Can we afford to do anaerobic cultures and identification? A positive point of view.

Because anaerobic bacteria cause significant human infections that require specific therapy and because anaerobes are resistant to certain antimicrobials, the isolation, identification, and determination of antimicrobial susceptibilities are as important for these bacteria as they are for other pathogenic bacteria. Anaerobic culturing can be made cost-efficient by strict adherence to several principles, including the selective culturing of only appropriate general specimens that are uncontaminated by normal flora (this can be achieved by educating physicians and nurses in recognizing likely sources of anaerobic infection); rapid transport of specimens and use of appropriate transport system; use of a system of rejection and notification when inappropriate or when multiple specimens have been received; and use of a logical algorithm for determining the degree of isolation and identification to be performed, according to the numbers and types of organisms present. Testing of all significant gram-negative organisms for the production of beta-lactamases can provide an early indication of antimicrobial susceptibility, and actual testing limited to screening of three or four drugs can be performed on selected isolates by using a rapid and simple method such as the Etest (AB BIODISK, Solna, Sweden). Although the number of anaerobic bacteremias has declined since the 1970s, this number has plateaued in recent years, and these infections are life-threatening. Routine culturing of blood for anaerobes is still indicated in many institutions because of the unpredictable clinical sources of some bacteremias and the improved yields of both anaerobes and some streptococci when anaerobic blood culture systems are used.