02 Normal Flora Flashcards
Normal flora
(In skin, nose, oropharynx, gingival crevices, colon, vagina)
Normal flora
Normal flora - Skin
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
Staph epidermidis
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Staph epidermidis
- Most common microbial skin flora
- Important in following scenarios:
- 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 \***
Propionibacterium acnes
Propionibacterium
- Skin anaerobe
- Implicated in acne
Candida albicans
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
Normal flora – Respiratory tract
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)
Staphylococcus Aureus
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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.
Viridans Streptococci
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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 *
Eikenella corrodens
Eikenella corrodens
Normal flora of the Mouth
–Skin and soft tissue infections associated with human bites and “clenched-fist” injuries
Anaerobes
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
Actinomyces israelii
•Gingival crevices – Actinomyces israelii
Can causes abcesses of the jaw, lungs, and abdomen
Normal flora of Resp tract- Throat
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.
Small intestine
Small intestine
- Small numbers of streptococci, lactobacilli and yeasts (C.albicans)
- Large numbers of these found in terminal ileum
Normal flora - Colon
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)
Escherichia coli *
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Escherichia coli *
–E.coli - **leading cause of urinary tract infection (UTI)* **
–endogenous E.coli contaminate the urethra