Kathleen Moser

Tuberculosis from Mycobacterium bovis in Binational Communities, United States

The epidemiology of tuberculosis (TB) in the United States is changing as the incidence of disease becomes more concentrated in foreign-born persons. Mycobacterium bovis appears to be contributing substantially to the TB incidence in some binational communities with ties to Mexico. We conducted a retrospective analysis of TB case surveillance data from the San Diego, California, region from 1994 through 2005 to estimate incidence trends, identify correlates of M. bovis disease, and evaluate risk factors for deaths during treatment. M. bovis accounted for 45% (62/138) of all culture-positive TB cases in children (<15 years of age) and 6% (203/3,153) of adult cases. M. bovis incidence increased significantly (p = 0.002) while M. tuberculosis incidence declined (p<0.001). Almost all M. bovis cases from 2001 through 2005 were in persons of Hispanic ethnicity. Persons with M. bovis were 2.55x (p = 0.01) as likely to die during treatment than those with M. tuberculosis.

Tracing the origins of Mycobacterium bovis tuberculosis in humans in the USA to cattle in Mexico using spoligotyping

OBJECTIVES To compare genotypes of Mycobacterium bovis strains from humans in Southern California with genotypes of M. bovis strains in cattle in Mexico and the USA to explore the possible origins of human infections. METHODS We conducted a descriptive analysis of M. bovis genotypes from a binational population of humans and cattle using spacer oligonucleotide typing (spoligotyping). RESULTS One hundred six human M. bovis spoligotypes were compared to spoligotypes from 496 Mexican cattle and 219 US cattle. Twelve spoligotype patterns were identified among human cases and 126 spoligotype patterns were detected in cattle. Over 91% (97/106) of the human M. bovis isolates had spoligotypes that were identical to those found in Mexican cattle. Four human cases had spoligotypes that matched both cattle born in Mexico and in the USA. Nine human cases had spoligotypes that did not match cattle born in Mexico or the USA. CONCLUSIONS Our data indicate that the population of M. bovis strains causing human TB disease in Southern California is closely related to the M. bovis strain population found in Mexican cattle and supports existing epidemiological evidence that human M. bovis disease in San Diego likely originated from Mexican cattle.

Predictors of adherence to treatment for latent tuberculosis infection in high-risk Latino adolescents: a behavioral epidemiological analysis

The objective was to test whether theoretical variables predict adherence to treatment for latent tuberculosis infection in high-risk Latino adolescents. 286 Latino adolescents, age 13-18 years, were recruited from 10 middle/high schools in San Diego County, San Diego, USA. Participants completed a baseline interview and up to 9 monthly interviews. The cumulative number of pills consumed in 9 months was regressed on 16 independent variables, entered hierarchically in seven blocks. The final model accounted for 25% of the variance in adherence to isoniazid (INH), F (16, 230)=4.69, p<0.001. Adherence counseling (+), age (-), grades (+), being bicultural (+), and risk behaviors (-) were significantly related to adherence. Learning theories presume that adherence to medical regimens requires social support and freedom from physical and social barriers. Results support these theories. Future studies should explore additional precepts in order to identify additional predictors and to maximize adherence to INH among Latino adolescents and other high-risk populations. Doing so should decrease the risk of active TB among high-risk racial/ethnic and foreign-born populations.

Latent Tuberculosis among Persons at Risk for Infection with HIV, Tijuana, Mexico

Interventions that prevent HIV transmission and TB reactivation are needed.

Influences of Cross-Border Mobility on Tuberculosis Diagnoses and Treatment Interruption Among Injection Drug Users in Tijuana, Mexico

OBJECTIVES We sought to identify correlates of reported lifetime diagnoses of TB among injection drug users in the border city of Tijuana, Mexico. METHODS Injection drug users in Tijuana were recruited into a prospective cohort study during 2006 and 2007. We used weighted multivariate logistic regression to identify correlates of TB diagnoses. RESULTS Of the 1056 participants, 103 (9.8%) reported a history of TB, among whom 93% received anti-TB medication and 80% were diagnosed in the United States. Treatment was prematurely halted among 8% of patients; deportation from the United States was the cause of half of these treatment interruptions. History of travel to (odds ratio [OR] = 6.44; 95% confidence interval [CI] = 1.53, 27.20) or deportation from (OR = 1.83; 95% CI = 1.07, 3.12) the United States and incarceration (OR = 2.20; 95% CI = 1.06, 4.58) were independently associated with a reported lifetime diagnosis of TB. CONCLUSIONS Mobility and migration are important factors in identifying and treating TB patients diagnosed in the US-Mexico border region. Strengthening capacity on both sides of the border to identify, monitor, and treat TB is a priority.

Tuberculosis screening among foreign-born persons applying for permanent US residence.

OBJECTIVES This study sought to determine adherence of physicians to tuberculosis (TB) screening guidelines among foreign-born persons living in the United States who were applying for permanent residency. METHODS Medical forms of applicants from 5 geographic areas were reviewed, along with information from a national physician database on attending physicians. Applicant and corresponding physician characteristics were compared among those who were and were not correctly screened. RESULTS Of 5739 applicants eligible for screening via tuberculin skin test, 75% were appropriately screened. Except in San Diego, where 11% of the applicants received no screening, most of the inappropriate screening resulted from the use of chest x-rays as the initial screening tool. CONCLUSIONS Focused physician education and periodic monitoring of adherence to screening guidelines are warranted.

HIV–Tuberculosis Coinfection in Southern California: Evaluating Disparities in Disease Burden

OBJECTIVES We sought to understand tuberculosis (TB) and HIV coinfection trends in San Diego County, California, and to identify associations between sociodemographic risk factors and TB and HIV coinfection. METHODS We analyzed TB surveillance data from 1993 through 2007. TB cases were grouped by HIV status: positive, negative, or unknown. We used Poisson regression to estimate trends and tested associations between TB and HIV coinfection and sociodemographic risk factors with polychotomous logistic regression. RESULTS Of 5172 TB cases, 8.8% were also infected with HIV. Incidence of coinfected cases did not change significantly over the period studied, but the proportion of cases among Hispanics increased significantly, whereas cases among non-Hispanic Whites and Blacks decreased. TB cases with HIV coinfection were significantly more likely to be Hispanic, male, injection drugs users, and aged 30 to 49 years, relative to cases with TB disease only. CONCLUSIONS The burden of TB and HIV in San Diego has shifted to Hispanics in the last decade. To address this health disparity, binational TB and HIV prevention efforts are needed.

Urine testing to monitor adherence to TB preventive therapy

This study examined the validity of the Arkansas urine test. One hundred ninety-four adolescents submitted an unannounced urine specimen monthly (for 6 to 8 months). Duplicate specimens were blindly tested with high agreement (kappa >90%). Sensitivity and specificity were estimated. In 68% of test runs, adolescents recalled taking INH within 24 hr of specimen collection. For recall intervals of 24, 48, and 72 hr, sensitivity was 87, 85, and 83%, respectively. Females were less likely to test positive when INH was taken within the previous 24 hr (sensitivity 84 versus 92% males). Specificity was 57, 91, and 95% at 24, 48, and 72 hr, respectively. The Arkansas urine test was practical to use, and results correlated well with self-reported adherence to INH for treatment of latent tuberculosis infection (LTBI), over several months of follow-up. The test may be useful as part of an adherence-monitoring program when used in conjunction with self-reported measures.

Prevalence and Treatment of Latent Tuberculosis Infection Among Newly Arrived Refugees in San Diego County, January 2010–October 2012

OBJECTIVES We determined the prevalence and treatment rates of latent tuberculosis infection (LTBI) in newly arrived refugees in San Diego County, California, and assessed demographic and clinical characteristics associated with these outcomes. METHODS We analyzed data from LTBI screening results of 4280 refugees resettled in San Diego County between January 2010 and October 2012. Using multivariate logistic regression, we calculated the associations between demographic and clinical risk factors and the outcomes of LTBI diagnosis and LTBI treatment initiation. RESULTS The prevalence of LTBI was highest among refugees from sub-Saharan Africa (43%) and was associated with current smoking and having a clinical comorbidity that increases the risk for active tuberculosis. Although refugees from sub-Saharan Africa had the highest prevalence of infection, they were significantly less likely to initiate treatment than refugees from the Middle East. Refugees with postsecondary education were significantly more likely to initiate LTBI treatment. CONCLUSIONS Public health strategies are needed to increase treatment rates among high-risk refugees with LTBI. Particular attention is required among refugees from sub-Saharan Africa and those with less education.

Factors associated with genotype clustering of Mycobacterium tuberculosis isolates in an ethnically diverse region of southern California, United States

Mycobacterium tuberculosis (Mtb) isolates with identical genotypes, found in different patients, are most likely the result of recent transmission. Mtb strains with closely related genotypes, called clonal complexes, are most likely derived from one another. We examined Mtb genotypes from southern California TB patients from 2005 through 2008 to complete the first comprehensive molecular epidemiology analysis of this complicated and ethnically diverse region. Mtb genotypes were characterized with spoligotype and MIRU-12 typing. MIRU-VNTRplus was utilized to assign genotypes to global lineages and complete cluster analyses. Associations between patient characteristics and genotype clustering and clonal complexes were evaluated using logistic regression and frequency analysis. Of 832 Mtb isolates analyzed, 480 (58%) fell into 94 strain clusters. The majority of isolates were identified as being in the EA1 (31%), LAM (17%) and Haarlem (15%) lineages, but 13 different lineages were found in this region. TB patients with clustered isolates were more likely to be homeless (AOR 3.44, 95% CI 1.65, 7.18) and male (AOR 1.57, 95% CI 1.17, 2.10). Of the 480 clustered strains, 388 aggregated into six clonal complexes. Over 45% of reported TB cases were clustered and likely resulted from recent transmission events. Patients with clustered Mtb isolates that were grouped into clonal complexes had unique socio-demographic characteristics. These data suggest that TB is being transmitted in relatively insular community networks defined by race/ethnicity and country of origin. The addition of clonal complex analysis to simple cluster analysis provides important public health insights into the local transmission of TB in ethnically diverse regions with diverse Mtb genotypes.