Infection control basics to stop TB spread in hospitals

Infection control basics to stop TB spread in hospitals

Lessons from past will be needed if XDR emerges

If extensively drug-resistant tuberculosis (XDR-TB) emerges to become an infection control threat in the nation's hospitals, the lessons learned from past outbreaks will prove invaluable. In past nosocomial outbreaks of TB and multidrug-resistant MDR-TB, the majority of the patients and some infected health care workers were HIV-infected and progression to TB disease was rapid, the Centers for Disease Control and Prevention reports.¹

Factors contributing to these outbreaks included delayed diagnosis of TB disease, delayed initiation and inadequate airborne precautions, lapses in airborne infection isolation (AII) practices and precautions for cough-inducing and aerosol-generating procedures, and lack of adequate respiratory protection. Multiple studies suggest that the decline in health care-associated transmission observed in specific institutions is associated with the rigorous implementation of infection control measures. However, because various interventions were implemented simultaneously, the effectiveness of each intervention could not be determined, the CDC reports.

One of the most critical risks for health care-associated transmission of TB in health care settings is from patients with unrecognized TB disease who are not promptly handled with appropriate airborne precautions or who are moved from an AII room too soon. All health care settings need a TB infection control program based on a three-level hierarchy of controls, including administrative, environmental, and respiratory protection.

Administrative Controls: The first and most important level of TB control is the use of administrative measures to reduce the risk for exposure to people who might have TB disease. Administrative controls consist of the following activities:

• assigning responsibility for TB infection control in the setting;
• conducting a TB risk assessment of the setting;
• developing and instituting a written TB infection control plan to ensure prompt detection, airborne precautions, and treatment of people who have suspected or confirmed TB disease;
• ensuring the timely availability of recommended laboratory processing, testing, and reporting of results to the ordering physician and infection control team;
• implementing effective work practices for the management of patients with suspected or confirmed TB disease;
• ensuring proper cleaning and sterilization or disinfection of potentially contaminated equipment (usually endoscopes);
• training and educating HCWs regarding TB, with specific focus on prevention, transmission, and symptoms;
• screening and evaluating HCWs who are at risk for TB disease or who might be exposed to M. tuberculosis (i.e., TB screening program);
• applying epidemiologic-based prevention principles, including the use of setting-related infection control data;
• using appropriate signage advising respiratory hygiene and cough etiquette;
• coordinating efforts with the local or state health department.

Environmental Controls: The second level of the hierarchy is the use of environmental controls to prevent the spread and reduce the concentration of infectious droplet nuclei in ambient air. Primary environmental controls consist of controlling the source of infection by using local exhaust ventilation (e.g., hoods, tents, or booths) and diluting and removing contaminated air by using general ventilation. Secondary environmental controls consist of controlling the airflow to prevent contamination of air in areas adjacent to the source (AII rooms) and cleaning the air by using high-efficiency particulate air (HEPA), filtration, or UVGI.

Respiratory-Protection Controls: The first two control levels minimize the number of areas in which exposure to M. tuberculosis might occur and, therefore, minimize the number of people exposed. These control levels also reduce, but do not eliminate, the risk for exposure in the limited areas in which exposure can still occur. Because people entering these areas might be exposed to M. tuberculosis, the third level of the hierarchy is the use of respiratory protective equipment in situations that pose a high risk for exposure. Use of respiratory protection can further reduce risk for exposure of HCWs to infectious droplet nuclei that have been expelled into the air from a patient with infectious TB disease (see Respiratory Protection). The following measures can be taken to reduce the risk for exposure:

• implementing a respiratory protection program;
• training HCWs on respiratory protection;
• training patients on respiratory hygiene and cough etiquette procedures.

Reference

1. Centers for Disease Control and Prevention. Guidelines for Preventing the Transmission of Mycobacterium tuberculosis in Health-Care Settings, 2005. MMWR 2005; 54(RR17):1-141.