Boar Semen Contamination: Identification of Gram-Negative Bacteria and Antimicrobial Resistance Profile

Abstract

Bacterial contamination of boar semen occurs with some frequency in artificial insemination centers and may have a negative effect on the quality of the semen as well as on the sows’ reproductive capacity. Normally, the source of bacterial contamination in pig seminal doses is the own boar. However, distilled water or laboratory equipment used to elaborate the seminal doses can be an important source of bacterial contamination. This study focused on the identification of gram-negative bacteria in boar semen, and impact on the quality of ejaculates obtained from boar, as well as on the establishment of antimicrobial resistance patterns of isolated gram-negative bacteria. Semen samples were collected from 96 boars, ranging in age from 12–36 month, from three artificial insemination centers from the North-West of Romania. Bacterial species were identified by two methods: matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry and API 20 E (BioMerieux, France). The main bacteria isolated from the doses diluted semen were gram-negative bacteria (47.91%), with a majority of the contaminant bacteria belonging to the family Enterobacteriaceae: Seratia marcescens 19.56%, Proteus mirabilis 15.21% and Escherichia coli 10.86% and to the family Pseudomonaceae: Ralstonia picketii 17.39%, Burkholderia cepacia 10.86%, Pseudomonas aeruginosa 8.69%, and Pseudomonas fluorescens 4.34%, respectively. More than half of these isolates (56.52%) were resistant to gentamycin and 58.69% were resistant to penicillin. These antibiotics are very frequently added in sperm diluent in the centers for the processing of sperm from boars in Romania. Regular monitoring for bacterial contamination is an important aspect of a control program.

Candida Genus Maximum Incidence in Boar Semen Even after Preservation, Is It Not a Risk for AI though?

“…From the point of view of the typification of the microbial genera and species, our study revealed the same genera and species as in other authors and that the frequency of their identification varies from one author to another [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 11 , 37 ].…”

“…Some similar publications reported higher frequencies in bacterial identification, such as that of Costinar Luminita et al (2022), instead of other research, such as Martin et al (2010), who reported results more similar to ours [ 37 , 49 ].…”

“…After qualitative microbiological examinations, it was reconfirmed that boar semen had a variable degree of bacterial and fungal contamination. Numerous studies have highlighted the bacterial contamination [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 9 , 37 ] of boar semen and its negative effects, both in terms of the number of germs (LogCFU) and their typing [ 11 , 13 , 20 ]. In general, when talking about the contamination of boar semen and its quality in preservation, attention is directed toward the bacterial one.…”

“…Researchers that have induced the pig industry development revealed that sperm collection in pigs is not and should not be a sterile procedure, but to ensure that the microbiological biosecurity of AI and the continuous optimization of technologies are needed. Techniques (hygiene) and methods (extenders) that reduce or annihilate the harmful effect are currently used in pig breeding centers [ 1 , 5 , 7 , 28 , 37 ].…”

“…At present, many details are known regarding the microbiota of boar semen [ 42 , 48 , 49 ], with implication effects and measures, but they are considered without too much influence by fungal contamination. A load of sperm with fungi can influence the reproduction processes in the pig industry and deserves attention in discovering new knowledge in this field [ 1 , 4 , 5 , 6 , 7 , 12 , 15 , 28 , 34 , 37 ].…”