chapter 18 infectious diseases affecting the skin and eyes

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Chapter 18 Chapter 18 Infectious Diseases Infectious Diseases Affecting the Skin and Affecting the Skin and Eyes Eyes

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Page 1: Chapter 18 Infectious Diseases Affecting the Skin and Eyes

Chapter 18 Chapter 18

Infectious Diseases Affecting Infectious Diseases Affecting the Skin and Eyes the Skin and Eyes

Page 2: Chapter 18 Infectious Diseases Affecting the Skin and Eyes

Skin Diseases Caused by Skin Diseases Caused by Microorganisms Microorganisms

18.4 Skin Diseases Caused by Microorganisms18.4 Skin Diseases Caused by Microorganisms

A. AcneA. Acne

1. Includes all follicle-associated lesions1. Includes all follicle-associated lesions

2. Causitive agent is 2. Causitive agent is Propionibacterium Propionibacterium acnesacnes

A) Digests the oil surplus resulting in A) Digests the oil surplus resulting in intense local inflammation that can intense local inflammation that can eventually burst the follicleeventually burst the follicle

3. No considered a communicable infection3. No considered a communicable infection

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4. Types of Lesions in Acne4. Types of Lesions in AcneA) Comedo – skin initially swells over A) Comedo – skin initially swells over

the pore leading out of a hair folliclethe pore leading out of a hair follicle1) Pore closed – whitehead1) Pore closed – whitehead2) Pore open but blocked with a 2) Pore open but blocked with a dark plug of sebum – blackheaddark plug of sebum – blackhead

B) Pustule or papule – when the lesion B) Pustule or papule – when the lesion erupts on the surfaceerupts on the surface

C) Cysts – pustules that come to C) Cysts – pustules that come to involve deeper layers of skininvolve deeper layers of skin

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B. Folliculitis, Hidradenitis, Furuncles, and B. Folliculitis, Hidradenitis, Furuncles, and CarbunclesCarbuncles

1. All are most often caused by 1. All are most often caused by Staphylococcus aureusStaphylococcus aureus

A) A) S. aureusS. aureus – the most serious – the most serious Staphylococcal pathogenStaphylococcal pathogen

1) Gram-positive cocci that form 1) Gram-positive cocci that form grape-like clusters; frequently found grape-like clusters; frequently found in the nostrils of virtually every in the nostrils of virtually every person at one time or anotherperson at one time or another

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2) Virulence Factors2) Virulence Factors

a) Capsule – inhibits phagocytosisa) Capsule – inhibits phagocytosis

b) Enzymesb) Enzymes

i) Coagulase – may impede progress i) Coagulase – may impede progress of leukocytes into infected areas by of leukocytes into infected areas by producing clotsproducing clots

ii) ii) -lactamase (penicillinase) – -lactamase (penicillinase) – degrades penicillindegrades penicillin

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c) Toxinsc) Toxins

i) Hemolysin – kills RBCi) Hemolysin – kills RBC

ii) Enterotoxin – causes symptoms in ii) Enterotoxin – causes symptoms in the GI tractthe GI tract

d) d) mecAmecA gene – provides resistance to gene – provides resistance to methicillin, penicillin, and other methicillin, penicillin, and other penicillin-like drugspenicillin-like drugs

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B) Folliculitis – inflammation of a hair B) Folliculitis – inflammation of a hair folliclefollicle

C) Hidradenitis – inflammation of a glandC) Hidradenitis – inflammation of a gland

D) Furuncle (boil) – when the infection D) Furuncle (boil) – when the infection extends from the follicle/gland into extends from the follicle/gland into surrounding tissues surrounding tissues

1) Results in localized redness, 1) Results in localized redness, swelling, tenderness, and painswelling, tenderness, and pain

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E) Carbuncle – larger, deeper lesion E) Carbuncle – larger, deeper lesion resulting from the aggregation and resulting from the aggregation and interconnection of multiple interconnection of multiple furunclesfuruncles

1) Results in the above furuncle 1) Results in the above furuncle symptoms plus several sites of symptoms plus several sites of draining pusdraining pus

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Skin Diseases Caused by Skin Diseases Caused by MicroorganismsMicroorganisms

C. ImpetigoC. Impetigo

1. Superficial bacterial infection1. Superficial bacterial infection

2. Causative agent can be either 2. Causative agent can be either Staphylococcus aureusStaphylococcus aureus or or Streptococcus pyogenesStreptococcus pyogenes

A) A) S. pyogenesS. pyogenes – the most serious – the most serious Streptococcal pathogen Streptococcal pathogen

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1) Catalase negative, Gram-positive cocci 1) Catalase negative, Gram-positive cocci in chains with Beta-hemolytic coloniesin chains with Beta-hemolytic colonies

2) Virulence factor2) Virulence factor

A) Streptolysin – destroys RBCA) Streptolysin – destroys RBC3. Highly contagious3. Highly contagious

A) Usually transmitted via direct A) Usually transmitted via direct contact but sometimes via fomitescontact but sometimes via fomites

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4. Usually seen in children4. Usually seen in children5. Causes the skin to flake or peel off 5. Causes the skin to flake or peel off

A) Looks like peeling skin, crusty and A) Looks like peeling skin, crusty and flaky scabs, or honey-colored crustsflaky scabs, or honey-colored crusts

B) Lesions usually found around B) Lesions usually found around mouth, face, and extremitiesmouth, face, and extremities

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6. Staphylococcal Impetigo6. Staphylococcal Impetigo

A) Superficial skin infection A) Superficial skin infection characterized by “weeping” pus characterized by “weeping” pus production (pyoderma)production (pyoderma)

7. Streptococcal Impetigo7. Streptococcal Impetigo

A) Marked by burning, itching lesions A) Marked by burning, itching lesions that break and weep forming a that break and weep forming a highly-contagious yellow crusthighly-contagious yellow crust

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D. D. Pseudomonas aeruginosaPseudomonas aeruginosa infections infections

1. Tend to be opportunistic pathogens 1. Tend to be opportunistic pathogens rather than true pathogensrather than true pathogens

2. It is a common cause of burn patient 2. It is a common cause of burn patient infections and is a leading cause of infections and is a leading cause of bacterial nosocomial pneumoniabacterial nosocomial pneumonia

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3. Can cause endocarditis, meningitis, 3. Can cause endocarditis, meningitis, skin rashes, UTI’s, external ear skin rashes, UTI’s, external ear infections in swimmers, as well as infections in swimmers, as well as corneal ulcers in contact wearerscorneal ulcers in contact wearers

4. Infections are characterized by a 4. Infections are characterized by a grape-like odor & bluish-colored pusgrape-like odor & bluish-colored pus

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E. Gas gangrene (Clostridial myonecrosis)E. Gas gangrene (Clostridial myonecrosis)

1. Primarily caused by 1. Primarily caused by Clostridium Clostridium perfringensperfringens

2. Bacteria or spores enter damaged tissue 2. Bacteria or spores enter damaged tissue and release exotoxins that cause necrosis and release exotoxins that cause necrosis of the surrounding tissues of the surrounding tissues

3. As a result hydrogen and carbon dioxide 3. As a result hydrogen and carbon dioxide gases are produced from fermentation of gases are produced from fermentation of amino acids and glycogen in the dead amino acids and glycogen in the dead tissuestissues

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4. Treatment involves removal of dead 4. Treatment involves removal of dead and infected tissue and may require and infected tissue and may require amputationamputation

A) There is no toxoid or vaccineA) There is no toxoid or vaccine

B) Hyperbaric oxygen treatment is B) Hyperbaric oxygen treatment is sometimes used to slow bacterial sometimes used to slow bacterial growth during treatmentgrowth during treatment

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F. Necrotizing fasciitis – “flesh-eating” F. Necrotizing fasciitis – “flesh-eating” diseasedisease

1. Occurs when aggressive strains of 1. Occurs when aggressive strains of Streptococcus pyogenesStreptococcus pyogenes or or Staphylococcus aureus Staphylococcus aureus contaminate contaminate skin woundsskin wounds

A) It is a rare condition and often A) It is a rare condition and often follows another infection that follows another infection that didn’t receive proper treatmentdidn’t receive proper treatment

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2. Releases toxins resulting in the 2. Releases toxins resulting in the destruction of fat & muscle tissue destruction of fat & muscle tissue along with the subcutaneous fasciaalong with the subcutaneous fascia

A) Toxins may spread via the A) Toxins may spread via the bloodstream resulting in organ bloodstream resulting in organ failure & deathfailure & death

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G. Chickenpox G. Chickenpox

1. Generally a mild disease, but in 1. Generally a mild disease, but in immunocompromised people, can be immunocompromised people, can be life-threateninglife-threatening

2. Caused by the Varicella-Zoster 2. Caused by the Varicella-Zoster Virus (VZV)Virus (VZV)

A) DNA virus that causes A) DNA virus that causes chickenpox and shingleschickenpox and shingles

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B) Chickenpox symptoms include fever B) Chickenpox symptoms include fever and a rash consisting of macules (small and a rash consisting of macules (small red spots), papules (little bumps), red spots), papules (little bumps), vesicles (small blisters), and finally vesicles (small blisters), and finally pustules (pus-filled blisters)pustules (pus-filled blisters)

1) The pustules eventually crust over 1) The pustules eventually crust over and fall off (scars may occur)and fall off (scars may occur)

2) The rash radiates in sparse crops to 2) The rash radiates in sparse crops to the extremitiesthe extremities

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3. Shingles can occur months or years after 3. Shingles can occur months or years after the primary chickenpox infection and is the primary chickenpox infection and is caused by latent virus harbored in sensory caused by latent virus harbored in sensory neuronsneurons

A) Upon reactivation the virus replicates A) Upon reactivation the virus replicates quickly resulting in skin lesions similar to quickly resulting in skin lesions similar to chickenpox except they may last for weekschickenpox except they may last for weeks

B) Inflammation of portions of the neurons B) Inflammation of portions of the neurons may also lead to pain and tenderness that may also lead to pain and tenderness that can last for monthscan last for months

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4. Because the chickenpox lesions are 4. Because the chickenpox lesions are itchy, many children are prone to itchy, many children are prone to secondary infection by secondary infection by S. pyogenes S. pyogenes or S. aureusor S. aureus

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I. Measles (Rubeloa)I. Measles (Rubeloa)

1. Caused by the Rubeola virus1. Caused by the Rubeola virus

2. Transmitted by direct contact with 2. Transmitted by direct contact with respiratory secretionsrespiratory secretions

A) Is one of the most contagious A) Is one of the most contagious diseasesdiseases

3. Symptoms include sore throat, dry 3. Symptoms include sore throat, dry cough, runny nose, and fevercough, runny nose, and fever

4. Characterized by the appearance of 4. Characterized by the appearance of small oral lesions known as Koplik’s spotssmall oral lesions known as Koplik’s spots

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5. Ultimately causes a skin rash starting at 5. Ultimately causes a skin rash starting at the head the progressing to the trunk the head the progressing to the trunk and extremities, then disappearing in and extremities, then disappearing in the same orderthe same order

6. Ear infections and pneumonia are 6. Ear infections and pneumonia are common secondary infectionscommon secondary infections

7. Is usually self-limiting (20-22 days from 7. Is usually self-limiting (20-22 days from the time of infection) but can cause the time of infection) but can cause complications in young children possibly complications in young children possibly lung or brain damagelung or brain damage

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MeaslesKoplik’s Spots

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J. Rubella (German measles)J. Rubella (German measles)

1. Caused by the Rubella virus1. Caused by the Rubella virus

2. 2 clinical forms2. 2 clinical forms

A) Postnatal – acquired after birthA) Postnatal – acquired after birth

1) Symptoms include mild fever, 1) Symptoms include mild fever, sore throat, and malaise sore throat, and malaise sometimes followed by a sometimes followed by a spreading pink rash or joint painspreading pink rash or joint pain

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2) About half of the infections are 2) About half of the infections are asymptomaticasymptomatic

3) Usually clears up in 2-3 days leaving 3) Usually clears up in 2-3 days leaving lifelong immunitylifelong immunity

B) Congenital – virus is obtained B) Congenital – virus is obtained in uteroin utero

1) First trimester exposure almost always 1) First trimester exposure almost always results in miscarriage or multiple, results in miscarriage or multiple, permanent defects of the eyes, ears, brain permanent defects of the eyes, ears, brain and heartand heart

2) Infants who survive excrete the virus for 2) Infants who survive excrete the virus for months after birthmonths after birth

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K. Fifth DiseaseK. Fifth Disease

1. Caused by Parvovirus1. Caused by Parvovirus

2. Begins as a reddish rash on the face 2. Begins as a reddish rash on the face resulting in a “slapped-cheek” resulting in a “slapped-cheek” appearanceappearance

3. The rash then spreads over the body 3. The rash then spreads over the body but is most prominent on arms, legs, and but is most prominent on arms, legs, and trunktrunk

4. Rash may last for days to weeks and 4. Rash may last for days to weeks and can recur during times of stresscan recur during times of stress

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L. RoseolaL. Roseola

1. Primarily caused by Human 1. Primarily caused by Human Herpesvirus 6 (HHV-6)Herpesvirus 6 (HHV-6)

2. Common in young children and 2. Common in young children and babiesbabies

3. Results in a high fever which can be 3. Results in a high fever which can be followed by a rashfollowed by a rash

A) However, most cases proceed A) However, most cases proceed without the rash stagewithout the rash stage

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4. Fever generally disappears on the 4. Fever generally disappears on the fourth day and rash can appearfourth day and rash can appear

5. It is thought that 100% of the 5. It is thought that 100% of the population has been infected with HHV-6 population has been infected with HHV-6 by adulthood even if no symptoms have by adulthood even if no symptoms have ever been seenever been seen

M. Warts (Papillomas)M. Warts (Papillomas)1. Affect children more than adults1. Affect children more than adults2. Benign squamous cell, epithelial 2. Benign squamous cell, epithelial

growths; may be covered with skin (wart) growths; may be covered with skin (wart) or mucus membrane (papillomas)or mucus membrane (papillomas)

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3. Caused by the Human Papillomavirus 3. Caused by the Human Papillomavirus (HPV)(HPV)

A) 3 main types of wartsA) 3 main types of warts

1) Common warts (seed warts)1) Common warts (seed warts)

a) Affect fingers and occasionally a) Affect fingers and occasionally other parts of the bodyother parts of the body

2) Plantar warts2) Plantar warts

a) Deep, painful warts on the a) Deep, painful warts on the soles of the feetsoles of the feet

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3) Genital warts3) Genital warts

a) Most common STD in the U.S.a) Most common STD in the U.S.

b) Range from tiny, inconspicuous b) Range from tiny, inconspicuous warts to large cauliflower-like warts to large cauliflower-like growthsgrowths

c) Primarily affects the external c) Primarily affects the external genitalia but may infect the cervix, genitalia but may infect the cervix, urethra, and anusurethra, and anus

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B) Some strains (both wart and non-wart B) Some strains (both wart and non-wart causing) of HPV have been linked to causing) of HPV have been linked to cervical and oropharyngeal cancercervical and oropharyngeal cancer

1) There are currently over 100 known 1) There are currently over 100 known strains with about 30 affecting the strains with about 30 affecting the genitaliagenitalia

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C) TreatmentC) Treatment

1) All 3 types of warts are commonly 1) All 3 types of warts are commonly removed by “freezing” them with liquid removed by “freezing” them with liquid nitrogen or by electrocautery (electric nitrogen or by electrocautery (electric burning)burning)

2) Aldara (imiquimod) cream is sometimes 2) Aldara (imiquimod) cream is sometimes used to treat external genital wartsused to treat external genital warts

3) Even with treatment warts have a 3) Even with treatment warts have a recurrence rate of between 10-40% recurrence rate of between 10-40% depending on the treatment useddepending on the treatment used

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N. Cutaneous AnthraxN. Cutaneous Anthrax

1. Most common and least dangerous 1. Most common and least dangerous version of infection with version of infection with Bacillus anthracisBacillus anthracis

2. Caused by endospores entering the skin 2. Caused by endospores entering the skin through small cuts or abrasions causing a through small cuts or abrasions causing a localized infection resulting in the localized infection resulting in the formation of a papuleformation of a papule

3. Papule that becomes increasingly 3. Papule that becomes increasingly necrotic then ruptures to form a black necrotic then ruptures to form a black eschar (scab)eschar (scab)

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O. Cutaneous Mycoses (Ringworm)O. Cutaneous Mycoses (Ringworm)

1. Dermatophytes are the most common 1. Dermatophytes are the most common cause of fungal skin infectionscause of fungal skin infections

A) Members of the genera A) Members of the genera Trichophyton, Microsporum, Trichophyton, Microsporum, andand EpidermophytonEpidermophyton

B) Confined to the nonliving B) Confined to the nonliving epidermal tissues and their epidermal tissues and their derivativesderivatives

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C) Products of fungal metabolism are C) Products of fungal metabolism are excreted into these areas resulting in excreted into these areas resulting in an immune response usually resulting an immune response usually resulting in redness and inflammationin redness and inflammation

D) Examples:D) Examples:

1) Tinea capitis – scalp1) Tinea capitis – scalp

2)Tinea barbae – beard (barber’s itch)2)Tinea barbae – beard (barber’s itch)

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3) Tinea axillaries – armpits3) Tinea axillaries – armpits

4) Tinea corporis – body (ringworm)4) Tinea corporis – body (ringworm)

5) Tinea cruris – groin (jock itch)5) Tinea cruris – groin (jock itch)

6) Tinea pedis – feet (athlete’s foot)6) Tinea pedis – feet (athlete’s foot)

7) Tinea manuum – hand7) Tinea manuum – hand

8) Tinea unguinum – nails 8) Tinea unguinum – nails

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Eye Diseases Caused by Eye Diseases Caused by Microorganisms Microorganisms

A. Conjunctivitis (pinkeye)A. Conjunctivitis (pinkeye)

1. Infection of the conjunctiva1. Infection of the conjunctiva

2. Bacterial conjunctivitis is often 2. Bacterial conjunctivitis is often caused by caused by Haemophilus aegyptius, Haemophilus aegyptius, Haemophilus influenzae, Haemophilus influenzae, Streptococcus pneumoniae, Streptococcus pneumoniae, Streptococcus pyogenes, Neisseria Streptococcus pyogenes, Neisseria gonorrhoeae, gonorrhoeae, and and Staphylococcus Staphylococcus aureusaureus

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3. Viral conjunctivitis is often caused by 3. Viral conjunctivitis is often caused by an Adenovirusan Adenovirus

4. Symptoms include a sensitivity to 4. Symptoms include a sensitivity to bright lights, swelling of the eyelids, bright lights, swelling of the eyelids, increased tears, redness, and large increased tears, redness, and large amounts of pusamounts of pus

A) Bacterial infections – milky A) Bacterial infections – milky dischargedischarge

B) Viral infections – clear exudateB) Viral infections – clear exudate

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B. KeratitisB. Keratitis

1. More serious infection than 1. More serious infection than conjunctivitisconjunctivitis

2. Invasion of deeper eye tissues occurs, 2. Invasion of deeper eye tissues occurs, can lead to complete corneal destructioncan lead to complete corneal destruction

3. Any microorganism can cause this 3. Any microorganism can cause this condition but the more common causes condition but the more common causes are the herpes simplex virusesare the herpes simplex viruses

A) Usually results from a “misdirected” A) Usually results from a “misdirected” reactivation of a cold sore causing HSVreactivation of a cold sore causing HSV

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B) May result due to direct contact of B) May result due to direct contact of the virus with the eye areathe virus with the eye area

4. Preliminary symptoms include gritty 4. Preliminary symptoms include gritty feeling in the eye, conjunctivitis, sharp feeling in the eye, conjunctivitis, sharp pain, and sensitivity to lightpain, and sensitivity to lightA) Symptoms are recurrent in 25-50% A) Symptoms are recurrent in 25-50%

of the casesof the cases5. Can lead to blindness5. Can lead to blindness

A) Is the leading cause of infectious A) Is the leading cause of infectious blindness in the U.S.blindness in the U.S.

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