Microbiology- Chapter 18 (Microbial Diseases Of The Skin And Eyes)

Front 1

What is the largest organ in the body?

Back 1

The skin

-Sometimes shows symptoms of illness not associated with skin (rash)

Front 2

Describe the structure of skin.

Back 2

Epidermis:
-Thin outer part, composed of layers of dead epithelial cells – stratum
-Replaced every 25-45 days
-Physical barrier against microbes

Dermis:
-Connective tissue; hair follicles, sweat glands, oil glands, neurons
-Sebaceus glands- softens and lubricate the skin

Front 3

Describe the normal microbiota of the skin.

Back 3

-Normally harmless, able to survive on the skin resistant to drying and high concentration of salt
-These microbes cannot be completely removed through cleansing
-Those in hair follicles and sweat glands reestablish rapidly-responsible for body odor
-May be opportunistic pathogens

Representatives
-Gr + cocci (Staphylycococcus, Micrococcus)
-G+ pleomorphic rods- diphteroids;
Propionibacterium acnes-anaerobic bacteria, inhabit hair follicles, produce propionic acid (maintains the acidity of the skin, pH 3-5)
-The yeast, Malassezia – cause skin scaling dandruff

Front 4

What is acne?

Back 4

-The most common skin disease caused by Propionibacterium acnes

Front 5

Why does acne happen?

Back 5

-Normally, dead cells and sebum are discharged through pores to skin surface
-Overproduction of sebum leads to clogging the pores
-Propionobacterium acnes digests the oily material-fatty acids are produced
-Bacterial antigens + fatty acids causes local inflammation

Front 6

what is Staphylococcus Aureus?

Back 6

Staphylococcus Aureus

-The most pathogenic are coagulase positive (blood clot protects them against phagocytosis)
-Found in hospital environments, resistant to antibiotics, difficult to treat.

Staphylococcal skin infection

-Staphylococci- spherical gr+ bacteria; form irregular clusters
-Two groups:
Coagulase “+” strains
Coagulase “-“ strains
-Coagulase positive strains coagulate (clots) fibrin in blood.
-Coagulase negative strains make up 90% of normal microbiota. Pathogenic only when the skin is broken. (Staphylococcus epidermidis)

Front 7

Staphylococcus Aureus causes infection of hair follices.

True or false?

Back 7

True

Causes infection of hair follicles

-Folliculitis –mild superficial inflammation of hair follicles
-Furuncle- more serious folliculatis
-Carbuncle-extensive damage of neighboring tissue

Front 8

Describe strepotococus.

Back 8

-Spherical, Gr+ bacteria forming chains

-There are two groups of streptococci:
-Beta-hemolytic: (hemolysins lyse red blood cells and other cells) -Alpha-hemolytic: (non-hemolytic)

-The most important Streptococcus belongs to group A (also called Streptococcus pyogenes)

Front 9

What is Scaled Skin Syndrome and whats is caused by?

Back 9

Scaled Skin Syndrome (peeling off the skin)- skin infection of newborns and children under age 2)

-Caused by staphylococci that were lysogenized by certain phages
-Toxins (A&B) are responsible for damage
-The patient is vulnerable to secondary infection

Front 10

What is impetigo and whats it caused by?

Back 10

-Caused by Staphyloccus aureus or Streptococcus pyogenes

-Skin lesions- small patches on the skin and limbs

-Develops into pus-filled vesicles that can itch intensely
-Spread by contact- highly contagious
-Virulence factor (S. aureus) exotoxins A and B- dissolve the cell cement
-Treatment- antibiotics- protein inhibitors (cephalexin)

Streptococcus pyogenes:
-Sometimes the skin infection can spread to deeper tissue- Necrotizing fasciitis –“Flesh eating bacteria”
-Rapid destruction of tissue
-Hyaluronidase – dissolves the connective tissue
-Exotoxin A – acts as superantigen- causes a massive immune response that is useless- immune system to contribute to damage
-15,000 cases in US each year

Front 11

What is gangrene and whats it caused by? And whats the treatment for it?

Back 11

-Caused by anaerobic spore- forming bacterium Clostridium perfigens

-Occurs when the blood supply to the tissue is interrupted
-The dying tissue provides anaerobic conditions for the growth of Clostridium
- Toxin produced by the bacterium causes necrosis of neighboring tissue (muscles)
-Gas is also produced that swells the tissue
-Treatment: Penicillin, surgical removal of necrotic tissue, hyperbaric chamber (oxygen penetrates the tissue)

Front 12

What are pseudomonads and what infections does it cause?

Back 12

-Aerobic, Gr- bacteria with polar flagella
-Found in water and soil
-Representative- Pseudomonas aeruginosa-opportunistic pathogen
-Causes dermatitis – rash, associated with swimming in pools
-P. aeruginosa is a common pathogen in burn patients
-Treatment: antipseudomonal Beta-lactame antibiotics

Front 13

What is the treatment for pseudomonads infections?

Back 13

Treatment: antipseudomonal Beta-lactame antibiotics

Front 14

List the viral diseases of the skin.

Back 14

--Warts
-Smallpox (Variola)
-Chickenpox (Varicella)
-Herpes simplex
-Measles (Rubeola)
-Rubella (German measles)

Front 15

What enables the chickenpox virus to remain latent?

Back 15

-The virus persist inside the nerve cell as viral DNA
-Not recognized by the immune system
-Later the virus may be reactivated (by stress) when it moves along the nerve to skin area.
-It causes a new outbreak (shingles (herpes zoster))

Front 16

Describe warts.

What causes it, how its transmitted and how its treated.

Back 16

-Warts
-Caused by human papillomavirus (HPV-80 types)
-Common in children
-In 70% of cases disappear on their own

-Transmitted by
-contact
- sexual contact- genital warts
-respiratory routs

-Treated by
-Liquid nitrogen (very low temp), electrical current, burning with acids, laser treatment

Front 17

Describe Smallpox (Variola)

What causes it, how its transmitted and how its treated.

Back 17

-Caused by orthopoxyvirus

-Two forms:
Variola major- mortality 20 %
Variola minor-mortality less than 1%

-Transmitted by the respiratory route and contact
-Symptoms: skin lesions; postules after 10 days
-The first vaccine- the one against smallpox
-Incubation period: 12 to 14 days

-Treatment: immediate vaccination
-The first disease that was eradicated
-Prevention: Vaccination was discontinued in 1972

Front 18

Describe chickenpox (Varicella)


What causes it, how its transmitted and how its treated.

Back 18

-A mild childhood disease.
Mortality rate is very low
-The disease is caused by herpesviruse varicella-zoster (human herpesvirus 3)
-Acquired through respiratory droplets or fluid of active skin lesions
-Skin lesions manifest the disease
-Virus moves from the skin to nerve cell near the spine
-There it remains latent
-Self-limiting

Front 19

Describe herpes simplex.

- What are the two types

Back 19

-Two groups: HSV-1 and HSV- 2
Herpes simplex virus

type 1
-Infection is manifested with lesions in the oral mucous membrane- “cold sores” or “fever blisters”
-90% of population infected- many subclinical

Type 1- The virus is latent in the nerve that communicates between face and central and nerve system (trigeminal nerve)
-Sunburn, emotional stress and hormonal changes can cause reappearance of the infection

Type 2- genital herpes
-Can be differentiated from HSV-1 by its antigenic makeup
-Transmitted by sexual contact
-Latent in the sacral nerve ganglia

Front 20

Describe Measles (Rubeola)

Back 20

-Acquired by the respiratory route
-Symptoms similar to common cold, rash on the face and trunk, lesions in the mouth
-Complications-pneumonia, encephalitis
-The law requires vaccination for school children- not earlier
-Dangerous disease for very young and very old people

Front 21

Describe Rubella (German measles)

Back 21

-A mild viral disease
-Manifestation-light fever, small red spots
-If contracted by pregnant woman a fetal damage is possible (deafness, heart defects, mental retardation)
-Rubella is prevented by effective vaccine (not recommended for pregnant women)

Front 22

List and describe the fungal diseases of the skin.

- What its caused by, treatments.

Back 22

-Dermatomycoses – fungal infection of skin, nails, hair (keratin) :
– ringworm
-Can digest keratin
-Transmitted by contact with fomites (non living objects)
-Ringworm of the groin – tinea cruris
-Ringworm of the feet- tina pedis- athlete’s foot
-Ringworm of the scalp- tina capitis

Candidiasis:

-Infection caused by the yeast Candida albicans
-C. albicans can overgrow the mucosal tissue when the normal microflora is suppressed (antibiotic treatment)
-In newborn infants, whitish overgrowth in the mouth cavity
-Treatment- miconazole, nistatin

Front 23

List the microbial diseases of the eye.

Back 23

-Conjunctivitis

-Neonatal gonorrheal ophtalmia

-Trachoma

-Acanthamoeba keratitis

Front 24

Describe Conjunctivitis

Back 24

Conjunctivitis (red eye)- inflammation of conjunctiva (mucous membrane that lines the eyelids and covers the eye ball)

-Can be caused by bacteria or viruses
-Bacterial conjunctivitis is caused by Heamiphilus influenza and Pseudomonas

-Source of infection- skin, upper respiratory tract and contact lenses

Front 25

Describe Neonatal gonorrheal ophtalmia

What causes it?

Back 25

-Conjunctivitis caused by Neisseria gonorrheae
-Contracted as the infant passes through the birth canal
-Newborns used to be treated with silver nitrate

Front 26

Describe trachoma.

_cause
_Symptoms
_ Treatment

Back 26

-Infectious disease caused by Chlamidia trachomitis (intracellular parasite)
-The most often cause of blindness
-C. trachimatis –causes conjunctivitis – thicken the upper eyelid
-Mechanical damage of cornea caused by in turning of eyelashes
-Treatment- tetracycline

Front 27

Describe Acanthamoeba keratitis

Back 27

-A protozoa- causes inflammation, in later stage- sever pain
-Found in fresh water, tap water, hot tubs
-Infections associated with contact lenses
-Damaged cornea is susceptible to infection