The "TB case"

In our society, flooded with a multitude of news destined to evaporate in a few days, the "TB case", which for weeks has been the scoop in newspapers and TV, is causing unnecessary anxiety and alarm.

The story is well known. A complaint filed by an association of consumers (Codacon) about the presence of a nurse "suffering from tuberculosis" in service at the Policlinico Gemelli in Rome, led to controls that have shawn 122 infections with Mycobacterium tuberculosis among children who were admitted to the hospital (currently,however, only a child born March 22, 2011 developed the disease). An

investigation of the Public Prosecutor of Rome (essentially a routine, and so far without any indictment), and the announcement of a "class action" brought by dozens of families against the management of the Hospital, has

set off a truly incredible scare campaign that will hopefully end soon.

Without getting into the reasons for which these campaigns are flaring on a daily basis, and into the liability issue involving the management of the Gemelli Hospital, (for the detection of the liability an investigation is being ordered by the Public Prosecutor’s Office of Rome), we shall limit ourselves to expose the health and medical aspects of the " Tuberculosis danger " in Italy.

Commonly, when talking about "Tuberculosis", or TB, thoughts run to harrowing images of death, the most

famous of these, of course, is the "consumption" of Violetta in the opera "La Traviata" by Giuseppe Verdi. In fact, according to the World Health Organization, one third of world population (an eighth among the industrialized countries) has been exposed to tuberculosis and may, therefore, said to be "suffering from tuberculosis."

This situation is caused by a group of microbes, first of all the Mycobacterium tuberculosis (also known as "Koch's bacillus", named after its discoverer), and then the Mycobacterium bovis, Mycobacterium africanum, mycobacterium microti and Mycobacterium canetti.

The reason why this infection spreads, is explained by the transmission mechanism of its microbes. When people with active pulmonary TB cough, sneeze, talk or spit, expel

aerosol droplets 0.5 to 5 μm in diameter. A single sneeze can release up to 40,000 particles. Each of these droplets may transmit the disease, and the inhalation of only a single bacterium can create a new infection, since the infectious dose of tuberculosis is very small. People with prolonged, frequent, or intense contacts are at particular risk of becoming infected, with a rate of approximately 22%.

A person with active, but not treated tuberculosis, can infect as many as 10-15 people a year. Other individuals subject to risk include people who live in areas such as those of the Third World, where active TB is very diffuse, or in places frequented by people at high risk such as, for example, patients imunocompromised by diseases such as AIDS, people taking immunosuppressive drugs, and healthcare personnel who treat such patients.

About 90% of people infected by Mycobacterium tuberculosis has asymptomatic TB infection (also called LTBCI, acronim for latent infection tuberculosis), and there are only 10% of chances that the latent infection will evolve in TB during lifetime.

The TB infection begins when the mycobacteria reach the pulmonary alveoli, where they attack and replicate within alveolar macrophages. The primary site of infection in the lungs is called the Ghon’s focus. The bacteria are collected

by dendritic cells, which do not allow their replication but can transport the bacilli to local mediastinal lymph nodes. The primary lesion of mycrobacterium accompanied by satellite adenopathy represents the "primary complex", in which the bacteria remain walled off without giving rise to clinical events, but they can resume their pathologic activity and spread especially following an immunodeficiency of the individual. The further spread via the bloodstream goes

toward the more distant tissues and organs, and secondary TB lesions can develop in the apices of the lungs, in peripheral lymph nodes, in the kidneys, in the brain and in the bones. Every body part can be affected by the disease, but it rarely affects the heart, skeletal muscle, pancreas and thyroid. The infection may increase, or decrease, and tissue destruction and necrosis are balanced by healing and fibrosis. The affected tissue is replaced by scarring and cavities filled with white necrotic material. Active disease in the necrotic material is combined with the air that flows through to the bronchi, and it is coughed out. Since it contains active bacteria, can then spread the infection. The

disease usually manifests with fever, chills, night sweats, loss of appetite, loss of weight, pallor, and a tendency to tire easily. In the case of lung infection symptoms include chest pain, hemoptysis and a cough for longer than three weeks. As mentioned above, the infection may localize at sites other than lungs such as the intestine, the lymphatic system, tonsils, liver, bones, esophagus, central nervous system, blood vessels, meninges, kidneys, and be manifested by symptoms other than those of pulmonary tuberculosis.

Antibiotics are used to treat TB; the most used are rifampicin and isoniazid. However, different from the short-term treatment of antibiotics typically used for other bacterial infections, TB requires much longer periods (6 to 12 months) to completely eliminate the mycobacteria from the body. Treatment for latent TB usually uses a single antibiotic, while active TB will be more effectively treated with the combination of several antibiotics, to reduce

possibility that bacteria develop resistance to the antibiotics. People with latent infections are treated to prevent the possible development of TB in its active form. However, the treatment utilizing rifampicin and isoniazid is not without risks. The Centers for Disease Control and Prevention (CDC) has provided healthcare professionals with recommendations against the use of rifampicin and isoniazid for the treatment of latent tuberculosis, due to the number of hospitalizations

and deaths from liver damage associated with the combined use of these drugs.

Tuberculosis resistant to drugs is transmitted the same way as ordinary TB. The primary resistance occurs in

people who are infected with a resistant strain of TB. A patient with ordinary TB develops secondary resistance (or acquired resistance) during TB therapy because of inadequate treatment, non-compliance with the prescribed treatment, or use of drugs of low quality. These forms of drugs resistant TB are a problem in many developing countries, because the treatment is prolonged and requires

more expensive drugs. Multidrug-resistant tuberculosis (MDR-TB) is defined as TB resistant to the two most effective first-line drugs: rifampicin and isoniazid. The extensively drugs resistant tuberculosis (XDR-TB) is also immune to three, or more, of the second-line drugs.

TB prevention and control has two parallel approaches. In the first, people with TB and their loved ones are

identified and treated. Identification of infections often involves examining high-risk groups for TB. In the second approach, children are vaccinated to protect them from TB. Unfortunately no available vaccine provides reliable protection for adults. However, in tropical areas

where levels of other species of mycobacteria are high, exposure to nontuberculous mycobacteria gives a

partial protection to TB. The first vaccine (consisting of heat killed mycobacteria) against TB was designed in the early 1900's by the Italian doctor Edward Maragliano; later, the vaccination was performed using live attenuated mycobacteria tuberculosis from cattle, developed by Albert

Calmette and Camille Guerin, the so-called 'BCG' (Bacillus Calmette-Guerin). Many countries use BCG as part of their TB control programs, especially for children. In South Africa, for example, the country with the highest concentration of TB, the vaccine is given to all children under three years.Several vaccines to prevent TB infection are being developed. The last, the one of M. Jacobs and others,

uses bacteria M. smegmatis lacking the gene sets ESX-3, by inserting in their place the analog set of genes of M. tuberculosis, but the results of early tests on animals have not been encouraging. For this reason the WHO based its campaign "Stop TB", on the fight against malnutrition (as it is very well known is the main factor of the spread of TB) and respect for elementary rules of hygiene, as, for example, according to the WHO, stopping the rude habit of spitting on the floor, would halve the risk of transmission of tuberculosis.