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2015 ; 83
(12
): 4750-8
Nephropedia Template TP
gab.com Text
Twit Text FOAVip
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English Wikipedia
The majority of 9,729 group A streptococcus strains causing disease secrete SpeB
cysteine protease: pathogenesis implications
#MMPMID26416912
Olsen RJ
; Raghuram A
; Cantu C
; Hartman MH
; Jimenez FE
; Lee S
; Ngo A
; Rice KA
; Saddington D
; Spillman H
; Valson C
; Flores AR
; Beres SB
; Long SW
; Nasser W
; Musser JM
Infect Immun
2015[Dec]; 83
(12
): 4750-8
PMID26416912
show ga
Group A streptococcus (GAS), the causative agent of pharyngitis and necrotizing
fasciitis, secretes the potent cysteine protease SpeB. Several lines of evidence
suggest that SpeB is an important virulence factor. SpeB is expressed in human
infections, protects mice from lethal challenge when used as a vaccine, and
contributes significantly to tissue destruction and dissemination in animal
models. However, recent descriptions of mutations in genes implicated in SpeB
production have led to the idea that GAS may be under selective pressure to
decrease secreted SpeB protease activity during infection. Thus, two divergent
hypotheses have been proposed. One postulates that SpeB is a key contributor to
pathogenesis; the other, that GAS is under selection to decrease SpeB during
infection. In order to distinguish between these alternative hypotheses, we
performed casein hydrolysis assays to measure the SpeB protease activity secreted
by 6,775 GAS strains recovered from infected humans. The results demonstrated
that 84.3% of the strains have a wild-type SpeB protease phenotype. The
availability of whole-genome sequence data allowed us to determine the relative
frequencies of mutations in genes implicated in SpeB production. The most
abundantly mutated genes were direct transcription regulators. We also sequenced
the genomes of 2,954 GAS isolates recovered from nonhuman primates with
experimental necrotizing fasciitis. No mutations that would result in a
SpeB-deficient phenotype were identified. Taken together, these data
unambiguously demonstrate that the great majority of GAS strains recovered from
infected humans secrete wild-type levels of SpeB protease activity. Our data
confirm the important role of SpeB in GAS pathogenesis and help end a
long-standing controversy.