Susceptibility of Some Clinically Resistant Bacterial Isolates to Thyme Essential Oil, Chitosan and Lactobacillus reuteri

Abstract

Numerous avenues are currently being investigated to curtail multidrug resistance.  The antibacterial activity of naturally derived agents, including thyme essential oil, chitosan and a probiotic Lactobacillus strain was screened against clinically resistant isolates of Staphylococcus aureus, Escherichia coli and Klebsiella. Thyme essential oil was hydro-distilled from wild Thymus capitatus and its chemical composition was profiled by Gas Chromatography-Mass Spectroscopy. Chitosan was prepared from shrimp shells and characterised by infrared spectroscopy. The antibiotic sensitivity pattern of the clinical isolates of Staphylococcus aureus, Escherichia coli and Klebsiella were investigated, and their susceptibility to the prepared natural agents was assessed by agar well diffusion technique. Both Gram-negative isolates exhibited similarly high resistance rates to piperacillin, co-amoxiclav, cephalothin, ceftazidime and imipenem. Meanwhile, 83% of S. aureus isolates were of the MRSA phenotype. The tested isolates displayed varying degrees of susceptibilities to the tested natural agents where thyme essential oil exhibited the highest inhibitory effect followed by chitosan and the culture supernatant of L. reuteri respectively. Albeit the high resistance displayed by both E. coli and Klebsiella isolates, they were the most susceptible to thyme essential oil. Contrariwise, L. reuteri exhibited the highest inhibitory effect against S. aureus isolates. Intriguingly, there was a general tendency for higher effectiveness of the natural products tested against the most resistant isolates implying that these natural products may have a resistance modifying potential. The presently investigated natural agents hold a promising potential against clinically significant multidrug resistant bacteria.