In this study, tetracycline resistant Ureaplasma urealyticum(U.u.), Mycoplasma hominis(M.h.) and some other bacteria were isolated from clinical specimens ad tested for the tet M gene kon their chromosome or plasmid.
The 235 strais of mycoplasma sp. Were isolated from 694 clinical specimens and 17 strains kof M. h. and 16 strains of U.u., resistant to 120㎍ ml of tetracycline, were selected from 235 isolates. The 53 strains of tetracycline resistant bacteria
including 38 strains of #. Coli, 4 strains of P. aeruginosa, 3 strains of E. cloacae, 2 strains each of C. freundii and S. marcescens, 1 strain each of E. agglomerans, P. mirabilis. P. vulgaris and K. pneumoniae were isolated from clinical
specimens.
Plasmids and chromosomal DNAs were prepared from 17 strains of M.h. and 16 strains of U.u. by modified methods of Harasawa et al. and Hempstead et al. respectively. Plasmids from 53 strains of other bacteria were also prepared by a modified
method
of
Homles and Birnboim, from which chromosomal DNAs were obtained by method similar to Ausubel et al.
The fragments from plasmids and chromosomal DNAs digested by Hinc II were transferred from agarose gels to nitrocellulose papers by Southern blotting. To identify the fragments carring the tetracycline resistant determinant, we used 32P-labelled
tetM
gene from plasmid pJI3, which had been cloned into E. coli vector PACYC177. DNA-DNA hybridization was performed at 42℃ for 6 hours and autoradiograph was performed overnight.
Plasmid was not isolated from all of the U.u. and M.h. which show the tetracycline resistance. The chromosomal DNAs of 10 strains of M.h. and 9 strains of U.u. hybridized with the tetM gene probe. All of the chromosomal DNAs of tetracycline
resistant
other bacteria did not hybridize with the tetM gene probe. Out of 53 strains of tetracycline resistant some other bacteria, 30 strains hadplasmids. Of these 30 plasmids, 10 hybridized with tet M gene. These include plasmids from 6 strains of E.
coli,
one strain each of E. cloacae, C. freundii, E. agglomerans and K. pneumoniae.
These results suggest that the tetracycline resistant M.h. and U.u. contain the tetM gene on their chromosomal DNA. On the other hand, some other tetracycline resistant bacteria have the tetM gene on their plasmids.
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