Methicillin-Resistant Staphylococcus aureus Clonal Complex 398 as a Major MRSA Lineage in Dogs and Cats in Thailand

Abstract

The aim of this study was to present molecular and antimicrobial resistance characteristics of methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) clonal complex (CC) 398 isolated from diseased dogs and cats in Thailand. A total of 20 MRSA isolates of 134 <i>Staphylococcus aureus</i> isolated from canine and feline clinical samples during 2017-2020 were CC398, consisting of sequence type (ST) 398 (18 isolates), ST5926 (1 isolate), and ST6563 (1 isolate) by multilocus sequence typing. <i>spa</i> t034 and staphylococcal cassette chromosome <i>mec</i> (SCC<i>mec</i>) V were predominantly associated with ST398. Intraclonal differentiation was present by additional <i>spa</i> (t1255, t4653), non-detectable <i>spa</i>, composite SCC<i>mec</i> with a hybrid of <i>ccrA1B1</i>+<i>ccrC</i> and class A <i>mec</i> complex, and DNA fingerprints by pulsed-field gel electrophoresis. The isolates essentially carried antimicrobial resistance genes, mediating multiple resistance to β-lactams (<i>mecA</i>, <i>blaZ</i>), tetracyclines [<i>tet</i>(M)], aminoglycosides [<i>aac(6')-Ie-aph(2')-Ia</i>], and trimethoprim (<i>dfr</i>). Livestock-associated MRSA ST398 resistance genes including <i>lnu</i>(B), <i>lsa</i>(E), <i>spw</i>, <i>fexA</i>, and <i>tet</i>(L) were heterogeneously found and lost in subpopulation, with the absence or presence of additional <i>erm</i>(A), <i>erm</i>(B), and <i>ileS2</i> genes that corresponded to resistance phenotypes. As only a single CC398 was detected with the presence of intraclonal variation, CC398 seems to be the successful MRSA clone colonizing in small animals as a pet-associated MRSA in Thailand.