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1. Microbe-Human Interactions:
Infection & Disease

2. I. Introduction
A. Recall _______ Postulates (experimental steps to establish the
microbe that causes a disease)
1. isolate a pathogen from a diseased host & grow pathogen in pure
culture
2. inoculate a healthy organism with the cultured pathogen
3. organism must get the same disease
4. isolate the same pathogen from the new host
B. Exceptions to Koch’s postulates
1. Microbes that can’t be grownon artificial media
examples:
2. More than one microbe produces the same disease
examples:
3. One microbe that causes multiple diseases
examples:
4. Strictly human diseases with no animal model
examples:
Koch’s
Viruses
pneumoniameningitis
Rickettsia Treponema
Streptococcus pyogenes
Rubella (German measles) smallpox
Strep throat
Scarlet fever

3. II. ____________ (microbes that normally live in/on the body w/o harm)
A. _______ vs _________ flora
(always there)(only present for a short time oron and off)
B. Establishment of Normal Flora = __________
1. Newborns are free of flora, but established as infant is exposed to
organisms from _______, _____, ______ etc.
2. Colonization is a selective processdue to physiological conditions in
the body such as _____, ___________, ____, ________, etc.
3. Takes about ____________ to fully establish normal flora
C. __________ (different organisms living together)
1. __________ (bothpartners benefit)
E. coli: produces vitamins K & some B, and ___________
(chemicals that ward off harmful species)
2. ___________ (onepartner benefits, other is neutral)
skin organisms live off of secretions/sloughed cells
3. _________ (onepartner benefits while the other is harmed) many
bacteria, fungi, protozoans, worms and even viruses
Normal Flora
ResidentTransient
Colonization
vaginaairfood
pH temperatureO
2nutrients
12-18 months
Symbioses
Mutualism
bacteriocins
Commensalism
Parasitism
parasite host

4. D. ____________ organisms (organisms that are usually nonpathogenic,
but that can become pathogenic under certain circumstances)
1. when host health is compromised
2. when there is a reduction of normal flora
3. if an organism gets in a different_______ (part of the body)
III. Mechanisms of ____________ (disease development)
A. Production of disease is actually a process of steps
1. ____________ to a susceptible host
2. ___________ to appropriate target tissue(s)
3. ________
4. __________
5. ________ to host while evading defenses
6. _____ from body
7. _________ outside long enough to be transmitted to another host
habitat
Pathogenesis
Transmission
Adherence
Invasion
Colonization
Damage
Exit
Survival
E. colifrom gut to urinary tract
Klebsiella pneumoniaefrom gut to respiratory
Opportunistic

5. B. Transmissionmust be to the correct “portal of entry”
1. typically to exposed surfaces such as ______ or _______
membranes (which is notan easy thing to do!)
2. entry aided by _____, ____, ________, _________etc.
a. Gastrointestinal tract(via ______, _____)
bacteria, especially Gram-_______ bacilli
viruses such as polio and Hepatitis A
protozoans such as Entamoebaand Giardia
b. Respiratory tract(via ____)
bacteria that cause strep throat, diphtheria, pertussis
viruses such as influenza, measles, mumps, rubella, chickenpox
and the common cold
fungi such as Histoplasmaand Pneumocystis
c. Urogenital tract(most are _____) (ormisplaced opportunists)
bacteria such as Neisseria, Treponema, and Chlamydia
viruses such as papilloma and herpes
protozoans such as Trichomonas
fungi such as Candida
skin mucous
bitescutsabrasionspunctures
foodwater
enteric
air
STDs

6. 3. ________ ____ = minimum number of microbes necessary to insure
infection (ex: only 10-100 Shigellabut 1,000,000 Salmonella)
C. Adherence(attachment)
_________ (projections of microbe that match host receptors)
1. pili tips, surface proteins, etc. (can change b/c of mutations so
previous Ab don’t recognize them!)
2. same organism can have different ligands to adhere to different
parts of the body (ex: Haemophilus influenzae)
3. some ligand genes on plasmidscan spread like antibiotic resistance!
4. why people don’t get a lot of other animal diseases and vice versa
D. Invasion(in order to establish infection)
1. high concentrations, more likely to invade successfully
2. ___________ = presenceof bacteria in the blood
________ = presenceof viruses in the blood
E. Colonization(when conditions are such that invading microbes are
successful enough to _________)
__________ = blood infection where bacteria are reproducing
Infectious dose
Ligands
Pink eye
Middle ear
Viremia
Bacteremia
reproduce
Septicemia

7. F. Evadehost defenses (mainly by avoiding ____________)
1. ________ (Streptococcus, Salmonella, Neisseria)
2. __________ are substances that are toxic to WBCs
3. _________ breaks down H
2O
2produced by phagocytes, preventing
digestion of the engulfed microbe
& Cause Damage/Disease
4. _______ (poisonous substances) (________ when in the blood)
a. _____: toxic soluble proteins secreted (botulism, tetanus)
___________ cause lysis of RBC’s
b. _____: cell wall components released when cell dies, toxic to
host (lipopolysaccharides in Gram-negativecell walls)
5. ____________ (act on host cells/tissues)
a. __________ activates prothrombin to coagulate fibrinogen in
plasma, forming a fibrin clotthat “hides” the microbe from
phagocytosis
b. ___________ breaks down blood clotsin order to spread
c. _____________ “spreading factor” breaks down hyaluronic acid
(loose connective tissue), allowing organism to invade tissues
phagocytosis
Capsules
Toxins Toxemia
Exo-
Endo-
*Can lead toSeptic shock
Exoenzymes
Hemolysins
Leukocidins
Coagulase
Fibrinase
Catalase
Hyaluronidase

8. Late stage necrosis of epidermis, subcutaneous layers, fascia, and
musculature of upper lateral leg. Necrosed peripheral nervous tissue
results in no perception of pain at wound site!
The effects of Hyaluronidasecan be drastic!

14. G. Development of Disease
1. __________ period (between infection and 1st signs/symptoms)
Depends on dose of microbes, which microbes, virulence, host health
a. typhoid fever 10-14 days
b. AIDS 10 years! (allows more spreading!)
(2). _________ period of 1-2 days follows incubation in some
diseases (= early, mild signs/symptoms such as _______, _______,
____________, etc. )
3. ______ period when the disease is acute and ______most likely
a. _______/______
b. numbers of ___________ (>10,000/ml)
c. swollen _____ _____
d. ______________
e. ____________
f. severe ____
4. Recovery
________ period (1-few days) when signs/symptoms are subsiding
BUTmost susceptible to secondary, ___________ infections
____________ period needed to regain strength
Incubation
Prodromal
Illness Death
ChillsFever
Leukocytes
lymph nodes
Nausea/diarrhea
Rashes/lesions
pain
Decline
Opportunistic
Convalescent
malaisefatigue
muscle aches

15. H. Disease Terminology
1. _____ infection (limited to point of entry)
Vs
_____ infection (spreads to a new location)
Vs
________ (infection that spreads to several sites and the blood)
2. ______ diseases develop fastbut for a shortduration
Vs
_______ diseases develop slowbut for a longduration
Vs
______ diseases may be inactivefor long periods of time
3. ________ (identification) of a disease is dependent upon:
_________ of a disease are subjectivechanges in body function
Vs
_____ of a disease are objective(measurable) changes
Local boil
Focal
Tooth abscess
tonsillitisappendicitis
wart
rabiesHepatitisA
Systemic
measles syphilischickenpox
Acute
Chronic
Latent
influenza
cold
TBleprosy
Cold sores
Diagnosis
Symptoms
Signs
painaches malaise
feverrashlesionsedema
sore throat
inflammation
Genital herpes

16. A _________ is a groupof symptoms/signscharacteristic of a
certain disease.
A _________ infection is asymptomatic,
but patient is still infectious
(more common in children)
Syndrome
Subclinical
I. Exitby means of
1. ______/_______
2. ________ 4. ____________
3. ____ /_______ 5. _____
J. Survivaloutside long enough to gain entry into a new host
1. Some can also live in the environment
2. Some are hardy and can survive for as long as several weeks
before a new host comes along
3. Some hang out in animal__________
4. Some require direct contact b/c they are fragile
K. Pathogenesisdepends on many factors
1. Genetics, both species and individual
2. state of host health
3. age (_______& ________have less capable immune systems)
4. ________ (causes corticosteroids that are immunosuppressive)
CoughSneeze
Diarrhea
PusBlood
Insect bites
Sex!
Clostridium tetani
Mycobacterium tuberculosis
reservoirsRabies, RMSF
Treponema
pallidum
Infants Elderly
Stress
Rubella syndrome

17. Epidemiology: The study of Disease in
Populations

18. IV. ___________ = study of frequency and distributionof disease in
order to set guidelines for disease prevention and control.
= like detective work to determine the cause, reservoirs, transmission,
portals of entry/exit, etc.
A. ____________ is essential to make predictions
1. National ________________________ & Prevention (CDC)
located in Atlanta, Georgia
2. _______________________________ (MMWR) tracks over
50 diseases carefully b/c hospitals, Drs., coroners, etc. REPORT
them: AIDS, STDs (such as gonorrhea, syphilis, Herpes), measles,
tetanus, TB, hepatitis, rabies, chicken pox, malaria, etc.
Epidemiology
Case reporting
Centers for Disease Control
Morbidity & Mortality Weekly Report
www.cdc.gov/mmwr/

19. 3. _______________________ (WHO) plans which diseases will
be targeted for eradication (such as smallpox, accomplished in 1979,
and polio, targeted for 2009).
B. Epidemiologic Statistics: Frequency of Cases
1. __________ = total numberof existing cases with respect to the
entire population (usually expressed as a __________);
a “snapshot” to help assess the overall impactof a disease
example: 100 people havea disease…………..
a. out of 500,000 people (0.02%) not a big deal, but
b. out of 500 people (20%) isa big deal
2. _________ # of ____ cases in a specific time period compared
with the general healthy population(usually expressed as # cases
per 100,000 people)
a. indicates both the _____ and ____ of infection
b. also called the__________ rate or ________ rate
A class of 50 students w/o influenza(P& Iboth 0 because 0/50 have
influenza) becomes exposed to influenza
1
st
week, 5 students become ill. P= ____ and I= __ in 10
2
nd
week 5 morestudents become illP= ____ and I= __ in 10
2
nd
week 5 morestudents become illP= ____ and I= __ in 10
w/1
st
5 students recovered
World Health Organization
Prevalence
Incidence
rate risk
Morbidity Disease
percentage
new
10% 1
20% 1
10% 1

21. Incidence of pneumococcal disease (per 100,000 people)

22. 3. _________ rate = percentage of people who diefrom a disease
4. Terms that describe disease frequency
a. _________ = a disease that is always presentin a population
(steady frequency)
b. ________ = a disease that only pops up occasionallyat irregular
intervals in random locales
c. _________ = a lot of people get a disease in a short time
(increasing frequency)
d. _________ = a worldwide epidemic
C. Investigative Strategies of the Epidemiologist
1. Determining ________ (= continual ______ of infectious organisms)
a. ________ are asymptomatic people that can spread disease
(1). _________ (50% of infected females are asymptomatic!)
(2). ________ Mary
*precautions can be taken:
*if humans are the onlyreservoir, it should be easier to control
Mortality
common cold
Endemic
Sporadic
Typhoid feverdiphtheria
Epidemic
ChlamydiaGonorrhea
Pandemic influenzaAIDS
sourceReservoirs
Carriers
Typhoid
Gonorrhea

24. 3. _________ rate = percentage of people who diefrom a disease
4. Terms that describe disease frequency
a. _________ = a disease that is always presentin a population
(steady frequency)
b. ________ = a disease that only pops up occasionallyat irregular
intervals in random locales
c. _________ = a lot of people get a disease in a short time
(increasing frequency)
d. _________ = a worldwide epidemic
C. Investigative Strategies of the Epidemiologist
1. Determining ________ (= continual ______ of infectious organisms)
a. ________ are asymptomatic people that can spread disease
(1). _________ (50% of infected females are asymptomatic!)
(2). ________ Mary
*precautions can be taken:
*if humans are the onlyreservoir, it should be easier to control
Mortality
common cold
Endemic
Sporadic
Typhoid feverdiphtheria
Epidemic
Chlamydia Gonorrhea
Pandemic influenzaAIDS
sourceReservoirs
Carriers
Typhoid
Don’t kissDon’t drink afterDon’t go out
Gonorrhea
Don’t have sex!

25. b. Nonhuman animals
(1) ________ vector (part of the pathogen’s life cycle)
(2) _________ vector (just carriers)
(3) _________ = an animal disease we can get
biological mosquitoes
mechanical
houseflies
cockroaches
Zoonosis
rabiesanthraxplagueRMSF
A fly walked on
the agar surface!

26. c. ____________ (soil, water, food)
2. Terms for transmission of infectious agents
a. ___________ diseases are spread from one person to another
b.Communicable diseases arecalled _________ if easilyspread
c. ______________ diseases (you cannotget them from another
person)
Environmental
tetanuscholeraSalmonella
Communicable
Herpes measlesCommon cold
Contagious
Chickenpox
Noncommunicable
tetanus botulism

27. 3. Patterns of communicable disease transmission
a. _______(Physical, person-to-person) “A portal of exit meets a
portal of entry!”
1 meter (close proximity) common in crowds, elevators
(1) _______ spread (mother to fetus/infant)
(2) _________ spread (anybody else to anybody else)
b. ________
(1) _______ (inanimateobjects)
(2) ______/______ (especially GI parasites) (This transmission
can be from the ________ or from __________; fecal-oral)
(3) _______ nuclei (small, dried up on dust, carried by aircurrents)
* good ventilation helpful (dilutes)
* air filters help trap
* pressurized air (out of operating rooms)
* damp mops better than brooms
Direct
touchkisssexRespiratory droplets/sneeze,
cough
Horizontal
Vertical
Indirect
Fomites
eating utensils
used kleenextoys needles
Toilet seatsDoor knobs
foodwater
Source Preparation
Salmonellaeggs/chicken Typhoid Mary
Droplet
Rubella, STDs

28. D. Areas of Epidemiology
1. _________ epidemiology occurs after disease outbreak and
describes the characteristicsof ill people
a. ____
b. _____
c. ____
d. _________
e. ________
f. ___________ (to help figure out reservoirs)
g. ______
* Common Source Epidemic
*Propagated Epidemic
Descriptive
age
sex
race
occupation
lifestyleSmoker?Druguse?Sexual activity?
Home location
Timing
time
#
c
a
s
e
s
time
#
c
a
s
e
s
2. _________ epidemiology then determineswhich risk factors
[identified by descriptive studies] are actually relevant by
_________ those withthe disease to those withoutthe disease
Analytical
comparing