Diseases of the Skin

1. Diseases of the Skin

2. Skin • Healthy, intact skin keeps microbes out of the body • Sebum, sweat effect bacteria • Skin cells are keratinized • Dead skin cells are a food source for some bacteria • Microbes like it warm and moist

3. Normal skin bacteria • Staphylococcus G+ • Micrococcus G+ • Propionibacterium G+

4. Bacterial Skin Infections

5. Acne • Propionibacterium acnes (primarily) • Many different types • Anaerobic • Uses sebum as food source • Affects 85% of teens • Many causes: hormones, stress, sweat, genetics • Not transmissible

6. Impetigo Staphylococcus aureus (children) Streptococcus pyogenes (adults) • Thin walled vesicles rupture and crust • Always carry risk of infection in the blood or below epidermis

7. Scalded Skin Syndrome • Staphylococcus aureus • Produces an endotoxin that causes the skin to peel off • Frequently a complication of Staphylococcus infection

8. Toxic Shock Syndrome • Staphylococcus aureus • “Sunburn” rash • Toxin causes capillaries to become permeable, causing a life threatening drop in blood pressure • Originally liked to highly absorbent tampons in the 1980’s

9. Nectotizing Fascitiis • Streptococcus aureus • When a bacterial infection spreads deeper into the skin. • Mortality is 40% • Hyperbaric chamber, surgical removal

10. Dermatitis • Pseudomonas • Found in soil, water • Rash associated with swimming pools, hot tubs, saunas • Nosocomial • Also causes Otitis media

11. Viral Skin Infections

12. Chicken pox • Varicella virus • Highly contagious • Mild childhood disease, 95% of population has been exposed,100 deaths per year • Spread through the respiratory droplet • Vaccine since 1995 (live, attenuated)

13. Shingles • Another manifestation of chicken pox • Virus is latent in the dorsal root ganglion • Reactivated by stress, low immune system capability • Virus moves along peripheral nerves (unilateral) where it causes blister rash • Communicable – can cause chicken pox in persons that have not had the disease

14. Smallpox • Variola virus • 80% of the population had disease during the middle ages • Transmitted by respiratory droplet • First human disease to be eradicated

15. Reyes Syndrome • Occasional, severe complication of a viral infection • A few days after original infection – vomiting, brain dysfunction, coma, death • Associated with aspirin

16. Cold sores • Herpes simplex virus, type 1 (HSV-1) • Provocative stimuli include fever, UV radiation, stress or mechanical injury • Prodromal stage • The virus is reactivated and migrates to the surface where it causes lesions • Spread by direct contact, droplet transmission

17. Warts • Human papillomavirus • Plantar warts – painful, deep, feet • Common/seed warts – painless, flat, fingers • Flat warts – smooth, develop everywhere • Genital warts – common STD • Wart is not contagious but the virus can be passed to another individual

18. Rubeola (measles virus) Big red disease, 7- day measles • Transmitted by respiratory droplet • Macular rash • Incubation is 2-3 weeks so subject is infectious before the rash is visible • Lesions in the mouth called Koplik’s Spots – red spots with white centers

19. Rubella 3-day, German Measles, Little red measles • Milder measles disease • Humans are the only reservoir • Causes severe birth defects if infected in first 3 months • MMR vaccine

20. Fungal Skin Infections

21. Tinea • Tinea capsis, ringworm • Tinea cruris, jock itch • Tinea pedis, athlete’s foot • Tinea unguinum, nail fungus • Tinea versicolor, a skin rash

22. Candida albicans • Candidiasis or thrush • Vaginal infection • Found anywhere there is damp skin, normally suppressed by local flora (bacteria)

23. Parasites of the Skin

24. Eyebrow mite • Dermodex follicularum • Lives in the eyebrows and eyelashes

25. Head lice • Insect • Predominantly found in Anglo hair • Very contagious, direct or indirect

26. Scabies • Insect • Burrow into the skin and cause intense itching • Very contagious, direct or indirect

28. Diseases of the Nervous System

29. Nervous System Structure • Central Nervous system • Brain • Spinal cord • Peripheral Nervous system • Nerves

30. Diseases of the eye • Conjunctivitis • Inflammation of the conjunctiva or Pinkeye • Haemophilus influenzae, Adenovirus • Contact lenses • Gonorrheal ophthalmia • Neisseria gonorrhoeae • Silver nitrate, antibiotics • Trachoma • Chlamydia trachomatis • Can lead to permanent scarring, blindness

31. Bacterial Nervous Disease

32. Meningitis • Can be caused by virus (most common), fungus, protozoa, bacteria (most deadly) • Microbe enters through lungs

33. Meningitis • Normal throat bacterial inhabitants • Haemophilus influenzae • Also causes pneumonia, otitis media, epiglottitis • Hib vaccine • Neisseria meningitidis • Meningitis vaccine for military, college populations • Streptococcus pneumoniae • Leading cause of bacterial meningitis • New vaccine also decreases the amount of otitis media

34. Tetanus • Clostridium tetani • Obligate anaerobe, endospore forming, G+ • Produces tetanospasmin (neurotoxin) blocks the relaxation pathway of muscles • Jaw (lockjaw), back muscles, respiratory muscles • Neonatal Tetanus • Most often the result of infected umbilical stump where the site has been covered with mud.

35. Botulism • Obligate anaerobe, endospore forming, G+ • Neurotoxin produced by Clostridium botulinum blocks release of acetylcholine • Occurs most often in home-canned foods • Also called the ‘sausage disease’ • Infant Botulism or Floppy Baby Syndrome • Often transmitted by contaminated honey

36. Viral Nervous Disease

37. Poliomyelitis • Seen in areas with poor sanitary conditions • Caused by the polio virus, transmitted by ingestion of contaminated water • Multiplies in throat, tonsils, viremia • Enters the CNS, affects the motor nerve cells where it replicates and kills the nerves, causing paralysis • Causes paralysis of the motor nerves less than 1% of the cases

38. Timeline • 1908 virus discovered • 1938 March of dimes • 1955 Salk IPV clinical trials, 90% effective • Killed virus • 1957 Sabin OPV, tested abroad • Attenuated virus • Licensed in 1962 and became preferred vaccine as it has higher effectiveness • Virus can back-mutate and spread the disease • 1970 Return to Salk using Salk vaccine • 1978 New, improved vaccine

39. Rabies • A specific type of encephalitis • uninique bullet shaped virus • Almost always fatal • Uniquely long incubation period • Localizes in muscle, connective tissues • Travels slowly along peripheral nerves to CNS • 90% cases caused by skunk, raccoon, bat, fox

40. Vaccination after a bite is determined by presence of rabies in the area • A series of antirabies vaccine + immune globulin antibodies • 5 to 6 injections over 28 days • Pre-exposure vaccine available

41. Encephalitis • Arbovirus • Chills, headache, fever, mental confusion, coma, death can occur • Eastern Equine Encephalitis • Western Equine Encephalitis • St. Louis encephalitis • West Nile virus

43. Circulatory & Lymph Diseases

44. Circulatory System • Blood • Formed elements, plasma • Vessels, capillaries and heart • Lymph system

45. Hemolysis • β-hemolysis on blood agar is a clear window • α-hemolysis on blood agar is green • Hemolysis – bacteria use the RBC’s for iron • Transferrins bind extra iron in the bloodstream • Staphalycoccus aureus

46. Terminology • Septicemia • Lymphangitits • G+ sepsis • G- sepsis

47. Bacterial Circulatory Disease

48. Gangrene • Clostridium perfringes – anaerobic, produces toxins • Blood supply to tissue is interrupted causing ischemia (anaerobic wound condition). • Leads to tissue death or necrosis • Hyperbaric chamber, amputation

49. Rheumatic Fever • Streptococcus pyogenes • Causes arthritis-like joint inflammation, possible heart valve damage

50. Rocky Mountain Spotted Fever • Rickettsia rickettsi • Passed by tick vector • Characteristic rash on body, soles of feet and hands • Prevalent in Southeastern and Southern USA, not in Rocky Mountains