Resource Packages: Tuberculosis

Historical Overview 

Tuberculosis is a disease that has had an interesting history.  It has been referred to as the “White Death” and mankind has certainly had good reason to dread this affliction also known as “Captain of all the men of death”, as it has and continues to be a disease that causes significant morbidity and mortality.

In 1882 Robert Koch announced the first isolation of the tubercle bacillus. Intensive studies unmasked the pathogenesis and epidemiological characteristics of the disease.  In the ensuing century the further advances of tuberculin (Mantoux) skin testing, BCG, mass miniature radiography and anti-tuberculosis chemotherapy succeeded sanatorium regimes as effective management measures.

In 1906 two French bacteriologists, Calmette and Guerin, attempted to produce a vaccine.  After many years they succeeded in making the organism non-virulent, and it is now used for immunisation throughout the world.  BCG stands for “Bacillus of Calmette and Guerin".

Tuberculosis is caused by the Mycobacterium tuberculosis (M. TB) organism.  This is an acid-fast aerobic bacterium.

Recent Developments 

Transmission of tuberculosis is most commonly due to exposure to bacilli in airborne droplets from bronchial excretions or sputum of persons with infectious tuberculosis.

Transmission of infection is more likely to occur in poorly ventilated and overcrowded conditions, and infection of family contacts is the most common.

Contact need not necessarily be prolonged or close.  Transmission by indirect contact through contaminated articles is extremely rare, as is direct invasion through mucous membranes or breaks in the skin.

The disease remains communicable as long as infectious tubercle bacilli are being discharged.  Some untreated or inadequately treated patients may be intermittently sputum-positive for years.  The degree of communicability depends on the number of bacilli discharged, the virulence of the bacilli, opportunities for their dispersion by coughing, sneezing or singing and the susceptibility of contacts.

The lungs are the most common sites for TB.  In untreated pulmonary TB, the TB organisms multiply, stimulating the immune system to activate the cytotoxic lymphocyte macrophages.  As they ingest the TB organisms, these lymphocytes emit toxins that liquefy and destroy lung tissue.  This immune response results in the formation of cavities.

TB is not exclusively a pulmonary disease; it is a systemic disease that can affect any organ or tissue.  Extrapulmonary forms of TB, involving the lymphatic or central nervous system, or miliary (disseminated) TB are most often seen in HIV related TB.

Appropriate antimicrobial therapy reduces communicability within a few weeks.

Extrapulmonary TB is not infectious if enclosed.  There is a risk of transmission in the presence of a tuberculous discharge.

TB should be suspected in any patient with certain key respiratory signs and symptoms that have lasted for more than 3 weeks, eg persistent cough, haemoptysis, or hoarseness as well as fever, chills, night sweats, anorexia and unexplained weight loss.

The primary screening tool for TB is the tuberculin skin test (Mantoux), followed by posterior-anterior chest X-rays.  Sputum specimens can help confirm active TB and help estimate the degree of infectiousness.  Initially 3 sputum specimens should be collected and examined by smear and culture.  The smear test can detect mycobacterial organisms but provides only presumptive diagnosis because AFB (acid fast bacilli) may be nontuberculous mycobacteria.  Culture testing takes much longer, from 2 to 12 weeks.

If hospitalised or in an outpatient facility, people with direct sputum smear positive TB should be treated with appropriate anti-TB drugs in a single room for at least two weeks.

Treatment Regimes

Compared with other infectious diseases, treatment for TB is lengthy - typically 6-9 months and sometimes longer.  If treatment is not continued for a long enough period of time, some of the TB organisms will survive and the patient will be at risk of a relapse.

Treatment regimes now involve multiple drugs to which the organisms are susceptible.  If only one drug is given, the patient may become resistant to it.  When two or more drugs are used, each helps prevent the emergence of organisms resistant to the other.

There are a number of possible drug combinations and administrative schedules. Treatment for persons without known drug resistance or HIV infection usually lasts 6 months.  For the first 2 months, the patient takes four drugs - isoniazid (INH) rifampicin, pyrazinamide, ethambutol and pyridoxine (Vitamin B6) for the last 4 months usually just isoniazid and rifampicin.  These are all known as First Line Drugs.  The initial regime is usually administered daily for the first 2-4 weeks, after that the patient may be on intermittent therapy, often 3 times a week.

If a patient with active TB caused by organisms that are resistant to first line drugs then Second Line Drugs would be considered. These drugs are Cycloserine, Ethionamide and Para-amino-salicylate (PAS).  These drugs may be toxic so the patient requires closer monitoring.

Active TB in HIV positive and other immunocompromised people should be treated with conventional medications but for 3 months longer than the usual regime.

Children should receive the very highest priority because they are at greater risk for developing active disease after infection; also children are more likely to develop more serious forms of the disease such as miliary and meningeal TB.

Standard precautions should be practiced at all times, especially when handling sputum.

Airborne precautions will be used for the above patients.  Ideally the patient should be nursed in a negative pressure room but if these rooms are unavailable then the patient should be nursed in a single room with the door closed at all times. The room should be kept vacant for one hour post discharge of the patient.

Teach the patient to cover nose and mouth when coughing and sneezing.

Health care workers (HCW) and visitors entering the room must wear a recommended particulate mask.

When in transport the patient must wear a recommended particulate mask and areas receiving the patient should be notified of infectious status.

Incubation period - from infection to demonstrable primary lesion or significant tuberculin reaction, about 4-12 weeks.  While the subsequent risk of progressive pulmonary or extrapulmonary TB is greatest within the first year or two after infection, it may persist for a lifetime.

Notification to the Public Health Unit - Tuberculosis is a notifiable disease to the Public Health Unit.  Contact tracing would be organised by the PHUs and the local Chest Clinics.

Protection of health care workers - Policy for TB control among health care workers should be uniform throughout NSW.  health care workers should carry a personal record of BCG vaccination and results of employment related screening from one employment to another.

All medical, nursing, pathology, radiology and paramedical hospital staff should:

• Receive a Mantoux test on employment unless there is documentation of a positive Mantoux  test, adequate treatment for disease or infection, or a negative Mantoux test  within the previous three months
• Be offered BCG vaccination if Mantoux negative

Routine chest X-rays are not recommended for asymptomatic, Mantoux-negative health care workers.

There has been a marked increase in the incidence of TB due to immigrants, homeless persons and persons with HIV, which has had significant impact on hospitals and other healthcare facilities.

This increase has resulted in the document Controlling Tuberculosis in New South Wales. This document addresses four major methods of TB control: disease containment, case prevention, surveillance and program evaluation.

References

Benenson AS ed, 15th ed,1990, Control Of Communicable Diseases In Man. American Public Health Association, Washington.

Bennett, Brahman, Sandford, JP eds, 1992 3rd edition, Hospital Infections. Little, Brown and Company, Boston.

Boutotte J, 1993, T.B. The Second Time Around.  Nursing 93, May, Boston.

NSW Health Department, 1994, Tuberculosis And HIV, 94/99, AIDS/Infectious Diseases Branch.

NSW Health Department, 1994, Infection Control.  94 /87, AIDS/Infectious Diseases Branch.

NSW Health Department. 1998. Infection Control Policy 99/87, AIDS/Infectious Diseases Branch.

Reid D, Grist NR, Pinkerton IW, 1986, Infections in Current Medical Practice. Butterworths, London.

South Australian Health Commission, 1992, Guidelines for Infection Control in Health Care Establishments.  Adelaide.

The Sutherland Hospital, Caringbah, 1993, Infection Control Manual.  Sutherland.

Wenzel RP, 1993, 2nd ed, Prevention and Control of Nosocomial Infections. Williams and Wilkins, Baltimore.

Westley-Wise V et al, March 1993, Controlling Tuberculosis in New South Wales. New South Wales Health Department.

Winner HI, 2nd ed ,1978, Microbiology in Patient Care.  Hodder and Stoughton, London.

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