Bacteraemia in the elderly

The aims of the study were to describe community-acquired and nosocomial bacteraemia in elderly patients and to determine the factors associated with increased mortality in these patients attending a tertiary hospital in Singapore. A consecutive series of 191 patients aged more than 60 years of age admitted in 1995 was studied retrospectively. All of them had positive blood culture results obtained from the Department of Pathology and the case notes were reviewed and entered into a standard clinical protocol. They were analysed for age, sex, place of origin, race, sites of infection, clinical parameters and bacteriology. The mean age of the study population was 75 years (SD = 8.9 years). Bacteraemia was acquired from the community in 57.5% of patients, 33% was nosocomial in origin and 9.5% acquired it in chronic long term care facilities. The common organisms cultured in community-acquired infections were Escherichia coli (26.1%), Klebsiella species (25.4%), Streptococcus species (11.1%), methicillin sensitive Staphylococcus aureus (7.6%) and Proteus mirabilis (4.8%). The common organisms cultured in nosocomial infections were Klebsiella species (19.8%), Enterobacter species (14.6%), E. coli (11.8%), Acinetobacter baumanii (9.2%), methicillin sensitive Staphylococcus aureus (7.9%) and methicillin-resistant Staphylococcus aureus (7.9%). Whilst most cases of bacteraemia were single organism cultures, 13.5% were polymicrobial. The common sources of bacteraemia were chest (27.5%), urinary tract (24.5%), skin (12.5), hepatic (8.8%), gut (4.3%), cardiovascular system (1%) and others (3.6%). In 12.5% of cases, the sources were multiple and in 5.3% of cases, the source could not be identified. Twenty-one per cent of patients with bacteraemia died. The following factors were associated with increased mortality rate: older age (median age of those that died was 78.5 years compared to survivors with a median age of 73 years, P = 0.011), patient's place of origin (patients in nursing home at higher risk of death, P = 0.04), patient's mobility status (immobile patients at higher risk, P = 0.00297), source of bacteraemia--respiratory infection at increased risk of death (P = 0.00009) but urinary tract infection had a better survival rate (P = 0.03935) and multiple sites of infection (patients with multiple sites of infection had higher risk, P = 0.00897). Methicillin-sensitive Staphylococcus aureus bacteraemia was associated with a mortality rate of 35.3%, followed by Klebsiella species 28.6%, Pseudomonas aeruginosa 28.6%, methicillin-resistant Staphylococcus aureus 25%, Proteus mirabilis 25% and E. coli 19.1%. Important clinical parameters which indicated a poor clinical outcome were: high pulse rate, hypotension, increased respiratory rate, low total white cell count, coagulopathy, hypoalbuminaemia and increased creatinine level.