MICR 201 Microbiology for Health Related Sciences

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

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 (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

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. 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

30. Ringworm and athlete’s 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. Superinfectedscabies

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. Acanthamoebakeratitis • 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. Acanthamoebakeratitis • b. Trachoma • c. Ophthalmianeonatorum • 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