Pasteurella multocida, Francisella tularensis and Bartonella

Question 1

General features and habitat of Pasteurella multocida

Answer 1

Gram –

Rod shape

Habitat- zoonosis; normal oral flora of mammals like cats (mostly), dogs and rabbits

Question 2

Biochemical Properties of Pasteurella multocida

Answer 2

Catalase +
Oxidase +

Capsule (Hyaluronic Acid)- virulence factor, helps to hide from the immune system

Facultative anaerobe

Question 3

Pathogenesis of Pasteurella multocida

Answer 3

Transmitted by a bite from dogs or cats (zoonotic infection)

In immunocompromised patients can be inhaled causing pneumonia or peritonitis

Question 4

Clinical Features of Pasteurella multocida

Answer 4

Cellulitis (seen as red swellings) and lymphadenitis within 24 hours of bite

Infection spreading into bones causing osteomyelitis and arthritis

Question 5

Diagnosis of Pasteurella multocida

Answer 5

Cultivation on Blood agar (5% sheep’s blood)

Bipolar staining- appear as “safety-pin” in microscope

Serotyping by agglutination (capsular antigen)

Question 6

Treatment of Pasteurella multocida

Answer 6

Penicillin (empiric treatment, often with beta-lactamase inhibitor)
Tetracycline or Macrolide

Question 7

General Features and habitat of Francisella tularensis

Answer 7

Gram – Coccobacillus

Habitat- zoonosis (mostly wild animals- especially in rabbits)

Question 8

Pathogenesis of Francisella tularensis

Answer 8

Rabbit are the main reservoir (other animals include deer and rodents)

Direct contact- skin contact with the animal (ulceroglandular form) or eating
undercooked rabbit’s meat (gastrointestinal form)

Indirect contact- Dermacentor ticks bite, inhalation of secretion (pneumonic
form) or inoculation in the eye (conjunctival / oculoglandular form)

Facultative intracellular- bacteria enter macrophages

No human-to-human transmission

Question 9

Clinical Features (Tularemia, “Rabbit Fever”) of Francisella tularensis

Answer 9

Ulceroglandular form:
When the tick bites, Franciella enters the wound causing painful ulcers at site of
infection

Through the ulcer site, the bacteria enter macrophage. Inside the macrophages,
they travel via the lymph system to resticuloendothelial organs (i.e. lymph
nodes) causing granuloma with necrotic caseating center

Can spread to other lymph nodes causing palpable regional lymphadenopathy

Gastrointestinal form- causes gastrointestinal infections

Pneumonic form- causes pneumonia

Conjunctival form- causes conjunctivitis

Question 10

Diagnosis of Francisella tularensis

Answer 10

Cultivation is not safe (biological weapon category A)

Francis medium- glucose, cysteine and rabbit’s blood at 37C (aerobic conditions) Colonies appear as small, round-shape with metallic blue color

Wright reaction (tube agglutination)- test specific antibodies in patient’s sera and establish their titer by serial dilutions of the antigen

BCYE medium- may be used also for francisella cultivation

Direct IF or PCR

Question 11

Treatment of Francisella tularensis

Answer 11

Aminoglycosides

Tetracycline, Fluoroquinolone, Chloramphenicol

Question 12

General Features and habitat of Bartonella henselae

Answer 12

Gram – Coccobacillus

Reservoir- zoonosis; cats (mostly) and dogs

Question 13

Pathogenesis of Bartonella henselae

Answer 13

Transmitted by scratches, bites and fleas’ bites

Question 14

Clinical Features of Bartonella henselae

Answer 14

Cat-Scratch Disease (Bartonellosis)- occurs in immunocompetent patients:
Lymphadenitis- swollen lymph nodes (especially in axillary lymph nodes)
Subacute endocarditis
Fever

Bacillary angiomatosis- in immunocompromised patients, such as HIV or AIDS:

Bacillary angiomatosis- raised red vascular lesions all over the body
Fever, chills, headache and weakness

Question 15

Diagnosis of Bartonella henselae

Answer 15

Warthin-Starry stain- type of silver staining

Question 16

Treatment of Bartonella henselae

Answer 16

Cat Scratch is self-limiting but if pain occurs- can use Erythromycin

Doxycycline (Tetracycline)

Macrolides

Question 17

Other Bartonella species

Answer 17

Bartonella quintana

Question 18

Clinical manifestation of Bartonella quintana

Answer 18

Trench fever (“quintana fever” or “five-day fever”)- headache, fever, weakness, pain in long bones.

Bacillary anginomatosis- vascular proliferative disease in immunocompromised patients.

Subacute endocarditis (requires blood culture for 3 weeks).