Download
lecture 13 microbial diseases of the skin and eyes edith porter m d n.
Skip this Video
Loading SlideShow in 5 Seconds..
MICR 201 Microbiology for Health Related Sciences PowerPoint Presentation
Download Presentation
MICR 201 Microbiology for Health Related Sciences

MICR 201 Microbiology for Health Related Sciences

269 Vues Download Presentation
Télécharger la présentation

MICR 201 Microbiology for Health Related Sciences

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

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

  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 microbiotaof 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 • Gram+cocci 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 Ritter’s disease • Phage encoded toxin (SSST) • exfoliation • Mostly in children < 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 <1% 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 human…yet!

  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, Reye’s 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. 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

  22. 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

  23. 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

  24. Fifth disease (Erythemainfectiosum) • 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

  25. 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

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

  27. 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.

  28. Cutaneousmycoses: 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

  29. Ringworm and athlete’s foot

  30. 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

  31. Oral candidiasis

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

  33. Superinfectedscabies

  34. 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

  35. 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)

  36. 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

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

  38. 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

  39. 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

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

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

  42. Acanthamoebakeratitis • Transmitted from water • Associated with unsanitary contact lenses

  43. 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

  44. Check your understanding • Using a homemade saline solution for contact lenses can result in • a. Acanthamoebakeratitis • b. Trachoma • c. Ophthalmianeonatorum • d. Inclusion conjunctivitis

  45. 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