Polymorphism in Bordetella pertussis pertactin and pertussis
toxin virulence factors in the United States, 1935-1999.
Cassiday P, Sanden G, Heuvelman K, Mooi F, Bisgard KM, Popovic T.
Division for Bacterial and Mycotic Diseases, Centers for Disease Control and
Prevention, Atlanta, GA 30333, USA. PCassiday@cdc.gov. PCassiday@cdc.gov
To elucidate the potential role of the etiologic agent in recent increases of
pertussis incidence in the United States, we studied the polymorphism in
pertactin and pertussis toxin, which are Bordetella pertussis proteins important
for pathogenesis and immunity. We sequenced regions of their genes (prn and ptx)
in 152 B. pertussis strains isolated from 1935 through 1999 and identified 2 prn
sequences: prn1 (old), observed continuously since 1935, and prn2 (new), not
recognized until 1981 but seen in 97% of tested isolates in 1999. There were 3
ptx S1 subunit sequences: ptxS1D (old) was identified in 3 strains (1935 and
1939); ptxS1B (old) represented 87% of the strains recovered during 1935-1974;
and ptxS1A (new) was the most prevalent during 1975-1987 and 1989-1999 (64% and
78%, respectively). Potential association between vaccination and the observed
shift from old to new types requires further study. Our results provide the
basis for prospectively monitoring for changes among circulating B. pertussis
that might have epidemiologic relevance.
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