JAC Advance Access originally published online on June 20, 2006
Journal of Antimicrobial Chemotherapy 2006 58(2):455-457; doi:10.1093/jac/dkl245
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Reversing methicillin resistance in MRSA using a bacterial transforming agent
Department of Microbiology, Southern General Hospital Glasgow G51 4TF, Scotland, UK
Received 20 March 2006; returned 11 April 2006; revised 15 May 2006; accepted 22 May 2006
*Corresponding author. Tel: +44-1412011710; Fax: +44-1412011704; E-mail: Stephanie.Dancer{at}sgh.scot.nhs.uk
Background: Antimicrobial resistance in staphylococci remains a significant problem in the clinical management of infections. New therapeutic entities are required for the prophylaxis and treatment of staphylococcal infection including those caused by methicillin-resistant Staphylococcus aureus (MRSA). Potential candidates include bacterial transforming agents (BTAs), compounds that can potentiate the activity of cell-wall-active antimicrobials by hypersensitizing the bacterial cell wall to the bactericidal effects of these drugs. BTAs have been found to inhibit MRSA in vitro when administered in combination with established antibiotics.
Objectives: To examine the antimicrobial potential of a known BTA (BTA 19976a) on strains of MRSA in vitro.
Methods: Etest and timekill methodologies were employed to assess the inhibitory potential of BTA at 10% w/v on strains of E-MRSA-3, E-MRSA-15 and E-MRSA-16.
Results: Etests demonstrated a reduction in the oxacillin MIC for E-MRSA-3, E-MRSA-15 and the NCTC 12493 reference strain of MRSA when exposed to BTA at 10% w/v. Timekill assays similarly demonstrated a reduction in viable counts for organisms exposed to methicillin at 40 mg/L + BTA at 10% w/v, compared with methicillin alone, an effect which varied in cidality, pattern of killing and regrowth between strains.
Conclusions: The antimicrobial effects of this BTA on MRSA are encouraging and warrant further investigation with large numbers of different epidemic strains and a comprehensive PK/PD evaluation. This could lead to new therapeutic entities for the prophylaxis and treatment of staphylococcal infections.
Keywords: anti-infective development , drug susceptibility testing , ß-lactams , cell wall , hypersensitizing agent