Pre-medicated gauze with hydrogel and hydrolat of Citrus aurantium var amara (flowers) for the prevention of microbial infections of the damaged skin

1. Introduction. As known, one of the major problems linked to the wound care is the highest probability of infection. Until now, many studies have been developed to modify gauzes made with hydrogel, with the only function to make the wound moist, giving it also an antimicrobial action. However, articles published to date show gauzes modified with the addition of antibiotics or chemical compounds with antimicrobial action or at most essential oils like Melaleuca alternifolia (Tea Tree Oil). Our studies focused on the antimicrobial action of a hydrogel, like the gellan gel, when modified with the addition of hydrolates (Hys), natural waste products of the essential oils production method. 2. Materials and Methods. On seven fungal strains (4 clinical isolates and 3 ATCC strains) and 11 GRAM+ strains both sensible and resistant to antibiotics (6 clinical isolates and 5 ATCC strains), micro-broth dilution test, in line with EUCAT guidelines, was performed. We studied the cytocidal action of 1 commercial Hy (Citrus aurantium var amara - CA), and 4 Hys produced at the DISTAL department of the University of Bologna (Monarda citriodora, M. didyma, M. fistulosa, Lavandula vera). The same test was performed to evaluate the antimicrobial action of preservatives present in the commercial Hy. The cytocidal action of a prototype of hydrogel-impregnated gauze (HIG) modified with 50% v/v of the Hy of CA was evaluated. Ten microL of a suspension of each strain were adsorbed on HIG and incubated overnight at 37°C. Subsequently, the HIGs were printed on Muller Hilton agar medium that was further incubated at 37°C for 24h. To assess the in vivo efficacy, preliminary study of subcutaneous S. aureus infections were developed in 8 Wistar rats by inoculating 100 microL of 1x107 cfu/mL suspension and bandaging only the treated group (n=4) with HIG. Every day, for 5 days, the HIG was changed and the rat was monitored for the development of subcutaneous abscess. 3. Results. Among all the investigated Hys, CA was the most effective (MIC90 ≤3.125% v/v). Tests carried out on preservatives alone did not show any cytocidal action (MIC >50% v/v); while, when associated with the Hy, they enhance the action of hydrolate alone (MIC90=12.5% v/v). Tests performed on HIG showed a cytocidal action on all tested strains. Preliminary in vivo data showed a reduction of about 70% of volume of abscess in treated rats compared to those in control group. 4. Discussion and Conclusions. Our data showed a cytocidal action of commercial Hy of CA vs fungal and bacterial strains potential skin pathogens. Although further in vivo studies are needed to confirm this activity, our study points out to a possible use of the Hy of CA in pre-medicated gauze for the treatment of skin wounds.