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Gram-negative rods - Non-fermentors

Terms in this set (12)

Overview
-Aerobic, non-sporing, bacilli
-Glucose/lactose utilisation
.Do not ferment:
.Not utilised e.g. Burkholderia
.Oxidate it e.g. Pseudomonas
-Opportunistic pathogens
.Septicemia
.Meningitis
.Pneumonia
.UTI
.Surgical site infections
-Constantly undergoing continuous taxonomic
Medically important
-Soil/water environment
.Grow at a range of temperatures
-Colonise mucous membranes
-Cause disease:
.Opportunistically infect immunocompromised individuals
.After trauma
-Pseudomonas aeruginosa
-Acineobacter baumannii
-Stenotrophomas maltophilia
-Others
.Pseudomonas stutzeri
.Burkholderia cepacia
.Moraxella
Difficult diagnosis
-Culture
-Reliant on phenotypic characteristics
-Commercial identification - fluorescence-based tech - detects metabolic changes
.API 20 NE
.VITEK 2
-Identification issues
.E.g. non-P. aeroginosa, non-fermenters
Pseudomonadaceae
211 described species
-84 clinically relevant (to a degree)
Taxonomic revision
-Pseudomonas
-Burkholderia
-Ralstonia
-Comamonas
-Acidovorax
-Delftia
-Hyrodenophaga
-Brevundimonas
-Stenotrophomonas
-Xanthomonas
Pseudomonas aeruginosa
-Opportunistic
.Plants and animals
.Immunocompromised patients
-Single polar flagellum
-Differing colony types
.Small, rough - plants
.Large, smooth
.Mucoid
.Role in colonisation and virulence
-Fluoresces on Cetrimide Agar
-Most oxidase +ve
-42'C (others unable)
Mucoid colony type
-Striking characteristic
.CF pulmonary infection
-Alginate overproduction
.Not essential for biofilms
.Enables persistence
.Influences virulence - T3SS - Flagellum
-P. aeruginosa biofilm -> host immune response protection
.Inhibiting complement activation
.Decreasing phagocytosis and antibiotic resistance
Virulence
-Immunocompromised patients
.Cancer
.Suffering from severe burns
.Cystic fibrosis
-Pigment protection
.Pyoverdine (yellow-green and fluorescent)
.Pyorubin
.Pyocyanin - contributes to persistance in CF - interferes with cell function
Surface virulence factors: adhesins - epithelial cells or inanimate surfaces
Type IV pili
-Strong flexible filaments
-Adhesion, biofilm, motility
Flagella
-FliC (monopolar)
-Mucin binding
LPS
-Oligosaccharide interfere
-CF transmembrane conductance regulator (ABC-transporter - mutation)
-Mucus overproduction
-Adhesion
Extracellular virulence factors
-Complex secretion systems
-7 secretion systems across G-ves
-5 utilised by P. aeruginosa
.Type I (T1SS) - ABC
.Type II (T2SS) - Xcp and Hxc - extracellular proteins
.Type III (T3SS) - toxin injection
.Type V (T5SS) - EstA, LepB, LepA
.Type VI (T6SS) - target other bacteria
-Exotoxin A (T2SS) - protein syn inhibit
-Rhaminolipid - surfactant
-Elastases - connective tissue deg
-Alkaline protease (T1SS) - protein deg
-Phospholipase C - haemolysin
Antibiotic resistance
Intrinsic resistance
-Chromosomally encoded
Acquired resistance
-MGEs
3 most studied mechanisms
-Resistance genes
.B-lactams, aminoglycosides
-Efflux pumps
.12 resistance-nodulation-division (RND) systems
-Membrane impermeability
.OM--> prevents large, hydrophilic molecules
.Pass through porins (efflux counters)
Treatment
Issues with antibiotic resistance
-Combined therapy (fluoroquinolone and cephalosporin)
Targeting virulence
-QS inhibitors
-Biofilm inhibitors
-T3SS inhibitors
Vaccines in development
-LPS and flagella - failure
-Alginate
-PcrV (T3SS)
-Elastase
-Alkaline proteases
-Exotoxin A toxoid
-OprF and OprI
All rest are promising
Acinetobacter
Environmental
-Possible contamination
-Colonise without infection
Nosocomial
-Prolonged hospitalisation
Emerging opportunistic pathogen
-Immunocompromised
-Blood or wound infections
-Concern in conflict zones
Highly resistant
-Carbapenem resistant outbreaks
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