Mechanism Of Bacterial Transfer Research Articles

Effects of Contact Time, Pressure, Percent Relative Humidity (%RH), and Material Type on Listeria Biofilm Adhesive Strength at a Cellular Level Using Atomic Force Microscopy (AFM)

Whereas the transfer of Listeria from surfaces to foods and vice versa has been well documented, little is known about the mechanism of bacterial transfer. The objective of this work is to gain a better understanding of the forces involved in listerial biofilms adhesion using atomic force microscopy (AFM). L. monocytogenes Scott A was grown as biofilms on stainless steel surfaces by inoculating stainless steel coupons with Listeria and incubating the coupons for 48 h at 32 °C with a diluted 1:20 tryptic soy broth. After growth, biofilms were equilibrated over saturated salt solutions at a constant relative humidity (%RH) before measurement of adhesion forces using AFM. The effects of contact time, loading force, and biofilm relative humidity (%RH) suggested that neither contact time, loading force nor biofilm %RH had a significant effect on biofilm adhesiveness at a cellular level (P > 0.05). In a second set of experiments, the influence of material type on biofilm adhesiveness was evaluated using two different colloidal probes (SiO2 and polyethylene). Results showed that the maximum pull-off force and retraction work needed to retract the cantilever for glass (−85.42 nN and 1.610−15 J, respectively) were significantly lower than those of polyethylene (−113.38 nN and 2.7 × 10–15 J, respectively; P < 0.001). The results of this study suggest that Listeria biofilms adhere more strongly to hydrophobic surfaces than hydrophilic surfaces when measured at a cellular level. These results provide important insights that could lead to new ways to remediate and avoid listerial biofilm formation in the food industry.

Static electricity as a mechanism of bacterial transfer during endoscopic surgery

During endoscopic surgery it is often difficult to describe the procedure based on the video screen image. To compensate, the surgeon may point to the monitor to define more exactly what is intended by the verbal cues. Experiments were conducted to determine if the electrostatic field of the monitor could serve as a mechanism of bacterial transfer from the video screen to the patient. A gloved hand traversed the monitor in a standard fashion at varying distances from the screen. The fingertips were then cultured onto blood agar plates. Bacterial growth occurred on 28 of the 30 cultures taken at 1, 2, and 4 cm from the video screen. No growth occurred on any of the 8 cm cultures, or the 20 controls. The number of bacterial colonies cultured from the glove was inversely related to the distance between the glove and video screen (p < 0.001). We conclude the electrostatic field generated by the video monitor could serve as a mechanism of bacterial contamination during endoscopic surgery. Also, we conclude that placing the gloved hand in proximity to the video monitor screen during an operative procedure constitutes a break in sterile technique and must be avoided.

Static electricity as a mechanism of bacterial transfer during endoscopic surgery

Static electricity as a mechanism of bacterial transfer during endoscopic surgery