Antibiotic Resistance

Mechanism of resistance	Organism involved	Antibiotics affected	Action taken
Antibiotic inactivation by plasmid mediated B- lactamase production.	Staph aureus	Penicillin	Use B-lactamase inhibitors: Clavulanic acid, Tazobactam, sulfobactam
Antibiotic inactivation by plasmid mediated ampicillin hydrolyzing enzymes (TEM-1 is the most common B-lactamase)	E.coli, H. influenza, N.gonorrhea.
Antibiotic inactivation by inducible chromosomally mediated B-lactamase production.	ESCAPPM (Enterobacter sp. Serratia sp., Citrobacter sp. Acinetobacter sp.Pseudomonas aeruginosa,Proteus vulgaris, Morganella morganii)	Third generation cephalosporins
Antibiotic inactivation by extended spectrum beta lactamase (ESBL)-TEM1, TEM2, SHV1.	Klebsiella pneumonia E.coli	Inactivates all cephalosporins	Use Meropenem or co-trimoxazole.
Alteration of target site by alteration in Penicillin Binding Proteins (PBPs)	Penicillin resistant strains of Strep pneumonia MRSA Coagulase negative staph.	Penicillin
Alteration of target site by alteration in gyrase target sites.		Fluroquinolones (Ciprofloxacin Norfloxacin)
Alteration of target site by ribosomal target site		Streptomycin Erythromycin Tetracycline
Alteration of target site by single step mutation that alters the binding affinity of Rifampicin to RNA polymerase	N. meningitides, Staph aureus, Mycobacteria spp, Pseudomonas aeruginosa Enterobacterioceae
Changes in cell permeability or alterations in or overproduction of dihydrofolate reductase		Trimethoprim Sulphonamide Vancomycin (Changes in enterococcal cell wall prevents vancomycin binding)
Decrease antibiotic permeability by changes in porins (resulting in diminished penetration)	Responsible for resistance of Enterobacterioceae and Pseudomonas aeruginosa to Trimethoprim and some fluoroquinolones	B-lactams Aminoglycoside Chloramphenicol
Active efflux of antibiotics from within bacteria-resulting in diminished intracellular drug conc.		Linezolid