E. coli

General discription about E coli.. Classification scheme of E coli. Pathogenecity of E coli. Pathological characters of E coli. slide contains animations and may not support in mobile.. Use laptop for full view

1. Escherichia coli ( E. coli ) Prepared by Prashant Dahal BSc. Microbiology Final Year Sunsari Technical College

2. TABLE OF CONTENT Table of Contents 1. Introduction 2. Morphology 3. Serotypes 4. Cultural characters 5. Biochemistry 6. Clinical significances a. Virulence factors b. Pathotypes of E. coli c. Pathogenesis d. Disease causing 7. Diagnosis 8. Treatment 9. Positive roles 10. Summary & Sources

3. INTRODUCTION Gram-negative, Rod shaped, Facultative anaerobic, non- sporing motile/non-motile coliform bacteria of genus Escherichia in Enterobacteriaceae family. Named after discoverer, German physician :Theodor Escherich, in 1886 Commensal / pathogenic; found in GIT of warm- blodded , hence in Enteric bacteria\ One of the most studied bacetria

4. MORPHOLOGY Rod shaped, around 2 m (1–3) X 0.4–0.7 m in size, 0.7 cubic m volume Peritrichous flagella, fimbriae/ pilli presence Some contains, polysaccharide capsule Mostly singular form or in pair  

5. Serotypes Serotyping is based on 3 major antigens: somatic lipopolysaccharide (LPS) (O ) , heat stable, common to Enterobacteriaceae, 173 types flagellar (H ) heat & alcohol labile, genus specific proteins, 75 types capsular ( K) heat-labile, acidic, 103 types Beside there is another antigenic structure, fimbrial (F) : heat labile, 2 types( K88 , K99 ) SEROTYPES More than 200 serotypes Eg : 1. E. coli O104:H4 (caused diarrhoeal outbreak in Germany ,2011) 2 . E. coli O157:H7 ( STEC , diarrhoeal, UTI infection) 3. E. coli O121 4. E. coli O103 , O128

6. CULTURE Aerobic / Facultative , pH: 7.2, Temp.: 10-49 with optm.temp . 37, generation time 20 min Common specimens for clinical culture: Urine, Stool, Blood, CSF, Aspirates Common media : MAC, CLED , NA, BA, CAP, TSA, EMB, VRBA , m-Endo MEDIA CHARACTERS MAC circular, moist, smooth, non- mucoid , 2- 3mm , convex , pink with darker pink halo, ( mucoid if capsulated) CLED Opaque yellow colonies with a slightly deeper yellow center , circular, moist, smooth, non- mucoid , 2mm , convex BAP big, circular, 1- 4mm , gray and moist, - haemolytic EMB Blue-black centered, green metallic sheen, circular, 2- 3mm , convex, smooth NA large, 2- 4mm , circular, low convex, grayish, white, moist, smooth, and opaque XLD Yellow, circular, large, flat MEDIA CHARACTERS MAC circular, moist, smooth, non- mucoid , 2- 3mm , convex , pink with darker pink halo, ( mucoid if capsulated) CLED Opaque yellow colonies with a slightly deeper yellow center , circular, moist, smooth, non- mucoid , 2mm , convex BAP EMB Blue-black centered, green metallic sheen, circular, 2- 3mm , convex, smooth NA large, 2- 4mm , circular, low convex, grayish, white, moist, smooth, and opaque XLD Yellow, circular, large, flat

7. BIOCHEMICAL CHARACTERS TEST RESULT Gm.Stain -ve (Red/ pink) Rod IMViC + + - - TSI Acid / Acid (Y /Y ) Urease -ve Catalase +ve Oxidase -ve Nitrate +ve H2S -ve Motility +ve (-ve absent flagella)

8. CLINICAL SIGNIFICANCE VIRULENCE FACTORS BIOLOGICAL ROLE Fimbriae Adherence of bacteria, mannose-resistant hemagglutination Adhesins firm adhesion, prevent flushing in GIT , GUT Endotoxin manifestations of endotoxic shock, protect from phagocytosis & bactericidal effects of complement Capsule Protect from serum killing & phagocytosis Hemolysins pathogenesis of disease caused by uropathogenic strains (Enterotoxins ) 1. Shiga toxins 2. Heat stable toxin 3. Heat labile toxin Cytotoxins Causes increased secretion of fluids Watery diarrhea due to hypersecretion of fluid into the lumen Sequestration of growth factors Compete for nutrition in host cell PATHO -TYPES 1. ETEC -- Enterotoxigenic   E. coli   2. EPEC -- Enteropathogenic  E. coli 3. EAEC -- Enteroaggregative   E. coli 4. EIEC -- Enteroinvasive   E. coli 5. EHEC -- Enterohemorrhagic   E. coli ( STEC -- Shiga Toxin–Producing  E. coli) ( VTEC -- Verocytotoxin -Producing E. coli) 6. DAEC -- Diffusely-adherent  E. coli  

9. PATHOGENESIS EHEC ( STEC , VTEC ) Epidemiology / Diesease : Hemorrhagic colitis and hemolytic uremic syndrome in all ages and thrombotic thrombocytopenic purpura in adults Diarrhoea : Bloody or non-bloody Mechanism: Cytotoxin production and adherence caused by E.coli 0157:H7 , E.coli O26:H11

10. EPEC Epidemiology/Disease: Acute and chronic endemic and epidemic diarrhea in infants Diarrhoea : Watery Mechanism : Adherence effacement, adhere to intestinal mucosa and produce a characteristic lesion in the gastrointestinal tract  via. plasmid coded bundle-forming pill, which form cup-like projections called pedestals. Do not produce ENTEROTOXIN and NON - INVASIVE Fecal-oral exposure O44, O55, O86, O111, O114, O119, O125, O126, O127, O128, O142 and O158.  

11. EAEC Epidemiology / Disease : Chronic diarrhea and growth retardation in infants Diarrhoea : Watery Mechanism : Adherence, "stacked brick" adherence pattern on HEP -2 or HeLa cells.; Gene encoding Adhesin and ST is variable E. coli  0104: H4 , produce ST

12. ETEC Disease/ Epidemiology : Traveler’s Diarrhoea , & Infantile diarrhea in developing countries Diarrhoea : Watery Mechanism: Adherence ( mediated by fimbrial protein called CFA ( colorlization factor antigen)) , enterotoxin production ( both heat-labile and/or heat-stable enterotoxins.) one of the most common causes of bacterial diarrheal disease in developing countries (estimated 840 million cases annually) (O6:H16, O8:H9 or O8:H-, O15:H11) E. coli-06, 08, 0 15, 025, 0 27, 0 153, 0 159

13. EIEC Epidemiology / Disease : Diarrhea with fever in all ages, Diarrhoea : Bloody or non-bloody Mechanism : invade and destroy the colonic epithelium , plasmid mediated Adherence & invasion of mucosa rare in both developed and developing countries Few serotypes; O28, O112, O115, O124, O136, O143, O144, O147, O152, O164 and O167

14. DAEC Epidemiology : Age dependent diarrhoea in Children (2-6 yr ) Diarrhoea : Watery Mechanism : adherence by fimbriae Less known

15. Disease caused 1. UTI (bacteriuria) 2. Gastroenteritis ( Diarrhoea , ulcer) 3. Septicemia 4. Neonatal sepsis 5. Meningitis

16. Laboratory Diagnosis Sample: Urine for UTI, Stool for gastroenteritis, Blood for speticemia /sepsis, CSF for meningitidis Microscopy Culture & Biochemical tests T o separate PATHO -TYPES 1 . Commercially available immunoassay ( ETEC ) 2. culture and adherence on Hep -2, HeLa cells ( EPEC , EAEC ) 3. ELISA, latex- agglitunation , SMAC culture ( STEC ) 4. Sereny test , HeLa ( EIEC ) E. PCR and Gene coding for serotyping

17. E. coli O157:H7 , non-sorbitol fermenter Sorbitol fermenter bacteria

18. TREATMENT Generally, adult need none in diarrhoea UTI - antibacterial agents, including ampicillin, cephalosporins, tetracyclines , quinolones, aminoglycosides, trimethoprim and sulphonamides Enteric E. coli: Fluid + ORS supplement, antibiotics are used in severe cases Meningititis and sepsis : Compulsory antibiotics However there is a huge obstacle developing in treatment of E. coli : ABR pathogenic strains of E. coli WHO has listed ABR E. coli as pathogen of concern Resistance is mainly by production of Beta-lactamases ESBL, ABL, CBL are most commonly associated in human infection

19. POSITIVE ROLES OF E. COLI Commensal of GIT , producing Vit.K and preventing colonization of other enteric pathogens like Cholera, Shigella, Pseudo.., Staph Production of Insulin commercially Tools of bio-technology in gene cloning and transfer Used as probiotics Indicator organism of Water, milk and juices contamination

20. SUMMARY Gm(-ve), rod, facultative, flagellate, most studied Commensal in GIT of all vertebrates Occasionally cause disease Pathogens are classified as EIEC , EPEC , EAEC , EHEC , ETEC , DAEC EMB, m-Endo selective media MAC, SMAC , CLED , BA – used in clinical culture

21. REFERENCES Greenwood Medical Microbiology Textbook of Diagnostic Microbiology by Connie R Mahon, Donald C. Lehman & George Mansuseli Textbook of Microbiology & Immunology by Subash Chandra Parija Escherichia coli (E. coli)- An Overview/ Microbenotes.com E. coli Pathotypes / Microbenotes.com Murray, P. R., Rosenthal, K. S., & Pfaller , M. A. (2013). Medical microbiology. Philadelphia: Elsevier/Saunders Sastry A.S . & Bhat S.K . (2016). Essentials of Medical Microbiology. New Delhi : Jaypee Brothers Medical Publishers . Wikipedia source

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