The CDC Epidemic Intelligence Service Takes Aim at Tuberculosis at Recent Conference

One-third of the world’s population is infected with tuberculosis (TB) and it’s one of the world’s deadliest diseases, according to the Centers for Disease Control and Prevention (CDC). Officers of the CDC’s Epidemic Intelligence Service (EIS) presented recent research on TB on May 3 in a session at the 65th Annual Epidemic Intelligence Service (EIS) Conference in Atlanta, Georgia. A summary of the presentations is included below:

Between August 2012 and July 2015, Dr. Diya Surie, MD, and her team of researchers identified 25 TB patients with matching TB genotype and drug susceptibility pattern in Gaborone, Botswana, suggesting recent transmission of this TB strain. Eleven patients had received care at the same hospital and the researchers investigated epidemiologic links between patients to determine the extent of nosocomial transmission and to identify potential transmission hotspots in the community.

“Being able to identify where TB transmission is occurring in endemic settings is of great value to national TB programs that have limited budgets for active case finding of TB disease. This approach is an exploration of whether genotyping can help identify locations within cities where TB transmission may be happening in endemic settings.” Dr. Surie told Contagion™ in an in-person interview.

The researchers interviewed patients to find common contacts, workplaces, and sites of social gathering. In addition, they reviewed dates of hospital visits and mapped primary residences. They found epidemiologic links, including overlapping hospital visits; living within 1 kilometer of another patient; frequenting the same locations as another patient; or naming another patient as a contact.

“We were initially thinking that because almost half of the cases in this TB cluster had received care at one particular hospital, the hospital would be the source of TB transmission. But, most TB transmission actually appeared to be occurring in the community. That was a surprising finding for us,” Dr. Surie said.

Epidemiologic links might have accounted for transmission at the hospital between only two patients. Recent community transmission was possible among 20 (95%) of 21 interviewed patients; 16 (76%) were linked to another patient by the same minibus route; 12 (57%) lived within 1 kilometer of another patient; 11 (52%) visited the same bar as at least one other patient; 8 (38%) attended the same church as at least one other patient; and 6 (29%) named each other as a contact.

Colleen Scott, PhD, and colleagues found that inherent resistance to pyrazinamide in Mycobacterium bovis TB cases did not lengthen the time to culture conversion among patients receiving standard treatment, and they suggest further in vitro studies to investigate the intrinsic differences in treatment response between M. bovis and M. tuberculosis.

“The most salient finding of our study is that M. bovis culture converted sputum cultures faster than M. tuberculosis. The difference between the two species was unexpected,” said Dr. Scott in an in-person interview.

Pyrazinamide shortens standard TB treatment, so current guidelines recommend longer treatment for TB due to pyrazinamide-resistant organisms, such as M. bovis. The authors compared treatment response times of 290 M. bovis and 30,572 M. tuberculosis culture-positive, pulmonary TB cases reported to the National Tuberculosis Surveillance System from 2006 through 2013.

The authors found that after being treated for two months, 72% of M. bovis and 65% of M. tuberculosis patients converted sputum culture to negative (P=0.0025), and M. bovis patients were more likely to convert to negative culture (adjusted hazard ratio 1.2; 95% confidence interval, 1.1 to 1.4).

Jacklyn Wong, PhD, and her group studied immigrants and refugees in California whose chest radiographs indicated TB before their arrival in the United States. They found that immigrants with previous TB had 8-fold higher TB incidence than the general California population, and they advised prioritizing these patients for evaluation and treatment.

The authors retrospectively examined a cohort of immigrants and refugees 15 years of age and older with chest radiographs conducted overseas that indicated TB. Those individuals who were studied had arrived in California between 1999 and 2012 and were classified into 1 of 3 groups: previous TB, latent TB infection, or no documented infection.

Of 35,613 arrivers, 20,187 (56.7%) had previous TB; 7,124 (20.0%) had latent TB infection; and 8,302 (23.3%) had no documented infection; overall, 102 arrivers developed active TB, with rates of 52.7, 28.8, and 22.0 cases/100,000 person-years among those with previous TB, latent TB infection and no documented infection, respectively.

Jorge L. Salinas, MD and his co-authors used surveillance data for multidrug-resistant tuberculosis (MDR TB) patients in California, Florida, Texas, and New York City between 2000 and 2007, and found that older age, previous TB disease, and excessive alcohol use were risk factors for poor outcomes and that directly observed therapy (DOT) was protective. They recommend maximizing DOT coverage to help reduce poor outcomes.

The median age of the 526 MDR TB patients in the study was 38; 100 patients (19%) had previous TB, and 60 (11%) reported excessive alcohol use. Of 493 (94%) patients with available data, 462 (94%) were given DOT; and 96 (18%) of 526 patients had poor outcomes, including 35 deaths and 61 treatment non-completions.

Lorraine L. Janeczko, MPH, is a medical science writer who creates news, continuing medical education and feature content in a wide range of specialties for clinicians, researchers and other readers. She has completed a Master of Public Health degree through the Department of Epidemiology of the Johns Hopkins Bloomberg School of Public Health and a Dana Postdoctoral Fellowship in Preventive Public Health Ophthalmology from the Wilmer Eye Institute, the Johns Hopkins University School of Medicine and the Bloomberg School.

SOURCE: EIS 2016 Conference Program, pp 40-42: Concurrent Session C2: Influenza

Studies Presented:

Diya Surie, MD, EIS officer in the Center for Global Health, Tuberculosis Hotspots: Cluster of Cases with Matching Mycobacterium tuberculosis Genotype — Gaborone, Botswana, 2012—2015

Colleen Scott, PhD, EIS officer, Center for Global Health, A Comparison of Treatment Response Time between Mycobacterium bovis and Mycobacterium tuberculosis Disease

Jacklyn Wong, EIS fellow, Office of Public Health Scientific Services, Progression to Active Tuberculosis Among Immigrants and Refugees with Abnormal Chest Radiographs Conducted Overseas — California, 1999—2012

Jorge L. Salinas, MD, EIS officer, Office of Infectious Diseases, Factors Associated with Poor Outcomes Among Patients with Multidrug-Resistant Tuberculosis — Four U.S. Sites, 2000—2007