Integument Microbiology Flashcards
Gram + bacteria predominate in (dry/moist) skin
Dry (forearm, legs, etc.)
Gram - bacteria predominate in (dry/moist) skin
Moist (armpit, creases, etc.)
Most organisms are in what layer of skin?
stratum corneum and upper parts of hair follicles
Gram + microbial inhabitants of the skin
- Staph. epidermidis
- S. aureus
- Propionibacterium acnes
- B-hemolytic streptococci (Group A S. pyogenes & Group B S. agalactiae)
- a-hemolytic streptocci (S. viridans & S. penumoniae)
What microbe colonizes normal skin in the nose, perineum, and vulva and commonly found on skin of patients with atopic dermatitis?
S. aureus
What microbes are prevalent in areas with sebaceous glands?
Propionibacterium spp. (P. acnes)
P.acnes has been renamed as
Cutibacterium acnes
What microbes are rare inhabitants of skin and are inhibited by lipids
B-hemolytic streptococci (Group A S. pyogenes & Group B S. agalactiae)
What microbe is a cause of impetigo in kids?
GAS (Group A S. pyogenes)
What microbes are common inhabitants of the mouth but rarely spread to skin?
a-hemolytic streptocci (S. viridans & S. penumoniae)
Gram - microbial inhabitants of the skin
Enterobacter
Klebsiella
E. coli
Microbes that are often found under nails
Fungi
How can keratinocytes act as innate immune players (besides being a physical defense)
- TLRs
- Cytokines/Chemokines (TNF-a, IL-1, IL-6)
- Antimicrobial Peptides (AMPs) (b-defensins, LL37))
immunologic defense mechanism of keratinocytes; example are b-defensins (LL37); will accumulate on the microbe, and if a high enough concentration is reached, will punch holes in membrane and form irregular structure, so makes resistance difficult
Antimicrobial Peptides (AMPs)
How does Staph. epidermidis, a normal skin flora, help “educate” CD8+ T-cells?
- Dendritic cells “sample” S. epidermidis angitens and present to CD8+ T cells
- Keratinocytes respond by enhancing barrier function and limiting pathogen invasion
Atopic Dermatitis is usually caused by an infection of
S. aureus
Why is Atopic Dermatitis more common in developed countries?
Improved sanitation–> dec. skin microflora–> less T-cell “education”–> exaggerated inflammation to infections
Common bacteria that infect skin
Staph. aureus
Strep. pyogenes
Common fungi that infect skin
dermatophytes
candida
Common viruses that infect skin
Childhood viruses
VZV
Molluscum contagiosum
Human Papillomavirus
Toxins produced by Staph. aureus and Strep. pyogenes can cause toxic shock via…
Superantigens (trigger MASSIVE polyclonal expansion of T-cells and a cytokine storm)
Massive polyclonal expansion of T-cells and cytokine storm is also known as
Mitogen
Which cutaneous bacteria can cause toxic shock via a superantigen response
Staph. aureus
Strep. pyogenes
What are other cutaneous virulence factors of S. aureus?
- Exfoliative toxins
- Exotoxins A-D
- Cause Staphylococcal Scalded Skin Syndrome - Resistance to AMP
What toxins are non-mitogenic, cleave desmoglein causing intraepidermal splitting
Exotoxins A-D
Bacteria implicated for Scalded Skin Syndrome (serious peeling of the skin) via cleaving desmoglein proteins
Staph. aureus
dermal bacterial infection; obligate intracellular Gram - bacteria; TICK BORNE; causes Rocky Mountain Spotted Fever
Rickettsia rickettsii
dermal bacterial infection; Gram - bacteria; frequent colonizer of the nasopharynx; can cause disseminated infection including MENINGITIS
Neisseria meningitidis
dermal bacterial infection; sexually transmitted spirochete; rash characteristic of SECONDARY SYPHILIS
T. pallidum
class of microbes that can infect the skin; keratinophilic (love keratin); most common is T. rubrum; can cause superficial infections such as “ringworm” or “tinea”
dermatophytes
Common genera of dermatophytes
Trichophyton
Microsporum
Epidermophyton
MOST common dermatophyte
T. rubrum
What fungal virulence factors are associated with hyphal elements?
Keratinases
Proteases
Lipases
What can predispose you to a Candida albicans skin infection
Antibiotics (disrupts normal flora) Steroids Diabetes Obesity Immunocompromised pts
Viral pediatric infections: Enveloped RNA viruses
Measles
Rubella
*Included in MMR vaccine
Viral pediatric infections: Non-Enveloped DNA virus
Parvo B19 (cause red cheeks)
Viral pediatric infection: Enveloped DNA virus
HHV 6/7 (roseola)
Cutaneous virus that is associated with warts; non-enveloped DNA virus
HPV (Human Papillomaviruses)
Cutaneous virus that is associated with Molluscum contagiosum (umbilicated papules); enveloped DNA virus
Poxvirus
Cutaneous virus that is associated with Chickenpox (primary infection) and Shingles (reactivation); herpes virus
VZV (herpesvirus)
VZV affect what type of cells?
Neurons
small, ds, circular DNA virus that is ubiquitous and infect external cutaneous skin and mucosal membranes
HPV (Human papillomaviruses)
Why does VZV, a cutaneous viral infection, cause a dermatome distribution
Reactivates along dermatome of sensory nerves of dorsal root ganglia
Two types of shingles vaccines
- Zostavax
2. Shingarix (reduce chances of zoster by 90%; preferred by CDC)
What shingles vaccine has live, attenuated virus and is contraindicated for immunocompromised people or pregnant women?
Zostavax
What shingles vaccine has recombinant viral antigen + adjuvent; no contraindication
Shingarix
