The acceleration of inactivating viable cells of Escherichia coli (E. coli), by using new direct and indirect innovative methods, is the targeted method of using an atmospheric pressure plasma jet (APPJ) operated by an AC high-voltage power source with variable frequency up to 60 kHz and voltage ranging from 2.5 to 25 kV. Discharges using dry argon (0% O₂) discharges and different wet argon discharges using admixtures with O₂/Ar ratios ranging from 0.25% to 1.5% were studied. The combined effects of dry and wet argon discharges, direct and indirect exposure using a mesh controller, and hollow magnets were studied to reach a complete bacterial inactivation in short application times. Survival curves showed that the inactivation rate increased as the wettability increased. The application of magnetized non-thermal plasma discharge with a 1.5% wetness ratio causes a fast inactivation rate of microbes on surfaces, and a dramatic decrease of the residual survival of the bacterial ratio due to an increase in the jet width and the enhanced ability of fast transport of the charges to viable cells, especially at the edge of the Petri dish. The membrane damage of E. coli mechanism factors in the activation process by APPJ is discussed.

Dry argon (Ar) discharge and wet oxygen/argon (O₂/Ar) admixture discharge for alternating current atmospheric pressure plasma jets (APPJs) were studied for Ar discharges with flow rates ranging from 0.2 to 4 slm and for O₂/Ar discharges with different O₂ ratios and flow rates ranging from 2.5 to 15 mslm. The voltage–current waveform signals of APPJ discharge, gas flow rate, photo-imaging of the plasma jet length and width, discharge plasma power, axial temperature distribution, optical emission spectra, and irradiance were investigated. Different behavior for varying oxygen content in the admixture discharge was observed. The temperature recognizably decreased, axially, far away from the nozzle of the jet as the flow rate of dry argon decreased. Similar behavior was observed for wet argon but with a lower temperature than for dry argon. The optical emission spectra and the dose rate of irradiance of a plasma jet discharge were investigated as a function of plasma jet length, for dry and wet Ar discharges, to determine the data compatible with the International Commission on Non-Ionizing Radiation Protection (ICNIRP) data for irradiance exposure limits of the skin, which are suitable for the disinfection of microbes on the skin without harmful effects, equivalent to 30 μJ/mm².

OBJECTIVE: To estimate the prevalence and antibiotic susceptibility of the Gram-negative bacteria isolated from 2 hospitals in Makkah. METHODS: This study was undertaken in 2 main tertiary care hospitals namely; Al-Noor Specialist Hospital, and Hera Hospital in Makkah, Kingdom of Saudi Arabia from October 2005 to March 2006. A total of 1137 Gram-negative bacteria were identified in non-duplicate clinical specimens obtained from 965 patients of various body sites infections. Demographic data, identity of microorganisms, and antimicrobial susceptibilities were obtained from medical and laboratory records. RESULTS: The most prevalent Gram-negative bacteria were Escherichia coli (31.6%), and Pseudomonas aeruginosa (31.2%), followed by Acinetobacter baumannii (10.8%), Klebsiella pneumoniae (8.3%), Klebsiella sp. (6.2%), Haemophilus influenzae (3.7%), Proteus sp. (3.3%), and Enterobacter sp. (1.9%). Results demonstrated that Gram-negative bacteria have a high rate of resistance to commonly used antibiotics. Furthermore, multi-drug resistance was also common in this study. CONCLUSION: Our data showed a high rate of resistance among Gram-negative pathogens in comparison with other countries in the world. The implementation of monitoring programs is an important part of the prevention strategy against the development of antibiotic resistance in hospitals.

Acceleration of antibacterial properties is the targeted fashion of the recent part of our project by studying different techniques, on the culture media of E. coli., including the non-thermal effect using atmospheric pressure plasma jet (APPJ) and the non-thermal effects combined with the photocatalytic effects using APPJ coupled with a titanium dioxide TiO₂ precursor. The electrical, non-thermal, and optical characteristics of the laminar and turbulent mode flow of a dry argon discharge afterglow using APPJ were vital in the study of the antibacterial properties, with the measured characteristics in the laminar mode flow as follows: frequency 25 kHz; applied voltage 11.2 kV; flow rate, 2.4 slm; power, 2.34 W; jet temperature, 340 K; jet length, 11.5 mm; jet width, 1.6 mm; energy, 96 mJ; and Reynolds number, 2819. Under all the measured characteristics of maximum laminar flow mode with the flow rate, 2.4 slm, the optical emission spectroscopy data of APPJ for dry Ar discharge and for wet argon (coupled with TiO₂ precursor with the emerging jet) were measured. Survival curves of live microbes confirmed that as TiO₂ precursor concentration increases in the range from 0 to 0.5 g l⁻¹, the deactivation rate of E. coli increases due to the photocatalytic disinfection performance, because of the TiO₂ precursor concentrations dosage enhances the effect of the incident plume of the non-thermal jet, leading to the generation of more active substances that can be absorbed by the cells causing acceleration of the sterilization efficiency.

An experimental study was performed on a low-density plasma discharge using two different configurations of the plasma cell cathode, namely, the one mesh system electrodes (OMSE) and the one mesh and three system electrodes (OMTSE), to determine the electrical characteristics of the plasma such as current–voltage characteristics, breakdown voltage (V_B), Paschen curves, current density (J), cathode fall thickness (d_c), and electron density of the treated sample. The influence of the electrical characteristics of the plasma fluid in the cathode fall region for different cathode configuration cells (OMSE and OMTSE) on the performance quality of a surgical gown was studied to determine surface modification, treatment efficiency, exposure time, wettability property, and mechanical properties. Over a very short exposure time, the treatment efficiency for the surgical gown surface of plasma over the mesh cathode at a distance equivalent to the cathode fall distance d_c values of the OMTSE and for OMSE reached a maximum. The wettability property decreased from 90 to 40% for OMTSE over a 180 s exposure time and decreased from 90 to 10% for OMSE over a 160 s exposure time. The mechanisms of each stage of surgical gown treatment by plasma are described. In this study, the mechanical properties of the untreated and treated surgical gown samples such as the tensile strength and elongation percentage, ultimate tensile strength, yield strength, strain hardening, resilience, toughness, and fracture (breaking) point were studied. Plasma had a more positive effect on the mechanical properties of the OMSE reactor than those of the OMTSE reactor.