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.