《微生物学》课程PPT课件讲稿（英文版）Lecture 12 Enterobacteriaceae

Enterobacteriaceae Diversity of species Ecology Found worldwide in soil, water, vegetation, and microbial flora of animals and humans Some are always associated with disease e.g., Shigella, Salmonella, yersinia pestis Some are normal flora that can become opportunistic pathogens . e.g. E, coll, k. pneumoniae p mirabilis BIOL 533 Lecture

BIOL 533 2 Lecture 12 Enterobacteriaceae • Diversity of species • Ecology – Found worldwide in soil, water, vegetation, and microbial flora of animals and humans – Some are always associated with disease • e.g., Shigella, Salmonella, Yersinia pestis – Some are normal flora that can become opportunistic pathogens • e.g., E. coli, K. pneumoniae, P. mirabilis

Enterobacteriaceae Epidemiology Animal reservoir: most salmonella infections Human carrier:5a/e∥m5hige∥a Endogenous spread in a susceptible patient Can involve all body sites 5% hospitalized patients develop nosocomial infections primarily caused by Enterobacteriaceae such as Escherichia ● Sites of infection BIOL 533 Lecture

BIOL 533 3 Lecture 12 Enterobacteriaceae • Epidemiology – Animal reservoir: most Salmonella infections – Human carrier: Salmonella typhi, Shigella – Endogenous spread in a susceptible patient • Can involve all body sites • 5% hospitalized patients develop nosocomial infections, primarily caused by Enterobacteriaceae such as Escherichia • Sites of infection

Microbial Physiology and structure Cell morphology Moderate-sized gram rods Non-spore-forming Motile(with peritrichous flagella) or non-motile Physiology All are facultative anaerobes Simple nutritional requirements Ferment glucose Reduce nitrates to nitrites BIOL 533 Lecture

BIOL 533 4 Lecture 12 Microbial Physiology and Structure • Cell morphology – Moderate-sized Gram— rods • Non-spore-forming • Motile (with peritrichous flagella) or non-motile – Physiology • All are facultative anaerobes • Simple nutritional requirements: – Ferment glucose – Reduce nitrates to nitrites

Distinguishing Characteristics Oxidase Distinguishes among other fermentative and non- fermentative gram bacilli Lactose fermentation(red colonies on MacConkey agar) Separate Escherichia, Klebsiella, Enterobacter from other lactose Enterobacteriaceae BIOL 533 Lecture

BIOL 533 5 Lecture 12 Distinguishing Characteristics • Oxidase¯: – Distinguishes among other fermentative and non-fermentative Gram— bacilli • Lactose fermentation (red colonies on MacConkey agar) – Separate Escherichia, Klebsiella, Enterobacter from other lactose— Enterobacteriaceae

Distinguishing Characteristics Resistance to bile salts Separate Shige∥ a and sa/me∥ la from normal flora in this group Eosin Methylene Blue(EMB Lactose, eosin, methylene blue; Lact, grow With green sheen BIOL 533 Lecture 12

BIOL 533 6 Lecture 12 Distinguishing Characteristics • Resistance to bile salts – Separate Shigella and Salmonella from normal flora in this group • Eosin Methylene Blue (EMB) – Lactose, eosinY, methylene blue; Lac+; grow with green sheen

Virulence factors Antigens Somatic O"LPS Major cell wall Ag; heat stable Specifico"antigens associated with each genus; however, cross reactions are common Salmonella and citrobacter Escherichia and Shigella BIOL 533 7 Lecture 12

BIOL 533 7 Lecture 12 Virulence Factors • Antigens – Somatic “O” LPS • Major cell wall Ag; heat stable • Specific “O” antigens associated with each genus; however, cross reactions are common – Salmonella and Citrobacter – Escherichia and Shigella

Virulence factors Capsular K Either protein or polysaccharide e Heat-labile May interfere with detection of"O o Removed by boling organisms Capsular antigen of salmonela typhi referred to as Vi antigen BIOL 533 Lecture 12

BIOL 533 8 Lecture 12 Virulence Factors • Capsular K – Either protein or polysaccharide • Heat-labile • May interfere with detection of “O” • Removed by boiling organisms – Capsular antigen of Salmonella typhi referred to as Vi antigen

Virulence factors Capsular K, continued Shared by different genera both inside and outside of family ● Cross reactions E. coliKl with N, meningitidis and Haemophilus meningitidis K pneumoniae with S pneunomiae Organisms with specific antigens have been associated with increased virulence (e.g. E. collKl with neonatal meningitis) BIOL 533 Lecture

BIOL 533 9 Lecture 12 Virulence Factors • Capsular K, continued – Shared by different genera both inside and outside of family • Cross reactions – E. coli K1 with N. meningitidis and Haemophilus meningitidis – K. pneumoniae with S. pneunomiae – Organisms with specific antigens have been associated with increased virulence (e.g., E. coli K1 with neonatal meningitis)

Virulence factors Flagella h Heat-labile proteins Can be absent or undergo antigenic variation (present in two phases) Specific h antigens assocated with disease BIOL 533 Lecture 12

BIOL 533 10 Lecture 12 Virulence Factors • Flagella H – Heat-labile proteins • Can be absent or undergo antigenic variation (present in two phases) • Specific H antigens assocated with disease

Virulence factors General role in pathogenesis ofˇO"“K and H"antigens Specific antigens associated with meningitis, gastroenteritis, and urinary tract infections Role that Ag's play in these diseases is not clear Some capsular Ag are poor immunogens Protect against antibody-mediated phagocytosis Flagellar Ag probably play a role in adherence BIOL 533 Lecture

BIOL 533 11 Lecture 12 Virulence Factors • General role in pathogenesis of “O,” “K,” and “H” antigens – Specific antigens associated with meningitis, gastroenteritis, and urinary tract infections • Role that Ag’s play in these diseases is not clear – Some capsular Ag are poor immunogens • Protect against antibody-mediated phagocytosis – Flagellar Ag probably play a role in adherence