17 – Pseudomonas and Non-Fermenters Flashcards
Microbial characteristics
- Biocontainment levels 1-3
- Gram negative rods to cocco-bacillus
- *famous for intrinsic drug resistance
P. aeruginosa on blood agar
- Characteristic smell=fruity/floral (grapes)
- Wet-corn tortilla
- *metallic sheen
P. aeruginosa on Mueller-Hinton agar
- Blue-green pigments
Stenotrophomonas maltophila on blood agar
- Foul smelling, ammonia-like odour
Non-fermenters: natural host or habitat
- Widely disseminated in environment
- Aquatic and marine environments
Pseudomonas aeruginosa: natural host or habitat
- Happily survives on surfaces in HOSPITAL environment
Burkolderia mallei: natural host or habitat
- Host adapted pathogen to equids
- Does NOT survive OUTSIDE the host
Burkholderia pseudomallel: natural host or habitat
- Found in water and soil of equatorial regions
Virulence factors of pseudomonas aeruginosa
- Ability to quorum sense
- Elastase (damage to blood vessels and lung tissues)
- Siderophores
- Type III secretion system (release effector to damage host tissues)
- Alginate biofilm
Siderophores
- Pigmented iron scavenging molecules pyoverdine (green), pyocyanin (blue)
- *characteristic colour
Alginate biofilm
- Slimy matrix produced by strains which prevents phagocytosis
Biofilm definition
- Collection of microbial cells covered by and embedded in a matrix of extracellular matrix which protects the bacteria inside
P. aeruginosa: clinical significance
- Opportunistic pathogen: rarely causes primary infection
- Can infect many species at a variety of anatomical sites
What are some presentations associated with the P. aeruginosa
- Pneumonia in farmed mink and pigs
- Otitis, pneumonia, sepsis, sudden death in chinchillas
- Sepsis in poultry
- Mastitis in ruminants
- Otitis externa in dogs
P. aeruginosa in horses and dogs: isolated from comprised animals (otitis externa and pyoderma)
- Infecting corneal tissues
o Ulcerative keratitis
o Cause of ‘melting ulcers’ in horses
o GREEN colour due to fluorescein DYE
P. aeruginosa (humans)
- Most commonly isolated P. species in humans
- In patents have other ‘issues’
- Infections often occur at ‘moist’ site
- Treatment is often difficult (intrinsic and acquired resistance and formation of biofilms)
Humans who get P. aeruginosa: other ‘issues’ they have
- Burns
- Cystic fibrosis
- Acute leukemia
- Transplant recipients
P. fluorescens (fish)
- Cause of septicemia in high intensity aquaculture operations
o Fish lethargic and have cutaneous lesions - Ubiquitous within environment
- More common in waters with organic pollutants
- Treatment is challenging (intrinsic resistance, drugs available=not effective)
S. maltophila (repitles)
- Septicemia in reptiles and amphibians
o Wounded animals, poor husbandry (kept too cold) - *if have systemic infections in reptiles=THINK NON-FERMENTERS
Cutaneous infection in reptiles: most common isolate
- P. aeruginosa
Abscess in reptiles: most common isolate
- Mixed anaerobes
Respiratory infection in reptiles: most common isolate
- P. aeruingosa
Oral infection in reptiles: most common isolate
- P. species
- Stenotrophomonas maltophila
Burkholderia mallei (glanders in horses)
- Humans and cats also susceptible
- Transmission by ingestion of food or water contaminated by nasal discharges
- Facultative intracellular parasite
Burkohodleria mallei: 3 forms it presents itself
- Glanders: pulmonary
- Glanders: nasal
- Farcy: cutaneous
Glands in horses (Burkoholderia mallei): disease
- Pyrexia, depression and anorexia
- Watery discharge from nostril (unilateral) and coughing
- Nodules and ulcers develop on septum and discharge becomes thicker
- Enlargement of lymph nodes
- *animals that survive=nasal septum may be perforated
Burkholderia mallei (Farcy in horses)
- Cutaneous lesions
o Nodules on inner thighs, limbs and belly - Lymphangitis (swollen lymph vessels) and lymphadenitis
- Nodules which may ulcerate seen along tracks of lymphatics on skin
B. mallei in humans, large cats in zoos, horses
- Disease often fatal within several weeks
- Not found in NA (found in Asia, middle east, SA, Russia)
- *possible agent of biological warfare
B. pseudomallei (melioidosis in humans)
- Primarily found in Thailand, Vietnam, N. Australia, China, Taiwan and Laos
- ‘glanders like disease’
- Facultative intracellular pathogen
- Broad host range
- Contracted by contaminated food or water
Melioidosis contracted by contaminated food or water: examples
- Muddy water and humid soil
- Consumption of infected animals
- Exposure often occupational (labourers, cleaners, rice paddy workers)
B. pseudomallei (melioidosis in humans): survival and lesions
- Self-limiting flu like illnesses
- Typical lessions=abscesses (occur anywhere on body)
o People: lungs and brain=most common
o Infections can be latent and reactivate after years - High rates of infections in US soldiers in the Vietnam war
- *intrinsic resistance to many antimicrobials
Meliodosis in people has 3 distinct forms
- Acute: septicemia with metastatic lesions and abscesses
- Subacute: ‘TB” like pneumonia, lymphangitis
- Chronic: localized chronic cellulitis
Meliodosis in people if untreated
- High mortality rate (95%)
- *even high in developed countries among bacteremic patents=19%
B. pseudomallei (meliodosis in other species)
- Can be fatal or subclinical
- Horses: may mimic glanders
- Goats and pigs: respiratory and CNS infections, arthritis and mastitis (ex. splenic abscesses)
- Dogs: localized abscessations with pyrexia
- Monkeys: necrosuppurative meningoencephalitis
Sample collection: P. aeruginosa and S. maltophila
- Collect samples from infection sites
- *do NOT freeze
Sample collection: B. mallei
- *wear gloves
- Discharges from lesions for culture
- Blood for serology
- *do NOT freeze
Lab ID: pseudomonas and Stenotrophomonas
- Readily grows on routine test media
Lab ID: Burkholderia mallei and pseudomallei
- Grows on blood and MacConkey agar
- PCR based assays
- Immunological tests helpful
Lab ID: non-ferments (other than P. aerunginosa)
- Notoriously difficult to ID to speices level
o Even with MALDI
B. mallei: zoonotic and interspecies transmission
- Human infections=zoonotic
o Vets
o Those working with horses
o Lab workers
o Abattoir workers or those working with horse meat
B. pseudomallei: zoonotic and interspecies transmission
- Not typically transmitted between animals
- *Acquired from environment
Bergeyella zoohelcum: zoonotic and interspecies transmission
- Found in dog mouths
- *possibility in bite wounds
B. mallei: treatment choice
- Immediately notifiable in Canada
- *authorities take a stamping out approach
Pseudomonas and Stenotrophomonas: treatment choice
- Based on susceptibility testing
- May consider topical therapies in some situations
Drugs to avoid/intrinsic resistance
- *LOTS
- Due to level of porin expression (drugs can’t get through cell membrane!)
