Abstract
Staphylococcus argenteus, a novel staphylococcal species independent of S. aureus, causes a wide spectrum of infectious diseases. As detection of this species from humans and animals has been increasingly reported worldwide, its growing virulence and drug resistance via external genetic determinants has become concerning. In this study, the prevalence and genetic characteristics of virulence factors and drug resistance determinants were investigated for 82 S. argenteus clinical isolates in Hokkaido, Japan, for a one-year period starting in August 2019. These S. argenteus isolates corresponded to 0.66% of the total number of S. aureus isolates collected in the same period. The most prevalent genotype was sequence type (ST) 2250 and staphylocoagulase (coa) genotype XId (45.1%, n = 37), followed by ST1223-coa XV (30.5%, n = 25) and ST2198-coa XIV (24.4%, n = 20). Panton-Valentine leukocidin genes (lukS-PV-lukF-PV) were identified in a single ST2250 isolate. Only ST1223 isolates had the enterotoxin gene cluster (egc-2), seb, and selw (detection rate; 100%, 60%, and 84%, respectively), while sec, sey, sel26-sel27, tst-1 were only detected in ST2250 isolates (detection rate; 10.8%, 100%, 67.6%, and 10.8%, respectively). ST2198 isolates harbored selx at a significantly higher rate (60%) than isolates of other STs. Although most of S. argenteus isolates were susceptible to antimicrobials examined, ST2198 showed higher resistance rates to penicillin, macrolides, and aminoglycosides than other STs, and it harbored various resistance genes such as blaZ, erm(C), msr(A), lnuA, and aac(6′)-Ie-aph(2″)-Ia. Only one ST2250 isolate possessed SCCmec-IVc, showing resistance to oxacillin. blaZ was the most prevalent determinant of resistance in the three STs and belonged to two plasmid groups and a chromosomal group, suggesting its diverse origin. lnu(A) in ST2198 isolates was assigned to a major cluster with various staphylococcal species. The present study indicates that the prevalence of virulence factors and drug resistance profile/determinants differ depending on the lineage (ST) of S. argenteus.
Highlights
Staphylococcus argenteus is a novel coagulase-positive Staphylococcus species that is genetically closely related to Staphylococcus aureus and classified within the S. aureus complex (SAC) together with S. aureus, and S. schweitzeri [1]
In a one-year period, we identified a total of eighty-two S. argenteus isolates from 82 patients, comprising 81 methicillin-susceptible and one single methicillin-resistant isolate
The prevalence and genetic characteristics of S. argenteus clinical isolates were investigated for a one-year period in northern Japan
Summary
Staphylococcus argenteus is a novel coagulase-positive Staphylococcus species that is genetically closely related to Staphylococcus aureus and classified within the S. aureus complex (SAC) together with S. aureus, and S. schweitzeri [1]. S. aureus and S. argenteus are widely distributed in human and animals, while S. schweitzeri has been identified mostly in animals in Africa [2,3]. Divergent S. aureus of sequence type 75 (ST75) was first described in 2002 [5], and was later assigned to S. argenteus belonging to clonal complex 75 (CC75) for clinical isolates found in the Northern Territory of Australia during a period from 2004 to 2005 [6]. ST2250 is considered to be the dominant clone with widespread geographical distribution including Europe [8,9,10,11,12], Southeast Asia [13,14,15,16], China [17], and Japan [18,19,20], while ST1223, the lineage related to CC75, is less prevalent and has been described as the pathogen responsible for outbreaks of food poisoning in Japan [21,22] as well as colonizing isolates in Cambodia and the Amazonian forest [23,24]
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