Download Lec 13 Microbial diseases of skin and eyes

Lecture 13: Microbial diseases of the skin and eyes
Edith Porter, M.D.
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 Skin
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Anatomy of the skin
Normal microbiota of the skin
Terminology for skin lesions
Bacterial infections of the skin
Viral infections of the skin
Fungal infections of the skin
Parasitic infections of the skin
 Eyes
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Anatomy of the eye
Bacterial infections of the eyes
Viral infections of the eyes
Protozoan infections of the eyes
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Rigid barrier due to keratin
Antimicrobial factors
 Salt
 Antimicrobial peptides
 Lysozyme
 Fatty acids
 Constant shedding
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Microbial entrance typically
through hair follicle and
sweat glands
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Gram-positive
bacteria
 Staphylococci
 Micrococci
 Corynebacteria
 Propionibacteria
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Exanthem or enanthem: skin or mucosa rash arising from another focus of infection
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Bacterial
 Staphylococcus aureus, Streptococcus pyogenes,
Pseudomonas aeruginosa, Propionibacterium acnes
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Viral
 Warts, small pox, chickenpox, shingles, herpes
simplex, Measles, Rubella, 5th disease, Roseola
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Fungal
 Candidiasis, ringworm
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Parasitic
 Scabies, lice, bed bugs
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Gram+cocci in clusters
Catalase +
Facultative anaerobe
Salt tolerant
Coagulase +
Leukocidin
Exfoliative toxin
Protein A (captures
antibodies)
Golden-yellow colonies
Antibody (Fc region)
SA
PrA
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Folliculitis
 Infections of hair follicles
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Sty
 Folliculitis of an eyelash
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Furuncle (boil)
 Abscess; pus surrounded
by inflamed tissue
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Abscess
 Inflammation of tissue
under the skin,
accumulation of pus,
walled off
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Also known as
Ritter’s disease
 Phage encoded
toxin (SSST)
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 exfoliation
Mostly in children <
2 years
 Toxemia
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Gram + cocci in pairs and chains
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Catalase negative
Facultative anaerobe
beta-hemolytic streptococci
Group A antigen
M protein (adherence and anti-phagocytic)
Streptolysin O
Hyaluronidase
Streptokinase
DNAse
Erythrogenic toxin (phage encoded)
 Responsible for red rash of scarlet fever!
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Localized
 Erysipelas
 Impetigo
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Invasive
 Cellulitis
 Necrotizing fasciitis
(flesh eating disease)
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Gram-negative rod
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Aerobic
Oxidase +
Non-fermenter
Pyocyanin produces a
blue-green pus
Pseudomonas dermatitis
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 Otitis externa
 Post-burn infections
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Comedonal acne
 Occurs when sebum
channels are blocked
by shedded cells
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Inflammatory acne
 Propionibacterium
acnes
▪ Gram + rods
▪ Anaerobic
▪ Skin flora
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Nodular cystic acne
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Pathogenesis
 P. acnes utilizes glycerol in sebum and
produces fatty acids (fermentation!)
 Fatty acids are pro-inflammatory
 Neutrophils are attracted further contributing
to inflammation
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Treatment
 benzoyl peroxide (antiseptic, dries out acne
lesions)
 Antibiotics (erythromycin, clindamycin)
 Isotretinoin (reduces sebum production,
TERATOGENIC, 30% of newborns with severe
damage)
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Ischemia
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Necrosis
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Death of tissue
Gangrene
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Loss of blood supply to tissue
Death of soft tissue
http://medicine.ucsd.edu/clinicalimg/Skin-Gangrene-DIC.jpg
Gas gangrene
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Clostridium perfringens, gram-positive,
endospore-forming anaerobic rod, grows in
necrotic tissue
Treatment includes surgical removal of
necrotic tissue and/or hyperbaric chamber
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Staphylococcus aureus: pus, abscess,
SSSS
Streptococcus pyogenes: impetigo,
erysipela
Pseudomonas aeruginosa: Otitis externa
Propionibacterium acnes: acne
Clostridium perfringens: gangrene
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Skin tumors (warts)
Exanthem
 Aerosol infection  viremia skin
manifestation
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Papillomaviruses (over 50
types in humans)
Benign skin growth
Some associated with
cancer
Infection by direct contact
Treatment
 Removal with ice, acid, lasers
 Interferon stimulation
 Interferon
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Smallpox (Variola)
 Variola major has 20 – 30 % mortality
 Variola minor has <1% mortality
 Vaccination:
▪ 15/1Mio life threatening side effects
▪ 1 – 2 deaths /1 Mio
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Emerging disease: Monkey pox
 Orthopox virus
 Only animal to human, not human to
human…yet!
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Varicella-Zoster virus (Human herpes virus 3, HHV-3)
Initially chicken pox
 Transmitted by the respiratory route, viremia, skin cell infection
 Causes pus-filled vesicles on face, throat, lower back, and sometimes
on chest and shoulders
 Rare complications: pneumonia, encephalitis, Reye’s syndrome in
conjunction with aspirin
 Virus may remain latent in dorsal root ganglia
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Recurrence as Shingles
 Reactivation of latent HHV-3 releases viruses that move along
peripheral nerves to skin
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Routine vaccination
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Human herpes virus 1 (HHV)
HHV-1 can remain latent in
trigeminal nerve ganglia
 Recurrent exacerbation
 Cold sores or fever blisters
(vesicles on lips)
 Herpes gladiatorum (vesicles on
skin)
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Rare complication
 Herpes encephalitis
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Acyclovir may lessen
symptoms
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Measles virus
 Transmitted by respiratory route
 Cold symptoms and fever
 Macular rash with raised spots and
Koplik's spots in oral mucosa
 Rash begins on face and affects the
trunk and extremities
 Prevented by vaccination
 Encephalitis in 1 in 1000 cases
 Subacute sclerosing panencephalitis
in 1 in 1,000,000 cases
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Rubella virus
Macular (not raised)
rash and light fever
 Congenital rubella
syndrome causes
severe fetal damage
(heart, eyes, hearing,
mental)
 Prevented by
vaccination
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Ranked as fifth disease in a
1905 list of skin rashes
 Human parvovirus B19
 Mild flu-like symptoms
 Distinct skin rash
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 Slapped face
 Fades slowly away
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Human herpes virus 6 and 7
Causes a high fever followed by rash lasting for 1-2 days
HHV 6 and 7 can be found in saliva in most adults
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Warts
Small pox
Herpes Simplex (HHV 1)
Chicken pox and shingles
Measles
Rubella
5th Disease
Roseola
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A 10-year-old boy presents with a fever, headaches,
sore throat, and cough. He also has a macular rash
on his trunk, face, and arms. A throat culture was
negative for Streptococcus pyogenes. The boy most
likely has:
a. Streptococcal sore throat.
b. Measles.
c. Rubella.
d. Smallpox.
e. None of the above.
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Dermatomycoses: tinea (ringworm)
 Metabolize keratin
 Infect hair, nails, and outer layer of epidermidis
 Treatment
▪ Topical miconazole
▪ Oral griseofulvin
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Candidiasis
 More often infection mucosal surfaces
 Skin infection when moisture increased
 Local or systemic immunosuppression
 Can become systemic
 Treatment
▪ Topical miconazol
▪ Systemic fluconazol
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Candida albicans (yeast)
Candidiasis may result from suppression of
competing bacteria by antibiotics
 Occurs in skin; mucous membranes of
genitourinary tract and mouth
 Thrush is an infection of mucous
membranes of mouth
 Topical treatment with miconazole or
nystatin
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Scabies
 Sarcoptes scabiei
burrows in the skin
to lay eggs
 Intense local
itching,
superinfections
 Treatment with
topical insecticides
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Pediculus humanus capitis
(head louse)
 P. h. corporis (body louse)
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 Feed on blood
 Lay eggs (nits) on hair
 Treatment with topical
insecticides
 Combing out
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Body louse transmits
typhus
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Small insects that feed on the
blood of mammals and birds
Bite during the night, peak
time before dawn
Red, itchy bites on the skin,
usually in rows, no central red
spot
May become superinfected
Check for bed bugs along the
seams of mattresses
Wash clothes and bedding in
hot, soapy water to kill
bedbugs and their larvae
(from WebMD and cdc.gov)
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Which of the following is responsible for
severe birth defects if contracted during
pregnancy?
a. Measles virus
b. Rubella (correct answer)
c. Varicella-zoster virus
d. Human parvovirus B19
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Bacterial
 Haemophilus influenzae, Neisseria gonorrhoeae,
Chlamydia trachomatis, Pseudomonas
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Viral
 Adenoviruses
 Herpes simplex type 1 (HHV-1)
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Protozoa
 Acanthamoeba
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Conjunctivitis (pink eye)
 Haemophilus influenzae
 Various microbes
 Associated with unsanitary contact lenses
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Neonatal gonorrheal ophthalmia
 Neisseria gonorrhoeae
 Transmitted to newborn's eyes during
passage through the birth canal
 Prevented by treatment newborn's eyes with
antibiotics
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Inclusion conjunctivitis
 Transmitted to newborn's eyes during passage
through the birth canal
 Spread through swimming pool water
 Treated with tetracycline
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Trachoma
 Greatest cause of blindness worldwide (3% of all
causes)
 Infection causes permanent scarring; scars abrade
the cornea leading to blindness
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Chronic follicular
conjunctivitis
2. Inversion of
eyelashes
irritation of cornea
3. Corneal ulcerations,
scarring
4. Vision loss typically
at age 30 – 40
1.
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Herpes simplex virus
1 (HHV-1)
Infects cornea
May cause blindness
Treated with
trifluridine
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Transmitted from water
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Associated with unsanitary contact lenses
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Conjunctivitis
 Bacterial: Haemophilus influenzae, Neisseria
gonorrhoeae, Chlamydia trachomatis,
Pseudomonas aeruginosa
 Viral: Adenoviruses
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Keratitis
 Viral: Herpes simplex type 1 (HHV-1)
 Protozoal: Acanthamoeba
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Using a homemade saline solution for
contact lenses can result in
a. Acanthamoeba keratitis
b. Trachoma
c. Ophthalmia neonatorum
d. Inclusion conjunctivitis
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Major opportunistic pathogens causing skin
lesions are staphylococci and streptococci
causing infections with pus
 Viral infections are often transmitted via aerosol
followed by viremia and skin cell infection with a
generalized exanthem
 Conjunctivitis is the most common eye infection
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