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Competing Interests: Disclosure The authors have stated that they have no conflicts of interest.

Purpose: High-grade gliomas (HGG) carry a poor prognosis, with glioblastoma accounting for almost 50% of primary brain malignancies in the elderly. Unfortunately, despite the use of multiple treatment modalities, the prognosis remains poor in this population. Our preclinical studies suggest that the presence of aromatase expression, encoded by CYP19A1, is significantly upregulated in HGGs. Remarkably, we find that letrozole (LTZ), an FDA-approved aromatase inhibitor, has marked activity against HGGs., Patients and Methods: We conducted a phase 0/I single-center clinical trial (NCT03122197) to assess the tumoral availability, pharmacokinetics (PK), safety, and tolerability of LTZ in recurrent patients with HGG. Planned dose cohorts included 2.5, 5, 10, 12.5, 15, 17.5, and 20 mg of LTZ administered daily pre- and postsurgery or biopsy. Tumor samples were assayed for LTZ content and relevant biomarkers. The recommended phase 2 dose (R2PD) was determined as the dose that resulted in predicted steady-state tumoral extracellular fluid (ECF; Css,ecf) >2 μmol/L and did not result in ≥33% dose-limiting adverse events (AE) assessed using CTCAE v5.0., Results: Twenty-one patients were enrolled. Common LTZ-related AEs included fatigue, nausea, musculoskeletal, anxiety, and dysphoric mood. No DLTs were observed. The 15 mg dose achieved a Css,ecf of 3.6 ± 0.59 μmol/L. LTZ caused dose-dependent inhibition of estradiol synthesis and modulated DNA damage pathways in tumor tissues as evident using RNA-sequencing analysis., Conclusions: On the basis of safety, brain tumoral PK, and mechanistic data, 15 mg daily is identified as the RP2D for future trials., (©2024 American Association for Cancer Research.)

Background and Objective: Immune checkpoint inhibitors (ICIs) have been widely applied and studied in the treatment of gastrointestinal (GI) cancers, and have achieved good results. However, in clinical practice, it has been observed that only some patients respond well to ICIs, and some patients may experience various degrees of adverse reactions during the treatment. Timely evaluation of the potential therapeutic effects and adverse reactions of ICIs for patients has important clinical significance. This review aimed to summarize recent progress regarding efficacy-associated biomarkers for ICIs in GI cancer., Methods: The literature on ICI treatment in GI cancers was searched in the PubMed, Embase, and Cochrane Library databases for publications up to April 2023., Key Content and Findings: Clinical practice and research has gradually revealed some biomarkers related to the treatment of GI cancers with ICIs, which can be roughly divided into three types: biomarkers that predict the effectiveness of ICIs treatment, biomarkers associated with resistance to ICIs, and biomarkers associated with immune related adverse events (irAEs). This review article provides a literature review on biomarkers related to the efficacy of ICIs in the treatment of GI cancers., Conclusions: According to existing clinical research results, there are multiple biomarkers that can be used for predicting and monitoring the efficacy and risk of adverse events of ICIs in the treatment of digestive system malignant tumors., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jgo.amegroups.com/article/view/10.21037/jgo-23-843/coif). P.Z. reports funding supports from General Project of Key Research and Development Plan, Shaanxi Provincial Department of Science and Technology (No. 2021SF-374) and General Research Project of Xi'an Science and Technology Bureau (No. 23YXYJ0136). A.M. received payment/honoraria for being speaker and panelist at ASCO Advantage program upper GI cancer program in Virginia, USA for 2022 and 2023. S.L. reports consulting fees from Cancer Study Group and expert witness fees from Kipp and Christian. The other authors have no conflicts of interest to declare., (2024 Journal of Gastrointestinal Oncology. All rights reserved.)

Background: Macrovascular invasion and(or) extrahepatic metastasis are the main clinical characteristics of Chinese patients with hepatocellular carcinoma (HCC) after entering the second-line treatment. The aim of this study was to explore the efficacy and safety of regorafenib as a second-line treatment for these patients with HCC., Methods: We selected 253 patients with primary liver cancer who were treated in Henan Cancer Hospital from June 2017 to September 2020. According to the inclusion and exclusion criteria, 63 patients with HCC with macrovascular invasion and/or extrahepatic metastasis were finally included. The clinical data of patients were obtained by consulting the electronic medical record system and through telephone follow-up. The median overall survival (mOS), duration of drug use, and disease control rate (DCR) of patients were evaluated, and the Cox regression model was used to analyze the risk factors of prognosis., Results: The mOS of 63 patients with HCC administered regorafenib as second-line treatment was 9.6 months, the duration of drug use was 3.8 months, and the DCR was 59% (37/63). Cox multivariate analysis showed that overall survival (OS) was closely related to the level of alpha-fetoprotein (AFP) and treatment method but not to the type of first-line drug. The mOS of patients with AFP ≥400 ng/mL was 7.4 months, which was significantly lower than that of those with AFP <400 ng/mL (12.5 months) (P=0.0052). The mOS of patients treated with regorafenib alone was 6.8 months, which was significantly lower than that of those treated with regorafenib combined with immunotherapy (24.3 months) and intervention therapy (17.5 months) (P<0.0001). The mOS of patients using regorafenib as second-line treatment in the first-line sorafenib group and first-line nonsorafenib group were 9.5 and 9.6 months, respectively (P=0.9766). The grade ≥3 adverse events (AEs) with an incidence of more than 10% included hand-foot syndrome, increased bilirubin, decreased albumin, and elevated transaminase, with incidences of 22%, 14%, 11%, and 10%, respectively., Conclusions: As second-line treatment for patients with HCC with macrovascular invasion and(or) extrahepatic metastasis, regorafenib has definite efficacy and tolerable adverse reactions. It is the preferred drug for the second-line treatment of patients with advanced HCC., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jgo.amegroups.com/article/view/10.21037/jgo-23-651/coif). S.G. serves as the Chair of DSMB, Imaging and Radiation Therapy Committee, Center for Cancer Research @ NCI. He holds leadership position on Advances in Radiation Oncology. He is in Editorial Board of The Breast Journal and Frontiers in Radiation Oncology. No payments were made to Sharad Goyal. The other authors have no conflicts of interest to declare., (2023 Journal of Gastrointestinal Oncology. All rights reserved.)

Background: Limited information is available for patients with breast cancer (BC) and coronavirus disease 2019 (COVID-19), especially among underrepresented racial/ethnic populations., Methods: This is a COVID-19 and Cancer Consortium (CCC19) registry-based retrospective cohort study of females with active or history of BC and laboratory-confirmed severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection diagnosed between March 2020 and June 2021 in the US. Primary outcome was COVID-19 severity measured on a five-level ordinal scale, including none of the following complications, hospitalization, intensive care unit admission, mechanical ventilation, and all-cause mortality. Multivariable ordinal logistic regression model identified characteristics associated with COVID-19 severity., Results: 1383 female patient records with BC and COVID-19 were included in the analysis, the median age was 61 years, and median follow-up was 90 days. Multivariable analysis revealed higher odds of COVID-19 severity for older age (aOR per decade, 1.48 [95% CI, 1.32-1.67]); Black patients (aOR 1.74; 95 CI 1.24-2.45), Asian Americans and Pacific Islander patients (aOR 3.40; 95 CI 1.70-6.79) and Other (aOR 2.97; 95 CI 1.71-5.17) racial/ethnic groups; worse ECOG performance status (ECOG PS ≥2: aOR, 7.78 [95% CI, 4.83-12.5]); pre-existing cardiovascular (aOR, 2.26 [95% CI, 1.63-3.15])/pulmonary comorbidities (aOR, 1.65 [95% CI, 1.20-2.29]); diabetes mellitus (aOR, 2.25 [95% CI, 1.66-3.04]); and active and progressing cancer (aOR, 12.5 [95% CI, 6.89-22.6]). Hispanic ethnicity, timing, and type of anti-cancer therapy modalities were not significantly associated with worse COVID-19 outcomes. The total all-cause mortality and hospitalization rate for the entire cohort was 9% and 37%, respectively however, it varied according to the BC disease status., Conclusions: Using one of the largest registries on cancer and COVID-19, we identified patient and BC-related factors associated with worse COVID-19 outcomes. After adjusting for baseline characteristics, underrepresented racial/ethnic patients experienced worse outcomes compared to non-Hispanic White patients., Funding: This study was partly supported by National Cancer Institute grant number P30 CA068485 to Tianyi Sun, Sanjay Mishra, Benjamin French, Jeremy L Warner; P30-CA046592 to Christopher R Friese; P30 CA023100 for Rana R McKay; P30-CA054174 for Pankil K Shah and Dimpy P Shah; KL2 TR002646 for Pankil Shah and the American Cancer Society and Hope Foundation for Cancer Research (MRSG-16-152-01-CCE) and P30-CA054174 for Dimpy P Shah. REDCap is developed and supported by Vanderbilt Institute for Clinical and Translational Research grant support (UL1 TR000445 from NCATS/NIH). The funding sources had no role in the writing of the manuscript or the decision to submit it for publication., Clinical Trial Number: CCC19 registry is registered on ClinicalTrials.gov, NCT04354701., Competing Interests: GN, SV, AK, TS, NK, DA, JA, JA, ZB, NB, TB, BB, SB, MB, PB, SB, BB, HB, CC, HC, JD, AD, NE, LF, DF, CF, MG, CG, PG, SG, MH, HH, DH, CH, CJ, SJ, MJ, VK, EK, NK, VK, AK, DK, CL, PL, KL, ML, XL, GL, GL, DM, AM, MM, SM, RM, IM, VM, RN, SN, RN, TN, TO, OP, KP, JP, KP, JP, HP, MP, YR, PR, SR, JR, DR, MR, SR, AR, LS, PS, MS, LS, MS, DS, MS, LT, MT, ST, LW, GW, MW, EW, SM, BF, JW, ML, MA, DS No competing interests declared

Importance: Systematic data on the association between anticancer therapies and thromboembolic events (TEEs) in patients with COVID-19 are lacking., Objective: To assess the association between anticancer therapy exposure within 3 months prior to COVID-19 and TEEs following COVID-19 diagnosis in patients with cancer., Design, Setting, and Participants: This registry-based retrospective cohort study included patients who were hospitalized and had active cancer and laboratory-confirmed SARS-CoV-2 infection. Data were accrued from March 2020 to December 2021 and analyzed from December 2021 to October 2022., Exposure: Treatments of interest (TOIs) (endocrine therapy, vascular endothelial growth factor inhibitors/tyrosine kinase inhibitors [VEGFis/TKIs], immunomodulators [IMiDs], immune checkpoint inhibitors [ICIs], chemotherapy) vs reference (no systemic therapy) in 3 months prior to COVID-19., Main Outcomes and Measures: Main outcomes were (1) venous thromboembolism (VTE) and (2) arterial thromboembolism (ATE). Secondary outcome was severity of COVID-19 (rates of intensive care unit admission, mechanical ventilation, 30-day all-cause mortality following TEEs in TOI vs reference group) at 30-day follow-up., Results: Of 4988 hospitalized patients with cancer (median [IQR] age, 69 [59-78] years; 2608 [52%] male), 1869 had received 1 or more TOIs. Incidence of VTE was higher in all TOI groups: endocrine therapy, 7%; VEGFis/TKIs, 10%; IMiDs, 8%; ICIs, 12%; and chemotherapy, 10%, compared with patients not receiving systemic therapies (6%). In multivariable log-binomial regression analyses, relative risk of VTE (adjusted risk ratio [aRR], 1.33; 95% CI, 1.04-1.69) but not ATE (aRR, 0.81; 95% CI, 0.56-1.16) was significantly higher in those exposed to all TOIs pooled together vs those with no exposure. Among individual drugs, ICIs were significantly associated with VTE (aRR, 1.45; 95% CI, 1.01-2.07). Also noted were significant associations between VTE and active and progressing cancer (aRR, 1.43; 95% CI, 1.01-2.03), history of VTE (aRR, 3.10; 95% CI, 2.38-4.04), and high-risk site of cancer (aRR, 1.42; 95% CI, 1.14-1.75). Black patients had a higher risk of TEEs (aRR, 1.24; 95% CI, 1.03-1.50) than White patients. Patients with TEEs had high intensive care unit admission (46%) and mechanical ventilation (31%) rates. Relative risk of death in patients with TEEs was higher in those exposed to TOIs vs not (aRR, 1.12; 95% CI, 0.91-1.38) and was significantly associated with poor performance status (aRR, 1.77; 95% CI, 1.30-2.40) and active/progressing cancer (aRR, 1.55; 95% CI, 1.13-2.13)., Conclusions and Relevance: In this cohort study, relative risk of developing VTE was high among patients receiving TOIs and varied by the type of therapy, underlying risk factors, and demographics, such as race and ethnicity. These findings highlight the need for close monitoring and perhaps personalized thromboprophylaxis to prevent morbidity and mortality associated with COVID-19-related thromboembolism in patients with cancer.

Introduction: COVID-19 particularly impacted patients with co-morbid conditions, including cancer. Patients with melanoma have not been specifically studied in large numbers. Here, we sought to identify factors that associated with COVID-19 severity among patients with melanoma, particularly assessing outcomes of patients on active targeted or immune therapy., Methods: Using the COVID-19 and Cancer Consortium (CCC19) registry, we identified 307 patients with melanoma diagnosed with COVID-19. We used multivariable models to assess demographic, cancer-related, and treatment-related factors associated with COVID-19 severity on a 6-level ordinal severity scale. We assessed whether treatment was associated with increased cardiac or pulmonary dysfunction among hospitalized patients and assessed mortality among patients with a history of melanoma compared with other cancer survivors., Results: Of 307 patients, 52 received immunotherapy (17%), and 32 targeted therapy (10%) in the previous 3 months. Using multivariable analyses, these treatments were not associated with COVID-19 severity (immunotherapy OR 0.51, 95% CI 0.19 - 1.39; targeted therapy OR 1.89, 95% CI 0.64 - 5.55). Among hospitalized patients, no signals of increased cardiac or pulmonary organ dysfunction, as measured by troponin, brain natriuretic peptide, and oxygenation were noted. Patients with a history of melanoma had similar 90-day mortality compared with other cancer survivors (OR 1.21, 95% CI 0.62 - 2.35)., Conclusions: Melanoma therapies did not appear to be associated with increased severity of COVID-19 or worsening organ dysfunction. Patients with history of melanoma had similar 90-day survival following COVID-19 compared with other cancer survivors., (© 2023. The Author(s).)

Importance: Cytokine storm due to COVID-19 can cause high morbidity and mortality and may be more common in patients with cancer treated with immunotherapy (IO) due to immune system activation., Objective: To determine the association of baseline immunosuppression and/or IO-based therapies with COVID-19 severity and cytokine storm in patients with cancer., Design, Setting, and Participants: This registry-based retrospective cohort study included 12 046 patients reported to the COVID-19 and Cancer Consortium (CCC19) registry from March 2020 to May 2022. The CCC19 registry is a centralized international multi-institutional registry of patients with COVID-19 with a current or past diagnosis of cancer. Records analyzed included patients with active or previous cancer who had a laboratory-confirmed infection with SARS-CoV-2 by polymerase chain reaction and/or serologic findings., Exposures: Immunosuppression due to therapy; systemic anticancer therapy (IO or non-IO)., Main Outcomes and Measures: The primary outcome was a 5-level ordinal scale of COVID-19 severity: no complications; hospitalized without requiring oxygen; hospitalized and required oxygen; intensive care unit admission and/or mechanical ventilation; death. The secondary outcome was the occurrence of cytokine storm., Results: The median age of the entire cohort was 65 years (interquartile range [IQR], 54-74) years and 6359 patients were female (52.8%) and 6598 (54.8%) were non-Hispanic White. A total of 599 (5.0%) patients received IO, whereas 4327 (35.9%) received non-IO systemic anticancer therapies, and 7120 (59.1%) did not receive any antineoplastic regimen within 3 months prior to COVID-19 diagnosis. Although no difference in COVID-19 severity and cytokine storm was found in the IO group compared with the untreated group in the total cohort (adjusted odds ratio [aOR], 0.80; 95% CI, 0.56-1.13, and aOR, 0.89; 95% CI, 0.41-1.93, respectively), patients with baseline immunosuppression treated with IO (vs untreated) had worse COVID-19 severity and cytokine storm (aOR, 3.33; 95% CI, 1.38-8.01, and aOR, 4.41; 95% CI, 1.71-11.38, respectively). Patients with immunosuppression receiving non-IO therapies (vs untreated) also had worse COVID-19 severity (aOR, 1.79; 95% CI, 1.36-2.35) and cytokine storm (aOR, 2.32; 95% CI, 1.42-3.79)., Conclusions and Relevance: This cohort study found that in patients with cancer and COVID-19, administration of systemic anticancer therapies, especially IO, in the context of baseline immunosuppression was associated with severe clinical outcomes and the development of cytokine storm., Trial Registration: ClinicalTrials.gov Identifier: NCT04354701.

Patients with B-lymphoid malignancies have been consistently identified as a population at high risk of severe COVID-19. Whether this is exclusively due to cancer-related deficits in humoral and cellular immunity, or whether risk of severe COVID-19 is increased by anticancer therapy, is uncertain. Using data derived from the COVID-19 and Cancer Consortium (CCC19), we show that patients treated for B-lymphoid malignancies have an increased risk of severe COVID-19 compared with control populations of patients with non-B-lymphoid malignancies. Among patients with B-lymphoid malignancies, those who received anticancer therapy within 12 months of COVID-19 diagnosis experienced increased COVID-19 severity compared with patients with non-recently treated B-lymphoid malignancies, after adjustment for cancer status and several other prognostic factors. Our findings suggest that patients recently treated for a B-lymphoid malignancy are at uniquely high risk for severe COVID-19., Significance: Our study suggests that recent therapy for a B-lymphoid malignancy is an independent risk factor for COVID-19 severity. These findings provide rationale to develop mitigation strategies targeted at the uniquely high-risk population of patients with recently treated B-lymphoid malignancies. This article is highlighted in the In This Issue feature, p. 171., (©2022 American Association for Cancer Research.)

Background: The frequency of coinfections and their association with outcomes have not been adequately studied among patients with cancer and coronavirus disease 2019 (COVID-19), a high-risk group for coinfection., Methods: We included adult (≥18 years) patients with active or prior hematologic or invasive solid malignancies and laboratory-confirmed severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) infection, using data from the COVID-19 and Cancer Consortium (CCC19, NCT04354701). We captured coinfections within ±2 weeks from diagnosis of COVID-19, identified factors cross-sectionally associated with risk of coinfection, and quantified the association of coinfections with 30-day mortality., Results: Among 8765 patients (hospitalized or not; median age, 65 years; 47.4% male), 16.6% developed coinfections: 12.1% bacterial, 2.1% viral, 0.9% fungal. An additional 6.4% only had clinical diagnosis of a coinfection. The adjusted risk of any coinfection was positively associated with age >50 years, male sex, cardiovascular, pulmonary, and renal comorbidities, diabetes, hematologic malignancy, multiple malignancies, Eastern Cooperative Oncology Group Performance Status, progressing cancer, recent cytotoxic chemotherapy, and baseline corticosteroids; the adjusted risk of superinfection was positively associated with tocilizumab administration. Among hospitalized patients, high neutrophil count and C-reactive protein were positively associated with bacterial coinfection risk, and high or low neutrophil count with fungal coinfection risk. Adjusted mortality rates were significantly higher among patients with bacterial (odds ratio [OR], 1.61; 95% CI, 1.33-1.95) and fungal (OR, 2.20; 95% CI, 1.28-3.76) coinfections., Conclusions: Viral and fungal coinfections are infrequent among patients with cancer and COVID-19, with the latter associated with very high mortality rates. Clinical and laboratory parameters can be used to guide early empiric antimicrobial therapy, which may improve clinical outcomes., (© The Author(s) 2022. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)

Hepatocellular carcinoma (HCC) is an aggressive cancer that typically develops in the setting of underlying cirrhosis of the liver. HCC commonly presents in advanced stages and if eligible orthotopic liver transplantation (OLT) and surgical resection/ablation remain as the only curative options. Prior to 2007, no systemic therapy was available that demonstrated an improvement in survival. Underlying cirrhosis and poor synthetic hepatic function provides a major challenge into effective systemic options contributing to the poor success of cytotoxic chemotherapy in HCC. The first drug to achieve clinical success was sorafenib despite the underwhelming overall survival of 3 months. Since then, other targeted therapies have shown modest benefit as well. Most recently, immunotherapy advances have come to the forefront in the management of HCC and combination therapy with immunotherapy and monoclonal antibodies have now surpassed sorafenib as first line treatment. This article will review the various approved and emerging therapies that have had a significant clinical impact and highlight the future directions and ongoing research that will hopefully translate into better outcomes in the treatment approach of advanced HCC., Competing Interests: Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://jgo.amegroups.com/article/view/10.21037/jgo-21-274/coif). DS reports institutional affiliations with Amgen, Apixigen, BMS, Fibrogen, Rafael, Oncomed, Merca, Roche with no personal fees and affiliations with Incyte and Genetech associated with personal fees. JA has no conflicts of interest to declare., (2022 Journal of Gastrointestinal Oncology. All rights reserved.)

Historically, cholera outbreaks have been linked to V. cholerae O1 serogroup strains or its derivatives of the O37 and O139 serogroups. A genomic study on the 2010 Haiti cholera outbreak strains highlighted the putative role of non O1/non-O139 V. cholerae in causing cholera and the lack of genomic sequences of such strains from around the world. Here we address these gaps by scanning a global collection of V. cholerae strains as a first step towards understanding the population genetic diversity and epidemic potential of non O1/non-O139 strains. Whole Genome Mapping (Optical Mapping) based bar coding produces a high resolution, ordered restriction map, depicting a complete view of the unique chromosomal architecture of an organism. To assess the genomic diversity of non-O1/non-O139 V. cholerae, we applied a Whole Genome Mapping strategy on a well-defined and geographically and temporally diverse strain collection, the Sakazaki serogroup type strains. Whole Genome Map data on 91 of the 206 serogroup type strains support the hypothesis that V. cholerae has an unprecedented genetic and genomic structural diversity. Interestingly, we discovered chromosomal fusions in two unusual strains that possess a single chromosome instead of the two chromosomes usually found in V. cholerae. We also found pervasive chromosomal rearrangements such as duplications and indels in many strains. The majority of Vibrio genome sequences currently in public databases are unfinished draft sequences. The Whole Genome Mapping approach presented here enables rapid screening of large strain collections to capture genomic complexities that would not have been otherwise revealed by unfinished draft genome sequencing and thus aids in assembling and finishing draft sequences of complex genomes. Furthermore, Whole Genome Mapping allows for prediction of novel V. cholerae non-O1/non-O139 strains that may have the potential to cause future cholera outbreaks.

We present draft genome sequences of 15 clinical Vibrio isolates of various serogroups. These are valuable data for use in studying Vibrio cholerae genetic diversity, epidemic potential, and strain attribution., (Copyright © 2014 Bishop-Lilly et al.)

In May of 2011, an enteroaggregative Escherichia coli O104:H4 strain that had acquired a Shiga toxin 2-converting phage caused a large outbreak of bloody diarrhea in Europe which was notable for its high prevalence of hemolytic uremic syndrome cases. Several studies have described the genomic inventory and phylogenies of strains associated with the outbreak and a collection of historical E. coli O104:H4 isolates using draft genome assemblies. We present the complete, closed genome sequences of an isolate from the 2011 outbreak (2011C-3493) and two isolates from cases of bloody diarrhea that occurred in the Republic of Georgia in 2009 (2009EL-2050 and 2009EL-2071). Comparative genome analysis indicates that, while the Georgian strains are the nearest neighbors to the 2011 outbreak isolates sequenced to date, structural and nucleotide-level differences are evident in the Stx2 phage genomes, the mer/tet antibiotic resistance island, and in the prophage and plasmid profiles of the strains, including a previously undescribed plasmid with homology to the pMT virulence plasmid of Yersinia pestis. In addition, multiphenotype analysis showed that 2009EL-2071 possessed higher resistance to polymyxin and membrane-disrupting agents. Finally, we show evidence by electron microscopy of the presence of a common phage morphotype among the European and Georgian strains and a second phage morphotype among the Georgian strains. The presence of at least two stx2 phage genotypes in host genetic backgrounds that may derive from a recent common ancestor of the 2011 outbreak isolates indicates that the emergence of stx2 phage-containing E. coli O104:H4 strains probably occurred more than once, or that the current outbreak isolates may be the result of a recent transfer of a new stx2 phage element into a pre-existing stx2-positive genetic background.