GI Micro

Question 1

GI System Defenses

Answer 1

General –> epithelium, mucous, peristalsis
Mouth –> saliva and normal flora
Stomach –> acidity and normal flora??
Intestines –> peyer’s patches and normal flora

Question 2

Normal flora in mouth???

Answer 2

Mouth is very clean until teeth come in –> then lots of normal flora

Question 3

Upper GI normal flora

Answer 3

sparse in stomach and small intestine

Question 4

Lower GI normal flora

Answer 4

MICROBIOME

• anaerobes
• gram (-) rods
• Enterococcus
• Spirochetes

Question 5

Caries

Answer 5

Dental infection –> tooth decay
Pain, tooth decay, and spread of infection
Risks => high sugar diet, poor oral hygiene, decreased saliva, smoking, periodontal disease
Common worldwide
Occurs by microbial overgrowth –> decrease in pH –> demineralization of teeth

Question 6

Treatment of dental caries

Answer 6

drill out tooth that is infected and replace

Question 7

Periodontal Disease

Answer 7

Gingivitis –> infectious disease destroying supporting structures of teeth
Mild –> irritation, redness, swelling

Question 8

Periodontitis

Answer 8

Infection of underlying tissue and bone
- associated with MI, stroke, lung disease, premature birth
Occurs because of host immune response to infection

Question 9

What is essential for dental disease?

Answer 9

Plaque formation –> BIOFILMS

Question 10

Biofilm

Answer 10

2 or more species of bacterial microcolonies enclosed in a glycocalyx (polysaccharides, DNA, protein)
Formation
1. weak adherence
2. strong adherence
3. multiplication
4. polysaccharide formation
5. changing of composition over time

Question 11

Advantages of living in biofilm

Answer 11

adherence
protection from immune system
protection against antibiotics
symbiotic relationships 
better pH

Question 12

Normal microbes of mouth

Answer 12

ANAEROBIC ORGANISMS
‘mitis’ group of strep species –> protect against dental caries
- also gram (+) lactobacilli and spirochetes

Question 13

Microbes that cause caries

Answer 13

Usually located on tooth/plaque surface –> usually gram (+)

Question 14

Microbes that cause periodontal disease

Answer 14

Usually located in subginival space –> usually gram (-)

Question 15

Streptococcus mutans

Answer 15

gram (+) –> cocci –> catalase (-) –> anaerobic –> alpha hemolytic –> optochin resistant
VF
1. adhesion-like surface proteins (AG I/II) –> bind to pellicle
2. extracellular glucosyltransferases (Gtfs) –> become part of pellicle and pump out glucans –> additional binding sites

Question 16

Keystone pathogens of periodontal disease

Answer 16

“red group” pathogens –> hard to detect
BIG 3
Treponema denticola –> spirochete
Tanerella forsythia –> anaerobic, gram (-)
Porphyromanos gingivalis –> best studied

Question 17

Aggergatibacter actinomycetemcomitans

Answer 17

extreme aggressive gram (-) rod of periodontal disease

Question 18

Porphyromonas gingivalis

Answer 18

Gram (-) –> bacillus –> anaerobic –> asaccharolytic –> black-pigmented colonies on blood agar –> bacitracin resistant

Question 19

Prevention of periodontal disease

Answer 19

less sugar in diet
brush and floss regularly
fluoride
increased saliva –> gum

Question 20

Gingivitis Treatment

Answer 20

Same as prevention –> good cleaning and oral care

Question 21

Periodontitis Treatment

Answer 21

clean all surfaces and pockets

• topical empiric antibiotics = mild cases
• surgery = severe cases

Question 22

Ludwig’s Angina

Answer 22

skin infection on floor of mouth from untreated dental infections –> swelling of infected area may block airway
REDNESS OF NECK

Question 23

Candidia albicans

Answer 23

yeast-like fungus –> pleomorphic
oral thrush –> creamy white lesion on tongue or cheeks
esophageal form = DANGEROUS
diagnosis made on clinical symptoms
Tx with anti-fungal –> azole/amphotericin

Question 24

Helicobacter pylori

Answer 24

Gram (-) –> flagellated helix-shaped rod (spirilli) –> microaerophilic –> catalase and oxidase (+) –> urease +
- 50% of U.S. infected –> only 10% have ulcer (some strains more virulent)

Question 25

H. pylori infections

Answer 25

symptoms and disease result from host immune response

Question 26

Gastritis

Answer 26

caused by H. pylori –> inflammation of gastric mucosa
Symptoms
- gnawing or burning ache in upper abdomen
- N/V
- feeling of fullness in abdomen

Question 27

Gastric ulcer

Answer 27

caused by H. pylori --> open sores that develop on inside of stomach lining
Symptoms
- felt anywhere from navel to breastbone
- worse when stomach empty
- flares at night
- relieved by eating foods
- disappear and reappear within days

Question 28

Virulence Factors of H. pylori

Answer 28

• Inhibits phagocytic uptake, inhibits immune response, evades killing by ROS and NO, evades recognition of receptors
• Urease –> raises pH (ammonia) –> needs to break through low pH layer
• Flagella –> move through pH layer
• Chemotaxis –> based on pH gradient
• Adherence

Question 29

Toxins produced

Answer 29

VacA –> pore forming cytotoxin that allows leakage to Ca from cell
CagA –> T4SS, travels through needle into cytosol and affects proliferation, adhesion –> HIGHLY proinflammatory

Question 30

How to cause ulcers

Answer 30

1. Attract inflammatory cells
2. Inflammatory cells cannot kill easily
3. Host damages itself by continual ineffective immune response

Question 31

Diagnosis of H. pylori

Answer 31

Endoscopy –> gold standard
Breath test –> detects radioactive CO2 as a result of urease (+)
Stool test –> direct antigen test –> good for diagnosis and confirming cure
Blood test –> detects H. pylori antibodies –> not useful for confirming cure

Question 32

Treatment of H. pylori

Answer 32

“Triple Therapy”
Antibiotics –> clarithromycin and amoxicillin
Proton Pump Inhibitor

Question 33

Gastric MALT

Answer 33

Indigestion, heart burn
Long term inflammation is culprit
Tumor of B cells
Antibiotics still part of strategy

Question 34

Gastric Carcinoma

Answer 34

Indigestion, heart burn
Long term inflammation is culprit
Cancer of stomach lining
H. pylori is risk factor