Ceftiofur treatment of sows results in long‑term alterations in the nasal microbiota of the ofspring that can be ameliorated by inoculation of nasal colonizers

Abstract

Background The nasal microbiota of the piglet is a reservoir for opportunistic pathogens that can cause polyse‑ rositis, such as Glaesserella parasuis, Mycoplasma hyorhinis or Streptococcus suis. Antibiotic treatment is a strategy to control these diseases, but it has a detrimental efect on the microbiota. We followed the piglets of 60 sows from birth to 8 weeks of age, to study the efect of ceftiofur on the nasal microbiota and the colonization by patho‑ gens when the treatment was administered to sows or their litters. We also aimed to revert the efect of the antibiotic on the nasal microbiota by the inoculation at birth of nasal colonizers selected from healthy piglets. Nasal swabs were collected at birth, and at 7, 15, 21 and 49 days of age, and were used for pathogen detection by PCR and bacterial culture, 16S rRNA amplicon sequencing and whole shotgun metagenomics. Weights, clinical signs and production parameters were also recorded during the study. Results The composition of the nasal microbiota of piglets changed over time, with a clear increment of Clostridiales at the end of nursery. The administration of ceftiofur induced an unexpected temporary increase in alpha diversity at day 7 mainly due to colonization by environmental taxa. Ceftiofur had a longer impact on the nasal microbiota of piglets when administered to their sows before farrowing than directly to them. This efect was partially reverted by the inoculation of nasal colonizers to newborn piglets and was accompanied by a reduction in the number of animals showing clinical signs (mainly lameness). Both interventions altered the colonization pattern of diferent strains of the above pathogens. In addition, the prevalence of resistance genes increased over time in all the groups but was signifcantly higher at weaning when the antibiotic was administered to the sows. Also, ceftiofur treatment induced the selection of more beta‑lactams resistance genes when it was administered directly to the piglets. Conclusions This study shed light on the efect of the ceftiofur treatment on the piglet nasal microbiota over time and demonstrated for the frst time the possibility of modifying the piglets’ nasal microbiota by inoculating natural colonizers of the upper respiratory tract.