CLINICAL MICRO - Host-Microbe Relationships

define symbiosis

both host and organism benefit and living together

define commensalism

organism benefit and no harm to the host

define parasitism

organism benefits at the expense of the host

define residential microbial site

organisms that colonize a site for a long duration (months/years)

define transient microbial site

organisms that are present at a site temporarily

which specie (normal flora) is the primary skin pathogen?

staphylococcus species

what is the predominate normal flora species in the mouth?

streptococcal species

what normal flora is predominantly in the upper respiratory tract?

viridans streptococci

what normal flora is predominantly found in the oropharynx (middle throat)?

alpha hemolytic / non-hemolytic streptococci

which flora species is predominantly found in the gastrointestinal (GI) tract (esophagus, stomach, intestine, colon)?

bacteroides species

define opportunists

usual flora that can cause diseases when any of the following occur:

1. damaged habitat/trauma

2. disturbed habitat

3. host immune system is weakened/compromised

define iatrogenic infection

infection that occurs from medical treatment/procedures

define pathogenicity

ability of a microbe to produce disease/damage in individual

define true pathogens

cause disease in healthy immunocompetent individuals

define virulence

the severity of disease in an infected host caused by an organism

define invasion

ability to penetrate and grow in a host tissue

define dissemination

spread from site of infection to distant organs/tissues

____ are proteins secreted/lysed by living bacteria into their environment and are heat labile (unstable)

exotoxins

______ are lipopolysaccharides bound to the outer cell wall (gram negative) that are released when the cell dies and is heat stable

endotoxins (think eNdo → gram Negative)

what are some routes of infection?

airborne, food & water, close contact/cuts/bites, arthropods & zoonoses (tick/flea & animals)

how does nutritional factors determine the composition of microbial flora?

how does pH determine the composition of the microbial flora?

how does oxidation-reduction potential determine the composition of the microbial flora?

how does resistance to antibacterial substances determine the composition of microbial flora?