Preparation of ribonucleic acid probes specific for Bacteroides fragilis

Nucleic acid probes promise to be very useful in the detection of infectious agents. Several RNA probes have been developed by random cloning of chromosomal DNA for the detection of Bacteroides fragilis. Four such probes prepared by transcription of inserts of 400 bp, 800 bp, 2.4 kbp, and 6 kbp all hybridized to denatured B. fragilis DNA on nitrocellulose, but did not bind to DNA from a variety of other Bacteroides spp. or from selected aerobic strains. Each probe readily detected five clinical isolates of B. fragilis and did not react with 11 clinical isolates representing four other species in the "B. fragilis group".