Allyl isothiocyanate from crucifers potentiates β-lactam activity against methicillin-resistant Staphylococcus aureus

Abstract

Introduction: Increasing prevalence of methicillin-resistant Staphylococcus aureus (MRSA) worldwide with limited therapeutic options is a growing public health concern. Isothiocyanates (ITCs) from crucifers have been shown to possess antibacterial actions against MRSA by antagonizing its resistance mechanisms. Allyl isothiocyanates (AITC) is the predominant isothiocyanates (ITC) of commonly consumed cruciferous vegetables such as brussels, mustard, cabbage, cauliflower and kale. Objectives: The aim of this study is to evaluate the potentiation effect of AITC on ampicillin and cefixime against clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) using broth microdilution method and checkerboard methods. Results: AITC showed a promising antibacterial activity against a panel of clinical isolates of MRSA when used in alone. However, β-lactam antibiotics like ampicillin and cefixime had little or no activity against MRSA confirming their multi-drug resistance. When AITC combined with ampicillin and cefixime, MIC was reduced by ≥ 4 fold as compared to their monotherapy, evidencing a synergistic effect of AITC, as defined by a FICI of ≤0.5. Conclusions: AITC showed promising synergistic and potentiation effect on ampicillin and cefixime at sub-MIC level against multi-drug resistant MRSA. This modulatory effect of AITC on β-lactam antibiotics could be useful as a synergistic therapeutic pair in combating MRSA infection in a hospital or community settings. Keywords: Allyl isothiocyanate; Crucifers potentiates; β-lactam activity; Methicillin-resistant Staphylococcus aureus