Module 5.8 Miscellaneous Gram-negative Aerobic Rods

Question 1

Describe the Brucella species.

Answer 1

• small, gram negative coccobacilli
• acid-fast staining
• facultative anaerobes
• capnophilic (thrive in presence of CO2)
• nutritionally fastidious
• host-specificity
• facultative intracellular
• target reproductive organs

Question 2

Which Brucella species are zoonotic?

Answer 2

• Brucella abortis
• Brucella melitensis
• Brucella suis
• Brucella canis

Question 3

How does zoonotic transmission of Brucella occur?

Answer 3

• ingestion
• breaks in skin
• airborne infection (labs and abattoirs)
• consumers of raw milk, farmers, butchers, veterinarians and lab personnel

Question 4

Brucella abortus 2-OBL-Z-R

Answer 4

• obligate pathogen of cattle
• eradicated in Canada except Wood Buffalo National Park
• non-motile
• non-capsulated
• non-spore former
• survives in the environment for months but doesn’t grow
• infection occurs via ingestion or through nasal and oral mucosae
• can invade epithelial cells allowing mucosal invasion and M cells in intestine
• migrates via macrophages and multiplies in placenta causing placentitis

Question 5

What are the major disease sequelae of brucella abortus in cows?

Answer 5

• contagious abortions
• cows will abort once or twice and then after that they will not abort but shed the pathogen at parturition
• causes epididymitis and orchitis in bulls leading to sterility

Question 6

How do we test for Brucella abortis?

Answer 6

• federal test and slaughter program in Canada
• rapid buffered plate test (cheap, not very specific)
  CFIA runs Bovine Surveillance System
• if there is a positive serologic test you investigate the whole herd

Question 7

Brucella suis 2-OBL-Z-R

Answer 7

• biovars 1-3 with domestic/wild swine
• biovar 4 with reindeer and caribou
• part of CFIA serological screening at slaughter facilities

Question 8

What clinical signs does Brucella suis cause?

Answer 8

• chronic inflammation of the reproductive tracts of sows and boars
• stillbirths
• neonatal mortality
• temporary sterility

Question 9

How do we diagnose Brucella suis?

Answer 9

• Rose-Bengal plate agglutination (serology)
• ELISA (serology)
• culture/PCR

Question 10

Brucella canis 3-OBL-Z

Answer 10

• very common in countries with free roaming dogs
• transmission to people is rare

Question 11

What diseases does Brucella canis cause?

Answer 11

• chronic, persistent reticuloendothelial infection
• bacteremia
• vertebral osteomyelitis
• abortion late pregnancy; epididymitis, orchitis

Question 12

How do we diagnose Brucella canis?

Answer 12

• usually serology
• rapid slide agglutination
• confirmed by ELISA
• Agar gel immunodiffusion assay
• culture/PCR of blood, semen, discharges

Question 13

How do we treat Brucella canis?

Answer 13

• long term treatment with tetracycline and aminoglycosides

Question 14

Brucella ovis 4-OBL

Answer 14

• present in most sheep raising countries
• epididymitis (usually unilateral), infrequent abortions, increased perinatal lamb mortality
• genital lesions in rams, placentitis in ewes

Question 15

How do we diagnose Brucella ovis?

Answer 15

• bacteriological isolation of B.ovis from semes, vaginal discharges, milk of ewes on a selective media
• indirect diagnosis based on serological tests
• serological tests: complement fixation test (CFT), agar gel immunodiffusion (AGID), test and enzyme linked immunosorbent assay (ELISA), soluble surface antigens

Question 16

Case Report:
- 2 yo, MN, DSH got in dishwasher
- after running away, his burns two days later were very inflamed, infected, smelled sweet, greenish tinge
- culture was done and had green colonies
- lab report showed mixed flora
What bacteria was likely in his wounds?

Answer 16

Pdeudomonas aeruginosa

Question 17

Pseudimonas aeruginosa 1-OPP

Answer 17

• gram-negative
• strict aerobe
• usually superficial, rarely systemic
• metabolically versatile
• ubiquitous in water and soil
• opportunistic pathogen with broad host range - specifically immunocompromised hosts and burn patients

Question 18

What are some virulence factors of Pseudomonas aeruginosa?

Answer 18

Alginate (slime), elastases, hyaluronidases, collagenases, haemolysis, exotoxin

Question 19

How is Pseudomonas aeruginosa killed?

Answer 19

Killed by neutrophils and therefore they occur in neutropenic, immunocompromised patients

Question 20

How do we diagnose Pseudomonas aeruginosa?

Answer 20

• culture (fruity smell)
• it is resistant to many antibiotics and disinfectants
• ESKAPE Group
  antimicrobial susceptibility testing is recommended
• no vaccines except mink

Question 21

How does Pseudomonsa aeruginosa present in dogs, horses, sheep and mink?

Answer 21

• Dogs: otitis externa (one of the leading causes, think green slimy discharge)
• Mink: Hemorrhagic pneumonia
• Horses: corneal ulcers
• Sheep: Fleece rot (usually green)

Question 22

Moraxella bovis 2-PR

Answer 22

• usually seen in pairs
• agent of infectious bovine keratoconjunctivitis (IBK pink eye)
• will eventually cause blindness which is a significant economic loss

Question 23

How is Moraxella bovis transmitted?

Answer 23

• animals carry bacterium in conjunctiva
• organism is host-adapted
• spread by flies via direct contact

Question 24

What are the virulence factors of Moraxella bovis?

Answer 24

• RTX hemolysis
• fibrinolysin
• hyaluronidase: efficient system for adhesive pilus antigenic variation

Question 25

How do we control and treat Moraxella bovis?

Answer 25

- early diagnosis - fly control with insecticide impregnated ear tags - prevent predisposing factors like cutting tall grasses, preventing viral infections, avoid dusts and ammonia - treat with topical antibiotics, aminoglycosides, beta lactams, macrolides, tetracyclines - no efficient vaccines to date

Question 26

Bartonella species characteristics:

Answer 26

- gram negative, aerobic, coccobacilli - difficult to culture (long) - virulence is poorly understood, type IV secretion system - intracellular - persistent, usually subclinical, bacteremia in hosts - vector transmitted: fleas and ticks

Question 27

Bartonella henselae 2-OPP-Z

Answer 27

- spread between cats by fleas - common in feral cats - asymptomatic bacterial infections in cats - may be present in RBC and/or endothelial cells - causative agent of cat scratch fever in humans

Question 28

How do we control and treat Bartonella henselae?

Answer 28

- sensitive to antibiotics that penetrate host cells like tetracyclines and fluoroquinolones - response is poor though so we use aggressive antibiotic treatment for immunocompromised individuals - treatment in infected cats will recur

Question 29

Acinetobacter baumannii 3-OPP

Answer 29

- commensal, environmental organism - low grade opportunistic pathogen - naturally resistant to most antimicrobials - ESKAPE - important nosocomial pathogen (originating in hospital)

Question 30

Capnocytophaga canimorsus 4-OPP-Z

Answer 30

- capnophilic - fastidious, slow-growing - gram negative rod - normal oral flora in dogs and cats - can cause septicemia and meningitis in humans following a bite - usually not a problem in healthy adults - predisposing factors: alcoholism, splenectomy, cytotoxic cancer treatments - diagnosis is difficult but done via PCR - long term treatment with Penicillin G

Question 31

What causes pink eye disease and what is its clinical signs?

Answer 31

- Moraxella bovis - sensitivity to light, darkening below the eye, corneal opacity and uneven surface

Question 32

What is the main cause of hemorrhagic pneumonia in mink?

Answer 32

Pseudomonas aeruginosa

Question 33

List the Pdeudomonas aeruginosa diseases in different species

Answer 33

- Dogs: otitis externa - Horses: corneal ulcers - Cattle: nosocomial mastitis - Mink: hemorrhagic pneumonia - Sheep: fleece rot - Humans: corneal ulcers, burn infections, cystic fibrosis