Skin and Soft Tissue Flashcards
What is the first line of defense against microbial invasion?
Intact Skin
What do Rubor, Calor, Tumor, and Dolor mean respectively?
- Redness (erythema)
- Warmth
- Edema
- Tenderness (pain)
What did he say causes Crepitus?
-
What diseases would mimic a SSTI and would require a differential diagnosis?
- Gout
- Thrombophlebitis
- Deep vein thrombosis
- Contact Dermatitis
- Drug Eruption
- Foreign body reaction
What is folliculitis?
Minor infection, associated with friction and sweat gland activity
What types of bacteria can cause folliculitis?
- Staph Aureus
2. Pseudomonas Aeruginosa
What bacteria causes Hot tub folliculitis?
Pseudomonas Aeruginosa
How do you treat folliculitis?
Soap and water; Topical antibiotics
What bacteria cause Acne?
Propionibacterium acnes
How does Propionbacterium cause acne?
Multiplies behind or within sebum trapped in follicles or glands
Define Acne
Inflammation of hair follicles associated sebaceous glands
What can contribute to Acne?
Hormonal influences, organic acids produced by P. acnes
What is the most common cause of soft tissue abscess?
Staph aureus (this includes MRSA)
What causes a soft tissue abscess?
Any breach in the skin
What areas are often polymicrobial?
- Oral
- rectal
- Vulvo-vaginal
- IV drug users also
What is a Furuncle?
-Abscess in the area of a hair follicle
What is a furuncle often referred to as?
Boil
T/F Furuncles are often recurrent
TRUE
What is a carbuncle?
- Multilocated abscess
- Spread of infection to subcutaneous tissue
What causes a Carbuncle?
Staph Aureus
How do you treat a carbuncle?
Incision and drainage
What bacteria cause Necrotizing Fasciitis?
- Group A strep
- Staph Aureus
- Anaerobic: Colstricium perfringens (spores)
What is the virulence factor of Necrotizing Fasciitis?
Enzyme-producing bacteria that digest fascial barriers and cause tissue necrosis
At what rate can necrotizing fasciitis spread
rapidly
What is Fournier’s gangrene?
Polymicrobial infection of the genitals and perineum
Describe pain as a symptom of necrotizing fasciitis
Pain is usually out of proportion to exam findings
What are some common symptoms of necrotizing fasciitis?
- Edema
- Erythema
- Pain
- Crepitus * (rare)
What is the most common pathogen in surgical wound infections?
Staph Aureus
Where does the Staph Aureus come from to infect surgical wounds?
- Patient’s own skin or normal flora
- Transmission by fomites, hands, air
- Environmental
What is a fomite?
Inanimate objects that can transmit pathogenic organisms
What is the main where to prevent surgical wounds?
Perioperative antibiotics
What are the 3 genera that cause fungal infections?
- Trichophyton
- Microsporum
- Epidermophyton
What is the most common yeast infection?
Candida Albicans
How do you treat Candida albicans infections?
Topical antifungals; systemic antifungals if severe
What are the most common fungal infections that we see?
Dermathophyte fungi-Tinea Cruris, Corporis,
What type of infections do dermatophyte fungi cause?
Superficial hair skin and nail infections
- Ringworm
- Nail infections: onchomycosis
- Keratinized layers of skin or nails
What areas of the body are more prone to yeast infections?
Warm, most areas of the body: Mouth, vagina, armpit, fat folds, butt
What are three examples of yeast infections caused by candida?
- Diaper rash
- Intertrigo
- Thrush
Where would you find an impetigo infection?
Epidermis
What does impetigo look like?
Honey crust
What are two things that cause impetigo?
- Group A. Strep
2. Staph Aureus
T/F Impetigo is ugly but not contagious
FALSE, it is highly contagious
How do you treat Impetigo?
Penicillin, topical Antibiotic
What Causes Erysipelas?
Group A strep
Where would an Erysipelas infection be in the skin?
Deep layers of dermis
How do you treat Erysipelas?
Penicillin
T/F Erysipelas spreads rapidly
TRUE
What are some systemic signs that might accompany Erysipelas
Maybe a fever and headache, etc
What causes Cellulitis?
- Group A strep 2. Staph Aureus
3. Gram Negatives
Where in the skin does a cellulitis infection occur?
Subcutaneous tissue
In what situations would Gram negatives cause Cellulitis?
- Immunocompromised
- Nosocomial
- Wounds
- Diabetes Mellitus
How do you treat cellulitis?
Systemic antibiotics
Is culture useful with cellulitis?
Not really
What factors increase risk of wound infections?
- High number or organisms
- Higher Virulence of Organisms
- Poor circulation near wound
- Poor General health
- Poor nutrition status
- Diabetes
- Immune comporomise
What is the all time champion of microbial pathogens?
Staphylococcus Aureus
Puss causes _____, ___, locally destructive __ lesions
- Acute
- Aggressive
- Purulent
Where does staph colonize?
Anterior nares
What percent of the population is carrying staph at any given time?
10-30% although that percentage is higher in healthcare workers and patients
T/F once in skin, staph easily accesses deeper tissue through skin appendages or trauma
TRUE
What can alpha toxins from staph cause?
Staph scalded skin syndrome
What is Exfoliatin
Bullous Impetigo
What does TSST-1 cause?
Staph Toxic Shock syndrome
What toxin will cause Staphylococcal food poisoning?
Enterotoxin
What does MSSA stand for?
Methicillin-Sensitive Staphylococcus Aureus
How does MRSA become resistant to Beta lactams?
- Acquires mecA gene
- Makes new PBP with reduced affinity for Beta-Lactams
- Resistant to all Beta-lactams
What are the drugs of choice for MSSA?
- Anti-Staphylococcal PCN
- Nafcillin
- Oxacillin
- Cephalosporins
What are risk factors for MRSA
- Close skin-skin contact
- Crowded Living conditions
- Poor hygiene
- IV drug use
How do you treat MRSA?
- Trimethoprim-Sulfa
- Doxycycline
- Vancomycin
- Linezolid
- Daptomycin
What are some Post-Strep sequelaes?
- Rheumatic fever
- can follow Pharyngitis
- Post-strep glomerulonephritis
- can follow Pharyngitis or soft tissue infection
Group A strep has over ____ serotypes on antigenic differences in _____
- 100
2. M protein
In what way are Streptolysins O and S cytotoxic?
They lyse leukocytes, tissue cells, and platelets
Name 3 enzymes produced by Group A strep
- Streptokinase
- hyaluronidase
- DNase
What does Streptokinsase doe?
It is a protease
What does Hyaluronidase do?
Degrades Carbohydrates
What does DNase do?
Degrades DNA
Describe Clostridium perfringens
Anaerobic, spore-forming, gram positive rod with square ends
Where would you find Clostridium Pergringens?
Soil and human colon
What kind of infections can C. Perfringens cause?
Soft tissue infections:
- Wound infection
- Gas Gangrene: Traumatic wounds contaminated with spores from dirt or host’s own intestinal flora
- These infections can be rapidly fatal
T/F C. perfringens produces Hydrogen and CO2 gas in tissue and has multiple exotoxins
TRUE
What causes Pasteurella multocida and how do you get it?
Caused by gram negative rods and you can get it from animal bites
Describe Pseudomonas aeruginosa
Gram negative rod
Does P. Aeruginosa ferment things?
It is a prototypical non-fermenter
Where can you find P. Aeruginosa?
Environmental Pathogen:
- Water
- Hospital rooms
What can P aeruginosa cause?
- Numerous skin infections
- Examples:
- Hot tub folliculitis
- Secondary infection after burns
Describe Vibrio vulnificus
Gram negative rod
Where would you find vibrio vulnificus?
In salt water environments: colonize shellfish
What is vibrio vulnificus associated with?
Iron overload and cirrhosis
What does the progression of vibrio vulnificus look like?
Fever -> Sepsis –> Hemorrhagic Bullae
What do you call a Mycetoma infection?
Madura foot
What bacteria can cause Madura foot?
- Actinomyces
- Nocardia
T/F Madura foot can also be caused by fungus
TRUE
Lots of molds
What causes Sporotrichosis?
Sporothrix schenckii: rose gardener’s thumb
A microbiological diagnosis is often ____
Clinical
In a microbiological diagnosis, surface cultures are often ____, and rarely have _____
- Positive
- the pathogen causing the infection
Biopsies of microbiologic infections are rarely ____
Positive
Inflammation in infected areas is often due more to _____ rather than _____
- immune response
- “lots” of organisms
What is pus great for?
Diagnosis
If the infection is severe what can you use to help diagnose?
Blood cultures
If you see an abscess on the skin, what organism should you suspect?
Staph aureus
If you see an abscess in the mouth, rectum, or vagina what should be be thinking?
Polymicrobial infection
If you diagnose Cellulitis or Erysipelas what organisms should you be thinking of?
Strep pyogenes (Group A strep)
What are some host and exposure considerations to detect other possible pathogens in an infection?
- IVDU: pseudomonas
- Cat or dot bites: Pasteurella
