Truncated hemoglobins in actinorhizal nodules of Datisca glomerata.

Three types of hemoglobins exist in higher plants, symbiotic, non-symbiotic, and truncated hemoglobins. Symbiotic (class II) hemoglobins play a role in oxygen supply to intracellular nitrogen-fixing symbionts in legume root nodules, and in one case ( Parasponia Sp.), a non-symbiotic (class I) hemoglobin has been recruited for this function. Here we report the induction of a host gene, dgtrHB1, encoding a truncated hemoglobin in Frankia-induced nodules of the actinorhizal plant Datisca glomerata. Induction takes place specifically in cells infected by the microsymbiont, prior to the onset of bacterial nitrogen fixation. A bacterial gene (Frankia trHBO) encoding a truncated hemoglobin with O (2)-binding kinetics suitable for the facilitation of O (2) diffusion ( ) is also expressed in symbiosis. Nodule oximetry confirms the presence of a molecule that binds oxygen reversibly in D. glomerata nodules, but indicates a low overall hemoglobin concentration suggesting a local function. Frankia trHbO is likely to be responsible for this activity. The function of the D. glomerata truncated hemoglobin is unknown; a possible role in nitric oxide detoxification is suggested.

The crystal structure of pneumococcal surface antigen PsaA reveals a metal-binding site and a novel structure for a putative ABC-type binding protein.

BACKGROUND: . The surface protein PsaA of the pathogenic bacterium Streptococcus pneumoniae plays an essential role in its virulence. PsaA is a putative ATP-binding cassette-type (ABC-type) binding protein involved in the uptake of Mn2+ and possibly Zn2+ and is considered to be both a potential drug target and and a candidate vaccine component. RESULTS: . The structure of PsaA has been determined to 2.0 A resolution using X-ray crystallography and is the first structure obtained for an ABC-type binding protein from a Gram-positive organism. The protein consists of two (beta/alpha)4 domains linked together by a single helix. A metal-binding site is formed in the domain interface by the sidechains of His67, His139, Glu205 and Asp280 and is occupied in the structure. CONCLUSIONS: . The structural topology of PsaA is fundamentally different from that of other ABC-type binding proteins determined thus far in that PsaA lacks the characteristic 'hinge peptides' involved in conformational change upon solute uptake and release. In our structure, the metal-binding site is probably occupied by Zn2+. The site seems to be well conserved amongst related receptors from both Gram-positive and Gram-negative bacteria.

Cloning and expression of the pneumococcal neuraminidase gene in Escherichia coli.

A gene bank of Sau3AI-generated Streptococcus pneumoniae DNA fragments was constructed in Escherichia coli K-12 by cloning into the BamHI site of the cosmid vector pHC79. One clone capable of cleaving the fluorogenic neuraminidase substrate 2'-(4-methylumbelliferyl)-alpha-D-N-acetyl-neuraminic acid was isolated. This activity was inhibited by treatment with a mouse antiserum raised against purified pneumococcal neuraminidase. The recombinant plasmid purified from this clone (designated pJCP301) contained approximately 3.0 kb of pneumococcal DNA. Western-blot analysis indicated that E. coli K-12[pJCP301] produced a 98-kDa polypeptide which reacted with antineuraminidase serum.

Molecular analysis of putative pneumococcal virulence proteins.

Although the polysaccharide capsule has been recognized as a sine qua non of virulence, recent attention has focused on the role of pneumococcal proteins in pathogenesis, particularly in view of their potential as vaccine antigens. The contribution of pneumolysin, two distinct neuraminidases, autolysin, hyaluronidase, and the 37 kDa pneumococcal surface adhesin A has been examined by specifically mutagenizing the respective genes in the pneumococcal chromosome and examining the impact on virulence in animal models. The vaccine potential of these proteins has also been assessed by immunization of mice with purified antigens, followed by challenge with virulent pneumococci.

Presence of a small plasmid in clinical isolates of Streptococcus pneumoniae.

We have detected the presence of a small (2.95 kb) plasmid in a clinical isolate of Streptococcus pneumoniae. A restriction map was constructed for this plasmid and for pDP1 (the only previously reported pneumococcal plasmid); no apparent differences were observed and the two plasmids hybridized strongly to each other. Portions of pDP1 were then cloned into Escherichia coli K-12, using the vector pUC19, and the pneumococcal DNA insert was used as a probe to screen 500 clinical isolates of S. pneumoniae for pDP1 sequences. The plasmid was detected in a total of 8 isolates. These were of various serotypes and no correlation could be found between the presence of the plasmid and the geographical location from which it came, the type of infection, or with resistance to antibacterial drugs. Although no function has yet been assigned to pDP1, it may form the basis of a useful vector for cloning in S. pneumoniae, as it contains at least seven unique restriction sites.

A comparison of Listerine® and sodium bicarbonate oral cleansing solutions on dental plaque colonisation and incidence of ventilator associated pneumonia in mechanically ventilated patients: a randomised control trial.

BACKGROUND: Effective oral hygiene has been proposed as a key factor in the reduction of dental plaque colonisation and subsequent development of ventilator associated pneumonia (VAP). Listerine(®) oral rinse, while used extensively in dental practice has rarely been tested in mechanically ventilated patients. Sodium bicarbonate as an oral rinse has been more commonly utilised in oral hygiene regimens in intensive care patients. AIM: To test the efficacies of the essential oil mouth rinse, Listerine(®) (Pfizer) and sodium bicarbonate in the reduction of dental plaque colonisation with respiratory pathogens and the subsequent development of VAP. METHODS: The study design was a prospective, single blind randomised comparative study of adult patients mechanically ventilated for at least 4 days. Patients were randomised to Listerine(®) (Pfizer) oral rinse twice daily, sodium bicarbonate oral rinse 2/24 or sterile water 2/24 (control group). All groups received tooth brushing 3 times a day. Dental plaque colonisation (primary outcome) and incidence of ventilator associated pneumonia (secondary outcome) were studied. RESULTS: Three hundred and ninety-eight patients were randomised to either the Listerine group (127), sodium bicarbonate group (133) or the control group (138). Baseline characteristics were similar for all groups. There were no significant differences between the control and study groups in colonisation of dental plaque at Day 4 (p=0.243). Ventilator associated pneumonia was diagnosed in 18 patients. The incidence was, Listerine(®) group 4.7%, sodium bicarbonate group 4.5% and control 4.3% [OR, 0.99; 95% CI, 0.31 to 3.16; p=0.92]. CONCLUSIONS: Compared to the control group, Listerine(®) or sodium bicarbonate oral rinses were not more effective in the reduction of colonisation of dental plaque or the incidence of VAP. Given the low incidence of VAP, the common factor of a small, soft toothbrush as part of an oral hygiene regimen suggests possible benefit in mechanically ventilated patients.

Effects of three approaches to standardized oral hygiene to reduce bacterial colonization and ventilator associated pneumonia in mechanically ventilated patients: a randomised control trial.

BACKGROUND: Ventilator associated pneumonia remains an important concern in the intensive care unit (ICU). An increasing body of evidence shows that mortality and morbidity can be reduced by implementing a range of preventive strategies, including optimizing oral hygiene. AIM: The aim of this feasibility study was to test two oral hygiene strategies on the effects of microbial colonization of dental plaque with respiratory pathogens (primary outcome) and incidence of ventilator associated pneumonia (secondary outcome). METHODS: A single blind randomised comparative study was conducted in a 20-bed adult intensive care unit in a university hospital. Patients with an expected duration of mechanical ventilation more than 48 h were eligible. Patients were randomised to one of three study regimens (Group A control, second hourly oral rinse with sterile water, Group B sodium bicarbonate mouth wash second hourly, and Group C twice daily irrigations with chlorhexidine 0.2% aqueous oral rinse and second hourly irrigations with sterile water). All study options included cleaning with a toothbrush and non foaming toothpaste. RESULTS: Data from a total of 109 patients were analyzed. Group A 43, Group B 33 and Group C 33 (mean age: 58 ± 17 years, simplified acute physiology score II: 44 ± 14 points). On admission no significant differences were found between groups for all clinical data. While Group B showed a greater trend to reduction in bacterial colonization no significant differences could be demonstrated at Day 4 of admission (p=0.302). The incidence of ventilator associated pneumonia was evenly spread between Groups B and C (5%) while Group A was only 1%. CONCLUSIONS: While a number of studies have advocated the use of various mouth rinses in reducing colonization of dental plaque a standardized oral hygiene protocol which includes the use of mechanical cleaning with a toothbrush may be a factor in the reduction of colonization of dental plaque with respiratory pathogens. This feasibility study provides data to inform future adequately powered studies.