Chloramphenicol is a relatively simple neutral nitrobenzene derivative with a bitter taste. It is highly lipid soluble and is used either as the free base or in ester ... Working concentration Antibiotic Stock solution (mg/ml) Solvent**** Storage temp (oC) µg/ml dilution Function Ampicillin* 50 H 2 O -20o C 50 1.0 µl/ml Start studying Antimicrobial Drugs. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Staphylococcus epidermidis is a gram-positive bacteria that utilizes a glycocalyx/biofilm to adhere to orthopedic implants and other surfaces and resist phagocytosis.