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Purpose <p>To evaluate the efficacy of the EUCAST Rapid Antimicrobial Susceptibility Testing (RAST) on <i>Klebsiella pneumoniae</i> carrying various carbapenemases, with a focus on KPC variants.</p> Methods <p>A total of 130 carbapenemase-producing <i>K</i>. <i>pneumoniae</i> (CPKP), encompassing those harboring class A (KPC-2: <i>n</i> = 38; KPC variants: <i>n</i> = 30), class B (<i>n</i> = 42), class D (<i>n</i> = 4) and strains co-producing class A and class B carbapenemases (<i>n</i> = 16), were evaluated for susceptibility to seven antibiotics, including ceftazidime/avibactam (CAZ/AVI), using the EUCAST RAST. Results obtained after 6&#xa0;h and 8&#xa0;h of incubation were compared with those obtained by reference broth microdilution. Additionally, the capacity of the RAST method to screen for different types of carbapenemases was assessed.</p> Results <p>All 130 CPKP isolates generated 100% readable zones at both 6&#xa0;h and 8&#xa0;h, with overall categorical agreement (CA) rates of &gt; 90% for all tested antibiotics. For isolates producing class A carbapenemases, particularly the KPC variants, the EUCAST RAST showed excellent performance in determining CAZ/AVI susceptibility, achieving 100% CA and no errors at each reading time. However, significant challenges arose for meropenem (MEM), characterized by low CA (73.9%) and high major errors (MEs, 20.1%) at 6&#xa0;h reading. Extending incubation to 8&#xa0;h dramatically improved the performance, while the proportion of strains within the ATU remained high (23.3% at 6&#xa0;h; 30.0% at 8&#xa0;h).</p> Conclusions <p>The EUCAST RAST can be effectively implemented in routine clinical laboratories, particularly in regions like China where <i>K</i>. <i>pneumoniae</i> carrying KPC-2 is widely prevalent. However, caution should be exercised when interpreting the results of MEM for KPC variants.</p>

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Evaluation of EUCAST rapid antimicrobial susceptibility testing (RAST) for carbapenemase-producing Klebsiella pneumoniae with focus on KPC variants

  • 期刊论文

  • 发表日期：

    2025年9月29日

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  • Min Xu,
  • Yuchao Zhang,
  • Yajie Fu,
  • Qiaoling Sun,
  • Haishen Kong,
  • Yiqi Fu

摘要

Purpose

To evaluate the efficacy of the EUCAST Rapid Antimicrobial Susceptibility Testing (RAST) on Klebsiella pneumoniae carrying various carbapenemases, with a focus on KPC variants.

Methods

A total of 130 carbapenemase-producing K. pneumoniae (CPKP), encompassing those harboring class A (KPC-2: n = 38; KPC variants: n = 30), class B (n = 42), class D (n = 4) and strains co-producing class A and class B carbapenemases (n = 16), were evaluated for susceptibility to seven antibiotics, including ceftazidime/avibactam (CAZ/AVI), using the EUCAST RAST. Results obtained after 6 h and 8 h of incubation were compared with those obtained by reference broth microdilution. Additionally, the capacity of the RAST method to screen for different types of carbapenemases was assessed.

Results

All 130 CPKP isolates generated 100% readable zones at both 6 h and 8 h, with overall categorical agreement (CA) rates of > 90% for all tested antibiotics. For isolates producing class A carbapenemases, particularly the KPC variants, the EUCAST RAST showed excellent performance in determining CAZ/AVI susceptibility, achieving 100% CA and no errors at each reading time. However, significant challenges arose for meropenem (MEM), characterized by low CA (73.9%) and high major errors (MEs, 20.1%) at 6 h reading. Extending incubation to 8 h dramatically improved the performance, while the proportion of strains within the ATU remained high (23.3% at 6 h; 30.0% at 8 h).

Conclusions

The EUCAST RAST can be effectively implemented in routine clinical laboratories, particularly in regions like China where K. pneumoniae carrying KPC-2 is widely prevalent. However, caution should be exercised when interpreting the results of MEM for KPC variants.