Molecular Analysis of Human and Canine Staphylococcus aureus Strains Reveals Distinct Extended-Host-Spectrum Genotypes Independent of Their Methicillin Resistance

Abstract

Staphylococcus aureus causes a wide range of infectious diseases in humans and various animal species. Although presumptive host-specific factors have been reported, certain genetic lineages seem to lack specific host tropism, infecting a broad range of hosts. Such Extended-Host-Spectrum Genotypes (EHSGs) have been described in canine infections, caused by common regional human methicillin-resistant S. aureus (MRSA) lineages. However, information is scarce about the occurrence of methicillinsusceptible S. aureus (MSSA) EHSGs. To gain deeper insight into EHSG MSSA and EHSG MRSA of human and canine origin, a comparative molecular study was carried out, including a convenience sample of 120 current S. aureus (70 MRSA and 50 MSSA) isolates obtained from infected dogs. spa typing revealed 48 different spa types belonging to 16 different multilocus sequence typing clonal complexes (MLST-CCs). Based on these results, we further compared a subset of canine (n ‫؍‬ 48) and human (n ‫؍‬ 14) strains, including isolates of clonal complexes CC5, CC22, CC8, CC398, CC15, CC45, and CC30 by macrorestriction (pulsedfield gel electrophoresis [PFGE]) and DNA-microarray analysis. None of the methods employed was able to differentiate between clusters of human and canine strains independently of their methicillin resistance. In contrast, DNA-microarray analysis revealed 79% of the 48 canine isolates as carriers of the bacteriophage-encoded human-specific immune evasion cluster (IEC). In conclusion, the high degree of similarity between human and canine S. aureus strains regardless of whether they are MRSA or MSSA envisions the existence of common genetic traits that enable these strains as EHSGs, challenging the concept of resistancedriven spillover of MRSA.

Capturing the cloud of diversity reveals complexity and heterogeneity of MRSA carriage, infection and transmission

“…Previously, we have shown a shared population of CC22 MRSA circulates in humans, cats and dogs 39 . Here, we demonstrate direct transmission occurring in both directions, substantiating the view that ST22 has a broad host range and behaves as a nosocomial pathogen within a veterinary health-care setting just as it does within human hospitals 39 40 .…”

Molecular Epidemiology of Methicillin-Susceptible and Methicillin-Resistant Staphylococcus aureus in Wild, Captive and Laboratory Rats: Effect of Habitat on the Nasal S. aureus Population

“…These host adaptation processes frequently restrict the host range that can be successfully colonized and infected by a certain S. aureus lineage. In consequence, certain CCs seem to have a restricted host spectrum, like ST5 in poultry or ST433 in pigs [35,36], while others, like CC8, CC22 and CC398, display an extended host spectrum and are therefore called Extended-Host-Spectrum Genotypes (EHSGs) [24,37,38].…”

Distribution of toxin genes among different spa types and phage types of animal Staphylococcus aureus

“…This complex was considered a typical human-associated lineage thus far (Sung et al 2008 ). As recent studies proved that it can be presented among both human and canine isolates, a transmission of strains from humans to dogs was likely to occur (Vincze et al 2013 ). The same refers to another type isolated in our study, t723, which was originally identified as a human-associated strain from a subtropical recreational marine beach (Plano et al 2013 ).…”

“…The diversity of the spa gene, consisting mainly of a number of repeats of 24 bp in length, is attributed to point mutations, as well as to deletions and duplications of the repeats. The spa typing allows us to characterize and compare strains isolated from various hosts for their phylogenetic relatedness (Ebner et al 2013 ; Espinosa-Gongora et al 2012 ; Vincze et al 2013 ). S. aureus is known to synthesize an array of virulence factors, such as leukocidins, exfoliative toxins and pyrogenic toxins superantigens (PTSAgs).…”