and none of them had abnormal CXR findings. The rates of positive tuberculin skin test (TST) ≥ 5 mm and < 10 mm, ≥ 10 mm and < 15 mm, and ≥ 15 mm were 12.0% (6/50), 16.0% (8/50), and 10.0% (5/50), respectively. On the second screening, 44 students with the same class as the index case had the EC skin test, of which 31 (70.5%) had positive EC tests. All patients had negative sputum smear results, of whom 4 (44.4%) had positive Xpert results; three had a TST induration diameter between 5 mm and 10 mm, but all of them had an EC diameter > 15 mm; 5 (55.6%) had abnormal CXR results, but all the confirmed patients had abnormal CT results; Except for four cases that were diagnosed by Xpert, the remaining five were confirmed by CT scan.

Conclusion

The novel EC skin test performed well in students during the school tuberculosis outbreak. In some special conditions, such as when the index case is bacteriologically positive for tuberculosis and the rate of LTBI is higher than the average for the local same-age group, secondary screening is recommended 2-3 months after the first screening. Furthermore, we cannot ignore the role of CT in the diagnosis of early student tuberculosis.

Cost-effectiveness of 3-months isoniazid and rifapentine compared to 9-months isoniazid for latent tuberculosis infection: a systematic review

BACKGROUND

We conducted a systematic review examining the cost effectiveness of a 3-month course of isoniazid and rifapentine, known as 3HP, given by directly observed treatment, compared to 9 months of isoniazid that is directly observed or self-administered, for latent tuberculosis infection. 3HP has shown to be effective in reducing progression to active tuberculosis and like other short-course regimens, has higher treatment completion rates compared to standard regimens such as 9 months of isoniazid. Decision makers would benefit from knowing if the higher up-front costs of rifapentine and of the human resources needed for directly observed treatment are worth the investment for improved outcomes.

METHODS

We searched PubMed, Embase, CINAHL, LILACS, and Web of Science up to February 2022 with search concepts combining latent tuberculosis infection, directly observed treatment, and cost or cost-effectiveness. Studies included were in English or French, on human subjects, with latent tuberculosis infection, provided information on specified anti-tubercular therapy regimens, had a directly observed treatment arm, and described outcomes with some cost or economic data. We excluded posters and abstracts, treatment for multiple drug resistant tuberculosis, and combined testing and treatment strategies. We then restricted our findings to studies examining directly-observed 3HP for comparison. The primary outcome was the cost and cost-effectiveness of directly-observed 3HP.

RESULTS

We identified 3 costing studies and 7 cost-effectiveness studies. The 3 costing studies compared directly-observed 3HP to directly-observed 9 months of isoniazid. Of the 7 cost-effectiveness studies, 4 were modelling studies based in high-income countries; one study was modelled on a high tuberculosis incidence population in the Canadian Arctic, using empiric costing data from that setting; and 2 studies were conducted in a low-income, high HIV-coinfection rate population. In five studies, directly-observed 3HP compared to self-administered isoniazid for 9 months in high-income countries, has incremental cost-effectiveness ratios that range from cost-saving to $5418 USD/QALY gained. While limited, existing evidence suggests 3HP may not be cost-effective in low-income, high HIV-coinfection settings.

CONCLUSION

Cost-effectiveness should continue to be assessed for programmatic planning and scale-up, and may vary depending on existing systems and local context, including prevalence rates and patient expectations and preferences.

Selection of the cutoff value of the tuberculin skin test for diagnosing students who need preventive treatment: A school-based cross-sectional study

Objective

Tuberculosis outbreaks in schools are common in China. This study aimed to introduce and evaluate a new screening process to help control outbreaks.

Methods

Screening information of students in three schools with tuberculosis outbreaks was collected. QuantiFERON-TB gold in-tube (QFT) results were used as the reference standard to determine the cutoff value of the tuberculin skin test (TST) for diagnosing students who need to have preventive medication.

Results

A total of 1,232 students and teachers from three different schools that all had more than three student patients with tuberculosis were included in this study. In total, 308 (25.0%) students had an induration diameter ≥10 mm; among students in a class different from the index case, the infection rate was 24.4% (264/1,084), which was lower than the rate among students in the same class (29.7%) (P = 0.157). Students in the same class as the index tuberculosis case had a much higher QFT positivity compared to those in a different class (58.1% vs. 7.7%, P < 0.0001). Diagnostic agreement between TST ≥10 mm and QFT was 36.6%. The diagnostic value reached the highest when the induration diameter of TST was ≥9 mm, with a sensitivity and specificity of 94.1% (95% CI: 89.4%–97.1%) and 27.6% (95% CI: 24.9%–30.4%), respectively. The area under the curve (AUC) was 0.664 (95% CI: 0.637–0.690, P < 0.0001).

Conclusion

In tuberculosis outbreaks in schools, if there are three or more cases of students with tuberculosis in a class or if the moderate or strong TST positivity rate is much higher than the normal range in the region, attention should be paid to those with moderately positive TST results. Interferon-gamma release assays (IGRAs) are recommended to be conducted following TST on the day of reading the results, especially among students sharing the same class with the index case. In resource-poor areas lacking IGRAs, the induration diameter of TST can be appropriately reduced from 15 to 9 mm to enhance the sensitivity of TST.

High rate of transmission in a pulmonary tuberculosis outbreak in a junior high school in China, 2020

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School tuberculosis outbreaks are common in China

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Students with PPD ≥ 15 mm are recommended to have prophylactic treatment

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More attention should be paid to students with PPD ≥ 10 mm and < 15 mm in school TB outbreaks

Background

School tuberculosis outbreaks are common in China. This study aimed to introduce a new screening process to help control outbreaks.

Methods

An epidemiological investigation into a school-based tuberculosis outbreak was conducted in order to identify the origin of the infection, and how it was transmitted.

Results

In total, 10 confirmed active tuberculosis cases were diagnosed among student contacts in the index case's class, giving an incidence rate of 19.2% (10/52). Three were found through a proactive visit and seven through screening. Of the nine secondary cases, two had purified protein derivation of tuberculin (PPD) ≥ 15 mm or blister (confirmed by computed tomography (CT) scan before preventive therapy), five had TST ≥ 10 mm and < 15 mm (two with abnormal chest radiography scan and three with positive T-SPOT tests, confirmed by CT) and two with PPD ≥ 5 mm and < 10 mm (confirmed by CT scan through proactive visit).

Conclusion

Further to our results based on this school outbreak, a new screening process is recommended that involves conducting interferon gamma release assays on those students with PPD ≥ 5 mm and < 15 mm if there are three or more active tuberculosis patients in the class with an epidemiological link. Furthermore, a CT scan is recommended for students who have had a recent tuberculosis infection before they have preventive therapy.

A scoping review of paediatric latent tuberculosis infection care cascades: initial steps are lacking

BACKGROUND AND OBJECTIVES

Identifying and treating children with latent tuberculosis infection (TB infection) is critical to prevent progression to TB disease and to eliminate TB globally. Diagnosis and treatment of TB infection requires completion of a sequence of steps, collectively termed the TB infection care cascade. There has been no systematic attempt to comprehensively summarise literature on the paediatric TB infection care cascade.

METHODS

We performed a scoping review of the paediatric TB infection care cascade. We systematically searched PubMed, Cumulative Index to Nursing and Allied Health Literature, Cochrane and Embase databases. We reviewed articles and meeting abstracts that included children and adolescents ≤21 years old who were screened for or diagnosed with TB infection, and which described completion of at least one step of the cascade. We synthesised studies to identify facilitators and barriers to retention, interventions to mitigate attrition and knowledge gaps.

RESULTS

We identified 146 studies examining steps in the paediatric TB infection care cascade; 31 included children living in low-income and middle-income countries. Most literature described the final cascade step (treatment initiation to completion). Studies identified an array of patient and caregiver-related factors associated with completion of cascade steps. Few health systems factors were evaluated as potential predictors of completion, and few interventions to improve retention were specifically tested.

CONCLUSIONS

We identified strengths and gaps in the literature describing the paediatric TB infection care cascade. Future research should examine cascade steps upstream of treatment initiation and focus on identification and testing of at-risk paediatric patients. Additionally, future studies should focus on modifiable health systems factors associated with attrition and may benefit from use of behavioural theory and implementation science methods to improve retention.

Multidrug-resistant tuberculosis transmission among middle school students in Zhejiang Province, China

Background

Despite significant advancements in the treatment and diagnosis of tuberculosis (TB) over the past decade, drug-resistant TB remains an increasing threat to public health. TB outbreaks are most commonly reported in schools considering the delay in TB diagnosis, sustained contact, and overcrowding observed in schools. This report describes multidrug-resistant TB (MDR-TB) transmission in a school in Zhejiang Province. We aimed to raise awareness regarding MDR-TB transmission among students.

Case presentation

The index patient was a 16-year-old girl in the second year of junior middle school in Zhejiang Province, China, who had been experiencing persistent cough and expectoration for 37 days since 1 March 2014. She tested positive for smear pulmonary and extrapulmonary TB on 8 April 2014 and was subsequently diagnosed with MDR-TB on 1 May 2014. However, the patient was resistant to isoniazid, rifampicin, ethambutol, and streptomycin. Thus, she was suspended from school for anti-TB treatment. All 54 students who were in close contact with the index patient in the same class were screened, and 5 tested positive on the tuberculin skin test. Their exposure time to the index patient was approximately 37 days. Three classmates were subsequently diagnosed with MDR-TB, with similar resistance profiles nearly two years later. Their average discovery delay was 55 days. These three classmates were also suspended from school for anti-TB treatment. During the treatment period, four students visited the local TB-designated hospital for further consultation every month and were followed up once a month by the local community health service center until they were completely cured.

Conclusions

Discovery delay for an index patient played a primary role in MDR-TB transmission inside the school. To immediately detect TB, morning examinations in schools should be performed. TB trackers and case managers should work closely with public health workers and physicians in cases of TB outbreaks or transmissions involving students. Moreover, individuals who are in close contact with MDR-TB patients should undergo careful clinical follow-up for at least two years. Implementing a joint examination strategy to ensure early detection, diagnosis, and treatment of MDR-TB transmission is recommended.

Tuberculosis Transmission in a Primary School and a Private Language School. An Estimation of Infectivity

Introduction: Belgium is a country with low incidence of tuberculosis (TB) and a very low number of TB cases in children. Children in contact with an adult smear-positive TB case are at high risk of transmission. Early diagnosis is important as young children have a significant predisposition of developing TB disease. In this paper, we describe two outbreaks after exposure to, respectively, two teachers with smear-positive pulmonary TB: one in a primary school, a nursery teacher, and another in a private language school. Methods: An exposure investigation was carried out in both index cases household and school, according to the stone-in-the-pond principle. The tuberculin skin test (TST) was used a screening tool. The time elapsed between TB diagnosis in the index case and contact investigation was, respectively, 1 and 3 weeks. If this initial test was negative, it was repeated after a "window period" of ≥8 weeks. Results: Index cases showed a transmission rate of, respectively, 13 and 40% in their classes at school, defined as casual contacts. The proximity of contact increased the risk of infection. TB disease was observed in, respectively, 4 and 11% of all the casual contacts; all of them were children younger than 5 years old. TB-infected and children with active TB disease had good compliance with recommended treatment. Uptake of chemoprophylaxis during the "window period" was poor, respectively, only 32-42%, in children under 5 years with an initially negative TST. Discussion: The World Health Organization recommends to screen all young children (<5 years old) who have close contact with a person affected by pulmonary TB and to initiate Latent tuberculosis infection treatment even before infection can be demonstrated, after ruling out active TB disease. Despite this knowledge, a small percentage of the children younger than 5 years with no proof of infection was treated with the proposed chemoprophylactic treatment, in both cases. Conclusion: This exposure investigation of two teachers detects high transmission among family contacts and school casual contacts. Recommendations for chemoprophylactic treatment in children <5 years showed low compliance, reflecting the difficulty of communication to staff, parents, and children in a school outbreak. It is essential to develop a new approach for this vulnerable group of patients. This approach could be improved, applied, and evaluated by National TB Control Programs, involving public and private health services. Public health authorities play a role in raising public awareness about the risks of TB for young children.

Social network analysis and whole genome sequencing in a cohort study to investigate TB transmission in an educational setting

BACKGROUND

TB outbreaks in educational institutions can result in significant transmission and pose a considerable threat to TB control. Investigation using traditional microbiological and epidemiological tools can lead to imprecise screening strategies due to difficulties characterising complex transmission networks. Application of whole genome sequencing (WGS) and social network analysis can provide additional information that may facilitate rapid directed public health action. We report the utility of these methods in combination with traditional approaches for the first time to investigate a TB outbreak in an educational setting.

METHODS

Latent tuberculosis infection (LTBI) cases were screenees with a positive T-SPOT®.TB test. Active TB cases were defined through laboratory confirmation of M. tuberculosis on culture or through clinical or radiological findings consistent with infection. Epidemiological data were collected from institutional records and screenees. Samples were cultured and analysed using traditional M. tuberculosis typing and WGS. We undertook multivariable multinomial regression and social network analysis to identify exposures associated with case status and risk communities.

RESULTS

We identified 189 LTBI cases (13.7% positivity rate) and nine active TB cases from 1377 persons screened. The LTBI positivity rate was 39.1% (99/253) among persons who shared a course with an infectious case (odds ratio 7.3, 95% confidence interval [CI] 5.2 to 10.3). The community structure analysis divided the students into five communities based on connectivity, as opposed to the 11 shared courses. Social network analysis identified that the community including the suspected index case was at significantly elevated risk of active disease (odds ratio 7.5, 95% CI 1.3 to 44.0) and contained eight persons who were lost to follow-up. Five sputum samples underwent WGS, four had zero single nucleotide polymorphism (SNP) differences and one had a single SNP difference.

CONCLUSION

This study demonstrates the public health impact an undiagnosed case of active TB disease can have in an educational setting within a low incidence area. Social network analysis and whole genome sequencing provided greater insight to evolution of the transmission network and identification of communities of risk. These tools provide further information over traditional epidemiological and microbiological approaches to direct public health action in this setting.

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

OBJECTIVE

Quantify tuberculosis (TB) risk attributable to dorm room exposure in addition to classroom exposure.

METHODS

Adolescent 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.

RESULTS

A 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).

CONCLUSION

The 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.

Tuberculosis Transmission in Households and Classrooms of Adolescent Cases Compared to the Community in China

The aim of this paper is to evaluate the link between the history of exposure to tuberculosis (TB) in the household and diagnosed TB cases at school, and to compare the detection rate of active TB among household contacts and classroom contacts of adolescent TB cases with the rates among contacts of healthy controls. From November 2016 to December 2017, a prospective matched case-control study was conducted using passively identified index adolescent student cases from the TB surveillance system and healthy controls (matched by county, school type, sex, age and ethnicity). Contacts in households and classrooms of index cases and of controls were investigated. Matched tabulation of 117 case-control pairs revealed exposure to TB in the household as a strong risk factor (odds ratio (OR) = 21.0, 95% confidence interval (CI): 3.4, 868.6). Forty-five (case detection rate 0.69%) and two (case detection rate 0.03%) new active TB cases were detected among 6512 and 6480 classroom contacts of the index cases and controls, respectively. Having an index case in the classroom significantly increased the risk of classmates contracting active TB (OR = 22.5, 95% CI: 5.9, 191.4). Our findings suggested that previous exposure to TB in the household could lead a child to catch TB at school, then spread TB to classmates.

A contact investigation after exposure to a child with disseminated tuberculosis mimicking inflammatory bowel disease

Purpose

Tuberculosis (TB) is one of the most important diseases that cause significant mortality and morbidity in young children. Data on TB transmission from an infected child are limited. Herein, we report a case of disseminated TB in a child and conducted a contact investigation among exposed individuals.

Methods

A 4-year-old child without Bacille Calmette-Guérin vaccination was diagnosed as having culture-proven disseminated TB. The child initially presented with symptoms of inflammatory bowel disease, and nosocomial and kindergarten exposures were reported. The exposed individuals to the index case were divided into 3 groups, namely household, nosocomial, or kindergarten contacts. Evaluation was performed following the Korean guidelines for TB. Kindergarten contacts were further divided into close or casual contacts. Chest radiography and tuberculin skin test or interferon-gamma-releasing assay were performed for the contacts.

Results

We examined 327 individuals (3 household, 10 nosocomial, and 314 kindergarten contacts), of whom 18 (5.5%), the brother of the index patient, and 17 kindergarten children were diagnosed as having latent TB infection (LTBI). LTBI diagnosis was more frequent in the children who had close kindergarten contact with the index case (17.1% vs. 4.4%, P=0.007). None of the cases had active TB.

Conclusion

This is the first reported case of TB transmission among young children from a pediatric patient with disseminated TB in Korea. TB should be emphasized as a possible cause of chronic diarrhea and failure to thrive in children. A national TB control policy has been actively applied to identify Korean children with LTBI.

Expected background rates of latent TB infection in London inner city schools: lessons from a TB contact investigation exercise in a secondary school

Following an extensive contact tracing exercise at a school in a London borough with one of highest tuberculosis (TB) rates in England, we estimated the background prevalence of latent TB infection to be significantly less than the widely accepted 10%. We screened 271 pupils aged 14-15 years in two groups: 96 pupils in group 1 had significant exposure (>8 h/week in the same room) to a case of infectious TB and 175 in group 2 who had minimal exposure. In group 1, 26% were diagnosed with latent or active TB, compared to 6.3% in group 2. Risk factors for TB infection (e.g. previous exposure or link to high-prevalence communities) were analysed using a cohort study design. In the univariable analysis only being in contact group 1 was statistically significantly associated with being a case (OR 5.25, 95%, P < 0.001). In the multivariable model contact group 1 remained significantly associated with being a case (adjusted OR 4.40, P = 0.001). We concluded that the 6.3% yield of TB infection in contact group 2 is either similar to or higher than the background prevalence rate of latent TB infection (LTBI) in this high TB prevalence London borough. Other parts of England with lower TB prevalence are likely to have even lower LTBI rates.

The Risk of Mycobacterium tuberculosis Transmission from Pediatric Index Cases to School Pupils

This study is the largest report on Mycobacterium tuberculosis transmission rate (TR) from children with pulmonary tuberculosis to school pupils. Higher TR (around 21.6%) was observed in contacts of smear-positive children. TR from pediatric smear-negative index cases was around 0. If our data are confirmed, school contacts of a smear-negative index case could be screened only by clinical evaluation and tuberculin skin test, avoiding the routine use of chest radiographs in children less than 5 years of age as well.

Concurrent Outbreaks of Tuberculosis in a School and the Wider Community in Macau

Between 2009 and 2012, 22 adolescents of age 15-20 from a day school in Macau were diagnosed with tuberculosis. Detection of multiple molecular clusters may suggest the presence of concurrent outbreaks, and could reflect also ongoing transmissions in the community. Careful interpretation of molecular epidemiology data is crucial in contact investigations.

Outbreak of multidrug-resistant tuberculosis in two secondary schools

OBJECTIVES

To describe an outbreak of multidrug-resistant tuberculosis (MDR-TB) in two schools

METHODS

This was a prospective, observational study of an outbreak of MDR-TB in 2 schools located in the towns of Onda and Nules, in the Spanish province of Castellon, from the moment of detection in November 2008 until November 2014, including patient follow-up and contact tracing.

RESULTS

Five cases of MDR-TB were diagnosed. Overall attack rate was 0.9%, and among the contacts traced, 66 had latent tuberculous infection, with an infection rate of 14.4%. Molecular characterization of the 5M. tuberculosis isolates was performed by restriction fragment length polymorphism (RFLP) analysis of the IS6110 sequence. In all 5 patients, cultures were negative at 4-month follow-up, showing the efficacy of the treatment given. No recurrence has been reported to date.

CONCLUSIONS

In the context of globalization and the increased prevalence of MDR-TB, outbreaks such as the one presented here are only to be expected. Contact tracing, strict follow-up of confirmed cases, the availability of fast diagnostic techniques to avoid treatment delay, and chemoprophylaxis, together with the molecular characterization of strains, are still essential.

Transmissibility of tuberculosis among school contacts: an outbreak investigation in a boarding middle school, China

Tuberculosis (TB) outbreak occurred in a boarding middle school of China. We explored its probable sources and quantified the transmissibility and pathogenicity of TB. Clinical evaluation, tuberculin skin testing and chest radiography were conducted to identify TB cases. Mycobacterium tuberculosis isolates underwent genotyping analysis to identify the outbreak source. A chain-binomial transmission model was used to evaluate transmissibility and pathogenicity of TB. A total of 46 active cases were ascertained among 258 students and 15 teachers/staff, an attack rate of 16.8%. Genetic analyses revealed two groups of M. tuberculosis cocirculating during the outbreak and possible importation from local communities. Secondary attack rates among students were 4.1% (2.9%, 5.3%) within grade and 7.9% (4.9%, 11%) within class. An active TB case was estimated to infect 8.4 (7.2, 9.6) susceptible people on average. The smear-positive cases were 28 (8, 101) times as infective as smear-negative cases. Previous BCG vaccination could reduce the probability of developing symptoms after infection by 70% (1.4%, 91%). The integration of clinical evaluation, genetic sequencing, and statistical modeling greatly enhanced our understanding of TB transmission dynamics. Timely diagnosis of smear-positive cases, especially in the early phase of the outbreak, is the key to preventing further spread among close contacts.

Shared air: a renewed focus on ventilation for the prevention of tuberculosis transmission

Background

Despite an improvement in the overall TB cure rate from 40–74% between 1995 and 2011, TB incidence in South Africa continues to increase. The epidemic is notably disquieting in schools because the vulnerable population is compelled to be present. Older learners (age 15–19) are at particular risk given a smear-positive rate of 427 per 100,000 per year and the significant amount of time they spend indoors. High schools are therefore important locations for potential TB infection and thus prevention efforts.

Methods and Findings

Using portable carbon dioxide monitors, we measured CO₂ in classrooms under non-steady state conditions. The threshold for tuberculosis transmission was estimated using a carbon dioxide-based risk equation. We determined a critical rebreathed fraction of carbon dioxide () of 1·6%, which correlates with an indoor CO₂ concentration of 1000 ppm. These values correspond with a ventilation rate of 8·6 l/s per person or 12 air exchanges per hour (ACH) for standard classrooms of 180 m³.

Conclusions

Given the high smear positive rate of high-school adolescents in South Africa, the proposal to achieve CO₂ levels of 1000ppm through natural ventilation (in the amount 12 ACH) will not only help achieve WHO guidelines for providing children with healthy indoor environments, it will also provide a low-cost intervention for helping control the TB epidemic in areas of high prevalence.

Clinical peculiarities of tuberculosis

The ongoing spread of tuberculosis (TB) in poor resource countries and the recently increasing incidence in high resource countries lead to the need of updated knowledge for clinicians, particularly for pediatricians. The purpose of this article is to provide an overview on the most important peculiarities of TB in children. Children are less contagious than adults, but the risk of progression to active disease is higher in infants and children as compared to the subsequent ages. Diagnosis of TB in children is more difficult than in adults, because few signs are associated with primary infection, interferon-gamma release assays and tuberculin skin test are less reliable in younger children, M. tuberculosis is more rarely detected in gastric aspirates than in smears in adults and radiological findings are often not specific. Treatment of latent TB is always necessary in young children, whereas it is recommended in older children, as well as in adults, only in particular conditions. Antimycobacterial drugs are generally better tolerated in children as compared to adults, but off-label use of second-line antimycobacterial drugs is increasing, because of spreading of multidrug resistant TB worldwide. Given that TB is a disease which often involves more than one member in a family, a closer collaboration is needed between pediatricians and clinicians who take care of adults.

Infection of great apes and a zoo keeper with the same Mycobacterium tuberculosis spoligotype

An animal keeper was diagnosed with pulmonary tuberculosis (TB) after bi-annual screening for latent TB infection in zoo employees. In the same period, several bonobos of the zoo were suffering from TB as well. The Mycobacterium tuberculosis strains from both the animal keeper and the bonobos appeared identical. We provide evidence that the animals infected their keeper.

A tuberculosis outbreak among senior high school students in China in 2011

OBJECTIVE

An outbreak of pulmonary tuberculosis (PTB) occurred in students attending Licai Training School, Gujiao City, China, in early 2011. The epidemic characteristics and possible contributory factors relating to the spread of this outbreak of PTB were studied in a field investigation and are reported here.

METHODS

Cases were detected by PTB symptom screening, tuberculin skin testing (TST), chest X-radiography, and examination of sputum smears and cultures for all students, school staff and close family contacts of patients with PTB.

RESULTS

Of the 287 students attending the school, 45 (15.7%) were diagnosed with PTB and two (0.7%) had a positive smear. No PTB was found among staff and close family contacts. Prevalence was high in Science Class 27 and the two floors of the dormitory building where the smear-positive TB patients studied and lived. The frequency of strong TST positivity was also high in Science Class 27 and among close contacts living in the same dormitories as the PTB patients.

CONCLUSIONS

Several avoidable factors likely to have enhanced disease transmission were identified and several recommendations are made to reduce the risk of future TB outbreaks in schools.

Pulmonary tuberculosis outbreak in a pediatric population

Community-based outbreaks of Mycobacterium tuberculosis are uncommon in the United States but represent a dramatic type of epidemic that can lead to considerable investigations. Most of our knowledge regarding spread of tuberculosis (TB) has accumulated from the study of outbreaks. We describe the most recent outbreak of TB in Genesee County, Michigan. In February 2007, isoniazid-sensitive infectious pulmonary TB was identified in a 45-year-old African American grandmother who frequently provided care for her grandchildren and other children. The source case was reported to the Genesee County Health Department, which started an investigation to identify family and social contacts. We reviewed past medical records of contacts and prioritized them for evaluation based on the period of exposure to the index case. Health department staff screened contacts using clinical evaluation, tuberculin skin test, and chest radiography when indicated. Results were reviewed, and data were analyzed using descriptive inferential and epidemiological statistics.

Outbreak of pulmonary tuberculosis in a Chinese high school, 2009-2010

BACKGROUND

In February 2009, a high school student was diagnosed with sputum-smear positive pulmonary tuberculosis (TB). One year later, 2 other students in the same grade developed sputum-smear positive TB.

METHODS

We used tuberculin skin testing (TST), chest radiography, sputum smear, and symptomatology for case identification. We defined latent TB infection (LTBI) as a TST induration of 15 mm or larger, probable TB as a chest radiograph indicative of TB plus productive cough/hemoptysis for at least 2 weeks or TST induration of 15 mm or larger, and confirmed TB as 2 or more positive sputum smears or 1 positive sputum smear plus a chest radiograph indicative of TB.

RESULTS

Of students in the same grade as the primary case-student, 26% (122/476) had LTBI and 4.8% (23/476) had probable/confirmed TB. Of teachers, 43% (18/42) had LTBI and none had probable/confirmed TB. Sharing a classroom with the primary case-student increased risk for LTBI (rate ratio = 2.5; 95% CI: 1.9-3.4) and probable/confirmed TB (rate ratio = 17, 95% CI: 7.8-39). Of students with LTBI in February 2009 who refused prophylaxis, 50% (11/22) had probable/confirmed TB in April 2010.

CONCLUSIONS

This TB outbreak was likely started by delayed diagnosis of TB in the case-student and was facilitated by lack of post-exposure chemoprophylaxis. Post-exposure prophylaxis is strongly recommended for all TST-positive students.

Counting the homeless: a previously incalculable tuberculosis risk and its social determinants

Tuberculosis (TB) surveillance among the homeless is not supported by the political will necessary for TB elimination. We merged the first stakeholder-accepted enumeration of homeless persons with existing surveillance data to assess TB risk among the homeless in Houston, Texas. The average incidence per 100,000 was 411 among homeless and 9.5 among housed persons. The homeless were more likely than the housed to be US-born, clustered, and in a larger-sized cluster. Multivariate analysis revealed that TB rates among the homeless were driven not by comorbidities but by social determinants. Homeless patients were hospitalized more days than the housed and required more follow-up time. Reporting of TB rates for populations with known health disparities could help reframe TB prevention and better target limited funds.

Transmission of tuberculosis within family-households

OBJECTIVE

The introduction of molecular typing methods in the 1990s to study the epidemiology of tuberculosis (TB) has significantly improved the possibilities of quantifying transmission of Mycobacterium tuberculosis in different human settings. The purpose of this study was to investigate transmission of TB in 35 family-households in Poland.

METHODS

Two PCR-based genotyping methods: spoligotyping and mycobacterial interspersed repetitive unit-variable number of tandem repeats (MIRU-VNTR) typing were used.

RESULTS

Of 78 patients, 49 (63%), could be assigned to intra-household transmission on the basis of identical DNA fingerprints upon a combined typing approach. However, if a single spoligotype spacer or a single MIRU-VNTR locus variation was tolerated in the cluster definition, the intra-household transmission raised to 85% of all patients. For 12 patients in 6 households, the M. tuberculosis isolates were clearly distinct in either spoligotyping or VNTR typing or in both genotyping methods, suggesting that these patients were infected by the sources in the community.

CONCLUSIONS

This study is the first to provide the results of a molecular epidemiological investigation performed within family-households in Poland. It shows the household setting as an important reservoir of M. tuberculosis transmission, and thus argues in favor of routine and extensive screening of the family contacts of TB patients.

Including the third dimension: a spatial analysis of TB cases in Houston Harris County

To reach the tuberculosis (TB) elimination goals established by the Institute of Medicine (IOM) and the Centers for Disease Control and Prevention (CDC), measures must be taken to speed the currently stagnant TB elimination rate and curtail a future peak in TB incidence. Increases in TB incidence have historically coincided with immigration, poverty, and joblessness; all situations that are currently occurring worldwide. Effective TB elimination strategies will require the geographical elucidation of areas within the U.S. that have endemic TB, and systematic surveillance of the locations and location-based risk factors associated with TB transmission. Surveillance data was used to assess the spatial distribution of cases, the yearly TB incidence by census tract, and the statistical significance of case clustering. The analysis revealed that there are neighborhoods within Houston/Harris County that had a heavy TB burden. The maximum yearly incidence varied from 245/100,000-754/100,000 and was not exclusively dependent of the number of cases reported. Geographically weighted regression identified risk factors associated with the spatial distribution of cases such as: poverty, age, Black race, and foreign birth. Public transportation was also associated with the spatial distribution of cases and census tracts identified as high incidence were found to be irregularly clustered within communities of varied SES.

Giving TB wheels: Public transportation as a risk factor for tuberculosis transmission

Previous geospatial analysis of the well-defined Houston Tuberculosis Initiative (HTI) database identified an association between the use of city-bus transportation (inclusive of time onboard) and Tuberculosis (TB) incidence in Houston/Harris County census tracts (paper submitted). This paper is an extension of those findings. Contact investigations on school buses have reported a high rate of positive tuberculin skin tests in the persons traveling with the index case and have shown an association with bus ride duration. In Houston, city bus routes are veins connecting even the most diverse of populations within the metropolitan area. Among HTI participants, TB patients who reported weekly bus use were more likely to have demographic and social risk factors associated with poverty, immune suppression and health disparities. An equal proportion of bus riders and non-bus riders were cultured for Mycobacterium tuberculosis (MTB), yet 75% of bus riders were clustered with a mean cluster size of 50.14, indicating recent transmission, compared to 56% of non-bus riders (OR = 2.4, p < 0.001) with a mean cluster size of 28.9 (p < 0.01). Individual bus routes, including one route servicing the local hospitals, were found to be risk factors for endemic MTB clustered strains and the routes themselves geographically connect the census tracts previously identified as having endemic TB.

Outbreak of tuberculosis among Guatemalan immigrants in rural Minnesota, 2008

OBJECTIVES

We described the outbreak investigation and control measures after the Minnesota Department of Health identified a cluster of tuberculosis (TB) cases among Guatemalan immigrants within three rural Minnesota counties in August 2008.

METHODS

TB cases were diagnosed by tuberculin skin test followed by chest radiography and sputum testing for Mycobacterium tuberculosis (M. tuberculosis). We reviewed medical records, interviewed patients, and completed a contact investigation for each infectious case. We used isolate genotyping to confirm epidemiologic links between cases.

RESULTS

The index case was a six-month-old U.S.-born male with Guatemalan parents. Although he experienced four months of cough and fever, TB was not considered at two medical visits but was diagnosed upon hospitalization in May 2008. The presumed source of infection was a Guatemalan male aged 25 years who sang in a band that practiced in the infant's house and whose pulmonary TB was diagnosed at hospitalization in June 2008, despite his having sought medical attention for symptoms seven months earlier. Among the 16 identified TB cases, 14 were outbreak-related. Three genetically distinct M. tuberculosis strains circulated. Of 150 contacts of the singer, 62 (41%) had latent TB infection and 13 (9%), including 10 children, had TB disease.

CONCLUSIONS

In this outbreak, delayed diagnoses contributed to M. tuberculosis transmission. Isolate genotyping corroborated the social links between outbreak-related patients. More timely diagnosis of TB among immigrants and their children can prevent TB transmission among communities in rural, low-incidence areas that might have limited resources for contact investigations.

Tuberculosis in kindergarten and primary school, Italy, 2008-2009

An outbreak of tuberculosis (TB) in Italy involved 19 schoolchildren with active TB and 43 with latent infection. The source of the outbreak was a school assistant born in Italy who had a family history of TB. This outbreak highlights the need for maintaining clinical and public health expertise in countries with low TB incidence.

[Tuberculosis outbreak in a primary school: description and reflections on the value of gastric juice in the management of micro-epidemics]

AIMS

To describe a tuberculosis outbreak in a primary school arising from a secondary case.

METHODS

Contact study and clinical study of exposed patients. Chest x-ray, gastric aspirate processing, and clinical evaluation of all children with a positive tuberculin skin test (TST) were recorded. Differential diagnosis between tuberculosis disease (TB) and latent tuberculosis infection (LTI).

RESULTS

Two groups were identified: one of higher exposure to the index case (> 6 hours/day, for 3 months; n=17 children) and one of sporadic exposure (< 6 hours/day; n=82 children). Clinical or bacteriological criteria for diagnosing TB were seen in 6 out of 17 (35%) highly exposed children. Four of them had clinical or radiological criteria. The other two children were asymptomatic and had a normal chest X ray, but had a positive gastric aspirate for M. tuberculosis. The overall infection rate (TB+LTI) was 94%. One child out of 82 (1.2%) sporadically exposed children had radiological criteria for TB. Staff latent infection rate was 15%. Apart from the index case, there were no other tuberculosis cases among the staff. Relative risk (RR) of exposed children was 28.5 (95% CI: 3-250).

CONCLUSIONS

Prolonged exposure to a baciliferous patient may infect almost every child exposed in closed groups. It can also cause a high attack rate. In this scenario, routine gastric aspirate may be considered for all children with a positive TST. It may identify early subclinical TB with an increased probability of isolating the M. tuberculosis. The potential benefit of this isolation may reach the entire cohort.

The potential to transmit Mycobacterium tuberculosis at a South African tertiary teaching hospital

OBJECTIVES

To assess the risk of nosocomial transmission by confirmed pulmonary tuberculosis (PTB) patients in a high TB/HIV incidence environment.

METHODS

Between November 2006 and April 2007, we carried out a cross-sectional survey of PTB patients with positive smears or cultures at an academic tertiary hospital in the Western Cape, South Africa.

RESULTS

Of 394 confirmed PTB patients, only 199 (50.5%) had a known HIV status, of whom 107 (53.8%) were HIV-co-infected. Sensitivity testing for Mycobacterium tuberculosis (TB) was done in 49.3% of patients with available cultures (140/284). Of these patients, 9.3% (13/140) had multidrug-resistant (MDR) TB strains. The turnaround times (TAT) for culture and susceptibility testing were delayed: mean TAT for cultures was 27 days (range 63 days) and for susceptibility testing was 42 days (range 63 days). One fifth of PTB patients (82/394) were diagnosed from wards that do not deal with TB on a daily basis. PTB inpatients were hospitalized for an average of 13 days and were on average transferred twice. Only 14.2% of all PTB patients were notified to the South Africa Provincial Department of Health. Throughout their hospitalization, PTB patients were potentially infectious.

CONCLUSIONS

The potential for nosocomial TB transmission in a setting of high TB and HIV co-infection with a high MDR prevalence, inconsistent infection prevention and control measures, and delayed diagnosis cannot be ignored. Barriers to TB infection control must urgently be addressed.

Population-based contact investigation of a cluster of tuberculosis cases in a small village

A cluster of five cases of tuberculosis (TB) in persons aged 19-23 years who were not close contacts was detected in a small village in Spain in 2006. All culture isolates had the same chromosomal-DNA restriction pattern. Contact investigations of family members, friends, workmates and schoolmates were complemented with tuberculin screening offered to the resident population born between 1976 and 1995. Expanded contact tracing detected two new cases of TB, 27 tuberculin conversions and an excess of latent tuberculosis infections (LTI) in persons born between 1978 and 1990. The contacts of two cases had a significantly elevated prevalence of LTI. Two secondary cases of TB, 33.3% of those diagnosed with LTI and 47.8% of the converters were unaware of any contact with the TB cases, but had frequented some of the same bars. This study suggests that a considerable percentage of the episodes of TB transmission in young people may escape detection in conventional contact studies.

Lessons learned from two school tuberculosis investigations

We describe the results from tuberculosis (TB) contact investigations of two high-school students. Following the development of active TB in two foreign-born students, contact investigations were performed to detect contacts with active TB disease or latent TB infection (LTBI). The two students developed pulmonary TB within 2 years of immigrating to the United States. Among household contacts, no case of active TB was identified; however, LTBI was identified in 7 of 20 persons screened (35%). Of the 104 high-risk school contacts identified, no cases of active TB disease were found, but 7 (9.3%) were diagnosed with LTBI. An additional 683 low-risk contacts were screened and 9 (1.5%) were positive. Schools and Public Health departments needs to be prepared for outbreak investigations and should screen only persons with a high risk of exposure to the index case with active TB in an attempt to identify secondary infections. Those persons with a low risk of exposure should not be screened.

Tuberculosis screening in internationally adopted children: the need for initial and repeat testing

OBJECTIVE

Because most internationally adopted children come from areas of high tuberculosis prevalence, an initial tuberculin skin test is recommended after arrival to the United States. We evaluated whether repeat testing of children >or=3 months after arrival to the United States would identify additional children with latent tuberculosis infection.

METHODS

Internationally adopted children who were seen at our International Adoption Center and had a tuberculin skin test within 2 months of arrival to the United States were eligible for the study. Children not diagnosed with tuberculosis with initial testing were retested at least 3 months later. The prevalence of tuberculosis on arrival and after repeat testing was determined, and potential risk factors for infection were examined.

RESULTS

Of the 527 internationally adopted children with an initial tuberculin skin test completed, 111 (21%) had evidence of latent tuberculosis infection. Repeat tuberculosis testing was complete for 191 internationally adopted children (46.9% of those who had an initially negative tuberculin skin test). Latent tuberculosis infection was found in 20% of those who were retested. No children were found to have active tuberculosis disease. Children with an initially positive tuberculin skin test result had slightly higher weight-for-age z scores at their initial clinic visit, whereas those whose tuberculin skin test result was positive after repeat testing had slightly lower weight-for-age z scores. A strong correlation between BCG immunization and tuberculin skin test result was observed.

CONCLUSIONS

Latent tuberculosis infection is common in internationally adopted children. A high proportion of internationally adopted children had an initially false-negative tuberculin skin test. Repeat tuberculosis testing of all internationally adopted children with an initially negative tuberculin skin test should be the standard of care for identifying tuberculosis infection and preventing tuberculosis disease in this high-risk population.

The effect of diagnostic delays on the drop-out rate and the total delay to diagnosis of tuberculosis

Background

Numerous patient and healthcare system-related delays contribute to the overall delay experienced by patients from onset of TB symptoms to diagnosis and treatment. Such delays are critical as infected individuals remain untreated in the community, providing more opportunities for transmission of the disease and adversely affecting the epidemic.

Methodology/Principal Findings

We present an analysis of the factors that contribute to the overall delay in TB diagnosis and treatment, in a resource-poor setting. Impact on the distribution of diagnostic delay times was assessed for various factors, the sensitivity of the diagnostic method being found to be the most significant. A linear relationship was found between the sensitivity of the test and the predicted mean delay time, with an increase in test sensitivity resulting in a reduced mean delay time and a reduction in the drop-out rate.

Conclusions/Significance

The results show that in a developing country a number of delay factors, particularly the low sensitivity of the initial sputum smear microscopy test, potentially increase total diagnostic delay times experienced by TB patients significantly. The results reinforce the urgent need for novel diagnostic methods, both for smear positive and negative TB, that are highly sensitive, accessible and point of care, in order to reduce mean delay times.

[The importance of genotyping of strains for the evaluation and interpretation of 5 school-based epidemic outbreaks of tuberculosis]

OBJECTIVE

The aim of this study was to describe 5 microepidemics of tuberculosis occurring in schools, establish the risk factors associated with the outbreaks, assess how well a concentric circles strategy for contact tracing predicts infection, and assess the usefulness of genotyping strains in the analysis of the outbreaks.

MATERIAL AND METHODS

The study assessed 5 epidemic outbreaks of tuberculosis using a standard contact tracing procedure. The outbreaks occurred in 2 day nurseries and 2 high schools between 1998 and 2005. Contacts were stratified using a concentric circle system based on level of exposure. DNA fingerprints of the available strains were determined based on the restriction fragment length polymorphism (RFLP) IS6110 and compared with the contact study to interpret the transmission of the infection.

RESULTS

We analyzed 5 outbreaks. Eighty-five contacts were analyzed in the first outbreak, 519 in the second, 116 in the third, 655 in the fourth, and 102 in the fifth. The rate of infection was 31%, 29%, 66%, 37.6%, and 32%, respectively. Secondary cases of active disease were detected: 9 in the first outbreak, 16 in the second, 5 in the third, 6 in the fourth, and 13 in the fifth. RFLP analysis revealed that a single strain was involved in 3 of the outbreaks, and in a fourth, at least 2 strains were involved. In outbreaks 2, 3, and 5, there was a significant association between the degree of contact and the probability of infection (P< .05). In all of the outbreaks, the relative risk of developing the disease was associated with the level of exposure.

CONCLUSIONS

Analysis of contacts based on concentric circles of risk predicts the likelihood of infection. RFLP facilitates analysis of complex transmission routes that are not detected using traditional methods of contact screening.

Field assessment of a model tuberculosis outbreak response plan for low-incidence areas

BACKGROUND

For a regional project in four low-incidence states, we designed a customizable tuberculosis outbreak response plan. Prior to dissemination of the plan, a tuberculosis outbreak occurred, presenting an opportunity to perform a field assessment of the plan. The purpose of the assessment was to ensure that the plan included essential elements to help public health professionals recognize and respond to outbreaks.

METHODS

We designed a semi-structured questionnaire and interviewed all key stakeholders involved in the response. We used common themes to assess validity of and identify gaps in the plan. A subset of participants provided structured feedback on the plan.

RESULTS

We interviewed 11 public health and six community stakeholders. The assessment demonstrated that (1) almost all of the main response activities were reflected in the plan; (2) the plan added value by providing a definition of a tuberculosis outbreak and guidelines for communication and evaluation. These were areas that lacked written protocols during the actual outbreak response; and (3) basic education about tuberculosis and the interpretation and use of genotyping data were important needs. Stakeholders also suggested adding to the plan questions for evaluation and a section for specific steps to take when an outbreak is suspected.

CONCLUSION

An interactive field assessment of a programmatic tool revealed the value of a systematic outbreak response plan with a standard definition of a tuberculosis outbreak, guidelines for communication and evaluation, and response steps. The assessment highlighted the importance of education and training for tuberculosis in low-incidence areas.

A threshold value for the time delay to TB diagnosis

BACKGROUND

In many communities where TB occurs at high incidence, the major force driving the epidemic is transmission. It is plausible that the typical long delay from the onset of infectious disease to diagnosis and commencement of treatment is almost certainly the major factor contributing to the high rate of transmission.

METHODOLOGY/PRINCIPAL FINDINGS

This study is confined to communities which are epidemiologically relatively isolated and which have low HIV incidence. The consequences of delays to diagnosis are analyzed and the existence of a threshold delay value is demonstrated. It is shown that unless a sufficient number of cases are detected before this threshold, the epidemic will escalate. The method used for the analysis avoids the standard computer integration of systems of differential equations since the intention is to present a line of reasoning that reveals the essential dynamics of an epidemic in an intuitively clear way that is nevertheless quantitatively realistic.

CONCLUSIONS/SIGNIFICANCE

The analysis presented here shows that typical delays to diagnosis present a major obstacle to the control of a TB epidemic. Control can be achieved by optimizing the rapid identification of TB cases together with measures to increase the threshold value. A calculated and aggressive program is therefore necessary in order to bring about a reduction in the prevalence of TB in a community by decreasing the time to diagnosis in all its ramifications. Intervention strategies to increase the threshold value relative to the time to diagnosis and which thereby decrease disease incidence are discussed.

The perils of public transport

Section 33 of The Public Health (Control of Disease) Act 1984 makes it an offence for a person in England and Wales who is suffering from a notifiable disease, e.g. cholera, to use any bus, tram or train; or use a taxi without notifying the driver or owner of the vehicle, or their carer to allow them to do so. Section 34 of the same act prohibits the owner, driver or conductor of a bus, train or tram from carrying a person who he knows is suffering from one of these diseases However, a taxi can carry an affected person, provided this individual pays a sum in addition to the fare to cover the costs of disinfection. Assuming that the owner or driver did not know that a passenger was suffering from one of these diseases, he must inform the local authority, which is required to disinfect the taxi for free. A literature review using PubMed did not reveal any evidence that buses, trains, trams or taxis provide a significant vehicle for transmission of notifiable diseases. Is it therefore about time that a non-evidence-based and little-used law is removed from the British statute books?

Balancing prevention and screening among international migrants with tuberculosis: Population mobility as the major epidemiological influence in low-incidence nations

BACKGROUND

Tuberculosis infection and disease remain a significant cause of global morbidity and mortality. The burden of tuberculosis disease is greatest in the developing nations of the world, although the effect of imported disease is observed in low-incidence tuberculosis regions, represented predominantly by high-income countries. In these regions, national tuberculosis control and elimination programmes are increasingly challenged to address disease in foreign-born residents. Immigration policies and shifting migration patterns over the past 5 decades have brought larger numbers of permanent and temporary residency migrants from high-prevalence regions of the world into low tuberculosis incidence environments. As a consequence, both national immigration policies and global health strategies for the control of tuberculosis share common interest in mobile populations moving from high-to-low prevalence regions. Existing immigration medical screening practices in major immigrant-receiving nations were often designed to prevent and manage the importation of contagious, active pulmonary tuberculosis disease. Such programmes may be limited in addressing the long-term consequences of latent tuberculosis infection in foreign-born residents. In nations with a low incidence of tuberculosis, a direct link can be found between the globalization of health factors related to international population movements, as observed with tuberculosis and immigration policies and practices. Continued migration from high-endemic tuberculosis regions will increasingly influence the disease burden in low-endemic areas, and challenge local tuberculosis control and elimination programmes. Evidence-based approaches to meeting those challenges will allow for the effective use of resources and support ongoing programme evaluation.

A tuberculosis outbreak in a private-home family child care center in San Francisco, 2002 to 2004

BACKGROUND

Child care facilities are well known as sites of infectious disease transmission, and California child care facility licensure requirements include annual tuberculosis (TB) screening for on-site adults. In April 2004, we detected an adult with TB living in a private-home family child care center (child care center A).

METHODS

We reviewed patient medical records and conducted a contact investigation. The investigation included all persons at the child care center, the workplace and leisure contacts of the adult patient with TB, and the household contacts of secondary case patients. Contact names were obtained through patient interviews. A positive tuberculin skin test result was defined as induration of > or =5 mm. DNA fingerprints of Mycobacterium tuberculosis isolates were analyzed. Outbreak cases were those that had matching DNA fingerprint patterns or were linked epidemiologically, if DNA fingerprint results were not available.

RESULTS

Between August 2002 and July 2004, we detected 11 outbreak cases, including 9 (82%) among children (<18 years of age). All 11 outbreak patients lived or were cared for at child care center A. The 9 pediatric TB patients were young (<7 years of age), United States-born children of foreign-born parents, and 4 (44%) had positive cultures for M tuberculosis. Including isolates recovered from the 2 adult patients, all 6 M tuberculosis isolates shared identical, 7-band, DNA fingerprint patterns. The contact investigation identified 3 (33%) of the 9 pediatric cases; 2 (22%) presented with illness and 4 (44%) were detected by primary care providers during routine TB screening. Excluding case subjects, 36 (54%) of 67 named contacts had latent TB infection.

CONCLUSIONS

Provider adherence to locally adapted pediatric TB screening recommendations proved critical to outbreak control. TB screening compliance by the child care center and more aggressive source-case investigation by the TB program might have prevented or abated this large pediatric TB outbreak.

Tuberculosis in children: an update

TB is a common and serious global infection that is spread exclusively from person to person. The initial infection in most healthy people leads to LTBI 95% of the time, but untreated individuals have a 5% to 10% lifetime risk for reactivating their infection to develop highly infectious cavitary pulmonary TB or extrapulmonary disease. Following primary infection progressive disease is more likely to develop in children younger than 5 years old or those who are immunocompromised, particularly those with HIV infection. The diagnosis of TB in most of the world depends on the presence of a clinical illness typical for TB in concert with radiographic changes, the presence of AFB in sputum, or a positive TST. Newer methods of in vitro stimulation of T lymphocytes from TB-infected people to produce interferon may be more accurate than a TST but have yet to be well studied in children. Treatment of children with LTBI is generally 9 months of daily isoniazid unless the child has been in contact with an adult with known isoniazid-resistant TB. For active TB, children generally are treated for 6 months with an initial 2 months of isoniazid, rifampin, and pyrazinamide. Where exposure to an isoniazid-resistant strain is likely, ethambutol is added. After 2 months, pyrazinamide is discontinued unless the patient has been confirmed to have been infected with a resistant strain of M. tuberculosis. BCG, rarely used in the United States, is still considered important to prevent meningitis and miliary disease in very young children in areas of the world with a high prevalence of TB.

Mycobacterium tuberculosis growth control by lung macrophages and CD8 cells from patient contacts

RATIONALE

Healthy household contacts (HHCs) of patients with active pulmonary tuberculosis are exposed aerogenically to Mycobacterium tuberculosis (Mtb), thus permitting the study of protective local immunity.

OBJECTIVES

To assess alveolar macrophage (AM) and autologous blood CD4 and CD8 T-cell-mediated Mtb growth control in HHCs and healthy, unexposed community control subjects (CCs).

METHODS

AMs were infected with Mtb strains H(37)Ra and H(37)Rv at multiplicities of infection 0.1 and 1. Mtb colony-forming units were evaluated on Days 1, 4, and 7.

MAIN RESULTS

CD8 T cells from HHCs in 1:1 cocultures with AMs significantly (p < 0.05) increased Mtb growth control by AMs. In CCs, no detectable contribution of CD8 T cells to Mtb growth control was observed. CD4 T cells did not increase Mtb growth control in HHCs or in CCs. IFN-gamma, nitric oxide, and tumor necrosis factor were determined as potential mediators of Mtb growth control in AMs and AM/CD8 and AM/CD4 cocultures. IFN-gamma production in AM/CD4 was twofold higher than that in AM/CD8 cocultures in both HHCs and CCs (p < 0.05). Nitric oxide production from AMs of HHCs increased on Days 4 and 7 and was undetectable in AMs from CCs. IFN-gamma and nitric acid concentrations and Mtb growth control were not correlated. Tumor necrosis factor levels were significantly increased in AM/CD8 cocultures from HHCs compared with AM/CD8 cocultures from CCs (p < 0.05).

CONCLUSION

Aerogenic exposure to Mtb in HHCs leads to expansion of Mtb-specific effector CD8 T cells that limit Mtb growth in autologous AMs.

Identification ofMycobacteriumtuberculosisH37Rv Integral Membrane Proteins by One-Dimensional Gel Electrophoresis and Liquid Chromatography Electrospray Ionization Tandem Mass Spectrometry

Because many membrane-associated proteins represent potential drug targets, diagnostic probes, and components of vaccines, we have chosen to study the membrane proteins of Mycobacterium tuberculosis H37Rv. To remove cytosolic proteins and facilitate access to the integral membrane proteins, membrane fractions of M. tuberculosis H37Rv were intensely washed with 5 M urea and high pH carbonate solution. One-dimensional SDS-PAGE, followed by enzymatic hydrolysis and nanoLC electrospray ionization MS/MS, proved to be the most efficient way to identify the proteins contained within the membrane fraction. Here we report 349 protein identifications in total, validated by at least two tryptic peptide matches and MOWSE scores greater than 75. Of those 349 proteins, 100 are integral membrane proteins with at least one predicted transmembrane alpha helix (excluding the possible signal sequence). 84 M. tuberculosis H37Rv proteins, including 42 integral membrane proteins, are described for the first time.