Lecture 2: Infectious Diseases Affecting Skin, Soft, Tissue, and Eyes Flashcards
Dysbiosis
sustained alteration of microbiota resulting in overt inlammation
Functions of skin
protects uderlying tissues from microbial colonization
Each layer with specific activities
epidermal with keratinocytes (producted in stratum basal, die in stratum corneium, dry & waterproof) with dendritic langerhang cells
Dermal: sweat glands, sebceous glands
Skin microbiota
protects deeper tissues from infections
Sebaceous sites of skin have…
…the lowest bacterial diversity
Moist sites of skin colony examples
Staph and coryneobacterium (gram +)
Dry sites of skin colony examples
highest diversity, s epidermidis, and gram - species
Acne
most common skin disease in world
chronic, inflammatory condition sometimes involving cutibacterium acnes
c. acnes part of normal microbiota
Pilosebacceous unit
hair follicle + sebaceous gland
*plugged sebaceous glands can deveop into papules or nodules
sebum+ c.acnes in pores can lead to acne
Biofilms
endogenous microbiota can form biofilms
biofilm=any group of microorganisma in which cells stick together and adhere to a surface
thrive in warm, humid climates
Staphylococci
Gram + spheres form clustered arrangements
several species cause disease: S. aureus (MRSA, MSSA), S. epidermidis, S. Saprophyticus (UTIs)
makes coagulase- if it is coagulase + that is indicitive of S. aureus
produce catalase, converts h2o2 to water and o2. Catalase test is useful to distinguish staph from streptococci and enterococci
MRSA
caused by staph aureus
-resistant to all beta-lactams/cephalosporins (*EXCEPT: ceftobiprole & ceftaroline)
Staphylococcal Contact Diseases 2 types
- Localized skin infections: abcess, folliculitis, furnuncle
- toxin generated diseased: impetigo, scalded skin syndrome, toxic shock syndrome (TSS)
Abcess
Pus-filled lesion on skin normally in dermis
Folliculitis
puss-filled pocket at base of hair folliclue
caused by Grp A streptococcus
Furnuncle
infection further down hair follicle, carbuncle group of furnucles
large, warm, painful
caused by grp A streptococcus
Streptococci
gram-positive
normal skin inhabitant
grow in chains
Streptococci classification systems
Hemolytic groups: behavior on blood agar
- aplha- olive green
- beta-clear
- gamma- no change
Variants of cell wall carbs:
- Grp A= s. pyogenes
- Grp B= s. agalactiae
*important because each species treated diff
Cellulitis
pathogen
morphology
P: Grp A Streptococci
M: Non purulent (no puss associated)
severe infection of dermis and SQ tissue
skin erythema, edema, warmth
Streptococcal pharyngitis pathogen
P: Grp A Streptocci
“strep throat”
ErySipelas
Pathogen
morphology
P: Grp A Streptococci
M: superficial form of celluitis of dermis
upper dermis with clear demarcation between involved and uninvolved