Comparison of Dey and Engley (D/E) neutralizing medium to Letheen medium and standard methods medium for recovery of Staphylococcus aureus from sanitized surfaces.

The ability of Dey and Engley (D/E) Neutralizing Medium to recover Staphylococcus aureus ATCC 6538 from tile surfaces exposed to a commercial phenol (Mikro-Bac) and a quaternary ammonium compound (Mikro-Quat) was compared to recovery with Letheen Medium. Standard Methods Medium was used as a control recovery medium. Organisms were exposed to both antimicrobials for varying time periods, then were recovered by swab and Rodac plate on both test media. The recovery by either procedure was significantly higher with Dey and Engley (D/E) Neutralizing Medium than with Letheen and Standard Methods Medium. The D/E Medium shows promise for evaluating antimicrobial chemicals used in environmental sanitation.

Methodology for recovery of chemically treated Staphylococcus aureus with neutralizing medium.

Recovery results of Staphylococcus aureus ATCC 6538 treated with phenolics and quaternary ammonium compounds on Dey and Engley (D/E) neutralizing medium at various time intervals were compared by the use of two commonly used media. Two recovery processes were utilized. In one, the chemically treated organisms were plated directly onto an agar medium. In the other, the aliquot was first put in broth and then was plated with agar. By either process, the numbers and the time period for recovery of organism were greater on D/E medium.

Typing methods for Proteus rettgeri: comparison of biotype, antibiograms, serotype, and bacteriocin production.

Two hunderd five strains of Proteus rettgeri from epidemic and nonepidemic sources were differentiated by a new biotyping scheme, agglutination in O antisera, antimicrobial resistance patterns, and a new scheme based on bacteriocin production. The P. rettgeri were divided into 10 groups by their fermentation of lactose, sucrose, D-mannitol, and salicin. These groups were then subdivided into 19 biotypes by other biochemical reactions. Bacteriocin production was tested by the cross-streak method. Thirty-four bacteriocin-sensitive indicator strains were evaluated, and 16 were selected for the final scheme and used to type the 205 P. rettgeri, which were divided into 15 bacteriocin types. Serologically, 43% of the P. rettgeri were O42, 13% were untypable, 4% were O15, and 3% each were O33, O64, and O84 in addition to 31 remaining serotypes. Strains of P. rettgeri from known outbreaks contained fewer biotypes, O groups, and bacteriocin types and were more resistant to antimicrobial agents than endemic strains. Strains with common patterns with all four marker systems were frequently associated with outbreaks. A strong correlation between multiple antibiotic resistance and bacteriocin production was shown.