Cat-Scratch Fever is caused by the bacterium Bartonella henselae, which is transmitted via a…cat…scratch, but it can also be transmitted when a cat gives you sweet keke kissses, and rarely transmitted through a tick or flea bite.
Therefore, this is mostly associated with people who have recently adopted a kitten and often associated with children, because they’re more likely to get scratched by said new kitten.
A patient is going to present with Cat-Scratch Fever with 2 weeks after the scratch occurs. It will cause the formation of papules at the inoculation site, which is usually the hand because cats have a love/hate relationship with getting pet. The draining lymph nodes will become severely swollen, not at a bubo level but definitely swollen. It might also accompany fever, muscle aches, and fatigue.
This organism loves to infect endothelial cells and macrophages. If it spreads from the site of the scratch, it can cause problems in other organs that are very vascularized like the heart, liver, or spleen and It can cause endocarditis if it spreads to the heart.
If it spreads to the skin in patients with AIDS, it can cause bacillary angiomatosis, which is when the bacteria forces the endothelial cells to proliferate causing the formation of hyperpigmented or flesh-colored benign tumors. These are going to mimic Kaposi Sarcoma, which also occurs in this patient population, so it’s important to do a biopsy to explore the cause of the formation. Bacillary angiomatosis will have a neutrophilic infiltration because it’s caused by the presence of a bacterium, whereas masses caused by Kaposi Sarcoma will have lymphocytic infiltrates.
If the bacterium spreads to the liver it can cause Bacillary Peliosis, which is the hyperproliferation of the capillaries in the liver. This will cause the formation of large cysts filled with blood. This can be fatal if not treated appropriately.
It has been associated with Reactive Arthritis causing uveitis, urethritis, and arthritis after the organism has been completely cleared, so it’s important to follow up with these patients.
To diagnose Cat-Scratch Fever, it’s best to use serologic testing to test for anti-Bartonella henselae antibodies. This is because the organism is fastidious and hard to culture, and it’s hard to stain, forcing you to use Warthin-Starry staining to visualize the organism.
Cat-Scratch fever is usually self-limited and will resolve in 1-4 months, it’s not clear whether utilizing azithromycin actually speeds up resolution or not. However, if it’s not cat-scratch fever you definitely need to treat with antibiotics and which one will depend on the location of the infection.
Brucella spp. organisms are very common in livestock and wildlife animals. It is transmitted to humans through the consumption of contaminated dairy products, especially unpasteurized milk and goat’s milk. It can also be transmitted by direct contact with the animals and inhalation of their droppings.
Once transmitted, this organism will infect macrophages which help to disseminate the organism throughout the body. Brucellosis is characterized by irregular waves of fever and resolution which is where the name undulating fever comes from. Symptoms that typically accompany this are weakness, muscle aches, chills, arthritis, lymphadenopathy, and often drenching night sweats with a particularly moldly odor.
Brucella spp. can disseminate into basically any organ in the body causing the formation of granulomas or abscesses.
To diagnose, culturing can be preformed, but this organism is particularly fastidious and is slow-growing so most physicians prefer serologic testing.
Brucella spp. should be treated with doxycyline because that antibiotic is very good against intracellular organisms.
A 38-year-old male presents with new-onset skin lesion for the last six days. Vital signs are significant for a temperature of 100F. Past medical history is significant for a 5-year history of untreated HIV infection. One week earlier the patient was scratched by his cat, the next day the lesion began to form,and has since slowly increased in size. Physical examination revealed a single, erythematous papule on his right knee located very close to the site of the scratch. Right inguinal lymphadenopathy is also present. If this remains untreated, what potential complication could occur in this patient?
A. Squamous cell carcinoma
B. Bacillary angiomatosis
C. Myonecrosis
D. Severe scarring
First, diagnose the patient.
The patient is presenting with a single red lesion, and draining lymphadenopathy that formed soon after a scratch from a cat. This is highly suggestive of Cat-Scratch Fever.
- Recent exposure to a feline via scratch, bite, or saliva
- Formation of a single or few erythematous papules that might be pus-filled near the site of the scratch
- Swelling of the draining lymph node
- Might present with fever, muscle aches, and fatigue
- Caused by Bartonella spp. bacteria, particularly Bartonella henselae
A. Bartonella henselae is not associated with the formation of any cancerous growths.
B. Bacillary angiomatosis is the formation of violaceous skin masses due to the dissemination of Bartonella henselae. This bacterium infects the endothelial cells triggering proliferation and wound healing which can force a hyperproliferative state forming bacillary angiomatosis. This is not a cancerous growth, and can be completely resolved with antibiotic treatment.
C. Bartonella henselae is not associate with myonecrosis even in severe infections. Myonecrosis is the a severely destructive muscle infection that is often necrotic.
D. Bartonella henselae as Cat-Scratch Fever is self-limiting and usually heals completely within 1-4 months, it’s not clear if antibiotic treatment speeds this up or not. However, there is not scarring involved in this healing process. Even if it causes Bacillary Angiomatosis, once the lesions heal, there is no scarring involved.
Therefore,
A 29-year-old female presented with anemia, hypotention, and an unintended weight loss of 9 lbs. over the course of 1 month. Past medical history revealed that one month ago she present to the clinic with intermittent fever, anorexia, profuse sweating, malaise, headache, neck and shoulder pain, and arthralgia for the past three days. An influenza infection was suspected, and she returned home. A current physical examination revealed hepatosplenomegaly with pain. Laboratory studies reveal neutropenia and lymphocytosis. She works as a laboratory technician and handles goats infected with Brucella melitensis. What is the most appropriate treatment?
A. Azithromycin
B. Penicillin
C. Doxycyline
D. Metronidazole
Luckily, we have a clue to this infectious agent. She has potentially been exposed to Brucella spp. through her job as a scientist. The next step is to see if her symptoms are characteristic for: Brucellosis.
- Variable fever, weakness, aches, chills, arthritis, night sweats, malaise
- Exposure to unpasteurized dairy products or handling animals especially cows and goats
The sign of hepatosplenomegaly is probably due to the organism taking residence in those organs and replicating.
The neutropenia is a sign of a chronic, unresolved bacterial infection. The lymphocytosis is most likely the body trying to compensate for the loss of the neutrophils.
A. Azithromycin is a macrolide that is commonly used for Chlamydia trachomatis, atypical pneumonia, and respiratory infections (pneumoia, strept throat, middle ear infections, rhinosinusitis). This antibiotic binds to bacterial ribosomal subunits and inhibits protein translation.
B. Penicillin is best against Gram-positive organisms and spirochete bacteria. Since Brucella spp. are Gram-negative this is not the best choice. This works by stopping the cross-linking of peptidoglycan. Gram-positive organisms have a very thin layer of peptidoglycan making them more susceptible to lysing if those few layers are disturbed.
C. Doxycycline is particularly good against intracellular organisms, and since Brucella spp. prefer to be intracellular, this antibiotic is preferred. Doxycyline works by binding to bacterial ribosomes and inhibiting protein translation causing the death of the cell.
D. Metronidazole is typically used for anaerobic bacteria and protozoa organisms. This forms free radical species which damage DNA causing the death of the cell.
Therefore,
References:
https://wwwnc.cdc.gov/eid/article/16/12/10-0647_article
https://microbewiki.kenyon.edu/index.php/Bartonella_henselae
https://microbewiki.kenyon.edu/index.php/Brucella
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4032053/pdf/apjtd-04-02-150.pdf
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