Smooth and Rough Biotypes of Arcanobacterium haemolyticum Can Be Genetically Distinguished at the Arcanolysin Locus

Arcanobacterium haemolyticum is a Gram-positive, β-hemolytic emerging human pathogen that is classified into smooth or rough biotypes. This bacterial species is also a rare pathogen of animals. Smooth biotypes possess smooth colony edges, are moderate to strong in β-hemolysis, and predominately cause wound infections. In contrast, rough biotypes possess rough and irregular colony edges, have weak to no β-hemolytic activity, and predominately cause pharyngitis. Using horse erythrocytes we confirmed that smooth isolates are generally more hemolytic than rough isolates. A hemolysin from A. haemolyticum, arcanolysin (aln/ALN), was recently discovered and is a member of the cholesterol-dependent cytolysin (CDC) family. PCR amplification of aln from all 36 smooth A. haemolyticum isolates yielded the expected 2.0 kb product. While 21 rough isolates yielded the 2.0 kb product, 16 isolates had a 3.2 kb product. The extra 1.2 kb segment was 99% identical to IS911 (insertion sequence) from Corynebacterium diphtheriae. PCR amplification and sequence analysis of the upstream region of aln revealed ~40 nucleotide polymorphisms among 73 clinical isolates from Finland, Denmark, Germany and United States (Nebraska). Remarkably, multi-sequence alignments of the aln upstream region demonstrated that ~90% of the isolates phylogenetically clustered as either smooths or roughs. Differential restriction enzyme analysis of the aln upstream region also demonstrated that the aln upstream region of most (~75%) smooth isolates was cleaved with ClaI while this region in most (~86%) rough isolates was cleaved with XcmI. We conclude that the aln upstream region can be used to genetically distinguish between smooth and rough biotypes of this important emerging pathogen.