Horizontal Gene Transfers Link a Human MRSA Pathogen to Contagious Bovine Mastitis Bacteria

Thomas Brody,Yong Lin,Yang Fann,Jermaine Ross,Alexander Kuzin,Mukta Kundu,Amarendra S Yavatkar,Ward F Odenwald,Michael Hofreiter

doi:10.1371/journal.pone.0003074

Abstract

BackgroundAcquisition of virulence factors and antibiotic resistance by many clinically important bacteria can be traced to horizontal gene transfer (HGT) between related or evolutionarily distant microflora. Comparative genomic analysis has become an important tool for identifying HGT DNA in emerging pathogens. We have adapted the multi-genome alignment tool EvoPrinter to facilitate discovery of HGT DNA sequences within bacterial genomes and within their mobile genetic elements.Principal Findings EvoPrinter analysis of 13 different Staphylococcus aureus genomes revealed that one of the human isolates, the hospital epidemic methicillin-resistant MRSA252 strain, uniquely shares multiple putative HGT DNA sequences with different causative agents of bovine mastitis that are not found in the other human S. aureus isolates. MRSA252 shares over 14 different DNA sequence blocks with the bovine mastitis ET3 S. aureus strain RF122, and many of the HGT DNAs encode virulence factors. EvoPrinter analysis of the MRSA252 chromosome also uncovered virulence-factor encoding HGT events with the genome of Listeria monocytogenes and a Staphylococcus saprophyticus associated plasmid. Both bacteria are also causal agents of contagious bovine mastitis.Conclusions EvoPrinter analysis reveals that the human MRSA252 strain uniquely shares multiple DNA sequence blocks with different causative agents of bovine mastitis, suggesting that HGT events may be occurring between these pathogens. These findings have important implications with regard to animal husbandry practices that inadvertently enhance the contact of human and livestock bacterial pathogens.

Highlights

Staphylococcus aureus (S. aureus) infections in both man and domestic livestock present growing and formidable global challenges for human and animal health concerns
EvoPrinter analysis reveals that the human MRSA252 strain uniquely shares multiple DNA sequence blocks with different causative agents of bovine mastitis, suggesting that horizontal gene transfer (HGT) events may be occurring between these pathogens
Our search for HGT DNA sequences within the genomes of different human Methicillinresistant S. aureus (MRSA) isolates has led to the discovery that one of the human strains, the hospital-acquired epidemic MRSA252 [23], uniquely shares multiple DNA sequence blocks with three different causative agents of contagious bovine mastitis but not with other human isolates

Summary

Conclusions

EvoPrinter analysis reveals that the human MRSA252 strain uniquely shares multiple DNA sequence blocks with different causative agents of bovine mastitis, suggesting that HGT events may be occurring between these pathogens. These findings have important implications with regard to animal husbandry practices that inadvertently enhance the contact of human and livestock bacterial pathogens

Introduction

Results and Discussion

Materials and Methods