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metha 2010 chp18
Microbial Disease of the Skin and Eye
| Question | Answer |
|---|---|
| The skin is | a large - complex organ that protects the body. |
| Epidermis | – layers of dead cells that contain keratin: a waterproofing and protective protein |
| Dermis | – connective tissue that contains the hair follicles - sweat gland ducts - and oil gland ducts that act as passageways for microorganisms to enter the skin and penetrate deeper |
| the Integumentary system | The skin combined with the hair nails and sweat and oil glands comprise the study of which is called dermatology. |
| Perspiration | – provides water and nutrients for some microorganisms - but also contains salt and lysozyme |
| Sebum | – secreted by the oil glands; lipids - proteins - and salt; limits growth of some microorganisms - but encourages growth of others |
| Mucous Membranes | – lining of body cavities; tightly packed epithelial cells attached to a membrane; many of these cells secrete mucous; often acidic; in the eyes are mechanically washed by tears containing lysozyme |
| Diptheroids | (club-shaped bacteria) |
| Micrococci | (including staphylococci – most commonly coagulase-negative S. epidermidis and streptococci) and yeasts |
| Growth patterns | Washing reduces but does not eliminate those in the hair follicles and sweat glands will quickly reproduce= Higher population on areas of the body with more moisture; metabolize secretions and give the body its odor |
| Vesicles | – small - fluid-filled lesions |
| Bullae | – larger vesicles; bubble |
| Macules | – flat - reddened lesions; |
| Maculopapular | – combines macular and popular characteristics |
| Papules | – raised reddened lesions; |
| Pustules | – if filled with pus |
| Bacterial Diseases of the Skin | Acne Impetigo Cellulitis Flesh-eating bacteria Staphylococcal Scalded Skin Syndrome Gas gangrene . Hansen’s Disease |
| Acne severe acne = cystic acne | Cause1) channels for the passage of sebum to the skin surface are blocked; as sebum accumulates - white-heads form; if breaks through the skin - black-heads 2) Propionibacterium acnes produces lipases (and other enzymes) digesting the oils produced by th |
| Acne Treatment | Topical treatments such as BenzaClin; Oral treatments such as antibiotics or the product Accutane - a derivative of vitamin A inhibits sebum formation; 2) No relationship to fats in diet; endocrine factors - emotional stress - pressure on skin by lean |
| Impetigo | – Highly contagious bacterial infection causing the formation of vesicles and pustules and peeling of the skin; caused by Staphylococcus aureus and/or Streptococcus pyogenes; spread by direct and indirect contact; prevention The skin is, a large - comple |
| Staphylococcus aureus | 1) Pathogenesis and Virulence Factors- 2) Culture and/or diagnosis Seen more often in older children and adults Gram Stain – irregular clusters of gram-positive cocci |
| coagulase positive | – almost all pathogenic strains of S. aureus; clots fibrin in plasma and blood and may protect the bacteria from phagocytosis |
| coagulase negative | – 90% of the normal microbiota that do not cause disease unless the skin is broken; S. epidermidis predominant of these |
| exotoxins: | exfoliate toxin A and B production connection with coagulase positive S. aureus |
| Diagnosis usually by observation - | but if antibiotic treatment fails then isolation by culture on blood agar or mannitol salt agar |
| Coagulase lab test using rabbit serum to differentiate | S. aureus and S. epidermidis |
| infected hair follicles: pimples or if an eyelash | –sty - or if with pus a pustule – boil - or if hard - deep inflammation of the tissue – carbuncle |
| Streptococcal Skin Infections | 1) Pathogenesis and Virulence |
| Beta-hemolytic streptococci | - further designated by antigens in the cell wall group A through T - group A beta-hemolytic strep = Streptococcus pyogenes - the most important |
| M protein produced by S. pyogenes | binds plasminogen which causes the bacterium to produce streptokinase. Streptokinase - in turn - changes plasminogen into plasmin. |
| Normally plasmin is produced in the blood to dissolve the plasmin clots | once they have fulfilled their purpose in stopping bleeding. But with a S. pygenes infection - tissue is degraded around the bacterium causing the symptoms of infection. |
| IMPORTANT CONCEPT: Streptokinase: | produced by beta-hemolytic streptococcus is used as an effective and cheap clot-dissolving medication in some cases of myocardial infarction (heart attack) and pulmonary embolism. |
| Cellulitis | – fast-spreading infection of the dermis and subcutaneous tissue usually caused by S. aureus or S. pyogenes but can be caused by other pathogenic bacteria or fungi; pain - swelling - fever - lymphangitis (red streaks leading away from the away - sometime |
| Flesh-eating bacteria: | Necrotizing Fasciitis – invasive S. aureus or S. pyogenes; unique strains that produce exoenzymes and toxins involved; a simple cut in the skin that untreated can spread rapidly into the tissue causing disfigurement and death |
| Staphylococcal Scalded Skin Syndrome | – usually with children under two; very serious; blistering symptoms caused by exfoliate toxins A & B that the bacteria has acquired from certain phage types transduction + lysogeny; mainly spread by asymptomatic carriers; treatment with antibiotics |
| Gas gangrene | – caused by Clostridium perfringens when bacterium enters tissue through a surgical incision - compound fracture - diabetic ulcers - septic abortions – puncture and gunshot wounds - and crushing injuries contaminated by spores from the body or soil; gas |
| Hansen’s Disease | – Leprosy: Mycobacterium leprae; slow growing parasite; need to have direct contact with only a small number of cells (10) to cause infection; tuberculoid leprosy vs. lepromatous leprosy; occurrence in the US |
| Smallpox or Variola | - eradicated b/c an effective vaccine was developed and there are no alternate hosts; US and Russia have samples for research; mortality rate of 70%; vesicles on the face and extremities causing disfigurement |
| Chickenpox or Varicella | a. vaccine at 12 months; before vaccine - 11 -000 hospitalizations - 100 deaths/yr; a live attenuated virus; vesicles b. TORCH - serious fetal damage in the first trimester; c. Reye’s syndrome - use of aspirin in children and teenagers with the flu or ch |
| Shingles | – also called Herpes zoster - Herpes virus HHV-3 or varicella zoster; vesicles similar to chickenpox localized around the waist - or face - upper chest and back; usually limited to one side of the body; can be serious impairing vision or causing paralysi |
| Herpes Simplex | a. Herpes simplex 1 - Herpes virus type 1: Cold Sores; HSV-1 b. Herpes simplex 2 - Herpes virus type 2: genital herpes; HSV-2 Cases have with the reverse from autoinoculation or by oral sexual contactHSV-1 genital infections - HSV-2 oral cavity infect |
| Occupational hazard - dental hygienists: whitlows | (painful inflammation of the finger or toe) near the tip or around the nail; individuals with herpetic whitlows should not work with patients: fluid of the sores is highly infectious and should be avoided |
| Herpetic keratitis | - cornea of the eye infected |
| Life Cycle - Reservoir: human carriers; Transmission: | mainly persons with active lesions; asymptomatic carriers; remains infectious in moist secretions on inanimate objects for a few hours |
| Latent and recurrent attacks | - nonactive virus remains inside the cranial nerves (HSV-1) or spinal nerve trunk (HSV-2); recurrent infection triggered by change: illness - stress - surgery - sunlight - food - citrus - sodium lauryl sulfate in toothpaste - hard candy |
| Virus migrates to the body surface | - prod. a local lesion - often the same site as before; # of attacks 1-12 times/yr. |
| Signs/Symptoms | - Tender - itchy bumps painful eruptive vesicles: intense burning - burst - drain - and scab over |
| HSV-1: | sometimes infect the oral mucosa - tongue - cheeks - and lips; complicated in adolescents w/ sore throat - fever - chills - headache - swollen lymph nodes |
| Prevention important | - extreme care in handling infants; wear gloves; treatment with topical applications of Penciclovir by R - < infection time and < viral shedding; Daily oral dose of Acyclovir (Zovirax) or Valacyclovir HCL (Valtrex) taken for 6 months to 1 yr; antiviral |
| Measles | – red measles or 7-day measles; macularopapular rash; vaccine - MMR given at 12-15 months - but period of vulnerability in infants to 1 year; Koplick’s spots in the oral mucosa (white centers) diagnostic; dangerous in very young and very old - deafness - |
| Rubella or German measles | or 3-day measles; milder than measles; TORCH – congenital rubella syndrome: 35% chance of deafness - eye cataract - heart defects - mental retardation - and death; major epidemic during 1964 - 1965; vaccine – 1969 To determine if an individual has had ru |
| Fifth Disease (Human parvovirus B19) | – common childhood disease presenting as very flushed cheeks: slapped cheek and a lacy macular rash on the trunk - may also have a slight fever - malaise - or cold; resolves in 7 – 10 days; adults may have the rash and joint swelling; fifth on the list o |
| Roseola (HHV-6) | – Affects babies and toddlers from 6 – 24 months; high fever until the fourth day - as it falls a macular rash appears |
| Juvenile and Plantar Warts | – caused by more than 65 types of papillomavirus; treatment by cryotherapy - electrodesiccation - burning - lasers create a virus-laden aerosol; alternatives – aspirin at site; tagament; duct tape |
| Molluscum contagiosum | – caused by a poxvirus that causes bumps that look like smooth - waxy nodules; common in AIDS patients and often on the face |
| Cutaneous mycoses Disease Comple | x - Dermatophytoses: Ringworm/Athlete’s Foot/Jock Itch |
| Cutaneous mycoses Caused by three fungal genera | - Trichophyton - Microsporum - Epidermophyton |
| Cutaneous mycoses Virulence | - breakdown of keratin by keratinase - the primary protein of the epidermal tissues of vertebrates (skin - nails - hair - feathers - horns) |
| Cutaneous mycoses Reservoirs | - other humans - animals - & soil; some species are zoonotic |
| Cutaneous mycoses Symptoms: | Athlete’s foot - scaly patches; Ringworm - scaly - reddish rings on the body; Nail - initially white patches in the nail thickening - distortion |
| Cutaneous mycoses Treatment | - long term (weeks +) with OTC topical ointments; gentle debridement of skin and UV light can help; nails - home remedies: tea tree oil; vicks; monistat “1” - thyme oil; many researchers say 3 months to 1 year |
| Candidiasis - Candida albicans | a. HIV related opportunist - an early indicator of HIV infection - TORCH - nosocomial - direct contact; most common nosocomial FUNGAL infectionb. Ubiquitous; Oral cavity - genitalia - large intestine - and/or skin c. Life Cycle: Reservoir - normal flora |
| Thrush: Symptoms | a white patchy infection affecting the mucous membranes of the oral cavity; common infection in the mouth of newborns & the elderly |
| Candidiasis or yeast infection: Symptoms | discharge - inflammation - painful ulcerations - and itching; Vaginal infections (possibly an STD) - skin infections (diaper rash) |
| Esophageal candidiasis – HIV complication Symptoms | ; painful - bleeding ulcerations - perforations - nausea - and vomiting; |
| Candidal blood infection Symptoms | – an opportunist - causing more deaths than any other fungal infection |
| Intestinal yeast Symptoms | – long term antibiotic use and high sugar diet; problems with mental clarity |
| Low pH and normal vaginal anaerobes keep Candida in check; | Normal T-cell activity is essential |
| Candidiasis - Candida albicans Treatment | Nystatin (Mycostatin) - skin; amphotericin B - systemic infection; OTC for yeast infection - imidazole or ketoconazole ointment; Diflucan pill |
| Candidiasis - Candida albicans Risk of infection | - infants - pregnancy - hormonal changes - use of birth control or antibiotics - immunodeficiency - surgery - trauma - diabetics |
| Parasitic Infestation of the Skin: | Scabies - Sarcoptes scabiei - a burrowing mite - treated with Kwell; chronic - under-diagnosed giving the phrase the seven year itch |
| Conjunctivitis | – bacterial or viral On the increase b/c of contact lenses - esp. soft lenses- avoid homemade saline solutions |
| Bacterial Diseases of the Eye Neonatal Gonorrheal Ophthalmia | - TORCH via the birth canal; blindness |
| Bacterial Diseases of the Eye Infection caused by Chlamydia trachomatis | 1) Inclusion conjunctivitis - contracted as the baby passes through the birth canal with symptoms appearing 5 to 12 days after birth - most prevalent form of conjunctivitis;2) Trachoma -- the leading cause of preventable blindness; infection of the epithe |
| Viral Disease of the Eye | - Herpetic keratitis |
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