Microbial Interspecies Associations in Fracture-Related Infection.

OBJECTIVES: Describe co-occurrence or clustering of microbial taxa in fracture-related infections to inform further exploration of infection-related interactions among them. DESIGN: Retrospective review. SETTING: Level 1 trauma center. PATIENTS/PARTICIPANTS: Four hundred twenty-three patients requiring surgical intervention for deep surgical site infection between January 2006 and December 2015. INTERVENTION: None. MAIN OUTCOME MEASUREMENT: Connection between microbial taxa. RESULTS: Methicillin-resistant Staphylococcus aureus, methicillin-sensitive Staphylococcus aureus, and coagulase-negative Staphylococcus represented the majority of monomicrobial observations (71%). Gram-negative rods, gram-positive rods, and anaerobes presented more frequently in polymicrobial infections. Enterobacter, vancomycin-sensitive Enterococcus, and Pseudomonas are present in polymicrobial infections with the highest frequencies and represent the top 3 most important nodes within the microorganism framework, with the highest network centrality scores. CONCLUSIONS: The present study indicates that there are common microbial taxa (Enterobacter, Enterococcus, and Pseudomonas) that tend to co-occur with other microbes greater than 75% of the time. These commonly co-occurring microbes have demonstrated interactive relationships in other disease pathologies, suggesting that there may be similar important interactions in fracture-related infections. It is possible that these microbial communities play a role in the persistently high failure rate associated with management of infection after trauma. Future studies are needed to study the intermicrobial interactions that explain the frequency at which taxa co-occur. Understanding and potentially disrupting these intermicrobial relationships could inform improvements in the treatment of established infections and in the prevention of infection in high-risk patients. LEVEL OF EVIDENCE: Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Host Matters: Medicinal Leech Digestive-Tract Symbionts and Their Pathogenic Potential.

Digestive-tract microbiota exert tremendous influence over host health. Host-symbiont model systems are studied to investigate how symbioses are initiated and maintained, as well as to identify host processes affected by resident microbiota. The medicinal leech, Hirudo verbana, is an excellent model to address such questions owing to a microbiome that is consistently dominated by two species, Aeromonas veronii and Mucinivorans hirudinis, both of which are cultivable and have sequenced genomes. This review outlines current knowledge about the dynamics of the H. verbana microbiome. We discuss in depth the factors required for A. veronii colonization and proliferation in the leech crop and summarize the current understanding of interactions between A. veronii and its annelid host. Lastly, we discuss leech usage in modern medicine and highlight how leech-therapy associated infections, often attributable to Aeromonas spp., are of growing clinical concern due in part to an increased prevalence of fluoroquinolone resistant strains.

Changes in DNA methylation and gene expression during 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced suppression of the lipopolysaccharide-stimulated IgM response in splenocytes.

Lipopolysaccharide (LPS) is a bacterial endotoxin and a potent B-cell activator capable of inducing a humoral immune response. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a well-established immunotoxicant that can suppress humoral immune responses, including those initiated by LPS stimulation. In murine models, TCDD-induced suppression of the LPS-activated primary immunoglobulin M (IgM) response is observed both in vivo and in vitro and is typically evaluated as a decrease in the number of IgM antibody-forming cells. The TCDD-induced suppression of the primary humoral immune response occurs, at least in part, upstream of IgM production. The current study was designed as an initial test of our hypothesis that altered DNA methylation, an epigenetic event, is involved in the LPS-induced IgM response by splenocytes as is the suppression of this response by TCDD. Splenocyte-derived DNA from mice treated in vivo with sesame oil + PBS, LPS, TCDD, or LPS + TCDD was used for the current investigation. DNA methylation was evaluated using a technique that permits assessment of the methylation status of multiple genomic regions simultaneously in an unbiased fashion (no specific genes or genomic regions are preselected). Additionally, the expression of selected genes was determined. Our results indicate that treatment with LPS or TCDD can alter DNA methylation and, importantly, combined TCDD + LPS results in altered DNA methylation that was not simply the addition of the changes discerned in the individual treatment groups. Thus, we have identified cross talk between LPS and TCDD at the level of DNA methylation and gene expression.