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Versión en Español

Tuberculosis and the BCG Vaccine

Date: (21/5/2009)

Facultad de Medicina

In contrast to the developed countries where there are fewer cases of people suffering from tuberculosis, in developing countries such as Mexico, this vaccine is applied in order to prevent pulmonary diseases.

Mycobacterium tuberculosis dyed with Ziehl- Nielsen.

By Gabriela Hernandez Villanueva

A scar in the right arm is the result of the BCG (Bacillus Calmette Guerin) vaccine which is commonly seen among Mexican people; however, there are many people who do not know about it nor about the diseases this vaccine protects us from.

This vaccine is applied to the newborn or to babies younger than three months old only once in their lives by intradermal route. If they are older, they need a prior application of the cutaneous tuberculin test (PPD, Spanish acronym). Only children who are in ideal health conditions are vaccinated to prevent pulmonary diseases.

Tuberculosis (TBC) is a contagious bacterial infection that mainly affects the lungs but it could be spread to other organs. This disease, caused by Mycobacterium tuberculosis is one of the most important problems of public health and also, it is linked to socio-sanitary deficiencies, poverty overcrowding and malnutrition.

“This disease has been with us for thousands of years. One of the theories is that this microorganism, which is in bovines moved to humans and it really specialized to the extent that it now affects more our race, the man.”

“Now that human genetics and microorganisms’ evolution are so well-known, we wonder who developed this disease, who was the person that transmitted it to other people. Traditionally, it has been told that tuberculosis emerged form people around the world, however, —and even though ten years ago the Mycobacterium tuberculosis chromosome was discovered by professor Stuart Cole — it has evolved,” explained Dr. Lucio Vera Cabrera, who is a specialist in microbiology and an UANL researcher.

The Hospital Universitario registers 150 cases each year of people with a tuberculosis profile, and out of these, many of them are drugs resistant.

“When patients go to the consultation, treatment is given to them, but sometimes it is so long (six months) that becomes uncomfortable or even inexistent in the clinics. When not taken correctly, and if the bacteria cannot be removed, they can react and that is when the resistant bacteria grows.”

“The BCG vaccine, is not a vaccine produced with the Mycobacterium tuberculosis bacteria. It is a bacteria, it is like its sister, very similar and is called Mycobacterium bovis (bovine stump). At the beginning of last year, this vaccine was applied massivley to children because it protects, at a certain extent, from extra- pulmonary diseases.”

“Currently, this vaccine is not applied in some developed countries such as Europe, Canada and the United States of America because the new tuberculosis cases are low. But in other developing countries such ours, it is applied. However, it does not offer a protection against the pulmonary disease,” said Dr. Vera, who is the author of the research “Analisis genetico y biologico de cepas de Mycobacterium tuberculosis polimorficas para los genes de fosfolipasa C.”

The first stage of this disease regularly presents no symptoms. However, in a second period, the symptoms could be: cough, sometimes with phlegm; bloody expectoration, excessive sweat, especially at night, fever, and involuntary loss weight. When it advances, the difficulty of breathing could be presented as well as thoracic pain and sibilance.

“Due to the fact that this infection is latent among patients who present no symptoms and it is transmitted from patients to most their direct contacts, it is important to detect them, provide them with treatment, medication, confirm they take care of themselves, and verify they get cured,” said the specialist.

We have to mention that this disease is totally curable if sick people take the right medication and time is respected.

“Treatment must be taken rigorously, because normally, there is an improvement in the first 15 days, the patient feels healthy and does not take the medication, but the bacteria is there, latent in small concentrations inside the phagocytic lungs cells or tissues. If medication is not taken, those resistant microorganisms are selected and they start reproducing themselves again,” commented Dr. Lucio Vera.

A third of the world population is infected with this microorganism, which survives a first contact with human immunological system and it stay in a inactive manner, latent for long time periods, inclusive years in the pulmonary tissues in small classifications. This is important if we consider it in infected people with human immunodeficiency virus, because their immune system can allow the development of a latent and endo infection,” said Dr. Lucio Vera.

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