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MICR 201 Microbiology for Health Related Sciences

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Lecture 13: Microbial diseases of the skin and eyes Edith Porter, M.D. * * Pediculus humanus capitis (head louse) P. h. corporis (body louse) Feed on blood Lay eggs ... – PowerPoint PPT presentation

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Title: MICR 201 Microbiology for Health Related Sciences


1
MICR 201 Microbiology for Health Related Sciences
  • Lecture 13 Microbial diseases of the skin and
    eyes
  • Edith Porter, M.D.

2
Lecture outline
  • Skin
  • 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
  • Anatomy of the eye
  • Bacterial infections of the eyes
  • Viral infections of the eyes
  • Protozoan infections of the eyes

3
Skin
  • Rigid barrier due to keratin
  • Antimicrobial factors
  • Salt
  • Antimicrobial peptides
  • Lysozyme
  • Fatty acids
  • Constant shedding
  • Microbial entrance typically through hair
    follicle and sweat glands

4
Normal microbiota of the skin
  • Gram-positive bacteria
  • Staphylococci
  • Micrococci
  • Corynebacteria
  • Propionibacteria

5
Terminology of skin lesions
  • Exanthem or enanthem skin or mucosa rash
    arising from another focus of infection

6
Microbial diseases of the skin
  • Bacterial
  • Staphylococcus aureus, Streptococcus pyogenes,
    Pseudomonas aeruginosa, Propionibacterium acnes
  • Viral
  • Warts, small pox, chickenpox, shingles, herpes
    simplex, Measles, Rubella, 5th disease, Roseola
  • Fungal
  • Candidiasis, ringworm
  • Parasitic
  • Scabies, lice, bed bugs

7
Staphylococcus aureus
Golden-yellow colonies
  • Gramcocci in clusters
  • Catalase
  • Facultative anaerobe
  • Salt tolerant
  • Coagulase
  • Leukocidin
  • Exfoliative toxin
  • Protein A (captures antibodies)

Antibody (Fc region)
SA
Y
PrA
8
Staphylococcal skin infections
  • Folliculitis
  • Infections of hair follicles
  • Sty
  • Folliculitis of an eyelash
  • Furuncle (boil)
  • Abscess pus surrounded by inflamed tissue
  • Abscess
  • Inflammation of tissue under the skin,
    accumulation of pus, walled off

9
Staphylococcal scalded skin syndrome
  • Also known as Ritters disease
  • Phage encoded toxin (SSST)
  • exfoliation
  • Mostly in children lt 2 years
  • Toxemia

10
Streptococcus pyogenes
  • Gram cocci in pairs and chains
  • 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!

11
Streptococcal skin infections
  • Localized
  • Erysipelas
  • Impetigo
  • Invasive
  • Cellulitis
  • Necrotizing fasciitis (flesh eating disease)

12
Pseudomonas aeruginosa
  • Gram-negative rod
  • Aerobic
  • Oxidase
  • Non-fermenter
  • Pyocyanin produces a blue-green pus
  • Pseudomonas dermatitis
  • Otitis externa
  • Post-burn infections

13
Acne
  • Comedonal acne
  • Occurs when sebum channels are blocked by shedded
    cells
  • Inflammatory acne
  • Propionibacterium acnes
  • Gram rods
  • Anaerobic
  • Skin flora
  • Nodular cystic acne

14
Acne pathogenesisand treatment
  • Pathogenesis
  • P. acnes utilizes glycerol in sebum and produces
    fatty acids (fermentation!)
  • Fatty acids are pro-inflammatory
  • Neutrophils are attracted further contributing to
    inflammation
  • Treatment
  • benzoyl peroxide (antiseptic, dries out acne
    lesions)
  • Antibiotics (erythromycin, clindamycin)
  • Isotretinoin (reduces sebum production,
    TERATOGENIC, 30 of newborns with severe damage)

15
Gangrene
  • Ischemia
  • Loss of blood supply to tissue
  • Necrosis
  • Death of tissue
  • Gangrene
  • Death of soft tissue
  • Gas gangrene
  • Clostridium perfringens, gram-positive,
    endospore-forming anaerobic rod, grows in
    necrotic tissue
  • Treatment includes surgical removal of necrotic
    tissue and/or hyperbaric chamber

http//medicine.ucsd.edu/clinicalimg/Skin-Gangrene
-DIC.jpg
16
Summary of bacterial skin infections
  • Staphylococcus aureus pus, abscess, SSSS
  • Streptococcus pyogenes impetigo, erysipela
  • Pseudomonas aeruginosa Otitis externa
  • Propionibacterium acnes acne
  • Clostridium perfringens gangrene

17
Viral skin infections
  • Skin tumors (warts)
  • Exanthem
  • Aerosol infection ? viremia? skin manifestation

18
Warts
  • 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

19
Poxviruses
  • Smallpox (Variola)
  • Variola major has 20 30 mortality
  • Variola minor has lt1 mortality
  • Vaccination
  • 15/1Mio life threatening side effects
  • 1 2 deaths /1 Mio
  • Emerging disease Monkey pox
  • Orthopox virus
  • Only animal to human, not human to humanyet!

20
Chicken pox and shingles are caused by the same
virus
  • 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,
    Reyes syndrome in conjunction with aspirin
  • Virus may remain latent in dorsal root ganglia
  • Recurrence as Shingles
  • Reactivation of latent HHV-3 releases viruses
    that move along peripheral nerves to skin
  • Routine vaccination

21
(No Transcript)
22
Herpes simplex 1
  • 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)
  • Rare complication
  • Herpes encephalitis
  • Acyclovir may lessen symptoms

23
Measles (rubeola)
  • 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

24
Rubella (German measles)
  • Rubella virus
  • Macular (not raised) rash and light fever
  • Congenital rubella syndrome causes severe fetal
    damage (heart, eyes, hearing, mental)
  • Prevented by vaccination

25
Fifth disease (Erythema infectiosum)
  • Ranked as fifth disease in a 1905 list of skin
    rashes
  • Human parvovirus B19
  • Mild flu-like symptoms
  • Distinct skin rash
  • Slapped face
  • Fades slowly away

26
Roseola
  • 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

27
Summary viral diseases
  • Warts
  • Small pox
  • Herpes Simplex (HHV 1)
  • Chicken pox and shingles
  • Measles
  • Rubella
  • 5th Disease
  • Roseola

28
Case study
  • 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
  • Streptococcal sore throat.
  • Measles.
  • Rubella.
  • Smallpox.
  • None of the above.

29
Cutaneous mycoses fungal skin infections
  • Dermatomycoses tinea (ringworm)
  • Metabolize keratin
  • Infect hair, nails, and outer layer of
    epidermidis
  • Treatment
  • Topical miconazole
  • Oral griseofulvin
  • Candidiasis
  • More often infection mucosal surfaces
  • Skin infection when moisture increased
  • Local or systemic immunosuppression
  • Can become systemic
  • Treatment
  • Topical miconazol
  • Systemic fluconazol

30
Ringworm and athletes foot
31
Candidiasis
  • 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

32
Oral candidiasis
33
Arthropod infections scabies
  • Scabies
  • Sarcoptes scabiei burrows in the skin to lay eggs
  • Intense local itching, superinfections
  • Treatment with topical insecticides

34
Superinfected scabies
35
Arthropod infections pediculosis
  • Pediculus humanus capitis (head louse)
  • P. h. corporis (body louse)
  • Feed on blood
  • Lay eggs (nits) on hair
  • Treatment with topical insecticides
  • Combing out
  • Body louse transmits typhus

36
Bed bugs
  • 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)
37
Check your understanding
  • 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

38
Microbial infections of the eyes
  • Bacterial
  • Haemophilus influenzae, Neisseria gonorrhoeae,
    Chlamydia trachomatis, Pseudomonas
  • Viral
  • Adenoviruses
  • Herpes simplex type 1 (HHV-1)
  • Protozoa
  • Acanthamoeba

39
Bacterial infections of the eyes
  • Conjunctivitis (pink eye)
  • Haemophilus influenzae
  • Various microbes
  • Associated with unsanitary contact lenses
  • Neonatal gonorrheal ophthalmia
  • Neisseria gonorrhoeae
  • Transmitted to newborn's eyes during passage
    through the birth canal
  • Prevented by treatment newborn's eyes with
    antibiotics

40
Chlamydia infection of the eyes
  • Inclusion conjunctivitis
  • Transmitted to newborn's eyes during passage
    through the birth canal
  • Spread through swimming pool water
  • Treated with tetracycline
  • Trachoma
  • Greatest cause of blindness worldwide (3 of all
    causes)
  • Infection causes permanent scarring scars abrade
    the cornea leading to blindness

41
Trachoma
  • Chronic follicular conjunctivitis
  • Inversion of eyelashes irritation of
    cornea
  • Corneal ulcerations, scarring
  • Vision loss typically at age 30 40

42
Herpes keratitis
  • Herpes simplex virus 1 (HHV-1)
  • Infects cornea
  • May cause blindness
  • Treated with trifluridine

43
Acanthamoeba keratitis
  • Transmitted from water
  • Associated with unsanitary contact lenses

44
Summary of eye infections
  • Conjunctivitis
  • Bacterial Haemophilus influenzae, Neisseria
    gonorrhoeae, Chlamydia trachomatis, Pseudomonas
    aeruginosa
  • Viral Adenoviruses
  • Keratitis
  • Viral Herpes simplex type 1 (HHV-1)
  • Protozoal Acanthamoeba

45
Check your understanding
  • Using a homemade saline solution for contact
    lenses can result in
  • a. Acanthamoeba keratitis
  • b. Trachoma
  • c. Ophthalmia neonatorum
  • d. Inclusion conjunctivitis

46
Important to remember
  • 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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