Cationic Synthetic Peptides: Assessment of Their Antimicrobial Potency in Liquid Preserved Boar Semen

Abstract

Various semen extender formulas are in use to maintain sperm longevity and quality whilst acting against bacterial contamination in liquid sperm preservation. Aminoglycosides are commonly supplemented to aid in the control of bacteria. As bacterial resistance is increasing worldwide, antimicrobial peptides (AMPs) received lively interest as alternatives to overcome multi-drug resistant bacteria. We investigated, whether synthetic cationic AMPs might be a suitable alternative for conventional antibiotics in liquid boar sperm preservation. The antibacterial activity of two cyclic AMPs (c-WWW, c-WFW) and a helical magainin II amide analog (MK5E) was studied in vitro against two Gram-positive and eleven Gram-negative bacteria. Isolates included ATCC reference strains, multi-resistant E. coli and bacteria cultured from boar semen. Using broth microdilution, minimum inhibitory concentrations were determined for all AMPs. All AMPs revealed activity towards the majority of bacteria but not against Proteus spp. (all AMPs) and Staphylococcus aureus ATCC 29213 (MK5E). We could also demonstrate that c-WWW and c-WFW were effective against bacterial growth in liquid preserved boar semen in situ, especially when combined with a small amount of gentamicin. Our results suggest that albeit not offering a complete alternative to traditional antibiotics, the use of AMPs offers a promising solution to decrease the use of conventional antibiotics and thereby limit the selection of multi-resistant strains.

Challenges and Limits Using Antimicrobial Peptides in Boar Semen Preservation

“…A second investigation addressed the suitability of the AMPs as an alternative to conventional antibiotics in liquid boar semen preservation (Speck et al. ). The antibacterial activity of c‐WWW, c‐WFW, and MK5E was studied in vitro with two gram‐positive and eleven gram‐negative bacteria.…”

“…The results suggest that AMPs, although not a complete alternative to traditional antibiotics, represent a promising solution for decreasing the use of conventional antibiotics and thereby limiting the selection of multiresistant strains (Speck et al. ). Testing the AMPs will require the implementation of validated standardized methods for in vitro and in situ studies.…”

Bacterial Contamination of Boar Semen and its Relationship to Sperm Quality Preserved in Commercial Extender Containing Gentamicin Sulfate

“…Most microorganisms detected in boar ejaculates are considered (to some extent) nonpathogenic (Althouse et al 2000, Maes et al 2008, Morrell and Wallgren 2014, and they seem to have little effect on fecundity under natural mating conditions (Speck et al 2014), as the female reproductive tract has developed its own defense mechanisms to cope with bacteria from the semen (Dalin et al 2004, Morrell andWallgren 2011). However, when such semen is used in AI, there is a possibility that the bacteria will grow and multiply in the extended semen.…”

“…If bacterial contamination is left uncontrolled, the end result is economic loss for porcine studs (Althouse et al 2000, Althouse and Lu 2005, Baracaldo and Ward 2008, Maroto Martín et al 2010. To avoid these problems, proper hygienic procedures should be respected during the collection and laboratory processing of semen, especially given that it has recently been emphasized that the antimicrobials usually used in porcine semen to prevent the growth of contaminating bacteria are of limited effectiveness (Althouse and Lu 2005, Goldberg et al 2013, Speck et al 2014, Schulze et al 2015, Kuster and Althouse 2016.…”

ANTIMICROBIAL PEPTIDES IN SEMEN EXTENDERS: A VALUABLE REPLACEMENT OPTION FOR ANTIBIOTICS IN CRYOPRESERVATION- A Prospective Review

“…CAMPs were seen as a potential alternates to deal with the problem of antibiotic resistance development and biofilms Speck et al, 2014). In comparison to traditional antibiotics, CAMPs lower the probability of microbial resistance.…”