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 FERMENTERSNLF

E.COLIKLEBSIELLAENTEROBACTER

SERRATIACITROBACTERARIZONAPROVIDENCIA

SHIGELLASALMONELLAPROTEUS

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 DURATIONDEVELOPING COUNTRIESFOOD BORNECHARACTERISTIC ATTACHMENT TO

CELLS : STACKED BRICK FORMATIONVIRULENCE : FIMBRIA, HEAT LABILE

ENTEROTOXIN AND CYTOTOXIN

EAEC

SEPSIS/MENINGITIS

• INADEQUATE NORMAL DEFENSES• SUSCEPTIBLE : NEW BORN• UROSEPSIS• MENINGITIS : K1 ANTIGEN IN

NEONATES