NEUTRALIZATION OF ANTIMICROBIAL CHEMICALS BY RECOVERY MEDIA

The ability to neutralize a variety of antimicrobial agents by commercially prepared Dey and Engley (D/E) Neutralizing broth and the solid medium with a 2% agar was tested against the broth and the agar formulations of Letheen (LT) and Standard Methods (SM) medium. Paper disc assay of aqueous solutions of 1:50 phenol, 1:750 benzalkonium chloride (Zephiran(R)), 1:100 alkalinized glutaraldehyde (Cidex(R) 1:125 phenol (Mikro-Bac(R)), 1:128 quaternary ammonium compound (Mikro-Quat(R)) and tinctures of 1:1000 mercuric chloride (Merthiolate(R)) and 1:50 iodine did not inhibit Staphylococcus aureus ATCC 6538, Salmonella typhimurium ATCC 14028, Escherichia coli ATCC 25922, Bacillus subtilis ATCC 6633 and Pseudomonas aeruginosa ATCC 27853 growth on D/E agar. Except for 1:100 phenol and 1:128 Mikro-Bac on LT, all agents inhibited organism growth on LT and SM agar. In the presence of all test agents all test organisms grew in D/E broth. Except for 1:100 phenol and 1:128 Mikro-Bac in LT broth, all agents inhibited growth of test organisms in LT and SM broth. The recovery of viable organisms unable to grow in LT broth in the presence of test agents was better with D/E Agar than with LT and SM Agar. Both formulations of D/E medium show promise for studying and evaluating known and unknown compounds, mixtures and formulations of antimicrobial chemicals.