PREVENTION OF NOSOCOMIAL TRANSMISSION OF MYCOBACTERIUM TUBERCULOSIS

doi:10.1016/S0891-5520(05)70362-7

Infectious Disease Clinics of North America

Volume 11, Issue 2, 1 June 1997, Pages 385-409

https://doi.org/10.1016/S0891-5520(05)70362-7 Get rights and content

Tuberculosis (TB) is a disease that is increasing in prevalence and is one of the leading causes of morbidity and mortality throughout the world; each year approximately 8 to 10 million persons acquire TB and 3 million persons die.44, 80, 107 Factors contributing to the worldwide increase in TB prevalence include the failure to aggressively identify and treat those with infectious TB, prevention of secondary transmission, and interaction between the human immunodeficiency virus (HIV) and TB epidemics.¹⁰¹ Approximately 7% of all deaths and 26% of preventable deaths in developing countries are caused by TB.70, 80 Worldwide, nearly 6 million persons are estimated to be coinfected with HIV and Mycobacterium tuberculosis.⁴⁴

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SECULAR TREND IN TUBERCULOSIS IN THE UNITED STATES

From 1953 through 1984, the number of persons in the United States each year with active TB decreased by approximately 6% per year from 84,304 to 22,201.³¹ From 1985 through 1992, however, the incidence of TB reversed its downward trend and, possibly secondary to the HIV epidemic and increased immigration from countries with a high incidence of TB, the reported number of persons with TB increased by approximately 20% to 26,673. During this period, an estimated 52,000 more persons developed TB

NOSOCOMIAL M. TUBERCULOSIS TRANSMISSION TO HEALTH CARE WORKERS

The combination of an increasing prevalence of TB, HIV, and MDR–TB resulted in an increase in hospitalization of persons with infectious TB and an increased risk for M. tuberculosis transmission to health care workers (occupational acquisition) in these facilities. Numerous institutional infection control and host factors influence whether M. tuberculosis will be transmitted in a health care facility (Table 1). In all nosocomial TB outbreaks, many if not most of these factors have facilitated

NOSOCOMIAL M. TUBERCULOSIS TRANSMISSION

Because there is no national reporting system for nosocomial M. tuberculosis outbreaks, our knowledge of such outbreaks is based on published reports. Before 1989, reports of nosocomial M. tuberculosis transmission were infrequent.4, 47, 57, 89 The infrequency of such reports may reflect either the rarity of nosocomial TB outbreaks or the failure to detect them. From 1960 through 1996, approximately 20 nosocomial TB outbreaks were reported in the United States*

RISK FACTORS FOR NOSOCOMIAL TRANSMISSION OF

M. TUBERCULOSIS

A wide variety of factors have facilitated patient-to-patient and patient-to–health care worker M. tuberculosis transmission. These included factors affecting the likelihood of exposure, the likelihood of infection given exposure, and the likelihood of active disease given infection (see Table 1). Patient risk factors identified included: having HIV or AIDS, recent (i.e., less than or equal to 1 month) admission to the outbreak hospital, close exposure or room proximity to AFB

MOLECULAR TYPING OF MDR–TB OUTBREAK

M. TUBERCULOSIS ISOLATES

A critical element in confirming the epidemiologic evidence of nosocomial M. tuberculosis transmission in each of the MDR–TB outbreak investigations was the use of molecular typing of the MDR–TB infecting strains to confirm the epidemiologic findings. Using restriction fragment length polymorphism (RFLP) analysis, which was developed in 1990 to type M. tuberculosis isolates, in most of the MDR–TB outbreaks, one or more unique strains were documented to be transmitted

EARLY IDENTIFICATION AND DIAGNOSIS OF INFECTIOUS TUBERCULOSIS PATIENTS

Community and hospital M. tuberculosis outbreaks have occurred among the homeless, seasonal workers, immigrants from countries with a high prevalence of TB, the elderly, injecting drug users, and persons in correctional facilities. To avoid future outbreaks, physicians must maintain a high index of suspicion for TB. Early identification of patients who may have infectious TB, prompt implementation of TB isolation precautions for such patients, prompt definitive diagnosis of TB, and prompt

MANAGEMENT OF SUSPECTED INFECTIOUS TUBERCULOSIS PATIENTS

The first point of contact of potentially M. tuberculosis–infected patients in health care facilities is the health care workers working in ambulatory care or emergency medicine settings. There have been reports of M. tuberculosis transmission in ambulatory care settings over the last 10 years; therefore, health care workers in these settings must be trained to quickly evaluate patients for the signs and symptoms suggestive of TB and triage potentially infectious patients to isolation areas.78,

CONTROL MEASURES FOR PREVENTION OF

M. TUBERCULOSIS TRANSMISSION IN HOSPITALS

Control of M. tuberculosis transmission in health care facilities is dependent on an understanding of and full implementation of guideline recommendations.²³ The exact control measures recommended are dependent on the risk each patient or health care worker has for exposure to an infectious TB patient.⁹² Thus, the first step in implementing a TB control program is to conduct a risk assessment to determine the risk for such exposures in the entire

TUBERCULOSIS INFECTION CONTROL PROGRAMS IN THE UNITED STATES

The sudden recognition and reporting of numerous nosocomial TB outbreaks raised concern that CDC TB Guideline recommendations might be inadequate in preventing M. tuberculosis transmission in US hospitals. In the early 1990s, several national surveys were conducted to assess the types of TB infection control programs implemented in US health care facilities. In 1992, the American Hospital Association (AHA) in collaboration with the CDC conducted a survey of all US municipal, veterans affairs,

BACILLUS CALMETTE-GUÉRIN VACCINATION OF HEALTH CARE WORKERS

The protective efficacy of BCG vaccine has been debated since it was recommended for use in preventing TB by the League of Nations-United Nations in 1928. Recently, two meta-analyses have attempted to calculate summary estimates of the vaccine's efficacy; however, these studies do not examine the efficacy of BCG in health care workers.37, 97 The second meta-analysis attempted to examine BCG efficacy in health care workers; however, the available studies lacked information on determination of

SUMMARY

The recent resurgence of TB together with the ongoing HIV epidemic has resulted in a larger number of infectious TB patients being admitted to US health care facilities. These patients have become a source for both nosocomial (patient-to-patient) and occupational (patient-to–health care worker) M. tuberculosis transmission. Infectious MDR–TB patients serve as even greater potential infectious sources because they often remain AFB smear and culture positive for months to years. The keys to the

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