Enteric Gram-Negative Rods (Enterobacteriaceae) Junqi zhang(张俊琪),PhD MOH&MOE Key Lab of Medical Molecular Virology Shanghai Medical College, Fudan University (复旦大学上海医学院分子病毒学教育部/卫生部重点实验室)
Enteric Gram-Negative Rods (Enterobacteriaceae) Junqi Zhang (张俊琪), PhD MOH&MOE Key Lab of Medical Molecular Virology Shanghai Medical College, Fudan University (复旦大学上海医学院分子病毒学教育部/卫生部重点实验室)
Enterobacteriaceae enterobacteriaceae v enteric gram-negative rods enteric bacteria More than 50 genera and 120 AA/3=2m< enteric bacilli √ coliforms 怜 species have been defined
enterobacteriaceae enteric gram-negative rods enteric bacteria enteric bacilli coliforms Enterobacteriaceae More than 50 genera and 120 species have been defined
Enterobacteriaceae v The enterobacteriaceae are a large and diverse family of Gram-negative rods, members of which are both free-living and part of the indigenous flora of humans and animals v Some of these organisms are part of the normal intestinal flora, eg.E coli y while others are regularly pathogenic for humans and animals: Salmonella, Shigella
The enterobacteriaceae are a large and diverse family of Gram-negative rods, members of which are both free-living and part of the indigenous flora of humans and animals Some of these organisms are part of the normal intestinal flora, eg.E.coli while others are regularly pathogenic for humans and animals: Salmonella, Shigella Enterobacteriaceae
General characteristics 1.T ypical morphology: Gram-negative rods: enteric bacilli on-sporeformin 2 Motile via flagella eXcept shigella and Klebsiella Can not distinguish each other by their morphology 2. Growth Characteristics Carbohydrate fermentation patterns and the activity of amino acid decarboxylases and other enzymes are used in biochemical differentiation Easy to culture in vitro, using biochemical tests for classification and identification
General Characteristics 1. Typical morphology: Gram-negative rods: enteric bacilli; Non-sporeforming; Motile via flagella EXCEPT Shigella and Klebsiella Can not distinguish each other by their morphology 2. Growth Characteristics: Carbohydrate fermentation patterns and the activity of amino acid decarboxylases and other enzymes are used in biochemical differentiation Easy to culture in vitro, using biochemical tests for classification and identification
Differential media MacConkey Agar (MCA) .Ingredients peptone, lactose, bile salts, sodium chloride and pH indicator (neutral red) aBacteria that ferment lactose in the medlium w produce acid byproducts which will change the color of the ph indicator from yellow to red
MacConkey Agar (MCA) Ingredients : peptone, lactose, bile salts, sodium chloride and pH indicator (neutral red). Bacteria that ferment lactose in the medium will produce acid byproducts, which will change the color of the pH indicator from yellow to red. Differential media
Clinically significant Enterobacteriaceae Escherichia Lactose fermented rapidly Shigella Lactose not fermented Salmonella Klebsiella ● roteus Citrobacter Serratia Mac conkey’ s agar
Clinically Significant Enterobacteriaceae • Escherichia • Shigella • Salmonella • Klebsiella • Proteus • Citrobacter • Serratia • …… Lactose NOT fermented Lactose fermented rapidly MacConkey's agar
Differential media Triple Sugar Iron(TSD slant Ingredients glucose sucrose, lactose, Slant, lactose, FeSO4 ferrous sulfate, and pH indicator phenol red (phenol red); Bacteria that ferment any of the three Butt, glucose, phenol red sugars in the medium will produce byproducts. These byproducts are usually acids, which will change the color of the ph indicator from red to yellow; Some bacteria utilize thiosulfate anion as a terminal electron acceptor, reducing it to hydrogen sulfide. The byproduct H2s reacts with ferrous sulfate in the medium to form black precipitate. E Coli Samonella Shigella
Differential media Triple Sugar Iron (TSI) slant • Ingredients : glucose ,sucrose , lactose , ferrous sulfate, and pH indicator (phenol red); • Bacteria that ferment any of the three sugars in the medium will produce byproducts. These byproducts are usually acids, which will change the color of the pH indicator from red to yellow; • Some bacteria utilize thiosulfate anion as a terminal electron acceptor, reducing it to hydrogen sulfide. The byproduct H2S reacts with ferrous sulfate in the medium to form black precipitate. Slant, lactose,FeSO4, phenol red Butt, glucose, phenol red E.Coli Samonella Shigella
Glucose Lactose motivity H,S Ecoli 十 Samonella+ 十 Shigella API 10s systems ONPG GLU ARA LDC ODC CIT H2S URE TDA IND
Shigella + - - - Samonella + - + + E.coli + + + - Glucose Lactose motivity H2S API 10s systems
3. Possess a complex antigenic structure Immulogic test for“sero” classification Flagella(H antigen Capsule(K or Vi antigen Lipopolysaccharide( LPS)or n O polysaccharid Polysaccharide lipid a U7P点CF就E ooplasmIc sp proprotein UPOPEOTEH Peptidogly PEPTDOCUCAH Inner membrane Cytopl
3. Possess a complex antigenic structure Immulogic test for “sero” classification
4. Easy to variation Plasmids and transfer of genetic information Original organisms Conjugation transduction Old donor New Donor transformation Drug resistant variation New type organism To oXinogeny variation Biochemical test variation
4. Easy to variation transformation transduction Original organisms Conjugation New type organism Drug resistant variation Toxinogeny variation Biochemical test variation