Classifying Types of Bacterial Infections FREE

Bacteria entering the blood can cause serious problems called bloodstream infections (bacteremia). In the past, doctors classified bloodstream infections as community-acquired or nosocomial. Community-acquired infections occurred in otherwise relatively healthy outpatients. Nosocomial infections occurred in very sick hospitalized patients. Doctors chose antibiotic drugs on the basis of the two kinds of infections because different types of bacteria typically caused them. In the past decade, sicker patients with complicated illnesses such as cancer and kidney failure requiring dialysis are routinely cared for in outpatient settings. Bacteremia in these sicker outpatients may be more like nosocomial infections than like community-acquired infections.

To develop a more useful classification system for bloodstream infections.

504 adults with symptoms or signs of infection and positive blood cultures.

The researchers reviewed blood culture reports of hospitalized patients from one academic medical center and two community hospitals in North Carolina. They then reviewed medical records of patients with positive blood cultures to learn about symptoms, signs, and sites of infection and medical conditions and treatments. They placed the patients into one of three groups (community-acquired, health care–associated, and nosocomial) and compared infection and patient characteristics across groups. The nosocomial group first had positive blood cultures at least 48 hours after hospitalization for another problem. The health care–associated group had positive blood cultures at the time of or within 48 hours of hospitalization and had recently needed complicated care (nursing home and dialysis patients, patients recently hospitalized, and patients recently given medicine in a vein [intravenous] at home). The community-acquired group first had positive blood cultures at the time of or within 48 hours of hospitalization but did not fit criteria for a health care–associated infection.

Patients with community-acquired infections less often had cancer than patients in the other groups. The most common source of bloodstream infection differed by group: urinary tract infections in the community-acquired group and tubes inserted in veins to give treatment in the other groups. Two bacteria (Escherichia coli and Streptococcus pneumoniae) frequently caused community-acquired infections. Staphylococcus aureus frequently caused health care–associated and nosocomial infections. Bacteria resistant to antibiotics were infrequent with community-acquired infections. More patients with nosocomial infections (37%) died than patients with health care–associated (29%) and community-acquired (16%) infections.

The study was from one area in North Carolina. Patterns of health care and infections may vary in different areas. The definition of health care–associated infection was broad and included patients with different risks for infection.

Health care–associated bloodstream infections acquired in the outpatient setting are different from community-acquired bloodstream infections in relatively healthy people.