28 November 2021

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Focal infection theory: a new modernity in view of microbiota recent studies?

Authors: Carlo Fornaini, Francesco Di Pierro

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The “Focal Infection Theory”, which was very popular in the 1930s, hypothesized the possibility that an infection of a specific zone might migrate to other different organs, even not contiguous, causing diseases  at a distance; this theory was responsible for very invasive preventive treatments, such as indiscriminate tooth extractions and tonsillectomies; it was abandoned due to the scanty scientific evidence.

Today, however, thanks to new epidemiological studies, several relationships between oral infections and many systemic diseases have been demonstrated.

The aim of this narrative review of the literature is to describe the microbiotic movements between the different zones of the body and to suggest a new approach to infections and their systemic effects prevention.

Materials and Methods
Considering microbiotics as “microbic consortiums, mainly represented by bacteria, which move in space and time”, their movements were described starting from phylogeny and then defining the vertical transmission (mother-child) and horizontal transmission (inside family) lines, as well as the existing paths between different districts inside the same person (haematogenic, entero-mammary and ascending from vagina to uterus).

Results and Conclusions
Even if reconsidered in view of the recent advances in the microbiological field, the theory of the “focal infection” may still be very alive, although the clinical perspectives, and particularly the possibility to carry out both proper prevention and the most conservative possible therapy, have completely changed its prognosis: in fact, the great limit of this theory consisted in the extremism of the therapeutic choices, mainly resulting in massive teeth extractions due to the scanty scientific and technologic knowledge of that time.

Assuming that microbic interconnections are largely structured inside the host, and that it is possible to divide microbiotics into primary (oral, fecal, vaginal, cutaneous and nasal) and derived (pulmonary, endometrial, urinary bladdery, mammary and prostatic), the successful therapeutic approach may be represented by the possibility to contrast the former by a bacterial therapy, thus taking advantage of the eubiotic dominances which are known for them, in order to better “construct” the latter.

Clinical significance
Several probiotics strains are available today for dentists, which may be orally assumed for modifying, in a eubiotic way, the oral microbiotic; many studies have confirmed that they may be very effective to control  oral diseases such as decay and periodontitis.

Among these, K12 strain seems to be very interesting: it derives from Streptococcus Salvarius, originally used against Streptococcus Pyogenes infections and subsequently suggested for a great number of indications; a great amount of research has in fact confirmed its efficacy to treat pharyngitis, tonsillitis and otitis both in child and adult, in treating periodontitis and to eliminate halitosis; moreover, a very recent study suggested its successful employment in the treatment of Oral Lichen Planus.

It may be therefore possible to suppose for it a role beyond oral cavity, for modifying in  eubiotic way other different organs of the body, even not close to the head-neck district.