Distinctive features of ertapenem mono-resistant carbapenem-resistant Enterobacterales in the United States: A cohort study

Background Carbapenem-resistant Enterobacterales (CRE) are highly antibiotic-resistant bacteria. Whether CRE resistant only to ertapenem among carbapenems (ertapenem “mono-resistant”) represent a unique CRE subset with regards to risk factors, carbapenemase genes, and outcomes is unknown. Methods We analyzed surveillance data from nine CDC Emerging Infections Program (EIP) sites. A case was the first isolation of a carbapenem-resistant Enterobacter cloacae complex, Escherichia coli, Klebsiella aerogenes, K. oxytoca, K. pneumoniae, or K. variicola from a normally sterile site or urine in an EIP catchment area resident in 2016-2017. We compared risk factors, carbapenemase genes, antibiotic susceptibility, and mortality of ertapenem “mono-resistant” cases to “other” CRE cases (resistant to ≥1 carbapenem other than ertapenem), and analyzed risk factors for mortality. Results Of 2009 cases, 1249 (62.2%) were ertapenem mono-resistant and 760 (37.8%) were other CRE. Ertapenem mono-resistant CRE cases were more frequently ≥80 years old (29.1% vs. 19.5%, p<0.0001) and female (67.9% vs 59.0%, p<0.0001). Ertapenem mono-resistant isolates were more likely to be Enterobacter cloacae complex (48.4% vs. 15.4%, p<0.0001) but less likely to be isolated from a normally sterile site (7.1% vs. 11.7%, p<0.01) or have a carbapenemase gene (2.4% vs. 47.4%, p<0.0001). Ertapenem mono-resistance was not associated with 90-day mortality in logistic regression models. Carbapenemase-positive isolates were associated with mortality (odds ratio 1.93, 95% confidence interval 1.30-2.86). Conclusions Ertapenem mono-resistant CRE rarely have carbapenemase genes and have distinct clinical and microbiologic characteristics from other CRE. These findings may inform antibiotic choice and infection prevention practices, particularly when carbapenemase testing is not available.

Primer reporte de Enterobacterales dobles productores de carbapenemasas en hospitales de Paraguay. Año 2021.

Las carbapenemasas se encuentran ampliamente distribuidas en nuestro país, tanto en bacilos gramnegativos fermentadores como no fermentadores. Durante 2021, se ha reportado incremento de cepas con estas enzimas. Con el objetivo de evaluar la doble producción de carbapenemasas en Enterobacterales y comunicar su circulación, fue puesta a punto una PCR convencional múltiple. Estudio retrospectivo en 128 aislamientos provenientes de 20 centros colaboradores de la Red Nacional de Vigilancia de la RAM (Capital, Central e interior del país), remitidos al LCSP entre febrero y setiembre de 2021, para confirmación y genotipificación de carbapenemasas. Se realizaron pruebas fenotípicas y colorimétricas con sustratos específicos, y pruebas genotípicas (PCR convencional múltiple) para la detección simultánea de varios genes de resistencia (bla NDM, bla KPC, bla OXA-48-like, bla IMP y bla VIM). De los 128 aislamientos estudiados, 107 correspondieron a Klebsiella pneumoniae, 14 a Enterobacter cloacae complex, entre otros; aislados en mayor frecuencia de muestras de orina (30%), respiratorias (30%), sangre y catéter (24%). Los genes de resistencia a los carbapenemes detectados fueron: bla NDM (77,3%), bla KPC (17,2%); siendo confirmada la doble producción de carbapenemasas en 7 aislamientos (5,5%) provenientes de 4 centros diferentes de la capital de país y uno de Central; 6 de ellas (K. pneumoniae) con bla NDM+bla KPC y 1 (E. cloacae complex) con bla NDM+bla OXA-48-like; confirmando circulación de Enterobacterales dobles productores de carbapenemasas en el país (KPC+NDM y OXA+NDM); hallazgos que obligan a proveer de capacidades de detección, de manera a que se puedan tomar medidas oportunas y eficaces de contención y control.

178. Endemic Carbapenem Resistance Driven By Clonal and Horizontal Spread of blaIMP-4 Across Diverse Enterobacterales: Jumping Genes, Promiscuous Plasmids and Killer Clones

Background Carbapenem-resistant Enterobacterales (CRE) have become endemic and cause significant morbidity and mortality globally. The metallo-beta-lactamase gene blaIMP-4 is a key CRE resistance determinant in Australia and Asia but its genomic context remains unknown. We aimed to determine the genomic epidemiology of blaIMP-4 in clinical and environmental isolates from 2008 – 2020 at our institution. Methods We performed whole genome sequencing on 219 blaIMP-4-carrying isolates from 134 patients (219 short-read and 75 long-read). Multi-locus sequence types (MLSTs), resistance determinants and plasmid replicons were assessed. High-quality de novo hybrid assemblies were used to identify location of blaIMP-4 gene. We conducted phylogenetic analysis for key MLSTs and plasmids. Results Bla IMP-4 was noted on a class I integron also harboring aminoglycoside, sulfamethoxazole, chloramphenicol and quaternary ammonium compound resistance genes. This integron was able to migrate over time to 10 bacterial species (42 STs) and 6 different plasmid types (Figure 1 and Figure 2). From 2008-2020, blaIMP-4 was present on IncC plasmids in Serratia marcescens and Klebsiella pneumoniae. We noted small outbreaks of Pseudomonas aeruginosa ST111 with chromosomal integration of blaIMP-4 from 2008-2018 (16 isolates) and Enterobacter cloacae complex ST114 with blaIMP-4 on IncFIB(K)/IncFIA(HI1) plasmids from 2011-2020 (19 isolates). From 2016-2020, there was an explosion of diverse IncHI2 plasmids carrying blaIMP-4. This was driven by clonal expansion of E. cloacae complex ST93/ST190 (79 isolates), with spillover of IncHI2 plasmids to Klebsiella spp (13 isolates), Citrobacter spp (2 isolates), S. marcescens (1 isolate), Escherichia coli (4 isolates). In addition to blaIMP-4, these plasmids carried mcr-9.1, a colistin resistance gene, and resistance determinants to nearly all key classes of Gram-negative antimicrobials. Figure 1. Bacterial species harboring blaIMP-4 2008-2020 BlaIMP-4 was noted in diverse bacterial species over the study period. Serratia marcescens and Klebsiella pneumoniae were present throughout. Outbreaks of Enterobacter cloacae complex ST114, ST190 and ST93 and Pseudomonas aeruginosa ST111 were noted. Figure 2. Diverse plasmids associated with blaIMP-4 carriage determined by de novo hybrid assembly Presence of blaIMP-4 on diverse plasmids that varied through the study period was noted. Plasmids were charaterised by analysing de novo hybrid assembly data and co-location of blaIMP-4 and plasmid replicons on the same contigs. Conclusion Bla IMP-4 spread on a class I integron was responsible for endemic carbapenem resistance at our institution. This mobile genetic element was able to persist due to both clonal spread and entry into diverse plasmids. Concerningly, we noted a large outbreak driven by IncHI2 plasmids harboring colistin resistance genes with spread to multiple bacterial species. Disclosures All Authors: No reported disclosures

177. Distinctive Features of Ertapenem Mono-Resistant Carbapenem-Resistant Enterobacterales in the United States: A Cohort Study

Background Carbapenem-resistant Enterobacterales (CRE) are highly antibiotic-resistant bacteria. Whether CRE resistant only to ertapenem among carbapenems (ertapenem mono-resistant) represent a unique CRE subset with regards to risk factors, carbapenemase genes, and outcomes is unknown. Methods We analyzed laboratory- and population-based surveillance data from nine sites participating in CDC’s Emerging Infections Program (EIP). We defined an incident case as the first isolation of Enterobacter cloacae complex, Escherichia coli, Klebsiella aerogenes, K. oxytoca, K. pneumoniae, or K. variicola resistant to doripenem, ertapenem, imipenem, or meropenem (determined at clinical laboratory) from a normally sterile site or urine identified from a resident of the EIP catchment area in 2016-2017. We compared risk factors, carbapenemase genes (determined via polymerase chain reaction at CDC), and mortality of cases with ertapenem “mono-resistant” to “other” CRE (resistant to ≥ 1 carbapenem other than ertapenem). We additionally conducted survival analysis to determine the effect of ertapenem mono-resistant status and isolate source (sterile vs. urine) on survival. Results Of 2009 cases, 1249 (62.2%) were ertapenem mono-resistant and 760 (37.8%) were other CRE (Figure 1). Ertapenem mono-resistant CRE cases were more frequently ≥ 80 years old (29.1% vs. 19.5%, p< 0.0001), female (67.9% vs 59.0%, p< 0.0001), and white (62.6% vs. 45.1%, p< 0.0001). Ertapenem mono-resistant isolates were more likely than other CRE to be Enterobacter cloacae complex (48.4% vs. 15.4%, p< 0.0001) but less likely to be isolated from a normally sterile site (7.1% vs. 11.7%, p< 0.01) or have a carbapenemase gene (2.4% vs. 47.4%, p< 0.0001) (Figure 2). Ertapenem mono-resistance was not associated with difference in 90-day mortality (unadjusted odds ratio [OR] 0.82, 95% confidence interval [CI] 0.63-1.06) in logistic models or survival analysis (Figure 3). Figure 1. Flow diagram of carbapenem-resistant Enterobacterales cases included in analysis, 2017-2018. CRE, carbapenem-resistant Enterobacterales; MIC, minimum inhibitory concentration. Ertapenem mono-resistant CRE are only resistant to ertapenem (among carbapenems). Other CRE are resistant to ≥1 carbapenem other than ertapenem. We excluded isolates that (1) had no interpretable MICs for any carbapenem, (2) were only tested against ertapenem, (3) had unknown death status, or (4) were not associated with patient’s first incident case. Figure 2. Proportion of ertapenem mono-resistant carbapenem-resistant Enterobacterales (CRE) vs. other CRE isolates with specific carbapenemase genes. KPC, Klebsiella pneumoniae carbapenemase; NDM, New Delhi metallo-ß-lactamase; OXA, oxacillinase. Ertapenem mono-resistant carbapenem-resistant Enterobacterales (CRE) are only resistant to ertapenem (among carbapenems). Other CRE are resistant to ≥1 carbapenem other than ertapenem. Testing via reverse transcriptase polymerase chain reaction. Figure 3. Survival analysis comparing patients with carbapenem-resistant Enterobacterales (CRE) that are ertapenem mono-resistant to other CRE (i.e., resistant to ≥1 carbapenem other than ertapenem), either total (A) or stratified by isolate site (B). Ertapenem mono-resistant) isolates were not associated with decreased mortality, and sterile isolate source (i.e., non-urinary isolates) was associated with increased mortality regardless of ertapenem mono-resistance. Conclusion Ertapenem mono-resistant CRE rarely have carbapenemase genes and have distinct clinical and microbiologic characteristics compared to other CRE. These findings may inform antibiotic choice particularly when testing for carbapenemases is not readily available. Disclosures All Authors: No reported disclosures

Revisiting Species Identification within the Enterobacter cloacae Complex by Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry

Creation of a database of MALDI-TOF reference spectral profiles with a high number of representatives associated with the performant MSI software enables substantial improvement in identification of E. cloacae complex members. Moreover, this online database is available through a free online MSI application ( https://msi.happy-dev.fr/ ).