Diverse Role of blaCTX-M and Porins in Mediating Ertapenem Resistance among Carbapenem-Resistant Enterobacterales

Cody A Black; Raymond Benavides; Sarah M Bandy; Steven D Dallas; Gerard Gawrys; Wonhee So; Alvaro G Moreira; Samantha Aguilar; Kevin Quidilla; Dan F Smelter; Kelly R Reveles; Christopher R Frei; Jim M Koeller; Grace C Lee

doi:10.3390/antibiotics13020185

Diverse Role of bla_CTX-M and Porins in Mediating Ertapenem Resistance among Carbapenem-Resistant Enterobacterales

Antibiotics (Basel). 2024 Feb 13;13(2):185. doi: 10.3390/antibiotics13020185.

Authors

Cody A Black^{1

2}, Raymond Benavides^{1

2}, Sarah M Bandy^{1

2}, Steven D Dallas^{2

3

4}, Gerard Gawrys^{1

2

4}, Wonhee So⁵, Alvaro G Moreira^{2

6}, Samantha Aguilar^{1

2

4}, Kevin Quidilla^{1

2}, Dan F Smelter^{1

2}, Kelly R Reveles^{1

2}, Christopher R Frei^{1

2

4}, Jim M Koeller^{1

2}, Grace C Lee^{1

2

6}

Affiliations

¹ College of Pharmacy, The University of Texas at Austin, Austin, TX 78712, USA.
² Joe R. and Teresa Lozano Long School of Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.
³ Department of Pathology and Laboratory Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.
⁴ University Health System, San Antonio, TX 78229, USA.
⁵ College of Pharmacy, Western University of Health Sciences, Pomona, CA 91766, USA.
⁶ Veterans Administration Research Center for AIDS and HIV-1 Infection and Center for Personalized Medicine, South Texas Veterans Health Care System, San Antonio, TX 78229, USA.

Abstract

Among carbapenem-resistant Enterobacterales (CRE) are diverse mechanisms, including those that are resistant to meropenem but susceptible to ertapenem, adding further complexity to the clinical landscape. This study investigates the emergence of ertapenem-resistant, meropenem-susceptible (ErMs) Escherichia coli and Klebsiella pneumoniae CRE across five hospitals in San Antonio, Texas, USA, from 2012 to 2018. The majority of the CRE isolates were non-carbapenemase producers (NCP; 54%; 41/76); 56% of all NCP isolates had an ErMs phenotype. Among ErMs strains, E. coli comprised the majority (72%). ErMs strains carrying bla_CTX-M had, on average, 9-fold higher copies of bla_CTX-M than CP-ErMs strains as well as approximately 4-fold more copies than bla_CTX-M-positive but ertapenem- and meropenem-susceptible (EsMs) strains (3.7 vs. 0.9, p < 0.001). Notably, carbapenem hydrolysis was observed to be mediated by strains harboring bla_CTX-M with and without a carbapenemase(s). ErMs also carried more mobile genetic elements, particularly IS26 composite transposons, than EsMs (37 vs. 0.2, p < 0.0001). MGE- ISVsa5 was uniquely more abundant in ErMs than either EsMs or ErMr strains, with over 30 more average ISVsa5 counts than both phenotype groups (p < 0.0001). Immunoblot analysis demonstrated the absence of OmpC expression in NCP-ErMs E. coli, with 92% of strains lacking full contig coverage of ompC. Overall, our findings characterize both collaborative and independent efforts between bla_CTX-M and OmpC in ErMs strains, indicating the need to reappraise the term "non-carbapenemase (NCP)", particularly for strains highly expressing bla_CTX-M. To improve outcomes for CRE-infected patients, future efforts should focus on mechanisms underlying the emerging ErMs subphenotype of CRE strains to develop technologies for its rapid detection and provide targeted therapeutic strategies.

Keywords: CRE; ESBL; ertapenem-resistant; extended-spectrum beta-lactamase; meropenem-susceptible; mobile genetic elements; molecular epidemiology; non-carbapenemase-producing; outer-membrane protein; porin loss.

Abstract

Grants and funding