Tuberculosis

Tuberculosis is an infectious disease. Tuberculosis can involve any organ in the body. When tuberculosis involves lungs it is called Pulmonary tuberculosis. It is the most common form of TB (more than 85% of all TB cases), when it affect organs other then lungs in the body it is called extra pulmonary tuberculosis. Transmission of tuberculosis occurs by the airborne spread of infectious droplets and droplet nuclei containing the tubercle bacilli.

Cause, Incidence and Type

Tuberculosis is caused by bacteria Mycobacterium tuberculosis (MTB). One fifth of the global TB incidence is in India, with 1.9 million new cases occurring every year and 0.87 million of these being infectious smear-positive cases. TB kills more adults in India than any other infectious disease. In India, an estimated 2.76 lakh deaths occur from TB every year.

Every day in India, 900 people die of tuberculosis.

Approximately 2 deaths every 3 minutes.

You can get TB infection by breathing in air droplets from a cough or sneeze of an infected person. This is called primary TB. Most people will recover from primary TB infection without further evidence of the disease although infection may stay inactive for years. However, in some people it can reactivate.

The following people are at higher risk for active TB:

• Elderly
• Infants
• People with weakened immune systems, for example due to diabetes, AIDS, any chronic illness, chemotherapy, steroids etc.

Risk of contracting TB increases in people those:

• Are in frequent contact with people who have TB
• Have poor nutrition
• Live in crowded or unsanitary living condition

Most people who develop symptoms of a TB infection first became infected in the past.

General symptoms of TB include:

• Excessive sweating, especially at night
• Fatigue
• Fever
• Unintentional weight loss

Pulmonary Tuberculosis can cause:

• Cough (usually with sputum)
• Coughing up blood
• Breathing difficulty
• Chest pain
• Wheezing

Persons having cough of 2 weeks or more, with or without other symptoms, are referred to as pulmonary TB suspect. They should have 2 sputum samples examined for AFB. Extrapulmonary Tuberculosis can cause:Symptoms based on the organ involved.

Tests to diagnose tuberculosis may include:

• Sputum examination for AFB(Acid Fast Bacilli) and cultures & drug sensitivity for MTB
• Chest x-ray
• Chest CT scan
• Bronchoscopy
• Thoracentesis
• Biopsy of the affected tissue
• Tuberculin skin test (also called a PPD test)
• Newer rapid diagnostic tools for detection of MDR TB
• Newer tools under evaluation for diagnosis of MDR/XDR TB

Treatment of Tuberculosis:

The disease classification, type of case, sputum result, severity of illness and history of previous treatment are the factors that determine the regimen used for treating a TB patient. The goal of treatment is to cure the infection with drugs that fight the TB bacteria. Treatment of active pulmonary TB will always involve a combination of drugs usually first line drugs initially and other drugs in resistant tuberculosis.

It is very important to elicit history of previous treatment for tuberculosis. It helps in defining a case; to identify patients with increased risk of acquired drug resistance and to prescribe appropriate treatment.

Grouping of Drugs:

• Group 1: First-line oral anti-TB agents-Isoniazid (H); Rifampicin (R); Ethambutol (E); Pyrazinamide (Z)
• Group 2: Injectable anti-TB agents-Streptomycin (S); Kanamycin (Km); Amikacin (Am); Capreomycin(Cm); Viomycin (Vm).
• Group 3: Fluoroquinolones-Ciprofloxacin (Cfx); Ofloxacin (Ofx); Levofloxacin (Lvx);Moxifloxacin (Mfx); Gatifloxacin (Gfx)
• Group 4: Oral second-line anti-TB agents-Ethionamide (Eto); Prothionamide (Pto); Cycloserine (Cs);Terizadone (Trd); para-aminosalicylic acid (PAS)
• Group 5: Agents with unclear efficacy (not recommended by WHO for routine use in MDR-TB patients)-Clofazimine (Cfz); Linezolid (Lzd); Amoxicillin/Clavulanate (Amx/Clv); thioacetazone (Thz); imipenem/cilastatin (Ipm/Cln); high-dose isoniazid (high-dose H); Clarithromycin (Clr)

Group 1 drugs are most effective and preferred for treatment of tuberculosis.

RNTCP(Revised National Tuberculosis Control Program) uses DOTS(Directly Observed Treatment Shortcourse) a short course chemotherapy given intermittently - thrice weekly under Direct Observation for both pulmonary and extra pulmonary tuberculosis patients.

Advantages of intermittent regimen are:

• As effective as daily treatment
• Facilitates DOT
• Reduction in total quantity of drugs consumed
• Fewer adverse reactions

Treatment regimens of six months duration either given daily, or on intermittent basis have been found to be equally effective and achieve high cure rates, prevent emergence of drug resistance and minimize relapses.

DOT is a supportive mechanism that ensures the best possible results in treatment of TB. Here, a DOT Provider helps the patient in taking the treatment, thereby ensuring adherence. Hence, by providing DOT, RNTCP ensures that patients receive the right drugs, in the right doses, at the right intervals and for the right duration.

Prognosis

Symptoms often improve in 2 - 3 weeks. A chest x-ray will not show this improvement until weeks or months later. The outlook is excellent if pulmonary TB is diagnosed early and treatment is begun quickly.

Complications

Pulmonary TB can cause permanent lung damage if not treated early.Medicines used to treat TB may cause side effects, including liver problems. Other side effects include:

• Changes in vision
• Orange- or brown-colored tears and urine
• Rash

A vision test may be done before treatment so your doctor can monitor any changes in your eyes' health over time.

Drug Resistant Tuberculosis

Some people can develop drug resistant tuberculosis due to poor compliance to treatment or ineffective treatment regimen or getting infected from the drug resistant tuberculosis bacteria.

MDR-TB is defined as tuberculosis disease where the bacilli is resistant to isoniazid (H) and rifampicin (R), with or without resistance to other drugs. Irregular consumption and frequent interruption in taking treatment for TB is the most common cause of acquiring multidrug resistance. In India, MDR-TB amongst new cases are estimated at 2- 3% and amongst re-treatment cases at 14-17%. Extensively Drug Resistant TB (XDR–TB) is a subset of MDR-TB where the bacilli, in addition to being resistant to R and H, are also resistant to fluoroquinolones and any one of the second-line injectable drugs (namely Kanamycin, Capreomycin or Amikacin)

Prevention

Prompt treatment is extremely important in controlling the spread of TB from those who have active TB disease to those who have never been infected with TB.DOTS is very effective and ensure compliance to treatment.

References

• Training module for medical practitioner –RNTCP. Central TB Division, India
• Revised National Tuberculosis Control Programme DOTS-Plus Guidelines. Central TB Division, India
• Fitzgerald DW, Sterling TR, Haas DW. Mycobacterium tuberculosis. In: Mandell GL, Bennett JE, Dolan R, eds. Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases. 7th ed. Orlando, FL: Saunders Elsevier; 2009
• Ellner JJ. Tuberculosis. In: Goldman L, Schafer AI, eds.Cecil Medicine. 24th ed.Philadelphia,PA: Saunders Elsevier; 2011

(Dr Rajlaxmi Borah)
Medical Officer
IIT Hospital