BHLHE40 drives protective polyfunctional CD4 T cell differentiation in the female reproductive tract against Chlamydia.

The protein basic helix-loop-helix family member e40 (BHLHE40) is a transcription factor recently emerged as a key regulator of host immunity to infections, autoimmune diseases and cancer. In this study, we investigated the role of Bhlhe40 in protective T cell responses to the intracellular bacterium Chlamydia in the female reproductive tract (FRT). Mice deficient in Bhlhe40 exhibited severe defects in their ability to control Chlamydia muridarum shedding from the FRT. The heightened bacterial burdens in Bhlhe40-/- mice correlated with a marked increase in IL-10-producing T regulatory type 1 (Tr1) cells and decreased polyfunctional CD4 T cells co-producing IFN-γ, IL-17A and GM-CSF. Genetic ablation of IL-10 or functional blockade of IL-10R increased CD4 T cell polyfunctionality and partially rescued the defects in bacterial control in Bhlhe40-/- mice. Using single-cell RNA sequencing coupled with TCR profiling, we detected a significant enrichment of stem-like T cell signatures in Bhlhe40-deficient CD4 T cells, whereas WT CD4 T cells were further down on the differentiation trajectory with distinct effector functions beyond IFN-γ production by Th1 cells. Altogether, we identified Bhlhe40 as a key molecular driver of CD4 T cell differentiation and polyfunctional responses in the FRT against Chlamydia.

IFNγ and Antibody Synergize To Enhance Protective Immunity against Chlamydia Dissemination and Female Reproductive Tract Reinfections.

CD4 T cell-dependent IFNγ production and antibody are the two best known effectors for protective immunity against Chlamydia female reproductive tract (FRT) infection. Nevertheless, mice lacking either IFNγ or B cells can clear the vast majority of Chlamydia from the FRT, while suffering from varying degrees of disseminated infection. In this study, we investigated whether IFNγ and B cells play complementary roles in host defense against Chlamydia and evaluated their relative contributions in systemic and mucosal tissues. Using mice deficient in both IFNγ and B cells (IFNγ-/- x µMT), we showed that mice lacking both effectors were highly susceptible to lethal systemic bacterial dissemination following Chlamydia muridarum intravaginal infection. Passive transfer of immune convalescent serum, but not recombinant IFNγ, reduced bacterial burden in both systemic and mucosal tissues in IFNγ-/- x µMT mice. Notably, over the course of primary infection, we observed a reduction of bacterial shedding of more than 2 orders of magnitude in IFNγ-/- x µMT mice following both C. muridarum and C. trachomatis FRT infections. In contrast, no protective immunity against C. muridarum reinfection was detected in the absence of IFNγ and B cells. Together, our results suggest that IFNγ and B cells synergize to combat systemic Chlamydia dissemination, while additional IFNγ and B cell-independent mechanisms exist for host resistance to Chlamydia in the lower FRT.

Novel viral RNA genomes of the vine mealybug Planococcus ficus.

The vine mealybug, Planococcus ficus (Signoret, 1875), is the most important insect pest in growing areas of the grapevine Vitis vinifera L. in several countries, including Mexico. In Mexico, Baja California (B.C.) is the region with the highest production of V. vinifera L. grapes for industrial purposes. Recently, the diversity of viruses infecting insects only (insect-specific viruses) has been broadly explored to elucidate further ecological viral-host interactions in many insect species, which in some cases has resulted in the application of virus-based biological control agents for insect pests. However, a survey of the Pl. ficus virome has not been done yet. In the present study, we pooled Pl. ficus individuals collected through different vineyards of Ensenada, B.C., Mexico and analysed them by meta-transcriptomics. Novel nearly complete genomes of five RNA viruses were retrieved. These viruses were related to the Iflaviridae and Reoviridae families, and to the Picornavirales and Tolivirales orders. A new isolate belonging to the Dicistroviridae family was also found. Phylogenetic analyses showed that these putative viral genomes group with viruses having hemipteran (including a mealybug species) or other insect hosts, or with viruses associated with insects. Our results suggest that the identified novel RNA viruses could be insect-specific viruses of Pl. ficus. This work is the first insight into the Pl. ficus virome; it guarantees further studies aimed to characterize those viruses with potential for application in biological control of this economically important insect.

Liver Transplantation as Definitive Treatment of Post-cholecystectomy Bile Duct Injury: Experience in a High-volume Repair Center.

OBJECTIVE: To analyze the perioperative and long-term outcomes of patients undergoing LT due to BDI in a tertiary care center. BACKGROUND: BDI is associated with significant morbidity and long-term impact on quality of life. LT represents the only possibility of a cure in patients with BDI who develop SBC. METHODS: Retrospective cohort study from a prospective LT database. Between 2008 and 2019, patients with SBC due to BDI after cholecystectomy and requiring LT were identified. Perioperative and long-term outcomes were analyzed. RESULTS: Among 354 LT, 12 patients underwent LT to treat post-cholecystectomy BDI and accounted for 3.4% of all LT. The median time from BDI to SBC diagnosis was 9.3 years (2.4-14). The mean time from SBC to inclusion on the waitlist was 2.4years (± 2.2). Postoperative complications occurred in 11 patients (91.6%); mainly infectious (9/12 patients, 75%), followed by renal complications (4/12 patients, 33.3%). Only 2 patients developed major complications, which were the patients who died, resulting in a 90-day mortality of 16.7%. After a mean follow-up of 40.3 months (± 42.2) survival at 1, 3, and 5 years was 83%. CONCLUSIONS: Although BDI is an unusual indication for LT worldwide, it accounted for 3.4% of all LT in our center. Although postoperative mortality remains high, LT is the only possibility of a cure, with acceptable long-term outcomes. Early referral to a tertiary care center is essential to avoid long-term complications of BDI, such as SBC.

Innate IFN-γ Is Essential for Systemic Chlamydia muridarum Control in Mice, While CD4 T Cell-Dependent IFN-γ Production Is Highly Redundant in the Female Reproductive Tract.

Protective immunity against the obligate intracellular bacterium Chlamydia has long been thought to rely on CD4 T cell-dependent gamma interferon (IFN-γ) production. Nevertheless, whether IFN-γ is produced by other cellular sources during Chlamydia infection and how CD4 T cell-dependent and -independent IFN-γ contribute differently to host resistance have not been carefully evaluated. In this study, we dissected the requirements of IFN-γ produced by innate immune cells and CD4 T cells for resolution of Chlamydia muridarum female reproductive tract (FRT) infection. After C. muridarum intravaginal infection, IFN-γ-deficient and T cell-deficient mice exhibited opposite phenotypes for survival and bacterial shedding at the FRT mucosa, demonstrating the distinct requirements for IFN-γ and CD4 T cells in host defense against Chlamydia In Rag1-deficient mice, IFN-γ produced by innate lymphocytes (ILCs) accounted for early bacterial control and prolonged survival in the absence of adaptive immunity. Although type I ILCs are potent IFN-γ producers, we found that mature NK cells and ILC1s were not the sole sources of innate IFN-γ in response to Chlamydia By conducting T cell adoptive transfer, we showed definitively that IFN-γ-deficient CD4 T cells were sufficient for effective bacterial killing in the FRT during the first 21 days of infection and reduced bacterial burden more than 1,000-fold, although mice receiving IFN-γ-deficient CD4 T cells failed to completely eradicate the bacteria from the FRT like their counterparts receiving wild-type (WT) CD4 T cells. Together, our results revealed that innate IFN-γ is essential for preventing systemic Chlamydia dissemination, whereas IFN-γ produced by CD4 T cells is largely redundant at the FRT mucosa.

Antibody, but not B-cell-dependent antigen presentation, plays an essential role in preventing Chlamydia systemic dissemination in mice.

The obligate intracellular bacterium Chlamydia trachomatis causes the most prevalent bacterial sexually transmitted infection worldwide. CD4 T cells play a central role in the protective immunity against Chlamydia female reproductive tract (FRT) infection, while B cells are thought to be dispensable for resolution of primary Chlamydia infection in mouse models. We recently reported an unexpected requirement of B cells in local Chlamydia-specific CD4 T-cell priming and bacterial containment within the FRT. Here, we sought to tackle the precise effector function of B cells during Chlamydia primary infection. Using mixed bone marrow chimeras that lack B-cell-dependent Ag presentation (MHCIIB-/- ) or devoid of circulating antibodies (AID-/- × µS-/- ), we show that Chlamydia-specific CD4 T-cell expansion does not rely on Ag presentation by B cells. Importantly, we demonstrate that antibody, but not B-cell-dependent Ag presentation, is required for preventing systemic bacterial dissemination following Chlamydia FRT infection.

THE FUTURE OF TECHNOLOGY AND ROBOTICS IN SURGERY.

In the past three decades, several technologies designed for other purposes, have been applied in surgery to provide more precision to the surgical procedures and better outcomes. In surgery, innovation requires evidence before widespread implementation of novelties and a continuous quality improvement process to assess benefits and risks. Robotics in surgery has been widely implemented, but in some cases, there are many doubts regarding its clinical benefit and cost utility. The future of surgery lies in the fulfillment of four main conditions: safety, access, efficiency, and efficacy. Innovation and technology should help to accomplish these conditions, but it must not be the center of surgical practice. We present here our perspective on the main issues related to technology and robotics focusing on evidence-based surgery.

Establishing consensus on the perioperative management of cholecystectomy in public hospitals: a Delphi study with an expert panel in Mexico.

BACKGROUND: Several guidelines have put forward recommendations about the perioperative process of cholecystectomy. Despite the recommendations, controversy remains concerning several topics, especially in low- and middle-income countries. The aim of this study was to develop uniform recommendations for perioperative practices in cholecystectomy in Mexico to standardize this process and save public health system resources. METHODS: A modified Delphi method was used. An expert panel of 23 surgeons anonymously completed two rounds of responses to a 29-item questionnaire with 110 possible answers. The consensus was assessed using the percentage of responders agreeing on each question. RESULTS: From the 29 questions, the study generated 27 recommendations based on 20 (69.0%) questions reaching consensus, one that was considered uncertain (3.4%), and six (20.7%) items that remained open questions. In two (6.9%) cases, no consensus was reached, and no recommendation could be made. CONCLUSIONS: This study provides recommendations for the perioperative management of cholecystectomy in public hospitals in Mexico. As a guide for public institutions in low- and middle-income countries, the study identifies recommendations for perioperative tests and evaluations, perioperative decision making, postoperative interventions and institutional investment, that might ensure the safe practice of cholecystectomy and contribute to conserving resources.

Choices of Therapeutic Strategies for Colorectal Liver Metastases Among Expert Liver Surgeons: A Throw of the Dice?

OBJECTIVE: To test the degree of agreement in selecting therapeutic options for patients suffering from colorectal liver metastasis (CRLM) among surgical experts around the globe. SUMMARY/BACKGROUND: Only few areas in medicine have seen so many novel therapeutic options over the past decades as for liver tumors. Significant variations may therefore exist regarding the choices of treatment, even among experts, which may confuse both the medical community and patients. METHODS: Ten cases of CRLM with different levels of complexity were presented to 43 expert liver surgeons from 23 countries and 4 continents. Experts were defined as experienced surgeons with academic contributions to the field of liver tumors. Experts provided information on their medical education and current practice in liver surgery and transplantation. Using an online platform, they chose their strategy in treating each case from defined multiple choices with added comments. Inter-rater agreement among experts and cases was calculated using free-marginal multirater kappa methodology. A similar, but adjusted survey was presented to 60 general surgeons from Asia, Europe, and North America to test their attitude in treating or referring complex patients to expert centers. RESULTS: Thirty-eight (88%) experts completed the evaluation. Most of them are in leading positions (92%) with a median clinical experience of 25 years. Agreement on therapeutic strategies among them was none to minimal in more than half of the cases with kappa varying from 0.00 to 0.39. Many general surgeons may not refer the complex cases to expert centers, including in Europe, where they also engage in complex liver surgeries. CONCLUSIONS: Considerable inconsistencies of decision-making exist among expert surgeons when choosing a therapeutic strategy for CRLM. This might confuse both patients and referring physicians and indicate that an international high-level consensus statements and widely accepted guidelines are needed.

Disparities in bile duct injury care.

BACKGROUND: An international group proposed a standardized terminology to report outcomes after bile duct repair. Data on this surgical complication vary depending on the center and country where patients are treated. The aim of this work is to show disparities in the care process of bile duct injury between patients from two different income-level countries, using a standard terminology of outcomes and clinical reporting. METHODS: A retrospective review comparing primary repair and re-repaired cases performed in an upper middle-income country (UMIC) versus primary repair cases treated in a high-income country (HIC) was performed. All pertinent data included in the tabular reporting system and outcomes classification were collected. Patients' characteristics were reported by calculating descriptive statistics. RESULTS: A total of 261 patients from UMIC (148 (56%) primary repair and 113 (44%) re-repair) were compared with 122 primary repair from HIC. Open cholecystectomy (55.4% vs 3.3%) and more E4 injuries (37.8% vs 19.7%) were found in the UMIC group. More Accordion 3 and higher complications were present in the UMIC primary and repair groups, as well as more episodes of postoperative acute cholangitis. Eleven patients were listed for liver transplant in the UMIC re-repair group. Primary patency by the end of the index treatment period was present in 217 (83%) of the full UMIC cohort. Median time to loss of primary patency was not reached in the primary repair, and was 3.8 years in the re-repair group. Patency was below HIC primary repaired cases. CONCLUSIONS: Standardized reporting outcomes after primary repair are applicable to re-repaired patients and are helpful to compare different populations, showing better outcomes in HIC. Measures of surgical access disparities exist among the process of bile duct injury care.

Fellows perspective of HPB training in Latin America.

BACKGROUND: Currently, no standards for HPB training exist in Latin America. The aim of this work is to evaluate fellows' experience of HPB training and the areas of opportunity to improve. METHODS: A 35 points survey was developed and distributed among fellows from dedicated HPB training programs in Latin America. The survey was applied by direct phone call (37%) or web based (63%), to fellows graduated between 2010 and 2014, from 7 different programs. RESULTS: Thirty-nine fellows from Argentina, Brazil, Chile and México were considered with a response rate of 82% (32/39). Most fellows (90%) shared cases with more than one co-fellow. Scrubbing with chief residents ocurred to 60% of fellows; only 14% of fellows noted having a primary surgeon role in more than 70% of cases. Median number of major hepatectomies during training was 15 (1-100), Whipple procedures 6 (1-40), and major bile duct repair 20 (1-80). Limited funding was the main reason to avoid HPB programs outside the country of origin. CONCLUSION: HPB training in Latin America requires more operative volume and autonomy. Financial burden is the main limitation to pursue training overseas. A multinational fellowship that takes advantage of each center may overcome differences in volume and type of cases.

Proposed standards for reporting outcomes of treating biliary injuries.

BACKGROUND: There is no standard nor widely accepted way of reporting outcomes of treatment of biliary injuries. This hinders comparison of results among approaches and among centers. This paper presents a proposal to standardize terminology and reporting of results of treating biliary injuries. METHODS: The proposal was developed by an international group of surgeons, biliary endoscopists and interventional radiologists. The method is based on the concept of "patency" and is similar to the approach used to create reporting standards for arteriovenous hemodialysis access. RESULTS: The group considered definitions and gradings under the following headings: Definition of Patency, Definition of Index Treatment Periods, Grading of Severity of Biliary Injury, Grading of Patency, Metrics, Comparison of Surgical to Non Surgical Treatments and Presentation of Case Series. CONCLUSIONS: A standard procedure for reporting outcomes of treating biliary injuries has been produced. It is applicable to presenting results of treatment by surgery, endoscopy, and interventional radiology.

Liver transplantation center in México with low-volume and excellent results / Centro de trasplante hepático en México con bajo volumen y excelentes resultados

Background: Orthotopic liver transplantation (OLT) is the treatment of choice for end stage liver disease. Many studies show an inverse relationship between the number of procedures and operative mortality. Objective: The objective of the study is to show the results of our center and determine if it can have comparable results to high volumen centers. Method: This is a retrospective study which analyzed the information of patients with OLT at our institution from 1985 to December 31, 2012. Depending on date of transplantation, the study was divided into three stages. Stage 1: from 1985 to 1999. Stage 2: from 2000 to 2007. Stage 3: from 2008 to 2012. In the 1, 2 and 3 stage 22, 37 and 56 OLT were performed respectively. Results: Perioperative mortality was significantly lower between Stage 3 vs. Stage 1 and 2 (3.5% vs. 50% and 21.7%, p = 0.001). Patient survival was also better at 1 and 5 years at Stage 3 (94.4%, 87.8%) vs. era 2 (77.6%, 66.17%) and Stage 1 (47% and 29%) (p = 0.001). Conclusion: In conclusion, the present results of OLT at our program are excellent despite being a low-volume center.

Antecedentes: El trasplante hepático ortotópico (THO) es el tratamiento de elección para la insuficiencia hepática terminal. Numerosos estudios muestran una relación inversa entre el número de procedimientos y la mortalidad operatoria. Objetivo: El objetivo de este estudio es mostrar los resultados de nuestro centro y determinar si puede tener resultados equiparables a los obtenidos en centros de alto volumen. Método: Es un estudio retrospectivo en el que se analizó la información de pacientes con THO en nuestra institución, de 1985 al 31 de diciembre de 2012. Dependiendo de la fecha del THO, el estudio se dividió en tres etapas: etapa 1, de 1985 a 1999; etapa 2, de 2000 a 2007; y etapa 3, de 2008 a 2012. En las etapas 1, 2 y 3 se realizaron 22, 37 y 56 THO, respectivamente. Resultados: La mortalidad perioperatoria fue menor de manera significativa en la etapa 3 en comparación con las etapas 1 y 2 (3.5 vs. 50 y 21.7%; p = 0.001). La supervivencia de los pacientes a 1 y 5 años fue mejor en la etapa 3 (94.4 y 87.8%) que en la etapa 2 (77.6 y 66.17%) y en la etapa 1 (47 y 29%) (p = 0.001). Conclusión: En conclusión, los resultados actuales en THO en nuestro programa son excelentes, a pesar de ser un centro de bajo volumen.

Timing of Surgical Repair After Bile Duct Injury Impacts Postoperative Complications but Not Anastomotic Patency.

OBJECTIVE: Our goal was to determine the optimal timing for repair of bile duct injuries sustained during cholecystectomy. BACKGROUND: Bile duct injury during cholecystectomy is a serious complication that often requires surgical repair. There is heterogeneity in the literature regarding the optimal timing of surgical repair, and it remains unclear to what extent timing determines postoperative morbidity and long-term anastomotic function. METHODS: A single institution prospective database was queried for all E1 to E4 injuries from 1989 to 2014 using a standardized tabular reporting format. Timing was stratified into 3 groups [early (<7 days), intermediate (8 days until 6 weeks), and late (>6 weeks) after injury]. Analysis was stratified between those who had a previous bile duct repair or not, including postoperative complications and anastomotic failure as outcome variables in 2 separate multivariate logistic regression models. RESULTS: There were 614 patients included in the study. The mean age was 41 years (range, 15-85 yrs), and the majority were female (80%). The mean follow-up time was 40.5 months. Side-to-side hepaticojejunostomy was performed in 94% of repairs. Intermediate repair was associated with a higher risk of postoperative complications [odd ratio = 3.7, 95% confidence interval (1.3-10.2), P = 0.01] when compared with early and late in those with a previous repair attempt. Sepsis control and avoidance of biliary stents were protective factors against anastomotic failure. CONCLUSIONS: Adequate sepsis control and delayed repair of biliary injuries should be considered for patients presenting between 8 days and 6 weeks after injury to prevent complications, if a previous bile duct repair was attempted.

Performance of robotic simulated skills tasks is positively associated with clinical robotic surgical performance.

OBJECTIVE: To compare user performance of four fundamental inanimate robotic skills tasks (FIRST) as well as eight da Vinci Skills Simulator (dVSS) virtual reality tasks with intra-operative performance (concurrent validity) during robot-assisted radical prostatectomy (RARP) and to show that a positive correlation exists between simulation and intra-operative performance. MATERIALS AND METHODS: A total of 21 urological surgeons with varying robotic experience were enrolled. Demographics were captured using a standardized questionnaire. User performance was assessed concurrently in simulated (FIRST exercises and dVSS tasks) and clinical environments (endopelvic dissection during RARP). Intra-operative robotic clinical performance was scored using the previously validated six-metric Global Evaluative Assessment of Robotic Skills (GEARS) tool. The relationship between simulator and clinical performance was evaluated using Spearman's rank correlation. RESULTS: Performance was assessed in 17 trainees and four expert robotic surgeons with a median (range) number of previous robotic cases (as primary surgeon) of 0 (0-55) and 117 (58-600), respectively (P = 0.001). Collectively, the overall FIRST (ρ = 0.833, P < 0.001) and dVSS (ρ = 0.805, P < 0.001) simulation scores correlated highly with GEARS performance score. Each individual FIRST and dVSS task score also demonstrated a significant correlation with intra-operative performance, with the exception of Energy Switcher 1 exercise (P = 0.063). CONCLUSIONS: This is the first study to show a significant relationship between simulated robotic performance and robotic clinical performance. Findings support implementation of these robotic training tools in a standardized robotic training curriculum.

Multi-Institutional Validation of Fundamental Inanimate Robotic Skills Tasks.

PURPOSE: Our group has previously reported the development and validation of FIRST (Fundamental Inanimate Robotic Skills Tasks), a series of 4 inanimate robotic skills tasks. Expanding on the initial validation, we now report face, content and construct validity of FIRST in a large multi-institutional cohort of experts and trainees. MATERIALS AND METHODS: A total of 96 residents, fellows and attending surgeons completed the FIRST exercises at participating institutions. Participants were classified based on previous robotic experience and task performance was compared across groups to establish construct validity. Face and content validity was assessed from participant ratings of the tasks on a 5-point Likert scale. RESULTS: A total of 51 novice, 22 intermediate and 23 expert participants with a median previous robotic experience of 0 (range 0 to 3), 10 (range 5 to 30) and 200 cases (range 55 to 2,000), respectively (p<0.001), were assessed across all 4 inanimate robotic skills tasks. Expert and intermediate groups reliably outperformed novices (p<0.01). Experts also performed better than intermediates on all exercises (p<0.01). A survey of participants on their perceptions of the tasks yielded excellent face and content validity. CONCLUSIONS: We confirm robust face, content and construct validity of 4 inanimate robotic training tasks in a large multi-institutional cohort. FIRST tasks are reliably able to discern among expert, intermediate and novice robotic surgeons. Validation data from this large multi-institutional cohort is useful as we incorporate these tasks into a comprehensive robotic training curriculum.

BILE DUCT INJURY REPAIR IN A PATIENT WITH SITUS INVERSUS TOTALIS.

BACKGROUND: Bile duct injury (BDI) causes significant sequelae for the patient in terms of morbidity, mortality, and long-term quality of life, and should be managed in centers with expertise. Anatomical variants may contribute to a higher risk of BDI during cholecystectomy. AIMS: To report a case of bile duct injury in a patient with situs inversus totalis. METHODS: A 42-year-old female patient with a previous history of situs inversus totalis and a BDI was initially operated on simultaneously to the lesion ten years ago by a non-specialized surgeon. She was referred to a specialized center due to recurrent episodes of cholangitis and a cholestatic laboratory pattern. Cholangioresonance revealed a severe anastomotic stricture. Due to her young age and recurrent cholangitis, she was submitted to a redo hepaticojejunostomy with the Hepp-Couinaud technique. To the best of our knowledge, this is the first report of BDI repair in a patient with situs inversus totalis. RESULTS: The previous hepaticojejunostomy was undone and remade with the Hepp-Couinaud technique high in the hilar plate with a wide opening in the hepatic confluence of the bile ducts towards the left hepatic duct. The previous Roux limb was maintained. Postoperative recovery was uneventful, the drain was removed on the seventh post-operative day, and the patient is now asymptomatic, with normal bilirubin and canalicular enzymes, and no further episodes of cholestasis or cholangitis. CONCLUSIONS: Anatomical variants may increase the difficulty of both cholecystectomy and BDI repair. BDI repair should be performed in a specialized center by formal hepato-pancreato-biliary surgeons to assure a safe perioperative management and a good long-term outcome.

Functional diversity of bacterial microbiota associated with the toxigenic benthic dinoflagellate Prorocentrum.

Interactions between bacterial microbiota and epibenthic species of the dinoflagellate Prorocentrum may define the onset and persistence of benthic harmful algal blooms (bHABs). Chemical ecological interactions within the dinoflagellate phycosphere potentially involve a complex variety of organic molecules, metabolites, and toxins, including undefined bioactive compounds. In this study, the bacterial diversity and core members of the dinoflagellate-associated microbiota were defined from 11 strains of three epibenthic Prorocentrum species, representing three geographically disjunct locations within Mexican coastal waters. Microbiota profiles in stable monoclonal Prorocentrum cultures were obtained by sequencing amplicons of the V3-V4 region of the 16S rRNA gene. Thirteen classes of bacteria were identified among dinoflagellate clones, where Alphaproteobacteria, Gammaproteobacteria, and Bacteroidia were consistently dominant. The bacterial community structure exhibited significantly different grouping by the location of origin of dinoflagellate clones. No significant diversity difference was found among free-living or unattached bacteria in the dinoflagellate culture medium (M) compared with those in closer association with the dinoflagellate host cells (H). Twelve taxa were defined as core members of the bacterial assemblage, representing the genera Algiphilus, Cohaesibacter, Labrenzia, Mameliella, Marinobacter, Marivita, Massilia, Muricauda, Roseitalea, and an unclassified member of the Rhodobacteraceae. The core members are inferred to significantly contribute to primary and secondary metabolic functions, but no direct correlation with dinoflagellate toxigenicity was apparent. Overall the bacterial profile and implied gene functionality indicated a suite of positive interactions, suggesting either mutualism or commensalism with the dinoflagellate. The further characterization and interpretation of specific gene functions and interactions between bacteria and dinoflagellates, such as epibenthic members of genus Prorocentrum, are key to understanding their role in toxigenesis and bHAB development.