3. خصوصیات کلی
40 جنس و 150 گونه ..کمتر از 20 جنس مسئول بیش از 90 در صد عفونتهاست.
35 درصد سپتی سمی ها
بیش از 70 درصد عفونتهای ادرای
بسیاری از عفونتهای روده ای
پاتوژنهای این گروه (سالمونلا تایفی،شیگلا،یرسینیا پستیس)
فرصت طلب ها (اشرشیا ،کلبسیلا و پروتئوس)
انتقال فاکتورهای ویرولانس از طریق پلاسمید یا باکتریوفاژ

4. مخازن عفونتها :مخازن حیوانی (سالمونلا و یرسینیا)
حاملان انسانی (شیگلا و سالمونلا تایفی)
گسترش درونی (اشرشیاکلی)
نکته:همه متحرک اند به جز شیگلا .کلبسیلا و یرسینیا
کپسول :کلبسیلا انتروباکتر

9. Incidence of Enterobacteriaceae Associated with Bacteremia

10. Differentiation between LF & NLF by Growth on MacConkey agar
Bile salts
Crystal violet
Lactose
Neutral red
Inhibit growth of G+ve bacteria
pH indicator
Acidic: Pink
Cause of differential
Cause of selectivity
Lactose non feremnters
colorless colonies
Lactose feremnters
Pink colonies

11. Enterobacteriaceae
Lactose Non-Fermenters
Lactose Fermenters
No acid
Acid
Neutral red
Colorless colonies
Pink colonies
Escherichia coli
Klebsiella spp
Enterobacter spp
Citrobacter spp
Salmonella spp
Schigella spp
Proteus spp
Yersinina spp

16. 50 Flagella ‘H’ antigen
Fimbriae/Pili
‘F (K)’ antigen
Capsule ‘K’ antigen 100
150 LPS ‘O’ antigen

17. Serologic identification based on presence or absence of several antigenic structures

18. Antigenic Structure of Enterobacteriaceae
S. typhi
O antigen side chain
(Fimbriae)

22. Exotoxins also known as enterotoxins:
Produced and secreted by the organism
Also play a major role in the pathogenicity of many of these organisms
Causes severe gastrointestinal symptoms such as nausea, vomiting, diarrhea, fluid loss, and cramping

27. Pedestal formation

30. E. coli toxins
ST: is heat stable and binds to specific receptors to stimulate the
production of cGMP with the same results as with LT

32. Shiga-type toxin: Also called the verotoxin
Is cytotoxic, enterotoxic, neurotoxic
May cause diarrhea and ulceration of the G.I. tract
Two types shiga-like toxin 1 and shiga-like toxin 2.
Inhibit protein synthesis by cleaving a 28S rRNA that’s part of the 60S subunit

33. Type III secretion system

35. اشرشیا اینترواگرسیو
اسهال حاد یا مزمن (14روزه) در ایدزی ها مکانیسم بیماریزایی کاملا مشخص نیست
سپسیس:به دنبال عفونت ادراری یا اسیب به روده در نوزادان شدیدتر (فقدان انتی بادی IgM)
مننژیت:باکتری بصورت فلور در مجاری معده ای روده ای زنان باردار و نوزادان تازه متولد شده..75 درصد انتی ژن K1

38. Klebsiella. sp Opportunistic bacteria Includes:
Klebsiella pneumoniae (K. friedlanderi)
responsible for most infections
found in the RT of 10% of the population
Klebsiella oxytoca
Klebsiella ozaenae
Klebsiella rhinoscleromatis
Gram (-)
Lactose fermenter in MacConkey
Mucoid capsule

39. Determinants of Pathogenicity
Capsule (mucoid), antiphagocytic and major virulence factor type 1,2 respiratory infection and type 8,9,10 urinary infection
Some strains produce toxins similar to heat-labile (LT) and heat-stable (ST) toxins of E. coli
Antibiotic resistance to most antibiotics

41. Enterobacter sp. Species: Enterobacter aerogenes
Enterobacter agglomerans
Enterobacter cloacae
Often found in the normal intestinal flora, soil and water
Differentiated from other enterobacteriaceae based on biochemical characteristics
Causes nosocomial infections esp. of urinary tract, bacteremia and septicemia
Produces beta-lactamase  inactivates penicillins and 1st- gen. cephalosporins

43. Serratia sp. water & soil red pigment - prodigiosin
Serratia marcescens – nosocomial surgical wound infections, UTI, RTI, septicemia
Treatment: aminoglycosides, chloramphenicol, trimethoprim-sulfa- methoxazole

44. Proteus sp. Species: Proteus mirabilis Proteus vulgaris Gram (-) rod
Extremely motile – numerous and long peritrichous flagella (“swarming phenomenon”)
Produce urease
Produce H2S from sodium thiosulfate
Ferment indole (P. vulgaris)
Produce phenylalanine deaminase

46. Morganella morganii Providencia sp.
Closely related to Proteus
indole fermenters
Urease producers but most Providencia species are not
Produce phenylalanine deaminase
Nosocomial UTI, pneumonia, bacteremia

47. Citrobacter sp. Closely related to Salmonella Found in the environment
Citrobacter freundii
Citrobacter diversus
Closely related to Salmonella
Found in the environment
Stool’s normal flora
Opportunistic bacteria
Causes: UTI, diarrhea (in children), wound infections, septicemia and neonatal meningitis
brain abscesses (C. diversus)
C. freundii - can be enterotoxigenic

49. Salmonella “species” No. of serotypes Species Subspecies
Isolated from:
S.enterica
S.bongori I II
IIIa
IIIb IV VI
>1300
464 64
309 10 93 17
warm-blooded
animals
Cold-blooded
animals V

50. Major species Salmonella typhi (the only systemically invasive specie)
- Typhoid fever, only in humans
2. Salmonella enteritidis, S. enteritidis typhimurium
- enterocolitis (salmonellosis)
- diarrhea, fever, abdominal pain
- dehydration and electrolyte imbalance
3. Salmonella choleraesuis

51. Salmonella attachment: fimbriae
Each serotype can produce many different types of fimbriae/pili
Eg S.typhimurium has genes for 13 different types of pili

53. 12 PIs identified in Salmonella, strain may not have all PIs.
Salmonella chromosome
Type III
secretion
system
Invasion of
epithelial cells
Enteritis
SPI 1
SPI 2
Type III
secretion
system
Survival in
macrophages
12 PIs identified in Salmonella, strain may not have all PIs.

54. Salmonellae may cause disease or colonise the gut of a host and cause no disease
Salmonella are invasive, facultative intracellular pathogens
Important syndromes are:
1. ENTERITIS resulting in diarrhoea, organisms restricted to gut tissue, don’t invade beyond mesenteric lymph node
2. SEPTICAEMIA organisms spread throughout body and grow in different organs, eg, liver and spleen, made lead to abortion or joint infections or pneumonia. May or may not be diarrhoea

55. Enteritis Septicaemia Macrophage Liver MLN Neutrophil Spleen M cell
Enterocyte
Tight junction
M cell
Macrophage
Neutrophil
Enteritis
MLN
Liver
Spleen
Septicaemia

58. Lysosome Phagosome H+ H+ Phagolysosome fusion Acidification
Prevent fusion H+
Survival in
phagososome
Phagosome H+

60. Salmonella typhi Symptoms Pathogenesis Typhoid Fever
contaminated food or water
infections at other sites
low infectious dose
involve lymphatic and circulatory systems
Symptoms
severe fever/headache
apathy, weakness, abdominal pain and rash.
1-3% recovered patients become carriers, harboring Salmonella in their gallbladder

62. Based on somatic O antigen
Antigenic structure
Complex, there are more than 40 sero types based on their LPS of somatic O antigen
Based on somatic O antigen
S. dysenteriae (A)
S. flexneri (B)
S. boydii (C)
S. sonnei (D)

65. Shigellosis
Shigella spp. producing Shiga toxin
Shiga toxin causes inflammation and bleeding

67. Incubation period 1-2 days. Sudden onset of
Clinical features
Incubation period 1-2 days.
Sudden onset of
Abdominal pain, fever and Watery diarrhoea,
Mucus and bloody stools.
Fever and diarrhea subsides 2-5 days.
Loss of water (dehydration).
Chronic carrier status may result.

69. Sources of in infection
Contaminated water
Contaminated dairy products
Shellfish
Dried or frozen eggs
Meat and meat products of infected animals
Household pets

70. Dysentery carriers There are healthy carriers in the community
This will happen after an attack
Will excrete in the bacilli intermittently for few weeks - small proportion can become persistent carriers

71. Microorganism Mechanisms Diseases Transmission Treatment Prevention
CLINICAL SUMMARY TABLE
Virulence
Microorganism Mechanisms Diseases Transmission Treatment Prevention
Salmonella typhi Not killed by Typhoid Fecal oral, Broad Water and
macrophages, Fever carriers spectrum sewage tx,
Endotoxins antibiotics Vaccines,
Control
carriers
Salmonella sp Endotoxins Gastroenteritis Food & Supportive Proper
waterborne Rx cooking,
Sanitary
procedures
Shigella sp Shiga toxin Dysentery Fecal-oral Rehydration Good
Endotoxins Antibiotics hygiene
Escherichia coli Enterotoxins Traveler’s Fecal-oral Rehydration Proper
Shiga-like toxin diarrhea, Opportunists Antibiotics? food
Attachment pili/ Hemorrhagic don’t help- handling,
fimbriae colitis, harmful Good
Urinary tract infections/Nosocomial infections sanitation

75. Diagnostic tests
Specimens-Urine, blood, pus, CSF, Sputum, Stools
Smear
Culture blood agar
Immunity is not satisfactory.
Management
No single specific therapy available
Sulfonamides
Ampicillin
Cephalosporines
Fluoroquinolone
Aminoglycoside

79. Non-lactose fermenters Pathogens of warm blooded animals
SALMONELLA
Indole -ve
Non-lactose fermenters
Pathogens of warm blooded animals
“commensals” of cold blooded animals

80. Selective media/indicators
Pale (yellowish) colonies on MacConkey agar
Alkaline reaction (red colonies) on brilliant green agar
On XLD (xylose-lysine deoxicholate), red colonies with black centre (H2S)
API 20E kit if available (very useful).
Typically, on TSI, most Salmonella spp. give red (alkaline) slant, yellow (acidic) butt, and black (H2S) production. (R/Y/H2S+)

81. Salmonella isolation and identification
API 20E: commercial kit of many biochemical tests in single raw

84. HEKTOEN ENTERIC(HE) AGAR
Hektoen enteric agar is a medium designed for the isolation and recovery of fecal specimens belonging to the Enterobacteriaceae family, especially Salmonella and Shigella. It can differentiate between bacteria that ferment lactose and those that don't. Acid produced from fermenting lactose imparts a yellow-orange color to the medium due to the presence of a pH indicator. Non-lactose fermenters do not significantly change the color of the medium. HE agar can also detect the production of hydrogen sulfide gas, which turns parts of the medium black.

86. INTERPRETATION OF TUBES ABOVE
TUBE 1 (UNINOCULATED)
TUBE 2
TUBE 3
TUBE 4
TUBE 5
SLANT - A K
BUTT
HYDROGEN SULFIDE +
GAS
A=Acidic K=Alkaline

88. The End