Pseudomonas and Other Non fermenters of Glucose Flashcards
What are the characterisitics of glucose non-fermenting gram neg bacilli?
Gram neg Nonspore forming Rods/Coccobacilli Obligate Aerobes Good growth in 24h No glucose fermentation Found in nature in water, soil, plants (Not part of normal gut flora)
Characteristics of Pseudomonas Aeruginosa?
Aerobic Gram Neg Rod Motile wit polar flagella Mucoid polysaccharide slime layer Pili Oxidase Positive Pyocyanin Grape like odor Opportunistic Pathogen
Where is pseudomonas found?
Environment
Grows in unsterile water, medications
Hospital
Moist areas
*Dont bring stuff fresh from outside like flowers when seeing immunosuppressed patients -> can get resistant organisms in
What factors predispose patients to serious pseudomonas infections?
Burns
Cystic Fibrosis
Hematologic Malignancies
Immunocompromised
How can you get pseudomonas skin infections?
Burn wounds
Folliculitis (hot tubs, whirlpools, water slides, swimming pools)
Nail infections
What are the types of pseudomonas pulmonary infections?
Asymptomatic colonization
Cystic fibrosis or chronic lung disease
Severe Necrotizing bronchopneumonia
VAP: ventilator associated penumonia
What are other pseudomnal infections?
UTI Ear infections : swimmer's ear; chronic otitis media Eye infections Bacteremia: Ecthyma Gangrenosum Endocarditis: Tricuspid valve Osteomyelitis
What is ecthyma gangrenosum
Happens in bacteremia due to P.Aeruginosa infections
Occurs in patients who are critically ill and immunocompromised => signals pseudomonal sepsis
What do ecthyma gangrenosum look like?
Hemorrhagic pustules or infarcted looking areas with surrounding erythema -> evolves into necrotic ulcers surrounded by erythema
What are hte virulence factors of P.Aeruginosa?
Structural: Capsule, Pili, LPS, Pyocyanin
Exotoxin A
Exoenzyme S
Elastase
What color is produced by the colonies of Pseudomonas on agar plate?
Greenish color due to pyocyanin + pyoveridin
What does Exotoxin A do in Pseudomonas?
Virulence factor
Blocks protein synthesis similar ot diptheria toxin
What does Exoenzyme S do in Pseudomonas?
ADP Ribosylation toxin -> damage epithelial cells -> promote bacterial spread, tissue invasion and necrosis
What does Elastase do in Pseudomonas?
Destroy elastin -> tissue destruction -> lung parenchymal damage and hemorrhagic lesions (Ecthyma Gangrenosum)
Also degrades complement components and prevent neutrophil chemotaxis and funciton
How is P.Aeruginosa infections diagnosed?
Culture: Grown on blood and MacConkey -> spready colonies with metallic sheen/offwhite color
ID: Glucose non fermenter, Oxidase Positive, Grape like odor, produce pyocyanin, Grows at 42deg C
What does Pseudomonoas look like on MacConkey Agar compared to E.Coli?
P.Aeruginosa: blue-grey colonies with lactose negative with green pigmentation
Ecoli: Purple colonies
How is Pseudomonas Infections treated?
REistant to many common abx for gram neg infections due to porins
Combination Therapy: Cell wall active agent + Aminoglycosides
A gram‐negative rod grows as a colorless colony on a
MacConkey agar plate.Further laboratory testing
shows the organism is oxidase positive, does not
ferment glucose, produces a sweet grape‐like odor and
grows at 420C.Which of the following clinical
infections is most likely to be caused by this organism?
A. Ear infection after swimming in a fresh water
lake
B. Melioidosis
C. Community acquired urinary tract infection
D. Community acquired pneumoniae
E. Gastroenteritis following ingestion of
contaminated water
A
What is important about Burkholderia Pseudomallei?
Causes melioidosis
Cat B Biothreat Agent
High Fatality rate associated with Bacteremia caused by B.Pseudomallei
What are the different kinds of Melioidosis caused by B.Pseudomallei?
Acute: Septicemia with metastatic lesions -> 95% mortality if untreated
Subacute: Most common; TB like pneumonia wiht cellulitis and lymphangitis
Chronic: Localized chronic cellulitis; Treat with abx before draining or will become bacteremic
Can show latency and come out later as late infection
How is B.Pseudomallei treated?
Ceftriaxone and Vanco
What are some complicaitons prsent with CF patients?
Mutation in CFTR -> defective innate immunity -> cannot internalize bacteria in bronchial epithelial cells -> increased inflmmation in airway + abnormal electrolyte transport -> thick dry sticky mucus => ideal niche for lung infection
How are pulmonary exacerbations and CF related?
Pts with CF have impaired mucocilliary transport with chronic infections leading to pulmonary exacerbations
This leads to impaired innate immunity and lung pathology due to neutrophil acitons
Which known pathogens cause chronic lung disease in CF patients?
S.Aureus
P.Aeruginosa
B.Cepacia Complex
