Increased Infectivity of Staphylococcus aureus in an Experimental Model of Snake Venom–Induced Tissue Damage
Departments of 1Microbiology, Tumor, and Cell Biology and 2Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden; 3Departamento de Bioquímica, Facultad de CCQQ y Farmacia, Universidad de San Carlos de Guatemala, Guatemala City, Guatemala; 4Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
Soft‐tissue infection is commonly found in patients bitten by Latin American Bothrops snakes. Staphylococcus aureus, which is not present in the mouth of the snake, is frequently isolated from these infections. The effects of B. asper venom on infection with S. aureus were analyzed in a model of infection in envenomated mouse gastrocnemius muscle. Inoculation of 50 colony‐forming units (cfu) of S. aureus was enough to cause infection in envenomated muscle, compared with >
cfu without venom. This effect was also achieved by injection of venom myotoxin III (an A2 phospholipase). A sarA mutant strain in which production of extracellular toxins and enzymes is up‐regulated and binding of fibronectin, fibrinogen, and other host proteins is down‐regulated was much less virulent than the corresponding parental strain, indicating that the ability of S. aureus to mask itself with host molecules might be more important than the effects of secreted toxins and enzymes in this kind of infection.
Received 28 November 2006; accepted 28 March 2007; electronically published 18 July 2007.
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Potential conflicts of interest: none reported.
Financial support: Swedish International Development Agency (as part of the NeTropica program); Swedish Research Council (grants 05969 to M.T., 12218 to J.‐I.F., and 4513 to S.A.).