Gram (-) Bacilli - Zoonotics Flashcards
List the gram (-) bacilli that are commonly known as zoonotics (4)
Bartonella henselae
Brucella
Francisella tularensis
Pasteurella multocida
What diseases are caused by Bartonella?
Cat Scratch Fever/Disease
Bacillary Angiomatosis
How do you visualize Bartonella?
It is technically gram (-), but you need Wartharin-Starry stain (a type of silver stain) to visualize
Cat Scratch Disease
Transmitted through cat scratches
Can involve regional lymph nodes (lymphadenitis) and causes painful swelling in nodes (esp axilla)
Occurs in patients who are immunocompetent
Usually self-limiting and doesn’t require Tx.
Cat Scratch Disease Tx
Usually self-limiting and doesn’t require Tx
If pain from lymph nodes or swelling is too much you can give azithromycin (Macrolides).
Bacillary Angiomatosis
Spread through cat scratches/bites
Only occurs in immunocompromised patients (HIV).
Causes fevers, chills, HA
Raised, red vascular lesions all over skin
A lot like Kaposi Sarcoma (both in HIV/immunocompromised, and both present with red vascular lesions)
Bacillary Angiomatosis Tx
Doxycycline
Also Macrolides
What is the main reservoir for Brucella?
Mostly associated with cattle and other farm animals
Cows, sheep, pigs, goats (each have own Brucella species)
Direct contact with animals in patients is usually seen - veterinarian, slaughterhouse worker, rancher
OR
Indirect contact like recent consumption of milk or dairy products, ingestion of unpasteurized dairy products
Brucella respiration
Facultative intracellular - can survive and multiply within macrophages by preventing phagolysosome fusion
Brucelosis (Brucella infection) symptoms
Nonspecific: Fever, chills, anorexia
In some patients the fever rises and falls - Undulating fever
Its ability to survive in macrophages means it is great at traveling to multiple systems through the reticuloendothelial system.
You can see enlargement of spleen, liver, lymph nodes
Osteomyelitis in chronic infection
Brucelosis Tx
Tetracyclines like Doxycycline PLUS Rifampin
Rifampin is used as adjunctive therapy NOT prophylaxis
What does Francisella look like?
Coccobacilli
What is the main reservoir for Francisella?
Rabbits
Humans get sick from direct contact with rabbits (handling/eating them) or indirect contact through a tick vector (dermacentor tick)
What zoonotic bacterial infection must be reported to CDC?
Francisella
It can be aerosolized and used in weapons. All cases must be reported.
What disease does Francisella cause?
Tuleremia
Francisella respiration
Facultative intracellular - recovery depends on cell-mediated immunity
Also helps facilitate spread throughout body
Tuleremia course
Caused by Francisella
Bacteria enter site of dermacentor tick bite causing painful ulcer at site
Bacteria get into macrophages and travel through lymph system to reticuloendothelial organs like lymph nodes causing granulomas with caseating necrosis
Lymph nodes swell - regional lymphadenopathy
Can spread systemically to other nodes
Tuleremia Tx
Streptomycin (an aminoglycoside)
Where is pasteurella found?
Respiratory tract of small mammals like cats and dogs
Most common transmission = dog and cat bites
How do you grow pasteurella on agar?
5% sheep blood agar
What does pasteurella look like?
Demonstrates “safety pin” staining - bipolar staining. Take up the most stain at its 2 ends
Like Yersenia
Pasteurella infection presentation
Cellulitis may occur in first 24 hrs
Soft tissue infection may spread to bone to cause osteomyelitis
Can also cause lymphadenopathy and spread systemically
The systemic spread usually only occurs in people with predisposing conditions like liver disease or COPD
Also, it’s encapsulated
Pasteurella infection Tx
Penicillin
You may want to also use a B-lactamase inhibitor to prevent resistance
Good combo would be amoxycillin + clavulanic acid
