Micro test2 11-13th

Concentration of antibiotic which prevents bacteria from growing enough to make the fluid turbid (usually good enough for patient unless they have a weak immune system)

• The concentration of antibiotic that kills all the bacteria.
• (this is the concentration of antibiotic that must be reached if the patient is immunocompromised or has a life threatening condition)

• It is the best way to compare antibiotic potency
• An analysis of hundreds of isolates of a species of bacteria.
• It is the MIC value that inhibits 90% of the bacteria tested
• Low is better

• Mutant Prevention Concentration = antibiotic concentration that when added to 10^10 CFU allows no bacteria to survive
• Reaching this concentration in patients slows the spread of antibiotic resistance

• Chains of NAG and NAMA
• Attached to NAMA is AA, AA, AA, D-Ala, D-Ala
• These peptides crosslink with other peptidoglycan strands

• Antibiotic that inhibits the formation of UDP-NAMA by binding to PEPA transferase, inhibiting muramic acid
• Broad spectrum both gram + and –
• Bacteria rapidly become resistant to

• Blocks the addition of both D-ala D-ala’s
• Good for drug resistant TB when used in conjunction with other drugs

• Blocks lipid dephosphorylation so that lipid cannot be added to the forming peptidoglycan
• If lipid is not added it cannot flip across membrane
• Only works on gram + by itself

• Bacitracin – disrupts cell walls of gram +
• Polymyxin – disrupts cell walls of gram –
• Neomycin – broad spectrum aminoglycoside

The terminal D-ala on a peptidoglycan peptide

• Method 1:
• VanX destroys d-ala-d-ala (plasmid coded)
• VanH converts pyruvate to d-lactate (plasmid coded)
• VanA links d-ala to d-lac
• Method 2:
• Staphylococcus have thick cell wall that binds vancomycin on outer surface
• This strain of staph is called “VIRSA”

Staph

• Previous endocarditis
• Prosthetic heart valve

• Carbenicillin and Ticarcillin
• They have an extra carboxy group which allows penetration
• They resist intrinsic Bla

• Staphylococcus and Streptococcus (NOT enterococcus)
• Susceptible gram – like Klebsiella
• Prophylaxis of clean surgery
• Prophylaxis of dental patient with implant

• Haemophilus respiratory infections
• Gram negative beta-lactamase producers like bacteroides
• Prophylaxis for surgery involving mucous membranes

Blocks PBP2a of MRSA

• The gene for beta lactamase activity is found on a small plasmid with a high copy number
• The high copy number allows for the production of more mRNA and thus more enzyme
• The high copy number also allows for more chance of mutations per cell which leads to the broad spectrum

Aerobic Gram-negative bacteria