Infectious Diseases
BIOMEDICAL TECHNOLOGY
Part One
OVERVIEW
* An Infectious Disease is a disease that is
caused by the invasion of a host by agents
whose activities harm the host’s tissues.
* They cause disease (by impairing normal tissue
function) and can be transmitted to other
individuals (they are infectious)
Vocabulary
• Pathogens – Microorganisms that are capable
of causing disease.
• Infection – Results when a pathogen invades
and begin growing within a host.
• Disease – results only if and when tissue
function is impaired (i.e. burns, skin lesions)
Infectious Process
• The body has defense mechanisms to prevent
infection and to prevent disease after
infection occurs.
• In order to cause disease, pathogens must be
able to enter the host body, adhere to specific
host cells, invade and colonize host tissues,
and inflict damage on those tissues.
Infectious Process Cont.
• Entrances to the host: mouth, eyes, genital
openings, or wounds.
• Growth of pathogens or the production of
toxins/enzymes cause disease.
• Some normal flora prevent disease.
Latent Period
• A "latent period" is the lag time between
exposure to a disease-causing agent and the
onset of the disease the agent causes.
• For instance, the latent period between
exposure to HIV infection and the onset of
AIDS may be many years.
• Example: Magic Johnson
MICROBES THAT CAUSE
INFECTIOUS DISEASES
BACTERIA
• Small unicellular microorganism that
multiplies by cell division.
• Found as bacillus (rod shaped), coccus
(spherical), or spirillum (spiral)
• Anthrax, Cholera, Legionellosis, Lyme Disease,
Salmonellas, Strep, TB, Typhoid, Yersinia pestis
(plague)
• Treatable with antibiotics
Bacteria Cont.
• Staphylococcus aureus (Staph)
– Favorite hangout: skin and nose
– Likes: getting inside the body where it can cause a minor
infection like a boil, or serious, sometimes fatal infections
such as blood infections or pneumonia.
– Dislikes: many antibiotics
Bacteria Cont.
• AEROBES
• Reproduces only in the
presence of oxygen
• ANAEROBES
• Reproduce only in the
absence of oxygen
Facultative anaerobic bacteria:
can produce in either environment
BACTERIA EXAMPLES:
Gram negative
– SALMONELLA
Gram positive
– STAPHYLOCOCCUS
Staph infections
• Flesh eating early
• Impetigo
•Flesh Eating
bacteria ADVANCED
Yersinia Pestis (looks like Pests)
• Bacterium that
causes Plague
• Transmitted via
rodents typically
VIRUSES
Viruses
• Apart from the host cell, have no metabolism
and cannot reproduce or survive unless they
take over a living cell
Retroviruses – a classification of
viruses
• HIV
• Certain types of
CA
• Retroviruses are
viruses whose
genome consists
of RNA not DNA.
Think about IT
• In February 1997 it was
reported that pig cells
contain a retrovirus
capable of infecting
human cells. This is
troublesome because of
the efforts that are being
made to transplant pig
tissue into humans (e.g.,
fetal pig cells into the
brains of patients with
Parkinson's disease/
hearts etc).
Virus Examples
•
•
•
•
•
•
•
•
Chicken pox
Cold sores
Genital herpes
Shingles
Small pox
AIDS
Influenza
Rabies-direct
contact
• West Nile Virus
• Ebola →
• Hantavirus
• Many viruses are preventable via
vaccinations
• Can be treated with Antiviral drugs
• ANTIBIOTICS do not work
Smallpox virus
More virus examples:
• Rhinovirus
– The common cold
• Influenza
• Measles
• Mumps↓
Rotaviruses
• Gastroenteritis
• Wheel shaped virus
causing diarrhea
• Every year it kills
approximately 1 Million
children world wide
FUNGI
Fungi
• Have a cell wall and a
cell membrane
• Includes molds and
yeast
• Treat with antifungal
medication, sometimes
with antibiotics.
Fungi examples
•
•
•
•
Ringworm
Histoplasmosis
Athletes foot
Thrush
• Yeast or candida are
opportunists
• Yeast infections are the most
common opportunistic
infection
• Antibiotics reduce normal flora
and allow yeast to grow
making the pt susceptible to
an opportunistic infection
PROTOZOA
• Acquired through contaminated food or water,
or bite of an arthropod (mosquito)
• More common in wet climates like the tropics
• Amoebic dysentery
• Malaria- re-emerging d/t drug resistance and
fear of vaccination
• Treatable with antibiotics
HELMINTHS (WORMS) ewwww!
• Simple, invertibrate animals, some infectious
parasites
• In intestine, blood, body tissue
• Medications to force evacuation or death of
worms
• Swimmer’s itch in US
– Schistosoma (flatworm)
– Symptoms include
abdominal pain and
diarrhea
• Trichinella spiralis
(roundworm)
– Ingested in undercooked
pork from infected pigs.
– Symptoms include
vomiting, diarrhea, and
abdominal pain
SEE NEXT SLIDE FOR PICTURE!!!
Filariasis
Filariasis- worm infestation in lymphatic system that
prevents normal draining of lymphatic fluids. Causes
SEVERE swelling.
PRIONS (pree-ons)
• Extremely small
particles that consist
only of protein.
• Resistant to heat and
Disinfectants
• No known treatments
– Creutzfeldt-Jakob disease
– “mad cow disease”
in cattle