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Micro block 1 > 02 Normal Flora > Flashcards

02 Normal Flora Flashcards

1
Q

Normal flora

(In skin, nose, oropharynx, gingival crevices, colon, vagina)

A

Normal flora

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2
Q

Normal flora - Skin

A

Normal flora - Skin

1) Staphylococcus epidermidis*

2) Propionibacterium acnes
3) Candida albicans
notes:

  • Most located superficially (corneum stratum)
  • Some found in hair follicles
  • Anaerobic bacteria in deeper follicles in dermis
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3
Q

Staph epidermidis

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A

Staph epidermidis

  • Most common microbial skin flora
  • Important in following scenarios:
    1. Gains access to bloodstream:

–Indwelling catheters/IV shunts/urinary catheters

–S.epidermidis is an important cause of infections of catheters, IVs and shunts *

2.  **Infects prosthetic devices \***

–Heart valves, joints

–Secretes slime that helps it adhere to prosthetic devices and form a biofilm (layer) impenetrable to antibiotics *

3. Common **contaminant of blood cultures \***
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4
Q

Propionibacterium acnes

A

Propionibacterium

  • Skin anaerobe
  • Implicated in acne
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5
Q

Candida albicans

A

Candida albicans

  • Candida albicans (yeast-unicellular fungus)
    • May gain access to bloodstream in patients with IV catheters/ IV drug abuse
    • Important cause of systemic infections in patients with reduced cell-mediated immunity
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6
Q

Normal flora – Respiratory tract

A

Normal flora – Respiratory tract

  • Staphylococcus aureus (nose)
  • Viridans Streptococci (mouth and throat)
  • Eikenella corrodens (mouth)
  • Gingival crevices (low O2)– Anaerobes
  • Gingival crevices – Actinomyces israelii
  • Can causes abcesses of the jaw, lungs, and abdomen
  • Non-pathogenic Neisseria species (throat)
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7
Q

Staphylococcus Aureus

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A

Staphylococcus aureus

  • Can cause many serious infections especially in a hospital setting
  • It is the leading cause of Hospital-acquired (nosocomial) infections *
  • Transmitted via sneezing, contaminated hands *
  • Health-care personnel that harbour S. aureus in ant. nares have been the cause of out * breaks of infections in hospital nurseries, ICUs, etc.
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8
Q

Viridans Streptococci

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A

Viridans Streptococci

normal flora in mouth (and throat)

Plaque & dental caries - S.mutans *

  • Plaque on enamel surface is made up of gelatinous glucans secreted by S.mutans, entrapped bacteria produce acids that demineralize the enamel and initiate caries

Leading cause of subacute bacterial endocarditis *

  • Enter bloodstream during dental surgery and infect damaged heart valves *
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9
Q

Eikenella corrodens

A

Eikenella corrodens

Normal flora of the Mouth

–Skin and soft tissue infections associated with human bites and “clenched-fist” injuries

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10
Q

Anaerobes

A

Anaerobes- in gingival crevices

Normal flora of the mouth in gingival crevices.

Gingival crevices (low O2)– Anaerobes

Bacteroides, Fusobacterium, Peptostreptococcus

If aspirated (fluid removed), can cause lung abcesses

especially seen in debilitated patients with poor dental hygiene

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11
Q

Actinomyces israelii

A

•Gingival crevices – Actinomyces israelii

Can causes abcesses of the jaw, lungs, and abdomen

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12
Q

Normal flora of Resp tract- Throat

A

Normal flora – Resp tract - Throat

  • Viridans streptococci
  • Non-pathogenic Neisseria species
  • Sometimes found:
    • Streptococcus pneumoniae *
    • Nontypeable Haemophilus influenzae (no capsule) *

NOTE: Normal flora of oropharynx inhibit the colonization and growth of pathogenic invaders like Streptococcus pyogenes, Neisseria meningitidis, etc.

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13
Q

Small intestine

A

Small intestine

  • Small numbers of streptococci, lactobacilli and yeasts (C.albicans)
  • Large numbers of these found in terminal ileum
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14
Q

Normal flora - Colon

A

Normal flora - Colon

Role of normal gut flora in extra-intestinal infections

  • Escherichia coli * ( leading cause of UTI)
  • Bacteroides fragilis * (peritonitis following trama to intestinal wall)
  • Enterococcus faecalis (UTI)
  • Clostridium difficile * (Prolonged antibiotic therapy)
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15
Q

Escherichia coli *

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A

Escherichia coli *

–E.coli - **leading cause of urinary tract infection (UTI)* **

–endogenous E.coli contaminate the urethra

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16
Q

Bacteroides fragilis

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A

Bacteroides fragilis

  • Imp. cause of peritonitis associated with perforation of intestinal wall following trauma, appendicitis
17
Q

Enterococcus faecalis

A

Enterococcus faecalis

  • Causes UTI
18
Q

Clostridium difficile

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A

Clostridium difficile

  • Presents in small numbers in gut
  • Prolonged antibiotic therapy suppresses other gut flora allowing overgrowth of Cl.difficile which then causes severe colitis
19
Q

Lactobacillus

A

Lactobacillus

Normal flora of Genitourinary tract

Lactobacillus

  • Adult vaginal flora – predominantly Lactobacilli
    • Produce acid that keeps vaginal pH low
    • Before puberty & after menopause - Low numbers of lactobacilli and higher pH
  • prevent growth of potential pathogens

Present in small numbers

  • Mobiluncus
  • Gardnerella
  • Candida albicans

Supression of Lactobacilli * (by antibiotics) can result in:

  • Vaginal candidiasis *– overgrowth of Candida albicans
  • Bacterial vaginosis *– overgrowth of Mobiluncus + Gardnerella
20
Q

Normal flora – Genitourinary tract

A

Normal flora – Genitourinary tract

  • ​Vagina
    • Lactobacillus
      • In small numbers:
        • Mobiluncus
        • Gardnerella
        • Candida albicans
  • ​Vagina introitus (An introitus is an entrance that goes into a canal or hollow organ. The vaginal orifice is an introitus.)
    • E.coli *
    • Group B Streptococcus *
  • ​Urethra
    • Distal part of urethra is usually colonized by small numbers of bacteria (usually skin or gut flora)
    • **Endogenous flora from gut **
    • **​​E.coli **
    • **Staph epidermidis **
    • Enterococcus faecalis
    • Presence of urinary catheters allows bacteria direct access to the bladder

NOTE:Bladder has no microbial flora

21
Q

Important colonizers of vagina

A

Important colonizers of vagina

Important colonizers of vagina, introitus (An introitus is an entrance that goes into a canal or hollow organ.) *

  • E.coli *
  • Group B Streptococcus *

NOTE: Both can cause meningitis and sepsis in the newborn on transmission during the birth process

23
Q

Urethra

A

Urethra

  • Bladder has no microbial flora
  • Distal part of urethra is usually colonized by small numbers of bacteria (usually skin or gut flora)
  • Endogenous flora from gut that colonize the urethra can cause urethritis and cystitis (bladder infection) which may even extend to the renal pelvis (pyelonephritis) *
  • E.coli, Staph epidermidis, Enterococcus faecalis *
  • Presence of urinary catheters allows bacteria direct access to the bladder

Micro block 1 (11 decks)

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