肠杆菌科e

ENTEROBACTERIACEAEENTEROBACTERIACEAE . Morphology all reduce nitrates to nitrites; all oxidase negative. lLactose fermentation: normal flora positive and pathogens negative. lPrimary isolation media include eosin-methylene-blue (EMB) and MacConkey agar. lDifferential selective media for specific organisms including dyes and bile salts. (Salmonella-Shigella (SS) medium, bismuth sulfite media.) ClassificationClassification 29 genera, over 100 species. 29 genera, over 100 species. Escherichia Shigella Edwardsiella Salmonella Citrobacter Klebsiella Enterobacter Hafnia Serratia Proteus Providencia Morganella Yersinia Erwinia Pectinobacterium Antigenic Antigenic StructureStructure Most are motile by peritrichous flagella -Most are motile by 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 membrane proteins.various outer membrane proteins. Pili - various antigen types, some encoded by Pili - various antigen types, some encoded by plasmids plasmids 鞭毛抗原（H ） 菌体抗原(O) K或Vi抗原 septicemia, septicemia, pneumonia, pneumonia, meningitismeningitis urinary tract infectionsurinary tract infections Citrobacter Enterobacter Escherichia Hafnia Morganella Providencia Serratia Opportunistic diseases Opportunistic diseases - -EnterobacteriaceaeEnterobacteriaceae EnterobacteriaceaeEnterobacteriaceae: : gastrointestinal diseasesgastrointestinal diseases Escherichia coli Escherichia coli Salmonella Salmonella ShigellaShigella Yersinia entercoliticaYersinia entercolitica Histocompatibility antigen (HLA) B27 Histocompatibility antigen (HLA) B27 Enterobacteriaceae *Salmonella *Shigella *Yersinia Not Not EnterobacteriaceaeEnterobacteriaceae * *CampylobacterCampylobacter * *ChlamydiaChlamydia Reiters syndromeReiters syndrome 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 urine alkaline urine EnterobacteriaceaeEnterobacteriaceae EnterobacteriaceaeEnterobacteriaceae gram negative facultative anaerobic rodsgram negative facultative anaerobic rods oxidase negative (no cytochrome oxidase) oxidase negative (no cytochrome oxidase) E. coli lactose positive not usually identified lactose positive sp. common, healthy intestine Shigella, Salmonella,Yersinia lactose negative identified FecesFeces other sites other sites identified biochemicallyidentified biochemically EnterobacteriaceaeEnterobacteriaceae SerotypesSerotypes l l reference laboratoryreference laboratory antigens antigens l l O (lipopolysaccharide) O (lipopolysaccharide) l l H (flagellar) H (flagellar) l l K (capsular) K (capsular) Escherichia coliEscherichia coli . Escherichia coliEscherichia coli lToxins: two types of enterotoxin; Shiga-type toxin; Enteroaggregative ST-like toxin; Hemolysins; Endotoxin lType III secretion system lAdhesions colonization factors ; both pili or fimbriae ;non-fimbrial factors involved in attachment. There are at least 21 different types of adhesions. lVirulence factors that protect the bacteria from host defenses: Capsule/Iron capturing ability (enterochelin) lOuter membrane proteins E. coliE. coli fimbriae fimbriae mannosemannose Type 1 Type 1 galactose galactose glycolipids glycolipids glycoproteins glycoproteins P P E.coli-urinary tract infection E.coli-urinary tract infection Is the leading cause of urinary tract infections which can lead toIs the leading cause of urinary tract infections which can lead to acute cystitis (bladder infection) and pyelonephritis (kidney infection). acute cystitis (bladder infection) and pyelonephritis (kidney infection). E.coli-Meningitis and SepsisE.coli-Meningitis and Sepsis lNeonatal meningitis is the leading cause of neonatal meningitis and septicemia with a high mortality rate. Usually caused by strains with the K1 capsular antigen. Enteropathogenic Enteropathogenic E. coliE. coli lfever linfant diarrhea lvomiting lnausea lnon-bloody stools lDestruction of surface microvilli 1. loose attachment mediated by bundle forming pili (Bfp); 2. Stimulation of intracellular calcium level; 3. rearrangement of intracellular actin, Enterotoxigenic Enterotoxigenic E. coliE. coli l l A A watery diarrhea, nausea, abdominal watery diarrhea, nausea, abdominal cramps and low-grade fever for 1-5 days. cramps and low-grade fever for 1-5 days. l l T Travellers diarrhearavellers diarrhea and and diarrhea in diarrhea in children in developing countrieschildren in developing countries l l Transmission is via contaminated food or Transmission is via contaminated food or water.water. Enterotoxigenic Enterotoxigenic E. coliE. coli l l diarrhea like cholera diarrhea like cholera l l milder milder l l nursery travellers diarrhea nursery travellers diarrhea l l caused by LT, ST, or LT/ST.caused by LT, ST, or LT/ST. Enterotoxigenic Enterotoxigenic E. coliE. coli l l Heat labile toxinHeat labile toxin like choleragenlike choleragen Adenyl cyclase activated Adenyl cyclase activated cyclic AMP cyclic AMP secretion water/ionssecretion water/ions l l Heat stable toxinHeat stable toxin Guanylate cyclase activated Guanylate cyclase activated cyclic GMPcyclic GMP uptake water/ionsuptake water/ions LT vs ST activityLT vs ST activity E.coli-E.coli-Enteroinvasive (EIEC)Enteroinvasive (EIEC) lThe organism attaches to the intestinal mucosa via pili lOuter membrane proteins are involved in direct penetration, invasion of the intestinal cells, and destruction of the intestinal mucosa. lThere is lateral movement of the organism from one cell to adjacent cells. lSymptoms include fever,severe abdominal cramps, malaise, and watery diarrhea followed by scanty stools containing blood, mucous, and pus. lresembles shigellosis Enteroinvasive Enteroinvasive E. coliE. coli (EIEC(EIEC) ) lDysentery -resembles shigellosis -elder children and adult diarrhea E.coli-E.coli-c. Enteropathogenic (EPEC)c. Enteropathogenic (EPEC) lMalaise and low grade fever diarrhea, vomiting, nausea, non-bloody stools lBundle forming pili are involved in attachment to the intestinal mucosa. lThis leads to changes in signal transduction in the cells, effacement of the microvilli, and to intimate attachment via a non-fimbrial adhesion called intimin. lThis is a problem mainly in hospitalized infants and in day care centers. E.coli-E.coli-d. Enterohemorrhagic (EHEC) d. Enterohemorrhagic (EHEC) lHemorrhagic bloody, copious diarrhea few leukocytes afebrile lhemolytic-uremic syndrome hemolytic anemia thrombocytopenia (low platelets) kidney failure Enterohemorrhagic Enterohemorrhagic E. coliE. coli Usually O157:H7 Transmission electron micrograph Enterohemorrhagic Enterohemorrhagic E. coliE. coli l l Vero toxin Vero toxin “shiga-like” “shiga-like” l l Hemolysins Hemolysins lyounger than 5 years old,causing hemorrhagic colitis Enteroaggregative Enteroaggregative E. coli E. coli 肠肠肠肠集聚型大集聚型大肠肠肠肠杆菌杆菌 la cause of persistent, watery diarrhea with vomiting and dehydration in infants. lThat is autoagglutination in a stacked brick arrangement. lthe bacteria adheres to the intestinal mucosa and elaborates enterotoxins (enteroaggregative heat-stable toxin, EAST). lThe result is mucosal damage, secretion of large amounts of mucus, and a secretory diarrhea. E.coli-E.coli-Enteroaggregative Enteroaggregative (EAggEC)(EAggEC) lMucous associated autoagglutinins cause aggregation of the bacteria at the cell surface and result in the formation of a mucous biofilm. lThe organisms attach via pili and liberate a cytotoxin distinct from, but similar to the ST and LT enterotoxins liberated by ETEC. lSymptoms incluse watery diarrhea, vomiting, dehydration and occasional abdominal pain. Various Types of E. coliVarious Types of E. coli Summary of Summary of E.coliE.coli strains that cause strains that cause gastroenteritis.gastroenteritis. Sanitary significanceSanitary significance l l Totoal Totoal bacterial bacterial number: number: number number of of bacteria bacteria contained contained per per ml ml or or gm gm of of the the sample; sample; the the standard standard of of drinking drinking water water is is less than 100.less than 100. l l Coliform Coliform bacteria bacteria index: index: the the number number of of coliform coliform bacteria bacteria detected detected out out per per 1000 1000 ml ml sample; sample; the the standard standard of of drinking drinking water is less than 3water is less than 3 Escherichia coli lGenetically E. coli and Shigella are genetically highly closely related. For practical reasons (primarily to avoid confusion) they are not placed in the same genus. Not surprisingly there is a lot of overlap between diseases caused by the two organisms. l1) Enteropathogenic E. coli (EPEC). Certain serotypes are commonly found associated with infant diarrhea. The use of gene probes has confirmed these strains as different from other groups listed below. There is a characteristic morphological lesion with destruction of microvilli without invasion of the organism that suggests adhesion is important. Clinically one observes fever, diarrhea, vomiting and nausea usually with non-bloody stools. l2) Enterotoxigenic E. coli (ETEC) produce diarrhea resembling cholera but much milder in degree. Also cause “travelers diarrhea“. Two types of plasmid-encoded toxins are produced. a) Heat labile toxins which are similar to choleragen (see cholera section below). Adenyl cyclase is activated with production of cyclic AMP and increased secretion of water and ions. b) Heat stable toxins; guanylate cyclase is activated which inhibits ionic and water uptake from the gut lumen. Watery diarrhea, fever and nausea result in both cases. l3) Enteroinvasive E. coli (EIEC) produce dysentery (indistinguishable clinically from shigellosis, see bacillary dysentery below). l4) Enterohemorrhagic E. coli (EHEC). These are usually serotype O157: H7. These organisms can produce a hemorrhagic colitis (characterized by bloody and copious diarrhea with few leukocytes in afebrile patients). Outbreaks are often caused by contaminated hamburger meat. The organisms can disseminate into the bloodstream producing systemic hemolytic-uremic syndrome (hemolytic anemia, thrombocytopenia and kidney failure). Production of Vero toxin (biochemically similar to shiga toxin thus also known as “shiga-like“) is highly associated with this group of organisms; encoded by a phage. Hemolysins (plasmid encoded) are also important in pathogenesis. lAs noted above, there are at least 4 etiologically distinct diseases. However, in the diagnostic laboratory generally the groups are not differentiated and treatment would be on symptomatology. Generally fluid replacement is the primary treatment. Antibiotics are generally not used except in severe disease or disease that has progressed to a systemic stage (e.g.hemolytic-uremia syndrome). Two major classes of pili are produced by E. coli : mannose sensitive and mannose resistant pili. The former bind to mannose containing glyocoproteins and the latter to cerebrosides on the host epithelium allowing attachment. This aids in colonization by E. coli. ShigellaShigella ShigellaShigella l l S. flexneri, S. boydii, S. sonnei, S. S. flexneri, S. boydii, S. sonnei, S. dysenteriaedysenteriae bacillary dysenterybacillary dysentery shigellosisshigellosis l l bloody fecesbloody feces l l intestinal painintestinal pain l l puspus Genral Genral featuresfeatures l l Pili. Pili. l l Most strains can not ferment Most strains can not ferment lactose; S. sonnei can slowly_ lactose; S. sonnei can slowly_ ferment lactose.ferment lactose. l l According to O antigen, 4 groupsAccording to O antigen, 4 groups l l Easily causing drug-resistence.Easily causing drug-resistence. ShigellosisShigellosis l l within 2-3 dayswithin 2-3 days epithelial cell damageepithelial cell damage Shiga toxinShiga toxin l l enterotoxicenterotoxic l l cytotoxiccytotoxic l l inhibits protein synthesisinhibits protein synthesis lysing 28S rRNA ShigellaShigella attachment and penetration attachment and penetration l l WWithin 2-3 daysithin 2-3 days l l E Epithelial cell pithelial cell damagedamage Clinical significanceClinical significance l l man only “reservoir“man only “reservoir“ l l mostly young children mostly young children fecal to oral contactfecal to oral contact children to adultschildren to adults l l transmitted by adult food handlerstransmitted by adult food handlers unwashed handsunwashed hands Clinical significanceClinical significance lThe infective dose required to cause infection is very low (10-200 organisms). lThere is an incubation of 1-7 days followed by fever, cramping, abdominal pain, and watery diarrhea (due to the toxin)for 1-3 days. lThis may be followed by frequent, scant stools with blood, mucous, and pus (due to invasion of intestinal mucosa). lIs is rare for the organism to disseminate. lThe 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. ImmunityImmunity lSIgA. Diagnosis of Shigella infectionDiagnosis of Shigella infection lSpecimen: stool. lCulture and Identification lQuick immunological methods: 1. Immunofluorescent “ball” test; 2. Coagglutination. PreventionPrevention lstreptomycin dependent (SD) dysentery vaccine. Treating shigellosisTreating shigellosis lmanage dehydration lpatients respond to antibiotics , Problem of drug-resistance disease duration diminished Shigella lShigella (4 species; S. flexneri, S. boydii, S. sonnei, S. dysenteriae) all cause bacillary dysentery or shigellosis, (bloody feces associated with intestinal pain). The organism invades the epithelial lining layer, but does not penetrate. Usually, within 2-3 days, dysentery results from bacteria damaging the epithelium lining layers of the intestine often with release of mucus and blood (found in the feces) and attraction of leukocytes (also found in the feces as “pus“). Shiga toxin (chromosomally encoded) is neurotoxic, enterotoxic and cytotoxic plays a role. The toxin inhibits protein synthesis (acting on the 80S ribosome and lysing 28S rRNA). This is primarily a disease of young children occurring by fecal-oral contact. Adults can catch this disease from children. However it can be transmitted by infected adult food handlers, contaminating food. The source in each case is unwashed hands. Man is the only “reservoir“. lPatients with severe dysentery are usually treated with antibiotics (e.g. ampicillin). In contrast to salmonellosis, patients respond to antibiotic therapy and disease duration is diminished. SalmonellaSalmonella lSalmonellosis may present as one of several syndromes including gastroenteritis, enteric (typhoid) fever or septicemia. The antigenic structures of salmonellae The antigenic structures of salmonellae used in serologic typingused in serologic typing SalmonellaSalmonella l l 2000 antigenic “types”2000 antigenic “types” l l disease categorydisease category S. enteritidisS. enteritidis many serotypesmany serotypes S. cholerae-suisS. cholerae-suis S. typhiS. typhi Virulence factorsVirulence factors lEndotoxin may play a role in intracellular survival lCapsule (for S. typhi and some strains of S. paratyphi) lAdhesions both fimbrial and non-fimbrial lType 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 lOuter membrane proteins - involved in the ability of Salmonella to survive inside macrophages lFlagella help bacteria to move through intestinal mucous lEnterotoxin - may be involved in gastroenteritis lIron capturing ability Enteric or typhoid feverEnteric or typhoid fever l l Enteric or typhoid fever occurs when the bacteria Enteric or typhoid fever occurs when the bacteria leave the intestine and multiply within cells of the leave the intestine and multiply within cells of the reticuloendothelial system. reticuloendothelial system. l l The bacteria then re-enter the intestine, causing The bacteria then re-enter the intestine, causing gastrointestinal symptoms. gastrointestinal symptoms. l l Typhoid fever has a 10-14 day incubation period Typhoid fever has a 10-14 day incubation period and may last for several weeks.and may last for several weeks. l l Salmonella typhi is the most common species Salmonella typhi is the most common species isolated from this salmonellosis. isolated from this salmonellosis. l l HHuman reservoiruman reservoir: :carrier state common l l C Contaminated foodontaminated food: :water supply water supply l l P Poor 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 days lasts 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 l l AntibioticsAntibiotics essential essential l l VaccinesVaccines Vi (capsular) antigen Vi (capsular) antigen : :protectiveprotective SalmonellaSalmonella gastroenteritisgastroenteritis l l Salmonella gastroenteritis is the most common Salmonella gastroenteritis is the most common form of salmonellosis and generally requires an form of salmonellosis and generally requires a