Identification and characterization of Staphylococcus argenteus from Indonesia

Background

In 2015, Staphylococcus argenteus was reported for the first time as a novel species of the Staphylococcus aureus complex. While S. argenteus has been found in many countries, its presence in Indonesia has not been reported yet. Our aim is to confirm S. argenteus presence in Indonesia, describe its characteristics and analyze its genomic diversity.

Methods

The S. aureus isolates used in this study were collected from patients with skin and soft tissue infections in Indonesia, between July 2009 to February 2010. Randomly selected isolates were recultured from −80 C° stocks and analyzed using matrix-assisted laser desorption/ionization – time of flight (MALDI-TOF). Isolates identified as S. argenteus, S. roterodami, or S. schweitzeri and S. aureus with a low score in the MALDI-TOF analysis were analyzed by a real-time PCR targeting the nucA gene able to identify true S. argenteus. Isolates identified as S. argenteus were further characterized by whole genome sequencing. Vitek®2 (bioMérieux) was used for antimicrobial susceptibility testing.

Results

Fifteen isolates were identified as S. argenteus, with the majority belonging to ST2250. Two pairs of isolates proved to be identical by core genome multilocus sequence typing analysis. Most isolates were susceptible to all antibiotics tested, except for seven isolates (46.7 %) that were resistant to benzylpenicillin, and one isolate was resistant to tetracycline (6.7 %). The presence of resistance genes blaZ and tet(45) correlated with these findings. Notably, the sey enterotoxin gene was prevalent in 80 % of the isolates. Other virulence factor genes were less prevalent. Plasmid replicon types in S. argenteus were also known to S. aureus.

Conclusion

Our study reveals the occurrence of S. argenteus in Indonesia. The diversity within Indonesian S. argenteus matches the global diversity of S. argenteus. Identical isolates between patients indicate potential transmission events. A lower prevalence of a broad panel of virulence factors suggests that S. argenteus is less virulent than S. aureus.