Clinical comparison of glucose broth with nutrient broth blood cultures for the detection of “Streptococcus viridans” bacteraemia

Viridans streptococci were isolated from the blood stream of half of 50 patients undergoing dental extractions approx. 2 min before blood culture. Glucose and nutrient broths were tested in parallel. There was no significant difference between the isolation rates of streptococci by the two methods after incubation for 7 days, nor did the addition of glucose 0.1% to nutrient broth significantly increase the speed of detection of streptococci; the isolation rates of streptococci during the first 48 h of incubation were similar with both types of broth. Although there were a few more isolations of streptococci from the glucose broth than from the nutrient broth during the first 20 h. the difference was not statistically significant. No rapid lethal effect against streptococci was observed in glucose broth during incubation for 7 days. These results suggest that adding glucose 0.1% to nutrient broth for blood culture does not influence the recovery of organisms from patients with “Streptococcus viridans” bacteraemia after incubation of the broth for 2-7 days.