Complete genome sequence of an M1 strain of Streptococcus pyogenes.

The 1,852,442-bp sequence of an M1 strain of Streptococcus pyogenes, a Gram-positive pathogen, has been determined and contains 1,752 predicted protein-encoding genes. Approximately one-third of these genes have no identifiable function, with the remainder falling into previously characterized categories of known microbial function. Consistent with the observation that S. pyogenes is responsible for a wider variety of human disease than any other bacterial species, more than 40 putative virulence-associated genes have been identified. Additional genes have been identified that encode proteins likely associated with microbial "molecular mimicry" of host characteristics and involved in rheumatic fever or acute glomerulonephritis. The complete or partial sequence of four different bacteriophage genomes is also present, with each containing genes for one or more previously undiscovered superantigen-like proteins. These prophage-associated genes encode at least six potential virulence factors, emphasizing the importance of bacteriophages in horizontal gene transfer and a possible mechanism for generating new strains with increased pathogenic potential.

Identification, cloning, and expression of the CAMP factor gene (cfa) of group A streptococci.

The CAMP reaction is a synergistic lysis of erythrocytes by the interaction of an extracellular protein (CAMP factor) produced by some streptococcal species with the Staphylococcus aureus sphingomyelinase C (beta-toxin). Group A streptococci (GAS [Streptococcus pyogenes]) have been long considered CAMP negative, and this reaction commonly has been used to distinguish GAS from Streptococcus agalactiae. We here provide evidence that GAS possess this gene and produce an extracellular CAMP factor capable of participating in a positive CAMP reaction. The S. pyogenes CAMP factor is specified by a 774-bp open reading frame homologous to the CAMP factor genes from S. agalactiae and Streptococcus uberis. This gene, designated cfa, was isolated on a 1,256-bp fragment and cloned in Escherichia coli. Recombinant clones of E. coli expressing cfa secreted an active CAMP factor. The deduced 28.5-kDa protein encoded by cfa consists of 257 amino acids, with a predicted 28-amino-acid signal peptide. The cfa gene is widely spread among GAS: 82 of 100 clinical GAS isolates produced a positive CAMP reaction. Of the CAMP-negative strains, 17 of the 18 GAS strains contained the cfa gene. Additionally, CAMP activity was detected in streptococci from serogroups C, M, P, R, and U. The cfa gene was cloned and actively expressed in Escherichia coli and gene fusions were made, placing the beta-galactosidase gene (lacZ) under control of the cfa promoter. These cfa promoter-lacZ fusions were introduced into S. pyogenes via a bacteriophage-derived site-specific integration vector where they showed that the cfa gene has a strong promoter that may be subject to as-yet-unidentified regulatory factors. The results presented here, along with previous reports, indicate that the CAMP factor gene is fairly widespread among streptococci, being present at least in groups A, B, C, G, M, P, R, and U.