Improved Pathologic response to chemoradiation in MGMT methylated locally advanced rectal cancer.

Background and Purpose: With the growing interest in total neoadjuvant treatment for locally advanced rectal adenocarcinoma (LARC) there is an urgent unmet need to identify predictive markers of response to long-course neoadjuvant concurrent chemoradiotherapy (LCRT). O6-Methylguanine (O6-MG)-DNA-methyltransferase (MGMT) gene methylation has been associated in some malignancies with response to concurrent chemoradiotherapy. We attempted to find if pathologic response to LCRT was associated with MGMT promoter hypermethylation (MGMTh). Materials and Methods: Patients were identified with LARC, available pre-treatment biopsy specimens, and at least 1 year of follow-up who received LCRT followed by surgical resection within 6 months. Biopsies were tested for MGMTh using a Qiagen pyrosequencing kit (Catalog number 970061). The primary outcome of LCRT responsiveness was based on tumor regression grade (TRG), with grades of 0-1 considered to have excellent response and grades of 2-3 considered to be non-responders. Secondary outcomes included overall survival (OS) and recurrence free survival (RFS). Results: Of 96 patients who met inclusion criteria, 76 had samples which produced reliable assay results. MGMTh corresponded with higher grade and age of the biopsy specimen. The percentage of responders to LCRT was higher amongst the MGMTh patients than the MGMTn patients (60.0% vs 27.5%, p value = 0.0061). MGMTh was not significantly associated with improved OS (2-year OS of 96.0% vs 98.0%, p = 0.8102) but there was a trend for improved RFS (2-year RFS of 87.6% vs 74.2%, p = 0.0903). Conclusion: Significantly greater tumor regression following LCRT was seen in MGMTh LARC. Methylation status may help identify good candidates for close observation without surgery following LCRT.

Neoadjuvant versus definitive chemoradiation in locally advanced esophageal cancer for patients of advanced age or significant comorbidities.

The addition of surgery to chemoradiation for esophageal cancer has not shown a survival benefit in randomized trials. Patients with more comorbidities or advanced age are more likely to be given definitive chemoradiation due to surgical risk. We aimed to identify subsets of patients in whom the addition of surgery to chemoradiation does not provide an overall survival (OS) benefit. The National Cancer Database was queried for patients with locally advanced esophageal cancer who received either definitive chemoradiation or neoadjuvant chemoradiation followed by surgery. Bivariate analysis was used to assess the association between patient characteristics and treatment groups. Log-rank tests and Cox proportional hazards models were performed to assess for differences in survival. A total of 15,090 with adenocarcinoma and 5,356 with squamous cell carcinoma met the inclusion criteria. Patients treated with neoadjuvant chemoradiation and surgery had significantly improved survival by Cox proportional hazards model regardless of histology if <50, 50-60, 61-70, or 71-80 years old. There was no significant benefit or detriment in patients 81-90 years old. Survival advantage was also significant with a Charlson/Deyo comorbidity condition score of 0, 1, 2, and ≥3 in adenocarcinoma squamous cell carcinoma with scores of 2 or ≥3 had no significant benefit or detriment. Patients 81-90 years old or with squamous cell carcinoma and a Charlson/Deyo comorbidity score ≥ 2 lacked an OS benefit from neoadjuvant chemoradiation followed by surgery compared with definitive chemoradiation. Careful consideration of esophagectomy-specific surgical risks should be used when recommending treatment for these patients.

The cost of elective nodal coverage in prostate cancer: Late quality of life outcomes and dosimetric analysis with 0, 45 or 54 Gy to the pelvis.

Purpose: Elective pelvic lymph node radiotherapy (PLNRT) in prostate cancer is often omitted from definitive (n = 267) and post prostatectomy (n = 160) radiotherapy (RT) due to concerns regarding toxicity and efficacy. Data comparing patient-reported outcome measures (PROMs) with or without PLNRT is limited. Our long-term supposition is that PLNRT, particularly to higher doses afforded by IMRT, will decrease pelvic failure rate in select patients. We aim to establish the impact of two different PLNRT doses on long term quality of life (QOL). Methods and materials: Prostate cancer patients (n = 428) recorded baseline scores using the Expanded Prostate Cancer Index Composite (EPIC), prior to definitive or post-prostatectomy RT. PLNRT, if given, was prescribed to 45 or 54 Gy at 1.8 Gy per fraction. New EPIC scores were recorded 20-36 months after radiotherapy. Absolute change in each domain subscale and summary score was recorded, along with if these changes met minimally important difference (MID) criteria. A separate multivariate analysis (MVA) was performed for each measure. Subsequent dosimetric analysis was performed. Results: Frequency of a MID decline was significantly greater with PLNRT to 54 Gy for urinary function, incontinence, and overall. No urinary decline was correlated with PLNRT to 45 Gy. PLNRT to 54 Gy was significant for decline in urinary function, bother, irritative, incontinence, and overall score in one or both MVA models while 45 Gy was not. Postoperative status was significant for decline in urinary function, incontinence, and overall. Amongst postoperative patients, there was significantly greater decline in urinary function score in the salvage setting. Neither 54 nor 45 Gy significantly affected bowel subscale or overall score decline. Conclusions: Using conventional fractionation, adding PLNRT to 54 Gy, but not 45 Gy, correlates with worse urinary QOL, with postoperative patients experiencing a steeper decline. PLNRT had no significant impact on bowel QOL with either dose.

The Effect of High-Dose Radiation Therapy on Healthy Vertebral Bone Density.

Objective Increased rates of insufficiency fractures are reported after radiation therapy without well-defined causality. Here, we conduct a cross-sectional study on the density change of a non-lesioned vertebral bone after irradiation relative to a control bone in patients with spinal metastases. Methods Patients were identified who received radiation therapy for spinal metastases to a region, including an adjacent vertebra without identifiable malignancy on pre-treatment CT. Every patient had an untreated vertebra of a similar type available as a control. A Hounsfield-density calibration curve was used to measure the vertebral body density before and after treatment. Analysis of covariance was used to model vertebral bone density changes with respect to treatment status. Significance was established as p < 0.05. Results We identified 36 patients who fit the study criteria. The irradiated healthy bone received a median dose of 30 Gy. The median biologically effective dose (BED) was 60 Gy (α/ß = 3) and 39 Gy (α/ß = 10). Median follow-up imaging intervals between pre-treatment and follow-up CT scans was 13.4 months. Levene's test was used to confirm the equality of error variance assumption of ANCOVA (p = 0.093). The mean change in the density of the irradiated vertebral bone was -3.59% (95% CI = -8.51% - 1.32%, p = 0.149). Conclusions We found no significant change in vertebral bone density attributable to radiation treatment. Further work is needed to elucidate if increased fracture rates after radiation are due to factors other than bone density.

C-Reactive Protein Is a Poor Marker of Baseline Inflammation in Prostate Cancer and Response to Radiotherapy or Androgen Ablation.

Introduction C-reactive protein (CRP) is an acute-phase reactant used as a general marker for inflammation. Isolated levels have been associated with prostate cancer development, prostate-specific antigen (PSA), Gleason score, and treatment response. We seek to establish whether CRP levels reflect inflammation caused by prostate cancer by comparing levels at various points of time before, during, and after therapy. Materials and methods A total of 209 patients had a complete blood count (CBC), PSA, and CRP taken at up to four different time points. Labs were performed up to one week prior to androgen ablation via leuprolide injection (pre-AA), up to one week prior to radiotherapy (RT) (pre-RT), within one week of RT completion (post-RT), and three months following RT completion (FU [follow-up]). Results Significant relationships were found between CRP and WBC pre-AA (p-value=0.0050), pre-RT (p-value=0.0170), and post-RT (p-value=0.0113), but not at FU (p=.096). CRP had no significant relationship with PSA or lymphocytes at any time points. PSA was significantly affected by androgen ablation but lymphocytes, WBCs, and CRP were not. No CRP levels were associated with risk groups or FU-PSA. Lymphatic radiation fields significantly decreased WBCs and lymphocytes but not CRP. PSA, WBC, and lymphocytes all significantly decreased from pre-RT to post-RT, followed by a significant recovery. CRP did not significantly change during any of these periods and was not significantly related to changes in PSA, WBCs, or lymphocytes. Conclusion CRP is not a sensitive marker of the acute inflammatory effects of non-metastatic prostate cancer and treatment response with androgen ablation or radiation therapy.

Bone Density Changes Following Radiotherapy to Vertebral Metastases.

Introduction Patients have increasing longevity and time for bone healing following radiotherapy (RT) for treatment of bone metastases (BM). Attempts to assess the treatment response of bone metastases have been either limited or heavily subjective. Our goal was to try to quantitate cancer-involved bone changes after RT using changes in bone mineral density (BMD) from computer tomographic (CT) imaging. Methods Retrospectively, 117 spinal metastases were identified that received RT with follow-up CT scans >9 months following CT simulation. Contoured volumes included: the metastasis (gross tumor volume; GTV); the involved vertebra (gross bone volume; GBV); a total lytic volume (Lyt); a dominant lytic volume (Domlyt); a control volume, and the nearest uninvolved, unirradiated vertebra (control bone volume; CBV). The Hounsfield-density calibration curve was used to measure the density of these volumes before and after treatment. Results Whether using raw or control-adjusted changes, the absolute and percent change in density of the GBV, GTV, Lyt, and Domlyt volumes all significantly increased (each p<0.0001). The increase in the density of Domlyt volumes was greater than that of Lyt volumes (p=0.0465), which were greater than GTV (p=0.0065), which were greater than GBV (p<0.0001). On multivariate analysis, only the biologically effective dose (BED) dose significantly correlated with GTV density change (p=0.0175). K means clustering created groups by initial lesion size, GTV, or GBV density. A significant difference in GTV density change was not detected between any groups. Conclusion Increases in BMD are associated with healing regardless of lesion size or initial density. A prospective study to determine whether long-term control is related to early density measurements is needed.

Vaginal cuff brachytherapy: do we need to treat to more than a two-centimeter active length?

PURPOSE: American Brachytherapy Society (ABS) guidelines recommend using a 3-5 cm active length (AL) when treating vaginal cuff (VC) in adjuvant setting of endometrial cancer (EC). The purpose of this study was to evaluate local control and toxicity, using an AL of 1 or 2 cm and immobilization with a traditional table-mounted (stand) or patient-mounted (suspenders) device. MATERIAL AND METHODS: Between 2005 and 2019, 247 patients with EC were treated with adjuvant high-dose-rate vaginal cuff (HDR-VC) brachytherapy with or without external beam radiation (EBRT). Treatment was prescribed to a 0.5 cm depth, with an AL of 1 or 2 cm, using stand or suspenders. VC boost after EBRT was typically administered with 2 fractions of 5.5 Gy, while VC brachytherapy alone was typically applied with 3 fractions of 7 Gy or 5 fractions of 5.5 Gy. RESULTS: The combination of suspender immobilization and an AL of 2 cm (n = 126, 51%) resulted in 5-year local control of 100%. An AL of 2 cm compared to 1 cm correlated with better local control (99.1% vs. 88.5%, p = 0.0479). Regarding immobilization, suspenders correlated with improved local control compared to stand (100% vs. 86.7%, p = 0.0038). Immobilization technique was significantly correlated with AL (p < 0.0001). Only 5 (2.0%) patients experienced grade ≥ 3 toxicity, all of whom received EBRT. CONCLUSIONS: In the present series, an AL of 2 cm provided excellent local control, while 1 cm was inadequate. Suspender immobilization was a practical alternative to stand immobilization in HDR brachytherapy of the vaginal cuff.

Improved local control in p16 negative oropharyngeal cancers with hypermethylated MGMT.

INTRODUCTION: Patients with oropharyngeal cancers that are p16 negative (p16-) have worse outcomes than those who are p16 positive (p16+) and there is an unmet need for prognostic markers in this population. O6-Methylguanine (O6-MG)-DNA-methyltransferase (MGMT) gene methylation has been associated with response to chemoradiotherapy (CRT) in glioblastoma. We sought to find if MGMT promoter methylation was associated with outcomes of locally advanced oropharyngeal and oral cavity squamous cell carcinoma (OOSCC) in patients treated with definitive concurrent CRT. METHODS: Patients were identified with primary OOSCC, known p16 status, retrievable pre-treatment biopsies, and at least 6 months of follow-up who received definitive concurrent CRT from 2004 to 2015. Biopsies were tested for MGMT hypermethylation (MGMT+) using a Qiagen pyrosequencing kit (Catalog number 970061). Outcomes were subsequently recorded and analyzed. RESULTS: Fifty-eight patients were included with a median follow up of 78 (range 6-196) months. Fourteen patients (24.1%) had oral cavity cancer and 44 (75.9%) had oropharyngeal cancer. A significant difference was found for local recurrence free survival (LRFS) by combined MGMT and p16 status (p = 0.0004). Frequency of LR in MGMT+/p16+, MGMT+/p16-, MGMT-/p16+, and MGMT-p16- patients was 14.3%, 14.3%, 13.0%, and 69.2%, respectively (p = 0.0019). A significant difference was not found for distant recurrence free survival (p = 0.6165) or overall survival (p = 0.1615). LRFS remained significant on analysis restricted to oropharyngeal cancer patients (p-value = 0.0038). CONCLUSION: Patients who are p16- and MGMT+ with oropharyngeal and oral cavity squamous cell carcinoma have significantly better LC with definitive CRT than those who are p16- and MGMT-. Prospective studies are needed to verify these findings.

Use of three pins in Gamma Knife stereotactic radiosurgery for brain metastases.

PURPOSE: We present our institutional experience in treating brain metastases with GK-SRS and a headframe fixed to the skull with only 3 pins to avoid collisions between the headframe and the Gamma Knife (GK) machine. METHODS AND MATERIALS: Among 3500 consecutive patients who received GK-SRS in 2011-2017, 50 had 1 of the 2 anterior pins removed immediately before treatment of ≥1 brain lesion. Endpoints were local control, dosimetric parameters, and toxicity. RESULTS: Median follow-up time for the 49 patients with follow-up was 7.0 months (range 0.2-57.0). Median number of lesions treated per session was 6 (range 1-18); a median 1 lesion was treated with 3-pin fixation (range 1-2) and a median 5 lesions treated with 4-pin fixation (range 0-17) during the same session. Lesions treated with 3-pin fixation were in the occipital lobe (n=41), cerebellum (n=9), or temporal lobe (n=1). No local failures were noted. The sole grade 2 toxicity (partial seizure) was attributed to treatment of a 4-pin-fixed lesion. Except for gradient index, dosimetry did not vary for lesions treated with 3-pin versus 4-pin fixation. CONCLUSIONS: Treating brain metastases with 3-pin fixation did not compromise treatment outcome and is a good option for posterior brain metastases that cannot otherwise be treated with 4-pin GK-SRS.

Radiotherapy in Patients with Mycosis Fungoides and Central Nervous System Involvement.

BACKGROUND: Involvement of the central nervous system (CNS) by mycosis fungoides (MF) is rare; however, it portends a poor prognosis. While aggressive multimodality therapy may improve outcomes, the role of radiation therapy (RT) is not well defined. OBJECTIVES: We sought to explore the efficacy of RT in the management of CNS involvement by MF. METHOD: We retrospectively identified five patients with MF and CNS involvement who received cranial or craniospinal RT at a single institution. Patient characteristics, disease features, radiographic findings, treatments delivered, and outcome data were extracted from the electronic medical record. RESULTS: All 5 patients had neurologic deficits at RT initiation, and 4 experienced at least a partial improvement. Of 4 patients evaluated by MRI after RT completion, 3 had complete resolution of CNS disease within the irradiated field. At the time of last follow-up, all patients had died of MF. The median time to death was 7.4 months (range 1.0-21 months) from their diagnosis with CNS involvement and 1.2 months (range 0.4-7.1 months) from the end of RT treatment. CONCLUSIONS: We observed high rates of radiographic response and palliation of neurological symptoms. Nonetheless, all patients succumbed to their disease shortly after treatment, confirming the poor prognosis of this condition. Our findings suggest that RT may play a valuable palliative role for these patients.

Genome Sequences of Nine Erwinia amylovora Bacteriophages.

Erwinia amylovora is a plant pathogen belonging to the Enterobacteriaceae family, a family containing many plant and animal pathogens. Herein, we announce nine genome sequences of E. amylovora bacteriophages isolated from infected apple trees along the Wasatch Front in Utah.

Prognostic value of combining a quantitative image feature from positron emission tomography with clinical factors in oligometastatic non-small cell lung cancer.

BACKGROUND AND PURPOSE: Oligometastatic non-small cell lung cancer (NSCLC) is a heterogeneous condition with few known risk stratification factors. A quantitative imaging feature (QIF) on positron emission tomography (PET), gray-level co-occurrence matrix energy, has been linked with outcome of nonmetastatic NSCLC. We hypothesized that GLCM energy would enhance the ability of models comprising standard clinical prognostic factors (CPFs) to stratify oligometastatic patients based on overall survival (OS). MATERIALS AND METHODS: We assessed 79 patients with oligometastatic NSCLC (≤3 metastases) diagnosed in 2007-2015. The primary and largest metastases at diagnosis were delineated on pretreatment scans with GLCM energy extracted using imaging biomarker explorer (IBEX) software. Iterative stepwise elimination feature selection based on the Akaike information criterion identified the optimal model comprising CPFs for predicting OS in a multivariate Cox proportional hazards model. GLCM energy was tested for improving prediction accuracy. RESULTS: Energy was a significant predictor of OS (P = 0.028) in addition to the selected CPFs. The c-indexes for the CPF-only and CPF + Energy models were 0.720 and 0.739. CONCLUSIONS: Incorporating Energy strengthened a CPF model for predicting OS. These findings support further exploration of QIFs, including markers of the primary tumor vs. those of the metastatic sites.

Genome Sequences of 19 Novel Erwinia amylovora Bacteriophages.

Erwinia amylovora is the causal agent of fire blight, a devastating disease affecting some plants of the Rosaceae family. We isolated bacteriophages from samples collected from infected apple and pear trees along the Wasatch Front in Utah. We announce 19 high-quality complete genome sequences of E. amylovora bacteriophages.

Patterns of metastatic progression after definitive radiation therapy for early-stage and locally advanced non-small cell lung cancer.

Current preclinical models of metastatic disease (particularly oligometastases) suggest that metastases appear in a hierarchical order. We attempted to identify systematic patterns of metastasis in non-small cell lung cancer (NSCLC) after radiation therapy (XRT). We analyzed 1074 patients treated from 12/21/1998 through 8/20/2012 with ≥60 Gy definitive radiation for initially non-metastatic NSCLC. Location and time of metastases were recorded. Regional nodal failure was noted, as was subsequent distal failure. For further analysis, we considered only the five most common sites of metastasis (bone, brain, liver, adrenal, and lung). Metastatic progression over time was defined and patterns elucidated with Chi square tests. Histologic findings were analyzed with Wilcoxon rank sum tests. A significant multistep linear progression was not apparent. Having a first metastasis in lung or bone was associated with respective 16% (median 2.4 months) and 15% likelihoods (median 7.9 months) of secondary brain metastasis. Initial metastasis in the brain led to metastasis in another organ 29.3% of the time, most often in the lung, bone, and liver (medians 3.6, 7.9, and 3.1 months). Adenocarcinoma was more likely than squamous to metastasize to the brain (18 vs. 9%) and any of the five major sites (41 vs. 27%). We did not appreciate dominant patterns suggesting a multi-step hierarchical order of metastasis. Rather, our findings suggest that certain subgroups may develop different patterns of spread depending on a variety of factors.

Prognostic impact of leukocyte counts before and during radiotherapy for oropharyngeal cancer.

INTRODUCTION: Peripheral blood count components are accessible and evidently predictive in other cancers but have not been explored in oropharyngeal carcinoma. We examine if there is an association between the use of intensity-modulated radiotherapy (IMRT) or intensity-modulated proton therapy (IMPT) and lymphopenia, as well as if there is an association between baseline neutrophilia, baseline leukocytosis and lymphocyte nadir in oropharyngeal cancer. MATERIALS AND METHODS: Analysis started with 150 patients from a previous case to case study design, which retrospectively identified adults with oropharyngeal carcinoma, 100 treated with IMRT in 2010-2012 and 50 treated with IMPT in 2011-2014. Pretreatment leukocyte, neutrophil, lymphocyte, and hemoglobin levels were extracted, as were neutrophil and lymphocyte nadir levels during radiotherapy. We retained 137 patients with recorded pre-treatment leukocyte and neutrophil levels for associated analysis and 114 patients with recorded lymphocyte levels during radiation and associated analysis. Multivariate survival analyses were done with Cox regression. RESULTS: The radiotherapy type (IMRT vs. IMPT) was not associated with lymphopenia (grade 3 P > .99; grade 4 P = .55). In univariate analyses, poor overall survival was associated with pretreatment neutrophilia (hazard ratio [HR] 5.58, 95% confidence interval [CI] 1.99-15.7, P = .001), pretreatment leukocytosis (HR 4.85, 95% CI 1.73-13.6, P = .003), grade 4 lymphopenia during radiotherapy (HR 3.28, 95% CI 1.14-9.44, P = .03), and possibly smoking status >10 pack-years (HR 2.88, 95% CI 1.01-8.18, P = .05), but only T status was possibly significant in multivariate analysis (HR 2.64, 95% CI 0.99-7.00, P = .05). Poor progression-free survival was associated with pretreatment leukocytosis and T status in univariate analysis, and pretreatment neutrophilia and advanced age on multivariate analysis. CONCLUSIONS: Treatment modality did not affect blood counts during radiotherapy. Pretreatment neutrophilia, pretreatment leukocytosis, and grade 4 lymphopenia during radiotherapy were associated with worse outcomes after, but establishing causality will require additional work with increased statistical power.

Radiotherapy-Induced Malfunction in Contemporary Cardiovascular Implantable Electronic Devices: Clinical Incidence and Predictors.

IMPORTANCE: Risk stratification and management paradigms for patients with cardiovascular implantable electronic devices (CIEDs) requiring radiotherapy (RT) vary widely and are based on limited clinical data. OBJECTIVE: To identify the incidence and predictors of CIED malfunction and describe associated clinical consequences in a large cohort of patients treated with photon- and electron-based RT. DESIGN, SETTING, AND PARTICIPANTS: Retrospective analysis of all patients with a functioning CIED who underwent RT between August 2005 and January 2014 with CIED interrogation data following RT at an academic cancer center. We identified 249 courses of photon- and electron-based RT in 215 patients (123 pacemakers [57%]; 92 implantable cardioverter-defibrillators [43%]). Substantial neutron production was generated in 71 courses (29%). EXPOSURE: Implantation of CIED with subsequent therapeutic radiation treatment (neutron producing with 15- or 18-MV photons and non-neutron producing with electrons, GammaKnife, or 6-MV photons). MAIN OUTCOMES AND MEASURES: Malfunction of CIED, characterized as single-event upset (data loss, parameter resets, unrecoverable resets), and delayed effects including signal interference, pacing threshold changes, and premature battery depletion. RESULTS: Malfunction of CIED attributable to RT occurred during 18 courses (7%), with 15 CIEDs experiencing single-event upsets, and 3, transient signal interference. All single-event upsets occurred during neutron-producing RT, at a rate of 21%, 10%, and 34% per neutron-producing course for CIEDs, pacemakers, and implantable cardioverter-defibrillators, respectively. No single-event upsets were found among 178 courses of non-neutron-producing RT. Incident CIED dose did not correlate with device malfunction. Patients treated to the abdomen and pelvis region were more likely to undergo a single-event upset (hazard ratio, 5.2 [95% CI, 1.2-22.6]; P = .03). Six patients with a CIED parameter reset developed clinical symptoms: 3 experienced hypotension and/or bradycardia, 2 experienced abnormal chest ticking consistent with pacemaker syndrome, and 1 developed congestive heart failure. The 3 episodes of signal interference did not result in clinical effects. No delayed malfunctions were directly attributed to RT. CONCLUSIONS AND RELEVANCE: In a cohort of contemporary CIEDs, all cases of single-event upset malfunction occurred in the setting of notable neutron production, at a rate of 21% for neutron-producing RT and 0% for non-neutron-producing RT. Where clinically feasible, the use of non-neutron-producing RT is recommended. Given the lack of correlation between CIED malfunction and incident dose observed up to 5.4 Gy, invasive CIED relocation procedures in these settings can be minimized.

Correction: genomic comparison of 93 Bacillus phages reveals 12 clusters, 14 singletons and remarkable diversity.

BACKGROUND: The Bacillus genus of Firmicutes bacteria is ubiquitous in nature and includes one of the best characterized model organisms, B. subtilis, as well as medically significant human pathogens, the most notorious being B. anthracis and B. cereus. As the most abundant living entities on the planet, bacteriophages are known to heavily influence the ecology and evolution of their hosts, including providing virulence factors. Thus, the identification and analysis of Bacillus phages is critical to understanding the evolution of Bacillus species, including pathogenic strains. RESULTS: Whole genome nucleotide and proteome comparison of the 83 extant, fully sequenced Bacillus phages revealed 10 distinct clusters, 24 subclusters and 15 singleton phages. Host analysis of these clusters supports host boundaries at the subcluster level and suggests phages as vectors for genetic transfer within the Bacillus cereus group, with B. anthracis as a distant member. Analysis of the proteins conserved among these phages reveals enormous diversity and the uncharacterized nature of these phages, with a total of 4,442 protein families (phams) of which only 894 (20%) had a predicted function. In addition, 2,583 (58%) of phams were orphams (phams containing a single member). The most populated phams were those encoding proteins involved in DNA metabolism, virion structure and assembly, cell lysis, or host function. These included several genes that may contribute to the pathogenicity of Bacillus strains. CONCLUSIONS: This analysis provides a basis for understanding and characterizing Bacillus and other related phages as well as their contributions to the evolution and pathogenicity of Bacillus cereus group bacteria. The presence of sparsely populated clusters, the high ratio of singletons to clusters, and the large number of uncharacterized, conserved proteins confirms the need for more Bacillus phage isolation in order to understand the full extent of their diversity as well as their impact on host evolution.

Genomic comparison of 93 Bacillus phages reveals 12 clusters, 14 singletons and remarkable diversity.

BACKGROUND: The Bacillus genus of Firmicutes bacteria is ubiquitous in nature and includes one of the best characterized model organisms, B. subtilis, as well as medically significant human pathogens, the most notorious being B. anthracis and B. cereus. As the most abundant living entities on the planet, bacteriophages are known to heavily influence the ecology and evolution of their hosts, including providing virulence factors. Thus, the identification and analysis of Bacillus phages is critical to understanding the evolution of Bacillus species, including pathogenic strains. RESULTS: Whole genome nucleotide and proteome comparison of the 93 extant Bacillus phages revealed 12 distinct clusters, 28 subclusters and 14 singleton phages. Host analysis of these clusters supports host boundaries at the subcluster level and suggests phages as vectors for genetic transfer within the Bacillus cereus group, with B. anthracis as a distant member of the group. Analysis of the proteins conserved among these phages reveals enormous diversity and the uncharacterized nature of these phages, with a total of 4,922 protein families (phams) of which only 951 (19%) had a predicted function. In addition, 3,058 (62%) of phams were orphams (phams containing a gene product from a single phage). The most populated phams were those encoding proteins involved in DNA metabolism, virion structure and assembly, cell lysis, or host function. These included several genes that may contribute to the pathogenicity of Bacillus strains. CONCLUSIONS: This analysis provides a basis for understanding and characterizing Bacillus phages and other related phages as well as their contributions to the evolution and pathogenicity of Bacillus cereus group bacteria. The presence of sparsely populated clusters, the high ratio of singletons to clusters, and the large number of uncharacterized, conserved proteins confirms the need for more Bacillus phage isolation in order to understand the full extent of their diversity as well as their impact on host evolution.