Commensalism vs. Parasitism

a man who had been asymptomatically carrying Staph aureus on his skin develops an infection after he burns his hand — which assumption of the commensal relationship was violated?

containment in proper compartment

what term refers to the relationship when organism 1 benefits and organism 2 also benefits?

mutualism

what term refers to the relationship when organism 1 benefits and organism 2 neither benefits nor is harmed?

commensalism

what term refers to the relationship when organism 1 benefits and organism 2 is harmed?

parasitism

what term refers to when there are fewer nutrients and physical locations for pathogens (specifically commensals) to set up residence?

• important element of innate immunity

colonization resistance

which type of pathogen very unlikely to cause disease with very low pathogenicity, high ID50, and very high LD50?

nonpathogen

which type of pathogen unlikely to cause disease unless host is debilitated, low pathogenicity, mid-low ID50, and high LD50?

opportunistic pathogen

what is the dose of bacteria necessary to infect 50% of the population called?

ID50

what is the dose of bacteria necessary to kill 50% of the population called?

LD50

what term refers to something that routinely causes disease in previously-healthy hosts, mid-high pathogenicity, low ID50, and mid-low LD50?

pathogen

a bacterium that has a very low pathogenicity and a high infectious dose is most likely a ____

nonpathogen

a bacterium that has a mid to low pathogenicity and a low infectious dose is most likely a ____

opportunistic pathogen

what normal flora commensal are on the skin?

S. epidermis and C. albicans

which normal flora commensal are in the throat?

staph and strep

which normal flora commensal is in the gut?

coliforms

which normal flora is a symbiote in the vagina?

lactobacilli

which normal flora is a symbiote in the gut?

nutrient-generating bacteria

what are the assumptions of the commensal relationship?

• containment in appropriate compartment

• immunocompetent host

• balance among commensal organisms

what are genes called that are experimentally necessary for a pathogen to produce disease?

virulence factors

what is the term for a group of several virulence factors that are regulated together and often transferred horizontally?

pathogenicity island

on what kind of DNA are virulence factors often encoded and transferred between bacteria?

accessory DNA

what are the secreted polypeptides, sometimes injected by T3SS, that can cause profound toxicity?

exotoxins

what is the heat- or chemically-inactivated exotoxin often used as a vaccine?

toxoid

in an A-B subunit exotoxin, which subunit is responsible for the toxic activity

A

in an A-B subunit exotoxin, what is the role of the B subunit?

to deliver A

what type of toxins are an intrinsic part of the bacterial surface and cause immunogenic symptoms?

endotoxins

can previous exposure or vaccination provide protection against endotoxins?

no

what are the five steps of Koch’s postulates?

• observe disease

• culture pathogen

• infect new host

• observe same disease

• culture same pathogen