Chicken cathelicidins display antimicrobial activity against multiresistant bacteria without inducing strong resistance

Abstract

The increased prevalence of multidrug-resistant (MDR) bacteria in combination with the relatively limited development of new antibiotics presents a serious threat to public health. In chicken, especially Extended-Spectrum ß-Lactamase (ESBL) carrying Enterobacteriaceae are often asymptomatically present but can infect humans. Due to their broad range antimicrobial activity cathelicidins and other host defence peptides, are considered to be an attractive alternative to conventional antibiotics. In this study, the antimicrobial activity of three chicken cathelicidins against a broad array of multidrug resistant bacteria was determined. All three peptides showed high antibacterial activity independent of the presence of MDR characteristics. Induction experiments using S. aureus and K. pneumoniae showed that although an increase in resistance was initially observed, susceptibility towards chicken cathelicidins remained high and no major resistance was developed. The combined results underline the potential of chicken cathelicidins as a new alternative to antibiotics.

Figure 1. Antibacterial activity of CATH-1-3 against E. coli 38.34.

E. coli (1×10⁶ CFU/ml) were incubated with CATH-1-3 for 3 h. Surviving bacteria were determined using colony count assays. All experiments were performed at least in triplicate. A: CATH-1; B: CATH-2; C: CATH-3.

Figure 2. Induction of CATH-1, -2, and -3 resistance in S. aureus S0385 (panel A), K. pneumoniae NCTC-13443 (panel B) and K. pneumoniae 03C006 (panel C).

Bacteria were grown o/n in the presence of 0–80 µM peptide. The sample containing the highest CATH concentration showing >80% bacterial growth compared to a control without CATH is shown. Subsequently, this bacterial culture was subcultured into new medium containing 0–80 µM CATH peptide. This procedure was repeated for 9 consecutive days. Circles: CATH-1; squares: CATH-2; triangles: CATH-3. Shown is the peptide tolerance (80% growth) over 10 days in a single induction experiment.