Why all of us don’t get Tuberculosis.
When our family went to Afghanistan in 1968 to teach medicine for two years with daughters ages 9, 11, and 14, we fully expected some of them to be exposed to tuberculosis and for their tuberculin tests to convert to positive. We tested them with the routine skin test every six weeks to be able to give a short course of medication soon after the skin test conversion to minimize the risk of clinical infection. Surprise! Their skin tests remained negative for the duration, all three of them.
A positive skin test means that any TB bacilli, which enter the lungs, will be promptly surrounded by a vigorous inflammatory reaction to wall the germs off from spreading without necessarily killing the germs. Much later, when people with a positive skin test become debilitated from some other disease, or even just plain old age, these walled off germs may break loose from the scar and multiply, infecting new people in addition to the patient himself. Since many of the local population in Afghanistan had chronic coughs, and half of our hospital patients had active tuberculosis, you can understand our surprise at the continuing negative tests in the children. Before the modern success in treating tuberculosis healthy people with a positive skin test were considered resistant to the disease compared to people with negative skin tests because they had already demonstrated resistance. Now it is preferable to remain negative to tuberculin throughout life.
During the early 1950’s while I was in specialty training in Denver, the grand old man of tuberculosis expertise, James Waring, was professor of medicine, emeritus, and still actively teaching. I remember him speculating during rounds that a recent conversion of skin tests represented an active infection, which could be treated with reduced risk of progression with the just recently available anti-tuberculosis medications. The first paragraph above indicates that this was soon standard practice.
Further evidence that a recent positive skin test is an active infection came in the 1960’s when positive cultures for tuberculosis were obtained from asymptomatic recent skin test converters. Since my student days in the 1940’s suspected cases of tuberculosis were proven to be infectious, even in the absence of bacilli visible under the microscope in sputum, by culture of stomach contents obtained before getting out of bed in the morning. During sleep any germs arriving in the throat would most likely swallowed and available in the stomach for culture. Tubercle bacilli are rugged and not promptly killed by stomach acid. In normal healthy people the lungs continuously cleanse themselves by forming a thin, continuous sheet of mucous throughout the bronchial tree and trachea (wind pipe). This thin sheet of mucous is conveyed to the throat and swallowed with the normal small amounts of saliva, which is forming all the time. Tiny “hairs” all over the surface of the cells lining the bronchial tree called cilia convey the mucous toward the throat by coordinated wave like movements which brush the mucous along. This mucous cleanses the lungs of all but the finest dust in addition to removing myriad germs of all types. When we have a cold and more mucous accumulates in puddles, this delays the timely expulsion of the thin mucous sheet increasing the chance of pneumonia from quite a list of common germs. Many of these are continuous inhabitants of the nose and throat.
So this cleansing mechanism is vital for health all of the time. Like the heart, these cilia never stop beating their coordinated movement of mucous. The lining of the nasal passages and sinuses also has cilia and a mucous sheet with a similar cleansing action. The mucous sheet moves contaminating particles to the throat for disposal and against gravity if the drainage of a particular sinus is not at its lowest point similar to the lungs moving mucous and its load of contaminants against gravity.
Gradually, I realized that my children must have inhaled countless germs and expelled them mechanically before there was any opportunity to experience them chemically because the germs were not present long enough to set up housekeeping and multiply in a more stagnant puddle of mucous.
The above is an illustration of the benefits of a healthy lifestyle enhancing our body’s ability to take care of itself. In addition to the obvious healthy diet and adequate rest, we should remember that overeating increases the risk of aspiration, especially excessively fast eating. Alcohol in excess fosters aspiration of swallowed material. Alcohol also inhibits phagocytosis of germs by white blood cells. Sulfa drugs, which only suppress growth of germs without killing them, require cooperation of white blood cells for their destruction. When anti-serum for pneumonia was becoming obsolete because of sulfa drugs, existing stocks were saved for use in treating alcoholics with pneumonia.. Penicillin, which kills germs dead, changed all that.
Above all nicotine paralyzes the cilia of the bronchial tree. A cigarette cough is partly irritation and partly accumulated mucous which puddles instead of moving as a continuous, efficient, thin sheet. Frustrating this natural defense mechanism contributes greatly to the harms of nicotine to health.
John A. Frantz, M.D.
October 3, 2002
Addendum, August 23, 2003. I have just run across solid academic corroboration of my surmise about smoking increasing the risk of acquiring tuberculosis. The Lancet for August 16, 2003, has a report entitled “Smoking and mortality from tuberculosis and other diseases in India: retrospective study of 43,000 adult male deaths and 35,000 controls” by V. Gajalakshima and others. Females were not included because so few of them use tobacco. Here is the most pertinent quote from their report:
In particular, 73% of those who died of tuberculosis had smoked, yielding a highly significant risk ratio of 4.2 (3.7-4.8)[the 3.7-4.8 are confidence intervals, a statistical derivative]. Likewise 68% of those who died of other respiratory diseases had smoked (3.6, 3.0-4.3).
In plain English this means that these authors found that smokers were more that four times as likely to get tuberculosis as were non-smokers.
Due to budgetary constraints
the light at the end of the tunnel
(Is this a pseudo-aphorism?)