Molecular characterization of multidrug resistant Enterobacterales strains isolated from liver and kidney transplant recipients in Spain

1 Vol.:(0123456789) Scientific Reports | (2021) 11:11875 | https://doi.org/10.1038/s41598-021-90382-5 www.nature.com/scientificreports Molecular characterization of multidrug resistant Enterobacterales strains isolated from liver and kidney transplant recipients in Spain Marta Fernández‑Martínez1,2,27*, Claudia González‑Rico2,3,27, Mónica Gozalo‑Margüello1,2, Francesc Marco4, Irene Gracia‑Ahufinger5,6, Maitane Aranzamendi7,8, Ana M. Sánchez‑Díaz9, Teresa Vicente‑Rangel10, Fernando Chaves11, Jorge Calvo Montes1,2, Luis Martínez‑Martínez5,6,12,27*, Maria Carmen Fariñas2,3,27* & ENTHERE Study Group, the Group for Study of Infection in Transplantation of the Spanish Society of Infectious Diseases and Clinical Microbiology (GESITRA‑SEIMC) and the Spanish Network for Research in Infectious Diseases (REIPI)* The objective of this study was to analyse the mechanisms of resistance to carbapenems and other extended‑spectrum‑β‑lactams and to determine the genetic relatedness of multidrug‑resistant Enterobacterales (MDR‑E) causing colonization or infection in solid‑organ transplantation (SOT) recipients. Prospective cohort study in kidney (n = 142), liver (n = 98) or kidney/pancreas (n = 7) transplant recipients between 2014 and 2018 in seven Spanish hospitals. We included 531 MDR‑E isolates from rectal swabs obtained before transplantation and weekly for 4–6 weeks after the procedure and 10 MDR‑E from clinical samples related to an infection. Overall, 46.2% Escherichia coli, 35.3% Klebsiella pneumoniae, 6.5% Enterobacter cloacae, 6.3% Citrobacter freundii and 5.7% other species were isolated. The number of patients with MDR‑E colonization post‑transplantation (176; 71.3%) was 2.5‑fold the number of patients colonized pre‑transplantation (71; 28.7%). Extended‑ spectrum β‑lactamases (ESBLs) and carbapenemases were detected in 78.0% and 21.1% of MDR‑E isolates respectively. In nine of the 247 (3.6%) transplant patients, the microorganism causing an infection was the same strain previously cultured from surveillance rectal swabs. In our study we have observed a low rate of MDR‑E infection in colonized patients 4–6 weeks post‑transplantation. E. coli producing blaCTX‑M‑G1 and K. pneumoniae harbouring blaOXA‑48 alone or with blaCTX‑M‑G1 were the most prevalent MDR‑E colonization strains in SOT recipients. OPEN 1Servicio de Microbiología, Hospital Universitario Marqués de Valdecilla, Santander, Spain. 2Instituto de Investigación Valdecilla-IDIVAL, Santander, Spain. 3Servicio de Enfermedades Infecciosas, Hospital Universitario Marqués de Valdecilla, Santander, Spain. 4Servicio de Microbiología, Centro Diagnóstico Biomédico, Hospital Clínic. ISGlobal, Universidad de Barcelona, Barcelona, Spain. 5Unidad de Microbiología, Hospital Universitario Reina Sofía, Córdoba, Spain. 6Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC), Córdoba, Spain. 7Servicio de Microbiología, Hospital Universitario de Cruces, Baracaldo, Vizcaya, Spain. 8Instituto de Investigación Sanitaria Biocruces, Vizcaya, Spain. 9Servicio de Microbiología, Hospital Universitario Ramón y Cajal, Madrid, Spain. 10Servicio de Microbiología Clínica y Enfermedades Infecciosas, Hospital General Universitario Gregorio Marañón, Madrid, Spain. 11Servicio de Microbiología, Hospital Universitario 12 de Octubre, Madrid, Spain. 12Departamento of Microbiología, Unidad de Microbiología, Hospital Universitario Reina Sofía, IMIBIC, Universidad de Córdoba, Córdoba, Spain. 27These authors contributed equally: Marta Fernández Martínez, Claudia González-Rico, Luis Martínez-Martínez and Maria Carmen Fariñas. *A list of authors and their affiliations appears at the end of the paper. *email: [email protected]; [email protected]; [email protected] 2 Vol:.(1234567890) Scientific Reports | (2021) 11:11875 | https://doi.org/10.1038/s41598-021-90382-5 www.nature.com/scientificreports/ The prevalence of multidrug-resistant Enterobacterales (MDR-E) as a cause of infection in solid-organ transplant (SOT) patients is progressively increasing, mainly during the first month post-procedure. These infections represent an important cause of morbidity and mortality1,2. Studies examining the outcome of infection caused by extended-spectrum β-lactamase (ESBL)-producing Enterobacterales among SOT recipients report mortality rates ranging from 5 to 20%3. Carbapenemase-producing Enterobacterales infections are associated with high mortality among SOT recipients4. Most MDR-E are organisms producing ESBLs, carbapenemases or AmpC enzymes (by either plasmid-borne genes or derepressed or hyperexpressed chromosomal genes). Among the numerous ESBLs, CTX-M, TEM and SHV are the most commonly detected5. OXA-48-like enzymes along with VIM and KPC are the three most common carbapenemase genes identified in Spain6. Pre-transplant colonization by MDR-E has been described as an important risk factor for infection after SOT7. Several studies recommend the screening of patients at high risk for MDR-E colonization, including SOT recipients8,9. According to these data, it seems advisable to obtain rectal swabs from SOT recipients at the time of transplantation to assess intestinal colonization by MDR-E. Subsequently, surveillance cultures may be recommended depending on the local epidemiological pattern and individual risk factors1. The objective of this study was to characterize the mechanisms of resistance to extended-spectrum cephalosporins and carbapenems and to determine the genetic relatedness of MDR-E involved in both colonization and infection in SOT recipients. Results Study population and bacterial strains. A total of 541 MDR-E isolates were obtained from 247 patients with kidney (n = 142), liver (n = 98) or both kidney and pancreatic transplants (n = 7). Of these, 531 were isolated from rectal samples (460 isolates were obtained post-transplantation; 71, pre-transplantation) and 10 were isolated from clinical samples (Table1). The microorganisms recovered were the following: E. coli (46.2%, n = 250), K. pneumoniae. (35.3%, n = 191), E. cloacae (6.5% n = 35), C. freundii (6.3%, n = 34) and other species (5.7%, n = 31, corresponding to 9 Morganella morganii, 7 Klebsiella oxytoca, 6 Proteus mirabilis, 5 Enterobacter aerogenes, 2 Citrobacter braakii, 1 Enterobacter asburiae and 1 Citrobacter koseri). Table2 shows the distribution of 541 MDR-E isolates recovered from patients according to transplant type. Overall, the isolation rates of E. coli and E. cloacae in kidney recipients were significantly higher than those of liver recipients (143/250, 57.2% vs 104/250, 41.6%, P = 0.042 and 22/35, 62.9% vs 9/35, 25.7%, P = 0.050 respectively). K. pneumoniae was significantly more prevalent in rectal swabs collected post-transplantation (174/460, 37.8%) compared with pre-transplantation (12/71, 16.9%) (P = 0.011). No significant differences were found in the prevalence of the other bacterial species between pre- or post-transplantation rectal swabs (Table1). Antimicrobial susceptibility testing. The activities of the 24 antibiotics against the species most frequently isolated (i.e., E. coli, K. pneumoniae, E. cloacae and C. freundii) among the 345 MDR-E isolates (one isolate per REP-PCR pattern/preliminary antibiogram and patient) are presented in Supplementary Table1. Overall, the resistance rates of the selected MDR-E were 100% to amoxicillin, 98.6% to piperacillin and between 48.4% and 96.8% to cephalosporins. MIC90 values of penicillins, penicillin-β-lactamase inhibitor combinations, cephalosporins and aztreonam were > 256mg/L. The following resistance rates to carbapenems were observed: 4.1% to meropenem, 7.2% to imipenem and 25.8% to ertapenem. Percentages of resistance to aminoglycosides were greater than 37.7% with the exception of amikacin (2.9% resistance rate). Colistin showed the lowest MIC90 (1mg/L). K. pneumoniae (70.2%) exhibited increased resistance to fosfomycin compared with E. coli (9.2%) or other species. K. pneumoniae exhibited increased rates of resistance compared with other organisms, with more than half of the isolates showing resistance to all the antibiotics tested except imipenem (4.1%), amikacin (4.1%), meropenem (8.3%) and colistin (10.7%). Table 1. Distribution of 541 multidrug-resistant Enterobacterales recovered from rectal swabs according to the pre and post-transplantation period and from clinical samples. *Statistically significant differences (bold type)were found between pre- and post-transplant rectal swabs. Other species included: 9 Morganella morganii, 7 Klebsiella oxytoca, 6 Proteus mirabilis, 5 Enterobacter aerogenes, 2 Citrobacter braakii, 1 Enterobacter asburiae and 1 Citrobacter koseri. Rectal swabs (n = 531) Infection (n = 10) P-valuePre-transplant (n = 71) Post-transplant (n = 460) E. coli (250) 46 (64.8%) 202 (43.9%) 2 (20.0%) 0.059 K. pneumoniae (191) 12 (16.9%)* 174 (37.8%)* 5 (50.0%) 0.011 E. cloacae (35) 5 (7.0%) 28 (6,1%) 2 (20.0%) 0.771 C. freundii (34) 5 (7.0%) 29 (6.3%) 0 0.825 Other (31) 3 (4.3%) 27 (5.9%) 1 (10.0%) 0.595 3 Vol.:(0123456789) Scientific Reports | (2021) 11:11875 | https://doi.org/10.1038/s41598-021-90382-5 www.nature.com/scientificreports/ Genes encoding ESBLs, AmpC and carbapenemases. The distribution of isolates with genes encoding ESBLs, plasmid-mediated AmpC or carbapenemases or hyperproducing AmpC among 345 MDR-E isolates is shown in Table3. In all, 269 strains (78.0%) harboured ESBLs genes, CTX-M-group-1 being the most prevalent (53.3%) followed by CTX-M-group-9 in 15.4% of isolates. Detailed information on the exact ESBLs identified is presented in Table4. Carbapenemases were detected in 73 MDR-E isolates (21.1%). Here, blaOXA-48 was the most frequently identified gene (16.5% of the strains), noted mainly in K. pneumoniae, followed by VIM-1 (3.8%) and KPC-2 (0.9%). No other carbapenemase genes were detected. Among ESBL-producers, 2.1% (n = 3) E. coli, 47.3% (n = 52) K. pneumoniae and 11.1% (n = 1) E. cloacae harboured a carbapenemase gene. In 93.0% (53/57) of the isolates producing OXA-48 (51K. pneumoniae and 2 E. coli), CTX-M-15 was also detected. One E. coli harboured VIM-1 plus CTX-M-14, and one K. pneumoniae isolate produced both KPC-2 and CTX-M-15 (Supplementary Information files). Plasmid-mediated AmpC production was observed in four E. coli isolates (2.6%) (3 CIT and one DHA producers), while the hyperproduction of chromosomal-AmpC was detected in E. cloacae (57.7%), C. freundii (82.6%) and other MDR-E species (39.1%). Other mechanisms of resistance to ESBLs could be inferred by interpretative reading of antibiograms, and included SHV-1 hyperproduction (3K. pneumoniae and 1 E. coli), TEM-1 hyperproduction (2 E. coli and 2K. oxytoca), and OXA-1 production (2 E. coli and 2K. oxytoca). Molecular epidemiology. PFGE was performed in 287 isolates: E. coli (n = 141), K. pneumoniae (n = 100), E. cloacae (n = 24) and C. freundii (n = 22). E. coli isolates recovered from different hospitals and patients exhibit high genetic diversity (Supplementary Fig.1). A total of 127 isolates were grouped into 113 pulsotypes, 14 of which were non-typeable. The molecular typing of K. pneumoniae (n = 100) revealed 57 different PFGE-patterns, showing a heterogeneous picture (Supplementary Fig.2). One strain was non-typeable. There were 44 pulsotypes with a single isolate and 13 clusters with two or more isolates. In general, K. pneumoniae strains exhibited greater similarity in PFGE- patterns compared with E. coli isolates with rates of 1.737 and 1.124, respectively. The predominant clone (#22) included 29 isolates belonging to patients from the same hospital and harboured both CTX-M-15 and OXA-48. The dendrograms obtained in E. cloacae and C. freundii demonstrated 21 pulsotypes in both species (Supplementary Figs.3 and 4), revealing high clonal heterogeneity. Table 2. Distribution of 541 multidrug-resistant Enterobacterales recovered from 247 patients according to transplant type. *Statistically significant differences(bold type)were found in the prevalence of bacterial species between kidney and liver transplant. Other species included: 9 Morganella morganii, 7 Klebsiella oxytoca, 6 Proteus mirabilis, 5 Enterobacter aerogenes, 2 Citrobacter braakii, 1 Enterobacter asburiae and 1 Citrobacter koseri. Transplant type Kidney (n = 142) Liver (n = 98) Kidney /pancreas (n = 7) P-value E. coli (250) 143 (57.2%)* 104 (41.6%)* 3 (1.2%) 0.042 K. pneumoniae (191) 83 (43.5%) 99 (51.8%) 9 (4.7%) 0.328 E. cloacae (35) 22 (62.9%)* 9 (25.7%)* 4 (11.4%) 0.050 C. freundii (34) 18 (53.0%) 15 (44.1%) 1 (2.9%) 0.668 Other (31) 16 (51.6%) 15 (48.4%) 0 0.883 Total 282 242 17 Table 3. Distribution of antibiotic resistance genes encoding ESBLs, AmpC and carbapenemases detected in 345 MDR-E isolates from patients with kidney, liver or combined kidney/pancreas transplant. a Other mechanisms were: SHV-1 hyperproduction (4 strains), TEM-1 hyperproduction (4 isolates) and OXA-1 production (4 strains). b Other species included: 7K. oxytoca, 6M. morganii, 4 E. aerogenes, 2 P. mirabilis, 2 C. braakii, 1 E. asburiae and 1 C. koseri. Species (n) bla CTX-M (238) TEM (4) SHV (27) AmpC-producing (47) Carbapenemases (73) Othera (12) CTX-M G1 (184) CTX-M G9 (53) CTX-M G8 (1) Plasmid Chromosomal hyperproduction OXA-48 (57) VIM-1 (13) KPC-2 (3) E. coli (152) 75 (49.3%) 40 (26.3%) 1 (0.6%) 3 (2.0%) 22 (14.3%) 4 (2.6%) 3 (2.0%) 2 (1.3%) – 5 (3.3%) K. pneumoniae (121) 101 (83.5%) 4 (3.3%) – 1 (0.8%) 4 (3.3%) – 53 (43.8%) 4 (3.3%) 3 (2.5%) 3 (2.5%) E. cloacae (26) 2 (7.7%) 6 (23.1%) – – 1 (3.8%) 15 (57.7%) 1 (3.8%) 2 (7.7%) – – C. freundii (23) 1 (4.3%) 2 (8.7%) – – – 19 (82.6%) – 1 (4.3%) – – Othersb (23) 5 (21.7%) 1 (4.3%) – – – 9 (39.1%) – 4 (17.4%) – 4 (17.4%) 4 Vol:.(1234567890) Scientific Reports | (2021) 11:11875 | https://doi.org/10.1038/s41598-021-90382-5 www.nature.com/scientificreports/ Association between faecal carriage and infection. The number of patients colonized with MDR-E during the first month post-transplantation (176; 71.3%) was 2.5-fold the number of colonized pre-transplanta- tion patients (71; 28.7%). In both cases, CTX-M-producing E. coli was the most prevalent MDR-E isolate. Ten out of 247 (4.0%) patients colonized by MDR-E developed infections during the post-transplantation follow-up. Isolates from rectal swabs pre- and post-transplant and infections were compared using PFGE and MLST. Table5 shows the characteristics of these patients and the corresponding organisms. The PFGE patterns are shown in Fig.1. In 9 of these 10 pairs of MDR-E, the colonization and the infection isolates exhibited identical PFGE-typing and STs. In patient 07, the MDR-E obtained in rectal swabs at 1, 2, 3 and 4weeks post-TX were non-typeable with XbaI. However, the isolate causing urinary infection obtained in the sample presented a clear PFGE pattern, so they were considered not clonally related (Fig.1). These isolates presented the same ESBL but with different allelic variants (CTX-M-15 and -32). Discussion In this study, the microbiological characteristics of MDR-E isolated from rectal swabs and clinical isolates in SOT patients were analysed. We found high heterogeneity among MDR-E colonizing isolates using a combination of active pre- and post-transplantation surveillance and molecular epidemiology studies. E. coli and K. pneumoniae represented the majority of MDR-E colonizing strains in our patients, a finding which is consistent with previous studies performed among SOT recipients4,10. ESBLs were identified in 78.0% of MDR-E, and CTX-M-15 was the most prevalent enzyme. These results are similar to those found in multiple reports worldwide5,11. In Spain approximately 20% of infections in SOT recipients are caused by MDR-E, from which 75% are due to ESBL-producing Enterobacterales12. Carbapenemases were detected in 21.1% of MDR-E isolates, and OXA-48 was the most common enzyme followed by VIM-1 and KPC-2. Data from the EuSCAPE project in Spain also showed a predominance of OXA- 48 and a low prevalence of KPC, VIM or NDM enzymes13. Carbapenems have been traditionally considered the drugs of choice for the treatment of infections caused by ESBL or AmpC-producing enterobacteria; however, their use has contributed to the significant worldwide spread of carbapenem resistance. It is therefore important to consider alternative drugs, such as ceftazidimeavibactam (active against most KPC- and OXA-48-producing Enterobacterales), meropenem-vaborbactam and imipenem-relebactam, which have activity against KPC and ESBL-producers14. However, MDR-E isolated in our study show a low resistance rate to meropenem (4.1%) and imipenem (7.2%), in contrast to ertapenem (25.8%) for which resistance rates in K. pneumoniae and E. cloacae were 52.9% and 38.5%, respectively. Surveillance cultures for detection of colonized patients with MDR-E and implementation of contact precautions, among other measures, have allowed a reduction of the infection rate, both in outbreak and in endemic settings9,15. Post-transplantation complications in SOT patients were associated with both MDR-E colonization and infection, suggesting that in-hospital acquisition of MDR-E in the early post-transplantation period plays an important role16,17. In this respect, MDR-E colonization after SOT transplantation has been associated with a Table 4. ESBL genes identified in MDR-E isolated from patients with kidney, liver or combined kidney/ pancreas transplant. ESBLs detected E. coli (141) K. pneumoniae (110) E. cloacae (9) C. freundii (3) Other species (6) SHV-2 2 SHV-12 22 2 1 TEM-19 2 TEM-52 1 TEM-169 1 CTXM-1 6 CTXM-3 1 CTXM-8 1 CTXM-9 7 1 6 1 CTXM-14 22 3 1 CTXM-15 44 97 1 3 CTXM-27 10 CTXM-28 1 CTXM-32 12 1 1 1 2 CTXM-55 6 CTXM-65 1 1 CTXM-138 4 2 CTXM-156 1 CTXM-182 1 5 Vol.:(0123456789) Scientific Reports | (2021) 11:11875 | https://doi.org/10.1038/s41598-021-90382-5 www.nature.com/scientificreports/ subsequent infection at a 1:7 ratio of infected: colonized patients for carbapenem-resistant Enterobacterales and 1:4 for organisms resistant to third-generation cephalosporins17. In this study, we observed a low rate of infection with MDR-E (4.0%) in colonized patients during follow-up in the first six weeks post-transplantation. In an Italian cohort study, infections caused by KPC-producing K. pneumoniae were diagnosed in 29.2% of the liver transplant recipients who were colonized7. Other studies have also described higher infection rates (17%-48%) in colonized liver transplant patients9,16,18. Table 5. Characteristics of the MDR-E isolated by rectal swab and clinical samples from eight kidney and two liver transplant recipients. KT kidney transplant, LT liver transplant, ST sequence type, AMC amoxicillinclavulanic acid, AMK amikacin, AMX amoxicillin, AZT aztreonam, CAZ ceftazidime, CIP ciprofloxacin, COL colistin, CTX cefotaxime, ERT ertapenem, FEP cefepime, FOS fosfomycin, FOX cefoxitin, GN gentamicin, IMP imipenem, LEV levofloxacin, MRP meropenem, NAL nalidixic acid, NET netilmicin, PIP piperacillin, RS rectal sample, ST sequence type, SXT trimethoprim–sulfamethoxazole, TIG tigecycline, TO tobramycin, TZP piperacillin-tazobactam, H1 Hospital Universitario Marqués de Valdecilla, H2 Hospital Clinic, H6 Hospital Reina Sofia. *Isolates from the RS that were selected to compare with infection isolate using MLST. Patients Transplant Species Clinical sample Positive rectal samples (weeks) Antibiotic resistance profile Mechanisms of resistance ST Hospitals PFGE-pattern relationship between MDR-E isolated in rectal swab and clinical sample 01 LT K. pneumoniae Bile 4* AMX, PIP, AMC, TZP, FOX, CTX, CAZ, FEP, AZT, ETP, IMP, MRP, NAL, CIP, LEV, TO, NET, FOS, TIG CTX-M- 15 + OXA-48 11 H1 Same 02 KT K. pneumoniae Urine 1*,2,3,4 AMX, PIP, AMC, TZP, FOX, CTX, CAZ, FEP, AZT, ETP, NAL, CIP, LEV, GN, TO, NET, FOS, SXT, TIG. (urine isolate susceptible to GN, TO, NET,) CTX-M- 15 + OXA-48 11 H1 Same 03 KT K. pneumoniae Skin abscess 1*,3,4 AMX, PIP, AMC, TZP, CTX, CAZ, FEP, AZT, CIP, GN, TO, NET, SXT, TIG CTX-M-15 429 H2 Same 04 LT K. pneumoniae Urine 1*,2*,3 AMX, PIP, AMC, TZP, FOX, CTX, CAZ, FEP, AZT, ETP, IMP, MRP, NAL, CIP, LEV, AMK, TO, NET, FOS, TIG, COL KPC-2 512 H6 Same except RS-1 05 KT K. pneumoniae Urine 2* AMX, PIP, AMC, TZP, CTX, CAZ, FEP, AZT, NAL, CIP, LEV, GN, TO, NET, SXT, TIG, CTX-M-15 307 H6 Same 06 KT E. coli Urine Pre-TX*,1,3,4 AMX, PIP, AMC, CTX, CAZ, FEP, AZT, NAL, CIP, LEV, TO NET. (urine isolate susceptible to CAZ and FEP) CTX-M-15 43 H1 Same 07 KT E. coli Urine 1*,2,3,4 AMX, PIP, AMC, TZP, CTX, CAZ, FEP, AZT, NAL, CIP, LEV, TO, NET. (strain from RS-1 susceptible to AMC, TO, NET) CTX-M-15 (urine), CTX-M- 32 (RS-1) 621 (urine) and 83 (RS1) H6 Different 08 KT E. cloacae Blood 1* AMX, PIP, AMC, TZP, FOX, CTX, NAL, FOS, TIG CTX-M-9 97 H1 Same 09 KT E. cloacae Catheter 4* AMX, PIP, AMC, FOX, CTX, NAL, FOS Hyper AmpC 781 H6 Same 10 KT K. oxytoca Urine 1* AMX, PIP, AMC, TZP, AZT Hyper TEM-1 213 H6 Same 6 Vol:.(1234567890) Scientific Reports | (2021) 11:11875 | https://doi.org/10.1038/s41598-021-90382-5 www.nature.com/scientificreports/ Molecular typing of our isolates (PFGE and MLST) revealed significant genetic diversity. Bert etal. also found high clonal diversity between ESBL-producing Enterobacterales obtained from colonization and infection after liver transplantation18. These findings indicate that MDR-E infections in our patients were not related to the hospital spread of specific clones. The high-risk ST-11K. pneumoniae strain has been frequently detected worldwide as a successful virulent pathogen with determinants for resistance, including VIM, OXA-4819 and KPC-production20. In our study, all ST11 strains carried CTXM-15 and OXA-48. In recent years, new international drug-resistant lineages have emerged. Among these, K. pneumoniae ST307 and KPC-producing K. pneumoniae ST512 have been recognized in several countries including Spain20,21. ST307 was strongly associated with the diffusion of CTX-M-15, and in France, it has recently been defined as a new successful high-risk clone associated with the dissemination of KPC genes22. Both clones were detected as a cause of urinary infection in two patients in our study. Some study limitations should be considered when extrapolating our results. First, we only collected rectal swabs, which may be inadequate for detecting resistant pathogens present in small amounts. Nevertheless,there is evidence that rectal swabs are more sensitive than other anatomical sites for detecting MDR-E. Secondly, we performed molecular characterization of 541 MDR-E corresponding to 80.2% of colonized patients pre or post-transplantation. Some hospitals did not send all MDR-E isolated from patients enrolled in the study to the coordinating center. And finally, this is a study restricted to a single country, a fact that may limit the extrapolation of its results to other territories. However, it is a prospective study conducted in seven University hospitals in southern Europe where a pioneering transplant program is implemented, and our results may be useful for comparing the evolution of MDR-E among SOT recipients with neighbouring countries. In summary, molecular typing of MDR-E revealed significant genetic diversity.E. coliproducing blaCTX-M-G1was the principal MDR-E colonizing strain in liver and/or kidney transplant recipients, followed by K. pneumoniae harbouring blaOXA-48alone or with blaCTX-M-G1.Rectal colonization by MDR-E increased in the first month after transplantation compared to before transplantation; however, this was not reflected in the infections since there was a low rate of infection by MDR-E during the six-week post-transplantation follow-up. Materials and methods Study population and setting. This prospective cohort study, which is part of a prospective multicentre cohort study of intestinal colonization by MDR-E in kidney, liver or combined kidney and pancreas transplant recipients in seven Spanish University Hospitals (The ENTHERE study), was conducted between 29 August 2014 and 9 April 201823–25. Adult patients aged 18years or older undergoing liver, kidney, or pancreas transplantation during the indicated period were included. Patients were followed up 24–48h before transplantation, Figure1. PFGE patterns of MDR-E from rectal swabs obtained pre-transplant (pre-TX) or post-transplant (number indicates weeks for rectal swabs) and from infection-related strains in 10 transplant recipients (P1 to P10 corresponding to Table5). The PFGE profiles were obtained from different agarose gels and grouped in this figure. (P7: isolates 1, 2, 3 and 4 were non-typeable with XbaI). 7 Vol.:(0123456789) Scientific Reports | (2021) 11:11875 | https://doi.org/10.1038/s41598-021-90382-5 www.nature.com/scientificreports/ weekly until 6weeks after transplantation, or until death, if this occurred within the indicated period. Intestinal colonization was defined as the isolation of MDR-E in a rectal swab. Infections were defined according to CDC criteria26. Of the 931 patients included in the study, no MDR-E were isolated from any of the rectal swabs collected pre- or post-transplantation in 623 patients. In 308 patients in whom MDR-E was isolated in pre- and post-transplant samples, only 247 patient samples were sent to the coordination center for further analysis. Bacterial strains. A total of 531 MDR-E isolates, defined as producing one or more ESBLs, plasmid-medi- ated or derepressed AmpC or carbapenemases, were included in this study. Rectal swabs were taken 24–48h pre-transplantation and weekly up to 6weeks post-transplantation and inoculated onto both ChromID-ESBL and ChromID-CARBA agar plates (BIOMERIEUX, Marcy L’Étoile, France). During the 6weeks of follow-up, 10 isolates from patients who developed MDR-E infections were also included. Antimicrobial susceptibility testing. All 541 MDR-E isolates underwent susceptibility testing for 24 antimicrobials, including amoxicillin, amoxicillin-clavulanic acid (2mg/L), piperacillin, piperacillin-tazobactam (4mg/L), cefoxitin, cefotaxime, ceftazidime, cefepime, aztreonam, imipenem, meropenem, ertapenem, amikacin, gentamicin, tobramycin, netilmicin, arbekacin, nalidixic acid, ciprofloxacin, levofloxacin, trimethoprimsulfamethoxazole, fosfomycin, tigecycline, and colistin, by standardized broth-microdilution methods according to CLSI guidelines27. The results were interpreted using EUCAST clinical breakpoints28. No breakpoints have been established by EUCAST for arbekacin and nalidixic acid, so the MIC values have been specified. E. coli ATCC 25922, E. coli ATCC 35218, and P. aeruginosa ATCC 27853 were used as quality control strains. Compounds with new β-lactamase inhibitors, such as ceftazidime-avibactam and meropenem-vaborbactam, were not available when the study was planned and consequently could not be tested. Molecular fingerprinting. Genetic relatedness was first studied by repetitive-extragenic-palindromic PCR (REP-PCR)29 in all 541 MDR-E. Subsequently, the clonal relationship was also determined by pulsed-field gel electrophoresis (PFGE) in at least one strain per patient or strains from the same patient if they had two or more differing bands on REP-PCR. Bacterial DNA was embedded in agarose plugs and digested with 20 U of XbaI at 37ºC overnight. The fragments were separated in 1% agarose gel at 6V/cm and 14°C with 0.5xTBE buffer using the CHEF-DRII-system (BIO-RAD, California, USA). Pulse times ranged from 1-5s for 7h and 15-35s for 16h. PFGE-patterns were analysed with Fingerprinting II v4.5 software (BIO-RAD). Isolates were classified as indistinguishable if they showed > 95% similarity, as closely related subtypes with 85–95% similarity, and as different strains with similarity < 85%. Molecular characterization of resistance genes. In a selection of 345 MDR-E isolates (one isolate per REP-PCR-pattern/patient and antibiogram pattern), standard-PCR was used to detect the presence of genes encoding ESBLs (blaTEM, blaSHV and blaCTX-M). PCR to detect carbapenemase genes (blaKPC, blaVIM, blaIMP, blaNDM and blaOXA-48) was performed in 90 out 345 MDR-E isolates with a meropenem MIC > 0.125mg/L, as recommended by EUCAST. In 59 out of 345 isolates not producing an ESBL or carbapenemase gene, multiplex-PCR was performed to detect plasmid-mediated AmpC (blaCIT, blaFOX, blaMOX, blaDHA, blaACC and blaEBC). The primers and PCR conditions used are provided in Supplementary Table2 online. Representative amplification products were sequenced and analysed in GenBank (www. ncbi. nlm. nih. gov/ BLAST). Multilocus Sequence Typing (MLST). MLST was determined for 21 MDR-E isolates collected from 10 patients, including 10 isolates from post-transplantation clinical samples related to an infection and 11 isolates that colonized these infected patients, corresponding to the first rectal swab from which MDR-E were obtained. Four Escherichia coli and 11 Klebsiella pneumoniae isolates were assessed using the Pasteur Institute protocols (h ttps:// bigsdb. paste ur. fr/ index. html). For K. pneumoniae, the methodology was used as described30. PubMLST (https:// pubml st. org/ datab ases/)31 was used to determine the sequence types (ST) of 2 Klebsiella oxytoca and 4 Enterobacter cloacae. Ethics statement. The study was performed in accordance with the Declaration of Helsinki. 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This research was supported by ‘Plan Nacional de I+D+i and Instituto de Salud Carlos III (Fondo de Investigaciones Sanitarias 13/01191), Subdirección General de Redes y Centros de Investigación Cooperativa, Ministerio de Ciencia, Innovación y Universidades, and the Spanish Network for Research in Infectious Diseases (REIPI RD16/0016/0007, RD16/0016/0010, RD16/0016/0012, RD16/0016/0011, RD16/0016/0008, RD16/0016/0002). The study was co-financed by the European Development Regional Fund “A way to achieve Europe” and the Operative Program Intelligent Growth 2014‐2020. Author contributions M.F.-M., C.G.-R. L.M.-M. and M.C.F were responsible for the study’s conception and designed the experiments. M.C.F obtained funding and M.F.-M. and C.G.-R. performed the experiments. Data acquisition, analysis or interpretation was performed by M.F.-M., C.G.-R. L.M.-M. and M.C.F. All authors contributed strains. M.F.M., L.M.M. and M.C.F. wrote the paper. All authors participated in critical revisions of the manuscript and approved the final manuscript. 9 Vol.:(0123456789) Scientific Reports | (2021) 11:11875 | https://doi.org/10.1038/s41598-021-90382-5 www.nature.com/scientificreports/ Competing interests The authors declare no competing interests. Additional information Supplementary Information The online version contains supplementary material available at https:// doi. org/ 10. 1038/ s41598- 021- 90382-5. Correspondence and requests for materials should be addressed to M.F.-M., L.M.-M.orM.C.F. Reprints and permissions information is available at www.nature.com/reprints. Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. 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To view a copy of this licence, visit http:// creat iveco mmons. org/ licen ses/ by/4. 0/. © The Author(s) 2021 ENTHERE Study Group, the Group for Study of Infection in Transplantation of the Spanish Society of Infectious Diseases and Clinical Microbiology (GESITRA‑SEIMC) and the Spanish Network for Research in Infectious Diseases (REIPI) Carlos Salas1,2, Carlos Armiñanzas2,3, Francisco Arnaiz de las Revillas2,3, Fernando Casafont‑Morencos13, Antonio Cuadrado Lavín13, Emilio Fábrega13, Concepción Fariñas‑Álvarez14, Virginia Flor Morales14, Emilio Rodrigo15, Juan Carlos Ruiz San Millán15, Marta Bodro16, Asunción Moreno16, Laura Linares16, Miquel Navasa17, Frederic Cofan18, Fernando Rodríguez5, Julián Torre‑Cisneros19, Aurora Páez Vega19, José Miguel Montejo20, María José Blanco20, Javier Nieto Arana20, Jesús Fortún21, Rosa Escudero Sánchez21, Pilar Martin Dávila21, Patricia Ruiz Garbajosa9, Adolfo Martínez22, Javier Graus23, Ana Fernández24, Patricia Muñoz10, Maricela Valerio10, Marina Machado10, María Olmedo10, Caroline Agnelli Bento10, Cristina Rincón Sanz10, María Luisa Rodríguez Ferrero25, Luis Alberto Sánchez Cámara25, José María Aguado26 & Elena Resino26 13Servicio de Digestivo, Hospital Universitario Marqués de Valdecilla, Santander, Spain. 14Unidad de Calidad, Hospital Universitario Marqués de Valdecilla, Santander, Spain. 15Servicio de Nefrología, Hospital Universitario Marqués de Valdecilla, Santander, Spain. 16Servicio de Enfermedades Infecciosas, Hospital Clínic-IDIBAPS, Barcelona, Spain. 17Unidad de Hígado, Hospital Clínic-IDIBAPS, Universidad de Barcelona, Barcelona, Spain. 18Departamento de Nefrología, Hospital Clínic-IDIBAPS, Universidad de Barcelona, Barcelona, Spain. 19Servicio de Enfermedades Infecciosas, Hospital Universitario Reina Sofía, Córdoba, Spain. 20Unidad de Enfermedades Infecciosas, Hospital Universitario de Cruces, Barakaldo, Spain. 21Departamento de Enfermedades Infecciosas, Hospital Universitario Ramón y Cajal, Madrid, Spain. 22Coordinación de Trasplante, Hospital Universitario Ramón y Cajal, Madrid, Spain. 23Unidad de Hígado, Hospital Universitario Ramón y Cajal, Madrid, Spain. 24Departamento de Nefrología, Hospital Universitario Ramón y Cajal, Madrid, Spain. 25Departamento de Nefrología, Hospital General Universitario Gregorio Marañon, Madrid, Spain. 26Unidad de Enfermedades Infecciosas, Hospital Universitario, 12 de Octubre, Madrid, Spain.