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METHODS article
Front. Microbiol.
Sec. Antimicrobials, Resistance and Chemotherapy
Volume 16 - 2025 | doi: 10.3389/fmicb.2025.1513425
This article is part of the Research TopicNavigating Challenges and Innovations in Antimicrobial Resistance, Environmental Microbiology, and Industrial SolutionsView all 7 articles
Three Simple and Cost-Effective Assays for AAC(6')-Ib-cr Enzyme Activity
Provisionally accepted- 1Wenzhou Hospital of Traditional Chinese Medicine, Wenzhou, China
- 2Wenzhou People’s Hospital, Wenzhou, Zhejiang Province, China
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The enzyme AAC(6')-Ⅰb-cr belongs to plasmid-mediated quinolone resistance (PMQR), first reported in 2006 and now widely disseminating. Here, we developed three phenotypic methods to detect AAC(6')-Ⅰb-cr enzyme-producing Enterobacteriaceae (APE), two of which are proposed innovatively in this research. These tests are based on the following principles: (i) Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF MS) can measure the mass shift of 42 Da resulting from ciprofloxacin acetylation by the AAC(6')-Ib-cr enzyme. (ii) Co-incubation of ciprofloxacin disks with APE results in inactivation of the drug activity, making it unable to inhibit the growth of the indicator organism. We named this test the Quinolone Inactivation Method (QIM). (iii) Based on the principles of the modified Hodge test, we designed the Quinolone Hodge test (QHT). Through exploration of optimal conditions for three methods, we found that MALDI-TOF MS provides the most intuitive results after 1 hour of incubation. The interpretability of the QIM and QHT results was significantly improved when the indicator organism E. coli ATCC25922 was replaced with a quinolone-slightly-resistant isolate. However, Proteus mirabilis was excluded from both QIM and QHT due to its swarming motility. Next, a validation study was conducted using a prospectively collected set of 187 clinical strains, demonstrating 100% specificity (MSM: 141/141; QIM,QHT: 135/135) and 100% sensitivity (MSM: 46/46; QIM,QHT: 33/33) compared to the genotype. In a word, this study presented three simple, efficient, and cost-effective methods for detecting APE, suitable for clinical microbiology laboratories under various conditions for the prevention and control of hospital infections.
Keywords: AAC(6')-Ib-cr, PMQR, quinolone, antimicrobial resistance, Enterobacteriaceae
Received: 18 Oct 2024; Accepted: 03 Apr 2025.
Copyright: © 2025 Liang, Cai, Mao, Chen, Dai, Jin and Kong. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence:
Shizhou Liang, Wenzhou Hospital of Traditional Chinese Medicine, Wenzhou, China
Wanzhong Kong, Wenzhou Hospital of Traditional Chinese Medicine, Wenzhou, China
Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.