The High Impact of Staphylococcus aureus Biofilm Culture Medium on In Vitro Outcomes of Antimicrobial Activity of Wound Antiseptics and Antibiotic

The staphylococcal biofilm-based infections of wounds still pose a significant therapeutical challenge. Treated improperly, they increase the risk of limb amputation or even death of the patient. The present algorithms of infected wound treatment include, among others, the application of antiseptic substances. In vitro wound biofilm models are applied in order to scrutinize their activity. In the present work, using a spectrum of techniques, we showed how the change of a single variable (medium composition) in the standard in vitro model translates not only to shift in staphylococcal biofilm features but also to the change of efficacy of clinically applied wound antimicrobials such as octenidine, polyhexamethylene biguanide, chlorhexidine, hypochlorite solutions, and locally applied gentamycin. The data presented in this study may be of a pivotal nature, taking into consideration the fact that results of in vitro analyses are frequently used to propagate application of specific antimicrobials in hospitals and ambulatory care units.

Facile and Versatile Modification of Cotton Fibers for Persistent Antibacterial Activity and Enhanced Hygroscopicity

Natural fibers with functionalities have attracted considerable attention. However, developing facile and versatile strategies to modify natural fibers is still a challenge. In this study, cotton fibers, the most widely used natural fibers, were partially oxidized by sodium periodate in aqueous solution, to give oxidized cotton fibers containing multiple aldehyde groups on their surface. Then poly(hexamethylene guanidine) was chemically grafted onto the oxidized cotton fibers forming Schiff bases between the terminal amines of poly(hexamethylene guanidine) and the aldehyde groups of oxidized cotton fibers. Finally, carbon-nitrogen double bonds were reduced by sodium cyanoborohydride, to bound poly(hexamethylene guanidine) covalently to the surface of cotton fibers. These functionalized fibers show strong and persistent antibacterial activity: complete inhibition against Escherichia coli and Staphylococcus aureus was maintained even after 1000 consecutive washing in distilled water. On the other hand, cotton fibers with only physically adsorbed poly(hexamethylene guanidine) lost their antibacterial activity entirely after a few washes. According to Cell Counting Kit-8 assay and hemolytic analysis, toxicity did not significantly increase after chemical modification. Attributing to the hydrophilicity of poly(hexamethylene guanidine) coatings, the modified cotton fibers were also more hygroscopic compared to untreated cotton fibers, which can improve the comfort of the fabrics made of modified cotton fibers. This study provides a facile and versatile strategy to prepare modified polysaccharide natural fibers with durable antibacterial activity, biosecurity, and comfortable touch.

In vitro activity of a novel compound, Mul-1867, against clinically significant fungi Candida spp. and Aspergillus spp

There is an urgent need for new antifungal compounds to treat various types of fungal infections, including pulmonary infections. This study was designed to investigate the potency of a novel compound (Mul-1867) against Candida spp. and Aspergillus spp. isolated from patients with fungal pneumonia, cystic fibrosis and chronic obstructive pulmonary disease. Mul-1867 was highly effective against susceptible control strains as well as resistant clinical isolates, with minimum fungicidal concentrations (MFCs) varying from 0.06 µg/mL to 0.5 µg/mL. It was also highly effective against pre-formed 48-h-old biofilms formed by yeasts and moulds. The half-minimal biofilm eradication concentration (MBEC₅₀) was equal to the MFC. The minimum biofilm eradication concentration to eliminate 90% of biofilms (MBEC₉₀) varied from 1 × to 4 × MFC. Scanning electron microscopy revealed morphological changes accompanied by the release of intracellular material from the fungal cells following exposure to Mul-1867. Furthermore, an increased concentration of nucleic acids was found in the medium after 5 min and 20 min of Mul-1867 treatment, indicating leakage of cytoplasmic contents. Overall, these data indicate that Mul-1867 may be a promising inhaled antifungal agent for the treatment and prevention of fungal respiratory infections.

Injectable cationic hydrogels with high antibacterial activity and low toxicity

We prepared injectable cationic hydrogels with strong antibacterial activity and remarkably low toxicity by in situ thiol–ene “click” reaction between dimethacrylate terminated poly(hexamethylene guanidine) (PHMGDMA) and poly[oligo(ethylene) glycol mercaptosuccinate] (POEGMS) under physiological conditions.