*Article* **Susceptibility of Multidrug-Resistant Bacteria, Isolated from Water and Plants in Nigeria, to Ceragenins**

**Marjan M. Hashemi <sup>1</sup> , Augusta O. Mmuoegbulam <sup>2</sup> , Brett S. Holden 1, Jordan Coburn <sup>1</sup> , John Wilson 1, Maddison F. Taylor 1, Joseph Reiley 1, Darius Baradaran 1, Tania Stenquist 1, Shenglou Deng <sup>1</sup> and Paul B. Savage 1,\***


Received: 12 October 2018; Accepted: 3 December 2018; Published: 6 December 2018

**Abstract:** The continuous emergence of multidrug resistant pathogens is a major global health concern. Although antimicrobial peptides (AMPs) have shown promise as a possible means of combatting multidrug resistant strains without readily engendering resistance, costs of production and targeting by proteases limit their utility. Ceragenins are non-peptide AMP mimics that overcome these shortcomings while retaining broad-spectrum antimicrobial activity. To further characterize the antibacterial activities of ceragenins, their activities against a collection of environmental isolates of bacteria were determined. These isolates were isolated in Nigeria from plants and water. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of selected ceragenins and currently available antimicrobials against these isolates were measured to determine resistance patterns. Using scanning electron microscopy (SEM), we examined the morphological changes in bacterial membranes following treatment with ceragenins. Finally, we investigated the effectiveness of ceragenins in inhibiting biofilm formation and destroying established biofilms. We found that, despite high resistance to many currently available antimicrobials, including colistin, environmental isolates in planktonic and biofilm forms remain susceptible to ceragenins. Additionally, SEM and confocal images of ceragenin-treated cells confirmed the effective antibacterial and antibiofilm activity of ceragenins.

**Keywords:** ceragenin; multidrug-resistant bacteria; biofilm; antimicrobial peptides; colistin
