The minimum inhibitory concentration susceptibility data for a few medically significant bacteria are:
S. aureus: 0.25 μg/mL to 4.0 μg/mL
S. aureus (methicillin resistant or MRSA): 1 μg/mL to 138 μg/mL
S. epidermidis: ≤0.12 μg/mL to 6.25 μg/mL

Side effects
Serum vancomycin levels may be monitored in an effort to reduce side effects, although the value of such monitoring has been questioned. Peak and trough levels are usually monitored, and for research purposes, the area under the concentration curve is also sometimes used. Toxicity is best monitored by looking at trough values.Common adverse drug reactions (≥1% of patients) associated with IV vancomycin include: local pain, which may be severe, and thrombophlebitis. Damage to the kidneys (nephrotoxicity) and to the hearing (ototoxicity) were side effects of the early impure versions of vancomycin, and these were prominent in the clinical trials conducted in the mid-1950s. Later trials using purer forms of vancomycin found nephrotoxicity is an infrequent adverse effect (0.1% to 1% of patients), but this is accentuated in the presence of aminoglycosides.Rare adverse effects (<0.1% of patients) include: anaphylaxis, toxic epidermal necrolysis, erythema multiforme, red man syndrome, superinfection, thrombocytopenia, neutropenia, leukopenia, tinnitus, dizziness and/or ototoxicity, and DRESS syndrome.Vancomycin can induce platelet-reactive antibodies in the patient, leading to severe thrombocytopenia and bleeding with florid petechial hemorrhages, ecchymoses, and wet purpura.Vancomycin has traditionally been considered a nephrotoxic and ototoxic drug, based on observations by early investigators of elevated serum levels in renally impaired patients who had experienced ototoxicity, and subsequently through case reports in the medical literature.
The organization of the modules necessary to biosynthesize Vancomycin is shown in Figure 1. In the biosynthesis of Vancomycin, additional modification domains are present, such as the epimerization (E) domain, which isomerizes the amino acid from one stereochemistry to another, and a thioesterase domain (TE) is used as a catalyst for cyclization and releases of the molecule via a thioesterase scission. A set of NRPS enzymes (peptide synthase VpsA, VpsB, and VpsC) are responsible for assembling the heptapeptide. (Figure 2). VpsA codes for modules 1, 2, and 3. VpsB codes for modules 4, 5, and 6, and VpsC codes for module 7. The vancomycin aglycone contains 4 D-amino acids, although the NRPSs only contain 3 epimerization domains. The origin of D-Leu at residue 1 is not known. The three peptide syntheses are located at the start of the region of the bacterial genome linked with antibiotic biosynthesis, and span 27 kb.β-hydroxytyrosine (β-HT) is synthesized prior to incorporation into the heptapeptide backbone. L-tyrosine is activated and loaded on the NRPS VpsD, hydroxylated by OxyD, and released by the thioesterase Vhp. The timing of the chlorination by halogenase VhaA during biosynthesis is currently undetermined, but is proposed to occur before the complete assembly of the heptapeptide.After the linear heptapeptide molecule is synthesized, vancomycin has to undergo further modifications, such as oxidative cross-linking and glycosylation, in trans by distinct enzymes, referred to as tailoring enzymes, to become biologically active (Figure 3). To convert the linear heptapeptide to cross-linked, glycosylated vancomycin, six enzymes, are required.