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FEATURES
• LARGE HETEROGENOUS GROUP : • NATURAL HABITAT : HUMAN/ANIMAL
INTESTINE• MORE THAN 25 GENERA AND 110 SPECIES; • 20-25 CLINICALLY SIGNIFICANT SPECIES• FACULTATIVE ANAEROBES, FERMENT
CARBOHYDRATES, COMPLEX ANTIGENIC STRUCTURE
• PRODUCE TOXINS AND VIRULENCE FACTORS
CHARACTERISTICS
• GRAM NEGATIVE BACILLI• NON SPORING• MOTILE(PERITRICHOUS FLAGELLA)/NON MOTILE• CAPSULATED/NON CAPSULATED• NON FASTIDIOUS• FERMENT GLUCOSE WITH ACID/GAS• REDUCE NITRATES TO NITRITES• OXIDASE NEGATIVE/CATALASE POSITIVE• BIOCHEMICAL TESTS DONE TO DIFFERENTIATE
THE VARIOUS SPECIES
CLASSIFICATION
• COMPLEX• CHANGING
TAXONOMY
LACTOSE FERMENTERS
(LF)
LATE LACTOSE FERMENTER
(LLF)
LACTOSE NON FERMENTERS
NLF
E.COLI
KLEBSIELLA
ENTEROBACTER
SERRATIA
CITROBACTER
ARIZONA
PROVIDENCIA
SHIGELLA
SALMONELLA
PROTEUS
O ANTIGEN (SOMATIC)
• MOST EXTERNAL PART OF CELL WALL LPS• REPEAT POLYSACCHARIDE UNITS• HEAT AND ALCOHOL RESISTANT• DETECTED BY AGGLUTINATION• ANTIBODIES TO ‘O’ ARE IgM• GENUS SPECIFIC• CROSS SHARING • ASSOCIATED WITH DISEASE (UTI OR
DIARRHOEA CAUSING E.COLI)• MORE THAN 150 TYPES
H ANTIGENS(FLAGELLAR)
• LOCATED ON FLAGELLA
• HEAT AND ALCOHOL LABILE
• ANTIBODIES FLUFFY CLUMPS MAINLY IgG TYPE
• MORE THAN 50 TYPES
K ANTIGENS (CAPSULAR)
• EXTERNAL TO O ANTIGEN• MORE THAN 100 TYPES• PRESENT IN SOME GENERA• POLYSACCHARIDE/PROTEINS• ASSOCIATED WITH VIRULENCE• E.G.K1 OF E.COLI MENINGITIS, UTI• KLEBSIELLA : UTI 8,9,10,24• Vi ANTIGENS IN SALMONELLA• INHIBITS PHAGOCYTOSIS• ANTIGENIC FORMULA : E.COLI 055:K5:H21
ESCHERICHIA COLI
• NORMAL INTESTINAL FLORA
• DETECTION IN WATER INDICATES RECENT FECAL CONTAMINATION
• ONLY ONE SPECIES
• SEVERAL SEROTYPES AND BIOTYPES
• MA : LF
• IMVIC ++--
UTI
• COMMON CAUSE OF ASCENDING INFECTION
• PREGNANCY, SEXUALLY ACTIVE FEMALES, OTHER PREDISPOSING FACTORS LIKE OBSTRUCTION
• PYELONEPHRITIS• UROPATHOGENIC STRAIN• VIRULENCE FACTOR : HAEMOLYSIN • P PILUS• K ANTIGEN • O1,2,4,6,7,75; K SEROTYPES K1,2,3,5,12,13
E.COLI DIARRHOEA
• 5 STRAINS
• ENTEROPATHOGENIC(EPEC)
• ENTEROTOXIGENIC(ETEC)
• ENTEROINVASIVE(EIEC)
• ENTEROHAEMORRHAGIC(EHEC)
• ENTEROAGGREGATIVE(EAEC)/
• DIFFUSE AGGREGATIVE
DIARRHOEA
• WATERY STOOLS
• ABDOMENAL CRAMPS
• VOMITING
• WITH OR WITHOUT FEVER
• WITH OR WITHOUT BLOOD AND MUCUS
• SELF LIMITING 5-10 DAYS
EPEC
• INFANTILE DIARRHOEA : SPORADIC CASES/INSTITUTIONAL OUTBREAK
• INCUBATION 1-2 DAYS• O26B6,055B5 STRAINS• VIRULENCE FACTOR: PILI (Bfp) ;
intimin(adhesin); Tir ( translocated intimin receptor)
• BACTERIAL ATTACHMENT TO MICROVILLI; AND EFFACING (DISTRUPTION) MECHANISM
EPEC DIAGNOSIS
• ISOLATION
• SEROTYPING WITH POLYVALENT SERA
• TISSUE CULTURE ADHESION : FLUORESCENT ACTIN STAIN
• DNA BASED DETECTION FOR VIRULENCE GENES
ETEC
• TRAVELLERS’ DIARRHOEA
• BOTH ADULTS AND CHILDREN
• CONSUMPTION OF WATER CONTAMINATED WITH SEWAGE
• IP 1-7 DAYS NO FEVER
• SELF LIMITING 2-6 DAYS
• O6, 08, 025, 027
ETEC
• VIRULENCE FACTOR• ENTEROTOXIN : LT AND ST: GENETIC
CONTROL• PILI OR K PROTEINS• LT : CHOLERA LIKE TOXIN, ACTIVATES
CYCLIC AMP PATHWAY : FLUID HYPERSECRETION INTENSE & PROLONGED
ST : ACTIVATES CYCLIC GMP PATHWAY: SHORT ONSET OF ACTION
ETEC
• DIAGNOSIS• CULTURE FAECES• DETECT LT/ST TOXIN• LT TOXIN BY : IN VIVO • IN VITRO• IN VIVO : LIGATED RABBIT ILEAL LOOP (6-18HRS)• ADULT RABBIT SKIN TEST • IN VITRO : ELISA• RIA• TISSUE CULTURE (CHO CELL LINES)
EIEC
• DYSENTRY/FEVER• OLDER CHILDREN AND ADULTS• O124, 136, 144• IP 3 DAYS ; DURATION 7-10DAYS• VIRULENCE FACTOR: PLASMID CODED OMP• INVASIVE:
ENDOCYTOSIS→INFLAMMATION→NECROSIS→ULCERATIONDETECTION : SERENY TEST HeLA CELL INVASION
EHEC
• DEVELOPED COUNTRIES• CONTAMINATED BEEF AND UNPASTEURIZED MILK• HAEMORRHAGIC COLITIS/HUS• IP 3-4 DAYS• DURATION : 5-10 DAYS• O157H7• VEROTOXIN :CYTOTOXIN:SHIGA LIKE TOXIN• DETECTION OF VERO TOXIN BY GENETIC PROBES• GROWTH ON MA SORBITOL AGAR
EAEC
ACUTE OR CHRONIC DIARRHOEA
>14DAYS DURATION
DEVELOPING COUNTRIES
FOOD BORNE
CHARACTERISTIC ATTACHMENT TO CELLS : STACKED BRICK FORMATION
VIRULENCE : FIMBRIA, HEAT LABILE ENTEROTOXIN AND CYTOTOXIN