ENTEROBACTERIACEAEENTERIC GRAM NEGATIVE

RODSDr.Indumathi

Gokula Metropolis Clinical laboratory

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

ANTIGENIC STRUCTURE

• COMPLEX

• 3 ANTIGENS

• O (SOMATIC)

• H(FLAGELLAR)

• K(CAPSULAR)

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 ++--

PATHOGENICITY

• URINARY TRACT INFECTION

• DIARRHOEA

• PYOGENIC INFECTION

• SEPTICAEMIA

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

ENTEROPATHOGENIC E.COLI

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

EAEC

SEPSIS/MENINGITIS

• INADEQUATE NORMAL DEFENSES

• SUSCEPTIBLE : NEW BORN

• UROSEPSIS

• MENINGITIS : K1 ANTIGEN IN NEONATES