# Anti-Bacterial Action of Plasma Multi-Jets in the Context of Chronic Wound Healing
## 3 Results
### Large Surface Resistant Bacterial Lawn Inactivation with Scanning Protocols  
The Figure 10 presents the multi-spot plasma treatment of resistant _P. aeruginosa_, _S. aureus_ and _E. coli_ inoculated agar substrate, the three strains being collected from patients suffering from chronic wounds. The translation scanning mode was processed for 1, 5 and 10 min in different regions of the agar plate. There may be some overlap of the treatment in one zone (for 1, 5 and 10 minute' plasma exposure) with the neighboring zones. Because of this possible artifact, the decontamination action is discussed for the central band of each of the three different treatment duration zones. For each of the three strains, the multi-spot scanning protocol results in a time-dependent inactivation efficiency. Nevertheless, even for the shortest, one minute treatment time, the bacterial lawn growth is almost already fully and homogenously inhibited. It is observed that the _P. aeruginosa_, _S. aureus_ present a higher sensitivity than _E. coli_ to the plasma treatment. Figure 10 presents the images of the bacterial lawn after the plasma treatment and a 24-h incubation period, but it was also verified that even after an incubation period as long as seven days the bacterial lawn growth was still completely inhibited. Figure 9: Inactivation of _P. aeruginosa_ ATCC®9027 TM and of resistant _P. aeruginosa_ with the diffuse mode plasma applicator. H24 images of the _P. aeruginosa_ ATCC®9027 TM inoculated sample exposed at H0 to 0 (**a**), 1 (**b**), 5 (**c**) and 10 (**d**) minute plasma treatment and of resistant _P. aeruginosa_ inoculated sample exposed at H0 to 0 (**e**), 1 (**f**), 5 (**g**) and 10 (**h**) minute plasma treatment. In terms of a patient's wound plasma treatment, it is important to assess the bactericidal action of plasma jets not only on a single strain inoculum but also for a mixture of different strains, as wounds are most of the time colonized by a symbiotically living bacteria assembly. Figure 11 presents the multi-spot plasma treatment of a combination of resistant _P. aeruginosa_, _S. aureus_ and _E. coli_ inoculum spread over an agar substrate. The zigzag scanning mode was processed for 1, 5 and 10 min in one selected region of the agar plate. This scanning mode was selected to mimic the way medical doctors or nurses may treat a large wound with a plasma device. It is observed that after a one-minute plasma treatment, the _P. aeruginosa_ inactivation is already achieved, as the green color, indicative of this bacteria colonization following a 24-h incubation, has vanished. A 5-min long treatment leads to the full inactivation of the three bacteria strains in the scanned region, while some circle shaped colonies are observed on the edges of the treated zone. These circle shape colonies are likely to be assigned to _E. coli_ persistence, as this specific morphology was already observed in the single bacteria inoculation experiment documented in Figure 10. A 10-min plasma treatment leads to the  
Figure 11: Inactivation of large surface bacterial lawn composed of a mixture of three resistant strains with the multi-spot plasma applicator applied in the zigzag scanning mode. H24 images of the inoculated sample exposed at H0 to 1, 5 and 10-min plasma treatment. The dashed rectangle zone indicates the plasma treated region. The size of the treated zone is about 32 cm\({}^{2}\). Figure 10: Inactivation of large surface resistant bacterial lawn with the multi-spot plasma applicator with the translation scanning mode. On top, images of resistant _P. aeruginosa_ (**left**), _S. aureus_ (**middle**) and _E. coli_ (**right**) 24 h after their inoculation. In the bottom, H24 images of the _P. aeruginosa_ (**left**), _S. aureus_ (**middle**) and _E. coli_ (**right**) inoculated sample exposed at H0 to 1, 5 and 10-min plasma treatment as indicated between the vertical dashed lines. The size of each treated zone is about 40 cm\({}^{2}\).