enterobacteriaceae n pseudomonas aeruginosa

7/27/2019 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
http://www.life.umd.edu/classroom/bsci424/pathogendescriptions/Enterobacteriaceae.htmhttp://www.life.umd.edu/classroom/bsci424/pathogendescriptions/Enterobacteriaceae.htmhttp://www.life.umd.edu/classroom/bsci424/pathogendescriptions/Enterobacteriaceae.htmhttp://www.life.umd.edu/classroom/bsci424/pathogendescriptions/Enterobacteriaceae.htmhttp://www.life.umd.edu/classroom/bsci424/pathogendescriptions/Enterobacteriaceae.htmhttp://www.life.umd.edu/classroom/bsci424/pathogendescriptions/Enterobacteriaceae.htm

enterobacteriaceae n pseudomonas aeruginosa

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