Effect of high dose oral zinc in mice with severe infection with Streptococcus pneumoniae

Zinc is important for normal function of the immune system and inflammation increases the demand for zinc. We hypothesized that high doses of zinc given during acute pneumococcal illness would alter the severity of infection. 24 six-week-old BALB/c mice were anaesthetized and infected intranasally with Streptococcus pneumoniae. Zinc intake was controlled by administering zinc through an intragastric tube. One group was given normal doses (5 microg/d) and the other group high doses of zinc (225 microg/d). We counted the number of bacteria from venous blood at 24 and 48 h, and from heart puncture and nasal wash at 72 h after intranasal challenge. Mice given excess zinc had 2.65 micromol/l, i.e. 25% higher (p= 0.05) mean plasma zinc concentration compared to those given normal amounts. 75% of mice in both groups developed pneumococcal bacteraemia. There were no differences in the numbers of S. pneumoniae colony forming units (CFUs) in blood or nasal wash between the groups. Thus, high doses of zinc did not alter the severity of systemic pneumococcal infection in mice.