Ten broth media were evaluated for their ability to support the growth of low inocula of selected fastidious aerobic, microaerophilic, and anaerobic bacteria. Thioglycolate medium USP (Oxoid, Basingstoke, England), cooked meat broth (Oxoid), and fastidious anaerobe broth (Quelab Laboratories Inc., Montreal, Quebec, Canada) were best able to support the growth of the greatest variety of organisms at the lowest inoculum tested (10 1 CFU). In most cases, incubation of these broths resulted in visible turbidity within 3 days. These three broth media were found to be equally suitable for use as an enrichment broth in the clinical laboratory.The use of enrichment broth media is recommended in order to enhance the recovery of pathogenic microorganisms, especially those with more fastidious growth requirements, from clinical specimens (1,4,6). Many broth media are available for the isolation of bacteria, but few studies comparing their usefulness have been published (3,5,7,8). In the study described here, a variety of broth media were evaluated for their ability to support the growth of low inocula of common and fastidious microorganisms.The broth media that were prepared in house and dispensed in 15-ml aliquots included (i) brain heart infusion (BHI; Becton Dickinson Microbiology Systems, Cockeysville, Md.); (ii) BHI with BIO-X (BHI-Bio), a supplement for fastidious organisms (Quelab Laboratories, Inc., Montreal, Quebec, Canada); (iii) thioglycolate medium USP (THIO; Oxoid, Basingstoke, England); (iv) Wilkins-Chalgren anaerobe broth (WC; Oxoid); and (v) cooked meat broth, consisting of WC base and cooked meat pellets (CM; Oxoid). Broth media that were obtained commercially in either 8-or 10-ml aliquots included (i) BHI anaerobe broth with 5% sheep blood (BHI-B; Quelab Laboratories, Inc.); (ii) fastidious anaerobe broth (FAB; Quelab Laboratories, Inc.); (iii) cooked meat enriched broth (CM-EB; Quelab Laboratories, Inc.); (iv) Schaedler broth (SB; Carr-Scarborough Microbiologicals, Inc., Stone Mountain,
