Biomedical subjects
Publications and source records attributed to Yoshiyuki Ozawa.
Of 1,456 strains isolated from 2001 to 2003 demonstrating resistance to either oxyimino-cephalosporin, 317 strains, isolated in 57 of 132 clinical facilities, were found to harbor bla(CTX-M) genes by PCR. Fifty-seven, 161, and 99 strains harbored bla(CTX-M) genes belonging to the bla(CTX-M-1), bla(CTX-M-2), and bla(CTX-M-9) clusters, respectively.
The Enterococcus faecalis plasmid pAM373 (36.7kb) encodes a mating response to the sex pheromone cAM373 secreted by recipient (plasmid-free) bacteria. Like certain other conjugative enterococcal plasmids, a key regulator of the pheromone response is a negatively acting protein, TraA, which is believed to interact with internalized pheromone to influence expression from a key transcriptional promoter P(0). An earlier report showed that in the case of pAM373 most, but not all, transposon-insertion mutations in traA differed from those in the case of pAD1 and pCF10 in that they did not give rise to the normally characteristic constitutive clumping. We show here that this phenomenon relates to a host effect involving an RpoB-related mutation associated with rifampin resistance. When harboring traA mutants, rifampin-sensitive hosts exhibited constitutive clumping, whereas rifampin-resistant hosts did not-despite the fact that the latter host exhibited a normal pheromone-inducible clumping response when harboring a wild-type plasmid. The data imply that TraA normally remains associated with the transcription complex after induction. In addition the promoter of traA, designated P(a), was shown to be located about 600bp upstream of the translational start site, as clones containing traA required this site to complement traA mutants in trans. Transcription from P(a) also gave rise to a short (130 nt) transcript, mD, expressed at a high level in uninduced cells. An earlier observation suggesting that TraA negatively affected transcriptional readthrough into the 3' end of traA from the t(ac) intrinsic bidirectional terminator between traA and the opposing, adjacent traC was supported by TraA complementation studies. Evidence is also presented suggesting that this regulation at t(ac) also involves an additional, possibly cis-acting, element.
Explore the source record for details and available documents.
Vancomycin-resistant Enterococcus faecalis coisolated with vancomycin-resistant (VanA) Staphylococcus aureus was found to contain two plasmids, designated pAM830 (45 kb) and pAM831 (95 kb). pAM830, found to be conjugative and closely related to the Inc18 family of broad-host-range conjugative plasmids, encodes resistances to vancomycin (via a Tn1546-like element) and erythromycin; pAM831 encodes resistances to gentamicin, streptomycin, and erythromycin.
The phenotypes and genotypes of 22 VanA-type vancomycin-resistant enterococci that had been isolated in Japan were examined. The VanA resistance determinant was plasmid mediated in each of the 22 strains. Of the 22 strains, 8 were isolated from different patients and 11 and 3 were obtained from different samples of chickens imported from Thailand and France, respectively. Three of the strains that were isolated from patients and the 11 strains isolated from the Thai chickens showed high-level vancomycin resistance (MICs, 512 to 1,024 micro g/ml) and low-level teicoplanin resistance (MICs, 0.5 to 4 micro g/ml). Each of these strains had three amino acid substitutions in the N-terminal region of the deduced VanS sequence. L50 was converted to V, E54 was converted to Q, and Q69 was converted to H compared to the vanS gene sequence of Tn1546.