Surface-associated motility, a common trait of clinical isolates of Acinetobacter baumannii, depends on 1,3-diaminopropane

While flagella-independent motility has long been described in representatives of the genus Acinetobacter, the mechanism of motility remains ambiguous. Acinetobacter baumannii, a nosocomial pathogen appearing increasingly multidrug-resistant, may profit from motility during infection or while persisting in the hospital environment. However, data on the frequency of motility skills among clinical A. baumannii isolates is scarce. We have screened a collection of 83 clinical A. baumannii isolates of different origin and found that, with the exception of one isolate, all were motile on wet surfaces albeit to varying degrees and exhibiting differing morphologies. Screening a collection of transposon mutants of strain ATCC 17978 for motility defects, we identified 2 akinetic mutants carrying transposon insertions in the dat and ddc gene, respectively. These neighbouring genes contribute to synthesis of 1,3-diaminopropane (DAP), a polyamine ubiquitously produced in Acinetobacter. Supplementing semi-solid media with DAP cured the motility defect of both mutants. HPLC analyses confirmed that DAP synthesis was abolished in ddc and dat mutants of different A. baumannii isolates and was re-established after genetic complementation. Both, the dat and ddc mutant of ATCC 17978 were attenuated in the Galleria mellonella caterpillar infection model. Taken together, surface-associated motility is a common trait of clinical A. baumannii isolates that requires DAP and may play a role in its virulence.     

The osteoinductive potential of printable, cell-laden hydrogel-ceramic composites

Hydrogels used as injectables or in organ printing often lack the appropriate stimuli to direct osteogenic differentiation of embedded multipotent stromal cells (MSCs), resulting in limited bone formation in these matrices. Addition of calcium phosphate (CaP) particles to the printing mixture is hypothesized to overcome this drawback. In this study we have investigated the effect of CaP particles on the osteoinductive potential of cell-laden hydrogel-CaP composite matrices. To this end, apatitic nanoparticles have been included in Matrigel constructs where after the viability of embedded progenitor cells was assessed in vitro. In addition, the osteoinductive potential of cell-laden Matrigel containing apatitic nanoparticles was investigated in vivo and compared with composites containing osteoinductive biphasic calcium phosphate (BCP) microparticles after subcutaneous implantation in immunodeficient mice. Histological and immunohistochemical analysis of the tissue response as well as in vivo bone formation revealed that apatitic nanoparticles were osteoinductive and induced osteoclast activation, but without bone formation. The BCP particles were more effective in inducing elaborate bone formation at the ectopic location.     

Soil-transmitted helminth and other intestinal parasitic infections among school children in indigenous people communities in Davao del Norte, Philippines

A significant portion of the population in the Philippines consists of indigenous people (IP) groups, approximately 9% or 8.1 million. Data on the health status of these groups are very limited including the status of soil-transmitted helminth (STH) infections. Provision of such data will be of great importance in the formulation of policy on control and prevention of these diseases in this group. This study was conducted in selected villages/barangays in the municipalities of Carmen, Kapalong, San Isidro and Sto. Tomas in the Province of Davao del Norte in Southern Mindanao, Philippines. Parasitologic assessment was performed using Kato-Katz to qualify and quantify STH infections, while nutritional status assessment was based on hemoglobin determination and on nutritional status indicators, i.e., weight-for-age (WFA), height-for-age (HFA), and body mass index (BMI) for age derived from anthropometric measurements. A total of 572 school children participated in the survey, 264 (46.2%) of whom belonged to a specific IP group. Results showed that 34.1% of the school children had at least one STH infection while 5.9% had heavy intensity infections. Cumulative prevalence in IP school children was significantly higher than in non-IP children with rates at 39.0% and 29.9%, respectively (P = 0.021). Overall prevalence of school children with below normal WFA was 29.9%, while prevalence of those with below normal HFA and BMI for age was 42.8% and 14.9%, respectively. Of those examined, 8.3% had below normal hemoglobin levels. There was no significant difference observed between the nutritional status parameters of IP and non-IP school children. The parasitologic parameters reported in this study signify the need to pay more attention to IP children who are at higher risk of morbidity due to helminth infections. Access of IP communities to quality health services, which include mass drug administration (MDA) and health education on a regular basis, must be ensured. Further studies to determine factors that contribute to the higher prevalence of STH among IP groups are recommended.     

Angiopoietin-2 promotes myeloid cell infiltration in a β₂-integrin-dependent manner

In human inflammatory diseases, we identified endothelial angiopoietin-2 (Ang-2) expression to be strongly associated with inflammations mediated by myeloid cells but not lymphocytes. To identify the underlying mechanism, we made use of a transgenic mouse model with inducible endothelial cell-specific expression of Ang-2. In this model, in the absence of inflammatory stimuli, long-term expression of Ang-2 led to a time-dependent accumulation of myeloid cells in numerous organs, suggesting that Ang-2 is sufficient to recruit myeloid cells. In models of acute inflammation, such as delayed-type hypersensitivity and peritonitis, Ang-2 transgenic animals showed an increased responsiveness. Intravital fluorescence video microscopy revealed augmented cell adhesion as an underlying event. Consequently, we demonstrated that Ang-2 is able to induce strong monocyte adhesion under shear in vitro, which could be blocked by antibodies to β?-integrin. Taken together, our results describe Ang-2 as a novel, endothelial-derived regulator of myeloid cell infiltration that modulates β?-integrin-mediated adhesion in a paracrine manner.