Microbiology Flashcards
Gram positive bacteria have a ? proteoglycan cell wall and stain ? with Gram stain
thick proteoglycan cell wall
purple
Gram negative bacteria have a ? proteoglycan cell wall and stain ? with Gram stain
thin proteoglycan cell wall
pink
Classification of antimicrobial agents? (6)
- inhibit cell wall synthesis
- inhibit protein synthesis
- inhibit DNA synthesis
- inhibit RNA synthesis
- cell membrane toxin
- inhibit folate metabolism
Types of antimicrobials that inhibit cell wall synthesis? (2)
- B lactams
2. Gycopeptides
How do B lactams work?
- inhibit the enzymes responsible for building the proteoglycan cell wall of the bacteria i.e. penicillin binding protein
- bacteriocidal - prevents peptide cross linking thus daughter cells are weaker and lyse when they divide
Which bacteria are B lactam effective against?
Which bacteria are B lactam ineffective against?
a) gram +, gram -, enterococci
b) mycoplasma, chlamydia
Resistance against B lactams?
production of B lactamase
Penicillin
- which organisms?
- resistance?
Gram +
Broken down by B lactamase produced by Staph aureus
Amoxicillin
- broad or narrow?
- which organisms?
- resistance?
Broad spectrum Penicillin
Gram + Gram - Enterococci
Broken down by B lactamase produced by Staph aureus
Flucloxacillin
- broad or narrow?
- which organisms?
- resistance?
- narrow spectrum penicillin
- Gram +
- stable to B lactamase produced by Staph aureus
Piperacillin
- which organisms?
- resistance?
- example with Tazobactam?
Gram + Gram - Pseudomonas
Broken down by B lactamase produced by Staph aureus
Tazocin
What are Clavulanic Acid and Tazobactam?
B-lactamase inhibitors
Protect penicillins from B lactamase produced by Staph aureus
Allows broader spectrum
Examples of B lactams? (3)
- Penicillins
- Cephalosporins
- Carbepenems
Cephalexin
- type of B lactam
First generation cephalosporin
Cefuroxime
- type of B lactam
- resistance
Second generation cephalosporin
Stable to many B lacatamases produced by Gram -
Ceftriaxone
- type of B lactam
- broad or narrow?
- which organisms?
- association
- # 1 use
Third generation cephalosporin Broad Gram + Staph & Strep C difficile Meningitis first line
Cephtazidime
- type of B lactam
- which organisms?
Third generation cephalosporin
Pseudomonas
Extended Spectrum B Lactamases?
Organisms producing these are resistant to ALL cephalosporins
Carbepenems
- resistance
- broad or narrow?
- examples (3)
Resistant to Extended Spectrum B Lactamases Broad spectrum 1. Meropenem 2. Imipenem 3. Ertapenem
Key features of B Lactams (5)
- Non-toxic
- Renally excreted (low dose is renal impairment)
- Short half life (multiple daily doses)
- Do NOT cross BBB
- Cross-allergenic (if allergic to Penicillin 10% cross reactivity with Cephallosporins and Carbepenems)
Glycopeptides
- how do they work?
- which organism
- side effect
Inhibit cell wall synthesis
Gram - only
Nephrotoxic therefore drug level must be monitored
Vancomycin
- Class of Abx?
- use?
Glycopeptide
C difficile
Aminoglycosides
- mode of action?
- binding site
- toxicity? (2)
- which organism?
- inhibit protein synthesis
- 30s ribosomal subunit
1. ototoxic
2. nephrotoxic
Gram -ve
Gentamycin
- Class of abx?
- organisms?
- use
Aminoglycoside
Gram - especially Pseudomonas
Gram - sepsis