Blood Culture (Anaerobic)

Aerobic blood culture bottles contain oxygenated medium to support growth of aerobic and facultative organisms; they’re incubated in an oxygen-rich environment. Anaerobic bottles contain reducing agents and are oxygen-free to support obligate anaerobes. Both are collected because some bacteria grow only under one condition; using paired aerobic and anaerobic bottles per draw increases detection and helps guide appropriate antimicrobial therapy.

The anaerobic blood culture bottle is the one labeled “anaerobic” (often marked AN). It contains reducing agents that remove oxygen to support growth of obligate anaerobic bacteria and is typically collected alongside an aerobic bottle during routine blood culture sampling. Use it when anaerobic infection is suspected; collect before antibiotics and follow your laboratory’s labeling and order-of-draw instructions.

Generally, draw the aerobic bottle first, then the anaerobic bottle. This order is standard for most peripheral venipunctures because the aerobic bottle tolerates exposure to oxygen and helps reduce contamination risk. Some collection systems or institutions may advise a different sequence—always follow your facility’s protocol or the microbiology lab’s instructions.

An anaerobic culture is performed to detect, isolate and identify bacteria that grow without oxygen from samples such as deep wounds, abscesses or sterile-site specimens. It confirms whether anaerobes are causing infection, enables species identification and antibiotic susceptibility testing, and guides targeted antimicrobial therapy, need for drainage, and overall clinical management.

Oxygen use: aerobic requires oxygen while anaerobic does not. Intensity/duration: aerobic is low–moderate intensity for longer periods; anaerobic is high intensity, short bursts. Energy pathways: aerobic uses oxidative phosphorylation; anaerobic uses ATP-PC and glycolysis. Byproducts: aerobic yields carbon dioxide and water; anaerobic produces lactate. Benefits: aerobic improves endurance and cardiovascular health; anaerobic builds strength and power.

Yes. Anaerobic bacteria such as Bacteroides, Clostridium and Fusobacterium can cause infections that progress to sepsis, especially after intra‑abdominal, pelvic, dental or necrotic soft‑tissue infections and abscesses. Diagnosis uses blood cultures and imaging; treatment requires prompt broad‑spectrum antibiotics with anaerobic coverage plus surgical or interventional source control to drain or remove infected tissue.