Rapid isolation and detection of Escherichia coli O157:H7 by use of rainbow agar O157 and PCR assay.

This study has evaluated the use of a commercially available Rainbow agar O157 and polymerase chain reaction (PCR) assays for the detection of Shiga-like toxin producing Escherichia coli and to serotype E. coli O157:H7 from raw meat. The Rainbow agar O157 was found to be selective and sensitive for the screening of the E. coli O157 from artificially and naturally contaminated meat samples. Shiga-like toxin producing E. coli were identified with two primer pairs that amplified fragments of the SLT-I (384 bp) and SLT-II (584 bp). E. coli O157:H7 was serotyped with a primer pair specified for the H7 flagellar gene, which amplify specific DNA fragments (625 bp) from all E. coli O157:H7 strains. The use of Rainbow agar O157 described allows for the presumptive isolation of E. coli O157 in 24 hours. Identification and confirmation of the presumptive isolates as E. coli O157:H7 by PCR assays require additional 6-8 hours. The above-mentioned screening and identification procedures should prove to be a very useful method since it allows for the specific detection of E. coli O157:H7.

Genotypic and phenotypic relationship in Burkholderia pseudomallei indicates colonization with closely related isolates.

Seven isolates of Burkholderia pseudomallei from cases of melioidosis in human (2 isolates) and animal (2 isolates), cat (one isolate) and from soil samples (2 isolates) were examined for in vitro sensitivity to 14 antimicrobial agents and for presence of plasmid DNA. Randomly amplified polymorphic DNA (RAPD) analysis was used to type the isolates, using two arbitrary primers. All isolates were sensitive to chloramphenicol, kanamycin, carbenicillin, rifampicin, enrofloxacin, tetracycline and sulfamethoxazole-trimethoprim. No plasmid was detected in all the isolates tested. RADP fingerprinting demonstrated genomic relationship between isolates, which provides an effective method to study the epidemiology of the isolates examined.