Rapid Differentiation of “ Mycobacterium canettii ” from Other Mycobacterium tuberculosis Complex Organisms by PCR-Restriction Analysis of the hsp65 Gene

Abstract

ABSTRACT A total of 102 isolates of the Mycobacterium tuberculosis complex, including available “ M. canettii ” isolates, were studied by PCR-restriction analysis of a 441-bp fragment of the hsp65 gene. PRA upon Hha I enzyme digestion (GCGC) allowed easy differentiatiation of “ M. canettii ” from other members of the M. tuberculosis complex (three bands of 260, 105, and 60 bp for “ M. canetti ,” compared to four bands of 185, 105, 75, and 60 bp for other members of the M. tuberculosis complex). Sequencing of the 441-bp hsp65 fragment of “ M. canettii ” isolates showed the disappearance of an Hha I site at position 235 due to a C-to-T transition that corresponded to position 631 of the homologous hsp65 gene of M. tuberculosis H37Rv. Considering that “ M. canettii ” may also exist as a stable rough morphotype, we suggest that the true number of “ M. canettii ” isolates may be underestimated in clinical microbiology laboratories.