Transcript Welcome to Ms. Looney`s Biology Class

Chapter 4: Infection
Ms. Harris
Pathophysiology
Fall 2009
• What is an infection?
– Colonization of a host organism by a foreign
species.
– The infecting organism is called a pathogen.
• Can be infected by a number of
microscopic organisms including bacteria,
protozoa, fungi, and viruses (although
viruses are NOT considered living).
Germ Theory
• Provided a link between microorganisms
and disease
– Was not verified until Robert Koch (Koch’s
Postulates) proved this by experimenting with
mice and anthrax cultures in the 1880s.
Types of microbes
• BACTERIA
– Prokaryotes- ???
• No nucleus
• Unicellular
– Can be good or bad
• Normal flora
Normal Flora
Resident flora present
Sterile areas
Skin
Blood and cerebrospinal
fluid
Nose, pharynx, mouth
Lungs, stomach
Colon, rectum, vagina,
distal urethra
Uterus, fallopian tubes,
ovary; bladder and
kidney
Bacteria continued…
• Classified by their shape
– Cocci = round (MRSA)
– Bacilli = tic-tac or rod shaped (Clostridium
tetani)
– Spirilla = spiral (Treponema pallidum)
Bacterial Structure
• Cell walls are either
– Gram positive: has peptidoglycan in the cell
wall  stains purple
– Gram negative: no peptidoglycan in the cell
wall  stains pinkishy red
• Antibiotics work on the cell walls of
bacteria, that’s why they cannot hurt our
cells!
• Bacteria usually cause disease by
producing toxins and/or enzymes
– Exotoxins- usually produced by G+. Can
interfere with nerve conduction (neurotoxin),
cause vomiting (enterotoxin). Stimulate
antibody production
– Endotoxins- usually produced by G-. Released
once the bacteria dies. Causes fever,
weakness, serious effects on circulatory
system.
– Enzymes- you already know
Last bit of bacteria stuff
• Bacteria can form spores
– Allow bacteria to survive long periods; highly
resistant (tetanus and botulism).
• Bacteria repro. By binary fission
VIRUSES
• Non-living- do NOT listen to your book!
– Requires a living host to reproduce
• Capsid (protein coat) surrounding some
DNA(usually) or RNA.
– If RNA, its called a retrovirus…can you name
a retrovirus?
How viruses cause disease
• Attach to host cell and injects its genetic
material
• Uses the host cell’s machinery to
reproduce
• Lyses the cell (too many virus babies
makes the cell explode)
• Some can enter latent phases
• Viruses are famous for mutating
– Flu, colds
• Difficult to control
• Some are capable of causing cancer
because they alter the host’s DNA…think
HPV and link to cervical cancer.
Infection Part 2
Chapter 4
K. Harris
Major Grade Poster
• Create a disease awareness poster for your
assigned disease
• Must include:
–
–
–
–
–
–
–
Prevelance/incidence/death rate
Is it epidemic or pandemic
Signs and symptoms
Potential complications
Geographic location of disease
Pictures
Pathophysiology of the disease
Fungal Infections
• Fungi are found everywhere.
– Usually on places where its warm and moist.
• Fungal Infections are also called mycotic
infections.
• Eukaryotic
– Uni or multicellular
Good vs. Bad
• Just like bacteria and people, some fungi
are good and some fungi are bad.
– Good: a source of antibiotic drugs like
penicillin
– Bad: the ones that cause disease.
Examples of Fungal Diseases
• Athletes foot
• Candida species
– Cause of vaginal yeast infections and thrush
in infants
• Histoplasmas cause lung infections
Protozoan Infections
• Also called protists
– Eukaryotic, can be uni or multicellular
• Examples include malaria, trichomonas,
amebic dysentery, etc.
Other parasites
• Helminths (actually worms…ewww…)
– Eggs and larvae are found in contaminated
water and can be ingested.
Transmission of infection
• Direct contact
• Indirect contact (contaminated food or
surfaces)
• Droplet transmission (oral or respiratory)
• Vector borne (carried by insect or other
animal)
• Nosocomal infections- occurs in a
healthcare facility
Host Resistance
• Interferons are produced by host cells in
response to a virus to help nearby cells
become resistant to viral attachment.
• Age, genetics, immunodeficiency,
malnutrition, chronic disease
Other terms
• Pathogenicity- capability to become
disease
• Virulence- degree of pathogenicity
– Mutation of microbe
• “Superbugs” like MRSA---huge issue,
especially in hospitals.
Infection Control
•
•
•
•
Isolation; quarantine
Universal precautions like handwashing
Sterilization of materials (autoclaving)
Disinfectants- chemicals to clean
inanimate objects
• Antiseptics- chemicals to clean animate
objects
Onset and Course
• Incubation period, then prodromal period,
then acute period, then (usually) recovery.
• If not recovery:
– Chronic infection
– Septicemia- life threatening, systemic,
infection is active in the bloodstream (BAD)
Signs and symptoms
• Local: inflammation- pain, swelling,
redness and warmth; purulent exudate if
infection is bacterial in nature; serous
exudate if viral; necrosis
• Systemic: fatigue, nausea, headache,
pyrexia, subnormal temp., disorientation,
seizures
Diagnosis
• Culture/staining to figure out what
specifically is causing the infection
Drugs
• Usually, body can fight off infection on its
own. Sometimes, drugs are required.
• Prophylactic treatment- given as a
precaution.
Types of drugs
• Antibiotic- derived from living organisms
(usually molds like penicillin and
amoxycillin)
– Broad spectrum: both G+ and G– Narrow spectrum: either G+ or G-, not both
• Better because it is less likely to kill normal flora
• Antibacterials, antivirals, antifungals
• Bactericidal- kill bacteria
• Bacteriostatic- reduce reproduction rate
DRUUUUUUUUUUUGS
• How do they work?
– Read and take notes on mode of action for
infection fighting drugs on pgs 98-99.
– In your notes, after your summary, answer
the Think About questions on page 99.
Current Event
1. Write three cause/effect statements
from the article.
2. What are the potential problems of
antibiotics becoming obsolete.
3. Write a letter to your senator
explaining the problem and what you
think should be done about it.
Current event article
http://www.cnn.com/2009/HEALTH/10/01/ant
ibiotic.penicillin.resistance/index.html?iref=
newssearch