Clinical Infectious Diseases: Open Access

Microbial biofilms provide an appropriate environment for increased genetic exchange. Extracellular DNA (eDNA) is an essential component of the extracellular matrix of microbial biofilms, but the pathway(s) responsible for DNA release are largely unknown. Autolysis (either spontaneous or phage-induced) has been proposed the major event leading to the appearance of eDNA. The ‘suicidal tendency’ of Streptococcus pneumoniae is well-known, with lysis mainly caused by the triggering of LytA, the major autolytic amidase. However, the LytC lysozyme and CbpD (a possible murein hydrolase) have also been shown involved. The present work examines the relationship between eDNA, autolysins, and the formation and maintenance of in vitro pneumococcal biofilms, via fluorescent labeling combined with confocal laser scanning microscopy, plus genetic transformation experiments. Bacterial DNA release mechanisms other than those entailing lytic enzymes were shown to be involved by demonstrating that horizontal gene transfer in biofilms takes place even in the absence of detectable autolytic activity. Evidence that the release of DNA is somehow linked to the production of extracellular vesicles by S. pneumoniae is provided.

Introduction: Serum Bactericidal Assays (SBAs) are considered as the gold standard to evaluate the immunogenicity of many vaccine formulations against infectious agents, for example Neisseria meningitidis vaccines. SBAs are also used to evaluate vaccine lots before release to the market, because it has been demonstrated that there is a correlation between bactericidal antibody titers and protection. For Laboratory and Clinical Good Practice, it is very important to have a positive control in each assay. To our knowledge, there is no commercial positive control to serve this function, therefore the purpose of this work was to evaluate a monoclonal antibody (mAb) panel against N. meningitidis strains produced at Institute Finlay of Vaccines as a reference material in the established bactericidal assay, with the advantage of high homogeneity and specificity and relative low cost of the mAbs test agents.
Materials and Methods: Specificity of a panel of mAbs was evaluated by a whole cell enzyme linked immunoassay (ELISA). The positive mAbs were then tested for bactericidal effect against target strains: F8238 (serogroup A), CU385/83 y NZ228/98 (serogroup B) and C11 (serogroup C). Determinations were carried out in triplicate and the mean was calculated.
Results: In this study, we positively identified five mAbs out of seven that recognised specific, selected N. meningitidis strains. However, only three mAbs (anti-PsA, anti-P1.15 and anti-P1.4) showed bactericidal activity with their homologous strain, and this was related to the mAbs subclass.
Conclusions: Three monoclonal antibodies presented bactericidal activity and they have the potential to be used as positive controls in bactericidal assays.

Background: The American Gastroenterological Association Institute guidelines on hepatitis B reactivation (HBVr) advocate for screening and treatment with nucleoside analogues. These drugs are known to cause mitochondrial toxicity and monitoring is recommended. Additionally, chemotherapy can cause mitochondrial damage that may enhance nucleosides toxicity. Compliance with these guidelines, however, is unknown. We present a case of fatal outcome of HBVr that could have been prevented with screening.
Case presentation: A 69-year-old female received chemotherapy for invasive breast cancer without prior screening for hepatitis B. She developed abdominal pain and loss of appetite few weeks after finishing chemotherapy. She was found to have elevated liver enzymes (ALT=2000 unit), positive hepatitis B surface antigen and hepatitis B viremia (11 × 107 IU). She was diagnosed with HBVr. She was started on tenofovir although by the time treatment was initiated her symptoms were improving, ALT decreased to 726 unit and hepatitis B viremia dropped to 16 × 104 IU. Few days after starting tenofovir she developed abdominal pain, diarrhea, vomiting, lactic acidosis, cardiomyopathy and eventually expired. The final manifestations and laboratory findings were suggestive of mitochondrial toxicity.
Conclusions: This case suggests that recent chemotherapy may predispose to rapid onset of severe tenofovir toxicity and illustrates the importance of compliance with HBV screening and monitoring for drug toxicity during treatment.

We report the first case of a picturesque exogenous Listeria monocytogenes endophthalmitis in a previously healthy woman after a cow tail’s sweep, successfully treated with surgical and linezolid. We discuss the interest of linezolid, until then never used in this specific infection. The pharmacokinetic properties and the anti-gram positive activity of the linezolid may challenge the requirement for intravenous therapy in gram positive endophthalmitis on long term treatment.