MICR 201 Microbiology for Health Related Science

1. MICR 201 Microbiology for Health Related Science Microbiology- a clinical approach by Anthony Strelkauskas et al. 2010 Chapter 26: Infections of the skin and eyes

2. Why is this chapter important? • Skin and eyes are in contact with potentially pathogenic organisms all the time. • Alterations of skin and eyes can represent a psychological burden. • Infections of the eyes can lead to blindness.

3. Map for chapter 26

4. Anatomy of skin • Largest organ in the body. • Barrier between our body and the outside • First line of defense against invading microorganisms • Outer layer (epidermis) comes into direct contact with the environment. • Constant shedding of cells keeps pathogens from successfully attaching to the skin. • Skin gets infected when surface is disrupted. • Exceptions: some worm infections; schistosomiasis, hookworm infection

5. Anatomy of skin • Close access to blood system • Surface penetrated by hairs and glands • Site of infections

6. Skin lesions • Four main types of skin lesions: • Macules • Papules • Vesicles • Pustules

7. Bacterial infections of the skin in burn patients

8. 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

9. 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

10. Staphylococcal scalded skin syndrome (SSSS) • Caused by exotoxin • Exfoliatins • Mostly in children < 2 years • Good prognosis and long lasting immunity

11. 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!

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

13. Pseudomonas aeruginosa • Gram-negative rod • Aerobic • Oxidase + • Non-fermenter • Pyocyanin produces a blue-green pus • Pseudomonas dermatitis • Otitis externa (swimmer’s ear) • Post-burn infections

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

15. Acne pathogenesisand treatment • Pathogenesis • Propionibacteriumacnesutilizes 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)

16. 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 spore forming rod, grows in necrotic tissue • Produces phospholipase, proteinase, hyaluronidase • Produce also hydrogen gas • Treatment includes surgical removal of necrotic tissue and/or hyperbaric chamber • In addition antibiotics such as penicillin and clindamycin http://medicine.ucsd.edu/clinicalimg/Skin-Gangrene-DIC.jpg

17. Summary of bacterial skin infections • Staphylococcus aureus: pus, abscess, SSSS • Streptococcus pyogenes: impetigo, erysipela • Pseudomonas aeruginosa: Otitis externa • Propionibacterium acnes: acne • Clostridium perfringens: gangrene

18. Viral infections of the skin • Exanthem • Aerosol infection  viremia skin manifestation • Skin tumors (warts) • Measles • Rubella • Smallpox (variola) • Chickenpox and shingles • Herpes simplex virus type 1 • Warts

19. Measles • Extremely contagious infection • Caused by single-stranded RNA virus • Transmitted by respiratory route • Cold symptoms and fever • Viremia • Macular rash, raised spots, Koplik's spots in oral mucosa • Rash begins on face, affects trunk and extremities • 15-25% mortality rate in developing countries • Up to 15% of cases of measles have complications - Otis media, sinusitis, pneumonia, sepsis, encephalitis • Prevented by vaccination

20. Rubella (German measles) • Very mild or asymptomatic infection • Low-grade fever, lymphadenopathy, and faint macular rash. • Very serious in pregnant women • Can cause congenital abnormalities in fetus (embryoathy) • Infected individual contagious for 8 days before and 8 days after appearance of rash.

21. Smallpox (Variola) • Infection caused by a DNA poxvirus. • Two forms of smallpox: • Variola major – mortality rate 20% or higher • Variola minor – mortality rate 1% • Vaccinatiom: side effects, 1-2 deaths/million • Smallpox has effectively been eradicated from the entire world; last victim in Somalia in 1977 • Only reservoir is humans; should be no more cases • Stocks of smallpox virus mean further infections are possible • Decreased herd immunity to smallpox increases the possibile potential as bioweapon

22. Smallpox (Variola)

23. Smallpox: Pathogenesis • Dominant feature is the appearance of papulovesicular rash and pustules. • Incubation period is usually 12-14 days. • Can be 4-5 days • Abrupt onset of fever, chills, and muscle aches • Rash appears 3-4 days later. • Papulovesicles most prominent on the head and extremities. • Become pustular over 10-12 days. • Death from smallpox results from: • Overwhelming virus infection • Bacterial superinfection

24. Summary of viral infections • Measles (measles virus, Koplik’s spots, subacute panencephalitis) • Rubella (rubella virus, embryopathic) • Small pox (variola virus, up to 30% mortality) • Chicken pox and shingles (Varizella Zoster virus, latency dorsal root ganglion) • Herpes simplex virus (HSV 1, latency trigenimal ganglion and recurrence) • Warts (Papilloma virus, cancer)

25. Fungal infections of the skin • Candidiasis • Dermaphytosis

26. Infections of the eyes Pink eye HSV1 Contact lenses (Pseudomonas) Riverblindness

27. Neonatal eye infections • Infected by the mother during vaginal birth • Neonatal gonorrheal ophthalmia by Neisseria gonorrhoeaeinfection • Chlamydia trachomatis can also infect the eyes of newborns. • Both infections cause large amounts of pus to form in the eyes. • Causes ulceration and scarring of the cornea if not treated • Common practice to treat eyes of newborn infants with erythromycin.

28. Neonatal gonorrheal ophthalmia

29. Eye infections treatment • Topical eye drops and ointments containing erythromycin or gentamicin are effective against acute bacterial conjunctivitis. • Fluoroquinolones can be used for eye infections caused by Pseudomonas. • Quinolones such as ciprofloxacin useful for all types of eye infection.

30. LOAIASIS • Parasitic worm Loa loa • African rain forest • Transmitted by bite of deer fly • Migrate from tissue to eye • Grow up to an inch and easily seen

31. Chapter 26 key concepts • Skin is an impermeable barrier to almost all pathogens. • A wide variety of bacteria can cause infection of the skin, with necrotizing fasciitis being one of the worst infections. • Bacteria can infect hair follicles, sebaceous glands, and sweat glands. • Viral pathogens also require a portal of entry to infect the skin. • Viral infections that cause lesions on the skin include measles, rubella, smallpox, chickenpox, herpes simplex type 1, and human papillomavirus. • Fungi are always present on the skin but rarely cause infection.

32. Chapter 26 key concepts The most common fungal infection of the skin is candidiasis. Dermatophytosis can be seen as ringworm, athlete’s foot, or jock itch. One of the most common parasitic infections of the skin is leishmaniasis. Eyes are infected through direct exposure to pathogens. A common eye infection and leading cause of blindness is trachoma, which is caused by Chlamydia trachomatis. Parasitic infections of the eye include loaiasis.

33. Final Examination –Wednesday, June 12, 2013 10:45am – 1:15pm Lecture, Chapter End Self Study Questions 100 Multiple Choice Questions: 2 points each x 100 = 200 points ~65%: Chapters 14-26 ~35%: Chapters 1-13 Please bring Scantron and No. 2 pencil

34. CORRECTION – Chapter Question Chapter 22 Infections of the Digestive System 1. The most common source of gastrointestinal infection in the developed world is A. Salmonella B. Shigella C. Escherichia D. Campylobacter E. Staphylococcus aureus Correct answer is D. Campylobacter