Download - Enterobacteriaceae n Pseudomonas Aeruginosa
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Enterobacteriaceae
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Family Enterobacteriaceae
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Morphology
Rod-shaped (bacili) 1-5 m in length
Gram-negative
All aerobes (but can be facultative anaerobes)
Glucose fermented Non-spore forming
Most have flagella (few non-motile)
Endotoxin producer
Fimbriated Capsulated, slime layer or neither
Complex cell wall
Antigenic structure
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Specimen Collection
Specimens whetherpus, tissue,sputum, fluids, rectal swabs, orfeces
should be cultured immediately or
placed on special media to preventovergrowth
Diagnosis by microscopic and cultural
examination ofurine Diagnosis by microscopic and cultural
examination ofcerebrospinal fluid
Diagnosis by blood culture
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Sites of Infections with
Members of the
Enterobacteriaceae
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Phatogenicity
Endotoxin: important virulence factor with wide-rangingeffects on host
Capsule: antiphagocytic
Antigenic phase variation: capability to alternatelyexpress or not express either capsule or flagella and
thus avoid host immunity Sequestration of nutritional factors, in particular, iron
by production ofsiderophores which are extracellulariron-chelating compounds(e.g., enterobactin, aerobactin)
Iron is important compound for both host and
pathogen and is limited in supply and thus must becompeted for
Much of iron in host body is sequestered in hemeproteins (e.g., hemoglobin, myoglobin) and in iron-chelating proteins (e.g., transferrin, lactoferrin)
http://www.life.umd.edu/classroom/bsci424/HostParasiteInteractions/Endotoxin.htmhttp://www.life.umd.edu/classroom/bsci424/Definitions.htmhttp://www.life.umd.edu/classroom/bsci424/Definitions.htmhttp://www.life.umd.edu/classroom/bsci424/HostParasiteInteractions/Endotoxin.htm -
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Resistance to serum killing: many bacteria are inherently
sensitive to nonspecific bloodborne components and tocirculating complement and the resultant complement-mediated clearance, but Enterobacteriaceae and otherbloodborne pathogens can resist such killing
Antimicrobial resistance
True pathogenic members of the Enterobacteriaceae may
possess specific virulence features, which are unique toindividual genera or species
Adhesins
Exotoxins, (e.g., enterotoxins which act in the smallintestine)
Antigens which stimulate antibody production by the hostinclude: K - polysaccharide capsularantigens
H - flagellarantigen
O - somatic polysaccharide antigen (associated with LPS)
http://www.life.umd.edu/classroom/bsci424/Chemotherapy/AntibioticResistance.htmhttp://www.life.umd.edu/classroom/bsci424/Definitions.htmhttp://www.life.umd.edu/classroom/bsci424/HostParasiteInteractions/Exotoxin.htmhttp://www.life.umd.edu/classroom/bsci424/Definitions.htmEnterotoxinhttp://www.life.umd.edu/classroom/bsci424/Definitions.htmhttp://www.life.umd.edu/classroom/bsci424/Definitions.htmhttp://www.life.umd.edu/classroom/bsci424/Definitions.htmhttp://www.life.umd.edu/classroom/bsci424/Definitions.htmhttp://www.life.umd.edu/classroom/bsci424/Definitions.htmhttp://www.life.umd.edu/classroom/bsci424/Definitions.htmhttp://www.life.umd.edu/classroom/bsci424/Definitions.htmEnterotoxinhttp://www.life.umd.edu/classroom/bsci424/HostParasiteInteractions/Exotoxin.htmhttp://www.life.umd.edu/classroom/bsci424/Definitions.htmhttp://www.life.umd.edu/classroom/bsci424/Chemotherapy/AntibioticResistance.htm -
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Lab Diagnosis
Special isolation media: contain various substancesincluding indicators, inhibitors, etc.
Media and tests to differentiate the genera of thefamily
Tests that divide species of the genera, e.g., patterns
of acid production from various carbohydrates Various species differ in the carbohydrates from which
acid may be produced and end products that may beformed from various substrates
Culture:
Colony morphology: moist, gray(except Serratia marcescans which appears red)smooth colonies on non-selective media
Special differential and selective media used forseparation of genera and species
Some strains are beta hemolytic on blood agar
http://www.life.umd.edu/classroom/bsci424/pathogendescriptions/Enterobacteriaceae.htmhttp://www.life.umd.edu/classroom/bsci424/pathogendescriptions/Enterobacteriaceae.htm -
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Pseudomonas aeruginosa
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Morphology
gram-negative, rod-shaped,
asporogenous, and monoflagellated bacterium
1-5 m long and 0.5-1.0 m wide
aerobic respiration (with oxygen)
anaerobically on nitrate or other alternative electron
acceptors.
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Specimen CollectionDepending on the nature of infection, an
appropriate specimen is collected
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Pathogenicity
nosocomial infectionopportunistic human pathogen. Mostly in cystic fibrosis,cancer, or AIDS patients
exhibits intrinsic resistance to chemotherapeutic agentsand antibiotics - capsule
secrets many virulent factors
- exotoxin A, which inhibits the protein synthesis of thehosts cells.
It also breaks down human immunoglobin proteins andserum alpha body organs, such as the lungs, the urinary
tract, and kidneys
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Lab diagnosisMacConkey agar - clear colonies (as it does not
ferment lactose)
Oxidase - test positive
Confirmatory tests - production of the blue-green
pigment pyocyanin on cetrimide agarand growth at42C.
http://en.wikipedia.org/wiki/MacConkey_agarhttp://en.wikipedia.org/wiki/Oxidasehttp://en.wikipedia.org/wiki/Pyocyaninhttp://en.wikipedia.org/wiki/Cetrimide_agarhttp://en.wikipedia.org/wiki/Cetrimide_agarhttp://en.wikipedia.org/wiki/Cetrimide_agarhttp://en.wikipedia.org/wiki/Cetrimide_agarhttp://en.wikipedia.org/wiki/Pyocyaninhttp://en.wikipedia.org/wiki/Oxidasehttp://en.wikipedia.org/wiki/MacConkey_agarhttp://en.wikipedia.org/wiki/MacConkey_agarhttp://en.wikipedia.org/wiki/MacConkey_agar -
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http://www.life.umd.edu/classroom/bsci424/pathogendescriptions/Enterobact
eriaceae.htm
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