Abstract
Several studies have been conducted to check the prevalence of methicillin-resistant strains of Staphylococcus aureus (MRSA) in animals and animal-derived food products but limited data are available regarding their virulence and associated gene expression profile. In the present study, antibiotic resistance and virulence of MRSA and methicillin-sensitive S. aureus animal isolates were determined in vitro by agar dilution, biofilm formation, adhesion, invasion and intracellular survivability assays. In addition, the pathogenicity of these isolates was examined in a murine model of S. aureus sepsis. MRSA1679a, a strain isolated from chicken, was observed to be highly virulent, in cell culture and in mouse model, and exhibited extensive resistant profile. Comparative gene expression profile of MRSA1679a and the reference human MRSA strain (ATCC 29213) was performed using Illumina-based transcriptome and RT-qPCR analyses. Several virulence elements including 22 toxin genes were detected in MRSA animal-isolate. In addition, we observed enhanced expression of crucial virulence regulators, such as sarA and KdpDE in MRSA animal-isolate compared to the human isolate. Collectively, gene expression profile including several virulence and drug-resistance factors confirmed the unique and highly virulent determinants of the MRSA strain of poultry origin which warrants further attention due to significant threat to public health.
Highlights
Methicillin-resistant Staphylococcus aureus (MRSA) is a multidrug-resistant and pathogenic bacteria causing severe community acquired and healthcare associated infections in human[1]
Gene expression and regulation of virulence elements in human isolates of S. aureus is generally governed by global virulence regulators including a staphylococcal accessory regulator, an accessory gene regulating system[7], and two component system (KdpDE)[8]
Two methicillin-resistant strains of Staphylococcus aureus (MRSA) strains (478 and 1679a isolated from pig and chicken, respectively) and two methicillin-susceptible Staphylococcus aureus (MSSA) strains (586 and 1161a both isolated from pig) isolates were selected for this study (Supplementary Table S1)
Summary
Methicillin-resistant Staphylococcus aureus (MRSA) is a multidrug-resistant and pathogenic bacteria causing severe community acquired and healthcare associated infections in human[1]. Current epidemiological studies have revealed that MRSA strains have increased in virulence posing a serious risk to public health[3]. These multidrug resistant strains have been recently detected in animal husbandry as well as in animal-derived food products raising issues of the possible zoonotic transmission[4]. While genome sequencing of MRSA isolates from animals has been identified, the gene expression profile and contribution to virulence remain unknown. Little is known about the gene expression and regulation of these virulence elements in animal associated MRSA. Results garnered from this study confirm the unique virulent regulators and global gene expression profile of MRSA strain of poultry origin
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