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Monday, March 06, 2006

The latest Holly Grail Test for bacterial infection? -Procalcitonin

"Use less antibiotics" has become a common theme. Antibiotics are expensive, pneumonia is a very big ticket item for CMS and hospitals and then there is the often invoked specter of antibiotic resistant in regard to which the conventional wisdom is that overuse of antibiotics is one of the causal elements. Recently, I referenced an article that suggested that effective "education" about overuse of antibiotics might have negative health effects because of underuse.

Procalcitonin, (PCT) as the name implies, is a precursor to the thyroid hormone calcitonin. Normally this substance is found in the thyroid glands but in some conditions,notably bacterial infections-but maybe not viral-blood levels rise.

A recent paper ( reported in the Feb. issue of "Pulmonary Medicine, pg 3, " Procalcitonin can guide antibiotic use in CAP cases) explored its use in community acquired pneumonia, in which the authors claimed that one could use the test to determine duration of antibiotic therapy. For the most part, how long we treat pneumonia is a function of physician preference and reliance on expert opinion.

As a recent journal club discussion of procalcitonin's role in detecting bacterial infections pointed out, already there are a number of "yes,buts" and "howevers". PCT may not always be elevated in bacterial sepsis, and may be elevated in heart failure and cardiogenic shock and I'll bet as time goes by more conditions and medications will be found to effect blood levels.

Appropriate restraint in the enthusiasm for thinking that PCT will always paint a bright line between bacterial and viral infections is expressed in this review by two investigators who have done some of the often quoted research in this area. PCT testing may well evolve into common use as one of the diagnostic elements to consider in evaluating a patient with possible infection.

1 comment:

Charles Weber said...

Heat is most effective against surface infections. However heat can considerably inhibit abdominal infections as well.
You may find the article below similar to this reference [1] useful. Heating the area of an infection up as hot as one can stand with an infrared lamp usually works beautifully for infections in the body near the surface. I am not certain that this works for gram positive bacteria. It is possible that it does not because they do not produce a fever in alligators [2]. However, heating Mycobacterium ulcerans to 40 degrees centigrade cures an infection [9].
I propose that fever evolved because bacteria grow poorly at elevated temperatures, and that the immune system evolved to become more active at elevated temperatures in order to take advantage of this bacterial weakness. The immune system is markedly stimulated by a rise in temperature. This may be a response arising through interleuken-1 [3]. This phenomenon has been demonstrated for interleukin–1 and interleukin-2 in post operative hypothermia [4]. Heat also stimulates tumor necrosis factor [5]. The above could be the reason why the ability to create a fever arose [6]. Doubling time of pneumococcal meningitis in rabbits is markedly increased at fever temperature, and that bacteria did not grow at all at 41 degrees centigrade in either soy broth or cerebral fluid [7], so it seems that the efficacy of body temperature effectiveness is dependent on more than enhancement of the immune system. It is conceivable in view of their results that rather than the fever evolving in order to enhance an innate characteristic of the immune system, the fever evolved to take advantage of an innate ineffectiveness of most bacteria at high temperatures and the immune system then evolved to be most effective during a fever. I have often cured a cold within a couple hours with an infrared heat lamp directed to my nose and it has been advantageous for me against other infections near the surface of the body such as sore throats and infected skin damage. It is probably necessary to start the temperature treatment early in the disease for viruses, because that is the case for rabies in mice [8]. Also it is possible that its efficacy is not on the virus so much as on the secondary infections in the case of nose colds. It is necessary to protect the eyes when applied near them though, because I have reason to believe their optical characteristics can change from a high temperature.
I have cured abscessed teeth that were not cured by anacardic acids in raw cashew nuts [ http://charles_w.tripod.com/tooth.html ] and were very slow to respond to amoxicillin by heating the jaw with an infrared lamp in conjunction with the amoxicillin. It is possible that a laser directed on the tooth would work better and should be tried. It is very desirable to get rid of an infection first even if a root canal operation is desired, in my opinion, and certainly imperative if a root canal operation is financially or tactically impossible. Development of a device that heated the tooth up directly to the correct temperature should be very advantageous, at least for the few gram negative tooth infections.
I have cured quite a few other kinds of infections in the last couple of years as well with artificial fever.
It would be desirable to perform experiments to determine whether this is a universal phenomenon or not for gram negative bacteria, because they produce many bad diseases near the surface of the body and this procedure would usually be practical and inexpensive as applied by patients. It would also be desirable to know for sure if gram positive infections can be cured.