enterobacteriaceae
DESCRIPTION
descriptionTRANSCRIPT
EnterobacteriaceaeEnterobacteriaceae
Habitat digestive tube(colon) of human and
animals 150 Species Facultative anaerobes Diarrheal illnesses 3 million death/year 4 billion infectoions/ worldwide
Enterobacteriaceae
Classification – more than15 different genera Escherichia Shigella Edwardsiella Salmonella Citrobacter Klebsiella Enterobacter Hafnia Serratia
Enterobacteriaceae
ProteusProvidenciaMorganellaYersiniaErwiniaPectinobacterium
Family Enterobacteriaceae
(nonmotile)
(nonmotile)
True pathogen
True pathogen
True pathogen
Certain E .coli strains can be considered true pathogens
Morphology and General Characteristics
Are facultative anaerobes Gram-negative, non-sporing, rod shaped bacteria If motile, motility is by peritrichous flagella(Except
Shigella & Klebsiella) Many are normal inhabitants of the intestinal tract of
man and other animals Some are enteric pathogens and others are urinary or
respiratory tract pathogens Differentiation is based on biochemical reactions and
differences in antigenic structure
Morphology and Physiology
Short gram-negative rods.
Facultative anaerobes.
Grow readily and rapidly on
simple media.
K. pneumoniae
Klebsiella spp. have large capsule
(form large and very mucoid colonies);
those of Enterobacter have smaller
capsule; the others produce diffusible
slime layers (form circular, convex and
smooth colonies).
ENTEROBACTERIACEAE PHYSIOLOGY
Glucose is fermented with strong acid formation and often gas
Reduce nitrates to nitrite Do not liquify alginate Oxidase negative Basis for speciation within a family
- differences in carbohydrate they ferment- variations in end-product production
- variation in substrate utilization
EnterobacteriaceaeOpportunistic pathogens
Escherichia coli
Klebsiella pneumoniae
Enterobacter aerogenes
Serratia marcescens
Proteus spp.
Providencia spp.
Citrobacter spp.
Obligate pathogens
Salmonella spp.
Shigella spp.
Yersinia spp.
Some E. coli strains
Sepsis
Meningitis
UTI
Diarrhea
Pneumonia
Incidence of Enterobacteriaceae Associated with Bacteremia
Sites of Infections with Members of the Enterobacteriaceae
CULTURAL CHARACTERISTICS
On non differential or nonselective media blood agar or infusion agar
- no species distinction- appear as moist, smooth, gray
colonies Selective media -To isolate Shigella and
salmonella from fecal matter Differential media – selectively inhibit gram-
positive organisms and to separate enterics in broad categories
Modes of Infection• Contaminated food and water (Salmonella spp.,
Shigella spp., Yersinia enterocolitica, Escherichia coli O157:H7)
• Endogenous (urinary tract infection, primary bacterial peritonitis, abdominal abscess)
• Abnormal host colonization (nosocomial pneumonia)
• Transfer between debilitated patients
• Insect (flea) vector (unique for Yersinia pestis)
Urinary Tract Infection, Pneumonia
• Escherichia coli, Klebsiella pneumoniae, Enterobacter spp., and Proteus mirabilis
• Pneumonia: Enterobacter spp., Klebsiella pneumoniae, Escherichia coli, and Proteus mirabilis• Wound Infection: Escherichia coli, Enterobacter spp., Klebsiella pneumoniae, and Proteus mirabilis
• Bacteremia: Escherichia coli, Enterobacter spp., Klebsiella pneumoniae, and Proteus mirabilisIntestinal Infection
• Shigella sonnei (serogroup D)• Salmonella serotype enteritidis• Salmonella serotype typhimurium• Shigella flexneri (serogroup B)• Escherichia coli O157:H7• Yersinia enterocolitica
MacConkey (MAC) Agar
Eosin Methylene Blue (EMB) Agar (Levine)
Antigenic StructureAntigenic Structure
– Most are motile by Most are motile by peritrichous flagella peritrichous flagella ----HH antigens. antigens.
– Capsule – Capsule – KK antigen (antigen ( ViVi for Salmonella).for Salmonella).– Cell envelope (wall)Cell envelope (wall)– LPS (endotoxin) –LPS (endotoxin) –
OO antigen. antigen. – various outer various outer
membrane proteins.membrane proteins.– Pili Pili - various antigen - various antigen
types, some encoded types, some encoded by plasmids by plasmids
Pathogenesis and Immunity
Common virulence factors
Type III secretion systems: possessed by some Enterobacteriaceae
pathogens, e.g., E. coli, Yersinia, Salmonella, and Shigella; facilitate
transport of bacterial virulence factors directly into host cells.
Endotoxin (Lipid A of LPS)
Capsule
Antigenic phase variation
Acquisition of growth factors (e.g. Fe)
Resistance to serum killing
Antimicrobial resistance
HE Agar: Growth of Enteric Pathogens and Commensals
Escherichia coliEscherichia coli Toxins: two types of enterotoxin; Shiga-type toxin;
Enteroaggregative ST-like toxin; Hemolysins; Endotoxin
Virulence factors that protect the bacteria from host defenses: Capsule/Iron capturing ability (enterochelin)
E. coli
May be hemolytic on CBA – more common in pathogenic strains
KEY tests for the normal strain: TSI is A/A + gas LIA K/K Urea – Indole + Citrate – Motility +
There is an inactive biotype that is anaerogenic, lactose –, and nonmotile.
Enteropathogenic Enteropathogenic E. coliE. coli fever infant diarrhea vomiting nausea non-bloody stools Destruction of surface microvilli loose attachment
mediated by bundle forming pili (Bfp); Stimulation of intracellular calcium level; rearrangement of intracellular actin,
Enterotoxigenic Enterotoxigenic E. coliE. coli A watery diarrhea, nausea, abdominal cramps and low-
grade fever for 1-5 days. Travellers diarrhea and diarrhea in children in
developing countries Transmission is via contaminated food or water.
E.coli-E.coli-Enteroinvasive (EIEC)Enteroinvasive (EIEC) The organism attaches to the intestinal mucosa via pili Outer membrane proteins are involved in direct
penetration, invasion of the intestinal cells, and destruction of the intestinal mucosa.
There is lateral movement of the organism from one cell to adjacent cells.
Symptoms- fever,severe abdominal cramps, malaise, and watery diarrhea followed by scanty stools containing blood, mucous,& pus.
resembles shigellosisE.coli-E.coli-c. Enteropathogenic (EPEC)c. Enteropathogenic (EPEC)
Malaise and low grade fever diarrhea, vomiting, nausea, non-bloody stools
Bundle forming pili are involved in attachment to the intestinal mucosa.
This leads to changes in signal transduction in the cells, effacement of the microvilli, and to intimate attachment via a non-fimbrial adhesion called intimin.
This is a problem mainly in hospitalized infants and in day care centers.
Enterohemorrhagic (EHEC) Enterohemorrhagic (EHEC)
Hemorrhagic – bloody, copious diarrhea– few leukocytes – afebrile
hemolytic-uremic syndrome – hemolytic anemia– thrombocytopenia
(low platelets)– kidney failure
• Usually O157:H7
Transmission electron micrograph
Enteroaggregative Enteroaggregative E. E. coli coli
a cause of persistent, watery diarrhea with vomiting and dehydration in infants.
That is autoagglutination in a ‘stacked brick’ arrangement.
the bacteria adheres to the intestinal mucosa and elaborates enterotoxins (enteroaggregative heat-stable toxin, EAST).
The result is mucosal damage, secretion of large amounts of mucus, and a secretory diarrhea.
ShigellaShigella
Shigella species
Shigella Contains four species that differ antigenically and, to a lesser
extent, biochemically. S. dysenteriae (Group A) S. flexneri (Group B) S. boydii (Group C) S. sonnei (Group D) bacillary dysentery, shigellosis, bloody feces, intestinal pain, pus
Biochemistry TSI K/A with NO gas LIA K/A Urea – Motility - All ferment mannitol except S. dysenteriae S. sonnei may show delayed lactose fermentation
Shiga toxinShiga toxin1. Chromosomally encoded
2. Neurotoxic
3. Enterotoxic
4. Cytotoxic
EnterotoxicityEnterotoxicity can make the disease clinicallyappear as a diarrheadiarrhea.
The toxin inhibits protein synthesistoxin inhibits protein synthesis (acting on the 60S ribosome and lysing 28S rRNA).
Clinical significanceClinical significance
man only "reservoir"man only "reservoir"mostly young children mostly young children
– fecal to oral contactfecal to oral contact– children to adultschildren to adults
transmitted by adult food handlerstransmitted by adult food handlers– unwashed handsunwashed hands
Diagnosis of Shigella infectionDiagnosis of Shigella infection
Specimen: stool. Culture and Identification Quick immunological methods:
1. Immunofluorescent “ball” test;
2. Coagglutination.
XLD Agar: Growth of Shigella and Proteus
Only a few types that are commonly associated with characteristic human diseases -
1. 1. S. enteritidisS. enteritidis
2. 2. S. cholerae-suisS. cholerae-suis
3. 3. S. typhiS. typhi
SalmonellaSalmonella
several syndromes including gastroenteritis, enteric (typhoid) fever or septicemia
Salmonella
Biochemistry TSI K/A + gas and H2S: S. typhi produces only a small
amount of H2S and no gas , and S. paratyphi A produces no H2S
LIA K/K with H2S with S. paratyphi A giving K/A results Urea – Motility + Citrate +/- Indole -
Virulence factors Endotoxin – may play a role in intracellular survival Capsule (for S. typhi and some strains of S. paratyphi) Adhesions – both fimbrial and non-fimbrial
Salmonella typhiSalmonella typhi• The organism is transmitted from:
1. a human reservoir 1. a human reservoir 2. in the water supply (if poor sanitary conditions)2. in the water supply (if poor sanitary conditions) 3. in contaminated food3. in contaminated food
The antigenic structures of salmonellae used in serologic typingThe antigenic structures of salmonellae used in serologic typing
Virulence factorsVirulence factors Endotoxin – may play a role in intracellular survival Capsule (for S. typhi and some strains of S. paratyphi) Adhesions – both fimbrial and non-fimbrial Type III secretion systems and effector molecules – 2 different systems may be
found:– One type is involved in promoting entry into intestinal epithelial cells
– The other type is involved in the ability of Salmonella to survive inside macrophages Outer membrane proteins - involved in the ability of Salmonella to survive
inside macrophages Flagella – help bacteria to move through intestinal mucous Enterotoxin - may be involved in gastroenteritis Iron capturing ability
XLD Agar: Appearance of Salmonella
DDiagnosisiagnosis
A. SpecimensA. Specimens a) Enteric fever: blood, bone marrow, stool, a) Enteric fever: blood, bone marrow, stool,
urine.urine. b) Food poisoning: stool, vomitus, suspected food.b) Food poisoning: stool, vomitus, suspected food. c) Septicemia: blood. c) Septicemia: blood. B. Culture and identificationB. Culture and identification C. Widal testC. Widal test
Klebsiella
NF of GI tract, but potential pathogen in other areas TSI A/A + gas LIA K/K Urea + Citrate + MR-, VP+ Motility - Has both O and K antigens
Klebsiella
Virulence factors Capsule Adhesions Iron capturing ability
Clinical significance Causes pneumonia, mostly in immunocompromised hosts.
Permanent lung damage is a frequent occurrence (rare in other types of bacterial pneumonia)
A major cause of nosocomial
infections such as septicemia and
meningitis
K.Pneumoniae On BA
K.Pneumoniae on BA and MAC
Proteus Proteus General characteristics: “swarming” phenomenon General characteristics: “swarming” phenomenon
on nonselective agaron nonselective agar (P.vulgaris; P.mirabilis and (P.vulgaris; P.mirabilis and P.myxofaciens) P.myxofaciens)
P.vulgaris strains (OX-19, OX-K, OX-2)have P.vulgaris strains (OX-19, OX-K, OX-2)have common antigen with Rickettsia (Weil-Felix test). common antigen with Rickettsia (Weil-Felix test).
urinary tract infections; food poisoningurinary tract infections; food poisoning..
Proteus spp.
Some enteric bacteria are motile.
Klebsiella species are not motile,
while Proteus species move very
actively by means of peritrichous
flagella, resulting in "swarming"
on solid medium.
Some strains of E. coli produce
hemolysis on blood plates.
CITROBACTERCITROBACTERResident of soil, water, stool• C.freundii• UTI and bacteremia
SerratiaSerratia
Serratia
A free-living saprophyte TSI A/A or K/A; +/- gas (does not ferment lactose) LIA usually K/K Citrate + Motility + Urea +/- Has been found in RT and UT infections Is resistant to many antimicrobics
Special Features:
Used in the differentiation of genera and species. e.g. E. coli (+) from Klebsiella (-).
Positive teste.g. E. coli
Negative teste.g. Klebsiella
IIndole testndole test
PositiveKlebsiella, Enterobacter
NegativeE. coli
Citrate Utilization Test
Urease Test
Positive test
Negative test
MMR/R/VVP testP testResults
Methyl Red test Voges-Proskauer test
Red: Positive MR (E. coli)
Yellow or orange: Negative MR (Klebsiella)
Pink: Positive VP (Klebsiella)
No pink: Negative VP (E. coli)
Gram Gram stainstain
OxidaseOxidase Nitrate Nitrate reductasereductase
O/FO/F MacConMacConkeykey
SSSS EMBEMB
E. coliE. coli -ve rod-ve rod -ve-ve +ve+ve O+/F+O+/F+ LFLF LFLF Metallic Metallic sheensheen
CitrobacterCitrobacter -ve rods-ve rods -ve-ve +ve+ve O+/F+O+/F+ LFLF LFLF DarkDark
KlebsiellaKlebsiella -ve rods-ve rods -ve-ve +ve+ve O+/F+O+/F+ LFLF LFLF DarkDark
EnterobacterEnterobacter -ve rods-ve rods -ve-ve +ve+ve O+/F+O+/F+ LFLF LFLF DarkDark
SalmonellaSalmonella -ve rods-ve rods -ve-ve +ve+ve O+/F+O+/F+ NLFNLF NLF/NLF/H2SH2S
ColorlessColorless
ShigellaShigella -ve rods-ve rods -ve-ve +ve+ve O+/F+O+/F+ NLFNLF NLFNLF ColorlessColorless
ProteusProteus -ve rods-ve rods -ve-ve +ve+ve O+/F+O+/F+ NLFNLF NLF/NLF/H2SH2S
ColorlessColorless
Summary of morphology, cultural characteristics, and biochemical reactions of Enterobacteriaceae
TSITSI IndoleIndole MRMR VPVP CitrateCitrate UreaseUrease MotilityMotility
E. coliE. coli A/A/-A/A/- +ve+ve +ve+ve -ve-ve -ve-ve -ve-ve MotileMotile
Citrobacter Citrobacter freundiifreundii
A/A/-A/A/- +ve+ve +ve+ve -ve-ve +ve+ve -ve-ve MotileMotile
Klebsiella Klebsiella pneumoniaepneumoniae
A/A/-A/A/- -ve-ve -ve-ve +ve+ve +ve+ve +ve+ve Non Non motilemotile
Enterobacter Enterobacter cloacaecloacae
A/A/-A/A/- -ve-ve -ve-ve +ve+ve +ve+ve +ve+ve MotileMotile
Salmonella Salmonella typhityphi
A/Alk/+A/Alk/+ -ve-ve +ve+ve -ve-ve +ve+ve -ve-ve MotileMotile
Shigella Shigella boydiiboydii
A/Alk/-A/Alk/- -ve-ve +ve+ve -ve-ve -ve-ve -ve-ve Non Non motilemotile
ProteusProteus mirabilismirabilis
A/Alk/+A/Alk/+ -ve-ve +ve+ve -ve-ve +ve+ve +ve+ve MotileMotile
SwarwingSwarwing
Summary of morphology, cultural characteristics, and biochemical reactions of Enterobacteriaceae
Oxidase TestOxidase Test
PositiveNegative
Pseudomonas Enterobacteriaceae
Nitrate test: +ve further reduction to N2
Growth on cetrimide agar: Pale colonies with green pigmentation
MacConkey’s agar & TSI
Lactose fermenter
Pink colonies on MacConkey& acidic butt and slant on TSI
colorless colonies on MacConkey& acidic butt alkaline slant onTSI
Lactose non-fermenter
IMViC test& EMB
IMViC++ - -& black colonies with metalic shines on EMB
E.coli
IMViC- - ++
Klebsiella
No H2S production(no blacking in TSI)
H2S production(blacking in TSI)
ShigellaUrease production
+ve
Proteus
-ve
SS agarcolorless colonies with black centers
Salmonella
O/F test: O+/F-
Motility
Not motileMotile
Enterobacter
