S1B5 - Zoonotic Bacteria Flashcards
What is the treatment for infection with Brucella?
Treatment for Brucella spp. infections include doxycycline and rifampin.
How are Brucella spp. transmitted?
Transmission of Brucella spp. occurs via ingestion contaminated animal products (unpasteurized milk and cheese), or entry of bacteria from infected animals or their secretions.
A doctor is struggling to diagnose a woman’s flulike illness. She complains of a fever that rises during the day and peaks after dinner, fatigue, spinal tenderness, and loss of appetite. Her lymph nodes are enlarged in physical exam. The doctor has trouble narrowing down the possible etiologies until he hears that the woman tasted goat cheese at a local French village a month before the onset of her symptoms. What organism is most likely the cause?
Brucella spp. are a group of gram-negative, coccobacilli, pleomorphic, aerobic bacteria that cause brucellosis (undulant fever). A mnemonic to help remember this is “Unpasteurized dairy products give you Undulant fever.”
In which cells do infections caused by Brucella localize? What are the consequences of this?
Brucella organisms survive within macrophages, where they are protected from antibodies, and localize in the reticuloendothelial system (liver, spleen, bone marrow, and lymph nodes). Granulomatous inflammation can eventually lead to abscess formation.
Can you name the six zoonotic bacteria that cause diseases in humans?
Zoonotic bacteria often have genera names ending in “-ella” and can be remembered by the mnemonic Big Bad Bugs From Your Pet named Ella
- Bartonella spp.
- Borrelia burgdorferi and other Borrelia spp.
- Brucella spp.
- Francisella tularensis
- Yersinia pestis
- Pasteurella multocida
A woman from Arkansas presents to the doctor with a small but persistent black ulcer on her arm. The area near the ulcer is erythematous and tender. Her axillary lymph nodes on the same side are enlarged. She believes the ulcer may be related to a tick bite that occurred on her arm while tending to her rabbit farm. What is the most likely organism?
F. tularensis can enter through skin and most often forms a papule that develops into an ulcer with a black base, known as the ulceroglandular tularemia. Bacteria can be phagocytosed and can enter the reticuloendothelial system, developing caseating granulomas and causing regional lymphadenopathy along with long-lasting fever.
How is tularemia transmitted to humans?
Transmission of F. tularensis can occur via
- Bite by tick or deerfly
- Handling infected animals, primarily rabbits
- Inhalation of aerosol (i.e. while mowing lawn, accidentally mow over infected animal such as rabbits)
What is the gram-staining and morphology of Francisella tularensis? Where are most cases reported? How do most patients infected present?
Francisella tularensis is a gram-negative, pleomorphic, coccobacilli that causes tularemia, with cases often occurring in Missouri and Arkansas. Tularemia is characterized by a site-specific infection and lymphadenopathy.
What’s the drug of choice for tularemia?
Treatment for tularemia is streptomycin.
How is Pasteurella multocida transmitted to humans?
P. multocida is part of the oral flora of domestic dogs and cats and is usually transmitted to humans through bites from these animals.
What are the treatment options for a Pasteurella multocida infection?
Treatment for P. multocida infections include penicillin G or amoxicillin and clavulanate.
A young girl, bitten by a cat earlier in the day, develops redness, heat, induration, and tenderness at the site of the bite. Her physician also notes local lymphadenopathy. Culture of wound site shows gram-negative coccobacilli with bipolar staining. What is the causative organism?
Pasteurella multocida is a gram-negative, pleomorphic, coccobacilli with bipolar staining pattern (similar to Yersinia pestis) that causes cellulitis and osteomyelitis following cat/dog bites.
What are the pathologies occurring from Pasteurella infection?
The most common clinical presentation of P. multocida infection is cellulitis originating from the site of the bite that rapidly spreads to the surrounding tissue. Osteomyelitis may be a complication, depending on the depth of the bite.
What are the clinical findings in brucellosis?
Clinical manifestations of brucellosis include:
- Undulant fever
- Night sweats (often described as profuse)
- Malaise
- Anorexia
- Arthralgias
- Fatigue
- Weight loss
