Skin and Soft Tissue Infections (SSTIs) Flashcards
What are some normal skin microbiota?
staphylococcus epidermidis, other staph spp., cutibacterium acnes, corynebacterium spp., and candida
What is the first line of defense against SSTI’s?
intact skin (physical barrier)
How does loss of intact skin led to infection?
loss of the physical barrier leaves room open for pathogens to enter, ducts of skin structures permit microbial invasion
What diseases can mimic SSTI’s?
gout, thrombophlebitis, deep vein thrombosis, contact dermatitis, eczema, drug eruption, and foreign body reaction
How does a SSTI typically present?
classic presentation = “rubor, calor, tumor, dolor” (redness, heat, swelling, pain) with erythema, warmth, edema, and tenderness
How would you examine a skin infection?
describe extent, location, and demarcation; describe if purulent or not
What are associated signs of SSTI’s?
crepitus: popping sensation under skin
necrosis: dying skin
fluctuance: wavy feeling when wound palpated - fluid
purpura: purple colored spots on skin - sepsis
bullae: blister seen with forms of impetigo
systemic signs: fever, night sweats, etc
What are the layers of involvement?
the epidermis, dermis, and subcutaneous; the deeper the invasion the more significant symptoms and sign will appear
At what layer of involvement does the immune system act?
once the stratum corneum is passed
What is follicultis?
superficial infection relating to infection of hair follicles and skin
What are the symptoms of folliculitis?
purulence, minor infection on hair-bearing skin, associated with friction and sweat gland activity
What pathogens cause folliculitis?
staphylococcus aureus and pseudomonas aeruginosa (when tied to hot tub)
How do we treat folliculitis?
usually self-limiting; soap and water, topical antibiotics, and treatment of any co-infections
What is acne?
acne is inflammation of hair follicles and associated sebaceous glands
What pathogen can be behind acne?
cutibacterium acnes
What is a cutaneous soft tissue abscess?
anything larger than acne pustule or folliculitis, and is a collection of pus (white blood cells, living and dead bacteria)
Where can cutaneous soft tissue abscesses occur?
can occur anywhere
What can cutaneous soft tissue abscesses cause?
local superficial cellulitis, bacterial necrose/liquefy tissue, cellular debris and WBC accumulation
How do we know its a cutaneous soft tissue abscess?
fluctuant, tender, erythematous nodule with surrounding erythema, and purulence
What can causes cutaneous soft tissue abscesses
staphylococcus aureus, and MRSA in some cases
In who do we see polymicrobial cutaneous soft tissue abscesses?
in IV drug users, oral, rectal, and vulvo-vaginal infections
What is the treatment for cutaneous soft tissue abscesses?
incision and drainage (I&D) and systemic antibiotics if needed
What are types of cutaneous soft tissue abscesses?
furuncle: abscess in area of hair follicle, “boil”, recurrent
carbuncle: multiloculated abscess, spread infection to subcutaneous tissue, caused commonly by staph. aureus, and the treatment is I&D “showerhead of pus”
What is impetigo?
non-purulent infection of the epidermis with a “golden honey crust” lesion that is highly contagious
What typically causes impetigo?
group A streptococcus, sometimes staphylococcus aureus
How do we treat impetigo?
penicillin (clindamycin), topical antibiotics, and treatment of any co-infections
What is erysipelas?
an acute deeper infection of the dermis that involves the blocking of dermal infatics
What does erysipelas present like?
non-purulent, rapidly spreading, “rubor, calor, tumor, dolor”, strict end to redness
What causes erysipelas?
group A streptococcus, often pain, fever, and cellulitis accompanies
How do we treat erysipelas?
penicillin (clindamycin)
What is cellulitis?
an infection of the subcutaneous tissue, diffuse acute inflammation
What can cellulitis cause?
systemic signs (fever, body aches, etc.), can trigger sepsis
What typically causes cellulitis?
often group A streptococcus, sometimes staphylococcus aureus (or MRSA), and H. influenzae in kids
How do we treat cellulitis?
systemic antibiotics
What is necrotizing fasciitis?
a CRITICAL condition; inflammatory response to infection in the soft tissue below the dermis
What does necrotizing fasciitis do?
enzyme-producing bacteria digest the fascial barriers causing tissue necrosis; spreads RAPIDLY
What can we see with necrotizing fasciitis?
gas build up with a crepitus feeling (gas gangrene)
What is fournier’s gangrene?
a specific type of necrotizing fasciitis of genitals and perineum
What are the types of necrotizing faciitis?
Type 1: aerobic and anaerobic bacteria (synergistic)
Type 2: monomicrobial
Type 3: often marine related
What causes type 1 necrotizing fasciitis?
often clostridium perfringens, bacteroides, enterics, ect.
What causes type 2 necrotizing fasciitis?
group A streptococcus (“flesh-eating bacteria”) or staphylococcus aureus
What causes type 3 necrotizing fasciitis?
often vibrio vulnificus (salt water) or aeromonas spp. (leeches)
How does necrotizing fasciitis present?
VERY sick, pain out of proportion to exam findings, edema, erythema, pain, and sometimes crepitus
How do we treat necrotizing fasciitis?
surgical debridement and a combination of systemic antibiotics
What layer of involvement can necrotizing fasciitis reach?
includes the deep fascia and subcutaneous fat
What typically cases surgical wound infections?
staphylococcus aureus, often MRSA
How can we prevent surgical wound infections?
hand washing, changing gloves often, and perioperative antibiotics = mainstay of prevention
What can cause fungal skin infections?
dermatophyte fungi such as tinea cruris, corporis, etc.
(ringworm, nail infections/onychomycosis, and keratinized layers of skin/nails)
What are the three genera that cause dermatophyte infections?
trichophyton, microsporum, and epidermophyton
What can cause a yeast infection?
candida albicans
What is intertrigo/diaper rash?
skin infection cause by a yeast (diaper rash when near genital region of baby); inflammatory cutaneous tissue in areas subject to heat, moisture, and friction
What infectious agents enhance intertrigo?
candida albicans (acidic bowels can irritate as well)
Where is intertrigo often found?
in skin folds such as armpits, perineum, underneath breasts, and abdominal folds
How do we treat intertrigo?
topical antifungals and allowing the skin to heal and dry out
What is thrush?
a yeast or candida albican infection in the mouth
Who is thrush common in?
babies, immunocompromised, those that use steroid sprays for asthma (rinse mouth to help prevent!!)
What does oral thrush look like?
white lesions on tongue and inner cheeks
How do we treat thrush?
antifungals
What bug factors increase risk of wound infections?
higher number of organisms, virulence of organisms (protease -destroy tissue proteins, hyaluronidase - “spreading factors” that breaks down proteoglycans in CT, lipase - degrades fat and oils)
What patient factors increase risk of wound infections?
poor circulation near wound, poor general health, poor nutritional status, diabetes, immunocompromised, etc.
What is the leading cause of immunosuppression worldwide?
MALNUTRITION!
What does S. aureus cause?
MOST common cause of SSTI’s in the US; causes acute, aggressive, locally destructive purulent lesions
What are staphylococcal toxins?
protease, hyaluronidase, lipase, alpha-toxin (S. scalded skin syndrome), exfoliatin (bullous impetigo), TSST-1 (S. toxic shock syndrome), enterotoxin (S. food poisoning)
What is scalded-skin syndrome (SSS)?
caused by alpha-toxin; occurs sporadically with large blister full of clear fluid and within a few days the overlying skin will sluff off
What is bullous impetigo?
more extreme presentation of impetigo that has blisters resembling a localized SSS infection
What is toxic shock syndrome (TSS)?
systemic infection associated with tampon use in healthy women (not confined to females); involves multiple organ systems, fever, hypotension, diffuse erythematous rash, and diffusion of skin in two weeks or so
What is MRSA? When should we think of it?
methicillin resistant S. aureus; think of MRSA whenever thinking S. aureus
What are risk factors for MRSA outbreaks?
close skin-skin contact, crowded living conditions, poor hygiene, and IV drug use
How do we treat MRSA?
trimethoprim-sulfa, doxycycline, vancomycin, linezolid, and daptomycin
What does group A Streptococcus cause?
non-purulent lesions, non-bullous impetigo, erysipelas, and TSS
What is strep to toxic?
it creates lots of different toxins or different strains depending on the strain; streptolysins O and S lyses your cells, pyrogenic exotoxins A and B (superantigens) activate massive numbers of T-cells - huge cytokine production, can cause systemic illness and SHOCK
What is Clostridium perfringens?
anaerobic, spore-forming, gram + rod with square ends
What do we ALWAYS keep in mind after a strep infection?
look for post strep sequelae as the leftovers will cause your body to attack itself
What does Clostridium perfringens cause?
gas gangrene and crepitus; dramatic and rapid wound infections that can be fatal
What is Eikenella corrodens?
part of the normal mouth flora, gram stain is slender, straight, small, GNR
What does Eikenella corrodens smells like in gram stain?
bleach!
How is Eikenella corrodens spread?
human bite wounds, and isolated from head and neck infections
What is pasteurella multocida?
GNR we associate with animal bites; creates dramatic immune response quickly after bite
What is Pseudomonas aeruginosa (non-fermenter)?
GNR, normal flora in our environment, can live at high temperatures
What can Pseudomonas aeruginosa (non-fermenter) cause?
numerous diseases; in skin it causes hot tub folliculitis and secondary infections after burns (turn dressings nasty green color)
What is Vibrio vulnificus?
GNR we associate with salt-water and shell fish
What can Vibrio vulnificus cause?
fever, sepsis, hemorrhagic bullae; associated with iron overload, cirrhosis, and hurricane clean-up efforts
What viral infections can cause SSTI’s?
herpes simplex virus, herpes zoster, measles, warts, and mpox
What is herpes simplex virus (HSV)?
HSV1 (mouth) and HSV2 (genitals), agent that causes cold sores or genital herpes sores; not JUST a STI - can be caused by stress or sun exposure
What is Varicella?
primary VZV infection; chickenpox, most common in children
What is herpes zoster?
secondary/reactivation VZV infection; shingles pain on sensory nerve before onset of eruption 1-3 dermatomes
What is measles?
rubeola virus causes this disease; VERY contagious, causes cold like symptoms with koplik spots and rash extending from the fact to the soles of the feet
What can cause warts?
human papillomaviruses (HPV) - can lead to cancer down the line
What are the two types of warts?
skin - flat, superficial
plantar - deep growths
What can mpox cause?
infects the skin and creates rashes and lesions that progress through stages
How do we get microbiological diagnosis from patients with skin infections?
often clinical - by what you visually see; surface cultures are rare, pus can be used and blood cultures can help if the infection is severe
SUMMARY
purulent abscess of skin - think S. aureus
abscess in mouth/rectum/vagina - think polymicrobial
cellulitis and erysipelas - think strep pyogenes (group A)
