Evaluation of the effects of sound exposure and low field electromagnetism on growth and antibiotics susceptibility of some microorganisms

Abstract

Background: The emergence of antibiotic-resistant microorganisms has been largely associated with drug misuse, drug abuse, and indiscriminate disposal of drugs; however, the interactions between some environmental factors and antibiotic resistance by microorganisms have been understudied. In this study, the effects of sound and electromagnetic field on the growth and antibiotic susceptibility of selected microorganisms to antibiotics were investigated. Results: Microorganisms used include Gluconobacter oxydans ATCC 19,357, Rhodobacter sphaeroides ATCC 17,023, Citrobacter freundii ATCC 33,128, Yersina pestis ATCC 11,953, Bacillus subtilis 6633, Acetobacter aceti ATCC 15,973, Escheri-chia coli ATCC 25,922, Pseudomonas aeuriginosa ATCC 9027, Streptococcus pyogenes ATCC 19,613, Klebsiella pneumonia ATCC 25,955, Staphylococcus aureus ATCC 25,923 and Serratia marcescens ATCC 14,766. The antibiotics used were: Cip-rofloxacin 5 μg, Imipenem 10 μg, Ampicillin 10 μg, Ceftazidime 30 μg and Tetracycline 30 μg for Gram-negative bacteria while Pefloxacin 10 μg, Gentamycin 10 μg, Amplicillin + Cloxacillin 30 μg, Cefuroxime 20 μg, Amoxacillin 30 μg, Ceftriaxone 25 μg, Ciprofloxacin 10 μg, Streptomycin 30 μg, Co-trimoxazole 30 μg, and Erythromycin 10 μg for Gram-positive bacteria, respectively. Acoustic treatment had varying effects on the antibiotics susceptibility profile of all test bacterial culture. Before exposure, P. aeruginosa had the highest zone of inhibition of 34 ± 3.4 mm, while B. subtilis had least inhibition zone of 12 ± 2.8. After exposure to acoustic treatment at 5000 Hz/90 dB at 72 h, C. freundii had highest zone of inhibition of 32 ± 0.7 mm and the least zone of 11 ± 1.4 mm observed in P. aeruginosa. At 1125 Hz/80 dB after 72 h, R. sphaeroides had highest zone of 34 ± 0.7 mm while A. aceti had least zone of inhibition of 10 ± 0 mm. Effect of electromagnetic flux treatment of 15 min showed E. coli to be the most inhibited having a growth rate of 0.08 log cfu/ mL, antibiotics testing showed G. oxydans to have the highest zone of inhibition of 28 ± 3.5 mm and least zone was observed in B. subtilis having a zone of 13 ± 2.8 mm. Conclusion: This study showed that environmental factor such as sound and electromagnetic flux (EMF) could interfere with the physiology of bacteria including resistance/susceptibility to antibiotics. However, further investigation will be needed to understand full mechanisms of action of sound and electromagnetic field on bacteria.