The T-agglutination types were determined for a diverse collection of 1531 group A streptococci for which the 5' M protein gene (emm) sequences had been analysed. The majority of the T-agglutination types correlated with previously seen M/emm/T-type associations; however, several new associations were found. Analysis of a subset of this collection -which included 1157 clinical isolates with multiply encountered emm types -found that emm amplicon restriction profiles of isolates sharing identical T types and opacity factor phenotypes are useful for detecting groups of isolates with identical emrn genes. Many emrn genes of known 5' sequence display a highly conserved restriction pattern amongst clinical isolates widely separated both geographically and temporally.
The bfrA (Bordetella bmnchiseptica ferric iron repressed outer-membrane protein) gene was cloned from Bordetella bmnchiseptica by screening a library of TnphoA insertion mutants for iron-repressed fusions to phoA. The bfrA gene encoded an 80 kDa outer-membrane protein with a high level of amino acid sequence identity to several bacterial proteins belonging to the family of Ton B-dependent outer-membrane receptors. BfrA was especially homologous to Cir of Escherichia coli, lrgA of Vibrio cholerae and to three previously characterized ferric enterobactin receptors. DNA hybridization results indicated that bfrA was not present in other Bordetella species. Expression of the bfrA gene was induced by low iron availability from a promoter overlapped by a sequence resembling a consensus Fur-binding sequence, and bfrA expression was derepressed in a B. bmnchiseptica fur mutant. Utilization of the Bordetella siderophore alcaligin and the exogenous siderophore enterobactin was unaffected in bfrA mutants. Upon attempting to find the specificity of BfrA, 2,3-dihydroxybenzoylserine (DHBS) was shown to be utilized in a bfeA (Bordetella ferric enterobactin receptor gene)-dependent manner by B. bmnchiseptica and B. pertussis. In addition, the hydroxamate siderophores ferrichrome and desferrioxamine B, and the iron source haemin were shown to be utilized independently of bfeA and bfrA in B. bmnchiseptica and B. pertussis.
The variable 5 emm (M-protein gene) sequences and T-antigen types were determined from 340 systemic group A streptococcal (GAS) isolates taken from hospitalized patients in San Francisco, Calif.; Atlanta, Ga.; and Connecticut in 1994 and 1995. Eighty percent of these isolates had emm sequences and T-antigen types in agreement with previously recorded M-and T-antigen associations. Most of the remaining strains either were T nontypeable (11%) or contained emm genes encoding M proteins for which T-antigen associations have not been made (6%). One newly encountered emm gene, designated ST2974, from each of 13 isolates had the T type 8/25/Imp19. Another new emm gene, ST2967, from 8 of 11 isolates was T nontypeable. Six other unique emm gene sequences from seven isolates were encountered. Sequencing of the variable region of the emm gene of GAS isolates (emm typing) is effective for surveying the sequence variability of the M virulence protein, and combined with T typing, emm typing is useful for monitoring GAS strain diversity.
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