Abstract
In order to elucidate the causes for the increased mortality of aged patients with bacterial central nervous system (CNS) infections, we compared the course of Streptococcus pneumoniae (S. pneumoniae) meningitis in aged and young mice. Aged (21.2 ± 3.1 months, n = 40) and young (3.2 ± 0.9 months, n = 42) C57BL/6N and B6/SJL mice were infected by intracerebral injection of 50–70 CFU S. pneumoniae serotype 3 and monitored for 15 days. Aged and young mice did not differ concerning mortality (35% versus 38%), weight loss, development of clinical symptoms, bacterial concentrations in cerebellum and spleen as well as the number of leukocytes infiltrating the CNS. In contrast to results from our geriatric mouse model of Escherichia coli (E. coli) meningitis, where aged mice showed a higher mortality and an impaired elimination of bacteria, we did not find any differences between aged and young mice after intracerebral infection with S. pneumoniae serotype 3. This indicates that the increased susceptibility of aged mice to bacterial CNS infections is pathogen-specific: It appears less prominent in infections caused by hardly phagocytable pathogens with thick capsules like S. pneumoniae serotype 3, where the age-related decline of the phagocytic capacity of microglia and macrophages has a minor influence on the disease course.
Highlights
As a consequence of increasing life expectancy, the population is ageing
Primary murine macrophages and microglial cells showed an age-related decline of their ability to phagocytose E. coli [7]. These results suggested, that strategies to increase the phagocytic potential of aged macrophages and microglial cells appear promising for the prevention and therapy of central nervous system (CNS) infections in the elderly
The overall survival after intracerebral infection with S. pneumoniae serotype 3 did not differ between young and aged mice (Fig. 1: log-rank test, P = 0.98)
Summary
As a consequence of increasing life expectancy, the population is ageing. The number of persons aged ≥80 years is projected to more than triple by 2050 and to increase more than seven-fold by 2100 [1]. Infectious diseases play an important role in the increasing group of elderly people and are accompanied by a higher mortality and a more severe course of disease [2, 3]. Patients more often develop severe neurological symptoms like coma, epileptic seizures or focal neurological deficits and show an increased mortality in comparison to younger patients [4, 5]. In persons aged ≥60 years, the incidence of S. pneumoniae meningitis
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