ENTEROBACTERIACEAEENTEROBACTERIACEAE

Morphology & IdentificationMorphology & Identification

• Gram-negative non-spore forming rods. When motile, by peritrichous flagella.

• Primarily normal flora of gastrointestinal tract. E. coli>Klebsiella>Proteus>Enterobacter

• Free living, also transient colonizers of skin.• Facultative anaerobes: mixed acid fermentation • All ferment glucose; all reduce nitrates to nitrites; all oxi

dase negative. • Lactose fermentation: normal flora positive and pathog

ens negative.• Primary isolation media include eosin-methylene-blue

(EMB) and MacConkey agar. • Differential selective media for specific organisms

including dyes and bile salts. (Salmonella-Shigella (SS) medium, bismuth sulfite media.)

ClassificationClassification~29 genera, over 100 species.

– Escherichia– Shigella– Edwardsiella– Salmonella– Citrobacter– Klebsiella– Enterobacter– Hafnia– Serratia

– Proteus– Providencia– Morganella– Yersinia– Erwinia– Pectinobacterium

Antigenic StructureAntigenic Structure

– Most are motile by peritrichous flagellaMost are motile by peritrichous flagella -- --HH a antigens. ntigens.

– 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 membrane proteins.various outer membrane proteins.– Pili - various antigen types, some encoded bPili - various antigen types, some encoded b

y plasmids y plasmids

鞭毛抗原（ H ）

菌体抗原 (O)

K 或 Vi 抗原

EnterobacteriaceaeEnterobacteriaceae- Opportunistic disea- Opportunistic disea

sesses Citrobacter EnterobacterEscherichiaHafniaMorganellaProvidenciaSerratia

– septicemia, septicemia, – pneumonia, pneumonia, – meningitismeningitis– urinary tract infectionsurinary tract infections

EnterobacteriaceaeEnterobacteriaceae:: gastrointestinal diseasesgastrointestinal diseases

– Escherichia coliEscherichia coli – SalmonellaSalmonella– ShigellaShigella – Yersinia entercoliticYersinia entercolitic

aa

• community acquired • otherwise healthy people

– Klebsiella pneumoniae * respiratory diseases* prominent capsule

–urinary tract infection–fecal contamination *E. coli*Proteus

– urease (degrades urea)urease (degrades urea)– alkaline urinealkaline urine

EnterobacteriaceaeEnterobacteriaceae

Escherichia coliEscherichia coli

Escherichia coliEscherichia coli• Toxins: two types of enterotoxin; Shiga-typ

e toxin; Enteroaggregative ST-like toxin; Hemolysins; Endotoxin

• Type III secretion system • Adhesions –colonization factors ; both pili

or fimbriae ;non-fimbrial factors involved in attachment. There are at least 21 different types of adhesions.

• Virulence factors that protect the bacteria from host defenses: Capsule/Iron capturing ability (enterochelin)

• Outer membrane proteins

E. coliE. coli fimbriae fimbriae

mannosemannose

Type 1 Type 1

• galactose galactose – glycolipids glycolipids – glycoproteins glycoproteins

P P

E.coli-urinary tract E.coli-urinary tract infection infection Is the leading cause of urinary tract i

nfections which can lead to acute cystitis (bladder infection) and pyelonephritis (kidney infectio

n).

E.coli-Meningitis and SepsisE.coli-Meningitis and Sepsis

• Neonatal meningitis – is the leading cause of neonatal meningitis and septicemia with a high mortality rate. Usually caused by strains with the K1 capsular antigen.

EnteroEnteroppathogenic athogenic E. coliE. coli

• fever• infant diarrhea• vomiting • nausea • non-bloody stools • Destruction of surface microvilli1. loose attachment mediated by bun

dle forming pili (Bfp); 2. Stimulation of intracellular calcium

level; 3. rearrangement of intracellular acti

n,

EnteroEnterottoxigenic oxigenic E. coliE. coli

• AA watery diarrhea, nausea, abdomina watery diarrhea, nausea, abdominal cramps and low-grade fever for 1-5 l cramps and low-grade fever for 1-5 days. days.

• TTravellers diarrhearavellers diarrhea and and diarrhea in chdiarrhea in children in developing countriesildren in developing countries

• Transmission is via contaminated foTransmission is via contaminated food or water.od or water.

EnteroEnterottoxigenic oxigenic E. coliE. coli

• diarrhea like cholera diarrhea like cholera • milder milder • nursery travellers diarrhea nursery travellers diarrhea • caused by LT, ST, or LT/ST.caused by LT, ST, or LT/ST.

EnteroEnterottoxigenic oxigenic E. coliE. coli • Heat labile toxinHeat labile toxin

– like choleragenlike choleragen– Adenyl cyclase activated Adenyl cyclase activated – cyclic AMP cyclic AMP – secretion water/ionssecretion water/ions

• Heat stable toxinHeat stable toxin– Guanylate cyclase activated Guanylate cyclase activated – cyclic GMPcyclic GMP– uptake water/ionsuptake water/ions

LT vs ST activity

E.coli-E.coli-EnteroEnteroiinvasive (EIEC)nvasive (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 include fever,severe abdominal cramps, malaise, and watery diarrhea followed by scanty stools containing blood, mucous, and pus.

• resembles shigellosis

EnteroEnteroiinvasive nvasive E. coliE. coli (EIE (EIECC))

• Dysentery- resembles shigellosis- elder children and adult diarrhea

E.coli-E.coli-c. Enteroc. Enteroppathogenic (EPEC)athogenic (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.

E.coli-E.coli-d. Enterod. Enterohhemorrhagic (EHEC)emorrhagic (EHEC)

• Hemorrhagic – bloody, copious diarrhea– few leukocytes – afebrile

• hemolytic-uremic syndrome – hemolytic anemia– thrombocytopenia (low platelets)– kidney failure

EnteroEnterohhemorrhagic emorrhagic E. coliE. coli

• Usually O157:H7

Transmission electron micrograph

Enterohemorrhagic Enterohemorrhagic E. coliE. coli

• Vero toxin Vero toxin – “ “shiga-like”shiga-like”

• Hemolysins Hemolysins

• younger than 5 years old,causing hemorrha

gic colitis

Enteroaggregative E. coli 肠集聚型大肠杆菌

• 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.

E.coli-E.coli-Enteroaggregative (EAggEC)Enteroaggregative (EAggEC)

• Mucous associated autoagglutinins cause aggregation of the bacteria at the cell surface and result in the formation of a mucous biofilm.

• The organisms attach via pili and liberate a cytotoxin distinct from, but similar to the ST and LT enterotoxins liberated by ETEC.

• Symptoms incluse watery diarrhea, vomiting, dehydration and occasional abdominal pain.

Various Types of E. coli

Summary of E.coli strains that cause gastr

oenteritis.

Sanitary significanceSanitary significance

• Totoal bacterial number: number of Totoal bacterial number: number of bacteria contained per ml or gm of thbacteria contained per ml or gm of the sample; the standard of drinking we sample; the standard of drinking water is less than 100.ater is less than 100.

• Coliform bacteria index: the number Coliform bacteria index: the number of coliform bacteria detected out per of coliform bacteria detected out per 1000 ml sample; the standard of drin1000 ml sample; the standard of drinking water is less than 3king water is less than 3

ShigellaShigella

ShigellaShigella

• S. flexneri, S. boydii, S. sonnei, S. flexneri, S. boydii, S. sonnei, S. dysenteriaeS. dysenteriae–bacillary dysenterybacillary dysentery

–shigellosisshigellosis• bloody fecesbloody feces

• intestinal painintestinal pain

• puspus

Genral features

• Pili. Pili.

• Most strains can not ferment lactMost strains can not ferment lactose; S. sonnei can slowly_ fermenose; S. sonnei can slowly_ ferment lactose.t lactose.

• According to O antigen, 4 groupsAccording to O antigen, 4 groups• Easily causing drug-resistence.Easily causing drug-resistence.

ShigellosisShigellosis

• within 2-3 dayswithin 2-3 days–epithelial cell damageepithelial cell damage

Shiga toxinShiga toxin• enterotoxicenterotoxic

• cytotoxiccytotoxic

• inhibits protein synthesisinhibits protein synthesis– lysing 28S rRNA

Shigella attachment and penetration

• WWithin 2-3 daysithin 2-3 days• EEpithelial cell damapithelial cell dama

gege

Clinical 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

Clinical significance• The infective dose required to cause infectio

n is very low (10-200 organisms).• There is an incubation of 1-7 days followed b

y fever, cramping, abdominal pain, and watery diarrhea (due to the toxin)for 1-3 days.

• This may be followed by frequent, scant stools with blood, mucous, and pus (due to invasion of intestinal mucosa).

• Is is rare for the organism to disseminate. • The severity of the disease depends upon the

species one is infected with. S. dysenteria is the most pathogenic followed by S. flexneri, S. sonnei and S. boydii.

Immunity

• SIgA.

Diagnosis of Shigella infection

• Specimen: stool.• Culture and Identification• Quick immunological methods:1. Immunofluorescent “ball” te

st; 2. Coagglutination.

Prevention

• streptomycin dependent (SD) dysentery vaccine.

Treating shigellosisTreating shigellosis

• manage dehydration• patients respond to antibiotics ,

Problem of drug-resistance– disease duration diminished

SalmonellaSalmonella

• Salmonellosis may present as one of several syndromes including gastroenteritis, enteric (typhoid) fever or septicemia.

The antigenic structures of salmonellae used in serologic typing

SalmonellaSalmonella• 2000 antigenic "types”2000 antigenic "types”• genetically single speciesgenetically single species

– S. entericaS. enterica

• disease categorydisease category – S. enteritidisS. enteritidis

– many serotypesmany serotypes

– S. cholerae-suisS. cholerae-suis– S. typhiS. typhi

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 • Type III secretion systems and effector molecules – 2 differ

ent systems may be found:– One type is involved in promoting entry into intestinal epithelia

l 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

Enteric or typhoid fever• Enteric or typhoid fever occurs when the bacEnteric or typhoid fever occurs when the bac

teria leave the intestine and multiply within cteria leave the intestine and multiply within cells of the reticuloendothelial system. ells of the reticuloendothelial system.

• The bacteria then re-enter the intestine, causiThe bacteria then re-enter the intestine, causing gastrointestinal symptoms. ng gastrointestinal symptoms.

• Typhoid fever has a 10-14 day incubation perTyphoid fever has a 10-14 day incubation period and may last for several weeks.iod and may last for several weeks.

• Salmonella typhi is the most common specieSalmonella typhi is the most common species isolated from this salmonellosis. s isolated from this salmonellosis.

• HHuman reservoiruman reservoir::carrier state common• CContaminated foodontaminated food::water supply water supply • PPoor sanitary conditions oor sanitary conditions

TyphoidTyphoid

•acute phase, gastroenteritis acute phase, gastroenteritis

gall bladdergall bladder–shedding, weeksshedding, weeks

SepticemiaSepticemia-occurs 10-14 days-occurs 10-14 days– lasts 7 dayslasts 7 days

gastrointenteritisgastrointenteritis

胆囊 --- 肠道 --- 粪排菌 /肠 壁淋巴组织肾 ----- 尿肝脾 ----- 肿大骨髓 ------ 受抑制皮肤 ---- 血栓出血 -- 玫瑰疹

伤寒和付伤寒的致病过程

伤寒和付伤寒沙门菌

小肠上部粘膜

肠系膜淋巴结

固有层淋巴结

进入血液 再次进入血液

第一次菌血症 第二次菌血症

Typhoid -TherapyTyphoid -Therapy

• AntibioticsAntibiotics

– essentialessential

• VaccinesVaccines

Vi (capsular) antigen Vi (capsular) antigen ::protectiveprotective

Salmonella gastroenteritis

• Salmonella gastroenteritis is the most commSalmonella gastroenteritis is the most common form of salmonellosis and generally requiron form of salmonellosis and generally requires an 8-48 hour incubation period and may laes an 8-48 hour incubation period and may last from 2-5 days. st from 2-5 days.

• Symptoms include nausea, vomiting and diarSymptoms include nausea, vomiting and diarrhea rhea ((non-bloody stoolnon-bloody stool)). Salmonella enteritidi. Salmonella enteritidis is the most common isolate.s is the most common isolate.

• poultrypoultry 家禽 , eggs, eggs. . no human reservoirno human reservoir• self-limiting (2 - 5 days)self-limiting (2 - 5 days)

Salmonella septicemia

• Salmonella septicemia (bacteremia) may be caused by any species but S. cholerae-suis is common. This disease resembles other Gram-negative septicemias and is characterized by a high, remittent fever with little gastrointestinal involvement.

Immunity (Immunity (S. typhiS. typhi))

• Vi (capsular) antigen Vi (capsular) antigen – protectiveprotective

DDiagnosisiagnosis

• A. SpecimensA. Specimens

• a) Enteric fever: blood, bone marrow, a) Enteric fever: blood, bone marrow, stool, urine.stool, urine.

• b) Food poisoning: stool, vomitus, sub) Food poisoning: stool, vomitus, suspected food.spected food.

• c) Septicemia: blood. c) Septicemia: blood.

• B. Culture and identificationB. Culture and identification

• C. Widal testC. Widal test

KlebsiellaKlebsiella

– NF of GI tract, but potential pathogen in other areas – Virulence factors

• Capsule• Adhesions• Iron capturing ability

– Clinical significance• Causes pneumonia, mostly in immunocompromised hos

ts. 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

KlebsiellaKlebsiella

• K. pneumoniae (Friedlander bacilli): maK. pneumoniae (Friedlander bacilli): may cause primary pneumonia, urinary tray cause primary pneumonia, urinary tract and wound infections, bacteremia, mct and wound infections, bacteremia, meningitis, etc.eningitis, etc.

• K. rhinoscleromatis: pathogen of granuK. rhinoscleromatis: pathogen of granumatous destruction of nose and pharynmatous destruction of nose and pharynx.x.

• K. ozaenae: causes chronic atrophic rhK. ozaenae: causes chronic atrophic rh

initis.initis.

Proteus Proteus • General characteristics: “swarming” phGeneral characteristics: “swarming” ph

enomenon on nonselective agarenomenon on nonselective agar (P.vulg(P.vulgaris; P.mirabilis and P.myxofaciens) aris; P.mirabilis and P.myxofaciens)

• Antigenic structure: O antigen (group-sAntigenic structure: O antigen (group-specific); H antigen (type-specific); certaipecific); H antigen (type-specific); certain P.vulgaris strains (OX-19, OX-K, OX-2)n P.vulgaris strains (OX-19, OX-K, OX-2)have common antigen with Rickettsia have common antigen with Rickettsia (Weil-Felix test). (Weil-Felix test).

• Clinical manifestations: Clinical manifestations: urinary tract inurinary tract infections; food poisoning.fections; food poisoning.