Important Diseases of the Skin and Eyes - Microbiology PDF

Important diseases (1) Skin, Mucosal Membrane and Eyes  Skin Outer layer epidermis, inner layer dermis. The skin is a physical barrier against microorganisms. Moist areas of the skin (such as the armpit) support larger populations of bacteria than dry...

Important diseases (1) Skin, Mucosal Membrane and Eyes  Skin Outer layer epidermis, inner layer dermis. The skin is a physical barrier against microorganisms. Moist areas of the skin (such as the armpit) support larger populations of bacteria than dry areas (such as the scalp). Human skin produces antibiotics called defensins.  STRUCTURE AND FUNCTION OF THE SKIN The outer portion of the skin (epidermis) contains keratin, a waterproof coating- prevent water from entering body. The inner portion of the skin, the dermis, contains hair follicles and sweat pores that provide passageways for microorganisms. The skin generates antimicrobial substances. Embedded in the dermis, durable part of the skin, sebaceous glands and sweat glands. Sebaceous glands produce an oily secretion called sebum (consist mainly organic acids and lipid). Maintain acidic skin pH that discourage pathogen growth. Increase sebum secretion in puberty, contribute to the development of acne.  STRUCTURE AND FUNCTION OF THE SKIN – cont. Sweat glands – watery secretion through pores in the skin. In armpits and groin, these glands secrete organic substances in the sweat that lower the skin pH, again inhibiting the growth of pathogens. High salt content in sweat also inhibits many microorganisms.  Mucous membrane Lining of tissues and organs that open to the exterior of body, especially those of respiratory tract, digestive and urogenital system. Thin epidermal layer and a deeper connective tissue layer. Epithelial cells secrete mucus by goblet cell– preventing drying and cracking of mucus membrane. Mucus trap pathogen.  Eyes External protective structures- eyelids, eyelashes, conjunctiva (a mucuos membrane covering the inner surface of each eyelids and the anterior region of each eye), cornea, lacrimal gland (secrete lacrimal fluid (tears)) Tears contain lysozyme – enzyme that break down bacterial cell wall. No normal microflora in eyes.  NORMAL MICROBIOTA OF THE SKIN Microorganisms that live on skin are resistant to desiccation and high concentrations of salt. Gram-positive cocci predominate on the skin. Staphylococcus (salt tolerant), Micrococcus and coryneform bacteria (eg: Corynebacterium and Proprionibacterium acnes) The normal skin microbiota are not completely removed by washing. Members of the genus Propionibacterium metabolize oil from the oil glands and colonize hair follicles. Malassezia furfur yeast grows on oily secretions and may be the cause of dandruff.  MICROBIAL DISEASES OF THE SKIN 1. Localized infections (sties, pimples, and carbuncles) result from S. aureus entering hair follicle - foliculitis - producing pus, can goes into blood and antibiotic cannot reach. - Removed. Furuncle — Staphylococcus aureus - Easily spread: carrier with no symptom. 2. Scalded skin syndrome - Toxemia occurs when toxins enter the bloodstream. - S. aureus – 2 different exotoxin, both called exfoliatins toxin The patient a few hours - Often baby than adult. after the diagnosis of Reddened area begin at staphylococcal scalded skin syndrome, when mouth spread within 24-48 hrs. 90% of the total body - High fever-- bacteremia, area was blistered. septicemia and death within 36 hrs. 3. Erysipelas (reddish patches) also called St. Anthony fire. Streptococci produce toxic byproducts (Group A beta hemolytic toxin) and enzyme hyaluronidase. 4. Impetigo, a highly contagious skin infections caused by Staphylococci, Streptococci, or both together. -Most in children- Easily transmitted- day care center. Why adults are not susceptible is unknown. Treatment: penicillin. 5. Scarlet fever (sometime called scarlatina)- Streptococcus pyogenes –produce erytrogenic toxin (red producing), scarlet fever rash. Three different erythrogenic toxins have been identified. A person can develop scarlet fever once from each toxin – streptococcal pyrogenic exotoxins. Bright red rash on body, together with fever and sore throat Patient who already has antibodies, will get sore throat without scarlet fever rash. They can transmit this fever to others. Treatment penicillin, resistant organisms. Scarlet fever is contagious at first, but after 24 hours of antibiotics, it can no longer be spread 6. Tetanus Vaccine-preventable disease. Does not spread from person to person. Infection from bacteria through skin. Jaw cramping, muscle spasms usually in stomach, painful muscle stiffness all over the body, trouble swallowing, headache, fever and sweating, changes in blood pressure and a fast heart rate. Treatment: antibiotics. Vaccination: DTaP (infant), 3 doses for pregnant women.  Viral Diseases of the Skin 1. Warts Papillomaviruses- human papillomavirus (HPV) cause skin cells to proliferate and produce a benign growth called a wart or papilloma. Warts are spread by direct contact. Can be distinguished by immunological tests and microscopic examination. Treatment: excision of infected tissue and chemical agents. 2. Rubella/German measles, togavirus: Rubella virus - skin rash, women only. Virus spread in blood and tissue 16-21 days before rash appear. Infected person suffer from joint pain (virus attack to joint membranes). Congenital rubella syndrome- If infected fetus 8 mth pregnancy, organ defect. Damage from congenital rubella syndrome includes stillbirth, deafness, eye cataracts, heart defects, and mental retarded. Transmission by nasal secretion. Very dangerous to children 5-14 yrs. Attenuated vaccine – before pregnancy to eliminate transplacenta (MMR)- measles, mumps, and rubella  Rubella In children, rubella is often a mild disease, a rash that begins on their face and then spreads from their head to their toes. It can be a little itchy Unlike measles, children with rubella often don't have a fever and the rash is fainter than the rash of measles.  Poxviruses 3) Smallpox (variola) Smallpox virus (orthopox virus) – Variola major has 20% mortality – Variola minor has ~12 days incubation, its infect phagocytic cell and blood cells, spread to skin cell and cause pus-filled vesicles, cause fever, backache and headaches, scab appear first in the mouth and throat, then rapidly to the face, forearms, hands, and lower back. Progression of smallpox: pus-filled vesicles and scabs on face, body parts, throat and lower back. 4. Measles/ rubeola- fever with rash - rubeola virus. Invades to lymphatic tissue and blood. Virus enter the body through nose, mouth or conjunctiva. Symptom appear in 9-11 days in children and 21 days in adult. Koplik’s spot, whitish spot on upper lips and cheek mucosa, followed by fever, conjunctivitis and cough > rash. very infectious- transmitted by the respiratory route, nasal secretion MMR vaccine - long-term immunity If the virus invade lungs, kidneys or brain, the common childhood disease often is fatal. Measles- Rubeola with Koplik’s spot Children have measles before they were 10 years old. 5. Chickenpox (Varicella) and Shingles (Herpes Zoster) herpesvirus, one virus two diseases. Chickenpox (varicella, children) and shingles (zoster, adult and immunocompromised). Is localized in skin cells, causing a vesicular rash. Chickenpox is a disease of childhood - 90% of cases occur in children aged 14 years and younger After chickenpox, the virus can remain latent in nerve cells and subsequently activate as shingles. Shingles (herpes zoster) is characterized by a vesicular rash along the affected cutaneous sensory nerves. When virus release –fever and malaise. After 14-16 days skin lesion at nerve end contain liquid. Lesion at portal of entry at nerve end contain fluid. Painful and itchy. Lesion also portal of entry for secondary infection for Stap. aureus. Can cause death – virus invade and damage cells that line small blood vessel and lymphatic– blood clot- hemorrhage. Death due to most blood vessel damaged in the lung and accumulation of erythrocytes and leukocytes in the alveoli. Very easilyy infected airborne.- highly contagious. Treated with acyclovir or famciclovir in immunocompromised patients. Treatment: live attenuated vaccine Chicken pox Shingles Fungal Diseases of the Skin and Nails 1. Cutaneous Mycoses Fungi that colonize the outer layer of the epidermis cause dermatomycoses called ringworm, or tinea. Trichophyton: Infects hair, skin, and nails Epidermophyton: Infects skin and nails Microsporum: Infects hair and skin – Tinea pedis -athlete’s foot-highly contagious – Tinea corporis – body ringworm (infection in arms and legs) – Tinea cruris – groin (in skin folds in pubic region) These fungi grow on keratin-containing epidermis, such as hair, skin, and nails. Ringworm and athlete’s foot are usually treated with topical antifungal chemicals. Diagnosis is based on the microscopic examination of skin scrapings or fungal culture Treatment – Remove dead epithelial tissues and applying topical antifungal ointment.  Opportunistic fungal Infection 1. Candidiasis Candida albicans causes infections of mucous membranes and is a common cause of thrush (in oral mucosa) and vaginitis. C. albicans is an opportunistic pathogen that may proliferate when the normal bacterial microbiota are suppressed. Topical treatment with antifungal drug  Superficial candidiasis appear as thrush, milky patches of inflammation on oral mucous membrane especially in infants, diabetic and those receiving prolonged antibiotic therapy. Candidiasis Candida infections of the nail are very difficult to eradicate. 2) Aspergillosis: Aspergillus fumigatus. – Enter through wound, burns, cornea, ear (ulcerate eardrum) – In immunosuppressed patients can cause pneumonia. – Treatment: antifungal. – Prevention mainly depend host defense.  BACTERIAL DISEASES OF THE EYE 1) Conjunctivitis (pinkeye) Inflammation cause by Stapylococcus aureus, Streptococcus pneumoniae, Neisseria gonorrhoease, Pseudomonas sp. and Haemophilus influenzae. Contagious especially among children. Treatment: sulfonamide ointment. 2) Neonatal gonorrheal ophthalamia (Ophthalamia neonatorum) – is caused by the transmission of Neisseria gonorrhoeae and Chlamydia trachomatis. from an infected mother to an infant during its passage through the birth canal cesarean. – Infection can cause keratitis, an inflammation of cornea, cornea destruction and blindness. All newborn infants are treated with an antibiotic to prevent Neisseria and Chlamydia infection. Treatment: Penicillin/ tetracyclin. Ophthalamia neonatorum 3) Trachoma – Chlamydia trachomatis infection >> swollen conjunctiva – Leading cause of blindness worldwide – Infection causes permanent scarring of eyelids; scars abrade the cornea leading to blindness – scar tissue forms on the cornea. Swollen conjuctiva. Transmission: direct contact, formite, insect vector and during birth Penicillin or Tetracyclin (resistant). Chronic inflammation of the eyelid  Viral Disease of the Eye 1) Epidemic Keratoconjunctivitis (EKC)/ shipyard eye - Cause by adenovirus - Often infect workers from dust particles in the environment. - After 8-10d infection, conjunctiva become inflamed, and eyelid edema, pain, tearing, and sensitive to light. 2) Acute hemorrhagic conjunctivitis (AKC) - Cause by ENTEROVIRUS - Disease cause chiefly in warm, humid climate, crowd and poor hygiene. - Severe eye pain, abnormal sensitivity to light, blurred vision, hemorrhage under conjunctival membranes.  Protozoan Disease of the Eye Acanthamoeba keratitis Protozoan –active (trophozoite) –dormant (cystic) Transmitted from water can cause a serious form of keratitis. Associated with unsanitary contact lenses Common in swimmers  CLINICAL FEATURES Blurred vision and disproportionate pain Patchy anterior stromal infilterates Perineural infilterates (radial keratoneuritis) Infilterates coalesce –ring abcess, ulceration and hypopyon White satellite lesions