Isolation and identification of anaerobic bacteria

Anaerobic bacteria make up a predominant part of the normal human flora. Adequate specimen collection must avoid contamination with this flora. Suitable methods include thoracentesis, transtracheal aspiration, needle and syringe aspiration of closed abscesses, and endocervical aspiration of intrauterine pus. Swabs are generally unsuitable. Sputum, voided urine, vaginal secretions, and specimens contaminated with feces are not cultured anaerobically. Specimens should be transported in an oxygen-free container. There are several efficient methods for culturing anaerobes, including the simple and inexpensive GasPak jar. The average clinical laboratory may not be able to afford the time, personnel, and equipment necessary for complete identification of all anaerobes isolated. However, the identification of certain ones, including Bacteroides fragilis and Clostridium perfringens, is relatively simple. Primary emphasis should be placed on the rapid recognition of the presence of obligate anaerobes in a culture and the immediate reporting of all available information to the clinician. Subsequent reports can provide as complete an identification as is possible for each laboratory.