Light micrograph (LM) of Vancomycin (antibiotic) crystals. Vancomycin is an antibiotic used in the prophylaxis and treatment of infections caused by Gram-positive bacteria. It acts by inhibiting proper cell wall synthesis. It is a branched tricyclic, glycosylated, glycopeptide produced by the fermentation of the actinomycete bacterium Amycolatopsis orientalis (formerly Nocardia orientalis). A synthetic derivative, vancomycin hydrochloride, was developed in the early 1980s and generic versions of the drug are now available. It is often reserved as the drug of last resort. With the increasing prevalence of antibiotic-resistant bacteria, vancomycin has increasingly become a first line therapy when faced with Staphylococcus aureus infections in a patient where antibiotic resistance can be anticipated. Magnification: x40 when shortest axis printed at 25 millimetres.