# Anti-Campylobacter Activity of Ternary Copper(II) Complexes with Imine Ligands and 4′-(4-Methylphenyl)-2,2′:6′,2″-Terpyridine

## TL;DR

This paper reports the synthesis and antibacterial activity of two copper complexes against antibiotic-resistant Campylobacter strains in both planktonic and biofilm forms.

## Contribution

The study introduces novel ternary copper(II) complexes with imine ligands and evaluates their anti-Campylobacter efficacy against antibiotic-resistant strains.

## Key findings

- The complexes reduced planktonic Campylobacter cells by 1.3 to 6.9 log CFU/mL at concentrations of 25–400 μg/mL.
- Both complexes modified biofilm ultrastructure and outperformed peracetic acid in reducing sessile cells by ≥2.6 log CFU/mL.
- CL2 controlled biomass formation by 1.2 orders of magnitude, and CL1 showed high penetration into C. jejuni biofilms.

## Abstract

Herein, two Cu­(II) complexes of the type [Cu­(N–N)­(mftpy)]­(PF6)2 (N–N = 4-chloro-N-(pyridin-2-methylene)
aniline (Clmp) or 4-methyl-N-(pyridin-2-methylene)
aniline (memp)­and mftpy = 4′-(4-methylphenyl)-2,2′:6′,2″-terpyridine)
were successfully synthesized and characterized by microanalysis (%
CHN), high-resolution mass spectrometry, Fourier-transform infrared
spectroscopy, and ultraviolet–visible (solution and solid state)
and electron paramagnetic resonance spectroscopies (solution and solid
state). Next, the in vitro antibacterial activity of the [Cu­(Clmp)­(mftpy)]­(PF6)2
CL1 and [Cu­(memp)­(mftpy)]­(PF6)2
CL2 complexes was investigated
in the planktonic and sessile form of Campylobacter
jejuni and Campylobacter coli strains selected from a bank of strains characterized by resistance
to first-line antibiotics. The quantification of planktonic cells
showed a reduction that varied from 1.3 to 6.9 log CFU (colony forming
units)/mL at a minimum inhibitory concentration of 25–400 μg/mL
according to the tested strain. The biofilms suffered modification
in their ultrastructure and showed evidence of the action of both
complexes that surpassed the results with peracetic acid, with a reduction
≥2.6 log CFU/mL of sessile Campylobacter, with control of 1.2 orders of magnitude in the biomass formation
by CL2, and the highest penetration (4.92 μg) of CL1 into the C. jejuni biofilm.
The results identified show that both complexes are biologically active,
activating processes that allow the control of the pathogen in both
lifestyles.