Microbial Diseases of the Skin, Eye, and Nervous System PDF

Microbial Diseases of the Skin, Eye, and Nervous System Summary: 1. What are pathology, infection, and disease? 2. What are Koch’s postulates? 3. How are infectious diseases classified? 4. What is the structure and microbiota of the skin? 5. What are some characteristics of microbial skin...

Microbial Diseases of the Skin, Eye, and Nervous System Summary: 1. What are pathology, infection, and disease? 2. What are Koch’s postulates? 3. How are infectious diseases classified? 4. What is the structure and microbiota of the skin? 5. What are some characteristics of microbial skin diseases? 6. What are bacterial skin diseases? 7. What are viral skin diseases? 8. What are fungal skin and nail diseases? 9. What are diseases caused by insects? 10. What are eye diseases? 1. What are pathology, infection, and disease? Pathology: Study of disease Infection: Invasion of the body by pathogens Disease: When the body is in an abnormal state of not performing normal functions 2. What are Koch’s postulates? Koch’s postulates: Used to prove that a specific pathogen causes a specific disease ○ 1. The same pathogen must be present in every case of the disease ○ 2. The pathogen must be isolated from the diseased host and grown in a pure culture ○ 3. The pathogen from the culture must cause the disease when inoculated into a healthy lab animal ○ 4. The pathogen must be isolated from the inoculated animal and must be the original species 3. How are infectious diseases classified? Symptoms: Changes in body function that are felt by a patient because of disease ○ Examples: Fatigue, nausea Signs: Changes in the body that can be measured or observed because of disease ○ Examples: Fever, white blood cell count Syndrome: A specific group of signs and symptoms that accompany a disease Communicable disease: A disease that is spread from one host to another Contagious disease: Communicable diseases that are easily and rapidly spread Noncommunicable disease: A disease not spread from one host to another 4. What is the structure and microbiota of the skin? Epidermis: Thin, outer portion of the skin; composed of layers of epithelial cells Keratin: Waterproofing protein coating outer layer of the epidermis. Also found in hair and nails. Dermis: Inner, thick portion of skin; composed mainly of connective tissue Normal microbiota of the skin: ○ Resistant to drying and high salt concentration ○ Large numbers of gram-positive cocci, some yeast Staphylococci  ○ Areas with moisture have higher populations ○ Either colonize hair follicles (folliculitis) or skin surface 5. What are some characteristics of microbial skin diseases? Skin abnormality Definition Vesicles Small fluid-filled lesion Bullae Vesicles larger than 1 cm in diameter Macules Flat, reddened lesions Papules Raised lesions Pustules Raised lesions with pus Exanthem Skin rash arising from a disease 6. What are bacterial skin diseases? List of bacterial groups associated with skin diseases: ○ 1. Staphylococci ○ 2. Streptococci ○ 3. Pseudomonas aeruginosa ○ 4. Mycobacterium ulcerans ○ 5. Propionibacterium acnes 1. Staphylococcal Skin Diseases: ○ Gram-positive cocci in clusters Staphylococcus epidermidis Staphylococcus aureus ○ Staphylococcus epidermidis: 90% of normal skin microbiota, usually harmless, but can turn opportunistic Causes hospital-acquired infection, produces biofilm on catheters ○ Staphylococcus aureus: Carried in the nasal passage of 20% of the population May produce damaging toxins and cause sepsis MRSA (Methicillin-resistant Staphylococcus aureus): Antibiotic resistant Transmission: Spread by direct contact with an infected wound or contaminated hands and surfaces, especially in healthcare settings Additional info: Small molecules produced by Staphylococcus epidermidis disrupt the formation of biofilms by Staphylococcus aureus  Silly Frogs Can't Ignore Silly Turtles Common skin conditions of Staphylococcus aureus Skin condition Definition Folliculitis Infections of the hair follicles Sty Folliculitis of an eyelash Furuncle (boil) A type of abscess; localized region of pus surrounded by inflamed tissue Carbuncle Damage and inflammation of deep tissue from a spreading furuncle. Most severe stage of a furuncle. Impetigo Crusting (nonbullous/non blistering) sores, spread by autoinoculation Scalded skin syndrome Bullous (blistering) impetigo Pemphigus neonatorum: impetigo of the newborn Think of a really bad sunburn Toxic shock syndrome (TSS) Fever, vomiting, shock and organ failure Can also be caused by other microbes, but it’s less common  2. Streptococcal Skin Diseases: ○ Gram-positive cocci in chains ○ Streptococci differentiated into groups A through T based on antigenic cell wall carbohydrates Group A streptococci (GAS) Streptococcus pyogenes ○ Group A streptococci (GAS) Produce virulence factors: M proteins: external to the cell wall; allow adherence and immune system avoidance Examples: Strep throat, cellulitis, impetigo Streptococcus pyogenes is the most prominent member of this group Streptococcus pyogenes Skin Diseases Disease Definition Erysipelas S. pyogenes infects the dermal layer of the skin Causes local tissue destruction and sepsis Cellulitis Deep infection of the skin Caused by skin breaks Treated with antibiotics and skin grafts Necrotizing fasciitis Flesh-eating disease S. pyogenes is the most common cause Exotoxin A produced by S. pyogenes acts as a potent toxin Very rare, may be fatal 3. Pseudomonas aeruginosa Skin Diseases: ○ Pseudomonas aeruginosa: Gram-negative, aerobic rod Produces exo- and endotoxins; grows in biofilms Opportunistic in burn patients Resistant to many antibiotics  Causes Pseudomonas dermatitis: Transmission: Acquired in swimming pools Symptoms/Signs: Self-limiting rash; Will resolve on its own Also causes Otitis externa/ “Swimmer’s ear”: Transmission: Acquired in swimming pools 4. Mycobacterium ulcerans Skin Diseases: ○ Mycobacterium ulcerans: Gram-positive Causes Buruli Ulcer Cause: Mycobacterium ulcerans produces the toxin mycolactone Transmission: Enters via a break in the skin or insect bite Symptoms/Signs: Causes deep, damaging ulcers that may require amputation Additional info: Primarily found in western and central Africa Different from necrotizing fasciitis: ○ Different bacteria cause Buruli Ulcer  ○ Different signs/symptoms, Buruli Ulcers are deeper infections 5. Propionibacterium acnes Skin Diseases: ○ Propionibacterium acnes: Anaerobic microbe Causes Inflammatory (moderate) acne Cause: Skin cells shed in the hair follicles and combine with sebum. ○ Propionibacterium acnes digests sebum and fatty acids producing an inflammatory response. ○ Causes blockages Treatment: Treated with antibiotics and benzoyl peroxide Additional info: There’s also Comedonal (mild) acne and Nodular cystic (severe) acne ○ Comedonal acne is easily treated with topical formations ○ Nodular cystic acne is inflamed lesions with pus deep in the skin 7. What are viral skin diseases? Many are transmitted via respiratory routes and are systemic Many cause problems in children and developing fetuses List of skin diseases: ○ 1. Warts ○ 2. Smallpox ○ 3. Chickenpox ○ 4. Shingles ○ 5. Herpes Simplex ○ 6. Measles/Rubella 1. Warts: ○ Cause: Excess amounts of keratin in the epidermis. Caused by papillomavirus ○ Transmission: Via contact Cut in the skin Close skin-to-skin contact ○ Symptoms/Signs: Papillomas (Small skin growths) ○ Treatment: Cryotherapy, electrodesiccation, or salicylic acid ○ Additional info: More than 50 types, some cause skin and cervical cancers  2. Smallpox (Variola): ○ Cause: Orthropoxvirus ○ Transmission: Respiratory route, moves into the bloodstream, and infects the skin ○ Symptoms/Signs: Flu-like symptoms, rashes, small bumps ○ Treatment: Completely eradicated from the human population by vaccination ○ Additional info: There are two forms of the disease: Variola major has 20-60% mortality rate Variola minor has