Pathology 2-3: Host Parasite Relationship 1 & 2

Question 1

List the 4 microorganism relationships? And what do they do?

Answer 1

1- symbiosis: 2 organisms living together.
2- commensalism: microorganism benefits while host is not harmed.
3- mutualism: microorganism and host benefit.
4- parasitism: microorganism benefits while the host is harmed.

Question 2

List the 3 types of microbial flora?

Answer 2

1- indigenous (normal) flora: microorganisms commonly found on or in healthy persons.
2- resident flora: microorganisms that colonize an area for months or years.
3- transient flora: microorganisms temporarily colonizing a host.

Question 3

Definition: condition of hosts capable of transmitting the infection.

Answer 3

Carrier state.

Question 4

Composition of microbial biota is influenced by what?

Answer 4

Specific nutritional and environmental factors.

Question 5

The affinity of microorganisms for a specific site depends on what?

Answer 5

The ability of the organisms to resist the antibacterial effects of: bile, lysozyme, fatty acids.

Question 6

List the environmental factors that affect composition of microbial biota?

Answer 6

1- moist or dry: most microorganism live in moist areas (skin folds).
2- low pH: female genital tract, GI tract of breast-fed infants.
3- gaseous atmosphere: low oxidation/reduction potential.

Question 7

Microbial infections are common in which type of patients?

Answer 7

Immunocompromised patients.

Question 8

List the properties of the normal biota of the skin?

Answer 8

• generally superficial organisms: skin surface and hair follicles.
• apocrine sweat glands: secrete substances metabolized by bacteria, release of odorous amines.
• normal flora: colonize skin surface, prevent pathogens from colonizing.

Question 9

List common resident microorganisms found on the skin?

Answer 9

1- candida spp.
2- staphylococcus spp.
3- diphtheroids (corynebacterium spp.).

Question 10

List the properties of the normal biota of the oral cavity (mouth)?

Answer 10

• bacterial plaque may develop on teeth.
• low oxidation reduction potential; anaerobes grow.
• buccal mucosa and tooth surface; production of acids by microorganisms, tooth decay.

Question 11

List common resident microorganisms found on the mouth?

Answer 11

1- streptococcus mitis.
2- streptococcus sanguinis.
3- streptococcus salivarius.
4- streptococcus mutans.
5- staphylococcus epidermidis.

Question 12

Which part of the respiratory tract is normally considered sterile?

Answer 12

Lower respiratory tract.

Question 13

List common resident microorganisms found in the nose and nasopharynx?

Answer 13

1- staphylococcus aureus.
2- staphylococcus epidermidis.
3- diphtheroids (corynebacterium spp.).
4- hemophilus parainfluenzae.
5- streptococcus spp.

Question 14

List common resident microorganisms found in the oropharynx?

Answer 14

1- staphylococcus aureus.
2- diphtheroids (corynebacterium spp.).
3- streptococcus pneumoniae.

Question 15

Why is the stomach normally sterile?

Answer 15

Due to acidic pH.

Question 16

List the exceptions to the normal sterile environment of the stomach?

Answer 16

Endospores, parasitic cysts, H.pylori.

Question 17

How do pathogens enter the GIT?

Answer 17

Enter in food particles.
Escape stomach and enter the intestine.
Colonize the small and large intestine.

Question 18

How do antibiotic affect the normal biota of the GIT?

Answer 18

Can significantly alter the usual flora.

Question 19

List common resident microorganisms found in the GIT?

Answer 19

1- bacteroids spp.
2- clostridium spp.
3- enterobacteriaceae.
4- eubacterium spp.
5- fusobacterium spp.

Question 20

List the sterile sites of the genitourinary tract?

Answer 20

1- kidney.
2- bladder.
3- fallopian tubes.

Question 21

List the nonsterile sites of the genitourinary tract?

Answer 21

1- distal urethra (particularly in women).
2- vagina.

Question 22

List common resident microorganisms found in the Genitourinary tract?

Answer 22

1- lactobacillus spp.
2- peptostreptococcus spp.

Question 23

List the role of microbial biota in the pathogenesis?

Answer 23

1- opportunistic infections.
2- trauma: introduce flora to sterile site.
3- immunosuppression.
4- in patients with serious infections associated with chronic illness like diabetes and severe hepatic disease (i.e, cirrhosis).

Question 24

List the role of microbial biora in the host defense against infectious disease?

Answer 24

1- normal microbial flora; prime the immune system, axenic animals: germ free, sterile environments impair immune development.
2- microenvironment: microbial flora block colonization of extraneous pathogens, antibiotics can alter the indigenous biota.

Question 25

Definition: organisms that cause disease in healthy immunocompetent hosts?

Answer 25

True pathogens.
Examples: Y.pestis and B.anthracis.

Question 26

Definition: infection that occurs as the result of medical treatment or procedures?

Answer 26

Iatrogenic infections.

Question 27

List opportunistic microorganisms that come because of foreign bodies (catheters, shunts, prosthetic heart valves)?

Answer 27

• Staphylococcus epidermidis.
• Viridans streptococci

Question 28

List opportunistic microorganisms that come because of alcoholism?

Answer 28

• Streptococcus pneumoniae.
• Klebisella pneumoniae.

Question 29

List opportunistic microorganisms that come because of burns?

Answer 29

• Pseudomonas aeruginosa.
• staphylococcus aureus.

Question 30

List opportunistic microorganisms that come because of hematoproliferative disorders?

Answer 30

• Cryptococcus neoformans.
• varicella-zoster virus.

Question 31

List opportunistic microorganisms that come because of cystic fibrosis?

Answer 31

• pseudomonas aeruginosa.

Question 32

List opportunistic microorganisms that come because of immunosuppression (drugs, congenital disease)?

Answer 32

• candida albicans.
• pneumocystis jirovecii.
• herpes simplex virus.

Question 33

Name a zoonoses microorganism and disease that is an endemic in saudi?

Answer 33

Disease: brucellosis.
Organism: brucella spp.

Question 34

How is virulence measured?

Answer 34

By numbers of organisms required to cause disease.

Question 35

Definition: relative ability of microorganism to cause disease?

Answer 35

Virulence.

Question 36

List 2 trait that determine pathogenicity and virulence?

Answer 36

1- capsules (S.pneumoniae, H.influnzae, and N.meningitidis).
2- toxins (diphtheria, cholera).

Question 37

Definition: the microbial surface structures that mediate attachment?

Answer 37

Adhesins.

Question 38

List 2 adhesive structures?

Answer 38

1- fimbriae (pili) - main adhesin in bacteria.
2- surface polysaccharides.

Question 39

List 3 mechanisms that prevent organisms from being killed intracellularly?

Answer 39

1- secretory antibody: IgA proteases, antigenic variation.
2- lactoferrin: binds free iron, meningococci can use lactoferrin for iron.
3- lysosomes: prevent fusion, escape phagosome.

Question 40

Definition: composed of the lipopolysaccharide (LPS) portion of the outer membrane of gram-negative bacteria?

Answer 40

Endotoxin.

Question 41

List the 3 regions of endotoxins?

Answer 41

1- O-specific oligosaccharide.
2- core polysaccharide.
3- inner lipid A (also called endotoxin).

Question 42

How does Lipid A (endotoxin) affect the host?

Answer 42

Stimulates the release of pro inflammatory cytokines that aid in mounting an innate immune response.

Question 43

These chemicals mediate (cytokines) to produce effects of endotoxins resulting in which dramatic changes?

Answer 43

BP, clotting, bloody temperature, circulating blood cells, metabolism, humoral and cellular immunity, and resistance to infection.

Question 44

What does endotoxin exposure cause?

Answer 44

1- stimulation of the fever center in the hypothalamus.
2- hypotension.
3- septic or endotoxic shock.
4- coagulation initiation.
5- severe neutropenia.
6- immune system disturbance.

Question 45

List the characteristics of bacterial exotoxins based on organism type, chemical nature, stability to heating (100 C), detoxification by formaldehyde, neutralization by homologous antibody, and biological activity)?

Answer 45

Organism type: gram positive and gram negative.
Chemical nature: simple protein.
Stability to heating: labile.
Detoxification by formaldehyde: detoxified.
Neutralization by homologous antibody: complete.
Biological activity: individual to toxin.

Question 46

List the characteristics of bacterial endotoxins based on organism type, chemical nature, stability to heating (100 C), detoxification by formaldehyde, neutralization by homologous antibody, and biological activity)?

Answer 46

Organism type: gram negative.
Chemical nature: protein-lipid - polysaccharide
Stability to heating: stable.
Detoxification by formaldehyde: not detoxified.
Neutralization by homologous antibody: partial.
Biological activity: same for all toxins.

Question 47

List antimicrobial substances found in the body?

Answer 47

1- fatty acids on skin.
2- hydrochloric acid (HCL) in the stomach.
3- lysozymes.
4- immune proteins; IgA, low molecular weight cationic proteins (beta-lysins), complement (synergies to increase effectiveness of killing), interferon inhibits proliferation of viruses.