ENTEROBACTERIACEAE

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ENTEROBACTERIACEAE

• Dr Gehan Panagoda
• Division of Microbiology
• Faculty of Dental Sciences
• University of Peradeniya

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• Gram -ve bacilli/rods
• Natural habitat - Intestinal tract of
  humans/animals
• Facultative anaerobes/aerobes

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• Ferment CHO, Often produce gas
• Enterics found in water is used as a proof of
  contamination with sewerage.

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• There are more than 25 genera,110 species.
• Clinically significant 25 species.

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• Grow on peptone or meat extract.
• Grow well on McConkey agar.
• Catalase ve
• Oxydase -ve.

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• Antigenic structure.
• Complex
• Lipopolisaccharides/Somatic or O antigen
• Heat stable.more than 150 types
• Most external in the cell wall
• detected by bacterial agglutination
• Antibody produced is predominantly IgM

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• Capsular/K antigen
• Sometimes external to O antigen but not always
• Can be polysaccharides or protein
• Flagella /H antigen
• Heat and alcohol labile.

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• Colicines/Bacteriocines
• Produced by many Gram -ves
• Virus like bactericidal substance
• Active against some other bacteria of similar
• or closely related species

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• Production is controlled by plasmids
• E coli - colicines
• Serratia - marcescines
• Pseudomonas - Pyocines

THIS MAY BE ONE OF THE REASONS FOR THEIR SUCCESS
AS COMMENSALS
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• Toxins/Enzymes
• Endotoxins- Complex LPS in the cell wall
• Exotoxins

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• Relevance in clinical
  medicine
• Normally nonpathogenic.
• In some instances, they even contribute to
  normal.
• function and nutrition.
• Other species cause hospital/community acquired
• disease
• Become pathogenic when they change their
  habitat.
• When the host defense is reduced, act as
  opportunistic
• pathogens.

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• Common infections
• UTI
• RTI
• Diarrhoea
• Enterocolitis
• Wound infection

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Lactose fermenters Non lactose fermenters

• E. Coli
• Klebsiella
• Serratia
• Enterobacter

• Shigella
• Salmonella
• Proteus
• Yersinia

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Relevance in clinical medicine

• Primary pathogens - Shigella sp Salmonella typhi
• Common infections - UTI ( E. coli, Proteus)
• Less common but important -
• Respiratory - Klebsiella
• Enterocolitis - Yersinia

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• Hospital infections - due to colonization
• - Contamination
• - Compromised patients

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E SCHERICHIA COLI UTI Most common cause for
UTI,90 UTI in young women is due to E
coli. Diarrhoea E coli is classified on the
basis of virulence and the mechanism of causing
diarrhoea
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• A.Enteropathogenic E coli (EPEC)
• Important cause of diarrhoea in infants of
• developing countries.
• Adhere to mucosal cells in small bowel,loss of
  microvilli, NONINVASIVE
• enter to cell body. result in watery diarrhoea.
• Self limiting ,can be chronic.
• Normally do not produce toxins
• Few EPEC produce 0114, 0128 called VETEC ( Vero
  cytotoxin producing ) (Viteka ?)

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• B.Enterotoxigenic E coli ( ETEC)
• Common cause for travelers diarrhoea, and watery
  diarrhoea in children.
• Colonisation factor facilitates the attachment to
  the
• intestinal epithelium.
• Some ETEC produces heat labile exotoxin LT and
  heat stable or either of the toxins
• LT has two sub units A B
• Action -Activate Adenylate cyclase
• Increase local CAMP
• Intense, prolonged hypersecretion of water
  ,
• Lumen of gut fill with water
• Hypermobility and diarrhoea results.

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• LT is antigenic and cross reacts with the
  enterotoxin of Vibrio cholerae.

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• Some ETEC produces heat stable enterotoxin
  STa/b
• STa activates guanylyl cyclase.
• STb activates cyclic nucleotides.
• Releases water

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• C. Enterohemorrhagic E coli ( EHEC)
• Produce verotoxin which has similarities to
• Shiga toxin
• Associated with hemorrhagic colitis, severe
  form of diarrhoea.
• Hemolytic uremic syndrome Disease can be
  prevented by thorough cooking.

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• D.Enteroinvasive E coli (EIEC)
• Produces disease similar to shigellosis.
• In adults this has been isolated with Shigella
• Commonly affect children in developing countries,
• and travelers.
• Disease is due to invasion into mucosal cells of
  the intestine
• multiply inside the cells and destruction
  /inflammation/ulceration
• diarrhoea with blood
• EIEC are nonlactose fermenter,or late lactose
  fermenter
• and non motile.

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• E. Enteroaggregative E coli (EAEC)
• Produce acute/chronic diarrhoea in persons in
  developing countries.
• Sepsis When normal host defense is poor
  ,sepsis can
• happen.Common in new born babies whose IgM
  level is low.

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Treatment of E.coli related diarrhoea

• 1st Line
• Nitrofurantoin
• Nalidixic acid
• Norfloxacin ABST SHOULD BE DONE
• Ampicillin
• Cotrimoxazole
• 2nd line
• Ciprofloxacin/Ceftriaxone/Cefuroxime
• Gentamicin

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• Meningitis
• E coli and Gp.B Strept. are the leading causes
  for
• meningitis in infants.
• K1 antigen is responsible for meningitis
• K1 cross reacts with the Gp.B capsular
• polysaccharides of N meningitides.

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Pneumonia

• 25 of gram -ve pneumonia with 50 mortality
• Usually broncho pneumonia
• High level of resistance to Ampicillin
  /Cotrimoxazole

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• Klebsiella
• K pneumoniae
• Present in respiratory tract and feces of about
  5 of
• normal individuals.
• Can cause bacterial pneumonia.
• Produce extensive hemorrhagic necrotising
  consolidation of lungs.

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UTI and focal infections in debilitated pts.
Hospital acquired infections due to K
pneumoniae K oxytoca K rhinoscleromatis
produces rhinoscleroma, condition with
destructive granuloma of the nose and pharynx.
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• Enterobacter aerogenus
• Capsulated
• Free living in the intestine
• Cause UTI and sepsis.
• Serratia
• Common opportunistic pathogen in hospital pts.

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Cause pneumonia, bacterimia, endocarditis.
Often resist to aminoglycosides and penicillin.
Treatment-Third generation Cephalosporines.
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• Proteus
• Pathogenic only when the bacteria leave the
  intestinal tract
• Cause UTI, bacteremia, Pneumonia.
• Ex.P vulgaris

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• Proteus produce urease-Alkaline urine
• Stone formation
• Rapid motility of the organism facilitates the
  invasion
• Morganella morganii is an important nosocomial
  pathogen.
• Treatment-Penicillin,Aminoglycosides,Cephalosporin
  es

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Diagnostic tests 1.Specimens-Urine, blood, pus,
CSF, Sputum, stools 2.Smear 3.Culture blood
agar Immunity is not satisfactory. Management No
single specific therapy available Sulfonamides ma
rked antibacterial effect Ampicillin on
enterics Cephalosporines Fluoroquinolone Aminoglyc
oside
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ABST is essential Predisposing factors to be
corrected surgically. EgObstructions- UTI
Perforated abdominal organs Diarrhoea fluid
replacement Bacterimia Rapid Antibiotic
therapy fluid replacement Treatment for
DIC
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• Travelers diarrhoea
• Bismuth subsalicilate suspension inactivate
• E coli toxin
• Tetracycline as prophylaxis
• Food and water sanitation

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• SHIGELLA
• Natural habitat intestinal tract of humans/other
• primates
• Exclusively of parasites of human or primates
• BLOODY MUCOUS DYSENTRY

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• Morphology and identification
• Slender Gram -ve rods
• Facultative anaerobes
• All Shigellae ferment glucose not lactose
• S sonnei ferments lactose also.

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• Antigenic structure
• Complex, there are more than 40 sero types based
  on their LPS of somatic O antigen
• There are four gps based on somatic O
• A
• B
• C
• D

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• Pathogenesis
• Infection almost always limited to GIT
• Blood invasion is rare
• Highly communicable

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• Infective dose 103 Organisms (Salmonella
  Vibrio 105-108) - pretty small
• Invade mucosal epithelial cells by induced
  phagocytosis,
• escape from phagocytic vacuole multiply and
  spread with in the cell and adjacent cells.

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• Microabscess in the large intestine and terminal
  ileum-necrosis-ulceration -bleeding.
• Formation of pseudomembrane in ulcerated areas
  lead to scarring

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Toxins

• Endotoxins - after autolysis, causes diarrhoea
  and ulcers
• Exotoxins - acts as a enterotoxin - acts on
  mucosa ---transudation of fluids
• -acts as neurotoxin -
  polyneuritis/coma/meningism

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• Common pathogenic species
• S dysenteriae (A)
• S flexneri (B)
• S boydii (C)
• S sonnei (D)

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Shigella Glucose
Acid only
Acid and gas
A,B (except type 6), C,D
Sh. flexneri type 6
Mannitol
Indole -ve
Fermented
Non-fermented
Gps BCD
GpA
OVERLAPPING SPECIES DIFFERENT TYPES
Indole
Lactose
-ve B,C
ve at 3-8 days GpD Sh sonnei
ve Sh. dysenteriae 2,7,7
-ve Sh. dysen 1,3,4,5,6
Indole
ve
-ve
Sh, flexneri/Sh. boydii
Sh. boydii
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• Clinical features
• Incubation period 1-2 days.
• Sudden onset of
• abdominal pain fever and
• watery diarrhoea,
• mucus and bloody stools.
• fever diarrhoea subsides 2-5 days.
• loss of water - dehydration.
• Chronic carrier status may result.

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Animal pathogenicity

• Oral administration
• Normally does not cause true dysenteric lesions
• Sh. flexneri 1010 sever dysentery in monkeys
• IV administration
• 0.01mg Sh. dysenteriae sever diarrhoea in
  rabbits

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Dysentery carriers

• There are healthy carriers in the community
• This will happen after an attack
• Will excrete in the bacilli intermittently for
  few weeks - small proportion can become
  persistent carriers

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LAB DIAGNOSIS Specimens - fresh stool/mucous
flakes/rectal swabs/Blood/serum Microscopy pus
cells /RBC/Macrophages
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Culture MacConkey agar - selective DCA S-S agar
selective Selenite F broth - for enrichment and
transport Colourless on MacConkey
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Biochemical Citrate -ve Urease -ve H2S
-ve Sh. sonnei KCN -ve Indole
ve MR ve
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• Slide agglutination
• Use of polyvalent antisera of three gps (ABC) and
  of gp D
• Monovalent antisera is being used when ve for
  polyvalent

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• Treatment
• Ciprofloxacin,Ampicillin,Tetracyclin,Trimethoprim
• Sulfamethoxasole, Chloramphenicol
• Transmission by food, fingers, feces, flies.

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Salmonella Pathogenic when acquired through
oral route. Transmitted from animals animal
products. Produce A. Enteric
fever B. Enteritis/Enterocolitis
C. Systemic infections
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• Sources of in infection
• contaminated water
• contaminated dairy products
• shellfish
• dried or frozen eggs
• meat and meat products of infected animals
• Household pets

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• Morphology
• vary in length.
• motile with peritrichous flagellae.
• never ferment lactose or sucrose
• Usually produce H2S, survive freezing in water.
• Resist chemicals.

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Antigenic structure Antigens O H K - Vi Ag
invasiveness
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• Classification - Complex -
• Kauffmann White Scheme
• Ex S typhi
• S. paratyphi A/B India and Asian
• S. choleraesuis
• S. typhimurium
• S. enteritidis
• SO MANY OTHER SPECIES

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Toxin

• LPS - endotoxin

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• Pathogenesis
• Almost always enter orally with contaminated
• S. typhi/S. parathyphi A/B - in humans
• Majority of Salmonella infect animals man is the
  secondry host
• food and drink.

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• Infective dose 105-108 - high
• Resist infection by the host via
• gastric acidity, normal flora ,Local
  immunity.

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• Enteric fever (Typhoid fever)
• Important pathogen - S typhi/
• S. paratyphi A/B/C
• Fever/ malaise/ headache /constipation
  bradycardia / myelgia occur.

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• INCUBATION STAGE
• Incubation period 10-14 days
• Faecal oral route
• Most of the cells will get killed
• ID should be high
• Reach the duodenum
• Multiply in alkaline medium
• adhere to villi
• to the sub mucous coat
• will be phagocytosed by Macro and Neutro

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• Virulent bacilli resist intracellular killing and
  multiply
• Enters the mesenteric lymhnodes and multiply
  there and then to the blood (primary bacteraemia)
  1-7 days
• bacilli will be cleared by MPS in the
  liver/spleen/bone marrow/lungs/lymhnode

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• SEPTICAEMIC STAGE
• Primary bacteraemia - where bacilli will be
  multiply in the cells of MPS
• 10th day parasitised cells undergo necrosis leads
  to seondry bacteramia, results in clinical
  symptoms thats about on the 14th day after the
  ingestion
• some bacilli lyse and release endotoxins
• bacteraemia and toxaemia causes fever and other
  signs

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• STAGE OF LOCALIZATION
• Bacteraemia-gall bladder/liver/spleen/bone
• bacilli can be discharge into the intestine from
  the gall bladder and cause inflammation of the
  Payers patches in the intstine and lymphoid
  follicles
• Necrosis/sloughing---ulcers--haemorrhage

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• Severe mental clouding
• headache
• anorexia -cannot eat
• High fever (Step ladder pyrexia)
• spleen and liver enlargement
• Splenohepatomagaly
• Rose spots (1-2mm) on skin of chest and abdomen
  2nd and 3rd week

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• bacilli appear during 2nd and the 3rd week in
  stools - diagnostic
• 4th week in urine - diagnostic
• The disease lasts 4 to 5 weeks
• WBC normal or low
• Treatment - chloramphenicoal

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• Complications
• Intestinal hemorrhage perforation
• Hyperplasia and necrosis of Payers paches
• Hepatitis, focal liver necrosis
• gall bladder inflammation
• bone ,lungs and other organs can be affected.

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Bacteremia with focal lesions Commonly
associated with S cholerasius Blood culture ve
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• LABORATORY DIAGNOSIS
• 1. Isolation of the bacteria
• 2. Demonstration of antibodies
• 3. Demonstration of circulating antigens
• 4. Blood picture

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• Isolation of bacteria
• Specimens - stools/urine/blood
• Blood culture - before giving chloramphenicol
• - repeat the culture
• - 80-90 ve 1st week up to10days
• - ve during relapses
• - can culture bone marrow ve
• 1-2 days after drug therapy ?
  good
• -

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• When blood culturing is done there is diluting of
  the drug
• Stool and urine culture
• Stools - during the second and third week
• Urine - during the third and the fourth week,
  less frequently ve than stools
• Repeated culture is necessary when blood
  culture is -ve

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• Blood (5 - 10 ml)
• BHI
• Incubate 37 0C
• Subculture
• (18-24hrs/every 2nd day for 7days)
• MacConkey
• Stools and urine first should be cultured in
  enrichment media

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• Serological test
• Detection of antibodies to H and O antigens
• Widal test
• Antibodies appear at the end of the first week
• Rises during the 3rd week of the enteric fever
• Two specimens are taken at interval of 7 to 10
  days

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Interpretation of Widal test

• 1. Antibody appears at the end of 1st week/rises
  during 2nd and 3rd/steady at the 4th week then
  decline
• 2. Four fold rise of both H and O antibody in an
  interval of 7 - 10 days (between 1st and the 3rd
  week is highly significant)

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• Treatment
• Antimicrobials - Ampicillin
• TrimethoprimSulfamethoxasole
• 3rd generation Cephalosporines

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• Paratyphoid fever
• Fever is milder, shorter period
• IP is short

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• Enterocolitis
• Common manifestation of Salmonella
• Common pathogen is S typhimurium
• 8-48 hrs after ingestion
• nausea/ headache/ vomiting and profuse
  diarrhoea,
• low grade fever Resolution 2-3 days.
• Inflammatory lesions in bowel are present

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• Bacterimia rare
• Blood culture -ve
• Stools remain ve for sometime after recovery

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Diagnosis 1.Faeces, vomitus, food stuffs
(mainly a single source) 2. Convalescent serum
often agglutinates the suspension of casual
serotype
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• Prevention and control
• Sanitation
• Thorough cooking
• Carriers should not handle food
• Vaccination not successful long-term.