Xiangkuo Zheng, Weiliang Zeng, Yan Liu, Luozhu Feng, Jiayin Zheng, Tieli Zhou, Changrui Qian, Cui Zhou
{"title":"Clinical characteristics, specific resistance patterns, and molecular mechanisms of carbapenem-resistant <i>Morganella morganii</i> isolates.","authors":"Xiangkuo Zheng, Weiliang Zeng, Yan Liu, Luozhu Feng, Jiayin Zheng, Tieli Zhou, Changrui Qian, Cui Zhou","doi":"10.3389/fcimb.2025.1672736","DOIUrl":null,"url":null,"abstract":"<p><strong>Objectives: </strong>The emergence and spread of carbapenem-resistant <i>Morganella morganii</i> (<i>M. morganii</i>) pose a serious global challenge. This study aimed to investigate the clinical characteristics, resistance patterns, and molecular mechanisms of carbapenem-resistant <i>M. morganii</i>.</p><p><strong>Methods: </strong>A total of 170 <i>M. morganii</i> clinical isolates were collected from the First Affiliated Hospital of Wenzhou Medical University (Wenzhou, China) between January 2016 and December 2017. Carbapenem MICs were determined by antimicrobial susceptibility testing. Carbapenem resistance determinants, including carbapenemase genes (<i>bla</i> <sub>KPC-2</sub>, <i>bla</i> <sub>VIM</sub>, <i>bla</i> <sub>IMP</sub>, <i>bla</i> <sub>NDM</sub>, and <i>bla</i> <sub>OXA-48</sub>) and extended-spectrum β-lactamase (ESBL) genes (<i>bla</i> <sub>TEM</sub>, <i>bla</i> <sub>CTX-M-1</sub>, and <i>bla</i> <sub>SHV</sub>), were analyzed by polymerase chain reaction (PCR). PCR and sequencing assays were performed to detect penicillin-binding protein (PBP) mutations. Efflux pump activity was also assessed in carbapenem-resistant isolates. Quantitative real-time PCR (qRT-PCR) was used to determine the relative mRNA expression levels of outer membrane porin-encoding gene <i>ompC</i> and PBP activator-encoding genes <i>lpoA</i> and <i>lpoB</i>.</p><p><strong>Results: </strong>Twenty-six imipenem-resistant and 108 imipenem-intermediate <i>M. morganii</i> isolates were identified, accounting for 15.29% and 63.53% of cases, respectively. No isolates were resistant to meropenem or ertapenem. Among the 26 carbapenem-resistant isolates, the prevalence of ESBL genes <i>bla</i> <sub>TEM</sub> and <i>bla</i> <sub>CTX-M-1</sub> was 30.77% and 11.54%, respectively, while carbapenemase genes were not detected. Resistant isolates carried more specific PBP mutations than carbapenem-susceptible and carbapenem-intermediate isolates. Efflux pump phenotypes were associated with reduced imipenem susceptibility in 13 carbapenem-resistant isolates. qRT-PCR revealed no significant differences in <i>ompC</i> expression among the resistant, intermediate, and susceptible groups; however, significant differences were observed in <i>lpoA</i> and <i>lpoB</i> expression. Isolates in the imipenem-resistant group carried more PBP mutations.</p><p><strong>Conclusion: </strong><i>M. morganii</i> isolates were commonly non-susceptible to imipenem but remained susceptible to meropenem and ertapenem. Low expression of PBP activator genes (<i>lpoA</i> and <i>lpoB</i>), along with the presence of specific PBP mutations, appeared to be the primary mechanisms of resistance. In addition, efflux pump overexpression may contribute to imipenem resistance in <i>M. morganii</i>.</p>","PeriodicalId":12458,"journal":{"name":"Frontiers in Cellular and Infection Microbiology","volume":"15 ","pages":"1672736"},"PeriodicalIF":4.8000,"publicationDate":"2025-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12446265/pdf/","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Frontiers in Cellular and Infection Microbiology","FirstCategoryId":"3","ListUrlMain":"https://doi.org/10.3389/fcimb.2025.1672736","RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2025/1/1 0:00:00","PubModel":"eCollection","JCR":"Q2","JCRName":"IMMUNOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Objectives: The emergence and spread of carbapenem-resistant Morganella morganii (M. morganii) pose a serious global challenge. This study aimed to investigate the clinical characteristics, resistance patterns, and molecular mechanisms of carbapenem-resistant M. morganii.
Methods: A total of 170 M. morganii clinical isolates were collected from the First Affiliated Hospital of Wenzhou Medical University (Wenzhou, China) between January 2016 and December 2017. Carbapenem MICs were determined by antimicrobial susceptibility testing. Carbapenem resistance determinants, including carbapenemase genes (blaKPC-2, blaVIM, blaIMP, blaNDM, and blaOXA-48) and extended-spectrum β-lactamase (ESBL) genes (blaTEM, blaCTX-M-1, and blaSHV), were analyzed by polymerase chain reaction (PCR). PCR and sequencing assays were performed to detect penicillin-binding protein (PBP) mutations. Efflux pump activity was also assessed in carbapenem-resistant isolates. Quantitative real-time PCR (qRT-PCR) was used to determine the relative mRNA expression levels of outer membrane porin-encoding gene ompC and PBP activator-encoding genes lpoA and lpoB.
Results: Twenty-six imipenem-resistant and 108 imipenem-intermediate M. morganii isolates were identified, accounting for 15.29% and 63.53% of cases, respectively. No isolates were resistant to meropenem or ertapenem. Among the 26 carbapenem-resistant isolates, the prevalence of ESBL genes blaTEM and blaCTX-M-1 was 30.77% and 11.54%, respectively, while carbapenemase genes were not detected. Resistant isolates carried more specific PBP mutations than carbapenem-susceptible and carbapenem-intermediate isolates. Efflux pump phenotypes were associated with reduced imipenem susceptibility in 13 carbapenem-resistant isolates. qRT-PCR revealed no significant differences in ompC expression among the resistant, intermediate, and susceptible groups; however, significant differences were observed in lpoA and lpoB expression. Isolates in the imipenem-resistant group carried more PBP mutations.
Conclusion: M. morganii isolates were commonly non-susceptible to imipenem but remained susceptible to meropenem and ertapenem. Low expression of PBP activator genes (lpoA and lpoB), along with the presence of specific PBP mutations, appeared to be the primary mechanisms of resistance. In addition, efflux pump overexpression may contribute to imipenem resistance in M. morganii.
期刊介绍：
Frontiers in Cellular and Infection Microbiology is a leading specialty journal, publishing rigorously peer-reviewed research across all pathogenic microorganisms and their interaction with their hosts. Chief Editor Yousef Abu Kwaik, University of Louisville is supported by an outstanding Editorial Board of international experts. This multidisciplinary open-access journal is at the forefront of disseminating and communicating scientific knowledge and impactful discoveries to researchers, academics, clinicians and the public worldwide.
Frontiers in Cellular and Infection Microbiology includes research on bacteria, fungi, parasites, viruses, endosymbionts, prions and all microbial pathogens as well as the microbiota and its effect on health and disease in various hosts. The research approaches include molecular microbiology, cellular microbiology, gene regulation, proteomics, signal transduction, pathogenic evolution, genomics, structural biology, and virulence factors as well as model hosts. Areas of research to counteract infectious agents by the host include the host innate and adaptive immune responses as well as metabolic restrictions to various pathogenic microorganisms, vaccine design and development against various pathogenic microorganisms, and the mechanisms of antibiotic resistance and its countermeasures.
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