Turkey Meat as Source of CC9/CC398 Methicillin-Resistant Staphylococcus aureus in Humans?

Turkey Meat as Source of CC9/ CC398 Methicillin-Resistant Staphylococcus aureus in Humans? TO THE EDITOR—Livestock-associated methicillin-resistant Staphylococcus aure-us (MRSA) of clonal complex (CC) 398 were first reported to cause severe infections in humans in 2005 [1]. Direct animal exposure is considered the most effective means of MRSA CC398 transmission from livestock to humans. However, about 20%–38% of MRSA CC398 cases among humans cannot be epidemiologically linked to direct livestock contact, indicating other transmission pathways [2]. As recently reported in this journal by Larsen et al [3], poultry meat may serve as a vehicle for livestock-to-human transmission. Here, we present similar findings for CC9/CC398 MRSA (displaying spa type t899 and related), which shares unique characteristics with human clinical isolates in Denmark as shown by Larsen et al [3], strongly supporting the implication of poultry, especially turkey meat, as the source of CC9/CC398. Of a collection of >14 000 compromising strains, mainly of food and livestock origin, we identified 37 CC9/CC398 MRSA strains in addition to those described by Larsen et al [3]. Among these, 31 strains (all of poultry origin) were positive for sak/scn/chp (indicative genes carried by the φSa3 prophage) by DNA microarray (see [4] for details), and 8 of 31 (7 from turkey meat, 1 from broiler meat) also carried the φAvβ prophage (SAAV_2008/2009 genetic markers, respectively), as tested by a polymerase chain reaction assay [5]. The nucleotide sequence of the 4 turkey meat isolates— 12S01032, 13-ST00660, 14-ST01012, and 14-ST00667—was determined using a PacBio RSII sequencer (Pacific Biosciences). De novo assembling of the readings by HGAP3 resulted in a closed draft genome for each isolate. In general, all 4 isolates exhibit similar genome features, chromo-somal resistance genes, and virulence factors (Supplemental Material Table S1). However, distinct differences were Figure 1. Phylogenetic relationship of clonal complex (CC) 9/CC398 methicillin-resistant Staphylococcus aureus (spa types t899 and related) of our own study and selected isolates of the collection of Larsen et al [3]. Single-nucleotide polymorphism tree analysis was conducted using the services of the Center for Genomic Epidemiology. Phylogenetic clusters (A–C) were highlighted by different background colors; subdivisions represent subclusters. Isolates of human, turkey, and broiler chicken origin are indicated in red, yellow, and green, respectively. Genomes comprising the φAvβ prophage are marked by asterisks. observed in the content of mobile genetic elements (ie, plasmids, and phages). Further phylogenetic single-nucleotide poly-morphism tree analysis against selected human cases and poultry isolates of the …