Overview Penicillin Campylobacter jejuni Enterococcus faecalis Neisseria gonorrohoeae Gram-negative bacilli resistant to benzylpenicillin G outer membrane layer inhibits entry of penicillin G may be susceptible to penicillin derivatives (e.g. ampicillin) Ampicillin Shigella Vancomycin Enterococcus faecalis (vancomycin resistant strains, VRE) VRSA Gram-negative bacilli outer membrane layer inhibits entry of vancomycin Methicillin MRSA via penicillin-binding protein mutation Bacitracin Streptococcus agalacticae Optochin Viridans group Streptococci Ceftriaxone some strains of Streptococcus pneumoniae Amantadine/rimantadine influenza virus Isoniazid + rifampin multi-drug resistant tuberculosis Aminoglycosides do not work against obligate anaerobes aminoglycosides require O2 to enter the cell Chloroquine chloroquine-resistant Plasmodium falciparum malaria