Enterococcus faecium isolated from 10 of 75 (13·3%) tenderloin beef samples were examined for resistance to selected antibiotics, presence of plasmids, and genetic diversity by random amplification of polymorphic DNA analysis. All strains showed multiple resistant to the antibiotics tested. Multiple antibiotic indexing of the vancomycin-resistant E. faecium strains showed that all (100%) originated from high risk contamination environments where antibiotics were often used. Plasmids ranging in size from 1·5 to 36 megadalton were detected in 15 of 19 (79%) strains. Thus, three plasmid profiles and eight antibiotypes were observed among the E. faecium strains. A high degree of polymorphism was obtained by combining the results of the two primers used; with the 19 E. faecium strains being differentiated into 19 RAPD-types. These preliminary results suggest that RAPD-PCR has application for epidemiologic studies and that resistance patterns and plasmid profiling could be used as an adjunct to RAPD for the typing of E. faecium in the study area.

R. SON, G. RUSUL, L. SAMUEL, YUHERMAN, S. SENTHIL, A. RASIP, E.H. NASRELDIN AND M. NISHIBUCHI. 1998. Four Vibrio cholerae O139 Bengal strains isolated from surface water were characterized by antibiotic resistance, plasmid profile, presence of cholera toxin gene and random amplification of polymorphic DNA (RAPD) analysis. All four strains exhibit multiple resistance towards the antibiotics tested with a multiple antibiotic resistance index of 0·5–0·66, and harboured a 2·0 MDa non‐conjugative plasmid. The Vibrio cholerae O139 Bengal were positive for the cholera toxin gene. Antibiotyping and random amplification of polymorphic DNA analysis with four primers proved to be useful in discriminating the isolates. RAPD proved to be more sensitive. These results reveal that there is significant genetic diversity among the Vibrio cholerae O139 Bengal strains studied.

A total of 35 Kanagawa-negative strains of Vibrio parahaemolyticus isolated from cockles (Anadara granosa) were investigated by randomly ampli®ed polymorphic DNA ®ngerprinting with three primers and their plasmid pro-®les. Eighteen strains carried small plasmid(s) of 2.4 to 7.3 kb that enabled the V. parahaemolyticus to be grouped into eight plasmid patterns. The three primers generated polymorphisms in all 35 strains of V. parahaemolyticus tested, producing bands ranging from 0.25 to 3.9 kb. The RAPD pro®les revealed a high level of DNA sequence diversity within the Vibrio parahaemolyticus strains tested, and that cockles in the study area are populated by genetically polymorphic strains of V. parahaemolyticus.