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Technical Abstract Details

Title Effect of trans-cinnamaldehyde, beta-resorcylic acid, carvacrol, thymol and eugenol in increasing the sensitivity of multidrug-resistant <i>Salmonella</i> Typhimurium DT104 to antibiotics
Presenter Anup Kollanoor Johny, Thomas Hoagland, Kumar Venkitanarayanan, Univ of Connecticut, Storrs, CT
Abstract <i>Salmonella typhimurium</i> DT 104 (DT) has emerged into a major health concern due to its resistance to five antibiotics, including ampicillin, chloramphenicol, streptomycin, sulfonamides and tetracycline. Cattle, pigs and poultry serve as the reservoir of the pathogen, thereby potentially contaminating the food supply. DT could be transferred to humans through consumption or handling of contaminated foods, resulting in infections difficult to treat with antibiotics. Thus there is a need for effective interventions to control DT in food animals.<br />This study investigated the efficacy of plant-derived antimicrobials, namely <i>trans</i>-cinnamaldehyde, &#946;- resorcylic acid, carvacrol, thymol and eugenol or their combination for increasing the sensitivity of DT to five antibiotics. Since plant-derived antimicrobials contain different chemical groups in the structure, their antimicrobial activity is attributed to multiple mechanisms, which also prevent bacteria from developing resistance.<br />The sub-inhibitory concentrations (SICs) of each antimicrobial or their combination containing concentrations lower than the individual SICs were added to tryptic soy broth (TSB) supplemented with antibiotics at their break points for resistance. DT was inoculated into TSB at ~6 log CFU/ml and growth (optical density) was determined at 600 nm before and after incubation at 37<sup>o</sup>C for 24 h. Appropriate controls were included. Duplicate samples were assayed and the experiment was replicated three times.<br />Trans-cinnamaldehyde increased the sensitivity of DT (<i>P </i>&#60; 0.05) toward all five antibiotics, thereby making the pathogen susceptible to the drugs. &#946;-resorcylic acid made DT susceptible to four antibiotics, whereas carvacrol increased the sensitivity to chloramphenicol, sulphamethoxazole and tetracycline. The combination of five plant-derived molecules was more effective than the individual ones (<i>P</i> &#60; 0.05) in making DT susceptible to the five antibiotics. Results indicate that these natural molecules individually and synergistically increased the sensitivity of DT towards the antibiotics and could potentially be used to control the pathogen in food animals.
Year/Location2009 IFT Annual Meeting, June 6-9, Anaheim, CA
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