Research for infection protection

Infection protection in case of tuberculosis

Besides HIV/AIDS and malaria, tuberculosis (TB) is one of the most common infectious diseases worldwide. Although the number of new TB infections throughout the world decreases by 1.5 per cent per year [1], in 2014 around 1.5 million people died from TB – often due to inadequate treatment. People infected with HIV are particularly vulnerable to TB. One third of those infected with HIV die from this bacterial infection which normally can be treated [2].


Transmission, symptoms, course of the disease

Causative agent of TB infections is the Mycobacterium tuberculosis. The bacterium is almost exclusively transmitted through the air and only from human to human. Particularly when sneezing or coughing, infected people release smallest droplets (diameter < 5 µm) carrying the pathogen, which are then inhaled by other people. Normally, only patients with open (pulmonary-positive) tuberculosis pose a risk of infection: in this case the focus of the disease has access to the respiratory tract through which the pathogen can reach the environment [2, 3].

On average, the incubation period is six to eight weeks after infection. However, only between five and ten per cent of those infected develop a tuberculosis that needs to be treated. In the remaining cases, the body is able to combat the mycobacteria and contain the infection permanently (latent tuberculosis infection, LTBI) [3]. Whether TB is transmitted depends on the extent (closeness, frequency and length) of the contact to TB patients. Also, the amount and virulence (extent of the pathogenicity) of the pathogen as well as the immune defence of the contact person plays a role.

In principle, TB can affect every organ. In most cases, however, it affects the lung. If symptoms occur, they mostly include coughing with or without bloody sputum. Occasionally, infected people complain about chest pain and shortness of breath. Further tuberculosis symptoms include fatigue, weight loss, general weakness and are similar to those of an influenza infection [4].

Multidrug-resistant tuberculosis MDR-TB and XDR-TB

According to WHO data, a total of 480 000 people contracted multidrug-resistant tuberculosis (MDR-TB) in 2014. The pathogens of an MDR-TB are resistant to two or more first-line tuberculostatic agents, such as isoniazid and rifampicin. Are the TB pathogens resistant to all first-line tuberculostatic agents and, additionally, to second-line tuberculostatic agents one speaks of XDR-TB (extensively drug-resistant tuberculosis). According to WHO estimates, 9.7 per cent of the new MDR-TB cases in 2014 involved XDR-TB [2, 5].

Isolation measures and room ventilation

Isolation rooms of TB patients should have own bathrooms. Infected persons should have single rooms and be urged to not leave the room if possible. In case the room is left, a face mask should be used [3].
To prevent the spread of TB pathogens to other hospital areas through the air, it is essential to ventilate the isolation room adequately. The air should be exchanged at least 12 times per hour [6]. Ideally, the outgoing air of ventilation systems is given off to the outside [6]. In case the air is circulated, high-efficiency particulate arrestance (HEPA) filters are to be used. In principal, the isolation room needs to have a negative pressure, which is to be checked every day [3].


PPE and face mask

When entering isolation rooms that accommodate contagious tuberculosis patients, face masks with a filter efficiency > 95 per cent should always be worn. The particle-filtering half masks protect visitors and staff against inhaling the pathogenic aerosols. It has to be made sure that the masks fit accurately. For some therapeutic or diagnostic measures such as bronchoscopies it is recommended to use a higher face mask and possibly also a protection against splashed of secretion [3].


Hand and surface disinfection

Hand disinfection is to be carried out following the WHO’s 5 Moments.
As TB is transmitted through the air, surfaces are disinfected as is usual. In case the room is occupied, staff should wear a face mask when disinfecting and cleaning the room. However, during the final disinfection after the patient got discharged, no PPE is necessary in case the room was ventilated adequately [3].


Sources:
[1] World Health Organization. Global tuberculosis report 2015.
[2] World Health Organization. WHO – tuberculosis Fact sheet No. 104.
[3] Robert Koch-Institut. RKI-Ratgeber für Ärzte. Tuberkulose. Stand: Januar 2013.    
[4] R. Ziegler, H-M. Just, S. Castell et al. Infektionsprävention bei Tuberkulose -Empfehlungen des DZK. In: Pneumologie 2012; 66: 269 – 282. Stand: 31.1.2012.
[5] World Health Organization. Drug-resistant TB: XDR-TB FAQ.  
[6] Centers for Disease Control and Prevention. Tuberculosis Infection Control, Core Curriculum on Tuberculosis: What the Clinician Should Know