Ebright - Infection of the Skin and Soft Tissue Flashcards
- A nurse comes to your clinic with a painful finger. Examination reveals a small cluster
of pustules over the middle phalanx of her index finger. There is cellulitis surrounding the
pustules. Your best approach would be?
a) Lance and drain the pus
b) Unroof a blister and test for virus
c) Begin Cephalothin
d) Apply mupirocin ointment and elevate the hand.
B
- A cat bites you. You should be concerned about getting a skin and soft tissue infection
with which group of organisms?
a) Streptococcus agalactiae, and Salmonella species
b) Pasteurella and streptococcus species
c) Capnocytophagia and clostridia
d) Pseudomonas and klebsiella
B
- A frustrated football coach comes to you because several of his players have had boils
on their arms and bodies over the past three weeks. One of the players has experienced
recurrent spiderbite-like lesions over this period. The team doctor has treated them with
penicillin which seemed unhelpful. A second antibiotic course with cephalexin also proved
unsuccessful. What antibiotic would you suggest?
a) Gentamicin
b) Dicloxacillin
c) Nitrofurantoin
d) Trimethoprim-sulfa
D
- A young man comes to see you in June because he has developed a “flu-like” illness
after camping and hiking on vacation in North Carolina. He’s especially concerned because
he’s developed a rash over his extremities; some spots are on his palms. The infectious cause
for this illness was probably acquired by?
a) Mosquito bite
b) Contaminated soil
c) Tick bite
d) Aerosolized white-footed mouse feces
C
Skin disease caused by these agents in 3 ways:
Exogenous: direct infection by agents external to the skin (ie. bacteria entering through a cut)
Endogenous: spread of organisms to the skin via the blood stream, along nerve pathways, or by extension from an adjacent site
Indirectly: from toxins produced by bacteria located outside the integument
EXOGENOUS INFECTIONS:
• General:
What happens in the majority of cases?
What are the most common infecting organisms?
In the majority of cases, some type of skin injury proceeds infection
Most common infecting organisms of the skin are bacterial:
o S.aureus
o S.pyogenes
Impetigo
Location
Typical Organism
Clinical information
Treatment
Location: Epidermis
Typical Organism: S.aureus/S.pyogenes
Clinical information:
- Weeping, crusted lesions (honey-colored)
- Patient is irritable and uncomfortable, but not febrile or seriously ill
- Post-Streptococcal Glomerulonephritis: can occur due to impetigo caused by S.pyogenes
Treatment: Topical Abx (Mupirocin)
Oral Abx
-Common among children
Erysipelas
Location
Typical Organism
Clinical information
Treatment
Location: Epidermis and dermis
Typical Organism: S.pyogenes
Clinical information:
- More serious
- Common in older adults
- Elevation of involved tissue, forming sharp borders
- Bright red and painful
- Fever common
Treatment: Oral or IV penicillin
Cellulitis
Location
Typical Organism
Clinical information
Treatment
Location: Epidermis, dermis and subcutaneous
Typical Organism: S.aureus, Streptococcus
Clinical information:
- Borders not as clear
- Fever is present
- Skin is edematous, warm, erythematous, tender and painful
- Vesicles/bullae common
- Ecchymosis in severe cases
Treatment:
Oral or IV penicillin
Cefazolin (May need to treat for CA-MRSA)
Folliculitis
Location
Typical Organism
Clinical information
Treatment
Location: Hair follicle (superficial)
Typical Organism: S.aureus
Clinical information:
Superficial
-Usually multifocal pustules
Treatment: –
Furuncle (Boil)
Location
Typical Organism
Clinical information
Treatment
Location: Hair follicle (deep)
Typical Organism: S.aureus
Clinical information:
- Deeper and more extensive
- Large, painful local boils
- Surrounding inflammation or cellulitis
Treatment:
Lance, drain (often all that is needed)
Cephalosporin/Dicloxacillin (May need to treat for CA-MRSA)
Carbuncle
Location
Typical Organism
Clinical information
Treatment
Location: Multiple furuncles in confined area
Typical Organism: S.aureus
Clinical information:
- Typical area is back of the neck
- Patient often acutely ill
Treatment:
-Requires systemic Abx and surgical drainage
Fasciitis
Location
Typical Organism
Clinical information
Treatment
Location: Fascia
Typical Organism:
S.pyogenes ("Flesh-eating strep)
S.aureus
Vibrio vulnificus (sea water exposure)
Anaerobic organisms
Polymicrobial infections including gram (-) enteric organisms
Clinical information:
- Patient acutely ill and in marked pain
- Skin overlying the infected area can be unremarkable
- Can also have changes such as gas in the tissue, hemorraghic bullae, ecchymosis, necrosis, woody induration, and cutaneous anesthesia
Treatment:
Emergency surgery and debridement
Systemic Abx (IV)
Myonecrosis (Gas Gangrene)
Location
Typical Organism
Clinical information
Treatment
Location: Muscle
Typical Organism:
Anaerobic streptococci
Gram (-) enterics
Clostridia spp. (gas gangrene)
Clinical information:
- Patient acutely ill and in marked pain
- Skin overlying the infected area can be unremarkable
- Can also have changes such as gas in the tissue, hemorraghic bullae, ecchymosis, necrosis, woody induration, and cutaneous anesthesia
Treatment:
Emergency surgery and debridement
Systemic Abx (IV)
ENDOGENOUS INFECTIONS:
• General:
- Skin can become infected by microorganisms that spread from another infected site in 3 ways
o Direct extension
o Hematogeneous Spread
o Spread along neurons
ENDOGENOUS INFECTIONS:
Typical Appearance:
Hematogenous Bacterial Infections:
Hematogenous Bacterial Infections: lesions are circumscribed (confined to a limited area) and appear singly or multiply as macule, papules or pustules (not spreading cellulitis)
ENDOGENOUS INFECTIONS:
Typical Appearance:
Hematogenous Viral Infections:
Hematogenous Viral Infections: present as widespread, symmetric lesions that frequently become confluent after initially presenting as discrete macules, papules, or vesicles (these rashes are called exanthems)
ENDOGENOUS INFECTIONS:
Typical Appearance:
Viral Infections with Neuronal Spread:
Viral Infections with Neuronal Spread: only local skin involvement (follow neuron)
Sources of Endogenous Skin Infections:
Direct Extension:
Osteomyelitis: draining sinus
Septic Arthritis: draining sinus
Lymphadenitis:
- TB
- Atypical mycobacteria
- Streptococcal infections
Oral/Dental Infection:
- Actinomycosis
- Mixed cellulitis
Sources of Endogenous Skin Infections
Hematogeneous Spread:
o Bacteremia o Endocarditis o Fungemia (candidemia) o Viremia: o Rocky Mountain Spotted Fever o Secondary Syphilis: lesions on soles of the feet and palms of the hands (as well as elsewhere)
Endogenous Skin Infections
Hematogeneous Spread
Viremia:(4)
Measles (rubeola): exanthem (macular-papular)
Koplik spots in oral mucosa very diagnostic;
Rubella (German Measles): exanthema, macular-papular
Chicken pox: exanthem (vesicles)
- Characterized by multiple different patterns in clusters (not all spots of same type due to the fact that break-outs occur in waves and not all at once)
Endogenous Skin Infections
Hematogeneous Spread
Bacteremia: (4)
Menigococcus
Gonococcus: lesions spread out, usually on extremities (macules or papules)
S.aureus
Pseudomonas
Endogenous Skin Infections
Spread Along Neurons (2):
Herpes Simplex Infection:
- Herpes labialis: HSV-1 (vesicles on lip)
- Herpes genitalis: HSV-2 (genital vesicles/ulcers)
Varicella Zoster (Shingles): dermatomal spread in older and immunocompromised (vesicles)
TOXIN MEDATED SKIN DISEASE (2):
Scarlet Fever
S.aureus
Scarlet Fever
Causative Agent:
Description:
Causative Agent: S.pyogenes
Description: primary strep throat infection that releases an erythrogenic toxin
o Toxin spreads systematically and causes diffuse red rash that feels like sandpaper
Staphylococcus aureus:
• Staphylococcus aureus:
2 different toxins that cause skin disease:
o Exfoliatin
o Toxic Shock Syndrome Toxin (TSST-1)
Scarlet Fever
Associated Symptoms:
Circumoral pallor (white area around the mouth)
Deep red lines (Pastia’s lines) in skin fold of neck, axilla, elbows and knees
Strawberry tongue
Extensive desquamation of superficial skin layers on recovery
Staphylococcus aureus
Exfoliatin Toxin:
Exfoliatin: results in bullous impetigo or scalded skin syndrome (more extensive)
Bullous Impetigo: differs from the S.pyogenes impetigo due to the fact that there are large vesicles/bullae
Scalded Skin Syndrome: widespread intra-epidermal cleavage, blistering and superficial epidermal sloughing (scary, but kids often make full recovery)
Staphylococcus aureus
Toxic Shock Syndrome Toxin (TSST-1):
Toxic Shock Syndrome Toxin (TSST-1): Hematogenous spread of the toxin results in high fever, hypotension, multi-organ injury and diffuse erythematous rash that desquamates on recovery (especially around nail beds, hands and feet)
Clinical Settings and Infecting Pathogens
Hot Tub folliculitis: Lymphatic obstruction/edema: Aquarium exposure: Freshwater exposure: Salt water exposure: Animal bites: Fingers of healthcare workers: Vesicles by dermatome: Neutropenic patient: Gangrene:
Hot Tub folliculitis: Pseudomonas
Lymphatic obstruction/edema: Streptococcus species
Aquarium exposure: Mycobacterium marinum
Freshwater exposure: Aeromonas species
Salt water exposure: Vibrio species
Animal bites: Pasteurella multocida
Fingers of healthcare workers: Herpes simplex (Whitlow)* (Endogenous)
Vesicles by dermatome: Herpes zoster* (Endogenous)
Neutropenic patient: Pseudomonas (ecthyma gangrenosum)* (Endogenous)
Gangrene: Clostridia species
Skin and soft tissue can be infected by microorganisms of all major types.
Skin disease caused by these agents occurs in three ways:
1.) Direct infection by infectious agents external to the skin, such as bacteria entering
through a cut or injury (exogeneous).
2.) Spread of organisms to skin via the blood stream or along nerve pathways; or by
extension from an adjacent infected site (endogenous).
3). Indirectly, from toxins(s) produced by bacteria located outside the integument.
Small pox
Agent:
Skin Manifestations:
Agent: Variola
Skin Manifestations: Exanthem, vesicles, pustules
Hand, foot, mouth
Agent:
Skin Manifestations:
Agent: Enterovirus
Skin Manifestations: Vesicles in mouth, hands, feet
Staphylococcal toxic shock syndrome
Treatment:
IV nafcillin, aggressive fluid and b/p
support
CA-MRSA (boils/cellulitis)
Treatment:
Lance, drain, oral trimethoprim-sulfa,
clindamycin or doxycycline
