Anaerobic Culture

Anaerobic Culture

Number
	008904
CPT
	87075
Related Information
	Default Test Order for Ambiguous Orders Susceptibility Testing, Anaerobic Bacteria
Synonyms
	Anaerobic Culture, Abscess ; Anaerobic Culture, Body Fluid ; Anaerobic Culture, Wound ; Culture, Anaerobic ; Wound Anaerobic Culture
Test Includes
	Culture; isolation and identification of potential anaerobic pathogens (additional charges/CPT code[s] may apply); susceptibility testing [180349] if culture results warrant (additional charges/CPT code[s] may apply). CPT coding for microbiology and virology procedures often cannot be determined before the culture is performed. Requests with only a written order and no test number indicated will be processed according to Default Test Order for Ambiguous Orders .
Special Instructions
	Gram stain [008540] is recommended with all anaerobic cultures (additional charge). The request form must state specific site of specimen, age of patient, current antibiotic therapy, clinical diagnosis, and 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 (eg, vaginal and/or cervical), and specimens from superficial wounds.
Specimen
	Pus, tissue, or other material properly obtained from an abscess, biopsy, aspirate, drainage, exudate, lesion, or wound. To ensure proper growth of organisms place swabs/specimen in anaerobic transporter. Do not refrigerate.
Volume
	Swab in anaerobic transporter or 0.5 mL pus, other fluid or tissue from aspirated site in anaerobic transporter
Container
	Anaerobic transport or aerobic/anaerobic bacterial swab transport containing gel preservative
Collection
	Some anaerobes will be killed by contact with molecular oxygen for only a few seconds. Overlying and adjacent areas must be carefully disinfected to eliminate contamination with indigenous flora. Ideally, pus or other fluid obtained by needle aspiration through intact skin or mucosal surface that has been cleaned with antiseptic should be collected. Sampling of open lesions is enhanced by deep aspiration using a sterile plastic catheter. Curettings of base of an open lesion are optimal. If irrigation is necessary, nonbacteriostatic sterile normal saline may be used. Lower respiratory samples must be obtained by transtracheal percutaneous needle aspiration, transbronchial biopsy, transthoracic needle biopsy, or open lung biopsy by physicians trained in these procedures. If swabs must be used, collect two, use one for Gram stain and one for culture. Anaerobic transports must be used for swabs and for aspirates. Specimens are to be collected from a prepared site using sterile technique. Contamination with normal flora from skin, rectum, vaginal tract, or other body surfaces must be avoided.
Storage Instructions
	Specimens for anaerobic culture should be maintained at room temperature. Under these conditions anaerobes will survive 24-72 hours when properly collected in the anaerobic transport tube.
Patient Preparation
	Sterile preparation of the aspiration site is imperative.
Causes for Rejection
	Unlabeled specimen or name discrepancy between specimen and request label; specimen that is not received in appropriate anaerobic transport tube; expired transport; swab that has not been stored in oxygen-free atmosphere (any swab is suboptimal); specimen refrigerated. Note: Refrigeration inhibits viability of certain anaerobic organisms. If an unacceptable specimen is received, the client will be notified and another specimen will be requested before disposal of the original specimen. Specimens from sites that have anaerobic bacteria as indigenous flora will not routinely be cultured anaerobically (eg, 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).
Use
	Isolate and identify anaerobic pathogenic organisms; determine susceptibility of isolates (extra charge). When actinomycetes are suspected a specific request must be made. Anaerobic cultures are indicated particularly when suspected infections are related to gastrointestinal tract, pelvic organs, associated with malignancy, related to use of aminoglycosides; or occur in a setting in which the diagnosis of gas gangrene or actinomycosis is considered. Anaerobic culture is especially indicated when an exudate has a foul odor or if the exudate has a grayish discoloration and is hemorrhagic. Frequently, more than one organism is recovered from an anaerobic infection.
Limitations
	The only sources for specimens with established validity for meaningful anaerobic culture in patients with pleuropulmonary infections are blood, pleural fluid, transtracheal aspirates, transthoracic pulmonary aspirates, and specimens obtained at thoracotomy. Pleural fluid is preferred for patients with empyema.¹ Blood cultures yield positive results in <5% of cases of anaerobic pulmonary infection. Specimens received in anaerobic transport containers are not optimal for aerobic fungus cultures. Mycobacterium sp or Nocardia sp, which may cause abscesses, will not be recovered even if present, since extended incubation periods, aerobic incubation, and special media are necessary for their isolation. Cultures for these organisms should be specifically requested, and a separate specimen submitted.
Methodology
	Anaerobic culture
Contraindications
	Bronchoscopically obtained specimens are not ideal as the instrument becomes contaminated by organisms normally contaminating the oropharynx during insertion. Culture of specimens from sites harboring endogenous anaerobic organisms or contaminated by endogenous organisms may be misleading with regard to etiology and selection of appropriate therapy.
Additional Information
	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, which are pathologic synergists. Anaerobes frequently recovered from closed postoperative wound infections include Bacteroides fragilis, approximately 50%; Bacteroides melaninogenicus, approximately 25%; Peptostreptococcus prevotii, approximately 15%; and Fusobacterium sp, approximately 25%. Anaerobes are seldom recovered in pure culture (10% to 15% 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) See table in Anaerobic and Aerobic Culture and Gram Stain [183111] .
Footnotes
	Bartlett JG, “Anaerobic Bacterial Infections of the Lung,” Chest, 1987, 91(6):901-9. Hall BB, Fitzgerald RH Jr, and Rosenblatt JE, “Anaerobic Osteomyelitis,” J Bone Joint Surg Am, 1983, 65(1):30-5. Finegold SM, George LW, and Mulligan ME, “Anaerobic Infections Part II,” Dis Mon, 1985, 21(11)