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Zero-to-Finals: Bacteria, Remember that encapsulated bacteria like S.…
Zero-to-Finals: Bacteria
Basics:
- Bacteria are single-celled organisms
- Classified according to:
1) Shape
2) Gram-staining
3) O2 requirements
SHAPE
- Cocci
-Staphylococcus = Clusters (like grapes)
-Streptococcus = Chains or pairs
- Bacilli (Rod-shaped)
-Eg. E.coli, Salmonella
- Spirochetes (Spiral-shaped)
-Eg. Treponema pallidum (syphilis), Borrelia burgdorferi (Lyme)
GRAM STAIN
- Gram + ive
-Thick peptidoglycan wall
- Cocci = Staph, Strep
- Bacilli = Clostridium, Bacillus
- Gram - ive
-Thin peptidoglycan wall w outer mem stains pink
- Cocci = Neisseria gonorrhoeae, Neisseria meningitidis
- Bacilli = E.coli, Klebsiella, Pseudomonas
O2 Requirement
- Aerobic: Require O2
-Mycobacterium TB
- Anaerobic: Thrive w out O2
-C.diff
- Facultative Anaerobes: w or w out O2
-E.coli
Common Bacteria
Gram +
Cocci
- Staph aureus
-cause: Skin infections, Endocarditis, osteomyelitis
-MRSA - Methicillin-resistant strain
- Strep pyogenes (Group A strep)
-causes: Tonsilitis, Cellulitis, NecFas
-Complications = Rheumatic fever, Glomerulonephritis
Bacilli
- C.Diff
-causes: Abx-ass diarrhea, pseudomembranous colitis
- Listeria monocytogenes
-causes: Meningitis in neonates, imm compromised pts
Gram -
Cocci
- Neisseria meningitidis
-Meningitis, meningoccemia
-Symp = Non-blanching rash
- Neisseria gonorrhoeae
-causes: Gonorrhea
Bacilli
- Escherichia Coli (E.coli)
-causes: UTI's, Gastro, Sepsis
- Klebsiella pneumoniae
-Pneumonia, UTI's
- Pseudomonas aeruginosa
-causes: Wound infections, HAP
Spirochetes
- Treponema pallidum (Syphilis)
- Borrelia burgdorferi (Lyme)
Syndromes & related Bac
Sepsis
E.coli, S.aureua, Strep Pneumoniae
Meningitis
- Neonates: Listeria monocytogenes, Group B strep, E.coli
- Adults: Neisseria meningitidis, Strep pneumoniae
Pneumonia
- CAP: Strep pneumoniae, H.Influenza
- HAP: Klebsiella pneumoniae, Pseudomonas aeruginosa
Gastroenteritis
Salmonella, Shigella, E.coli, Campylobacter
Endocarditis
- Native valves: Strep viridans, Staph. aureus
- Prosthetic valves: Staph Epidermidis, Enterococcus
UTI's
E.coli, Proteus mirabilis, Enterococcus
ABX Resistance
- Key resistant Bacteria:
1) MRSA
2) VRE: Vancomycin-resistant Enterococcus
3) ESBL-Producing Bac: E.coli, Klebsiella pneum
- Strategies to combat Abx resistance:
1) Antimicrobial Stewardship
2) Target abx therapy based on micro results
Remember that encapsulated bacteria like S. pneumoniae and Neisseria meningitidis are harder to clear in patients with splenectomy or complement deficiency.
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HIGH-risk path: "ESKAPE"
- Enterococcus faecium
- Staph aureus
- Klebsiella pneum
- Acinetobacter baumannii
- Pseudomonas aeruginosa
- Enterobacter species
Streptococcus agalacticae: most common cause of severe infection in neonates. It is a Gram-positive coccus (round-shaped bacterium) which forms chains and is a facultative anaerobe.
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