Transduction of the Streptococcus pyogenes bacteriophage Φm46.1, carrying resistance genes mef(A) and tet(O), to other Streptococcus species

Abstract

Φm46.1 – Streptococcus pyogenes bacteriophage carrying mef(A) and tet(O), respectively, encoding resistance to macrolides (M phenotype) and tetracycline – is widespread in S. pyogenes but has not been reported outside this species. Φm46.1 is transferable in vitro among S. pyogenes isolates, but no information is available about its transferability to other Streptococcus species. We thus investigated Φm46.1 for its ability to be transduced in vitro to recipients of different Streptococcus species. Transductants were obtained from recipients of Streptococcus agalactiae, Streptococcus gordonii, and Streptococcus suis. Retransfer was always achieved, and from S. suis to S. pyogenes occurred at a much greater frequency than in the opposite direction. In transductants Φm46.1 retained its functional properties, such as inducibility with mitomycin C, presence both as a prophage and as a free circular form, and transferability. The transductants shared the same Φm46.1 chromosomal integration site as the donor, at the 3′ end of a conserved RNA uracil methyltransferase (rum) gene, which is an integration hotspot for a variety of genetic elements. No transfer occurred to recipients of Streptococcus pneumoniae, Streptococcus oralis, and Streptococcus salivarius, even though rum-like genes were also detected in the sequenced genomes of these species. A largely overlapping 18-bp critical sequence, where the site-specific recombination process presumably takes place, was identified in the rum genes of all recipients, including those of the species yielding no transductants. Growth assays to evaluate the fitness cost of Φm46.1 acquisition disclosed a negligible impact on S. pyogenes, S. agalactiae, and S. gordonii transductants and a noticeable fitness advantage in S. suis. The S. suis transductant also displayed marked overexpression of the autolysin-encoding gene atl.

Phages rarely encode antibiotic resistance genes: a cautionary tale for virome analyses

“…In particular, three well-studied ARGs carrying prophages in Streptococcus pyogenes have not been shown yet to be capable of phage lytic activity (Banks et al, 2003;Brenciani et al, 2010;Iannelli et al, 2014). The three elements carry over the antibiotic resistance phenotype across Streptococcal species when cells are put into contact, using a conjugation protocol (Santagati et al, 2003;Giovanetti et al, 2014). Whether these ARG-carrying prophages that may not be lytically active represent an important category of mobile elements in terms of ARG spreading remains an open question.…”

Phages rarely encode antibiotic resistance genes: a cautionary tale for virome analyses

“…In particular, three well-studied ARG carrying prophages in Streptococcus pyogenes have not been shown yet to be capable of phage lytic activity (Banks et al 2003, Brenciani et al 2010, Iannelli et al 2014. The three elements carry over the antibiotic resistance phenotype across Streptococcal species when cells are put into contact, using a conjugation protocol (Giovanetti et al 2014, Santagati et al 2003. Whether these ARG-carrying prophages that may not be lytically active represent an important category of mobile elements in terms of ARG spreading, remains an open question.…”

Characterization and spontaneous induction of urinary tract Streptococcus anginosus prophages

“…In a previous study, Φm46.1 was found to be capable of being transduced in vitro to strains of S. agalactiae, S. gordonii and S. suis [28]. This suggests that the group 3 phages may have a broad host range.…”