title: Antimicrobial activity of a new preservative for multiuse ophthalmic solutions.
abstract: OBJECTIVE
  The aim of this study was to examine the antimicrobial activity and the preservative efficacy of a novel preservative solution containing sodium hydroxymethyl glycinate (SHMG) and edetate disodium (EDTA), which is used for preservation of some commercial ophthalmic formulations.
  
  
  METHODS
  In vitro susceptibility assays were performed against several gram-positive (Staphylococcus aureus, Staphylococcus epidermidis, and Bacillus cereus) and gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria representative of the microbial flora of epithelial surfaces or colonizing the conjunctiva, as well as against Candida albicans and Aspergillus niger. Using different concentrations of SHMG alone or in combination with EDTA, the minimal inhibitory and microbicidal concentrations against these organisms were assessed. In addition, 8 brands of multidose eye drops containing 0.002% SHMG and 0.1% EDTA as preservative were tested for antimicrobial activity using the antimicrobial effectiveness test recommended by the international pharmacopoeias.
  
  
  RESULTS
  The minimal inhibitory and bactericidal/fungicidal concentration values of SHMG ranged from 0.0025% to 0.0125% for bacteria and from 0.125% to 0.50% for mold and yeast. Susceptibility testing demonstrated that the addition of EDTA substantially increased the SHMG activity against all bacterial and fungal strains. The preservative effectiveness test was applied to commercial eye drops. All the drop solutions met the criteria reported by the U.S. Pharmacopeia for parenteral and ophthalmic preparations. All products also satisfied the major acceptance criteria of the European Pharmacopeia with respect to the antifungal activity. With regard to the antibacterial activity, the less-stringent criteria of the European Pharmacopeia were fulfilled.
  
  
  CONCLUSIONS
  The present study demonstrates the efficacy of a novel preservative for ophthalmic solutions (SHMG/EDTA) and its activity in protecting selected commercial artificial tears against microbial contamination.
authors: Department of Experimental Pathology, Medical Biotechnology, Infectivology and Epidemiology, University of Pisa, Pisa, Italy. emilia.ghelardi@med.unipi.it
authors: Emilia
authors: E
authors: Ghelardi
authors: Francesco
authors: F
authors: Celandroni
authors: Sokhna A
authors: SA
authors: Gueye
authors: Sara
authors: S
authors: Salvetti
authors: Mario
authors: M
authors: Campa
authors: Sonia
authors: S
authors: Senesi
mesh_terms: D000890:Anti-Infective Agents / Q000737:chemistry / Q000494:pharmacology*; D001234:Aspergillus niger / Q000187:drug effects; D002176:Candida albicans / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004492:Edetic Acid / Q000737:chemistry / Q000494:pharmacology*; D006090:Gram-Negative Bacteria / Q000187:drug effects; D006094:Gram-Positive Bacteria / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D009883:Ophthalmic Solutions / Q000737:chemistry / Q000494:pharmacology*; D011310:Preservatives, Pharmaceutical / Q000737:chemistry / Q000494:pharmacology*; D012521:Sarcosine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology
chemical_list: D000890:Anti-Infective Agents; D009883:Ophthalmic Solutions; D011310:Preservatives, Pharmaceutical; C020420:monomethylolglycine; D004492:Edetic Acid; D012521:Sarcosine