Experimental infections with Staphylococcus aureus, Streptococcus sanguis, Pseudomonas aeruginosa, and Bacteroides fragilis in the jaws of dogs

Abstract

This investigation was undertaken to determine whether well-characterized microorganisms in pure cultures inoculated into root canals could cause a periapical inflammation and whether these microorganisms could be isolated from pulpectomized but primarily noninfected root canals in other parts of the jaw. The experiments were made on fourteen dogs. In all dogs partial and/or total pulpectomies were performed under aseptic conditions and on the majority of the premolars in each quadrant of the jaw. The pulpectomized roots were inoculated with culture broth alone or culture broth with four different bacterial species ( Staphylococcus aureus, Streptocossus sanguis, Pseudomonas aeruginosa, and Bacteroides fragilis). In each dog only one species was inoculated. Thereafter the teeth were sealed with sterile cotton, fast-setting zinc oxide argard cement, and amalgam fillings. At different time intervals (from 4 up to 120 days) bacteriologic specimens were taken from the noninfected teeth by using sampling fluid (VMG I), charcoaled paper points, and transport medium (VMG III). Bacteriologic samples from the inoculated teeth were taken after 50 and 100 days to test that the inoculated microorganisms were still alive. Cultivation was carried out both aerobically and anaerobically. Radiographs were taken before and during the treatments and at the end of the observation period. A histologic examination was made after the termination of the experiment. The most important findings were the following. The inoculated microorganisms could be isolated from the majority of the primarily noninfected roots after 28 to 120 days, which demonstrated that a transport of microorganisms (anachoresis) had occurred. The roentgenologic examination revealed that radiolucencies could be observed on most roots. On the teeth where no roentgenologic changes could be observed no growth was obtained. The morphologic examination demonstrated a chronic inflammatory reaction on the roots where Pseudomonas aeruginosa and Bacteroides fragilis had been inoculated or could be isolated, while the inflammatory reaction on the roots with Staphylococcus aureus and Streptococcus sanguis was dominated by polymorphonuclear leukocytes.