E2- Bacterial Skin Infection Flashcards
What kind of infections raise concerns over colonization with resistant bacterial or underlying issees?
Recurrent infections
What bacteria is apart of normal skin and mucous membrane inhabitants and is often introduced through breaks in skin?
Staphylococci
(inoculum is usually not large, meaning proper cleansing and disinfection with germicidal soap or other agents will prevent disease in persons of normal health)
If a foreign body is present (splinter, stitches, surgery) what does this mean for probability of infection?
Infectious dose drops dramatically (takes less bacteria to cause an infection, because the bacteria can hide better)
What is a disease of sebaceous follicles and is a noninfectious form of folliculitis?
Acne Vulgaris
What can trigger acne vulgaris?
Androgen hormones
Is Propionibacterium acne gram positive/negative? Shape? Oxygen tolerance?
Gram positive anaerobic rod (normal skin flora)
When does inflammatory acne vulgaris develop?
Develops when follicular contents rupture into the dermis
What is primary causative agent of Folliculitis?
Staph. aureus (majority of abscess-type infections)
What causes mild pain, itching/irritation with pustules or nodules surrounding hair follicles?
Folliculitis
What should you do if 1st line treatments are not working for tx of Folliculitis?
Gram stain to rule or gram- negative etiology or MRSA
What is secondary causative agent of Folliculitis?
Pseudomonas aeruginosa
Is Staph. aureus gram positive/negative? Shape?
Gram positive cocci
Is Pseudomonas aeruginosa gram positive/negative? Shape?
Gram negative rod
Where are Pseudomonas aeruginosa infections commonly acquired? How does t appear?
Hot tubs
Itchy maculopapular rash, some pustules
What is the causative agent of most furuncles?
Staph. aureus
What is an accesses that involves a hair follicle and surrounding tissue?
Furuncle (boil)
What is a cluster of furuncles with subcutaneous connections, that extend into dermis and subcutaneous tissue?
Carbuncle
Can furuncles or carbuncles cause systemic effects like fever and prostrations (exhaustion)?
Carbuncle
What populations commonly get furuncles/carbuncles?
Obese, immunocompromised, diabetic and elderly
How are furuncles and carbuncles treated?
Abscesses are incised and drained
Hot compresses
Abx if > 5 mm, do not resolve with drainage, on evidence of spreading, or occur in immunocompromised or subjects at risk of endocarditis
What kind of abx should you use to tx furuncles or carbuncles?
Use antibiotics that are effective against MRSA
What kind of abx should you use to tx furuncles or carbuncles if pt has fever or multiple abscesses?
Aggressive combination therapy with rifampin
How can you prevent recurrent furuncles?
Liquid soap containing chlorhexidine/isopropyl alcohol and maintenance antibiotics.
What is a superficial skin infection with crusting or bullae?
Impetigo (Pyoderma)
What causes Impetigo (Pyoderma)?
Staphylococci, streptococci or both.
What is severe form of impetigo featuring deep invasion of dermis caused by same agent producing non-bullous impetigo?
Ecthyma
What are risk factors for Impetigo and Ecthyma?
Moist environment, poor hygiene or chronic nasopharyngeal carriage of agents
What is the most common cause of non-bollous impetigo?
S. aureus - currently #1 cause, with MRSA in about 20% of recent cases
What is often co-infected with S. aureus impetigo?
Streptococcus pyogenes – (group B, β-hemolytic)
What are vesicles that enlarge to form bacteria-colonized fluid-filled bullae created by action of exfoliative toxin that disrupts epidermal cell connections?
Bullous Impetigo
What is another name for Staphylococcal Scalded Skin Syndrome?
Ritter’s Disease
What is an acute and extensive epidermolysis due to action of staphylococcal toxin (exfoliatin) that splits the skin just beneath the granule cell layer?
Staphylococcal Scalded Skin Syndrome
What is unique about the bullae in Staphylococcal Scalded Skin Syndrome?
Bullae are sterile – no bacteria or leukocytes, this is due to toxin
Staphylococcal Scalded Skin Syndrome is positive for what sign?
Positive Nikolsky’s sign, skin peels easily, desquamated areas look scalded
What are acute bacterial infections of the skin and (sometimes) deeper subcutaneous tissues?
Erysipelas and cellulitis
What is superficial cellulitis with focal dermal lymphatic involvement? What are the causative agents?
Erysipelas
Group A Streptococcus pyogenes
What is another name for erysipelas?
St. Anthony’s Fire
Patient presents with Erythematous, raised lesions with distinct borders (demarcation), rash, lymphadenopathy, fever, and chills. What do you suspect?
Erysipelas (St. Anthony’s Fire)
What is a unilateral infection involving deeper dermis and subcutaneous tissues?
Cellulitis
Patient presents with areas of heat, erythema, edema, and tenderness (HEET) unilaterally on the lower leg, localized sunburn-like area with indistinct borders that blend in elevation and color to surrounding tissue. What do you suspect?
Cellulitis - Wound may not be evident
What are the causative agents of cellulitis?
S. aureus and S. pyogenes
What should you avoid in the tx of cellulitis?
NSAIDS – may mask pain of developing myonecrosis and interfere with response to agent
Why do cultures rarely ID the pathogen in cellulitis infection?
Too many options to test for
Besides the major two, what are other agents known to produce cellulitis?
Acinetobacter baumannii Pasteurella multocida Capnocytphaga species Aeromonas hydrophilia Vibrio vulnificus
What pathogen is associated with cat bite infections?
Pasteurella multocida
What pathogen is associated with cuts from an oyster or salt water injury?
Vibrio vulnificus
What are signs of MRSA infection?
Redness, swelling, warmth, pain with: Fluctuance Yellow or white center Central point (head) Draining pus or ability to aspirate pus with syringe
How is MRSA dx?
PCR assay to detect mecA gene or latex agglutination assay
What part of the body do necrotizing infections affect?
Subcutaneous tissue, fascia, and/or muscle
How does Necrotizing fasciitis present?
HEET Pain out of proportion* Rapid progression over several days Skin changes color (red-purple to patches of blue-gray) Thick pink/purple fluid fulled bullae Cutaneous anesthesia
What makes dx of necrotizing fasciitis difficult?
Initially overlying tissue appears unaffected
Makes diagnosis difficult without surgical intervention
What will determine blood supply in a necrotizing fasciitis infection?
Involvement of muscle tissue
What type of Necrotizing fasciitis is most common? How is it characterized?
Type 1
Polymicrobic, one anaerobe plus one facultative anaerobe or aerobe
What is a major risk factor for Type 1 necrotizing fasciitis?
Diabetes
What is the mildest form of acne vulgaris that forms small firm pink bumps?
Papules
What form of acne vulgaris is clearly inflamed and contains visbable pus?
Pustule
What form of acne vulgaris is large, painful, inflamed, pus-filled lodged deep within the skin?
Nodule- most severe form
How should you treat extensive scalded skin syndrome? Does this syndrome have high or low mortality rates?
Treat as for burns
Mortality rate is low and often due to secondary infections
What type of Necrotizing fasciitis is “flesh-eating?”
Type 2
What is the causative agent of Type 2 Necrotizing fasciitis?
Group A Strep (monomicrobic)
How does the fascia present in Necrotizing fasciitis? Is there pus?
Fascia appears swollen and dull gray
No true pus anywhere, only thin brownish excudate
What differentiates Necrotizing fasciitis from Cellulitis?
Failure to respond to abx therapy
Cellulitis will typically respond in 24-48 hrs
What is another name for Clostridal myonecrosis?
Gas gangrene
What are the majority of Gas gangrene cases caused by?
Clostridium perfiringens type A
What type of organism is Clostridium perfiringens type A?
Spore forming, gram positive anaerobic bacillus
In a Gas gangrene infection, what promotes split and invasion of nearby tissue?
Production of exotoxins and insoluble H2 gas
Patient presents with rapid onset of pain. The skin has a bronze appearance, tense edema, is intensely tender, and crepitant. There is overlying bullae. What do you suspect?
Gas gangrene
How is Gas gangrene dx?
Tissue biopsy and presentation
** biopsy gram stain will show muscle necrosis, gram-variable rods, and tissue destruction
What is shown on a gram stain of a Gas gangrene tissue biopsy?
Muscle necrosis
Gram-variable rods and tissue destruction
What are the two causative agents of Toxic Shock Syndrome?
Staph aureus and Strep pyogenes
Patient presents with soft tissue inflammation at the site of skin infection that leads to bacteremia and necrotizing fasciitis. What do you suspect?
Streptococcal Toxic Shock Syndrome
What pathogen is responsible for toxic shock syndrome associated with tampon use?
Staphylococcus aureus
What triggers the immune response in toxic shock syndrome?
Non-specific binding of toxin to receptors
What treatment is usually sufficient for folliculitis?
Topical Clindamycin ointment or Benzoyl peroxide wash
What is the management of scalded skin syndrome?
Prompt diagnosis and therapy with penicillinase-resistant anti-staph antibiotics.
What is the treatment of erisepelas?
Oral or IV antibiotics targeted against the most likely agent
Is the treatment for cellulitis?
Empiric Abx treatment, but be aware infections may be mixed etiology
What is the causative agent of Type 1 necrotizing fasciitis?
Group A strep (pyogenes) and anaerobes
What is the treatment for necrotizing fasciitis?
- Surgical debridement
- Amputation
- IV antibiotics
What is the common way to get gas gangrene?
Direct introduction of anaerobic cells or spores into a wound
How is gas gangrene treated?
IV antibiotics, hyperbaric oxygen therapy, and surgical debridement/amputation
*** on surgery, infected muscle wil be dark red/black, noncontactile, and will not bleed
