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Microbiology ` microbiology—basic bacteriology Microbiology ` microbiology—basic bacteriology SEcTioN ii 129

Spore-forming Some gram ⊕ bacteria can form spores A when Examples: B anthracis (anthrax), B cereus (food
bacteria nutrients are limited. Spores lack metabolic poisoning), C botulinum (botulism), C difficile

A activity and are highly resistant to heat and (pseudomembranous colitis), C perfringens
chemicals. Core contains dipicolinic acid. (gas gangrene), C tetani (tetanus).
Must autoclave to kill spores (as is done to
surgical equipment) by steaming at 121°C for
15 minutes.

Bacterial virulence
factors These promote evasion of host immune response.

Protein A Binds Fc region of IgG. Prevents opsonization and phagocytosis. Expressed by S aureus.
IgA protease Enzyme that cleaves IgA, allowing bacteria to adhere to and colonize mucous membranes. Secreted
by S pneumoniae, H influenzae type b, and Neisseria (SHiN).
M protein Helps prevent phagocytosis. Expressed by group A streptococci. Shares similar epitopes to human
cellular proteins (molecular mimicry); possibly underlies the autoimmune response seen in acute
rheumatic fever.

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