Kocer Kaan, Klein Sabrina, Hildebrand Dagmar, Krall Johannes, Heeg Klaus, Boutin Sébastien, Nurjadi Dennis
Department of Infectious Diseases, Medical Microbiology and Hygiene, Heidelberg University Hospital, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany.
J Antimicrob Chemother. 2021 Oct 11;76(11):2795-2801. doi: 10.1093/jac/dkab267.
There is a growing interest in the rapid genotypic identification of antimicrobial resistance (AMR). In routine diagnostics, we detected multiple KPC-positive Escherichia coli (KPC-Ec) with discordant phenotypic meropenem susceptibility from a single patient's blood cultures, which prompted a more thorough investigation.
We investigated the potential clinical relevance of, and the mechanism behind, discordant phenotypic and genotypic meropenem susceptibility in KPC-Ec.
WGS was used to perform a comparative analysis of the isolates' genetic characteristics and their blaKPC-2 locus. Expression of blaKPC-2 was determined by quantitative PCR and the potency of meropenem hydrolysis was determined using a semi-quantitative carbapenem inactivation method. An in vivo infection assay using Galleria mellonella was performed to assess the potential clinical relevance of KPC expression in E. coli.
Despite the presence of blaKPC-2, three of five isolates were susceptible to meropenem (MICVITEK2 ≤ 0.25 mg/L), while two isolates were resistant (MICVITEK2 ≥ 16 mg/L). The isolates with high MICs had significantly higher blaKPC-2 expression, which corresponds to phenotypic meropenem inactivation. The genetic environment of blaKPC-2, which may impact KPC production, was identical in all isolates. In vivo infection assay with G. mellonella suggested that meropenem was effective in reducing mortality following infection with low-expressing KPC-Ec.
Our findings clearly highlight a limitation of genotypic AMR prediction for blaKPC. For the time being, genotypic AMR prediction requires additional analysis for accurate antibiotic therapy decision-making.
对抗菌药物耐药性（AMR）进行快速基因型鉴定的兴趣与日俱增。在常规诊断中，我们从一名患者的血培养物中检测到多株产KPC的大肠埃希菌（KPC-Ec），其美罗培南表型药敏结果不一致，这促使我们进行更深入的调查。
我们调查了KPC-Ec中美罗培南表型和基因型药敏结果不一致的潜在临床相关性及其背后的机制。
采用全基因组测序（WGS）对分离株的遗传特征及其blaKPC-2基因座进行比较分析。通过定量PCR测定blaKPC-2的表达，并使用半定量碳青霉烯灭活法测定美罗培南水解的效力。利用大蜡螟进行体内感染试验，以评估大肠杆菌中KPC表达的潜在临床相关性。
尽管存在blaKPC-2，但五株分离株中有三株对美罗培南敏感（VITEK2 MIC≤0.25mg/L），而两株分离株耐药（VITEK2 MIC≥16mg/L）。高MIC值的分离株具有显著更高的blaKPC-2表达，这与美罗培南的表型灭活相对应。所有分离株中blaKPC-2的遗传环境相同，这可能会影响KPC的产生。用大蜡螟进行的体内感染试验表明，美罗培南对低表达KPC-Ec感染后的死亡率有降低作用。
我们的研究结果清楚地凸显了blaKPC基因型AMR预测的局限性。目前，基因型AMR预测需要额外分析才能做出准确的抗生素治疗决策。
