Acute bacterial meningitis in adults. A 20-year overview

Abstract

Although acute bacterial meningitis is most common among children, the disease nevertheless poses serious problems in the adult population. However, most clinical overviews of the disease have either focused on children or all age groups combined.Information on all patients 5=16 years of age diagnosed in Iceland during the years 1975-1994 was collected from patient records from 10 hospitals and the records of the Dept. of Microbiology at the University Hospital which processes all bacterial isolates from the CSF identified in the country.One hundred thirty six patients were identified, but complete records were found for 123 patients. Yearly incidence ranged from 1.7-7.2/100,000 inhabitants with a mean of 3.8/100,000. The most common causative organisms were Neisseria meningitidis (54%), Streptococcus pneumoniae (20%), Listeria monocytogenes (6%) and Haemophilus influenzae (5%). The relative incidence of N. meningitidis was dependent on age, the organism caused 93% of infections in the 16-20 year age group, whereas only 25% of infections in subjects 3=45 years of age were due to meningococci. On the other hand, the relative incidence of S. pneumoniae did increase from 2% in the younger age group to 37% in the older subjects. L. monocytogenes caused 14% of cases among patients 3=45 years of age. The mean mortality was 19.1% and did not change significantly during the study period. A significant underlying illness or condition was present in 39% of the patients. During the first third of the study period penicillin or ampicillin alone or in combination with chloramphenicol were used as initial empiric therapy in 76% of cases, wheras during the last third of the period these agents were used initially in 24% of patients. The third generation cephalosporins either alone or in combination were instead employed for empiric treatment in almost two-thirds of the patients.Meningococci were the most common cause of bacterial meningitis in adults in Iceland during the study period, albeit age dependent, and causing only a fourth of infections in patients 3=45 years of age. Mortality did not change during the period. The third generation cephalosporins are now the most commonly used agents for empiric therapy.