Spatial Characteristics of Colonic Mucosa-Associated Gut Microbiota in Humans

Limited data exist on the spatial distribution of the colonic bacteria in humans. We collected the colonic biopsies from five segments of 27 polyp-free adults and collected feces from 13 of them. We sequenced the V4 region of the bacterial 16S rRNA gene using the MiSeq platform. The sequencing data were assigned to the amplicon sequence variant (ASV) using SILVA. Biodiversity and the relative abundance of the ASV were compared across the colonic segments and between the rectal and fecal samples. Bacterial functional capacity was assessed using Tax4fun. Each individual had a unique bacterial community composition (Weighted Bray-Curtis P value = 0.001). There were no significant differences in richness, evenness, community composition, and the taxonomic structure across the colon segments in all the samples. Firmicutes (47%), Bacteroidetes (39%), and Proteobacteria (6%) were the major phyla in all segments, followed by Verrucomicrobia, Fusobacteria, Desulfobacterota, and Actinobacteria. There were 15 genera with relative abundance > 1%, including Bacteroides, Faecalibacterium, Escherichia/Shigella, Sutterella, Akkermansia, Parabacteroides, Prevotella, Lachnoclostridium, Alistipes, Fusobacterium, Erysipelatoclostridium, and four Lachnospiraceae family members. Intra-individually, the community compositional dissimilarity was the greatest between the cecum and the rectum. There were significant differences in biodiversity and the taxonomic structure between the rectal and fecal bacteria. The bacterial community composition and structure were homogeneous across the large intestine in adults. The inter-individual variability of the bacteria was greater than inter-segment variability. The rectal and fecal bacteria differed in the community composition and structure.

Immunosuppressive Drug Levels in Liver Transplant Recipients: Impact in Decision Making

To prevent rejection, liver transplant providers largely base their management decisions on their clinical impression and pharmacokinetics. Clinical impression relies on assessing graft function, liver enzymes, and biopsy. High immunosuppressive drug levels, although minimizing rejection, are related to significant side effects such as nephrotoxicity and metabolic syndrome, contributing to long-term morbidity and mortality. Similarly, levels that are lower than necessary can decrease the rate of side effects with a potential toll on rejection and graft survival. Herein, the authors present an update on immunosuppressive drug level monitoring and manipulation strategies according to different scenarios and time from transplant. They also provide a brief overview of next level immunosuppression monitoring strategies that aim to properly balance rejection rates with drug side effect profiles.

Pathogenesis of Alcoholic Liver Disease: An Update

Apart from the classic knowledge that ethanol mediates its hepatotoxicity through its metabolism to acetaldehyde, a well-known hepatotoxic molecule, recent research has elucidated several key mechanisms that potentiate ethanol's damage to the liver parenchyma, such as generation of free radicals, activation of Kupffer cells, and alterations to the human bacterial and fungal microbiome. Genetic studies have suggested the role of PNPLA3 and TM6SF2 gene mutations in the progression of alcoholic liver disease.

Antibody Response to Hepatitis B Virus Vaccine is Impaired in Patients With Inflammatory Bowel Disease on Infliximab Therapy

BACKGROUND

Studies have demonstrated an association between anti-TNF/immunomodulator agents used in inflammatory bowel disease (IBD) and impaired hepatitis B virus (HBV) vaccine immunogenicity, but little data exist on whether specific medication types affect protective HBsAb titers. Our aim was to analyze this association.

METHODS

This is a retrospective cohort study. Inclusion criteria: age ≥18, diagnosis of Crohn's disease (CD) or ulcerative colitis (UC), previous HBV vaccination series and/or ≥1 positive HBsAb, and record of IBD therapy in 6 months before titer level. Patients were stratified based upon medication exposures: anti-TNF, immunomodulator, combination anti-TNF and immunomodulatory, and a reference arm. Titer levels following vaccination and specific medication types given in the 6 months before titer were recorded. Seroprotection was defined as HBsAb ≥10 IU/l and ≥100 IU/l.

RESULTS

The study cohort (N = 391) was 70.8% white, 51.4% female and 64.2% had CD and 35.8% had UC. The mean age was 45.8 years. A significantly lower percentage of patients exposed to anti-TNF, immunomodulator or dual therapy had titers ≥10 (P < 0.01). Regarding specific medications, only patients exposed to infliximab (P < 0.01) were less likely to have titer levels ≥10, after controlling for other medication exposures, age at titer level, and interval time between vaccination/titer level. This was not found for patients exposed to adalimumab, methotrexate, 6-mercaptopurine, or azathioprine.

CONCLUSIONS

Patients exposed to infliximab were significantly less likely to have protective HBsAb titer levels following vaccination, a trend not seen in patients on adalimumab. Efforts to vaccinate IBD patients against HBV before use of immunomodulators and anti-TNFs, infliximab specifically, and screen periodically thereafter must be reinforced.

Risk factors for invasive fungal disease after allogeneic hematopoietic stem cell transplantation: a single center experience

Invasive fungal disease (IFD) is a major cause of morbidity and mortality after hematopoietic stem cell transplantation (HCT). We performed a retrospective review of 271 adults with a hematologic malignancy undergoing allogeneic HCT to determine the incidence of and risk factors for IFD and to examine the impact of IFD on nonrelapse mortality and overall survival. We defined IFD using standard criteria and selected proven and probable cases for analysis. Diagnoses in the study group included acute leukemia (42%), non-Hodgkin lymphoma (24%), myelodysplastic syndrome (15%), chronic lymphocytic leukemia (5%), and other hematologic disorders (14%). Conditioning included reduced-intensity (64%) and myeloablative (36%) regimens. Donor sources were HLA-matched sibling (60%), matched unrelated (20%), haploidentical (12%), and cord blood (8%). A total of 51 episodes of IFD were observed in 42 subjects (15%). Aspergillus spp (47%) was the most frequent causative organism, followed by Candida spp (43%). The majority of IFD cases (67%) were reported after day +100 post-HCT. In multivariate analysis, haploidentical donor transplantation (hazard ratio [HR], 3.82; 95% confidence interval [CI], 1.49-9.77; P = .005) and grade II-IV acute graft-versus-host disease (HR, 2.55; 95% CI, 1.07-6.10; P = .03) were risk factors for the development of IFD. Conversely, higher infused CD34(+) cell dose was associated with a lower risk of IFD (HR, 0.80; 95% CI, 0.68-0.94; P = .006, per 1 × 10(6) cells/kg increase in CD34(+) cell infusion). IFD-related mortality was 33.3%. Nonrelapse mortality was significantly higher in patients who developed IFD compared with those without IFD (P < .001, log-rank test). Patients with IFD had lower overall survival (5.8 months versus 76.1 months; P < .001, log-rank test). Further studies exploring strategies to increase the infused cell dose and determine adequate prophylaxis, especially against aspergillus, beyond day +100 are needed.

Candida infection and colonization among non-trauma emergency surgery patients

BACKGROUND

Candida is a significant pathogen among critically ill patients. However, candidiasis among non-trauma emergency surgery (NTES) patients has not been previously investigated. Herein we describe the incidence of both colonization and infection from Candida and risk factors for invasive disease in this population.

METHODS

For this retrospective single center study we included all NTES patients with ICU stay ≥4 days from May 1(st), 2002 to April 30(th), 2007. Patients were divided into 3 non-overlapping groups: 1) patients with Candida-infection, 2) patients with Candida colonization and 3) patients with negative Candida cultures. Groups were compared by univariate and multivariate analyses to identify significant risk factors for invasive candidiasis.

RESULTS

Of all 289 eligible patients, 63 (21.7%) fulfilled the criteria for Candida infection and 110 (38%) were included in the Candida colonization group. Interestingly, from the 63 patients with invasive candidiasis, 25 (39.7%) were infected by a non-albicans species. Upon multivariate analyses, ventilator-associated pneumonia (VAP) (Odds Ratio [OR]: 2.34; 95%, Confidence Interval [CI]: 1.213-4.533, p = 0.0112), bacteremia (OR: 4.778; 95%CI: 1.519-15.029, p = 0.0075) and surgical complications (OR: 3.903; 95%CI: 1.335-11.412, p = 0.0129) were independent risk factors for the development of Candida infection. Candida infection and colonization were both found to correlate with approximately $40,000-100,000 mean additional costs). Interestingly, candidemia was associated with 63% all-cause mortality. For all other forms of candidiasis, mortality was not significantly different among groups.

CONCLUSION

We found that Candida infection is alarmingly high among NTES patients with prolonged intensive care unit (ICU) stay. Surgical complications and bacterial infections (VAP and bacteraemia) were significantly correlated with the development of candidiasis. Candidiasis reached a rate of 21.7/100 discharges, which is significantly higher than most established high-risk populations for candidiasis. Future studies should review the need for antifungal prophylaxis on this population.

Candida infection and colonization among trauma patients

BACKGROUND

Data on Candida infection among critically ill trauma patients are limited and not recently updated. Here we study the epidemiology and economic impact of Candida and examine potential risk factors for Candida infection in this population.

METHODS

In this 5-year retrospective study, all severely injured patients with ≥4 days of intensive care unit stay were included, with the primary outcome being Candida infection. We identified 3 distinct patient groups: 1) The Candida infection, 2) The Candida colonization and 3) the Candida-free group. All comparisons between groups with p-values ≤0.2 from the univariate analysis were entered into stepwise logistic regression to identify independent risk factors for candidiasis.

RESULTS

374 patients were included. Upon comparisons between groups, candidiasis patients received significantly more blood transfusions (p=0.013), antibiotics (p=0.005), and total parenteral nutrition (TPN) (p=0.004), had a longer duration of mechanical ventilation (MV) (p=0.008) and underwent more laparotomy procedures than Candida free patients (56.5% versus 16.4%; p<0.001). Surgical complications (13% versus 1.4%; p=0.013), injury of the upper (13% versus 0.9%; p=0.007) and lower gastrointestinal tract (8.7% versus 0.9%; p=0.048), and bacterial wound or intra-abdominal infections (17.4% versus 1.9%; p=0.004) were also more common in candidiasis patients. Upon multivariate analysis, patients receiving TPN had 7-fold higher odds for developing candidiasis (Odds ratio [OR]: 7.2; 95% Confidence interval [CI]: 2.6-19.4; p=0.0001). Other predisposing factors included laparotomy (OR: 3.8, 95% CI: 1.5-9.9; p=0.0057) and female gender (OR: 5.7; 95% CI: 2.1-15.6; p=0.0007). Average total hospital charges were higher for patients with Candida infection compared to patients with Candida colonization or without a positive Candida culture.

CONCLUSIONS

TPN, laparotomy, and female gender independently predict the development of candidiasis among trauma patients. Severely injured women requiring laparotomy and TPN therapy should be carefully managed for the possibility of increased risk for candidiasis.