Phage Conversion for beta-Lactam Antibiotic Resistance of Staphylococcus aureus from Foods

Abstract

Temperate phages have been suggested to carry virulence factors and other lysogenic conversion genes that play important roles in pathogenicity. In this study, phage TEM123 in wild-type Staphylococcus aureus from food sources was analyzed with respect to its morphology, genome sequence, and antibiotic resistance conversion ability. Phage TEM123 from a mitomycin C-induced lysate of S. aureus was isolated from foods. Morphological analysis under a transmission electron microscope revealed that it belonged to the family Siphoviridae. The genome of phage TEM123 consisted of a double-stranded DNA of 43,786 bp with a G+C content of 34.06%. A bioinformatics analysis of the phage genome identified 43 putative open reading frames (ORFs). ORF1 encoded a protein that was nearly identical to the metallo-beta-lactamase enzymes that degrade beta-lactam antibiotics. After transduction to S. aureus with phage TEM123, the metallo-beta-lactamase gene was confirmed in the transductant by PCR and sequencing analyses. In a beta-lactam antibiotic susceptibility test, the transductant was more highly resistant to beta-lactam antibiotics than S. aureus S133. Phage TEM123 might play a role in the transfer of beta-lactam antibiotic resistance determinants in S. aureus. Therefore, we suggest that the prophage of S. aureus with its exotoxin is a risk factor for food safety in the food chain through lateral gene transfer.