156: Miscellaneous Bacterial Infections with Cutaneous Manifestations Flashcards
(233 cards)
What is the primary mode of transmission for Bacillus anthracis in humans?
The primary mode of transmission for Bacillus anthracis in humans is through percutaneous inoculation of anthrax spores, which accounts for approximately 95% of cases. Other modes include inhalation and gastrointestinal disease.
What are the major virulence factors of Bacillus anthracis?
The major virulence factors of Bacillus anthracis include:
- Poly-Y-D-glutamic acid capsule: Provides protection against phagocytosis.
- Tripartite anthrax toxin: Contains three proteins: Protective antigen (best target for vaccines or immunotherapy), Lethal factor, Edema factor.
What are the clinical findings associated with cutaneous anthrax?
Clinical findings associated with cutaneous anthrax include:
- Incubation period: 1-7 days.
- Symptoms: Low-grade fever, malaise, and development of a painless papule at the exposed site, which becomes edematous.
- Pain: If present, results from edema-associated pressure or secondary infection.
Describe the progression of cutaneous anthrax lesions.
The progression of cutaneous anthrax lesions follows these phases:
- Dermal papule
- Vesicle
- Pustule
- Eschar
Lesions may appear with regional lymphadenitis, malaise, and fever. Individual lesions may be pustular, leading to the term malignant pustule, but true pustules are rare. Lesions can enlarge into a pseudobulla with hemorrhagic necrosis and may be umbilicated.
What is the recommended treatment for naturally occurring anthrax?
The recommended treatment for naturally occurring anthrax includes:
- Penicillin or doxycycline.
- For suspected bioterrorism-associated anthrax, fluoroquinolone is recommended (safe for pregnant women and children).
- Raxibacumab is used for inhalational anthrax.
- Treatment of primary cutaneous anthrax continues with parenteral therapy until local edema disappears or the lesion dries up over 1-2 weeks.
What is the causative agent of anthrax?
Bacillus anthracis, a large aerobic, spore-forming Gram-positive rod.
How can anthrax be contracted?
Through direct handling of infected animals, contaminated soil, or processing of hides, wool, hair, or meat.
What is the incubation period for anthrax?
1 to 7 days.
What are the initial symptoms of cutaneous anthrax?
Low grade fever, malaise, and a painless papule at the exposed site that becomes edematous.
What are the phases of cutaneous anthrax lesions?
Dermal papule -> vesicle -> pustule -> eschar phases.
What is a characteristic feature of lesions caused by cutaneous anthrax?
Lesions may appear pustular but do not suppurate; true pustules are rare in anthrax.
What is the treatment for naturally occurring anthrax?
Penicillin or doxycycline.
What is the significance of the protective antigen in anthrax?
It is the best target for vaccines or immunotherapy.
What is the term for the syndrome associated with cutaneous anthrax?
Ulceroglandular syndrome, characterized by fatigue, fever, chills, and tender regional adenopathy.
What happens to the eschar in cutaneous anthrax lesions?
The eschar dries and separates in 1 to 2 weeks.
A farmer presents with a painless papule on his hand that has progressed to a black eschar surrounded by non-pitting edema. What is the most likely diagnosis, and what is the first-line treatment?
The most likely diagnosis is cutaneous anthrax. The first-line treatment is penicillin or doxycycline for naturally occurring anthrax, or fluoroquinolone for suspected bioterrorism-associated anthrax.
A patient presents with a painless ulcer on the hand and regional lymphadenopathy after handling contaminated animal hides. What is the diagnosis, and what are the major virulence factors of the causative organism?
The diagnosis is cutaneous anthrax. Major virulence factors include the poly-γ-D-glutamic acid capsule and the tripartite anthrax toxin (protective antigen, lethal factor, and edema factor).
What are the major virulence factors of Bacillus anthracis and their significance in anthrax infection?
The major virulence factors of Bacillus anthracis include:
- Poly-Y-D-glutamic acid capsule: A protective capsule that helps the bacteria evade the immune system. Best target for vaccines or immunotherapy.
- Tripartite anthrax toxin: Composed of three proteins: Protective antigen, Lethal factor, and Edema factor. Contributes to the pathogenicity and severity of the disease.
Describe the progression of cutaneous anthrax lesions and their clinical implications.
The progression of cutaneous anthrax lesions follows these phases:
- Dermal papule - initial painless papule at the exposed site.
- Vesicle - develops from the papule.
- Pustule - may appear but true pustules are rare in anthrax.
- Eschar - the lesion dries and separates in 1-2 weeks.
Lesions may be accompanied by regional lymphadenitis, malaise, and fever. The lesions are caused by toxins and are unaffected by antibiotics, indicating the need for timely treatment to prevent complications.
What is the recommended treatment for primary cutaneous anthrax and the rationale behind it?
The recommended treatment for primary cutaneous anthrax includes:
- Penicillin or doxycycline for naturally occurring anthrax.
- Fluoroquinolone for suspected bioterrorism-associated anthrax, even in pregnant women and children.
- Raxibacumab for inhalational anthrax.
Treatment is continued with parenteral therapy until local edema disappears or the lesion dries up over 1-2 weeks, ensuring effective management of the infection and prevention of severe complications.
What is the prognosis for untreated cutaneous anthrax?
Untreated cutaneous anthrax, particularly if nonedematous, is self-resolving. However, lesions with massive edema pose a risk of bacteremia with subsequent septicemia, and the mortality rate of untreated cutaneous anthrax is 5-20%.
What are the major clinical presentations of tularemia?
The six major clinical presentations of tularemia are:
- Glandular
- Ulceroglandular
- Oculoglandular
- Oropharyngeal
- Typhoidal
- Pneumonic.
How is tularemia transmitted?
Tularemia is transmitted through:
- Tick vectors (e.g., Dermatocentor variabilis, Amblyomma americanum, Ixodes sp.)
- Arthropod vectors (e.g., Chrysops discalis, mosquitoes)
- Domestic cats via direct contact, bite, or aerosol
- Aquatic rodents (muskrats and beavers), household rodents, and contaminated drinking water
- Direct inoculation into conjunctivae
- Ingestion of poorly cooked, contaminated meat.
What are the clinical findings associated with ulceroglandular tularemia?
In ulceroglandular tularemia, a painful red papule appears at the inoculation site, which enlarges and evolves into a necrotic chancriform ulcer covered by a black eschar. Regional lymph nodes are large and tender, and bacteremia may cause sepsis and pneumonia.