Interference of a speB 5′ untranslated region partial deletion with mRNA degradation in Streptococcus pyogenes

The 5′ untranslated region (5′ UTR) of an mRNA molecule embeds important determinants that modify its stability and translation efficiency. In Streptococcus pyogenes, a strict human pathogen, a gene encoding a secreted protease (speB) has a large 5′ UTR with unknown functions. Here we describe that a partial deletion of the speB 5′ UTR caused a general accumulation of mRNA in the stationary phase, and that the mRNA accumulation was due to retarded mRNA degradation. The phenotype was observed in several M serotypes harboring the partial deletion of the speB 5′ UTR. The phenotype was triggered by the production of the truncated speB 5′ UTR, but not by the disruption of the intact speB 5′ UTR. RNase Y, a major endoribonuclease, was previously shown to play a central role in bulk mRNA turnover in stationary phase. However, in contrast to our expectations, we observed a weaker interaction between the truncated speB 5′ UTR and RNase Y compared with the wild‐type, which suggests that other unidentified RNA degrading components are required for the pleiotropic effects observed from the speB UTR truncation. Our study demonstrates how S. pyogenes uses distinct mRNA degradation schemes in exponential and stationary growth phases.     

Live and let die: Hydrogen peroxide production by the commensal flora and its role in maintaining a symbiotic microbiome

The majority of commensal oral streptococci are able to generate hydrogen peroxide (H₂O₂) during aerobic growth, which can diffuse through the cell membrane and inhibit competing species in close proximity. Competing H₂O₂ production is mainly dependent upon the pyruvate oxidase SpxB, and to a lesser extent the lactate oxidase LctO, both of which are important for energy generation in aerobic environments. Several studies point to a broad impact of H₂O₂ production in the oral environment, including a potential role in biofilm homeostasis, signaling, and interspecies interactions. Here, we summarize the current research regarding oral streptococcal H₂O₂ generation, resistance mechanisms, and the ecological impact of H₂O₂ production. We also discuss the potential therapeutic utility of H₂O₂ for the prevention/treatment of dysbiotic diseases as well as its potential role as a biomarker of oral health.     

Expanded range of Burkholderia species in Australia

We recently reported the production of the recombinant kinesin-related protein of Leishmania donovani with a molecular weight of 42 kd (rKRP42) and the value of the antigen in serum-based ELISA for the diagnosis of visceral leishmaniasis (VL). In this study, the rKRP42 antigen was validated with ELISA using urine samples (rKRP42 urine ELISA). The urine-based ELISA showed 94% sensitivity (108 positives among 115 VL samples) and 99.6% specificity (239 negatives among 240 non-VL samples). The sensitivity and specificity are almost similar to our previous results by ELISA with acetone-treated L. donovani promastigote antigen and direct agglutination test, both methods being done by use of urine samples. A comparison of the rKRP42 urine ELISA with the commercially available urinary antigen detection kit (KAtex) using 108 VL samples showed much higher sensitivity of the ELISA (96.3%) than KAtex (55.6%). The use of the rKRP42 antigen with urine samples will facilitate epidemiologic studies.     

p53 gene mutations and protein accumulation in human ovarian cancer.

Mutations of the p53 gene on chromosome 17p are a common genetic change in the malignant progression of many cancers. We have analyzed 38 malignant tumors of ovarian or peritoneal müllerian type for evidence of p53 variations at either the DNA or protein levels. Genetic studies were based on single-strand conformation polymorphism analysis and DNA sequencing of exons 2 through 11 of the p53 gene; mutations were detected in 79% of the tumors. These data show a statistically significant association between mutations at C.G pairs and a history of estrogen therapy. Two of 20 patients whose normal tissue could be studied carried germ-line mutations of p53. Immunohistochemical analysis of the p53 protein was carried out using monoclonal antibody PAb1801. Ninety-six percent of the missense mutations were associated with abnormal accumulation of p53 protein, but nonsense mutations, a splicing mutation, and most deletions did not result in p53 protein accumulation. A statistically significant association between p53 protein accumulation in poorly differentiated stage III serous carcinomas and small primary tumor size at diagnosis was found, perhaps suggesting that p53 protein accumulation accelerates the metastatic spread from a primary tumor. Overall, our findings indicate that alterations of p53 play a major role in ovarian cancer, including predisposition to the disease in some patients, and suggest a possible mechanism for somatic mutations leading to this cancer.     

Role of internal fixation in infection of open fractures: studies with Staphylococcus aureus and Proteus mirabilis

Studies of infections in open fractures are described. The hamster was chosen as the experimental model. Osteotomies of the femur were created with an osteotomy saw. Some osteotomies were left to heal and others were fixed with an 0.9 mm K-wire. The infection rates in fixed and unfixed fractures were compared. The first group of hamsters with fixed and unfixed osteotomies was returned to cages with open wounds. There was no difference in the infection rate at 2 weeks. The second group was deliberately contaminated with Staphylococcus aureus and then returned to cages with open wounds. In this group, the infection rate at 2 weeks was lower in the internally-fixed fractures than in the unfixed fractures. The third group was deliberately contaminated with the gram negative organism Proteus mirabilis. In these animals, the infection rate was increased in the presence of the internal fixation device. The fourth group was deliberately contaminated with both Staphylococcus aureus and Proteus mirabilis. The infection rate in these animals was very high; Proteus was recovered from those animals with internal fixation and Staphylococcus was recovered from those animals without internal fixation. These studies in the hamster document the usefulness of this animal as an inexpensive and reproducible model for studying infection of open fractures. The hamsters tolerated the procedure well, and wound and fracture healing progressed satisfactorily.     

Observations of vitamin A toxicity in three patients with renal failure receiving parenteral alimentation

Elevated serum retinol concentrations have been previously reported in patients with renal failure, although overt clinical toxicity has been described only rarely. We present three patients with renal failure receiving total parenteral nutrition (TPN) who developed biochemical and clinical findings of hypervitaminosis A. Improvement followed deletion of vitamin A from the TPN. These cases demonstrate that patients with renal failure may be at risk for symptomatic vitamin A toxicity if given TPN with standard retinol supplementation. Such patients should be carefully observed clinically and biochemically if supplementation is given.