[Blood culture results in elderly febrile patients]

We retrospectively evaluated blood culture results in elderly patients (≥65 years) with a fever due to infection.

We examined the bacteria isolated from blood cultures and compared them to bacteria detected in infected lesions that caused bacteremia. We compared the types of bacteria isolated in the two groups (the community-acquired group and the hospital-acquired group).

Blood cultures were obtained from 638 patients. Bacteria were detected in 182 patients (28.5%), including 66 (36.3%) patients in the community-acquired group and 116 (63.7%) patients in the hospital-acquired group. There were 259 positive samples (25.1%). In arterial blood specimens, 153 (30.9%) samples were positive, while in venous blood specimens, there were 106 (19.8%) positive samples (P<0.001). In the community-acquired group, the most common bacteria identified were E. coli compared to S. epidermidis in the hospital-acquired group. More than 50% of the bacteria identified in the blood cultures were of the same species identified in the respective urine samples and central venous catheter tips.

The bacteria detection rate in this study was 28.5% for blood cultures, which is higher than the 17.5% reported by the Japan Nosocomial Infections Surveillance Program conducted by the Japanese Ministry of Health, Labour and Welfare. These results suggest that in elderly patients from whom an insufficient volume of blood can be drawn from a vein, an arterial sample may increase the detection rate. A high percentage of bacterial species isolated from the blood cultures was also detected in urinary tract infections and central venous catheter-related infections, indicating that a blood culture is useful for detecting various infectious diseases, even in elderly febrile patients.