Microbiology-Bites

Question 1

Most common cause of animal bites

Answer 1

Dogs

Question 2

Animal bites with higher risk of infection than dog bites

Answer 2

Cats, deeper penetration w/deeper infection and osteomyelitis

Question 3

Common microbial infections associated with cat and dog bites

Answer 3

Pasteurella, capnocytophagia, normal skin flora and anaerobes

Question 4

What people are at higher risk for infection by capnocytophagia after a dog/cat bite? What symptoms are common? How do you treat?

Answer 4

Immunocompromised. Presents with fever, muscle aches and rare sepsis. Tx with augmentin, avoid bactrim and aminoglycosides.

Question 5

Symptoms that commonly present with pasteurella infection after a cat/dog bite? How do you treat?

Answer 5

Fever, cellulitis, arthritis, pneumonia, endocarditis, meningitis 15 hours after bite. Tx with augmentin or azithromycin. Avoid erythromycin and clindamycin.

Question 6

More common microbe involved in community acquired MRSA from animals

Answer 6

S. intermedius > S. aureus.

Question 7

Indications for antibiotic prophylaxis after bits

Answer 7

Deep bites (cats), crush injuries, venous/lymphatic compromise, wounds close to bone, wounds that requires surgical care, immunocompromised. Drug of choice = augmentin.

Question 8

28 year old pregnant woman presents with a red and swollen cat bite. She has a penicillin allergy. What is appropriate empiric therapy?

Answer 8

Axithromycin

Question 9

Cat-scratch disease

Answer 9

Bartonella henselae (mostly in fall/winter in outdoor cats and affects younger kids)

Question 10

Cat scratch symptoms

Answer 10

Papule/pustule at site of infection, fever, enlarged lymph nodes 1-3 weeks after exposure.

Question 11

Diagnosing and treating cat-scratch disease.

Answer 11

Dx clinically most of the time, can also use serology or PCR. Tx with azithromycin if symptoms do not resolve spontaneously (they usually do).

Question 12

Common pathogens associated with human bites

Answer 12

Staph, strep, eikenella (facultative). Also worry about HSV, HIV, HepC and HepB.

Question 13

A 52 year old man suffers a hand injury in a brawl from punching a guy in the face. He has bony fragments on x-ray. He was given cephalexin in the ER and sent home. 5 days later he returns tachycardic, hypotensive, feverish and confused. His hand is warm, edematous, painful to move and has decreased sensation. He was given Tdap shot, started on amp-sulbactam and has a fasciotomy for compartment syndrome. Gram stain shows an anaerobic gram negative bacilli. How do you treat him?

Answer 13

Eikenella corrodens is a common infection in human “bites”. It is resistant to cephalexin, clindamycin, erythromycin and metronidazole. Tx with augmentin, fluoroquinolones, TMP-SMX or doxycycline.

Question 14

Common pathogens in pig bites? How do you treat them?

Answer 14

Strep, staph, pasteurella, actinobacillus, tx with augmentin + ciprofloxacin to cover actinobacillus.

Question 15

Symptoms and pathogens associated with rat-bite fever?

Answer 15

Streptobacillus moniliformis (US, branching gram-negative bacillus shown below), spirillum minus (asia). Symptoms: fever, pustular rash (shown below), migratory polyarthritis and endocarditis. Tx with augmentin or doxycycline.

Question 16

Pathogen associated with seal finger? Symptoms? Treatment?

Answer 16

Mycoplasma. Papular lesion with pain, swelling and joint involvement. Tx with tetracycline.

Question 17

Pathogens associated with the candiru fish (cat fish in amazon river attracted to urea)?

Answer 17

They swim up your urethra and lodge there to get urea waste.

Question 18

Bacterial infections associated with snake bites

Answer 18

Secondary flora wounds are rare because venom is sterile.

Question 19

Things to not do when bit by a snake? What should you do?

Answer 19

Suck out the venom, apply a tourniquet, place ice packs. You should give anti-venom, first aid and ceftriaxone + clavulanate empirically.

Question 20

Pathogens associated with monkey bites

Answer 20

Staph, strep, eikenella, Herpes B virus

Question 21

Symptoms associated with herpes B virus after a monkey bite?

Answer 21

Reactivation, vesicular lesions, paresthesias, seizures, respiratory failure. (80% fatality rate)

Question 22

Tx for person exposed to herpes B virus after a monkey bite

Answer 22

Prophylactic acyclovir if pregnant, valacyclovir for others (can be life-long). IV if CNS involved.

Question 23

3 phases of rabies

Answer 23

1) Flu-like illness, prickling at bite site 2) Agitation, delirium 3) Coma death

Question 24

Diagnosing rabies

Answer 24

1) Salive PCR 2) Neck biopsy (nerves) 3) Serum immunoassay 4) CSF immunoassay

Question 25

Animal bites that merit immediate rabies prophylaxis

Answer 25

Skunks, raccoons, foxes and bats. Give RIG if not previously vaccinated. Revaccinate if previously vaccinated, don’t give RIG if previously vaccinated.

Question 26

Path of infection by clostridium tetani?

Answer 26

Spores enter wound, germinate and make toxin that causes muscular spasms and seizures.

Question 27

Tx for tetanus

Answer 27

TIG, toxoid booster, antibiotics (penicillins or metronidazole). Give prophylaxis TIG and toxoid vaccine if immunization hx is unclear. Don’t give TIG if immunizations are clear and current.