lecture 2 Flashcards
why is p.aeuginosa the epitome of an opportunistic pathogen?
what group is pseudomonas aeruginosa and the burkholderia genus apart of and why are the plant pathogens so environmentlally important?
what are proteobacteria broadly split into?
enteric and non-enteric genera
what is the difference between enteric and non-enteric genera?
what diets are more likely to carry pseudomonasaea?
vegetarians
Pseudomonadaceae characteristics
Gram-negative bacilli
Polar flagella
Aerobic (could this possibly be dogma?)
Non-fermentative
Many genera, including:
✓Pseudomonas
✓ Burkholderia
✓ Xanthomonas
✓ Ralstonia
✓ Zymomonas
✓ Sphingomonas
✓Stenotrophomonas
✓ Common human pathogens
✓Uncommon human pathogens
what do we mean by “opportunistic”
Opportunistic: cannot invade intact tissue, and so exploits failing host defences to initiate infection
Pseudomonadaceae aeruginosa infections in humans
Endocarditis: Mostly heart valves of IV drug users
Respiratory infections: 80% of CF patients colonised in lungs, cats and dogs with chronic illness
Bacteraemia and septicaemia: in immunocompromised patients (AIDS, diabetes mellitus, and severe burns)
Pseudomonadaceae aeruginosa infections in humans
Central Nervous System infections: meningitis and brain abscesses after invasion from contiguous structure (eg. inner ear or paranasal sinus)
Ear infections including external otitis: a predominant bacterial pathogen in external otitis, chronic in cats and dogs
Eye infections: causes devastating infections in the human eye
Bone and joint infections: most often seen in lV drug users, and in conjunction with urinary tract or pelvic infections
Urinary tract infections: usually hospital-acquired after catheterization,
P aeruginosa: infections in humans
Skin and soft tissue: After breakdown of integument
(burns, dermatitis) and high moisture conditions
(swimmers; toe webs; perineum; under nappies).
Gastrointestinal: any part (oropharynx to rectum) in
immunocompromised. Does not cause typical diarrhoeal / vomiting disease.
Organs: Bladder and lungs are common
Burn Toe web Hot tub folliculitis Eye
the different virulance factors mean that P aeruginosa can adapt and affect hosts in multifactoral mechanisms- what are they?
Fimbriae & other adhesins-
Attachment to host cells. Formation of biofilms
Neuraminidase- Modifies host receptors to aid fimbriae attachment
Polysaccharide capsule-Attachment to host tissues. Protects against immune system, and antibiotics
Endotoxin- May cause septic shock in host
Exotoxin A / Exoenzyme S- Inhibits host cell protein synthesis
Elastase, protease, haemolysins- Breaks down host cell fibres, and IgA / IgG
Pyocyanin- Generates superoxide and peroxide
radicals – tissue damage. Stimulates
inflammatory response. A siderophore
Exopolysaccharides Facilitate biofilm formation
P. aeruginosa characteristics
Can multiply in nutritionally poor environments
* API 20NE assimilation tests
* Aviation fuel
* Distilled water
* Photographic chemicals
* Cosmetics
* Plasticisers
P aeruginosa: routes of spread
Ubiquitous in the environment (potentially dogma):
* Soil & vegetation
* decaying organic matter
* Water
* Domestic environment
* Hospital environment
Spread via:
* Person – to – person
* Fomite spread
* Exposure to environmental sources
key facts about Burkholderia pseudomallei – melioidosis
A saprophytic bacterium found in parts of Southeast Asia, India, Africa, and North Australia
Found in soil, water, rice paddies. Long term
environmental survival: > year
Melioidosis: a severe infection in animals and humans in some tropical countries (~165 000 cases annually)
Localised infection from a break in the skin – may
progress to the bloodstream.
Pulmonary infection – mild bronchitis to severe
pneumonia
how are infections caused by melioidosis
Infections
Patients with latent melioidosis may be symptom-free for decades. The longest period
between presumed exposure and clinical presentation is ~62 years. Dubbed the “Vietnam
time-bomb” following military activity and soil disturbance.
Animals
Widespread. In 1975 a panda introduced to a Paris zoo caused a major outbreak – serious
damage to a number of zoo populations and equestrian clubs.
