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Background <p><i>Staphylococcus aureus</i> is a major human pathogen whose virulence and antimicrobial resistance are regulated by complex genetic networks, including the accessory gene regulator (<i>agr</i>) system. Although the relationship between <i>agr</i> types, virulence factors, antimicrobial resistance, and toxin gene distribution has been widely investigated, inconsistencies among reported findings highlight the need for further studies in different geographic and epidemiological settings. This study investigated the distribution of toxin genes, <i>agr</i> types and evaluated their association with antimicrobial resistance profiles in clinical <i>Staphylococcus aureus</i> isolates.</p> Methods <p>A total of 150 isolates, comprising 75 methicillin−resistant <i>Staphylococcus aureus</i> and 75 methicillin susceptible <i>Staphylococcus aureus</i> isolates, were collected from clinical specimens at Kocaeli University Hospital, Türkiye. Identification was performed using MALDI TOF-MS. Antimicrobial susceptibility testing was conducted by broth microdilution, and cefoxitin resistance was determined by disk diffusion. The <i>agr</i> groups (I–IV), toxin genes (<i>sea</i>, <i>seb</i>, <i>sec</i>, <i>sed</i>, <i>see</i>, <i>eta</i>, <i>etb</i>, <i>tst</i>, and <i>pvl</i>), <i>mecA</i>, and <i>femA</i> were detected by polymerase chain reaction.</p> Results <p><i>Agr</i> group I was the most prevalent, followed by groups III and II. Isolates with higher toxin gene scores (≥ 2) were more frequently associated with <i>agr</i> group III, whereas lower scores (&lt; 2) predominated in <i>agr</i> group I. MRSA isolates and resistance to tetracycline and erythromycin were more common in <i>agr</i> group III. Additionally, isolates harboring <i>eta</i>, <i>tst</i>, and <i>pvl</i> showed higher trimethoprim–sulfamethoxazole resistance rates.</p> Conclusions <p>These findings demonstrate significant associations between <i>agr</i> types, toxin gene profiles, and antimicrobial resistance patterns, suggesting that <i>agr</i> typing may offer insight into the pathogenic and epidemiological characteristics of clinical <i>Staphylococcus aureus</i> isolates.</p>

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Relationship between agr types, toxin genes, and antibiotic resistance in clinical Staphylococcus aureus isolates

  • 期刊论文

  • 发表日期：

    2026年4月24日

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  • Yilmaz Pulcu,
  • Doganhan Kadir Er,
  • Devrim Dundar

摘要

Background

Staphylococcus aureus is a major human pathogen whose virulence and antimicrobial resistance are regulated by complex genetic networks, including the accessory gene regulator (agr) system. Although the relationship between agr types, virulence factors, antimicrobial resistance, and toxin gene distribution has been widely investigated, inconsistencies among reported findings highlight the need for further studies in different geographic and epidemiological settings. This study investigated the distribution of toxin genes, agr types and evaluated their association with antimicrobial resistance profiles in clinical Staphylococcus aureus isolates.

Methods

A total of 150 isolates, comprising 75 methicillin−resistant Staphylococcus aureus and 75 methicillin susceptible Staphylococcus aureus isolates, were collected from clinical specimens at Kocaeli University Hospital, Türkiye. Identification was performed using MALDI TOF-MS. Antimicrobial susceptibility testing was conducted by broth microdilution, and cefoxitin resistance was determined by disk diffusion. The agr groups (I–IV), toxin genes (sea, seb, sec, sed, see, eta, etb, tst, and pvl), mecA, and femA were detected by polymerase chain reaction.

Results

Agr group I was the most prevalent, followed by groups III and II. Isolates with higher toxin gene scores (≥ 2) were more frequently associated with agr group III, whereas lower scores (< 2) predominated in agr group I. MRSA isolates and resistance to tetracycline and erythromycin were more common in agr group III. Additionally, isolates harboring eta, tst, and pvl showed higher trimethoprim–sulfamethoxazole resistance rates.

Conclusions

These findings demonstrate significant associations between agr types, toxin gene profiles, and antimicrobial resistance patterns, suggesting that agr typing may offer insight into the pathogenic and epidemiological characteristics of clinical Staphylococcus aureus isolates.