Sequence Analysis of the Variable Number Tandem Repeat in Staphylococcus aureus Protein A Gene - Bacterial Pathogenesis: Methods and Protocols - page 270

TIGR-F TIGR-R

X r

A.

polymorphic X region

B.

Fig. 1. (A) Protein A gene organization. Boxes indicate segments of the gene
coding for the signal sequence (S); the immunoglobulin G-binding regions (A-D);
a region homologous to A-D (E); and the polymorphic X region, which includes
(Xr) the variable spa repeat region, shaded in alternating segments and (Xc) the cell
wall attachment sequence. Locations of primers described in the “Methods” section
are also shown (50) . (B) Nucleotide sequence of Staphylococcus aureus USA300-
FPR3757 protein A gene (SAUSA300_0113) showing locations of spa type 1 repeats
and sequencing primers referred to in “Methods” section. Alternating repeats, are
highlighted as in the Xr region in Fig. 1(A) . Individual repeats are named according to
eGenomics database nomenclature.

concordant results; however, spa typing was more discriminating, and the
smaller amplicon sizes were more amenable to single sequencing runs (10,20) .
The variance in discriminatory power between spa and coa is largely attributed
to the evolutionary rate of the specific genetic locus, consistent with the obser-
vation that the level of discrimination afforded by VNTR analysis is propor-
tional to the molecular “clock-speed” of the target (21) .
As epidemiologically related isolates are typically considered descendants
of a common precursor cell, outbreak investigations of S. aureus and other
pathogens are viewed as short-term events or cases of local epidemiology that