Module 5.8 Miscellaneous Gram-negative Aerobic Rods Flashcards
Describe the Brucella species.
- small, gram negative coccobacilli
- acid-fast staining
- facultative anaerobes
- capnophilic (thrive in presence of CO2)
- nutritionally fastidious
- host-specificity
- facultative intracellular
- target reproductive organs
Which Brucella species are zoonotic?
- Brucella abortis
- Brucella melitensis
- Brucella suis
- Brucella canis
How does zoonotic transmission of Brucella occur?
- ingestion
- breaks in skin
- airborne infection (labs and abattoirs)
- consumers of raw milk, farmers, butchers, veterinarians and lab personnel
Brucella abortus 2-OBL-Z-R
- 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
What are the major disease sequelae of brucella abortus in cows?
- 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
How do we test for Brucella abortis?
- 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
Brucella suis 2-OBL-Z-R
- biovars 1-3 with domestic/wild swine
- biovar 4 with reindeer and caribou
- part of CFIA serological screening at slaughter facilities
What clinical signs does Brucella suis cause?
- chronic inflammation of the reproductive tracts of sows and boars
- stillbirths
- neonatal mortality
- temporary sterility
How do we diagnose Brucella suis?
- Rose-Bengal plate agglutination (serology)
- ELISA (serology)
- culture/PCR
Brucella canis 3-OBL-Z
- very common in countries with free roaming dogs
- transmission to people is rare
What diseases does Brucella canis cause?
- chronic, persistent reticuloendothelial infection
- bacteremia
- vertebral osteomyelitis
- abortion late pregnancy; epididymitis, orchitis
How do we diagnose Brucella canis?
- usually serology
- rapid slide agglutination
- confirmed by ELISA
- Agar gel immunodiffusion assay
- culture/PCR of blood, semen, discharges
How do we treat Brucella canis?
- long term treatment with tetracycline and aminoglycosides
Brucella ovis 4-OBL
- present in most sheep raising countries
- epididymitis (usually unilateral), infrequent abortions, increased perinatal lamb mortality
- genital lesions in rams, placentitis in ewes
How do we diagnose Brucella ovis?
- 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
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?
Pdeudomonas aeruginosa
Pseudimonas aeruginosa 1-OPP
- 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
What are some virulence factors of Pseudomonas aeruginosa?
Alginate (slime), elastases, hyaluronidases, collagenases, haemolysis, exotoxin
How is Pseudomonas aeruginosa killed?
Killed by neutrophils and therefore they occur in neutropenic, immunocompromised patients
How do we diagnose Pseudomonas aeruginosa?
- culture (fruity smell)
- it is resistant to many antibiotics and disinfectants
- ESKAPE Group
antimicrobial susceptibility testing is recommended - no vaccines except mink
How does Pseudomonsa aeruginosa present in dogs, horses, sheep and mink?
- Dogs: otitis externa (one of the leading causes, think green slimy discharge)
- Mink: Hemorrhagic pneumonia
- Horses: corneal ulcers
- Sheep: Fleece rot (usually green)
Moraxella bovis 2-PR
- usually seen in pairs
- agent of infectious bovine keratoconjunctivitis (IBK pink eye)
- will eventually cause blindness which is a significant economic loss
How is Moraxella bovis transmitted?
- animals carry bacterium in conjunctiva
- organism is host-adapted
- spread by flies via direct contact
What are the virulence factors of Moraxella bovis?
- RTX hemolysis
- fibrinolysin
- hyaluronidase: efficient system for adhesive pilus antigenic variation
How do we control and treat Moraxella bovis?
- 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
Bartonella species characteristics:
- 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
Bartonella henselae 2-OPP-Z
- 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
How do we control and treat Bartonella henselae?
- 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
Acinetobacter baumannii 3-OPP
- commensal, environmental organism
- low grade opportunistic pathogen
- naturally resistant to most antimicrobials - ESKAPE
- important nosocomial pathogen (originating in hospital)
Capnocytophaga canimorsus 4-OPP-Z
- 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
What causes pink eye disease and what is its clinical signs?
- Moraxella bovis
- sensitivity to light, darkening below the eye, corneal opacity and uneven surface
What is the main cause of hemorrhagic pneumonia in mink?
Pseudomonas aeruginosa
List the Pdeudomonas aeruginosa diseases in different species
- Dogs: otitis externa
- Horses: corneal ulcers
- Cattle: nosocomial mastitis
- Mink: hemorrhagic pneumonia
- Sheep: fleece rot
- Humans: corneal ulcers, burn infections, cystic fibrosis
