1. Enteric Gram-Negative Rods
(Enterobacteriaceae)

6. no yes white colonies pathogenic colored colonies (red) non-pathogenic
SS plate

7. lactose fermentation
Mechanism: Non-pathogenic enteric bacilli can ferment lactose to produce acidic by-products while pathogenic enteric bacilli such as Shigella and Salmonella can not.
Media: SS-plate or EMB plate , TSI agar slants
Basic components: lactose and a pH indicator
Triple Sugar Iron

8. Enterobacter Aerogenes
IMViC test
Indole test
Methyl red (MR) test
Voges-Proskauer (VP) test
Citrate utilization test  
E. coli
   
   
Enterobacter Aerogenes

9. Live in the intestinal tract of humans and animals
anaerobes
opportunistic infection (E. coli)
septicemia
pneumonia
meningitis
urinary tract infections
human pathogens (Salmonella and Shigella)
community-acquired diseases
respiratory infections (Klebsiella pneumoniae)
urinary tract infection (E. coli and Proteus)

10. E. coli causes urinary tract infections such as acute cystitis and pyelonephritis
上行感染 ascending infection
肾盂肾炎 pyelonephritis

11. enterotoxin: cause diarrhea and tissue damage endotoxin
pili
capsule
enterotoxin: cause diarrhea and tissue damage
endotoxin

12. somatic O Ag (lipopolysaccharide)
H Ag (flagella)
K/Vi Ag (capsule)
somatic O Ag (lipopolysaccharide)

13. Escherichia coli Gram stain? Motility? lactose fermentation? Antigens?
IMViC?
Transmission route?
virulence factors?

14. Enterotoxigenic E. coli (ETEC) Enteroinvasive E. coli (EIEC)
Enteropathogenic E. coli (EPEC)
Enterotoxigenic E. coli (ETEC)
Enteroinvasive E. coli (EIEC)
Enterohemorrhagic E. coli (EHEC)
Enteroaggregative E.coli (EAggEC) .

15. Enteropathogenic E. coli (EPEC)
Commonly associated with infant diarrhea.
Characteristic lesion with destruction of microvilli without invasion
Clinical signs
Fever
diarrhea with non-bloody stools
Vomiting
nausea

17. Enterotoxigenic E. coli (ETEC)
Cause "traveller’s diarrhea".
Two types of plasmid-encoded toxins are produced:
Heat labile toxins (LT), an adenyl cyclase which catalyze ATP to cAMP.
Heat stable toxins (ST), a guanyl cyclase to catalyze GTP to cGMP. cAMP/cGMP are the intracellular second messagers. The former increases the secretion of water and ions, and the latter inhibits ionic uptake.
Clinical signs
watery diarrhea
Fever
nausea

18. Enteroinvasive E. coli (EIEC)
Associated with elder children and adult diarrhea.
Without flagella
High virulence: a small number of EIEC can cause serious illness
Clinical signs
Acute inflammatory responses
tissue destruction
diarrhea with little fluid, a lot of blood and mucus containing polymorphonuclear cells

19. Enterohemorrhagic E. coli (EHEC)
EHEC produces bacteriophage-mediated exotoxin. This toxin is called as Vero toxin (VT) because of its cytotoxicity to cultured Vero cells.
In children, the disease may be progressed to a systemic stage called as hemolytic uremic syndrome (kidney injury) with 10% death rate.
Clinical signs
serious abdominal pain
diarrhea which is initially watery but then becomes bloody

20. Enteroaggregative E. coli (EAggEC)
It produces enteroaggregative heat-stable toxin (EAST) similar to the heat stable toxins of ETEC.
It produces mucous associated autoagglutinin which causes aggregation of the bacteria and formation of biofilm.
Clinical Signs
persistent, mucus-watery diarrhea
vomiting and dehydration in infants

21. Shigella
Gram stain?
motility?
Lactose fermentation?

22. Classification S. dysenteriae S. flexneri S. boydii S. sonnei
According to the difference of O antigen, Shigella strains are divided into 4 groups:
S. dysenteriae
S. flexneri
S. boydii
S. sonnei

23. Clinical findings Most common cause of bacterial dysentery in human
characteristic blood and mucus stools
Due to specific S-IgA, only invades intestinal mucosa and never enters bloodstream. But the endotoxin can be absorbed into bloodstream to cause endotoxemia.
Can cause toxic dysentery in children, display systemic toxic symptoms but no enteric symptoms. Has a a high death rate.

24. Virulent factors endotoxin
pilus
endotoxin
exotoxin: Shigella dysenteriae can produce an exotoxin called as shiga-toxin which is simmilar to Vero toxin (VT) of EHEC. Shiga-toxin is enterotoxic, cytotoxic and neurotoxic. So the dysentery (痢疾) caused by this microbe is more serious than that by the other three groups.

25. Control transmission
Dysentery is treated with antibiotics.
But multiple drug resistance mediated by plasmids are common in many Shigella strains.

26. Salmonella Gram stain? Motility? Lactose fermentation?
antigenic structures?

27. More than 2000 serotypes based on antigenic difference
Infect human (enteric fever)
S. typhi
S. paratyphi A
S. schottmuelleri (S. paratyphi B)
S. hirschfeldii
Infect animal and human
S. choleraesuis
S. typhimurium
S. enteritidis

28. Virulent factors
Vi antigen: consisted of capsular polysacchride. It resists phagocytosis and plays an important role during invasion of Salmonella.
endotoxin
enterotoxin

29. Diseases enteric fever (typhoid fever) S. typhi S. paratyphi A
S. schottmuelleri (S. paratyphi B)
S. hirschfeldii

30. Enteric fever (typhoid fever) is the most serious form of salmonella infection which only occurs in human.
Carrier state is common
In untreated patients, the death rate is 7% to 14%.
Antibiotic therapy is essential, vaccines are not effective and not widely used.

31. enteric fever development
The microbe initially invades intestinal mucosal epithelium and propagate at the local.
The microbe penetrates into the bloodstream to cause the first round of bacteremia with symptoms of fever, general discomfort and pain.
The microbe enters many organs such as liver, spleen, kidney, gall and marrow for further propagation.
The microbe penetrates into the bloodstream again to cause the second round of bacteremia with serious symptoms of high fever, swell of spleen and liver, rose-colored spots in skin, and tissue injury.

32. enteric fever Diagnosis
1. Definitive diagnosis-bacteria culture
first week
Stool and from the second week on
Marrow can be considered because of its high and permanent positive results.

33. enteric fever diagnosis
2. Widal test
a quantitative agglutination test using the known O antigen of S.typhi , and H antigens of S. typhi and S. paratyphi A/B to detect specific serum antibodies.
For one single serum sample, The titers of anti-O antigen IgM  1:80 and/or anti-H antigen IgG  1:160.
For two serum samples that collected with an interval of 5~7 days, 4-fold increase in titers of specific antibody.

34. Diseases Gastroenteritis (food-poisoning) S. choleraesuis
S. typhimurium
S. enteritidis

35. Gastroenteritis (food poisoning):
It is the most common Salmonella infection and usually transmitted from contaminated food. However, only a few of food poisoning-causing salmonella serotypes can produce enterotoxin.

36. Diseases Septicemia: commonly caused by S. hirschfeldii S. typhimurium
S. choleraesuis

37. Septicemia:
Many Salmonella serotypes can cause septicemia. This disease is commonly found in children or adult with low immunity.

38. Vibrio cholerae Cholera
                                                 

41. Introduction
Cholera caused by Vibrio cholerae is characterized by profuse watery diarrhea and serious vomiting which results in extreme loss of fluid and electrolytes, shock and kidney prostration. If patients are untreated, the death rate is as high as 60%.

42. Cholera: outbreak in India

43. Introduction There have been 8 great outbreaks in the world.
In 1991, a great outbreak (7th) started in Peru. There were more than a million patients in Central and South America.
In 1992, another great outbreak (8th) started in India and then spread to all parts of Asia. Not serotype O1 but O139 caused this outbreak.

44. Classification classical biotype
El Tor biotype
Responsible for the 1st-6th great outbreaks
Further typing O1
Responsible for the 7th great outbreak
Responsible for the 8th great outbreak in 1992
O-antigen
O139
non-O1/139
Cause cholera-like disease

46. high pH (pH )
TCBS (thiosulfate-citrate-bile-sucrose) agar plate

47. Major virulent factors
Flagellum: offers an ability to penetrate enteric mucus layer to reach the surface of host cells.
Pilus: adhesion
Cholera toxin: the most important virulent factor which induce electrolyte and water hypersecretion. This toxin is chromosomally encoded and its molecule contains subunits A and B.

48. Pathogenesis of cholera toxin
◇ Subunit B binds to its receptor (gangliosides) on the surface of epithelial cells and provides a channel allowing subunit A to enter host cell.
◇ Cellular proteinase lyses subunit A into peptides A1 and A2
Peptide A1 has activity of ADP-ribosylation to transfer ADP from NAD onto protein G which activates protein G ↓
Activated protein G induces cAMP overproduction
A large number of cAMP induces electrolyte and water hypersecretion of cells

49. the major cause of death…
Dehydration!! (脱水)
Replace fluid and electrolyte！！！
-most important treatment
Antibiotics such as tetracycline additionally used

50. Vibrio parahemolyticus
exists in raw sea-food and causes food poisoning in human
It is halophilic and optimal NaCl concentration in media is 3.5%
It produces hemolysin
Can be rapidly killed by acid (eg. acetic acid)