Three oligonucleotide probes complementary to base sequences of the HLA-B variable region were used to probe clinical and foodborne isolates of Klebsiella spp. by DNA colony hybridization. One oligonucleotide (RR-3) corresponding to amino acid residues 66-74 of the HLA-B27.1 sequence and one corresponding to residues 66-74 of the HLA-B7 sequence (RR-5) hybridized with K. pneumoniae under conditions of high stringency. A genomic library was constructed using K. pneumoniae K43 chromosomal DNA, and a 1 kb PstI restriction fragment was found to contain the sequence associated with specific binding of the oligonucleotide probes. After purification and radiolabeling, the cloned fragment hybridized with 96.2% of the K. pneumoniae isolates by DNA colony hybridization. These results confirm the presence of sequence similarities between bacterial DNA and the MHC Class I variable region.