Multiple selective media for the isolation of anaerobic bacteria from clinical specimens.

Using fresh clinical material, a comparison of a number of anaerobic selective media was made. For Gram-negative anaerobes nalidixic acid tween agar (NAT), neomycin agar (NA), and neomycin-vancomycin agar (NVA) all performed equally well. Kanamycin-containing media were more inhibitory to all Gram-negative anaerobes other than Bacteroides fragilis and B. melaninogenicus. When the recovery of Gram-positive anaerobes was examined NAT performed better than any of the other selective media used. No single selective medium could recover all anaerobes. Better isolation was achieved using a combination of two selective media (the best combinations being NAT and NVA or NAT and NA). Only a combination of three selective media gave the maximum recovery of anaerobes in this study (NAT, NVA, and NA or KA).