Staphylococcus aureus CC398 clade associated with human-to-human transmission

Abstract

Staphylococcus aureus clonal complex 398 (CC398) isolates colonize livestock and can spread to human contacts. Genetic analysis of isolates epidemiologically associated with human-to-human, but not livestock, transmission in multiple countries and continents identified a common clade that was negative for tet(M) and positive for bacteriophage 3. Another group of human-to-human-transmitted isolates belonged to the common livestock-associated clade but had acquired a unique 7 bacteriophage.

Fig 1

Microarray clustering analysis of CC398 isolates based on 11,715 60-mer oligonucleotides representing MGE genes. The clustering on the left shows the evolutionary relatedness of the isolates. For each isolate, the host origin (human with pig contact = H, pig = P, and human without pig contact = HWP), country origin (Belgium = BE, Canada = CA, Denmark = DK, Dominican Republic = DO, Italy = IT, Martinique = MQ, The Netherlands = NL, and United States = US), status (colonization = C and infection = I), and year of isolation is shown. Isolates from humans without pig contact are highlighted in red, while isolates from pigs and humans with pig contact are shown in black. Multiple MGEs varied between isolates, and representative genes of those MGEs with the strongest association with a clade are shown as present (black/red boxes) or absent (white boxes) Each MGE gene was significantly associated (P < 0.05, χ² test) with either the major pig-associated CC398 clade (clade P) or the major human-specific CC398 clade (clade H). Two humans without pig contact may have had previous exposure to reservoirs of pig bacteria; they are denoted with an asterisk (HWP*).