Preliminary evaluation of the synergistic effects of methanol extracts of garlic and some conventional antimicrobial agents on bacterial isolates from HVS

Abstract

The emergence of multiple drug resistant organisms has made the treatment combinations of conventional drugs with medicinal plants against resistant microorganisms necessary. Therefore, this work aimed to discover how the potency of some conventional antimicrobial drugs can be increased by combining them with the natural antimicrobial potentials of garlic. This was carried out using ethanolic extracts of garlic in combination with the drugs against clinical bacterial isolates obtained from high vaginal swab (HVS) using the agar overlay inoculum susceptibility disc method. A total of 24 clinical bacterial isolates obtained after successive sub-culturing were tested against the antibiotics alone and after their combinations with garlic extracts. The number of the clinical isolates reduced upon identification to just six different bacterial species: Escherichia coli, Enterococcus sp., Staphylococcus aureus, Enterobacter sp., Citrobacter sp. and Klebsiella sp. Result obtained showed that when only antibiotic sensitivity discs alone was used, the isolates showed resistance to them in varying degrees. For example, isolate 2B, a Citrobacter sp. showed resistance to 9 of the 10 antibiotics, followed by isolate 4, Klebsiella sp. which resisted 8 antibiotics and isolates 3 (Escherichia coli) and 7 (Enterobacter sp.) which resisted 5 antibiotics each. In terms of antibiotics, resistance was shown most to nitrofurantoin, with 16 out the 24 isolates resisting it and ampicillin, 12 isolates. However, combinations of the antibiotics with methanolic extracts of garlic reduced the incidence of resistance to significant levels, reaching 100% reductions in resistance in many cases. Thus the use of garlic extract in combinations with antibiotics positively increased the killing abilities of most of them. These are clearly positive results that should be adequately exploited for humanity’s benefit.

Key words: Antibiotics, garlic, extract, synergism, resistance, antagonism.