Epidemiology and virulence gene expression of intracellular group A streptococci in tonsils of recurrently infected adults.

Intracellularly persistent group A streptococci (GAS, Streptococcus pyogenes) have been associated with recurrent tonsillopharyngitis and antibiotic treatment failure. As a supplementation of the published in vitro data, conventional bacteriology and molecular epidemiology was performed on material from 29 adult patients of a German army hospital with anamnestic signs of recurrent tonsillopharyngitis. Pre-surgery tonsil swabs and the surgically removed tonsils were examined with respect to growth of aerobic bacteria in absence and presence of antibiotics with exclusively extracellular activity. Under such antibiotic selection, Staphylococcus aureus and GAS were cultured from specimens of 13 and 3 patients, respectively. In every material GAS-positive by culture methods, the intracellular location of the penicillin-susceptible GAS isolates was confirmed by immunohistologic examination of tonsillar sections using a GAS-specific IgG antibody. The three intracellular GAS isolates were typed by emm gene sequencing and could be associated to types M6 and M49 (two isolates). The bacteria were serially passaged on sheep blood agar, and semiquantitative mRNA analysis from virulence genes was performed using bacteria of the 4th and 25th passage after isolation. An M-type-specific pattern of virulence gene expression and different gene expression levels in relation to the passage number were observed.

Divergent intron conservation in the mitochondrial nad2 gene: signatures for the three bryophyte classes (mosses, liverworts, and hornworts) and the lycophytes.

The slow-evolving mitochondrial DNAs of plants have potentially conserved information on the phylogenetic branching of the earliest land plants. We present the nad2 gene structures in hornworts and liverworts and in the presumptive earliest-branching vascular land plant clade, the Lycopodiopsida. Taken together with the recently obtained nad2 data for mosses, each class of bryophytes presents another pattern of angiosperm-type introns conserved in nad2: intron nad2i1 in mosses; intron nad2i3 in liverworts; and both introns, nad2i3 and nad2i4, in hornworts. The lycopods Isoetes and Lycopodium show diverging intron conservation and feature a unique novel intron, termed nad2i3b. Hence, mitochondrial introns in general are positionally stable in the bryophytes and provide significant intraclade phylogenetic information, but the nad2 introns, in particular, cannot resolve the interclade relationships of the bryophyte classes and to the tracheophytes. The necessity for RNA editing to reconstitute conserved codon entities in nad2 is obvious for all clades except the marchantiid liverworts. Finally, we find that particularly small group II introns appear as a general feature of the Isoetes chondriome. Plant mitochondrial peculiarities such as RNA editing frequency, U-to-C type of RNA editing, and small group II introns appear to be genus-specific rather than gene-specific features.

Group A streptococcal RofA-type global regulators exhibit a strain-specific genomic presence and regulation pattern.

RofA-like protein (RALP) type regulators have been shown to exist in different forms in group A streptococci (GAS) and to regulate the expression of important bacterial adhesins. This study shows that the vast majority of strains from different GAS M serotypes carried a rofA virulence regulator gene in their genome and that this gene could be detected in combination with other RALP genes and RALP-dependent adhesin genes in a strain-specific manner. The gene encoding the Nra regulator was predominantly found in opacity factor (OF)-negative serotypes. When analysing a rofA mutant in a serotype M2 strain, the strain specificity was also found in the positive and negative regulatory functions of RALP genes as well as in the type and number of virulence genes and functions controlled by the RALP genes. Of 17 virulence-associated genes tested, only one, the putative streptolysin S gene, was observed to be derepressed in RALP mutants of three different GAS serotype strains. This strain-specific variability of RALP regulon sizes is associated with different patterns of host cell attachment and internalization. In addition, RofA2 was shown to control expression of the ribosomal protein gene rpsL. As a consequence, it was demonstrated for the first time in streptococci that aminoglycoside resistance mediated by rpsL expression is apparently controlled by a virulence gene regulator.