Molecular Characteristics of Methicillin-Resistant Staphylococci Clinical Isolates from a Tertiary Hospital in Northern Thailand

Abstract

Methicillin-resistant staphylococci are now recognized as a major cause of infectious diseases, particularly in hospitals. Molecular epidemiology is important for prevention and control of infection, but little information is available regarding staphylococcal infections in Northern Thailand. In the present study, we examined antimicrobial susceptibility patterns, detection of antimicrobial resistance genes, and SCC mec types of methicillin-resistant S. aureus (MRSA) and methicillin-resistant coagulase-negative staphylococci (MR-CoNS) isolated from patients in a hospital in Northern Thailand. The species of MRSA and MR-CoNS were identified using combination methods, including PCR, MALDI-TOF-MS, and tuf gene sequencing. The susceptibility pattern of all isolates was determined by the disk diffusion method. Antimicrobial resistance genes, SCC mec types, and ST239 were characterized using single and multiplex PCR. ST239 was predominant in MRSA isolates (10/23). All MR-CoNS (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mrow><mml:mi>N</mml:mi><mml:mo>=</mml:mo><mml:mn>31</mml:mn></mml:mrow></mml:math>) were identified as S. haemolyticus (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mrow><mml:mi>N</mml:mi><mml:mo>=</mml:mo><mml:mn>18</mml:mn></mml:mrow></mml:math>), S. epidermidis (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M3"><mml:mrow><mml:mi>N</mml:mi><mml:mo>=</mml:mo><mml:mn>3</mml:mn></mml:mrow></mml:math>), S. cohnii (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M4"><mml:mrow><mml:mi>N</mml:mi><mml:mo>=</mml:mo><mml:mn>3</mml:mn></mml:mrow></mml:math>), S. capitis (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M5"><mml:mrow><mml:mi>N</mml:mi><mml:mo>=</mml:mo><mml:mn>6</mml:mn></mml:mrow></mml:math>), and S. hominis (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M6"><mml:mrow><mml:mi>N</mml:mi><mml:mo>=</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:math>). More than 70% of MRSA and MR-CoNS were resistant to cefoxitin, penicillin, oxacillin, erythromycin, clindamycin, gentamicin, and ciprofloxacin. In MRSA isolates, the prevalence of erm A (78.3%) and erm B (73.9%) genes was high compared to that of the erm C gene (4.3%). In contrast, erm C (87.1%) and qac A/B genes (70.9%) were predominant in MR-CoNS isolates. SCC mec type III was the dominant type of MRSA (13/23), whereas SCC mec type II was more present in S. haemolyticus (10/18). Ten MRSA isolates with SCC mec type III were ST239, which is the common type of MRSA in Asia. This finding provides useful information for a preventive health strategy directed against methicillin-resistant staphylococcal infections.