Pneumococcal pulmonary infection, septicaemia and survival in young zinc-depleted mice

The aim of the present study was to explore whether mice fed a diet low in Zn (2.0 mg Zn/kg diet) for a relatively short period of time were more pron e to severe Streptococcus pneumoniae infection than mice fed a normal diet (25 mg elemental Zn/kg). The Zn-deficient mice were compared with mice in t wo Zn-adequate control groups; one pair-fed and another with free access to the diet. After 2 weeks feeding, the mice were infected intranasally under anaesthesia with a suspension containing about 10(7) pneumococci. Clinical status was observed every day and blood samples were examined for S. pneum oniae every second day for a week. All infected mice examined carried the i nfecting strain intranasally. The survival time and time before positive bl ood culture were significantly shorter in the Zn-depleted group than in the pair-fed Zn-adequate group (hazard ratios 15.6 and 3.2, P<0.0001 and P=0.0 45 respectively). At the end of the observation period, ten of the twelve m ice in the Zn-deficient group were dead while one of twelve and two of twel ve were dead in the two Zn-adequate control groups. This study shows that e ven acutely-induced Zn deficiency dramatically increases the risk of seriou s pneumococcal infection in mice.