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Micro > Bacteria Of Lower GI > Flashcards

Bacteria Of Lower GI Flashcards

1
Q

Enterobacteriaceae (gram , 5 major features)

A

Gram negative bacilli

  1. All ferment glucose –
  2. All reduce nitrates to nitrites(energy r) –
  3. All are oxidase negative –
  4. All Facultative anaerobes.
  5. All are motile except Klebsiella,.Shigella and some Yersinia
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2
Q

Virulence and Antigenic Factors of Enterics(3)

A

Ability to colonize, adhere, produce various toxins and enzymes to invade tissues
• Some possess plasmids that may mediate resistance to antibiotics
• Many enterics possess antigens that can be used to identify groups

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3
Q

Antigenic Factors of Enterics

A

O antigen – somatic, heat-stable antigen in the
cell wall
H antigend – flagellar antigen
K antigen – capsular antigen

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4
Q

Antigenic Factors of Enterics

A

O antigen – somatic, heat-stable antigen in the
cell wall
H antigend – flagellar antigen
K antigen – capsular antigen

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5
Q

enterics are divided into two categories:

A

Opportunistic pathogens : normally part of the usual intestinal flora that may produce infection outside the intestine

Primary intestinal pathogens : Salmonella, Shigella, and Yersinia sp.

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6
Q

Escherichia coli ( Common isolate from colon flora) cause(3)

A
  • meningitis (neonatal)
  • urinary tract infections, wound infection, bacteremia
  • Gastrointestinal Infections(DIARRHOEA)
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7
Q

Pathogenesis of E-coli (5)

A
  • Pili
  • Capsule
  • Endotoxin (fever, hypotension,DIC)
  • Two exotoxins (enterotoxins)
  • Motility
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8
Q

Laboratory diagnosis of E-coli (6)

A

1.Culture on MacConkey’s agar. They produce pink colonies due to lactose fermentation.

2.Biochemical tests: eg, Indole positive and methyl red tests

  1. Ferments glucose, lactose, xylose
  2. Does NOT produce H2S or phenylalanine deaminase
  3. Citrate negative
  4. Usually motile
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9
Q

Klebsiella species (3)

A

• K. pneumoniae makes the colonies moist and mucoid – Has a distinctive “yeasty” odor – Frequent cause of nosocomial lober pneumonia.
K. ozaenae: atrophic rhinitis.

K.rhinoscleromatis :destructive granuloma of the nose and the pharynx

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10
Q

Significant biochemical reactions ofKlebsiella (4)

A
  • Lactose positive
  • Citrate positive
  • Most are urease positive
  • Non-motile
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11
Q

Proteus, Morganella & Providencia species

A
  • All are normal intestinal flora
  • Opportunistic pathogens
  • Deaminate phenylalanine positive
  • All are lactose negative
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12
Q

Proteus (mirabilis , vulgaris)

A

UTI (promoting stone formation by precipitating Mg and Ca (stag horn ) )

Wounds

Ear

Bacteremia

Pneumonia

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13
Q

Why the urine of UT infection with proteus is alkaline ?

A

Proteus produce urease

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14
Q

Lab test for proteus

A

Swarming colonies (motile)

Urease +

Phenylalanine deaminase +

When cultured aerobically at 37 smells fishy

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15
Q

Salmonella disease

A

Enteritis

Bacteremia

Enteric fever

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16
Q

Salmonella diagnosis

A

Stool is cultured in selenite F

Widal test

17
Q

Salmonellae are facultative intracellular pathogen

A

No answer here

18
Q

Treatment of Enteric fever and bacteremia(2)

A
  1. require antibiotic treatment: chloramphenicol, ampicillin, trimethoprim-sulfamethoxazole.
  2. Surgical drainage of metastatic abscesses may be required.
19
Q

Treatment of Salmonella enterocolitis

A

needs only supportive therapy

20
Q

Treatment of Chronic carriers of S. typhi

A

may be cured by antibiotics alone or combined with cholecystectomy.

21
Q

Prevention and control of salmonella (4)

A
  1. Sanitary measures.
  2. Carriers must not be allowed to work as food handlers.
  3. Strict hygienic precautions for food handling
  4. Vaccines against S.typhi
22
Q

Vaccines against S.typhi:

A

Purified Vi antigen, parentral

Oral, live attenuated vaccine.

23
Q

Shigella species All species cause bacillary dysentery

A

No answer here

24
Q

Characteristics Of Shigella (5)

A 
Non lactose ferment 
– Non-motile –
 Do not produce gas from glucose –
 Do not hydrolyze urea 
– Do not produce H2S on TSI
25
Q

reservoir of Shigella

A

–Humans are only known reservoir

26
Q

Shigella transmission

A

Oral-fecal

27
Q

Shigella pathogenesis

A

–Secret Shiga toxin which cause dysentery (bloody stools, mucous, and numerous WBC)

28
Q

Laboratory diagnosis of Shigella

A

Large numbers of fecal leukocytes and some RBC may often be seen microscopically.
Culture: differential and selective media as used for salmonellae.

29
Q

Shigella Treatment (2)

A

Antibiotic treatment: chloramphenicol, ampicillin, tetracycline, and trimethoprim-sulfamethoxazole. Drug resistance is common.
Rehydration

30
Q

Prevention and control of dysentery:

A
  1. Sanitary control of water, food and milk; sewage disposal; and fly control.
  2. Isolation of patients and disinfection of excreta.
  3. Detection of subclinical cases and carriers.
31
Q

Yersinia Virulence factors (2)

A

resist phagocytic

Produce an endotoxin, exotoxin

32
Q

Y. pestis infections are treated with

A

combination of streptomycin and tetracycline is the treatment of choice.
chloramphenicol , or trimethoprim , sulfamethoxazole can be administered as alternative therapy.

33
Q

Control of Y. pestis infections (5)

A
  • Controlling the spread of rats.
  • Avoid flea bite and contact with dead rodents.
  • Isolation (quarantine) the patient for 72 hours after starting drugs.
  • Tetracycline for close contacts.
  • A killed vaccine : is not very effective.
34
Q

Campylobacter characteristics (6)

A
  • Slender, Rod Shaped or spiral
  • Motile
  • Gram negative
  • Microaerophilic
  • Thermophilic
  • Urease -ve
35
Q

• C. jejuni can cause (3)

A

Enterocolitis (contamination of food and water by contaminated domestic animal faeces)
Guillain-Barre Syndrome – Immune system attacks own nerves
Reiter’s Syndrome (arthritis, urethritis, conjunctivitis) 1-3 wks after infection

36
Q

Campylobacter lab diagnosis

A

Microscopic: G-ve bacilli,S –shaped or curved

Cultured sample of stool on skirrows agar –Microaerophilic(5% O, 10 % CO2 at 42 Oc)

37
Q

Campylobacter treatment (2)

A

mainly fluid and electrolyte replacement

Antibiotics : erythromycin , ciprofloxacin

Micro (6 decks)

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