Notes Unit 18
Contact Diseases
Structure and Function of the Integumentary (Skin) System
The human skin consists of two principal parts:
 Epidermis – the outer portion, composed of several layers of epithelial cells. The outer portion of this
consists of dead cells that contain a waterproofing protein called keratin. When unbroken, the epidermis
is an effective barrier against microorganisms.
 Dermis – the inner, relatively thick portion of skin, composed mainly of connective tissue. The hair
follicles, sweat gland ducts, and oil gland ducts in the dermis provide passageways through which
microorganisms can enter the skin and penetrate deeper tissues.
There are some other defenses against pathogens too:
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Perspiration contains salt, which inhibits many microorganisms and also contains the enzyme
lysozyme, which is capable of breaking down the cell walls of certain bacteria.
Sebum is secreted by the oil glands, and is a mixture of lipids, proteins, and salts. It can also inhibit the
growth of certain pathogens.
Membranes of the eyes are mechanically washed by tears, and the lysozyme in tears destroys the cell
walls of certain bacteria.
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Normal Flora of Skin
The skin does support the growth of certain microbes, which are normal. Those that normally exist on the skin
are resistant to drying and like high salt concentrations. Some of our normal flora are the staphylococci,
micrococci, and Propionibacterium acnes, which causes acne. Others include Corynebacterium xerosis, and a
yeast called Pityrosporum ovale, which is thought to be responsible for dandruff.
Types of Skin Lesions
Rashes and lesions on the skin DO NOT necessarily mean that you have an infection of the skin; in fact, many
systemic diseases affecting internal organs are manifested in skin lesions. There are different types of lesions,
and here are the descriptions of each:
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Vesicles – small, fluid-filled lesions (see diagram “a” below)
Bullae – vesicles larger than 1 cm in diameter, also fluid-filled (see diagram “b” below)
Macules – flat, reddened lesions (see diagram “c” below)
Pustules or papules – raised lesions. Called papules when no pus inside; pustules when pus is inside.
(see diagram “d” below)
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Important Diseases
1. Helicobacter Peptic Ulcer Disease
Causative Organism:
Type of Organism:
Pathogenicity:
Symptoms:
Hallmark:
Transmission:
Treatment:
Helicobacter pylori
Bacteria; spiral-shaped rod
Can grow in highly acidic environment of stomach
The most common ulcer symptom is gnawing or burning pain in the abdomen
between the breastbone and the belly button. The pain often occurs when the
stomach is empty, between meals and in the early morning hours, but it can occur
at any other time. It may last from minutes to hours and may be relieved by eating
food or taking antacids. Less common symptoms include nausea, vomiting, or
loss of appetite. Sometimes ulcers bleed. If bleeding continues for a long time, it
may lead to anemia with weakness and fatigue. If bleeding is heavy, blood may
appear in vomit or bowel movements, which may appear dark red or black.
Causes peptic ulcers
Unknown to date. Know it is passed from person to person somehow; it is more
common in conditions of overcrowding.
Antibiotics.
2. Leprosy (Hansen’s Disease)
Causative Organism:
Type of Organism:
Pathogenicity:
Symptoms:
Hallmark:
Transmission:
Treatment:
Mycobacterium leprae
Acid-fast bacteria; rod-shaped
Targets skin, nerves, and mucous membranes
The most severe symptoms of leprosy result from infection of the peripheral
nerves, which causes a deterioration of a person's sense of touch and a
corresponding inability to feel pain and temperature. People with peripheral nerve
damage may unknowingly burn, cut, or otherwise harm themselves. Repeated
damage may eventually lead to loss of fingers and toes. Also, damage to
peripheral nerves may cause muscle weakness, at times resulting in clawing of the
fingers and a "drop foot" deformity. Skin infection can lead to areas of swelling
and lumps, which can be particularly disfiguring on the face. Can lose body parts.
Disfiguring nodules; loss of body parts.
Although the mode of transmission of Hansen's disease remains uncertain, most
investigators think that M. leprae is usually spread from person to person in
respiratory droplets.
Antibiotics, usually taken for at least 2 years and with multiple types.
3. Staphylococcal Skin Infections
Causative Organism:
Type of Organism:
Pathogenicity:
Diseases Caused:
Staphylococcus aureus
Bacteria; Gram positive cocci in clusters
Produce toxins, which injure tissue. Toxins include leucocidin, which destroys
white blood cells; exfoliating toxin, which causes skin loss; enterotoxins, which
affect the GI tract.
Staph can cause a number of diseases, which are described below:
i. Folliculitis – infected hair follicle (occur as pimples)
ii. Furuncle (boil) – a type of abcess, where pus is in the tissue
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Symptoms:
Transmission:
Treatment:
iii. Carbuncle – when the body does not cure a furuncle, this is the stage of
the illness where you actually get sick with fever and are ill.
iv. Sty – forms when an eyelash follicle becomes infected
v. Impetigo – thin-walled vesicles form on skin of newborns that rupture and
crust over.
vi. Scalded Skin Syndrome – forms a lesion around the nose and mouth,
which develops into a bright red area that spreads. Skin peels off in sheets
when touched. Usually in kids under 2.
vii. Toxic Shock Syndrome – toxin enters the bloodstream from the bacterial
infection site, and causes fever, vomiting, and a rash. Can kill you.
Usually caused by not changing tampons frequently enough.
viii. Methicillin-resistant Staphylococcus aureus (MRSA) is a type of
bacterium that is resistant to certain antibiotics. These antibiotics include
methicillin and other more common antibiotics such as oxacillin, penicillin
and amoxicillin. Two ways you can get: hospital-acquired, and
community-associated. Staph infections, including MRSA, occur most
frequently among persons in hospitals and healthcare facilities (such as
nursing homes and dialysis centers) who have weakened immune systems.
MRSA infections that occur in otherwise healthy people who have not
been recently (within the past year) hospitalized or had a medical
procedure (such as dialysis, surgery, catheters) are known as communityassociated (CA)-MRSA infections. These infections are usually skin
infections, such as abscesses, boils, and other pus-filled lesions.
See each of the above.
From normal skin floral; invades when there is a break in tissue.
Antibiotics
4. Streptotoccal Skin Infections (GAS)
Causative Organism:
Type of Organism:
Pathogenicity:
Diseases Caused:
Streptococcus pyogenes; GAS stands for Group A Strep
Bacteria; Gram positive cocci in chains
Secrete toxins and enzymes as they grow; such as hemolysins, which lyse red
blood cells. Also produce streptokinases (dissolve blood clots), hyaluronidase
(destroys connective tissue), deoxyribonucleases (enzymes that degrade DNA),
and proteases (break down protein).
Strep can cause a number of diseases, which are described below:
Transmission:
Treatment:
1. Erysipelas – the skin erupts into red-dish patches with raised margins, which
can progress to local tissue destruction, and enter the blood stream causing
septicemia.
2. Impetigo – like Staph, Strep can also cause impetigo. Most common in
school-age children, causes pustules that become encrusted and rupture. The
bacteria penetrate the skin through an abrasion or insect bite.
3. Necrotizing fasciitis – when Strep attacks muscle covering, causing tissue
destruction. Also called “flesh-eating bacteria”.
4. Rheumatic Fever – an infection of the heart that can follow a strep throat
infection if it is not treated.
Normal flora; invades tissue when there is a break in it.
Antibiotics
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5. Infectious Mononucleosis (EBV)
Causative Organism:
Type of Organism:
Pathogenicity:
Symptoms:
Hallmark:
Transmission:
Treatment:
Epstein-Barr Virus
Virus
95% of adults between 35 and 40 years of age have been infected
Symptoms of infectious mononucleosis are fever, sore throat, and swollen lymph
glands. Sometimes, a swollen spleen or liver involvement may develop. Heart
problems or involvement of the central nervous system occurs only rarely, and
infectious mononucleosis is almost never fatal. Although the symptoms of
infectious mononucleosis usually resolve in 1 or 2 months, EBV also establishes a
lifelong dormant infection in some cells of the body's immune system. A late
event in a very few carriers of this virus is the emergence of Burkitt's lymphoma
and nasopharyngeal carcinoma, two rare cancers that are not normally found in
the United States
Swollen lymph nodes from kissing.
Intimate contact with the saliva of an infected person
None
6. Rabies
Causative Organism:
Type of Organism:
Pathogenicity:
Symptoms:
Hallmark:
Transmission:
Treatment:
Rabies virus
Virus
Very virulent; host usually does not survive.
Fever, headache, confusion, sleepiness or agitation. Can experience hydrophobia,
or fear of water. Urge to bite others. Salivate excessively.
Bite of an infected animal
From the bite of an infected animal; however, it is so infectious that just getting
some saliva from an infected animal on you can cause the disease. Usually found
in wild animals such as raccoons, skunks, bats, foxes, and coyotes. Cats, cattle
and dogs are the most frequently reported domestic animals with rabies.
Antirabies vaccine after bite.
7. Ebola Hemorrhagic Fever
Causative Organism:
Type of Organism:
Pathogenicity:
Symptoms:
Hallmark:
Transmission:
Treatment:
Ebola Virus
Virus
High mortality rate
Fever, headache, joint and muscle aches, sore throat, weakness, diarrhea,
vomiting. Rash, red eyes, hiccups, and internal & external bleeding.
Bleeding out of body orifices; frequently fatal.
First transmission is from a monkey to a human; once infected, that person can
transmit the virus in several ways. Can happen by direct contact with the blood
and/or secretions of an infected person. Thus, the virus is often spread through
families and friends because they come in close contact with such secretions when
caring for infected persons. People can also be exposed to Ebola virus through
contact with objects, such as needles, that have been contaminated with infected
secretions.
None.
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8. Enterobiasis (Pinworm Disease)
Causative Organism:
Type of Organism:
Pathogenicity:
Symptoms:
Transmission:
Treatment:
Enterobius vermicularis
Helminth (worm)
Most common worm disease in U.S., affects mainly children.
Causes itching around the anus which can lead to difficulty sleeping and
restlessness. Symptoms are caused by the female pinworm laying her eggs in the
folds of the anus. Symptoms of pinworm infection usually are mild and some
infected people have no symptoms. Diagnose with “Scotch Tape Test”, where you
press scotch tape on the child’s anus at night, and eggs will adhere.
Pinworm infection is spread by the fecal-oral route, that is by the transfer of
infective pinworm eggs from the anus to someone’s mouth, either directly by
hand or indirectly through contaminated clothing, bedding, food, or other articles.
Pinworm eggs become infective within a few hours after being deposited on the
skin around the anus and can survive for 2 to 3 weeks on clothing, bedding, or
other objects. People become infected, usually unknowingly, by swallowing
(ingesting) infective pinworm eggs that are on fingers, under fingernails, or on
clothing, bedding, and other contaminated objects and surfaces. Because of their
small size, pinworm eggs sometimes can become airborne and ingested while
breathing.
Anti-helminth medication.
9. Schistosomiasis (Blood flukes)
Causative Organism:
Type of Organism:
Pathogenicity:
Symptoms:
Transmission:
Treatment:
Schistosoma sp. (japonicum, haematobium, mansoni)
Helminth (worm)
Can infect any part of the body. NOT found in U.S.
Within days after becoming infected, you may develop a rash or itchy skin. Fever,
chills, cough, and muscle aches can begin within 1-2 months of infection. Most
people have no symptoms at this early phase of infection. Eggs travel to the liver
or pass into the intestine or bladder, causing inflammation or scarring. Children
who are repeatedly infected can develop anemia, malnutrition, and learning
difficulties. After years of infection, the parasite can also damage the liver,
intestines, lungs, and bladder. Rarely, eggs are found in the brain or spinal cord
and can cause seizures, paralysis, or spinal cord inflammation. Symptoms of
schistosomiasis are caused by the body's reaction to the eggs produced by worms,
not by the worms themselves.
Infection occurs when your skin comes in contact with contaminated freshwater
in which certain types of snails that carry schistosomes are living. Freshwater
becomes contaminated by Schistosoma eggs when infected people urinate or
defecate in the water. The eggs hatch, and if certain types of snails are present in
the water, the parasites grow and develop inside the snails. The parasite leaves the
snail and enters the water where it can survive for about 48 hours. Schistosoma
parasites can penetrate the skin of persons who are wading, swimming, bathing,
or washing in contaminated water. Within several weeks, worms grow inside the
blood vessels of the body and produce eggs. Some of these eggs travel to the
bladder or intestines and are passed into the urine or stool.
Anti-helminth drugs.
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