Narrow-Spectrum
Natural Penicillin

Highly bactericidal, only
gram positives/anaerobes,
susceptible to betalactamases

Targets
GPC: Streptococci, Meningococcus
Listeria (GPB)
GNC: Neisseria, Clostridia
Treponemma (Spiral)

Synergistic effects with
aminoglycosides

narrow spectrum but is
useful for treating staphlococci which are resistant to benpen due to beta-lactamase activity
It should not be used if the organism is sensitive to benpen as benpen is more bactericidal

Moderate spectrum
Semisynthetic
Can penetrate some gram
negative outer membranes,
but susceptible to betalactamases. Often given with clauvanic acid
Targets
Strep, Listeria, Enterococcus, Haemophilus

Resistance
MRSA
Many Staph
-Betalactamase prod
Gram Negatives

MRSA develop or acquire the gene mecA which synthesizes an additional penicillin binding protein that enables it to continue cell wall synthesis in the presence of a beta lactam drug

Bacteria produce beta lactamases, which hydrolyse and inactivate the antibiotic

Resistance
MRSA
Many Staph
-Betalactamase prod