Download Chapter 5/Microbiology

Chapter 5/Microbiology
Joe Pistack MS/ED

Disease-failure of the body to function
normally.

A leading cause of disease in humans is
invasion of the body by pathogens.

Pathogen-disease-producing
microorganism.
Disease

Infection-invasion of the body by a
pathogen and the symptoms that develop
in response to this invasion.

Localized infection-restricted to a small
area of the body.

Systemic infection-widespread infection
throughout the body, usually spread by
the blood.
Infection

Bacteria-single-cell organisms found
everywhere.

Normal flora-organisms that normally
and harmoniously live in or on the human
body without causing disease.

Prevents the overgrowth of other
organisms, keeps them under control.
Microorganisms (Microbes)

Bacteria make up the largest group of
pathogens.

Successful invasion of pathogens can
cause damage in two ways:
(1)-entering and growing in the human
cell.
(2)-secreting toxins that damage the
cells.
Bacteria

Bacteria are classified into three groups
based on shape:
(1)coccus (round)
(2)bacillus (rod-shaped)
(3)curved rod

Rickettsiae and chlamydiae are also
classified as bacteria, although they differ
in several ways from cocci, bacilli, and
curved rods.
Classification of Bacteria

Cocci-round cells
arranged in patterns.

Diplococci-cocci
arranged in pairs.

Staphylococci-look like
bunches of grapes and are
arranged in clusters.

Cocci- responsible for
many diseases such as
gonorrhea, meningitis and
pneumonia.
Cocci

Bacilli-long and
slender and shaped
like a cigar.

Diseases caused by
bacilli include
tetanus, diphtheria,
and tuberculosis.
Bacilli

Curved rodsinclude: vibrio
spirillum
spirochete

Cholera is caused by
the vibrio.
Tightly coiled spirilla
are called spirochetes
and are the cause of
syphilis.

Curved Rods

Many bacteria form spores, they allow the
bacteria to survive in a dormant state during
extreme conditions or when exposed to
disinfectants.

When the conditions improve, the spores will
wake from their dormant state and resume
activity.

Ex. Clostridium botulinum, causes a deadly form
of food poisoning. The spores that cause this
disease can withstand several hours of boiling
water.
Bacteria

Rickettsia and chlamydia are classified as
bacteria, they are smaller than most
bacteria and must reproduce within the
living cells of a host.

Called parasites, because they require a
living host.

Rickettsia are often carried by fleas, ticks
and body lice.
Bacteria

Chlamydiae are smaller than rickettsiae and
cause several diseases.

Chlamydia trachomatis is responsible for one
of the most prevalent sexually transmitted
diseases in the US today.

Chlemydial infection is also responsible for
trachoma, a serious eye infection that is the
leading cause of blindness in the world.
Bacteria

Virus-smallest infectious agent.

Viruses are parasites, they can only
reproduce within the living cells of a host.

Ex. of viral diseases, measles, mumps,
influenza, poliomyelitis and AIDS.

Most upper respiratory infections are viral
and are not responsive to antibiotics.
Viruses
Virus

Fungus-plantlike organism, grows best in
dark, damp, places.

Mycotic infections-pathogenic fungal
infections. Usually localized.

Ex. of fungal infections include athlete’s
foot, ringworm, thrush, and vaginitis.
Fungus




Fungal infection
that causes
redness, itching,
burning.
Mildly contageous.
Passed by direct
contact such as
walking in locker
rooms or around
pools.
Rx. Topical
antifungal lotion.
Athlete’s Foot




Skin infection
caused by a fungus.
The fungus grows
outwards from the
center.
Skin becomes itchy,
red, raised scales
that may blister and
ooze.
Rx. Antifungal
lotions or pills.
Ringworm

Protozoa-single-cell, animal-like
microbes.

Found in soil and most bodies of water.

The parasites are ingested in
contaminated water and food and cause
diarrhea.
Protozoa

Helminths-multicellular animals that are
parasitic and pathogenic to humans.

Microscopic examination of body samples
is required to identify the worm.

The worms are classified as round-worms
and flat-worms.
Parasitic Worms

Pinworm is a type of roundworm that is
common in children.

The pinworm lives in the intestinal tract
but deposits their eggs on the outer
perianal area.

The deposition of the eggs causes itching,
(pruritis).
Parasitic Worms

The child may scratch the anal area and
transfer the eggs to the mouth.

The eggs are swallowed and newly
hatched pinworms grow into adulthood in
the intestine.

This transfer of eggs is called the fecaloral route.
Parasitic Worms
Pinworms

Tapeworm-form of flatworm.

Acquired by eating poorly cooked
contaminated food such as beef, fish, or
pork.

Tapeworms that live in the intestines may
grow from 5ft. To 50ft. In length.
Flatworms




Tapeworms attach
to the intestines of
the host.
Once anchored to
the intestinal wall
the tapeworm
absorbs nutrients
through it’s skin.
Symptoms include
increased appetite,
insomnia irritability.
Rx. Medications.
Tapeworms

Ectoparasites-arthropods with jointed
legs and include insects and ticks.

They live on the skin and mucous
membrane.

Cause itching and discomfort.

Ex. lice, insects and ticks.
Ectoparasites

Mosquitoes, biting flies, fleas, and ticks
act as vectors of disease.

Vector-object, living or non-living, that
transfers a pathogen from one organism
to another.

The bite of the vector introduces
pathogens into the host causing infection.
Ectoparasites

Mosquito can carry
the pathogens for
malaria and
encephalitis.

The tick can carry
the pathogen that
causes Lyme
disease and Rocky
Mountain Spotted
Fever.

Ectoparasites

Methods of identifying pathogens:
(1) Gram stain
(2) Culture
Gram stain-bacteria are classified
according to staining characteristics.
 A dye is used to gram-stain the bacteria,
gram-positive bacteria will stain purple or
blue. Ex. streptococcus

Laboratory Identification

Gram-negative-bacteria will not absorb
the dye, it will pick up a pink or red stain.
Ex. Escherichia coli

Bacteria is either gram-positive or gramnegative, gram staining may be an
important step in identification of
organisms.
Laboratory Identification
Acid-fast stain-the bacteria is first
stained with a red dye and then washed
with an acid.
 Many bacteria lose the red stain when
washed with acid, but several others
retain the red stain and are therefore
called acid-fast.
 Ex. Mycobacterium tuberculosis (TB).

Laboratory Identification
Gram stain

Culture-growth of pathogens in a culture
medium. Ex. Wound drainage

Culture and sensitivity-when the
pathogen is cultured for susceptibility to
various antibiotics.

Antibiotic is placed in the same culture
and stops the growth of the pathogen, it
is assumed to be sensitive to the
antibiotic.
Laboratory Identification
Culture and Sensitivity
Modes of Transmission

Portal of Entryhow pathogens
enter the body.

Portals of entry
include:
Respiratory tract
GI tract
GU tract
Eyes
Skin
Portal of Entry

Parenteral routeincludes injuries
that penetrate the
skin or mucous
membranes such as
bites, cuts, or
surgery.

Break in the skin is
an excellent way for
pathogens to enter
the body.
Portals of Entry
Portals of Exit-the
way that pathogens
leave an infected
body.
 Portals of exit
include:
Respiratory tract
GI tract
GU tract
Eyes(tears)
Breasts (milk)

Portals of Exit



Most common exits
are the respiratory
and gastrointestinal
tracts.
Ex. Cold virus is
sneezed or coughed
into room air from
the passages of the
infected person.
Salmonella is
excreted in stool.
Portals of Exit

By knowing the
portal of exit we
can set up
procedures or take
precautions to
prevent the spread
of disease.
Preventing Infection





Pathogens are
spread :
Person to person
Environment to
person
Insects to person
Most important
procedure in the
prevention the
spread of disease is
Handwashing!
Preventing Infection

An infected person can spread germs by
coughing or sneezing.

When a person sneezes, the cold virus is
sprayed into the room in droplets.

The droplets are inhaled by co-workers.

The virus is spread by droplet contact.
Person-to-Person Contact

A person with contaminated hands
touches other objects in the office, ex.
doorknobs, desktops, handshaking.

Vector-an object, living or non-living,
that transfers a pathogen from one
organism to another.

Fomite-nonliving vector.
Person-to Person Contact
Person-to-Person Contact

This mode includes contact with
contaminated water, air, food, or soil.

Ex. You can develop food poisoning if you
eat food contaminated with E-coli.
Environment-to-Person Contact

Insects act as vectors to transmit disease.

Ex. A mosquito bites a person with
malaria, the malaria germ matures in the
stomach of the insect. The insect then
bites another person.
Animal-to-Person Contact

A hospital acquired infection- formerly
known as nosocomial infection

Most often transmitted from person to
person by direct contact.

Most frequently spread by professionals
who Do Not Wash Their Hands!
Nosocomial Infections
Prevent the Spread of Infection