Microbial Diseases of the Skin

Vocab and Diseases

Vesicle

small, fluid-filled lesion

Bulla

large, fluid-filled lesion

Macule

flat, lesion

Papules

rasied lesion no pus

Pustule

rasied lesion with pus

Exanthem

skin rash arising from another focus of the infection

Eneanthem

mucous membrane rash arising from another focus of the infection (inflammation red or purple)

Acne: Etiological agent

Cutibacteria acnes

Acne: Type of agent

Gram positive bacteria, rod, anaerobic

Acne: Reservoir

humans

Acne: Transmission

Normal microbiota

Acne: Characteristic signs/symptoms

Infects sebum channels near hair follicles.

Inflammatory respose casues pimples

Acne: Treatment

topical/oral antibiotics or chemicals (salicylic acid, retinoids, benzoyl peroxide), visible blue light

Acne: Prevention

hygiene, avoid touching the face, non-comedogenic skincare products.

Acne: Special Notes

• Comedonal (mild), Inflammatory (Moderate) or​

• Severe (nodular cystic)​

  • Bacterial infections + Hormonal Contributions + Genetics​

Staph and Strep Skin Infections: Bacteria Types

Staphylococcus aureus

• Gram-positive cocci - clusters, catalase +, coagulase-positive bacteria​

• 30% of adults are natural carriers​

• 2-5% adults are MRSA carriers​

Staph and Strep Skin Infections: Bacteria Types

• Streptococcus spp.​

  • Gram positive cocci – chains bacteria, catalase -​

  • Many different types of strep can cause skin infections.​

Staph and Strep Skin Infections: Reservoir

animals

Staph and Strep Skin Infections: Transmission

direct contact-broken skin

Staph and Strep Skin Infections: Sign/symptoms

abscess, boil/furuncle, sty, folliculitis, carbuncle, impetigo, invasive skin, systemic infections​

Staph and Strep Skin Infections: Treatment

Antibiotics (resistance is a problem)

Staph and Strep Skin Infections: Prevention

Good Hygiene/limit exposure

Severe Staph Infection

• Scalded skin syndrome​

  • Staph aureus infection​

    • Exfoliative toxin​

    • Secondary infections are common

Severe Strep Infections

Erysiplelas​

• Subcutaneous Strep infection​

• Inflammation,​

• Can Spread in tissue​

Severe Staph/Strep Infections

• Nectrotizing fasciitis​

  • “Flesh Eating Bacteria”​

  • Infection of connective tissue​

  • Fast​

  • Can be caused by Strep. pyogenes OR Staph. aureus

Gas Gangrene: Etiological Agent

Clostridium perfringens

Gas Gangrene: Type of Agent

gram-postive, endospore-forming anaerobic rod

Gas Gangrene: Reservoir

Soil

Gas Gangrene: Transmission

soil to necrotic tissue/deep wound/anaerobic wounds

• Associated with improper “backyard” abortions.​

Gas Gangrene: Signs/Symptoms

Major swelling of tissue and necrotic tissue

• Can lead to sepsis.​

• Ischemia: Loss of blood supply ​

• Necrosis: Death of tissue​

  • Gangrene: Death of soft tissue

Gas Gangrene: Treatment

surgical removal of necrotic tissue and/or use of hyperbaric chamber

Gas Gangrene: Prevention

proper wound care

Pseudomonas dermatitis: Etiolocial agent

Pseudomonas aeruginosa

Pseudomonas dermatitis: type of agent

gram-negative bacteria, aerobic rod

Pseudomonas dermatitis: reservoir

natural environmental; clinicla

Pseudomonas dermatitis: Transmission

break/damage skin

Pseudomonas dermatitis: Characteristic signs/symptoms

pyocyanin produces a blue-green pus

Pseudomonas dermatitis: Treatment

difficult, bacteria is naturally resistant to control methods

Pseudomonas dermatitis: Prevention

avoid breaks/damage skin, wound management of broken/damaged skin

Pseudomonas dermatitis: Special Notes

• Risk Factors:​

  • Post-burn infections​

  • Opportunistic, nosocomial

Anthrax: Casustive agent

bacillus anthracis

Anthrax: Type if agebt

gram positive, endospore-forming, bacilli bacteria

Anthrax: Reservoir

naturally occurring in the soil

Anthrax: Transmission

wound entry, pneumonic -airborne, gastrointestinal – ingestion​

Anthrax: Signs/Symptom

• necrotic skin lesion – black appearance, most common ​

  • Also causes pneumonia, gastrointestinal infection​

Anthrax: Treatment

antibiotics

Anthrax: Prevention

vaccine-only used in military or those at risk

Leprosy (Hansen’s Disease): Etiological agent

Mycobacterium leprae

Leprosy (Hansen’s Disease): Type of agent

acid fast rod bacteria

Leprosy (Hansen’s Disease): Signs/symptoms

• Leptromatous form – disfiguring nodules​

• Affects peripheral body regions (nose, fingers, toes)​

  • Cooler temp

Leprosy (Hansen’s Disease): Treatment

multidrug antibictic

Leprosy (Hansen’s Disease): Prevention

masking around infected

Leprosy (Hansen’s Disease): Special Notes

Untreated can lead to permanent nerve damage and disfiguration

Cat Scratch Fever: Etiological/Caustive agent

Bartonella henselae

Cat Scratch Fever: Type of agent bacteria

gram-negative rod

Cat Scratch Fever: Reservior

felines

Cat Scratch Fever: Transmission

Cat scratches or bites

Cat Scratch Fever: Signs/Symptoms

Small papules at site of inoculation, swollen lymph nodes, high fever, usually self limiting​

Cat Scratch Fever: Treatment

antibiotics

Cat Scratch Fever: Prevention

avoid bites/protective gear if expecting bites

Typhus: Etiological agent

Rickettsia prowazekii

Typhus: Type of agent

Gram-negative intracellular vacteria

Typhus: Reservoir

rodents

Typhus: Transmission

Vector: lice

Transmitted when louse feces are rubbed into bite wound

Typhus: Signs/symptoms

rash starting on trunk and flu like symptoms

Typhus: Treatment

antibiotics (fatal if not treated)

Typhus: Prevention

good hygiene/avoid ventor

Typhus: Special Notes

Outbreaks common in Burundi, Ethiopia, and Rwanda (~12,000 cases/year)

Spotted Fevers (Rocky Mountain spotted fever) [tickborne typhus]: Etiological Agent

Rickettsia rickettsia

Spotted Fevers: Type of agent

gram negative intracellular bacteria

Spotted Fevers: Reservoir

Small mammals

Spotted Fevers: Transmission

vector: fleas, lice, mites, ticks

Spotted Fevers: Sign/Symptoms

• Measles-like rash, except that the rash starts on palms and soles and flu like symptoms​

• Severe: cardiovascular disruption, convulsions, and coma

Spotted Fevers: Treatment

antibiotics

Spotted Fevers: Prevention

vector protection

Lyme Disease: Etiological agent

Borrelia burgdorferi

Lyme Disease: Type of agent

gram-negative spirochete bacteria

Lyme Disease: Reservoir

small rodents

Lyme Disease: Vector Transmission

deer ticks

Lyme Disease: Sign/Symptoms

• First sign/symptom: bull’s-eye rash, “flu like” symptoms​

• Second phase: irregular heartbeat, encephalitis​

• Third phase: arthritis, neurological symptoms

Lyme Disease: Treatment

antibiotics for first/second phase

Lyme Disease: Prevention

avoid ticks/vector controls

Cutaneous Mycoses: Dermatomycoses

• Also known as tineas or ringworm​

• Metabolize keratin​

  • Yeast Infections Candida albicans

Cutaneous Mycoses: Etiological Agents

Different genera of fungi involved in different body locations

Cutaneous Mycoses: Reservoir

environmental, mental

Cutaneous Mycoses: Transmission

direct contact

Cutaneous Mycoses: Signs/Symptoms

skin/nail/hair disruption, inflammation, itching

Cutaneous Mycoses: Treatment

antifungal treatments available

Cutaneous Mycoses: Prevention

Good Hygiene/limit exposure

Subcutaneous Mycoses

More serious than cutaneous mycoses

Candida auris - invasive nosocomial infections

• Blood, wound, ear infections​

  • Multidrug resistant

Sporotrichosis

• “Rose-sorters” disease​

• Most common U.S. disease of this type​

  • Sporothrix schenchii enters puncture wound

Scabies: Etiological agent

Sarcoptes sabiei (mite)

Scabies: type of agent

insect

Scabies: Reservoir

var. by mammalian host

Scabies: Transmission

close contact; fomite (bedding/clothing)

Scabies: Signs/symptoms

burrows in the skin to lay eggs - itching and rash

Scabies: Treatment

topical insecticides

Scabies: Treatment

topical insecticides

Scabies: Prevention

good hygiene

Scabies: Special Notes

• Associated with Secondary Infections; immunocompromised ​