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

Front 1

Describe the structure of skin.

Back 1

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 2

Describe the normal microbiota of the skin.

Back 2

-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 3

What is acne?

Back 3

-The most common skin disease caused by Propionibacterium acnes

Front 4

Why does acne happen?

Back 4

-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 5

what is Staphylococcus Aureus?

Back 5

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 6

Staphylococcus Aureus causes infection of hair follices.

True or false?

Back 6

True

Causes infection of hair follicles

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

Front 7

Describe strettococus.

Back 7

-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 8

What is Scaled Skin Syndrome and whats is caused by?

Back 8

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 9

What are pseudomonads and what infections does it cause?

Back 9

-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 10

List the viral diseases of the skin.

Back 10

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

Front 11

What enables the chickenpox virus to remain latent?

Back 11

-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 12

Describe warts.

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

Back 12

-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 13

Describe Smallpox (Variola)

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

Back 13

-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 14

Describe chickenpox (Varicella)


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

Back 14

-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 15

Describe herpes simplex.

- What are the two types

Back 15

-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 16

Describe Measles (Rubeola)

Back 16

-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 17

Describe Rubella (German measles)

Back 17

-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 18

List and describe the fungal diseases of the skin.

- What its caused by, treatments.

Back 18

-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 19

List the microbial diseases of the eye.

Back 19

-Conjunctivitis

-Trachoma

Front 20

Describe Conjunctivitis

Back 20

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 21

Describe trachoma.

_cause
_Symptoms
_ Treatment

Back 21

-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 22

What bacteria is found on skin, that is salt tolerant and produces antimicrobial substances that maintain balance?

Back 22

Staphylococci Epidermidis

Front 23

What term means 'pus' 'generating'?

Back 23

Pyogenic

Front 24

What are two causes of Pyogenic Infections

Back 24

Staphylococcus aureus
Streptococcus pyogenes