Performance-driven design of Biocompatible Mg alloys

Magnesium (Mg) and its alloys provide numerous benefits as a resorptive biomaterial and present the very real possibility of replacing current metallic implant materials in a variety of roles. The development of suitable biodegradable implant alloys is a multidisciplinary challenge, since alloy design must be confined to a range of alloying additions that are biologically nontoxic, whilst still providing the requisite mechanical properties. This leaves a small number of compatible elements that can provide benefits when alloyed with Mg, including calcium (Ca) and zinc (Zn). To date, although a range of different Mg alloys have been investigated both in vitro and in vivo, little work has been performed to characterize the relationship between the composition of Mg alloys, their corrosion and resulting mechanical properties over time. Consequently it is crucial to understand how these properties may be related if alloys are to be successfully screened for implantation in the body.     

Peptide Programmed Hydrogels as Safe Sanctuary Microenvironments for Cell Transplantation

Cell transplantation is one of the most promising strategies for the minimally invasive treatment of a raft of injuries and diseases. However, a standing challenge to its efficacy is poor cell survival due to a lack of mechanical protection during administration and an unsupportive milieu thereafter. In response, a shear‐injectable nanoscaffold vector is engineered considering the three equal requirements of protection, support, and survival. Here, the programmed peptide assembly of tissue‐specific epitopes presents a safe sanctuary microenvironment for the transplantation of cells. For the first time, a mechanistic understanding of the multifactorial role of the nanoscaffold in promoting cell survival is presented, where initial cell survival is dependent on the fluid mechanic process of droplet formation rather than on shear rate. However, provided is the first report of the most critical component of a transplantation vector, distinguishing feigned biological support from mechanical properties from true ongoing biological support post transplantation. This is achieved via the presentation of amino acid constituents that significantly improve the efficacy of the vector compared to a biocompatible, yet inert analogue. Together, the peptide‐programmed hydrogels enable fundamental rules for the engineering of advanced treatment strategies with wide reaching implications for tissue repair and biofabrication.     

Inhibition of in vitro Salmonella Typhimurium colonization in porcine cecal bacteria continuous-flow competitive exclusion culturest

Continuous-flow (CF) chemostate cultures were used as models to determine the potential usefulness of undefined porcine cecal bacteria as competitive exclusion (CE) cultures against colonization by Salmonella Typhimurium. One culture, pCF1, was derived from cecal bacteria of an animal maintained on antibiotic-free feed, while the other culture, pCF4, was derived from cecal bacteria of an animal maintained on feed containing chlortetracycline. The effectiveness against a chlortetracycline-resistant Salmonella Typhimurium was examined in CF cultures maintained in the absence (pCF1 and pCF4) and presence (cpCFl and cpCF4) of chlortetracycline. CF cultures were inoculated with each of 10(2), 10(4), and 10(6) Salmonella Typhimurium CFU/ml. Chemostat inocula of 10(2) Salmonella CFU/ml resulted in no Salmonella Typhimurium being detected at 2 and 3 days postinoculation in pCF1 and pCF4, respectively, and after 2 days in both cpCF1 and cpCF4. Inoculations of 10(4) Salmonella Typhimurium CFU/ml resulted in clearance from pCF1 and pCF4 within 4 days and within 3 days from cpCF1 and cpCF4. Following inoculation with 10(6) CFU/ml, no Salmonella Typhimurium were detected in all CF cultures by 6 days postinoculation. The results indicated that in vitro CF cultures of porcine cecal bacteria were able to inhibit the growth of Salmonella Typhimurium. The ability to limit Salmonella Typhimurium growth was not restricted by prior exposure of the cecal bacteria to the feed additive chlortetracycline. The present study demonstrates the potential application of CF cultures as models to aid in the identification of CE cultures against salmonellosis in pigs.     

Prevalence of antimicrobial resistance in Salmonellae isolated from market-age swine

Antimicrobial resistance levels were examined for 365 Salmonella isolates recovered from the lymph nodes (n = 224) and cecal contents (n = 141) of market-age swine at slaughter. Antimicrobial resistance testing was performed by disk diffusion using 13 antibiotics common in the treatment of disease in human and veterinary medicine. Although none of the antibiotics tested were used subtherapeutically within the last 5 years on the farms sampled, resistance to chlortetracycline, penicillin G, streptomycin, and sulfisoxazole was common. Penicillin G resistance was significantly more frequent (P = 0.03) and sulfisoxazole resistance was significantly less frequent (P < 0.01) in lymph node versus cecal isolates. Multidrug resistance was observed among 94.7% of the lymph node isolates and 93.5% of the cecal isolates. The most frequent multidrug resistance pattern included three antibiotics-penicillin G, streptomycin, and chlortetracycline. Isolates in somatic serogroup B, and more specifically, Salmonella Agona and Salmonella Schwarzengrund isolates, were often resistant to a greater number of antibiotics than were isolates in the other serogroups. Streptomycin, sulfisoxazole, ampicillin (lymph node isolates), and nitrofurantoin (cecal isolates) resistance levels differed significantly between somatic serogroups. The prevalence of penicillin G-, streptomycin-, and sulfisoxazole-resistant isolates differed significantly between serovars for both lymph node and cecal isolates. Results of this study suggest that a correlation exists between the somatic serogroup or serovar of a Salmonella isolate and its antimicrobial resistance status, which is specific to the antibiotic of interest and the source of the isolate (lymph node versus cecal contents).     

Effect of waste milk pasteurization on fecal shedding of Salmonella in preweaned calves

The objective of the current research was to determine if pasteurization of nonsaleable waste milk influences fecal Salmonella concentrations and prevalence, or antimicrobial susceptibility and serotype of the cultured isolates. Holstein dairy calves (n = 211) were housed on a single commercial dairy in the southwestern United States and randomly allotted to be fed either pasteurized (PWM; n = 128 calves) or nonpasteurized waste milk (NPWM; n = 83 calves). Fecal samples were collected via rectal palpation or from freshly voided, undisturbed fecal pats, weekly during the first 4 wk of the animal's life and then again at weaning. Eight total collections were made and 1,117 fecal samples cultured for Salmonella. One isolate from each culture-positive fecal sample was preserved for antimicrobial susceptibility screening and serotyping. Sixty-nine percent of the fecal samples were culture positive for Salmonella with no difference due to treatment (67.7 and 69% Salmonella positive for PWM and NPWM treatments, respectively). Few fecal samples (178/1,117; 15.9%) contained Salmonella concentrations above the limit of detection (～1 cfu/g of feces) with concentrations ranging from 1.0 to 6.46 cfu (log₁₀)/g of feces. Concentration was not affected by treatment. Seventeen different serotypes were identified, the majority of which were Montevideo and Anatum. A greater percentage of Typhimurium (87 vs. 13%), Muenchen (88 vs. 12%), and Derby (91 vs. 9%) were recovered from calves fed PWM compared with NPWM-fed calves. Conversely, Newport (12.5 vs. 86%), Bredeney (22.2 vs. 77.8%), and Muenster (12.5 vs. 87.5%) were lower in PWM compared with NPWM treatments. The majority (66.7%) of isolates were susceptible to all of the antibiotics examined. Results from this one commercial dairy suggest that milkborne Salmonella is not an important vector of transmission in dairy neonates, nor does pasteurization of waste milk influence fecal shedding of this pathogen. Caution should be used, however, when extrapolating results to other farms as Salmonella contamination of milk on farm is well documented. The potential benefits of pasteurization in disease prevention outweigh the potential risks of feeding a nonpasteurized product and warrants incorporation into any calf-rearing program using nonsaleable waste milk for feeding young dairy neonates.     

Prevalence of Escherichia coli O157 in cattle and swine in central Mexico

Escherichia coli O157:H7 is a foodborne pathogenic bacterium that can reside undetected in the gastrointestinal tract of cattle because colonization by this bacterium is asymptomatic. Recent research has indicated that swine can carry and transmit this pathogen as well. The development of more advanced and sensitive detection techniques has improved the limit of detection and increased sensitivity for this important pathogen. This study was undertaken to determine the prevalence of E. coli O157 in cattle and swine in Mexico with the more sensitive detection technique of immunomagnetic bead separation. Samples (n = 60 per farm) were taken from four cattle and four swine farms (n = 240 cattle samples, n = 240 swine samples) located throughout central Mexico in October 2001. The prevalence of E. coli O157 was found to be only 1.25% on cattle farms and 2.1% on swine farms. The prevalence in cattle in this study is lower than that reported in the United States and could be related to the lower reported prevalence of E. coli O157 in humans in Mexico. However, further research is needed to verify prevalence throughout other regions of Mexico, as well as prevalence during other seasons of the year.     

A critical evaluation of the strategy project

The STRATEGY project (sustainable restoration and long-term management of contaminated rural, urban and industrial ecosystems; www.strategy-ec.org.uk) addressed the need for a holistic decision framework for the selection of optimal remediation strategies for long-term sustainable management of contaminated areas in Western Europe. The project considered both technical and social aspects of implementing restoration strategies for urban and rural environments. The importance of considering socially relevant objectives in addition to the dose reduction was emphasised. A critical evaluation was carried out on 101 selected countermeasures, (including rural waste disposal options), a model was developed to aid optimising countermeasure strategies and a method of carrying out participatory decision-making suggested. The outputs of the project are described and critically evaluated.     

Response in the late phase to a radiological emergency

This paper looks at the key issues that need to be addressed during the transition from the emergency phase to the late phase of a radioactive release, and the development of the initial late phase strategy. It discusses the extent to which current national plans and international advice address the needs of decision makers following contamination of inhabited areas and food production systems. Based on this the following recommendations are made: (1) the issues that will arise at the start of the late phase response to a radioactive release require preparation work in advance of any release; (2) this preparation should consider the adequacy of legislation, technical data and modelling, options for waste storage and disposal, resources for monitoring and implementing clean up; (3) late phase preparedness requires regular exercising and (4) the possibility of terrorist releases adds further emphasis to the need for preparedness for the late phase.