Focal infection theory

Focal infection theory is the historical concept that many chronic diseases, including systemic and common ones, are caused by focal infections. In present medical consensus, a focal infection is a localized infection, often asymptomatic, that causes disease elsewhere in the host, but focal infections are fairly infrequent and limited to fairly uncommon diseases. (Distant injury is focal infection's key principle, whereas in ordinary infectious disease, the infection itself is systemic, as in measles, or the initially infected site is readily identifiable and invasion progresses contiguously, as in gangrene.) Focal infection theory, rather, so explained virtually all diseases, including arthritis, atherosclerosis, cancer, and mental illnesses. Focal infection theory is the historical concept that many chronic diseases, including systemic and common ones, are caused by focal infections. In present medical consensus, a focal infection is a localized infection, often asymptomatic, that causes disease elsewhere in the host, but focal infections are fairly infrequent and limited to fairly uncommon diseases. (Distant injury is focal infection's key principle, whereas in ordinary infectious disease, the infection itself is systemic, as in measles, or the initially infected site is readily identifiable and invasion progresses contiguously, as in gangrene.) Focal infection theory, rather, so explained virtually all diseases, including arthritis, atherosclerosis, cancer, and mental illnesses. An ancient concept that took modern form around 1900, focal infection theory was widely accepted in medicine by the 1920s. In the theory, the focus of infection might lead to secondary infections at sites particularly susceptible to such microbial species or toxin. Commonly alleged foci were diverse—appendix, urinary bladder, gall bladder, kidney, liver, prostate, and nasal sinuses—but most commonly were oral. Besides dental decay and infected tonsils, both dental restorations and especially endodontically treated teeth were blamed as foci. The putative oral sepsis was countered by tonsillectomies and tooth extractions, including of endodontically treated teeth and even of apparently healthy teeth, newly popular approaches—sometimes leaving individuals toothless—to treat or prevent diverse diseases. Drawing severe criticism in the 1930s, focal infection theory—whose popularity zealously exceeded consensus evidence—was discredited in the 1940s by research attacks that drew overwhelming consensus of this sweeping theory's falsity. Thereupon, dental restorations and endodontic therapy became again favored. Untreated endodontic disease retained mainstream recognition as fostering systemic disease. But only alternative medicine and later biological dentistry continued highlighting sites of dental treatment—still endodontic therapy, but, more recently, also dental implant, and even tooth extraction, too—as foci of infection causing chronic and systemic diseases. In mainstream dentistry and medicine, the primary recognition of focal infection is endocarditis, if oral bacteria enter blood and infect the heart, perhaps its valves. Entering the 21st century, scientific evidence supporting general relevance of focal infections remained slim, yet evolved understandings of disease mechanisms had established a third possible mechanism—altogether, metastasis of infection, metastatic toxic injury, and, as recently revealed, metastatic immunologic injury—that might occur simultaneously and even interact. Meanwhile, focal infection theory has gained renewed attention, as dental infections apparently are widespread and significant contributors to systemic diseases, although mainstream attention is on ordinary periodontal disease, not on hypotheses of stealth infections via dental treatment. Despite some doubts renewed in the 1990s by conventional dentistry's critics, dentistry scholars maintain that endodontic therapy can be performed without creating focal infections. In ancient Greece, Hippocrates reported cure of an arthritis case by tooth extraction. Yet modern focal infection theory awaited Robert Koch's establishment of medical bacteriology in the late 1870s to early 1880s. In 1890, Willoughby D Miller attributed a set of oral diseases to infections, and a set of general diseases—as of lung, stomach, brain abscesses, and other conditions—to those infectious oral diseases. In 1894, Miller became the first to reveal existence of bacteria in samples of dental pulp. Miller advised root canal therapy. Yet focal infection theory met a cultural climate where ancient and folk ideas, long entrenched via Galenic humoral medicine, found new outlets through bacteriology—a pillar of the new 'scientific medicine'. Emigrating from Russia in 1886, international scientific celebrity Elie Metchnikoff—discoverer of phagocytes, mediating innate immunity—was embraced in Paris by Louis Pasteur, who granted him an entire floor for research once the Pasteur Institute, the globe's first biomedical institute, opened in 1888. Later the Institute's director and 1908 Nobelist, Metchnikoff believed, as did his rival Paul Ehrlich—theorist on antibody, mediating acquired immunity—and as did Pasteur, that nutrition influenced immunity. Sharing Pasteur's view of science as a means to suppress the problems plaguing humankind, Metchnikoff brought into France its first cultures of yogurt for probiotic microorganisms to foster health and longevity by suppressing the colon's putrefactive microorganisms alleged to foster the colon's toxic seepage, autointoxication. As the 20th century opened, British surgeons were still knife-happy, and called for 'surgical bacteriology'. Surgical pioneer Sir Arbuthnot Lane, famed for an emergency appendectomy performed on England's royalty, drew from Metchnikoff and clinical observation to issue dire warnings about 'chronic intestinal stasis'—that is, constipation—its 'flooding of the circulation with filthy material' and causing autointoxication, which Lane then treated with colon bypass and colectomy. In America, alleged bowel sepsis wreaking degeneration and disease had been targeted since 1875 by John Harvey Kellogg in Michigan at his huge Battle Creek Sanitarium—he coined the term sanitarium—yearly receiving several thousand patients, including US Presidents and celebrities, and advertising itself as the 'University of Health'. When embracing focal infection theory, however, American medical doctors sided against alleged 'health faddists' like Kellogg as well as Sylvester Graham, and endorsed the academic tradition of German 'scientific medicine'. In 1900, British surgeon William Hunter blamed many disease cases on oral sepsis. In 1910, lecturing in Montreal at McGill University, he claimed, 'The worst cases of anemia, gastritis, colitis, obscure fevers, nervous disturbances of all kinds from mental depression to actual lesions of the cord, chronic rheumatic infections, kidney diseases are those which owe their origin to or are gravely complicated by the oral sepsis produced by these gold traps of sepsis.' He apparently indicted dental restorations. Incriminating their execution, rather, his American critics lobbied for stricter dental licensing requirements. Still, Hunter's lecture—as later recalled—'ignited the fires of focal infection'. Ten years later, he proudly accepted that credit. And yet, read carefully, his lecture asserts a sole cause of the sepsis: dentists who instruct patients to never remove partial dentures. Focal infection theory's modern era really began with physician Frank Billings, based in Chicago, and his case reports of tonsillectomies and tooth extractions claimed to have cured infections of distant organs. Replacing Hunter's term oral sepsis with focal infection, Billings in November 1911 lectured at the Chicago Medical Society, and published it in 1912 as an article for the American medical community. In 1916, Billings lectured in California at Stanford University Medical School, this time printed in book format. Billings thus popularized intervention by tonsillectomy and tooth extraction. A pupil of Billings, Edward Rosenow held that extraction alone was often insufficient, and urged teamwork by dentistry and medicine. Rosenow developed the principle elective localization, whereby microorganisms have affinities for particular organs, and also espoused extreme pleomorphism.