Clonal diversity and trend of methicillin-resistant/susceptible Staphylococcus aureus (MRSA/MSSA) from a tertiary care hospital in Myanmar: Increase in ST6-IVa/t304 and identification of notable clones ST22-PT, ST2885-ETA, and ST2990-ETE.

چکیده اصلی

OBJECTIVES: Staphylococcus aureus is one of the leading causes of nosocomial infections. This study aimed to clarify the recent trend of molecular epidemiological features of methicillin-resistant and susceptible S. aureus (MRSA/MSSA) isolates from a tertiary care hospital in Myanmar. METHODS: S. aureus clinical isolates from various specimens were genetically classified by the schemes of MLST and other genotypings. Antimicrobial resistance determinants and virulence factors were detected by uniplex/multiplex PCR, along with antimicrobial susceptibility testing by broth microdilution method. RESULTS: A total of 319 S. aureus (65 MRSA and 254 MSSA) and 7 S. argenteus isolates were collected during a 19 month-period (Sep. 2023 to Mar. 2025), with an MRSA rate of 20.4%. Panton-Valentine leukocidin (PVL) genes were detected in 30.4% of all the isolates, with almost similar rates in MRSA and MSSA. Among MRSA, ST6 (CC5) with SCCmec-IV (ST6-IV) was the most dominant (31%), followed by ST772 (CC1)-V, ST2885 (CC1)-IV, ST22 (CC22)-IV, and ST672 (CC361)-V. PVL-positive rate was highest in ST22 (75%) and ST121 (84%) among MRSA and MSSA, respectively. PVL-positive ST22 MRSA also harbored TSST-1 gene (ST22-PT clone). Characteristic virulence factors were detected in other MRSA clones; enterotoxin A (SEA) in ST6, exfoliative toxin A (ETA) in ST2885, and exfoliative toxin E (ETE) in ST2990. PVL-positive ST22 and ST772 MRSA showed multiple antimicrobial resistance harboring some resistance genes. MSSA isolates were differentiated into 33 STs, among which ST2990 (CC1) was the most common (24%), followed by ST121, ST1156 (CC12), ST6 (CC5) and ST1930 (CC96). All the S. argenteus were mecA-negative and belonged to ST2250. CONCLUSIONS: The present study revealed the recent clonal trend and change of MRSA/MSSA isolates in Myanmar, identifying some notable clones with characteristic virulence factors (ST6-SEA, ST22-PT, ST2885-ETA, and ST2990-ETE).

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