Microbial Infection and Pathogenesis - Enzymes as Virulence Factors

5 important questions on Microbial Infection and Pathogenesis - Enzymes as Virulence Factors

Explain the two major ways bacterial pathogens damage host tissues and provide examples of each.

Bacterial pathogens damage host tissues by secreting tissue-destroying enzymes and by secreting or shedding toxins. For example, Streptococcus pyogenes produces streptokinase, an enzyme that dissolves fibrin clots, facilitating further invasion, while Staphylococcus aureus produces coagulase, promoting the formation of fibrin clots to protect the pathogen.

Describe the role of hyaluronidase in the virulence of certain bacteria. Provide an example of a bacterium that produces hyaluronidase.

Hyaluronidase is an enzyme that promotes the spreading of bacteria in tissues by breaking down the polysaccharide hyaluronic acid. Streptococci, staphylococci, and certain clostridia produce hyaluronidase. For instance, Streptococcus pyogenes secretes hyaluronidase to spread between host cells and attack subsurface tissues.

Discuss how fibrinolytic enzymes produced by certain pathogens impact the host's blood clotting mechanism. Provide an example of a pathogen and its fibrinolytic enzyme.

Fibrinolytic enzymes, such as streptokinase produced by Streptococcus pyogenes, dissolve fibrin clots, countering the host's blood clotting mechanism. This facilitates the pathogen's invasion. Streptokinase is also used medically to dissolve clots in conditions like heart attacks.
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Explain how some pathogens use enzymes to evade the host's immune defenses at mucosal surfaces. Provide an example of a bacterial species and its enzyme.

Certain pathogenic bacteria, like Neisseria species (e.g., N. gonorrhoeae), produce IgAases, enzymes that cleave the IgA antibodies present on mucosal surfaces. This enzymatic activity helps these bacteria evade the host's immune defenses by rendering secretory antibodies ineffective.

Discuss the dual role of enzymes produced by pathogens—offensive and defensive. Provide examples illustrating both offensive and defensive enzyme activities.

Pathogens produce enzymes as offensive weapons to destroy host tissues (e.g., hyaluronidase, collagenase) and as defensive weapons to destroy or inactivate host defenses (e.g., fibrinolytic enzymes, IgAases). Streptococcus pyogenes produces streptokinase as an offensive enzyme to dissolve fibrin clots, and Neisseria species produce IgAases as defensive enzymes to cleave IgA antibodies. Both strategies increase pathogen invasiveness.

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