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INTRODUCTION TO INFECTIOUS DISEASES

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Title: INTRODUCTION TO INFECTIOUS DISEASES


1
INTRODUCTION TO INFECTIOUS DISEASES
  • PAUL A. GULIG, PH.D.
  • Feb. 19, 830, 930 AM
  • Office - R1-250, 392-0050
  • Lab R1-144, 392-0682
  • email gulig_at_ufl.edu

2
  • 1. Randall, a first year IDP student, went on a
    picnic at Crescent Beach. Before leaving for the
    beach he made chicken salad sandwiches, which sat
    in the hot car for five hours before being eaten.
    The next afternoon he had nausea, diarrhea, and
    mild fever, which persisted for three days, just
    long enough to ruin the condo rental! Symptoms
    resolved by the time he returned to school.

Diagnosis Treatment Keys
3
  • 1. Randall, a first year IDP student, went on a
    picnic at Crescent Beach. Before leaving for the
    beach he made chicken salad sandwiches, which sat
    in the hot car for five hours before being eaten.
    The next afternoon he had nausea, diarrhea, and
    mild fever, which persisted for three days, just
    long enough to ruin the condo rental! Symptoms
    resolved by the time he returned to school.

Diagnosis Salmonella gastroenteritis
Treatment - Symptomatic Keys Poor food prep
aration, bacterial invasion, intercellular
communication
4
2. Marsha, another IDP student, went on a picnic
at Manatee Springs. She ate some potato salad
that had sat in on the picnic table while she was
snorkeling. Five hours later, she had severe,
profuse vomiting, followed by some diarrhea. It
resolved in a day.
Diagnosis Treatment Keys
5
2. Marsha, another IDP student, went on a picnic
at Manatee Springs. She ate some potato salad
that had sat in on the picnic table while she was
snorkeling. Five hours later, she had severe,
profuse vomiting, followed by some diarrhea. It
resolved in a day.
Diagnosis Staphylococcal food poisoning
(intoxication) Treatment - Symptomatic K
eys Poor food preparation, toxin-mediated damage
6
3. Ann, a single 35 year old woman from Miami
met a guy at a bar in South Beach. After having
a few drinks, they engaged in wild sex. She
experienced mild, flu-like symptoms a couple of
weeks afterward. One year later on giving blood,
she was informed she was HIV-positive. Despite
treatment with newest combination HAART therapy,
she developed protracted, watery diarrhea that
could not be treated. The diagnosis was made by
observing oocysts in her stool. She ultimately
succumbed to her intestinal ailments. None of
here friends had ever experienced, nor ever
would, her intestinal disease, although they
encountered the agent frequently.
Diagnosis Treatment Keys
7
3. Ann, a single 35 year old woman from Miami
met a guy at a bar in South Beach. After having
a few drinks, they engaged in wild sex. One year
later on giving blood, she was informed she was
HIV-positive. Despite treatment with newest
combination HAART therapy, she developed
protracted, watery diarrhea that could not be
treated. The diagnosis was made by observing
oocysts in her stool. She ultimately succumbed to
her intestinal ailments. None of here friends
had ever experienced, nor ever would, her
intestinal disease, although they encountered the
agent frequently.
Diagnosis AIDS Cryptosporidium parvum
diarrhea Treatment HAART, no cure for Crypt
o Keys Viral mediated immunodeficiency, opp
ortunistic infection
8
4. Alice another graduate student from the IDP
traveled up North to visit her family in
Rochester, NY for spring break. It was still
very cold. The first day home, she went to a
movie. The person sitting next to her had a
cold and was sneezing, coughing, and blowing
her nose. Two days later, Alice had high fever,
sore throat, respiratory congestion, aches,
pains, and chills. It lasted for the rest of
break. When Alice returned to class, with some
residual sneezing and coughing, she gave the
disease to all of her friends in class.
Diagnosis Treatment Keys
9
4. Alice another graduate student from the IDP
traveled up North to visit her family in
Rochester, NY for spring break. It was still
very cold. The first day home, she went to a
movie. The person sitting next to her had a
cold and was sneezing, coughing, and blowing
her nose. Two days later, Alice had high fever,
sore throat, respiratory congestion, aches,
pains, and chills. It lasted for the rest of
break. When Alice returned to class, with some
residual sneezing and coughing, she gave the
disease to all of her friends in class.
Diagnosis - Influenza Treatment Amantidi
ne (early), Symptomatic Keys Viral respirat
ory infection, Host-host spreading
10
5. Brad, a 35 year old investment banker went
hiking in the Rocky Mountains of Colorado.
During his hiking trip he experienced severe
watery diarrhea with gas and pain. He just drank
extra fluid to make up for the fluid loss from
diarrhea. The diarrhea did not resolve for more
than two weeks after returning to New York City.
Diagnosis Treatment Keys
11
5. Brad, a 35 year old investment banker went
hiking in the Rocky Mountains of Colorado.
During his hiking trip he experienced severe
watery diarrhea with gas and pain. He just drank
extra fluid to make up for the fluid loss from
diarrhea. The diarrhea did not resolve for more
than two weeks after returning to New York City.
Diagnosis Giardia lamblia diarrhea
Treatment Anti-protozoals, symptomatic
Keys Protozoal, zoonotic infection
12
6. Mary, an undergraduate student at U.F., had
a bad cold. She went to the student clinic
demanding antibiotics. After some resistance,
they gave in to get rid of her. Three days later
she experienced very severe irritation of the
genital tract with redness, white plaque-like
material, itching, and inflammation.
Diagnosis Treatment Keys
13
6. Mary, an undergraduate student at U.F., had
a bad cold. She went to the student clinic
demanding antibiotics. After some resistance,
they gave in to get rid of her. Three days later
she experienced very severe irritation of the
genital tract with redness, white plaque-like
material, itching, and inflammation.
Diagnosis Candida albicans (yeast) infection
Treatment Anti-fungals Keys Post antibiot
ic infection, normal flora, host
response/inflammation
14
INTRODUCTION TO INFECTIOUS DISEASES
I. Wide variety of diseases with infectious
causes A. Severity self-limiting vs. lethal
B. Time course acute vs. chronic vs.
latent C. Where any organ system D. From t
he environment or people or animals
E. Highly contagious vs. non-transmissible
F. Relationship with the infectious agent
infection vs. non-infection (toxin only)
15
II. Wide variety of microorganisms that can cause
infectious disease in humans A. viruses - para
sitic nucleic acid 1. RNA vs. DNA genomes 2
. enveloped vs. non-enveloped
16
II. Wide variety of microorganisms that can cause
infectious disease in humans B. bacteria - pro
karyotic 1. cell wall gram-positive vs. gram-
negative vs. acid-fast 2. physiology aerobe
s vs. anaerobes
17
II. Wide variety of microorganisms that can cause
infectious disease in humans C. fungi - eukary
otic
- yeasts vs. molds
18
II. Wide variety of microorganisms that can cause
infectious disease in humans D. protozoans- eu
karyotic - unicellular organisms with complex l
ife cycles
19
II. Wide variety of microorganisms that can cause
infectious disease in humans E. worms - animal
s
- large organisms with complex life cycles
20
III. Microbial Pathogenesis Infectious disease
usually constitutes a cycle of biological
interactions. Intervention preventing ? phy
sician. Understanding pathogenesis ? interven
tion prevention other than antibiotics or
vaccines.
21
A. Definitions and concepts 1. Disease - dama
ge caused by presence of microorganisms or their
products 2. Pathogen - any organism that has
the potential to cause disease
a. overt pathogens - a high probability of ca
using disease in an otherwise healthy host
b. opportunistic pathogens have a low probabi
lity and usually require a debilitated or
compromised host
22
A. Definitions and concepts 3. Normal flora
- organisms that are found in a significant
portion of the healthy population may still have
the potential to cause disease (i.e., some
pathogens are normal flora) 4. Infection - pr
esence of bacteria in or on the body (note that
some use this term synonymously with disease)
5. Colonization - presence of microorganisms a
t a site (some infer no damage)
23
B. Functions/stages of pathogens/disease
1. Encounter a. Exogenous vs. endogenous
infection and normal flora i. Exogenous -
disease initiated shortly after encounter, no
stable interaction ii. Endogenous - diseas
e initiated after long-term stable relationship
24
B. Functions/stages of pathogens/disease
b. sources food, water, air, body fluids, in
sects, animals, fomites (things)
c. Is there a reservoir in other animals or i
n the environment? d. Can we eliminate the s
ource or reservoir?
25
2. Entry - where in/on the body do we initially
contact the microbes a. surface of skin
b. mucosal membrane open to outside
i. ingestion ii. inhalation iii. sex
c. direct inoculation (trauma, bite, inject
ion, surgery)
26
2. Entry - where in/on the body do we initially
contact the microbes d. virulence function
adherence i. to infect a mucosal surface o
r tract bathed with moving fluid, microbes must
stick or be washed away ii. specific ligand
-receptor interactions - not glue
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3. Spread - movement from surface through
tissues and body a. not all microbes spread
to cause disease b. microbes cannot penetrat
e intact skin, require macro or microlesions
c. mucosal surface is usually first barrier

29
3. Spread - virulence functions
i. cellular invasion - invading into host
cells to become intracellular professional p
hagocytes (macrophages and PMN) by phagocytosis
non-professional phagocytes (epithelial cells
, endothelial cells, hepatocytes, etc.) by
microbial mediated endocytosis
some microbes escape the phagosome into the c
ytoplasm
30
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31
Spread ii. tissue invasion - through tissu
es, either through cells or between cells
- degrade extracellular matrix
- disrupt tight junctions e. use of host
cells as vehicles to move through blood or lymph
(intracellular pathogens)
32
4. Multiplication a. inoculum is not sufficie
nt, need increase b. nutritional environments
in the body i. intestinal lumen, blood, urine
ii. intracellular bacteria- cytoplasm vs. p
hagolysosome c. incubation period how lon
g it takes the inoculum to result in clinical
damage
33
5. Evasion of host defenses (later lecture)
consider where the microbes are and which de
fenses they will encounter a. Complement -bey
ond mucosal surface b. Phagocytes - beyond muco
sal surface EXTRACELLULAR vs. INTRACELLULAR c.
Antibodies d. Cell-mediated immunity e. Lat
ency i. dormant in host ii. many viruses (e
.g., Herpes)
34
6. Damage a. cytotoxicity (kill host cells)
i. from outside - toxins ii. from inside
- intracellular growth b. pharmacology/physio
logy (alter host cell function) - toxins
35
6. Damage c. host immune/inflammatory respon
se (host causes damage to itself)
i. nonspecific inflammation, abscess, pr
ostaglandins, cytokines ii. specific immune
response antibodies, cell-mediated
36
d. TOXINS i. Endotoxin vs. Exotoxin
37
d. TOXINS ii. Endotoxin (LPS) from gram-negati
ve bacteria only - damage - macrophages produ
cing cytokines (TNF-a, IL-1, IL-6)
38
d. TOXINS iii. Exotoxins (proteins) se
veral have A-B motif Aactive portion Bbindin
g portion
39
iii. Exotoxins (proteins) lytic (pores or li
pase activity) cytotoxic (kill host
cells by altering functions, e.g., protein
synthesis)
40
iii. Exotoxins (proteins) pharmacological (a
lter host cell function, e.g., cAMP levels)
extracellular enzymes (degrade extracellular mat
rix, e.g., protease, DNase, hyaluronidase)
41
iii. Exotoxins (proteins) superantigens (sti
mulate host immune response in antigen-independent
manner resulting in cytokine cascade - similar
to endotoxin)
42
7. Spread to new host a. completes the cycle
to lead to new encounter virulence step 1
b. not all pathogens spread to new human
host (e.g., Legionella pneumophila)
c. not all pathogens are contagious - hum
ans may be dead end hosts
43
7. Spread to new host d. most bacterial pat
hogens are contagious - some examples of
how i. fecal-oral ii. sexually transmit
ted iii. droplet spread (respiration) iv.
skin-skin v. fomites vi. vertical - in
utero, at birth
44
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