Many difficulties are encountered in the isolation of bacteria that gain forceful entry into the blood stream during tooth removal. Blood-culture techniques must be sensitive to detect the relatively few organisms present. Contamination of the culture must be controlled; otherwise, the detection of micro-organisms may be inaccurately interpreted. This is particularly important for the detection of postextraction bacteremia because some of the organisms, which in ordinary cultures might be disregarded as contaminants, are true inhabitants of the mouth that can ultimately enter the circulation.There is a wide variation in the percentage of positive blood cultures found after extraction of teeth as reported by different investigators; the range is from 12.8 to 93.4 per cent. A comparison of the work of various investigators revealed considerable differences in clinical and laboratory techniques, differences adequate to explain the disparate results.1-'2 Variances occurred in such clinical matters as the sterility of the gingival sulcus before tooth extraction, the number of teeth extracted at one sitting, the degree of trauma, and the kind of anesthesia. Laboratory practices varied in such matters as the size of the blood sample, the number of aliquots cultured, the addition of agents to neutralize the antibacterial action of the blood, the number of different media, and the utilization of aerobic, as well as anaerobic, culturing methods.Whereas clinical practices affect the actual incidence of bacteremia, laboratory practices affect the success of its detection. If contamination is avoided and if clinical conditions are comparable, those laboratory procedures which yield the highest percentage of positive blood cultures are the most sensitive.The purpose of this investigation was to determine what laboratory conditions increase the sensitivity of blood-culture technique for the detection of dental bacteremias. Four sets of conditions were varied: (1) different media and the use of aerobic and anaerobic procedures, (2) single blood samples as compared with multiple aliquots, (3) the neutralization of the antibacterial action of blood, and (4) variations in the size of the blood samples.
EXPERIMENTAL METHODSThe data of the laboratory investigations came from three experimental studies in a series of 124 cases following tooth removal. The patients ranged from sixteen to ninety
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