Imaging host–pathogen interactions

Dental Abscess to Septic Shock: A Case Report and Literature Review

Sepsis is a leading cause of death in the United States, with a mortality rate in excess of 215,000 deaths per year. It may lead to septic shock, a complex pathophysiological process with microbial and host response events that progress to multisystem derangement. There is poor documentation of the relationship between dental infection and septic shock, with only a few case reports of septic shock secondary to dentoalveolar abscess. Presented is a case of sepsis/septic shock in a 23-year-old man with signs and symptoms of pulpal necrosis, acute apical abscess, and canine space infection that rapidly progressed to an altered mental state, hyperthermia, tachycardia, hypotension, acute respiratory failure, diarrhea, renal insufficiency, lactic acidosis, leukocytosis, and hyperglycemia. Once septic shock develops, the mortality rate is nearly 50%. Early antimicrobial intervention is associated with surviving severe sepsis, making it critical for dentists to understand local factors leading to the crisis and the signs and symptoms of the sepsis-septic shock continuum.

Expression of fluorescent proteins in bifidobacteria for analysis of host-microbe interactions

Bifidobacteria are an important component of the human gastrointestinal microbiota and are frequently used as probiotics. The genetic inaccessibility and lack of molecular tools commonly used in other bacteria have hampered a detailed analysis of the genetic determinants of bifidobacteria involved in their adaptation to, colonization of, and interaction with the host. In the present study, a range of molecular tools were developed that will allow the closing of some of the gaps in functional analysis of bifidobacteria. A number of promoters were tested for transcriptional activity in Bifidobacterium bifidum S17 using pMDY23, a previously published promoter probe vector. The promoter of the gap gene (Pgap) of B. bifidum S17 yielded the highest promoter activity among the promoters tested. Thus, this promoter and the pMDY23 backbone were used to construct a range of vectors for expression of different fluorescent proteins (FPs). Successful expression of cyan fluorescent protein (CFP), green fluorescent protein (GFP), yellow fluorescent protein (YFP), and mCherry could be shown for three strains representing three different Bifidobacterium spp. The red fluorescent B. bifidum S17/pVG-mCherry was further used to demonstrate application of fluorescent bifidobacteria for adhesion assays and detection in primary human macrophages cultured in vitro. Furthermore, pMGC-mCherry was cloned by combining a chloramphenicol resistance marker and expression of the FP mCherry under the control of Pgap. The chloramphenicol resistance marker of pMGC-mCherry was successfully used to determine gastrointestinal transit time of B. bifidum S17. Moreover, B. bifidum S17/pMGC-mCherry could be detected in fecal samples of mice after oral administration.

The pathophysiology of septic shock

Septic shock remains a significant challenge for clinicians. Recent advances in cellular and molecular biology have significantly improved our understanding of its pathogenetic mechanisms. These improvements in understanding should translate to better care and improved outcomes for these patients.

A genotype and phenotype database of genetically modified malaria-parasites

The RMgm database, www.pberghei.eu, is a web-based, manually curated, repository containing information on genetically modified rodent-malaria parasites. It provides easy and rapid access to information on the genotype and phenotype of mutant and reporter parasites. The database also contains information on unpublished mutants without a clear phenotype and negative trials to disrupt genes. Information can be searched using pre-defined key features, such as phenotype, life-cycle stage, gene model, gene-tags and mutations. The information relating to the mutants is reciprocally linked to PlasmoDB and GeneDB. Access to mutant-parasite information, and gene function/ontology inferred from mutant phenotypes provides a timely resource aimed at enhancing research into Plasmodium gene function and (systems) biology.

The pathophysiology of septic shock

There is a profound cellular dysfunction in sepsis, that clinically manifests as a continuum from simple, uncomplicated sepsis to severe sepsis, and finally to septic shock. Septic shock remains a significant challenge for clinicians. Recent advances in cellular and molecular biology have significantly improved our understanding of its pathogenetic mechanisms. These improvements will translate to better care and improved outcomes for these patients.

Two-photon microscopy of host-pathogen interactions: acquiring a dynamic picture of infection in vivo

Two-photon (2P) microscopy has become increasingly popular among immunologists for analysing single-cell dynamics in tissues. Researchers are now taking 2P microscopy beyond the study of model antigen systems (e.g. ovalbumin immunization) and are applying the technique to examine infection in vivo. With the appropriate fluorescent probes, 2P imaging can provide high-resolution spatio-temporal information regarding cell behaviour, monitor cell functions and assess various outcomes of infection, such as host cell apoptosis or pathogen proliferation. Imaging of transgenic and knockout mice can be used to probe molecular mechanisms governing the host response to infection. From the microbe side, imaging genetically engineered mutant strains of a pathogen can test the roles of specific virulence factors in pathogenesis. Here, we discuss recent work that has applied 2P microscopy to study models of infection and highlight the tremendous potential that this approach has for investigating host-pathogen interactions.