A site for blood culture collection can typically be cleaned with which of the following?

Sepsis, meningitis osteomyelitis, septic arthritis, bacterial pneumonia

Two sets of cultures—one from each of two prepared sites, the second drawn after a brief time interval, then begin therapy.

Assure sufficient sampling in cases of intermittent or low level bacteremia. Minimize the confusion caused by a positive culture resulting from transient bacteremia or skin contamination.

Fever of unknown origin (eg, occult abscess, empyema, typhoid fever, etc)

Two sets of cultures—one from each of two prepared sites, the second drawn after a brief time interval (30 minutes). If cultures are negative after 24 to 48 hours obtain two more sets, preferably prior to an anticipated temperature rise.

The yield after four sets of cultures is minimal. A maximum of three sets per patient per day for three consecutive days is recommended.

Endocarditis

Acute

Obtain three blood culture sets within two hours, then begin therapy.

95% to 99% of acute endocarditis patients (untreated) will yield a positive in one of the first three cultures.

Subacute

Obtain three blood culture sets on day one, repeat if negative after 24 hours. If still negative or if the patient had prior antibiotic therapy, repeat again.

Adequate sample volume despite low level bacteremia or previous therapy should result in a positive yield.

Immunocompromised Host (eg, AIDS)

Septicemia, fungemia mycobacteremia

Obtain two sets of cultures from each of two prepared sites; consider lysis concentration technique to enhance recovery for fungi and broth systems for recovery of mycobacteria.

Low levels of fungemia and mycobacteremia frequently encountered.

Previous Antimicrobial Therapy

Septicemia, bacteremia; monitor effect of antimicrobial therapy

Obtain two sets of cultures from each of two prepared sites; increased volume >10 mL/set.

Recovery of organisms is enhanced by dilution and increased sample volume.

*Adapted from Flournoy DJ, Adkins L. Understanding the blood culture report. Am J Infect Control. 1986 Feb; 14(1):41-46.

Virtually any organism, including normal flora, can cause bacteremia.

A negative culture result does not necessarily rule out bacteremia; false-negative results occur when pathogens fail to grow.

A positive culture result does not necessarily indicate bacteremia; false-positive results occur when contaminants grow.

Gram-negative bacilli, anaerobes, and fungi should be considered pathogens until proven otherwise.

The most difficult interpretation problem is to determine whether an organism that is usually considered normal skin flora is a true pathogen.