Anaerobic and Aerobic Culture
UFHPL Epic Test Name: CULTURE, WOUND
UFHPL Epic order code: LAB2007
In open wounds, anaerobic organisms may play an etiologic role, whereas aerobes may represent superficial contamination. Serious anaerobic infections are often due to mixed flora that are pathologic synergists. Anaerobes frequently recovered from closed postoperative wound infections include Bacteroides fragilis, 50 percent; Bacteroides melaninogenicus, 25 percent; Peptostreptococcus prevotii, 15 percent; and Fusobacterium sp, 25 percent. Anaerobes are seldom recovered in pure culture (10 to 15 percent of cultures).
Aerobes and facultative bacteria when present are frequently found in lesser numbers than the anaerobes. Anaerobic infection is most commonly associated with operations involving opening or manipulating the bowel or a hollow viscus (eg, appendectomy, cholecystectomy, colectomy, gastrectomy, bile duct exploration, etc.).
The ratio of anaerobes to facultative species is normally about 10:1 in the mouth, vagina, and sebaceous glands and at least 1000:1 in the colon. Biopsy culture is particularly useful in establishing the diagnosis of anaerobic osteomyelitis,2 clostridial myonecrosis, intracranial actinomycosis, and pleuropulmonary infections. Anaerobic infections of soft tissue include anaerobic cellulitis, necrotizing fasciitis, clostridial myonecrosis (gas gangrene), anaerobic streptococcal myositis or myonecrosis, synergistic nonclostridial anaerobic myonecrosis, and infected vascular gangrene. These infections, particularly clostridial myonecrosis, necrotizing fasciitis, and nonclostridial anaerobic myonecrosis, may be fulminant and are frequently characterized by the presence of gas and foul-smelling necrotic tissue.3 Empiric therapy based on likely pathogens should be instituted as soon as appropriate cultures are collected.
Clinical symptoms suggestive of anaerobic infection include:
- Foul-smelling discharge
- Location of infection in proximity to a mucosal surface
- Necrotic tissue, gangrene, pseudomembrane formation
- Gas in tissues or discharges
- Endocarditis with negative routine blood cultures
- Infection associated with malignancy or other process producing tissue destruction
- Septic thrombophlebitis
- Bacteremic picture with jaundice
- Infection resulting from human or other bites
- Black discoloration of blood-containing exudates (may fluoresce red under ultraviolet light in B melaninogenicus infections)
- Presence of “sulfur granules” in discharges (actinomycosis)
- Classical clinical features of gas gangrene
- Clinical setting suggestive for anaerobic infection (septic abortion, infection after gastrointestinal surgery, genitourinary surgery, etc)
- The specific site of the specimen;
- The age of patient;
- The current antibiotic therapy;
- The patient's clinical diagnosis; and
- The time of collection.
If an unusual organism is suspected, such as Actinomyces, this information must be specifically noted on the request form. Aspirates are preferable to swabs. A thin smear for Gram stain obtained from the same site is strongly recommended and must be ordered separately. Culture samples must be collected to avoid contamination with indigenous anaerobic flora from skin and mucous membranes. Because of resident anaerobic flora, the following sites are inappropriate for anaerobic cultures: throat and nasopharynx, sputum, bronchoscopy specimens, gastrointestinal contents, voided or catheterized urine, urogenital swabs (e.g., vaginal and/or cervical) and specimens from superficial wounds.
Type: Pus, tissue, or other material properly obtained from an abscess, biopsy, aspirate, drainage, exudate, lesion or wound. To ensure the proper growth of organisms, place swabs/specimen in a nanaerobic transporter. Do not refrigerate.
Sample Volume: Swab 0.5 mL pus or other fluid or tissue from an aspirated site. Ship specimens to the Lab in an anaerobic transporter.
- Under these conditions, aerobes and anaerobes will survive 24 to 72 hours when properly collected in the anaerobic transport tube.
- Ambient: Unstable
- Refrigerated: Unstable
- Frozen: 14 days
- Unlabeled specimen or name discrepancy between specimen and request label
- Specimen not received in appropriate anaerobic transport tube
- Swab not stored in oxygen-free atmosphere (any swab is suboptimal)
- Refrigerated specimens
- Specimen received after prolonged delay in transport (usually more than 72 hours)
- Note: Refrigeration inhibits viability of certain anaerobic organisms.
- Specimens from sites that have anaerobic bacteria as indigenous flora will not be cultured anaerobically
(e.g., throat, feces, colostomy stoma, rectal swabs, bronchial washes, cervical-vaginal mucosal swabs, sputa, skin and superficial wounds, voided or catheterized urine, ulcer surfaces, drainages onto contaminated surfaces).
- The isolation and identification (additional CPT coding of 87076, 87077, 87143 or other code, depending on the methods required) of potential anaerobic and aerobic pathogens
- Susceptibility testing if culture results warrant at an additional charge. CPT coding for microbiology and virology procedures often cannot be determined before the culture is performed.
Anaerobic and aerobic culture
Monday - Friday