1. Pseudomonas, Aeromonas and Burkholderia species
Pseudomonadaceae
Pseudomonas, Aeromonas and Burkholderia species

2. Pseudomonas and Burkholderia
Gram negative rods
Obligate aerobes
Oxidise carbohydrates (not fermentative)
Oxidase, catalase positive
Motile by one or more flagellae (B. mallei non-motile)
Grow well on Maconkey agar
P. aeruginosa produces diffusible pigments (pyocyanin, pyoverdin)
P. aeruginosa is an opportunist pathogen
B. mallei causes glanders, B. pseudomallei causes melioidosis

3. Habitat
Pseudomonads are environmental organisms occurring worldwide in water, soil and vegetation
P. aeruginosa may be also found on skin, mucous membranes and in faeces
B. pseudomallei lives in soil where it may infect man and animals. Widely distributed in tropical and subtropical regions of southeast Asia and Australia
B. mallei may survive in the environment for up to 6 weeks but its reservoir is infected Equidae.

4. P. aeruginosa infections
Causes a wide range of opportunistic infections
Predisposing factors associated with many of these infections – defective or altered normal host defences
Bovine mastitis linked to contaminated water for udder washing or insertion of intra-mammary antibiotics
Fleece rot of sheep (associated with prolonged rainfall). Maceration of skin followed by water penetration of the fleece allows colonisation resulting in suppurative dermatitis. Pyocyanin pigment produced by P. aeruginosa discolours the wool

5. Diagnosis
Specimens for lab diagnosis include pus (green pus sometimes), respiratory aspirates, mastitic milk, etc
Blood agar and MacConkey inoculated and incubated at 37 degrees for hours.
Colonies are large, greyish-blue
Identified by colonial morphology and characteristic fruity odour (grape-like).
Pyocyanin production. Enhanced when grow on P. agar (also called DIFCO).
Non lactose fermenter on Maconkey agar
Oxidase positive
Shows multiple resistance to antibiotics
API 20E

7. MacConkey

8. Virulence factors of P. aeruginosa – survival in diverse environments and large number of virulence factors

10. Treatment
Predisposing causes and sources of infection identified and eliminated
P. aeruginosa very resistant to many antibiotics so lab susceptibility testing needs to be performed on isolates (aminoglycoside + anti-pseudomonal beta lactam usually effective)

11. Glanders Caused by Burkholderia mallei, Gram negative rod -
Rare - once worldwide but now in Middle East, India, Pakistan, China, Mongolia
Contagious disease of Equidae characterised by formation of nodules and ulcers in the respiratory tract and skin
Humans and carnivores also susceptible to infection – potential bioterrorism agent
Transmission by ingestion of food or water contaminated by nasal discharges of infected horses, also by inhalation or skin abrasions
Over horses were destroyed because of glanders during the First World War

12. Clinical features
Acute septicaemia with fever, mucopurulent nasal discharge and respiratory signs
Chronic disease more common presenting as nasal, pulmonary and cutaneous forms
Ulcerative nodules develop on the mucosa of the nasal turbinates and nasal septum
Purulent nasal discharge and regional lymphadenopathy present
Cutaneous form (Farcy) is a lymphangitis in which nodules occur along the lymphatic vessels of the limbs. Ulcers develop and discharge pus.
Animals may die after months or recover and shed organisms from RT or skin
Pathogenesis not well defined – organism dangerous to work with!

13. exposed nasal septum of a horse showing the range of lesions observed in glanders

15. Diagnosis Clinical signs
Lab diagnosis by sending pus, lesion discharge, blood for serology
(warn the lab-category 3 organism)
B. mallei will grow on simple media but not MacConkey.
Colonies are smooth, white, 1-2 mm.
Serology; e.g. complement fixation, agglutination
Mallein test

16. Mallein test

17. Treatment and control Test and cull
Antibiotics are inappropriate as treated animals may carry the organism and transmit it
Cleaning and disinfection of contaminated areas (formalin or iodophor)

18. Melioidosis Caused by Burkholderia pseudomallei
Endemic in soil and water in south east Asia (‘Vietnam time-bomb’), tropical Australia (Darwin)
Infection results from ingestion, inhalation or skin abrasion from soil/water contact
Opportunistic pathogen, stress-immunosupression predisposes to clinical disease

19. Melioidosis
Many animal species, including man, susceptible, subclinical infections occur in which the organism may remain latent and then re-activate
Infection may be acute or chronic, septicaemic, respiratory, disseminated and characterised by abscess formation
Organism may be cultured on blood agar or Ashdowns medium
Colonies are shiny, yellowish brown, small or rough with wrinkled corrugated surface

21. L’affaire du Jardin des Plantes
Horse from menagerie (zoo!) at Jardin des Plantes discovered by chance by a visitor from the Institute Pasteur in Paris to have melioidosis
Numerous other animals at the Jardin had melioidosis and soil contaminated with the organism
Zoo closed to help stop outbreak
Disinfection of environment and slaughter of all animals followed
To late – 2 other zoos affected and dissemination of B. pseudomallei across France discovered
Horses bore the brunt of infection, cases among animal handlers – 2 human deaths
Epidemic subsided – healthy respect among vets for B. pseudomallei in France ever since!
Infection imported by horses from Iran or giant panda from China!??

22. AEROMONAS Gram negative rods (3-4 μm) Grow at room temperature (25°C)
Non lactose fermenting
Ferment glucose – often with gas production
Motile (except A. salmonicida)
Primarily pathogens of reptiles and fish although some can infect mammals and birds
A. hydrophila -  haemolytic, Enteritis, Food poisoning in man
A. salmonicida –Brown pigment, Furunculosis in salmonids.
Isolation of A. salmonicida on blood agar at (25°C) for 48h

23. PIGMENT IN A. salmonicida (L) A. hydrophila (R)

24. FURUNCULOSIS

25. Vibrio Curved Gram negative rods (3-4 μm) Catalase positive
Ferment glucose
Motile
Require NaCl for growth
Significant in medical rather than vet microbiology
Main spp. are V.cholerae (the Cholera bacillus) and V.parahaemolyticus (food poisoning)
Only V.metschnikovii is associated with disease in animals. It causes cholera-like symptoms in chickens