Host-Parasite Interactions

Question 1

Koch’s postulates

Answer 1

1) the microorganism must be present in every case of the infectious disease
2) the microorganism can be isolated in a pure culture
3) inoculation of the pure culture into animals produces a similar disease
4) the same species of microorganism must be recovered from the diseased animal

Question 2

Host

Answer 2

an animal (human) or plant on or in which a parasite or commensal organism lives

Question 3

Parasite

Answer 3

an organism that lives in or on an organism or another species (host) and derives nutrients at the other’s expense

Question 4

Pathogen

Answer 4

a microorganism capable of causing an infectious disease

Question 5

Primary pathogen

Answer 5

microorganism that regularly causes infection and disease when it enters a non-immune host

Question 6

Opportunistic pathogen

Answer 6

microorganism that rarely causes disease in healthy humans but may in a host whose defense mechanisms have been compromised or weakend

Question 7

Commensal (coloinization)

Answer 7

organism living in or on a host where neither derives benefit or harm

Question 8

Symbiosis

Answer 8

an organism living in or on a host where both derive mutual benefit

Question 9

Parasitism

Answer 9

an organism living in or on a host where the organism gains benefit at the expense of the host

Question 10

Infection

Answer 10

invasion and multiplication of microorganisms in or on a host; a disease process may or may not be present; it may cause an immune response; symptoms may be subclinical

Question 11

Virulence

Answer 11

the degree of pathogenicity and extent to which a microorganism can cause damage to the infected host (level of sickness it can cause)

Question 12

Carrier

Answer 12

an infectious host that, because of inherited genetic traits, either does not develop symptoms of disease or carrier it in a latent state

Question 13

Steps to chain of infection

Answer 13

1) reach host and find portal of entry
2) overcome host defenses
3) invade and proliferate in the host tissues; produce toxins or other virulence factors
4) be capable of resisting host defenses

Question 14

Microbiota

Answer 14

community of microbes that live in and on an individual

Question 15

Biofilm

Answer 15

an assemblage of microbial cells that adhere to a surface and enclose a matrix of primarily polysaccharide material (slime layer); help the bacteria resist antimicrobial agents

Question 16

Host defenses

Answer 16

microbiome throughout body, anatomic barriers (skin, fascia), cilia in respiratory tract, coughing and sneezing, mucus layer in gut, stomach acid, peristalsis, humoral substances (complement, opsonins), neutrophils and macrophages, antibodies

Question 17

Host factors leading to disease

Answer 17

behavior, occupation, age/genetic/sex, prior viral infections, foreign body, splenectomy, diabetes, hemato proliferative disorders, burns, steroid therapy, prior course of antibiotics, immunosuppressive drugs

Question 18

Microbial factors leading to disease

Answer 18

evade immune system, antibiotic cleaving, ability to attach (pili or fimbriae), can inhibit chemotaxis/phagocytosis, exotoxins, endotoxins, tissue tropism, excrete enzymes, hemolysins, coagulase

Question 19

Exotoxins

Answer 19

produced in cell and excreted

Question 20

Endotoxins

Answer 20

toxin derived from the cell wall of Gram-negative rods

Question 21

Tissue Tropism

Answer 21

ability to penetrate and survive within tissue excrete enzymes

Question 22

Disease Transmission: Endogenous sources

Answer 22

breaks in natural barriers (trauma, surgery, IV catheters), change in other host defense mechanisms

Question 23

Disease Transmission: Exogenous source

Answer 23

inhalation, ingestion, direct contact or inoculation, congenital, fomites, animal contact “zoonosis”, arthropod vector (malaria, typhus)

Question 24

Fomite

Answer 24

inanimate object such as hospital instrument or clothing; source of most nosocomial infections

Question 25

Nosocomial infection

Answer 25

infection acquired in a health-care setting

Question 26

Congenital

Answer 26

disease or condition present from birth; transplacental or in birth canal for infection

Question 27

Hemolysis

Answer 27

the break down of red blood cells