Pasteurella multocida

Q. 1

A mailman gets a severe bite wound from a dog guarding a junkyard. The wound is cleansed and he receives a booster injection of tetanus toxoid and an injection of penicillin G. Several days later, the wound is inflamed and purulent. The exudate is cultured on blood agar and yields gram-negative rods. Antibiotic sensitivity tests are pending. The most likely agent to be isolated is?

A		Bartonella henselae
B		Brucella canis
C		Clostridium tetani
D		Pasteurella multocida

Q. 1

A		Bartonella henselae
B		Brucella canis
C		Clostridium tetani
D		Pasteurella multocida

Ans. D

Explanation:

Pasteurella multocida is a gram-negative rod that is normal flora of the oral cavity of dogs and cats. It often causes a local abscess following introduction under the skin by an animal bite. Most cases occur in children who are injured while playing with a pet.

Bartonella henselae is a very small, gram-negative bacterium that is closely related to the rickettsia, although it is able to grow on lifeless media.

It is the cause of cat-scratch disease (a local, chronic lymphadenitis most commonly seen in children) and bacillary angiomatosis (seen particularly in AIDS patients).

In this latter patient population, the organism causes proliferation of blood and lymphatic vessels causing a characteristic “mulberry” lesion in the skin and subcutaneous tissues of the afflicted individual.

Brucella canis is a gram-negative rod that is a zoonotic agent. Its normal host is the dog, but when it gains access to humans, it causes an undulating febrile disease with malaise, lymphadenopathy and hepatosplenomegaly. The normal route of exposure is via ingestion of the organism.

Clostridium tetani is a gram-positive spore-forming anaerobic rod. It causes tetanus (a spastic paralysis caused by tetanospasmin, which blocks the release of the inhibitory neurotransmitters glycine and gamma-aminobutyric acid [GABA]). There may be no lesion at the site of inoculation, and exudation would be extremely rare.

Ref: Ray C.G., Ryan K.J. (2010). Chapter 36. Plague and Other Bacterial Zoonotic Diseases. In C.G. Ray, K.J. Ryan (Eds), Sherris Medical Microbiology, 5e.

Q. 2

While playing in the park, an 8-year-old girl is bitten in the leg by a neighbor’s cat. She presents the next day with fever and bone pain localized to her right calf. X-ray reveals a lytic lesion of the right tibia. Results of the bone culture are pending. You expect the infecting organism to be ?

A		Brucella melitensis
B		Eikenella corrodens
C		Francisella tularensis
D		Pasteurella multocida

Q. 2

A		Brucella melitensis
B		Eikenella corrodens
C		Francisella tularensis
D		Pasteurella multocida

Ans. D

Explanation:

This patient has osteomyelitis due to a cat bite that penetrated the periosteum.

Whenever you see dog or cat bites in a question stem, consider Pasteurella multocida as a primary cause of wound infection.

This organism is a short, encapsulated, gram-negative rod demonstrating bipolar staining.

Rapidly arising cellulitis is particularly indicative of this organism.

Brucella melitensis is a small, acapsular, gram-negative rod that causes brucellosis (undulant fever) and is associated with contact with goats or sheep.

Brucella abortus and Brucella suis are variants associated with contact with cows and pigs, respectively.

The organisms enter the body through the skin or through contaminated dairy products, such as unpasteurized imported goat’s milk or cheeses.

Eikenella corrodens is commonly found in human bites. It is a gram-negative rod that is part of the normal flora of the human mouth.

Francisella tularensis is a small, pleomorphic, gram-negative rod that causes tularemia (rabbit fever). It occurs most commonly in rural areas.

Ref: Ray C.G., Ryan K.J. (2010). Chapter 36. Plague and Other Bacterial Zoonotic Diseases. In C.G. Ray, K.J. Ryan (Eds), Sherris Medical Microbiology, 5e.

Q. 3

A 35 year old man comes to the clinic with a skin lesion following a cat bite 1 day back. On examination he was found to have cellulitis of the affected area. Which of the following is the most likely causative organism?

A		F.tularensis
B		Pasteurella multocida
C		Capnocytophaga canimorsus
D		Bartonella henselae

Q. 3

A		F.tularensis
B		Pasteurella multocida
C		Capnocytophaga canimorsus
D		Bartonella henselae

Ans. B

Explanation:

Pasteurella multocida is the common cause of cutaneous infection following cat or dog bite. Pasteurella multocida is a bipolar-staining, gram-negative coccobacillus that colonizes the respiratory and gastrointestinal tracts of domestic animals. Within 24hrs of bite patients develop cellulitis and bacteremia.

Pasteurella multocida is sensitive to amoxicillin, penicillin, amoxicillin-clavulanate, tetracyclines and fluoroquinolones.

Ref: Barlam T.F., Kasper D.L. (2012). Chapter 146. Infections Due to the HACEK Group and Miscellaneous Gram-Negative Bacteria. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison’s Principles of Internal Medicine, 18e.

Q. 4

Appendicitis like syndrome is caused by all except‑

A		Yersinia enterocolitica
B		Yersinia pseudotuberculosis
C		Pasteurella septica
D		Yersenia pestis

Q. 4

Appendicitis like syndrome is caused by all except‑

A		Yersinia enterocolitica
B		Yersinia pseudotuberculosis
C		Pasteurella septica
D		Yersenia pestis

Ans. D

Explanation:

Ans. is ‘d’ i.e., Yersinia pestis

Pasteurella multocida (Pasteurella septical

. The bacillus is often carried in the upper respiratory tract of a variety of animals such as dogs, cats, rats, cattle and sheep.

. It may sometimes occur as a commensal in human respiratory tract also.

. Human infection is rare but may occur following animal bites or trauma.

. Clinical manifestations

– Wound infection – Abscess – Pneumonia – Meningitis

– Cellulitis – Osteomyelitis – Sinusitis – Appendicitis

Yersinia pseudotuberculosis

. he bacillus resembles the plague bacillus (Y.pestis) but can be distinguished by presence of motility at 22°C (but not at 37°C).

. It causes pseudotuberculosis in animals.

. Human infection is rare and may present as typhoid like illness or mesentric lymphadenitis simulating appendicitis. Yersinia enterocolitica

. This bacillus resembles Y. pseudotuburculosis in being motile at 22°C.

. It causes gasteroenteritis or mesentric adenitis & terminal ileitis that may mimic appendicitis or systemic disease (bacteremia, meningitis).

Q. 5

Most common mode of transmission of Pasturella multocida is –

A		Animal bites or scratches
B		Aerosols or dust
C		Contaminated tissue
D		Human to human

Q. 5

Most common mode of transmission of Pasturella multocida is –

A		Animal bites or scratches
B		Aerosols or dust
C		Contaminated tissue
D		Human to human

Ans. A

Explanation:

Ans. is ‘a’ i.e., Animal bites or scratches

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Pasteurella multocida