Antimicrobial effects of the organosulfur compounds diallyl monosulphide, diallyl disulphide, and kiallyl trisulphide found in allium sativum against planktonic methicillin-resistant staphylococcus aureus (MRSA) and MRSA biofilms

Kelly Knapp, The College of Wooster

Abstract

The increasing frequency of methicillin resistant Staphylococcus aureus (MRSA) and vancomycin intermediate S. aureus (VISA) are causing care providers to consider alternative forms of treatment. Consequently, the study of botanicals with antimicrobial properties is becoming important. One such botanical, Allium sativum (garlic) contains organosulfur compounds such as diallyl monosulphide (DS), diallyl disulphide (DDS) and diallyl trisulphide (DTS), which are antimicrobially active. The purpose of this work was to investigate the antimicrobial activity of these compounds against S. aureus. Antimicrobial susceptibility testing was performed on S. aureus ATCC 29213, S. aureus ATCC 43300, MRSA 932284, methicillin susceptible S. aureus (MSSA T001), and VISA MU50 using pure garlic oil (GO), DS, DDS, DTS, and oxacillin (OXA) as a comparator in minimal inhibitory concentration (MIC) trays. Checkerboard Synergy MIC trays containing combinations of OXA with GO, DS, DDS, or DTS were tested against the S. aureus isolates. Time kill and synergy time kill was performed to test the rate of bactericidal activity of the GO, DDS, DTS, and OXA against the SA isolates. Biofilms of SA 29213, SA 43300, MSSA, and MRSA were grown and exposed to MIC trays and CS trays containing GO, DS, DDS, DTS, and OXA to determine the minimal biofilm eradication concentration (MBEC) values of these compounds alone and in combination with OXA. The MIC results for S. aureus ATCC 29213, MSSA T001, S. aureus ATCC 43300, MRSA 932284, and VISA MU50 respectively were: GO 128, >128, 64, >128, and 64_g/ml; DS >128 _g/ml, DDS 128, 128, 128, 64, and 128_g/ml; and DTS 128, 128, 4 64, 8, and 128_g/ml. Synergistic results were observed combining OXA with GO, DS, DDS, and DTS against the planktonic and biofilm isolates tested. Time kill was performed at 1X, 2X and 4X the MIC of GO, DDS, DTS and OXA. The GO at 1X killed the MRSA 932284 at 4hrs with no regrowth in comparison to the OXA at 1X that killed the MRSA 932284 at 6hrs with regrowth occurring. At 1X, DDS and DTS killed the MRSA 932284 at 4hrs with regrowth occurring at 6hrs. Synergy time kill results were observed combining OXA with the GO, DDS, and DTS against S. aureus ATCC 29213, MSSA T001, S. aureus ATCC 43300, MRSA 932284, and VISA MU50. The MBEC results for S. aureus ATCC 29213, MSSA T001, S. aureus ATCC 43300 and MRSA 932284 respectively were: GO >128, >128, >128, and 128_g/ml; DDS >128_g/ml for all, DTS >128, >128, 128, and 128_g/ml; and OXA >16_g/ml for all. This study suggests that GO and DTS were the most effective against planktonic MRSA 932284 and MRSA 932284 biofilms alone and in combination with OXA.