TUBERCULOSIS

If we discuss about tuberculosis, there are many information about this infection. Tuberculosis become a world problem, and handling with care at WHO as one of disease that caused a death in worldwide.Currently,  one third of the world’s population is infected with  Mycobacterium tuberculosis and 8.9 – 9.9 million new and relapse cases of tuberculosis are reported every year . The emergence of new cases, the increased incidence of multi-drug resistant strains of M. tuberculosis, the adverse effects of first- and second-line antituberculosis drugs, and the increased incidence of tuberculosis associated with viral infections (Human Immunodeficiency Virus, HIV) has become a new worldwide problem.

So, in this article, I try to explain about Tubeculosis,definition,  caused by , diagnosis, and the treatment. One of the the reason to write this , is to gain the knowledge of patient about Tuberculosis, so it will impact to their compliance abour their medicine.

We have to start to say.. STOP TB!!!

 

What is it Tuberculosis?

Tuberculosis or TB (short for tubercles bacillus) is a common and often deadly infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis in humans. Tuberculosis usually attacks the lungs but can also affect other parts of the body. It is spread through the air, when people who have the disease cough, sneeze, or spit. Most infections in humans result in an asymptomatic, latent infection, and about one in ten latent infections eventually progresses to active disease, which, if left untreated, kills more than 50% of its victims.

Mycobacterium tuberculosis

Mycobacteria are Gram-positive (no outer cell membrane), non-motile, leomorphic rods, related to the Actinomyces. Most Mycobacteria are found in habitats such as water or soil. However, a few are intracellular pathogens of animals and humans. Mycobacterium tuberculosis, along with M. bovis, M. africanum, and M. microti all cause the disease known as tuberculosis (TB) and are members of the tuberculosis species complex. Each member of the TB complex is pathogenic, but M. tuberculosis is pathogenic for humans while M. bovis is usually pathogenic for animals.

M. bovis was causing TB in the animal kingdom long before invading humans. There is archaeological evidence of human infection by M. bovis probably through milk consumption.  So, thats why, we need to boiling a fresh milk, to avoid infection by M.bovis. M. tuberculosis is probably a human-specialized form of M. bovis developed among milk-drinking Indo-Europeans who then spread the disease during their migration into western Europe and Eurasia. M. tuberculosis and pulmonary TB had spread throughout the known world.

What are Mycobacteria?

Tuberculosis complex organisms are:

  • Obligate aerobes growing most successfully in tissues with a high oxygen content, such as the lungs.
  • Facultative intracellular pathogens usually infecting mononuclear phagocytes (e.g. macrophages).
  • Slow-growing with a generation time of 12 to 18 hours (c.f. 20-30 minutes for Escherichia coli).
  • Hydrophobic with a high lipid content in the cell wall. Because the cells are hydrophobic and tend to clump together, they are impermeable to the usual stains, e.g. Gram’s stain.
  • Known as “acid-fast bacilli” because of their lipid-rich cell walls, which are relatively impermeable to various basic dyes unless the dyes are combined with phenol. Once stained, the cells resist decolorization with acidified organic solvents and are therefore called “acid-fast”.

Pathogenesis:

Tuberculosis is transmitted by airborne droplet nuclei (containing tubercle bacilli).  Many droplet nuclei are capable of floating in the immediate environment for several hours. Large particles may be inhaled by a person breathing the same air and impact on the trachea or wall of the upper airway As the bacilli multiply, they spread through lymphatic channels to regional lymph nodes, and through the blood stream to the rest of the body

Clinical Manifestations

Most patients present as cases of pulmonary tuberculosis with fever, asthma. cough, weight loss, anorexia,  fatigue,  night sweats wasting, and pulmonary hemorrhage.

Weight loss and fatigue are more likely to lead to medical attention than is fever usually in the afternoon, which is often unrecognized.

Cough may vary from mild to severe, and sputum may be scant and mucoid or copious and purulent.

Hemoptysis may be due to cough of a caseous lesion or bronchial ulceration. Particularly in late chronic disease, bleeding may be copious and sudden owing to rupture of an artery within the fibrous walls of a cavity.

Radiology

The following characteristics of a chest radiograph favour the diagnosis of tuberculosis:

(1). shadows mainly in the upper zone; (2).patchy or nodular shadows; (3).the presence of a cavity or cavities, although these, of course, can also occur in lung abscess, carcinoma, etc; (4).the presence of calcification, although a carcinoma or pneumonia may occur in an areas  of the lung where there is calcification due to tuberculosis; (5).bilateral shadows, especially if these are in the upper zones; (6).the persistence of the abnormal shadows without alteration in an x-ray repeated after several weeks; this helps to exclude a diagnosis of pneumonia or other acute infection.

Diagnosis

A patient with tuberculosis pulmonary disease will come to the physician for one of three reasons:

(1). Suggestive symptoms;

(2).a positive finding on routine tuberculin testing;

(3).a suspicious routine chest roentgenogram.

The following need to be considered:

(1). Sputum examination

There are direct smear and culture.

Direct smear examination is only positive when large numbers of bacilli begin to be excreted, so that a negative smear by no means excludes tuberculosis. A negative smear in the presence of extensive disease and cavitation makes the diagnosis less likely, particularly if the negatives are frequently repeated.

(2). Tuberculin testing:

A positive tuberculin test although it is of great use in children, has limited diagnostic significance in older age groups.

Tuberculin Test

The tuberculin test in complished with old tuberculin (OT) and purified protein

derivative (PPD) of tuberculin that is a crude culture filtrate of M.tuberculosis.

OT and PPD dilute 0. 1 ml (unit and content)

(3). White blood count

The white blood count is usually normal. In practice the white blood count is only useful in a  minority of cases. When the patient is less ill and the radiological shadowing less extensive the count is Often normal or high normal.

Besides these routine investigations the history is sometimes of value.

 Treatment

Non-compliance of patients on chemotherapy is the most difficult problem in TB control. The critical issue in TB control is adopting the DOTS (directly observed short-term therapy). Strategy recommended by the WHO TB Programme. Chemotherapeutic Agents. The principles of antituberculous chemotherapy involve earlier,combination, appropriate drugs and durations.

Isoniazid. streptomycin, rifampin and pyrazinamide kill organisms, ethambutol and para-amino-salicylic acid restraint organisms.

 Isoniazid (INH)

Isoniazia is a principal agent used to treat tuberculosis. It is universally accepted for initial treatment.

Rifampin (RFP)

This is the newest drug effective against tuberculosis. Like isoniazid it is bacterieidal and highly effective, unlike isoniazid, it is also effective against most other   mycobacteria as well as other organisms.

Streptomycin (SM)

This was the first trully effective drug for the treatment of tuberculosis. It is administered only parenterally.

Pyrazinamide (PZA)

Pyrazmamide is a major oral agent used against mycobacteria but can produce gastro intestinal and liver toxicity.

Regimens of chemotherapy    

Because of concern over the rising prevalence of drug resistance, recent CDC recommendations advocate a four-drug regimen for most cases of known or suspected tuberculosis. INH and RFP are the central agent of any regimen based on their superior bactericidal activity and low toxicity. PZA has special utility in promoting rapid, early reduction in bacillary burden; in drug-susceptible cases. PZA need be given only for the initial 2 months to produce this effect. EMB is useful primarily to protect against the emergence of drug resistance in cases with unknown initial susceptibility patterns and large mycobacterial burdens; EMB may be terminated if susceptibility is reported or be continued throughout the duration of treatment if resistance is noted. Streptomycin(SM), parenteral agent, has found a diminishing role in modem therapy due to problems with regularly administering intramuscular injections; however, for patients with very extensive tuberculosis, SM may accelerate initial bactericidal activity.

To initial patients : we can select short-term chemotherapy 2HRZS(E)/4HR, the duration lasts 6 months.

To retreatment patients: 3HRZSE/5HRZ , the duration lasts 6-12 months.

To MDR-TB: MDR-TB means that resistant to both INH and rifampin. We can select five kinds of antitubercule drugs in the stage of extensive . These drugs include aminoglycosides(amikacin, kanamycin, capremycin), cycloserine, EMB, quinolones(levofloxacin, ofloxacin), PZA, ethionamide.

In the stage of consecutive, we can select three kinds of drugs,including ethionamide, quinolones and EMB.The whole therapy lasts at least 18 months.

Prevention of Tuberculsis Vaccination

BCG(bacille. Calmette Guerin) is a strain of M.bovis with aaemuated virulence for man. BCG Vaccination can obtain immunity acquired for tubercle bacillus, therefore.is one of the most important tuberculosis prevention.

Vaccination target: infants children and youngster of tuberculin negative (vaccination is of course, of no use in tuberculin-positive persons).