The original work presented in this thesis provides examples of the unique chemistry of a helium/oxygen Kilohertz plasma jet and its antimicrobial activity against a cohort of clinically relevant microorganisms termed the ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter cloacae). The potential of non-thermal plasma to attenuate quorum sensing controlled bacterial virulence is demonstrated in Gram-negative bacteria with further elucidation undertaken to examine how examples of plasma produced reactive species; the hydroxyl radical and peroxynitrite anion affect acyl homoserine lactones (extra-cellular molecules utilised by Gram-negative bacteria in quorum sensing). This thesis provides further evidence of non-thermal plasmas antimicrobial efficacy and presents new evidence of how non-thermal plasma may attenuate bacterial quorum sensing controlled virulence through modification of acyl homoserine lactones in a chain length-dependent manner. This work contributes new knowledge and understanding of non-thermal plasmas interaction with bacteria and its potential for the amelioration of hospital acquired infections.