Pseudomonas aeruginosa and Other Non-Fermenting Bacilli Flashcards
*Describe the type of patients who acquire Pseudomonas aeruginosa infections
Burn patients
Cystic fibrosis patients
Patients with hematologic malignancies
Immunocompromised patients
Can be part of the microbial flora in hospitalized patients and ambulatory, immunocompromised hosts
Common cause of ventilator associated pneumonia (people on ventilators)
-its an opportunistic pathogen/ wont affect healthy people
*List major toxins produced by Pseudomonas aeruginosa and describe their principle effect on human cells.
Exotoxin A
Exoenzyme S
Elastase
*Discuss the association of Burkholderia cepacia and pulmonary infection in cystic fibrosis patients
Cellular defect results in thickened viscous mucus layer in resp tract and impaired innate immunity
Results in impaired mucocillary transport and chronic infection with limited number of bacterial species
Chronic infection leads to intermittent pulmonary exacerbations
*Describe the gene defect and resultant pathology of cystic fibrosis disease
Caused by a mutation in gene: cystic fibrosis transmembrane conductance regulator(CFTR)
- Mutation in CFTR results in defects in innate immunity including decreased nitric oxide levels, failure to internalize bacteria in bronchial epithelial cells, increased inflammation in CF airway and abnormal electrolyte transport causing thick, dry, sticky mucus
- Abnormal mucus adversely effects mucocilliary clearance providing ideal niche for chronic lung infection
*diseases associated with Stenotrophomonas maltophilia
Opportunistic infection
- Bacteremia
- Pneumonia
- Meningitis
- Wound infections
- Urinary tract
- Treatment complicated by resistance to many commonly used antibiotics
> 95% of all clinical infections are hospital acquired
2nd leading cause of gram-negative nonfermentative bacillary infections
Hallmark of S. maltophilia disease is life-threatening systemic infections in debilitated patients (usually malignancy)
*diseases associated with Burkholderia cepacia
respiratory tract infections. Major clinical problem in patients with cystic fibrosis (CF) and chronic granulomatous disease (CGD)
Urinary tract infections
Septicemia
Other opportunistic infections
Resistant to most antibiotics
*diseases associated with Burkholderia pseudomallei
Melioidosis
*diseases associated with Acinetobacter baumannii
sites Low virulence but implicated in community acquired and nosocomial infections
Recovered from numerous human sources: blood, sputum, urine, feces, vagina
Found to colonize 45% of inpatient tracheostomy
*diseases associated with Elizabethkingia meningoseptica
Pathogenic for premature infants
Associated with neonatal meningitis
Epidemics may occur in nurseries
Nosocomial outbreaks traced to breast pumps used in hospital nurseries
Mortality rate as high as 55%
May cause pneumonia in adults usually in IC patients
*Name Non-Fermenting bacteria that are listed as potential bioterrorist agents
Burkholderia pseudomallei (category B- highly virulent, no immunity in US, aerosol release)
characteristics of Glucose Non-Fermenting Gram-Negative Bacilli
Gram‑negative, nonsporeforming bacteria, may be rods, or coccobacilli Obligate aerobes Good growth usually seen in 24 h Glucose not fermented Natural Habitat: water, soil, plants
characteristics of Pseudomonas aeruginosa
Aerobic Gram negative rod Motile with polar flagella Mucoid polysaccharide slime layer Pili on cell surface -Grows on blood and MacConkey agar producing spready colonies with a metallic sheen
- Identification
- Glucose Non-Fermenter
- Oxidase positive
- Grape-like odor
- Produces Pyocyanin
- Grows at 42oC (rare that a bacteria would grow at that high of a temp)
Exotoxin A
Correlates with virulence
Blocks protein synthesis much like diphtheria toxin
Most likely contributes to dermatonecrosis in wounds and tissue damage in lungs
Exoenzyme S
ADP-ribosylating toxin
Epithelial cell damage facilitates bacterial spread, tissue invasion and necrosis
Elastase
Results in tissue destruction and hemorrhagic lesions (ecthyma gangrenosum)
Two enzymes: Las A and Las B act synergistically to degrade elastin
Degrades compliment components and inhibits neutrophil chemotaxis and function
Pseudomonas types of infections
skin lung urinary ear eye bacteremia endocarditis (tricuspid valve) osteomyelitis Bacteremia with ecthyma gangrenosum
Bacteremia with ecthyma gangrenosum
EG is a well-recognized but uncommoncutaneous infection most often associated with a Pseudomonas aeruginosa bacteremia.
EG usually occurs in patients who are critically ill and immunocompromised and is almost always a sign of pseudomonalsepsis.
Characteristic lesions are hemorrhagic pustules or infarcted-appearing areas with surrounding erythema that evolve into necrotic ulcers surrounded by erythema.
The transformation of an early lesion to a necrotic ulcer may occur in as little as 12 h
pyocyanin
blue pigment produced by Pseudomonas aeruginosa that turns the agar blue.
p. aeruginosa also produces pyoveridin which is yellow (flourecent under UV light) therefore the agar appears green
Treatment of Pseudomonas Infections
Resistant to many of the common antibiotics used for Gram negative infections
Resistance due to changes in porins
Combination therapy of cell wall active agent + aminoglycoside for serious systemic infections
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?
Ear infection after swimming in a fresh water lake
Melioidosis
Community acquired urinary tract infection
Community acquired pneumoniae
Gastroenteritis following ingestion of contaminated water
Ear infection after swimming in a fresh water lake
where is Burkholderia pseudomallei found
Habitat: soil, water, vegetation of S.E. Asia, 20o north and south of equator.
Primarily found in India, Thailand, Vietnam, northern Australia. Also endemic in China, Taiwan, Laos
Melioidosis
caused by Burkholderia pseudomallei
- Acute Disease: septicemia with metastatic lesions. 95% mortality if untreated
- Subacute Disease: most common. TB like pneumonia with cellulitis and lymphangitis
- Chronic Disease: localized chronic cellulitis. Treat with antibiotics before draining otherwise become bacteremic
What is a pulmonary exacerbation?
Chronic infection leads to intermittent pulmonary exacerbations
Exacerbation characterized by recruitment of neutrophils, cytokine release, and high level of neutrophil derived elastases causing significant lung pathology.
Stenotrophomonas maltophilia treatment
Drug of choice is trimethoprim-sulfamethoxazole (SXT)
inherently resistant to beta lactam agents
