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MICR 201 Microbiology for Health Related Science

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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

7 Bacterial infections of the skin
in burn patients

8 Staphylococcus aureus
Gram+cocci in clusters Catalase + Facultative anaerobe Salt tolerant Coagulase + Leukocidin Exfoliative toxin Protein A (captures antibodies) Golden-yellow colonies 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 Inflammatory acne Nodular cystic acne Gram + rods
Occurs when sebum channels are blocked by shedded cells Inflammatory acne Propionibacterium acnes Gram + rods Anaerobic Skin flora Nodular cystic acne

15 Acne pathogenesis and treatment
Propionibacterium 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)

16 Gangrene Ischemia Necrosis Gangrene Gas gangrene
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

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 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 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 River blindness
Contact lenses (Pseudomonas) River blindness

27 Neonatal eye infections
Infected by the mother during vaginal birth Neonatal gonorrheal ophthalmia by Neisseria gonorrhoeae infection 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. 32

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

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