TY - JOUR
T1 - Extracellular virulence factors in Bacillus cereus endophthalmitis
T2 - Methods and implication of involvement of hemolysin BL
AU - Beecher, D. J.
AU - Pulido, J. S.
AU - Barney, N. P.
AU - Lee Wong, A. C.
PY - 1995
Y1 - 1995
N2 - Bacillus cereus is a common cause of highly fulminant posttraumatic and metastatic endophthalmitis. Exotoxins or enzymes likely contribute to the severity of the infection, but specific virulence factors have not been identified. We developed two methods for the identification of B. cereus ocular virulence factors. In an in vitro assay that allows screening of multiple samples, retinal toxicity was estimated by measuring the release of lactate dehydrogenase from retinal buttons treated with B. cereus toxins. The results from this assay were confirmed with a sterile endophthalmitis model in which the histopathologic effect of intravitreally injected toxins was assessed. We tested pure hemolysin BL (HBL), a tripartite dermonecrotic vascular permeability factor of B. cereus, and crude exotoxin (GET) preparations, consisting of concentrated, cell-free B. cereus culture supernatant. In the in vitro assay, both GET and HBL caused rapid release of lactate dehydrogenase and retinal disintegration. In vivo, the toxins caused endophthalmitis clinically characteristic of B. cereus within 4 h. Histological changes included rapid retinal necrosis and detachment, choroidal edema, detachment and disruption of the retinal pigment epithelium, and rapid infiltration of polymorphonuclear leukocytes. Neutralization of HBL in CET preparations inhibited toxicity in vitro by 54%, and pure HBL was less toxic than CET with equal HBL contents in both methods. The results suggest that B. cereus ocular virulence is multifactorial and that HBL contributes to virulence.
AB - Bacillus cereus is a common cause of highly fulminant posttraumatic and metastatic endophthalmitis. Exotoxins or enzymes likely contribute to the severity of the infection, but specific virulence factors have not been identified. We developed two methods for the identification of B. cereus ocular virulence factors. In an in vitro assay that allows screening of multiple samples, retinal toxicity was estimated by measuring the release of lactate dehydrogenase from retinal buttons treated with B. cereus toxins. The results from this assay were confirmed with a sterile endophthalmitis model in which the histopathologic effect of intravitreally injected toxins was assessed. We tested pure hemolysin BL (HBL), a tripartite dermonecrotic vascular permeability factor of B. cereus, and crude exotoxin (GET) preparations, consisting of concentrated, cell-free B. cereus culture supernatant. In the in vitro assay, both GET and HBL caused rapid release of lactate dehydrogenase and retinal disintegration. In vivo, the toxins caused endophthalmitis clinically characteristic of B. cereus within 4 h. Histological changes included rapid retinal necrosis and detachment, choroidal edema, detachment and disruption of the retinal pigment epithelium, and rapid infiltration of polymorphonuclear leukocytes. Neutralization of HBL in CET preparations inhibited toxicity in vitro by 54%, and pure HBL was less toxic than CET with equal HBL contents in both methods. The results suggest that B. cereus ocular virulence is multifactorial and that HBL contributes to virulence.
UR - http://www.scopus.com/inward/record.url?scp=0028929005&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0028929005&partnerID=8YFLogxK
U2 - 10.1128/iai.63.2.632-639.1995
DO - 10.1128/iai.63.2.632-639.1995
M3 - Article
C2 - 7822032
AN - SCOPUS:0028929005
SN - 0019-9567
VL - 63
SP - 632
EP - 639
JO - Infection and Immunity
JF - Infection and Immunity
IS - 2
ER -