Transcript MICROBIOLOGY Curtis V. Smith Asst. Prof. Biological

Microbiology 261 –Lecture Notes
Microbes and Hosts: Infection,
Disease and Defenses
Dr. Gary G. Andersen
We make contact!



Resident flora – (skin, upper respiratory
tract, gastro-intestinal tract, urethra,
genitalia, vagina, external ear canal,
external eye) (Note: All internal tissues and
organs are sterile)
Birth is a microbe event
See pg 388 for microbes established on
humans.
Flora Locations and Types





Transient – (variable) such as on skin surface
Resident – (stable populations)
Skin - deeper layers of skin (stable populations of
Staphlococcus, Corynebacterium, & Yeasts)
GI tract: Mouth – Streptococcus species
GI tract: Intestine – Anaerobes such as
Bacteroides, Bifidobacterium, Fusobacterium,
Clostridium and Coliforms
Flora Locations and Types (cont.)



Respiratory Tract – upper nasal passages and
throat (Staphylococcus aureus)
Genitourinary Tract – eurethral opening and
vagina (Lactobacillus, Steptococcus,
Corynebacterium, Escherichia, Mycobacterium)
Germ-free animals are healthier as long as they
remain in a sterile environment
Host Parasite Relationships
A.
Symbiosis – the relationship between
bacteria (microbiota) and us (the host!).
1. Parasitism – pathogenic, harmful to
the host.
2. Mutualism – both microbe and host
benefit. Bacteria in the colon release
Vitamin K as a waste product. Vitamin K
is used in clotting.
3. Commensalism – microbe benefits by
absorbing nutrients released from
sloughed dead cells.
Normal Microbiota
Mutualists and commensalists comprise the
normal microbiota of the host. Normal
microbiota can be permanent (resident), or
transient bacteria. Opportunistic bacteria are
normal microbiota that may cause disease
when the immune system is depressed from
cold or flu viruses. It has been estimated 1015
bacteria live in or on the human body. (500 –
1000 species) Yet, the human body itself
comprises only 1014 eukaryotic cells in the
adult!
The disruption of Normal Microbiota
1.
Vaginal Bacteria
pH 4.0
birth - 2-3 wks.
Lactobacilli
(residual estrogen)
pH 7.5
2-3 wks. – puberty
Various Microbes
(no estrogen)
ex. Staph & Strep.
pH 4.0
puberty – menopause
Lactobacilli
(estrogen levels high)
pH 5.0
Oral contraceptives, broad spectrum antibiotics, or
frequently douching may cause: Opportunistic
infections may arise causing vaginosis: ex. Candida
albicans (yeast), Gardenerella vaginalis (bacteria), or
Trichomonas vaginalis (protozoan)
pH 7.5 postmenopausal Various Microbes: Staph & Strep.
GA f07
Infectious Disease Classifications
A. Symptomology – changes in body function
resulting from infectious diseases.
1. asymptomatic – without symptoms. Detection
based on positive blood test indicating
presence of antibodies. Inapparent,
subclinical and carrier are synonyms.
Insidious infection if damaging host tissues
without symptoms, Ex. Pelvic Inflammatory
Disease. Etiology: Chlamydia, or Neisseria
gonorrhea.
2.
3.
Subjective symptoms – malaise, a
general feeling of discomfort.
Objective symptoms – observable and
measured conditions. Ex. Rash size and
color, body temperature, and extent of
lymphadenopathy (lymph node
swelling).
Infectious Disease Stages
1.
2.
3.
4.
p 402
Incubation Period – no symptoms
Prodromal period – subjective
symptoms
Period of Invasion – objective
symptoms
Convalescence – decrease to subjective
or no symptoms.
Modes of Transmission MOT
Ye’ ole 6 F’s: feces, flies, fingers, fomites,
food and fornication!
1. Contact Transmission
a. Direct contact – STD’s, or
vertical (prenatal and perinatal).
b. Indirect contact – fomites: ex.
money, catheter, syringe, eating
utensils.
c. Droplet contact – within 1 meter
zone!
2.
Vehicle Transmission
GA f 07
a. Water – raw sewage in water results
in fecal-oral cycle.
b. Food – poisoning via bacterial toxins
as with botulism (ex. Clostridium
botulinum), or gastroenteritis from
bacteria (ex. Salmonella typhi) or
viruses (ex Rotavirus) that invade the colon.
c. Airborne – greater than 1 meter in
extreme wind blown conditions such as in
military settings. 747 airlines
recirculate air.
Vectors
3.
Vector Transmission
a. Mechanical – the feet of flies
b. Biological – insect bites
ex. Anopheles mosquito transmits
malaria, etiology: Plasmodium vivax.
ex. Rat Flea transmits bubonic plague,
etiology: Pasteurella pestis
ex. Tick transmits Lymes disease,
etiology: Borrelia burgdorferi
Flies defecate, vomit, feed
Zoonoses (pl.)– diseases transmitted directly from
animals to humans, or indirectly from animals by insect
vectors. ex. Malaria and Yellow Fever have a monkey
reservoir. Wild and domestic animals are carriers for
many human infectious diseases. Zoonoses include diseases
transmitted by feathers, hides, or furs to humans.
ex. Tularemia – “rabbit fever” etiology:
Francisella tularensis (Gram – bacteria)
ex. Toxoplasmosis – etiology: Toxoplasma
gondii. A protozoan parasite found in cat
litter boxes. Beware if pregnant or with
reduced immunity.
ex. Rabies – etiology; Rhabdovirus. A virus
transmitted by skunks and raccoon.
Rabies (Dog and restrained man)
GA sp07
Epidemiology
1.
2.
3.
Definition – the study of the incidence,
transmission and frequency of a disease.
Centers for Disease Control and Prevention
(the CDC) in Atlanta, MMWR, the Morbidity
and Mortality Weekly Report. Provides
cumulative statistical public health
information. http://www.cdc.gov/mmwr/
The World Health Organization (W.H.O.) in
Geneva, Switzerland. Conducts international
epidemiological research.
4.
5.
6.
7.
8.
Communicable disease – direct contact
Non-communicable disease – vehicle,
vector or indirect contact transmission.
ex. Bacillus anthracis endospores in the
mail!
Endemic – a disease that is constantly
present in a local population. Ex.
malaria
Epidemic – many people contracting a
disease in a short period of time. Ex.
Lyme disease
Pandemic – global spread of pathogen.
NOSOCOMIAL INFECTIONS p433
Nosocomial def. – from the Greek word for “hospital”
A.
B.
The CDC claims that ~8% of all inpatients acquire new
infections while in the hospital. ~ 20,000 deaths/year.
Three reasons for nosocomial infections:
1. There is a concentration of virulent, antibiotic
resistant microbes in hospitals.
2. Patients are normally immunocompromised from
chemotherapy, radiation, malnutrition, and
psychological or physiological stress.
3. Chain of Transmission – from patients to doctors
to other patients. Lack of handwashing!
What Normal Microbiota
become Nosocomial Infections
1.
2.
E. coli, Enterococcus faecalis, and Staph.
saprophyticus cause roughly ~50% of all
nosocomial infections. Due to urinary
catheterizations that push fecal bacteria into the
bladder (bladder infection- cystitis) High
mortality rate.
E. coli causes roughly ~25% of all nosocomial
infections due to colon surgery. Clostridium
difficile from prolonged use of antibiotics which
destroys normal bacterial communities.
3.
4.
5.
Lower respiratory tract pneumonia causing
microbes. ~12% of all nosocomial infections.
Pneumocystis carinii is the most common
opportunist in AIDS patients.
Cutaneous (skin) infections, ~ 8% of all
nosocomial infxns. Staph. aureus outbreaks in
nurseries and bedsores in long term care
patients. Ex. Methicillin Resistant Staph aureus
(MRSA).
Bacteriemia – bacteria accidentally introduced
into blood stream by contaminated intravenous
fluids. Ex. portacaths (implanted caths) or
dialysis.
Portacaths
What makes microbes pathogenic
or virulent?
SEVEN MECHANISMS OF
PATHOGENESIS
1.
2.
3.
Maintain a reservoir – in humans (carriers),
animals (zooneses), water, soil, dust etc.
Adherance hooks, spikes, tacky chems
Anti-phagocytic properties: capsule, Wax D,
M-protein in Streptococcus pyogenes, and
antigenic drift in Influenza (virus), Neisseria
(bacteria), and Trypanosomes (protozoan).
Adhesion: How do pathogens stick?




Fimbriae (bacterial
projections)
Capsules (bacterial
coatings)
Spikes (viral
particles)
Hooks
(Treponema) or
flagella
(Salmonella)
Vibro cholerae attaching to intestinal cells
4. EXOENZYMES – secreted by
pathogens
a.
Hemolysin – lysis of erythrocytes (RBC)
b. Leukocidin – degrades lysosomes, the digestive
vacuole found in phagocytes. Staph. aureus.
c.
Coagulase – clots blood Staph aureus.
d. Streptokinase – dissolves clots ex. Strep. and
Staph.
e.
Hyaluronidase –hydrolyzes the “glue” that
holds cells together, I.e. the dermis to the
epidermis. Leaves tissues black. ex. Clostridium
perfringens causes gas gangrene.
f.
g.
Collagenase – degrades collagen, Strep.
pyogenes (necrotizing faciitis)
Urease – ex. Helicobacter pylori survives
at low stomach pH. Causes ulcers.
http://www.bact.wisc.edu/Bact330/lecturehelico2
h.
Neisseria gonorrhea degrades
imunoglobulin (IgA) found in mucous
rendering its antibody activity to be lost.
5. SIDEROPHORES
Most pathogens obtain iron from the host
by secreting these low molecular weight
proteins into the blood which strip iron
from transferrin, a glycoprotein in the
blood.
Exotoxins







Secreted to attack
specific targets
Toxic in small amounts
Polypeptide composition
Unstable at 60 C
Convert to toxoid
Stimulate antitoxins
No fever
Endotoxins








Found in cell wall of
gram – bacteria
Released on cell lysis
Toxic in high doses
Lipopolysaccharide
composition
Stable at 60 C
Do not convert to
toxoid
Do not stimulate
antitoxins
Fever
6. EXOTOXINS
a.
b.
c.
d.
e.
Toxic proteins secreted by bacteria that
disrupt cell membranes.
Toxemia – exotoxins in blood or lymph.
Toxoid – inactivated altered exotoxins
used for vaccination.
Exotoxins are toxic in small quantities.
Exotoxins are heat labile (sensitive) if
treated at 60 degrees Celsius for 30
minutes.

f. Three examples of powerful exotoxins:
1. Cytotoxins – kill host cells by disrupting
protein synthesis. Toxoid used in “D” part of
the DTP vaccine. ex.
Corynebacterium
diphtheriae
2. Neurotoxins – act on nerve cells
ex. Clostridium tetani – (tetanus) blocks Ach
inhibitors and leaves ACh on. Spastic paralysis.
ex. Clostridium botulinum – (botulism) binds
ACh receptors blocking them. Flaccid paralysis.
3. Enterotoxins – binds to villus cells causes
excess loss of water and electrolytes
(gastroenteritis). ex. Vibrio cholerae.
7.
a.
b.
c.
d.
e.
ENDOTOXIN
– also known as “Lipid A”
Found in lipopolysaccharide of Gram –
cell wall.
Heat resistant.
Toxic only in large quantities
No toxoid (vaccine) available
Limulus test – an industrial Lipid A
detection method used by manufacturers
of IV fluids. (Came from horsehoe crab)

f. PHYSIOLOGICAL
EFFECTS OF LIPID A
In Six Easy Steps! Causes Endotoxic
Shock, synonymous with Blood
Poisoning, and Sepsis Shock.
1. Originates with lysed Gram – bacteria in
blood (bacteremia). Lipid A fragments
of Gram - cell wall are scattered
throughout cardiovascular system, and
becomes lodged in the capillary network
of vital organs.
2.
3.
4.
Prostaglandins are released by endothelial cells in
contact with Gram – bacteria causing
vasodilation.
Macrophage (MP) phagocytize some Gram –
bacteria. MP release IL-1 signals the
hypothalamus to produce fever. Fever has 3
benefits: Inactivates bacterial enzymes, hides iron
from bacteria, and increases leukocytic
infiltration.
Neutrophils cannot squeeze through endothelial
cells to reach lipid A lodged in basement
membrane of capillaries. “Frustrated”
neutrophils release digestive enzymes on
endothelial cells.
5. On massive scale causes Disseminated
Intravascular Coagulation (D.I.C.).
6. Result: Endotoxic Shock. Impaired oxygen
exchange in lungs leads to coma, and death.
~ 175,000 deaths per year in the U.S.
7. Diseases that cause Endotoxic Shock:
a. Neisseria meningitidis meningitis
b. Salmonella typhi – typhoid fever
c. Nosocomial infections (cystitis)
Opportunistic Gram - (E. coli)
Application of Pathogenesis:
Bioterror

NOVA “Bioterrorism”
http://www.pbs.org/wgbh/nova/bioterror/bi
owarriors.html
Body Defenses Overview



1st line of defense (physical, chemical and
genetic barriers)
2nd line of defense (Inflammation,
Interferons, Phagocytosis) (linked to 3rd)
3rd line of defense (Immune response)
Body Defenses
Nonspecific Immunity (Innate) offers
general protection from all pathogens.
I. Skin - the largest organ of the body in
terms of surface area.
A. Epidermis - outer thin layer contains
stratified squamous epithelium. Forms a
barrier against most pathogens.
Keratinocytes secrete keratin, a type of
wax. Most microbiota is located here.
B
o
d
y
D
e
f
e
n
s
e
s
c
o
n
t
.
GA f 07
B. Dermis – skin’s inner thicker part
composed of connective tissue made of
collagen.
1. Dendritic cells are a type of phagocyte found in
the skin derived from monocytes. These cells
migrate to the lymph nodes after phagocytosis.
2. Mast cells release histamine during inflammation.
Not normally in circulation but in the skin.
3. Suderiferous glands produce sweat. Sweat
contains lysozyme and NaCl which inhibits most
bacteria except - Staphylococcus epidermidis
4. Sebacous glands produce sebum, an unsaturated
fatty acid, lowers skin pH to 4.0.
Dendritic Cell
Dendritic Cells
i
n
D
i
a
g
r
a
m
(
C
r
o
s
s
S
e
c
t
i
o
n
)

(Nerve ending)
Body
Defense
s cont.
C. Subcutaneous Tissue – mostly the
membranes that line the G.I.T., G.U.T., and
R.T!
1. Goblet cells secrete mucus. Prevent cells
from drying out and cracking. Keeps bacteria
flowing over the surface of cells lining tracts
of the body.
2. Ciliated columnar cells wave dirt, dust and
bacteria out of the body. In the R.T., cilia
wave particles up toward the epiglottis
where they are swallowed. The "muco-ciliary
escalator."
3. Hydrochloric Acid (HCl) pH 1.8 stomach
4. Salivary glands 1 liter of saliva per day.
Bathes teeth with lysozyme (destroys
peptidoglycan layer ).
5. Lacrimal glands produce tears, contain
lysozyme.
Mucous membranes
II. Phagocytic System - Phagocytosis (to eat)
P
h
a
g
o
c
y
t
i
c
S
y
s
t
e
m
A. Mechanism Fig. 16.3
1. Chemotaxis - chemical attraction of
phagocytes to a microbe.
2. Adherence - attachment
3. Ingestion - pseudopods extend
around microbe.
4. Digestion - the plasma membrane of
a phagocytic cell pinches off into
the cell and forms a vacuole
(phagosome). Lysosomes fuse with
phagosome. Contain nitric oxide and
lysozyme which kills microbes, and digestive
enzymes that degrade microbes.
P
h
a
g
o
c
y
t
o
s
i
s
d
i
a
g
r
a
m
Five
Leukoc
y tes
Five Types of Leukocytes (wbc’s)- made
in the bone marrow (Figure 16.1 p. 448). 3
Granulocytes- with granules in cytoplasm.
1. Neutrophils stain poorly and have 27 nuclei. 1st phagocytes to arrive at
site of inflammation. 60% of blood
leukoctyes.
2. Eosinophils stain red have 2 nuclei
and phagocytize large parasites
(protozoans, worms and fungi).2-4%.
3. Basophils stain blue and release
histamine during inflammation. Nonphagocytic. < 1%.
B.
Neutrophil
Multi-nucleate
Lightly staining
Phagocytic
Stain blue
Non-phagocytic
Inflammatory response
Release histamine
Multineucleic
Lightly staining
Phagocytic
Eosinophil
Two nuclei
Stain orange/red
Phagocytosis of large
antigens such as protozoans
and worms
sp08
Two nuclei
Stain orange/red
Phagocytosis of large
antigens
Basophil
Stain darkly (blue)
Non-phagocytic
Inflammatory response
Release histamine
Monocyte
Agranulocyte
Notched nucleus
Become macrophages when out of circulation
Lymphocyte
Become T or B cells
Specific Immunity Responders
Agranulocy tes (Monocy tes &
Ly mphocy tes)
Two Agranulocytes-no granules in
cytoplasm.
4. Monocytes --horseshoe shaped nucleus.
Largest leukocyte. Migrate out of the
circulatory system and wander into
any tissue of the body scavenging
for foreign substances. If out of the
circulation, they are called macrophage
(MP). Ingest 100 bacteria at once.
3-8% of all wbc’s in blood.
5. Lymphocytes - make up 20% of all
leukocytes. Function in specific
immunity. There are basically two
types: T cells and B cells.
C.
Platelets, or thrombocytes, are small
cells that form blood clots.
B cells and T cells


B-cells develop in
the bone marrow
T-cells migrate
from bone
marrow to the
thymus where
they complete
their
development.
Platelets
Inflamm
ation
III.Inflammation is a nonspecific host
defense mechanism designed to mobilize
components to the site of injury, destroy
microbes, and set repair processes into
motion.
A.
4 Cardinal Signs of Inflammation
1.
Rubor - redness or erythema
2.
Dolar - pain
3.
Calor - heat
4.
Halor - swelling, can be fluid
(edema) or cellular (tumor).
Five Patterns of
Inflammation
B. 5
1.
2.
3.
Patterns of Inflammation
Serous – water blister, mild burns
Fibrinous – scar tissue formation
Pseudomembrane – new membrane
formed over the old.
4. Suppurative – pus formation, dead
neutrophils and target bacteria
within an abscess.
5. Ulcer – crater from inflammed
tissue.
C. Inflammatory Response consists of
three phases;
Fluid, Cellular, and Healing
This yellow-green exudate on the surface of an inflamed,
hyperemic (erythematous) bowel mucosa consists of many
neutrophils along with fibrin and amorphous debris from
dying cells.
Here is a purulent
exudate in which the
exuded fluid also
contains a large
number of acute
inflammatory cells.
Thus, the yellowish
fluid in this opened
pericardial cavity is a
purulent exudate.
A purulent exudate is seen beneath the meninges in the brain of
this patient with acute meningitis from Streptococcus
pneumoniae infection. The exudate obscures the sulci.
GA
Fluid
Phase
1. Fluid Phase (Chemical Mediators)
a. Bradykinin produced in kidney, causes pain
and vasodilation. (found in bee venom)
b. Histamine-released by mast cells
causes vasodilation and smooth muscle
contraction. (problem- asthma)
c. Prostaglandin –lipid released by somatic
(body) and mast cells, causes vasodilation
d. Heparin - by mast cells, anticoagulant
e. Leukotrienes - by leukocytes,
squeezing
effect on capillaries +(bronchial constriction)
Fluid
Phase
(cont.)
f. Seratonin – released by platelets causes
vasodilation.
g. Histamine – released by
Basophils.(vasodilation)
h. Complement - consists of 20 serum
proteins that bind to antibody in an
ordered sequence, or cascade. Pg 462
C3a - interacts with mast cells causes
release of histamine
C3b - enhances phagocytosis by coating
(process
called opsonization)
C5a - chemotactic for neutrophils
i. LPf - leukocytosis promotion factor by
mast cells, chemotactic for
neutrophils.
C
o
m
p
l
i
m
e
n
t
P
a
t
h
w
a
y
With mast cells release
Histamine
Attracts
Neutrophils
Complement
End Results
Cytolysis
Clotting
h. Hemostasis - clotting begins within 15-20
seconds if there is a severe cut. and 1-2
minutes if minor. 12 clotting factors
found in serum. Activated when they
leave the circulatory system.
Ex. Prothrombin -----------> thrombin
(in blood)
(out of circulation)
thrombin (enzyme)
Ex. Fibrinogen ------------>
fibrin
(in blood)
(out of circ.)
Fibrin enmeshes platelets.
These two substances form the clot.
Simplified Steps in Clotting
Fibrinogen to
Fibrin
Changes from
“ball” to “fiber”
Cellular
Phase
2. Cellular Phase - occurs within 1 hour and
involves phagocytic cell infiltration.
Occurs within an abscess in supparative
pattern of inflammation.
a. low pH kills microbes
b. macrophages attack escaping microbes
c. body temperature increases due to
macrophage signaling the hypothalamus
with lymphokine (a chemical secreted
by white blood cells that regulates the
immune response) called IL-1
(interleukin I). Note: Specific
Immunity begins here!
3. Healing Phase
a. Fibroblast cells produce beta interferon
(a lymphokine secreted by cells of the
body that regulates the immune
response). This chemical signals the
immune system to stop.
b. Fibroblasts proliferate and produce
collagen fibers.
c. Macrophage also produce collagen.
d. Intact connective tissue reforms.
Cytokines
Cytokines are chemicals secreted by cells of the body
that regulate the immune response. “Chemical
messengers” Cytokines produced by leukocytes
are lymphokines.
Wound
Infectio
ns
I
n
t
e
r
f
e
r
o
n
IV.Interferon (abbrev. IFN)
Discovered in 1957.
A. Beta Interferon - produced by
fibroblasts. Activates T suppressor
(TS) cells to end the inflammatory
response.
B. Alpha Interferon – viruses trigger
neighboring cells to produce antiviral
proteins. Used to treat symptoms of
ovarian cancer, multiple sclerosis,
Kaposi's Sarcoma and HCV.
C. Gamma Interferon - produced by T
helper cells (TH1) in response to
viruses. Gamma-IFN activates
macrophages (MP) and Natural Killer