Abstract
In this study, we aimed to investigate the molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus pseudintermedius (MRSP) clinical and colonizing isolates of dogs and cats to profile contributing factors associated with their isolation. Nasal and rectal samples were collected from dogs and cats between 2015 and 2017 to identify colonizing isolates. Clinical isolates collected between 2003 and 2016 were retrieved from a Queensland university veterinary diagnostic laboratory. All isolates were identified using standard microbiological and molecular methods and were characterized by whole genome sequencing. Phylogenetic relationships and differences in epidemiological factors were investigated. Seventy-two MRSP isolates out of 1,460 colonizing samples and nine MRSP clinical isolates were identified. No MRSA was isolated. ST496 and ST749 were the most commonly isolated sequence types with different SCCmec types. ST496 clones spread both along the coast and more inland where ST749 was more centered in Brisbane. The resistance and virulence factors differed significantly between the two sequence types. ST496 colonizing and clinical isolates were similarly multidrug resistant. The virulence genes of ST749 colonizing and clinical isolates were similar as both contained the gene nanB for sialidase. There were no differences in the individual and clinical factors between predominant sequence types. High levels of antimicrobial resistance occurred in the majority of isolates, which is of potential concern to human and veterinary health. The phylogenetic clustering of isolates from this study and others previously identified in countries, particularly New Zealand, with which Australia has high volume of pet movements could suggest the importation of clones, which needs further investigation.
Highlights
Methicillin-resistant Staphylococcus pseudintermedius (MRSP) and methicillin-resistant Staphylococcus aureus (MRSA) are concerning zoonotic opportunistic pathogens in veterinary medicine and public health
Sixteen of the isolates were from 11/255 dogs (4%) sampled at clinic A; 24 isolates were from 14/102 dogs (14%) from clinic B, and 11 isolates were from 9/30 dogs (30%) sampled at clinic C were positive for MRSP
Our study demonstrates that a sample population of healthy pets from South East Queensland (SE QLD) is primarily carriers of ST496 and ST749 MRSP clones, and these sequence types (STs) differ significantly in their resistance and virulence patterns
Summary
Methicillin-resistant Staphylococcus pseudintermedius (MRSP) and methicillin-resistant Staphylococcus aureus (MRSA) are concerning zoonotic opportunistic pathogens in veterinary medicine and public health. MRSP is predominately found in dogs but has been isolated from cats and humans [1, 2]. MRSA is a major human pathogen but has been identified in companion animals [3]. Methicillin-resistant staphylococci (MRSs) are often multidrug resistant, which can result in infections challenging to treat. The mecA gene is responsible for methicillin resistance and confers reduced affinity for β-lactam antimicrobials. The gene is carried on the staphylococcal chromosomal cassette mec (SCCmec) that provides potential for transfer of resistance to other non–βlactam antimicrobials genes between susceptible and resistant strains [4]. The combination of multidrug resistance, zoonotic capabilities, and nosocomial transmission contributes to the public health concern surrounding these bacteria
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