Asempa Tomefa E, Bajor Hannah, Mullins Jessica H, Hartnett Janice, Nicolau David P
Center for Anti-Infective Research and Development, Hartford Hospitalgrid.277313.3, Hartford, Connecticut, USA.
Women's Ambulatory Health Services, Hartford Hospitalgrid.277313.3, Hartford, Connecticut, USA.
Microbiol Spectr. 2021 Nov 24;9(3):e0167021. doi: 10.1128/Spectrum.01670-21.
Research in identifying alternative growth media that better mimic host conditions is gaining ground. Relative to nutrient-rich Mueller-Hinton broth (MHB), data on the influence of physiologic or host-mimicking media on metallo-β-lactamase (MBL) resistance are lacking. The objective was to evaluate meropenem susceptibility against clinical and engineered MBL-harboring strains in a physiologic medium (urine). Antimicrobial susceptibility testing (AST) by broth microdilution was conducted with a wild-type Klebsiella pneumoniae strain and two engineered isogenic variants harboring K. pneumoniae carbapenemase 2 (KPC-2) or New Delhi MBL 1 (NDM-1), as well as two clinical K. pneumoniae isolates (harboring NDM-1 and VIM-1). MICs were determined in conventional cation-adjusted MHB (caMHB) and sterile-filtered urine samples (18 patients). All KPC- and MBL-harboring isolates were meropenem resistant (MICs of ≥16 mg/liter) in caMHB. AST of the KPC isolate in urine resulted in 50% (9/18 urine samples) essential agreement (i.e., within ±1 dilution, relative to the caMHB MIC), highlighting challenges with the use of urine as a medium capable of supporting AST. In the 9 AST-viable urine samples, meropenem MICs were 2- to 9-fold lower than that in caMHB (MIC of 32 mg/liter) among MBL-harboring isolates. Zinc concentrations determined by inductively coupled plasma mass spectrometry averaged 1.25 mg/liter and ranged from 0.12 to 1.14 mg/liter in caMHB and 18 urine samples, respectively. The full extent of MBL-mediated resistance among K. pneumoniae isolates appears to be attenuated in urine. Factors influencing free bioactive zinc levels warrant further investigation. Studies assessing antibiotic susceptibility profiles in nonconventional media are lacking. MBL-mediated resistance has come under scrutiny due to the dependence on extracellular zinc concentrations, which makes the choice of testing medium influential for β-lactam MICs. This study explores human urine as a physiologically relevant matrix with which susceptibility profiles of MBL-harboring isolates can be assessed, relative to conventional broth.
寻找能更好模拟宿主环境的替代生长培养基的研究正在取得进展。相对于营养丰富的穆勒-欣顿肉汤（MHB），关于生理或模拟宿主培养基对金属β-内酰胺酶（MBL）耐药性影响的数据尚缺。目的是评估美罗培南对生理培养基（尿液）中临床和工程化携带MBL菌株的敏感性。采用肉汤微量稀释法对一株野生型肺炎克雷伯菌菌株以及两株携带肺炎克雷伯菌碳青霉烯酶2（KPC-2）或新德里金属β-内酰胺酶1（NDM-1）的工程化同基因变体，还有两株临床肺炎克雷伯菌分离株（携带NDM-1和VIM-1）进行了抗菌药物敏感性试验（AST）。在传统阳离子调整MHB（caMHB）和无菌过滤尿液样本（18例患者）中测定了最低抑菌浓度（MIC）。所有携带KPC和MBL的分离株在caMHB中对美罗培南耐药（MIC≥16mg/L）。对尿液中的KPC分离株进行AST，结果显示50%（9/18个尿液样本）基本一致（即相对于caMHB的MIC，在±1个稀释度范围内），这凸显了将尿液用作能够支持AST的培养基所面临的挑战。在9个可进行AST的尿液样本中，携带MBL的分离株中美罗培南的MIC比在caMHB中低2至9倍（caMHB中的MIC为32mg/L）。通过电感耦合等离子体质谱法测定的锌浓度在caMHB和18个尿液样本中平均分别为1.25mg/L和0.12至1.14mg/L。肺炎克雷伯菌分离株中MBL介导的耐药性在尿液中的全部程度似乎有所减弱。影响游离生物活性锌水平的因素值得进一步研究。缺乏评估非传统培养基中抗生素敏感性谱的研究。由于对细胞外锌浓度的依赖性，MBL介导的耐药性受到了审查，这使得测试培养基的选择对β-内酰胺类MIC有影响。本研究探讨了人尿液作为一种生理相关基质，相对于传统肉汤，可用于评估携带MBL分离株的敏感性谱。
