Microbial Diseases of Skin & Wounds

Microbial Diseases of Skin and Wounds 

  

  • Skin microbiome and ports of entry 

  1. How does the microbiome protect against infections? 

  • The skin microbiome is composed of harmless microbes present on skin surface. 

  • These harmless microbes compete with potential pathogens for nutrients & space 

  • They produce chemicals that interfere with growth of other microbes. 

  • Persistence: can’t be completely removed through cleansing 

  • Distribution: Typically grow in visit areas of skin 

  • Byproduct: waste products cause body odor 

  1. Why is it very difficult to eliminate the microbiome? 

  • Microbes in skin microbiome typically grow in moist areas of the skin 

  1. How can pathogens enter the body through the skin? 

  • Trauma to any body tissue including cuts, scrapes, surgery, burns, and bites --> allow microbes to infect deeper body tissue 

  • Impetigo, erysipelas, and cellulitis 

  1. Causative agent:  

  • Impetigo: S. Aureus 

  • Erysiplas: streptococcus perplexes [group A streptococcus] 

  • Cellulitis:  S. Pyogenes 

  1. Signs and symptoms 

  • Impetigo: red patches form on face & limbs; paptches develop into pus-filled vesicles that crust 

  • Erysipelas: infection spreads to lymph nodes; reddening on face, arms, or legs 

  • Cellulitis: infection of deeper dermis and subcutaneous fat; appears as red, swollen area that is hot to the touch 

  1. Mode of transmission: transmitted by person-to-person contact via donors; impetigo occurs mostly in children; erysipelas can also occur in elderly 

  • Impetigo diagnosis: presenc of vesicles diagnostic; treatment --> oral and microbials with careful cleaning of infected areas 

  • Erysipelas: treatment: penicllin 

  • Cellulitis: most often occurs in legs of adults with poorly controlled fractures; treatment: cephalexin 

  1. Why is cellulitis a life-threatening condition? 

  • Bacteria can spread to deeper tissue/bloodstream causing sepsis... 

  • Necrotizing fasciitis 

  1. Causative agent: streptococcus pyogenes 

  1. Toxins: Endotoin A and Streptolysin S damage cells& tissues 

  1. Signs and symptoms: 

  1. Redness, intense pain, and swelling at infection site 

  1. Develop fever, nausea, malaise, and possible mental confusion 

  1. Mode of transmission 

  1. S pyogenes interred though breaks in skin 

  1. Treatment 

  1. Removal of affected tissue; broad-spectrum antimicrobials 

  1. Why is it a life-threatening condition? 

  1. About glomerulonephritis can result if infection spreads to kidneys 

  1. Death can also occur. 

  • Pseudomonas infection 

  1. Causative agent: pseudomonas aeruginosa  

  • Gram negative baccilus 

  • Found in soil, decaying matter, moist environments, and numerous hospital surfaces 

  1. Signs and symptoms:  

  • Blood infection causes fever, chills, and shock 

  • blue-green color from bacterial pigment pyocyanin occurs in massive infections 

  1. Treatment 

  • Diagnosis: pyocyanin discoloration indicates massive infection 

  • Treatment: combination of antimicrobials; multidrug resistance common in this organism 

  • NOTE: infections typically don’t occur in healthy individuals 

  1. Mode of transmission 

  • Inhabits water and soil, rarely part of human microbiome 

  • Can infect almost any organ or system once in body 

  1. Why is it particularly dangerous (and common) in burn victims? 

  • Bacteria grows under burn surface 

  • Bacteria kill cells, destroy tissue, trigger shock 

  • IMPORTANT: debridement of burn required for topical antimicrobials to be effective 

  • Spotted fever rickettsiosis 

  1. Causative agent: rickettsia ricketsii 

  • Gram negative intracellular parasite 

  1. How are rickettsias different from other bacteria? 

  • Does not use glucose as a nutrient 

  • Does it secrete any toxins 

  1. Signs and symptoms 

  • non-itchy spotted rash on trunk and appendages 

  • Organ failure can occur in severe cases 

  1. Mode of transmission (vector) 

  • Infected bite of TICK 

  • Location: Appalachian mountains 

  • Seasonal occurrence: summer [may, June, july] 

  • Treatment 

  1. Diagnosis: serological testing 

  1. Treatment: various antimicrobials 

  1. Prevention: use of tick repellants and avoidance of tick-infested areas 

  • Gas gangrene 

  1. Causative agent: C. perfringens 

  • Gram-negative endospore-forming bacilli 

  1. Signs and symptoms 

  • Death of muscle & connective tissue 

  • Blackening of infected muscle & skin 

  • Presence of gas bubbles 

  • Shock, kidney failure, and rapid possible death 

  1. Mode of transmission 

  • Traumatic event must introduce endospores into dead tissue 

  • Mortality rate > 40% 

  1. Treatment 

  • Surgical removal of dead tissue 

  • Administration of antitoxin & antimicrobials 

  • Smallpox 

  1. Causative agent: orthopoxvirus [variola virus] 

  • Only attaches to human cells 

  1. Signs and symptoms 

  • High fever 

  • Severe head & body aches 

  • Skin rash 

  1. How was it possible to eradicate this disease? 

  • Requires immediate vaccination 

  1. Besides smallpox, what other human diseases have been eradicated? 

  • Chickenpox and shingles 

  1. Causative agent: Varicella-zoster virus [VZV] causes both diseases 

  1. Signs and symptoms 

  • Chickenpox 

  • Lesions on back and trunk that spread across body 

  • Virus becomes latent with sensory nerves 

  • Shingles Characteristics 

  • Occurs following reactivation of virus 

  • Lesions localized to skin along infected nerve 

  • Rash pattern: forms in a single strip or band on only ONE side of the body or face 

  • Pain may last after lesions have healed 

  1. Mode of transmission 

  • Chickenpox 

  • Airborne droplets, direct touch, contact with shingles --> mostly children get it 

  • Shingles 

  • Infection spreads from respiratory tract to skin via blood and lymph --> ppl usually over 50 

  • NOTE: You can’t catch shingles from someone else; however, if a person who never had chickenpox touches the fluid from a shingles blister, they can catch chickenpox. 

  1. Treatment 

  • Treatment: relief of symptoms 

  • Prevention: vaccines available for chickenpox and shingles 

  1. What is the relationship between the virus causing chickenpox and the one causing shingles? 

  • Same virus, but two different stages/reactions of the same infection in the body... 

  • Measles [Rubeola] 

  1. Causative agent: Paramyxoviridae Morbillivirus 

  • IMPORTANT: adhesion and fusion proteins help virus avoid immune recognition 

  1. Signs and symptoms 

  • Koplik’s spots: numerous red lesions on head and across body 

  • Complications: Subacute sclerosing panencephalitis [rare but deadly] can develop years after initial infection 

  1. Treatment 

  • Confirmed with serological testing 

  • Treatment:  

  • Vitamin A 

  • Antiboidies against measles virus 

  • ribavirin 

  1. Vaccine: MMR vaccine 

  1. Why is measles making a comeback? 

  • People aren’t getting the vaccine. 

  • Cutaneous fungal infections 

  1. Causative agents 

  • Trichophyton 

  • Microsporum 

  • Epidermophyton floccosum 

  1. What is a dermatophyte? 

  • Specialized molds that feed on keratin, causing common superficial infections of the skin, hair, & nails --> ringworm or tinea 

  1. Athlete’s Foot 

  • Agents: Trichophyton rubrum; T. mentagrophytes var interdigitale; epidermophyton floccosum 

  • Signs: red, raised lesions on and around toes/soles; webbing between toes heavily infected 

  1. Ringworm 

  • Agents: T. rubrum; microsporum gypseum M. canis 

  • Signs: red, raised, ringlike lesions on various skin surfaces 

  1. Mode of transmission 

  • Athlete’s Foot: Human reservoirs in toe webbing; carpeting holding infected skin cells 

  • Ringworm: can spread from other body sites; acquired from contaminated soil or animals 

  1. Treatment 

  • Antifungal medications