AN ELECTROCHEMICAL MICROFLUIDIC BIOSENSOR PLATFORM FABRICATED BY ADDITIVE MANUFACTURING AND SUPERSONIC CLUSTER BEAM DEPOSITION

Fused Filament Fabrication (FFF) three-dimensional printing have attracted much attention for fabrication of microfluidic platforms used to construct electrochemical microfluidic biosensors because of high process speed, low production costs and the possibility of manufacturing directly from virtual data. Because of poor adhesion between metal electrodes fabricated using conventional techniques and FFF printed thermoplastic substrates, electrodes are usually integrated into the devices either modularly or using adhesive layers placed at the bottom of fluidic channels. These have hindered the exploitation of FFF for scale-up manufacturing of monolithically integrated microfluidic biosensors. In this work, supersonic cluster beam deposition (SCBD) was employed to fabricate strongly anchored nanostructured electrodes integrated into FFF printed microfluidics platforms. SCBD enables the formation of well-adhering metallic thin film electrodes by implanting supersonically accelerated neutral metal clusters into polymeric substrates. The SCBD also enables deposition over large areas using noble metals and metal oxides with precisely controlled geometry and surface topography. A novel integrated manufacturing approach was developed and optimized to couple SCBD fabricated electrodes with consumer-grade FFF printed microfluidics, employing acrylonitrile butadiene styrene as the base material, to develop a three electrodes configuration electrochemical sensor on-a-chip. Electrochemical investigation performed using stagnant ferro/ferricyanide probe showed that the integrated device possesses high sensitivity and functionality as an electrochemical sensor. In addition, in-channel laminar flow electrochemical detection conducted using the same probe showed robust stability in the system response for online dynamic detection. The integrated platform could be employed for various customized clinical, industrial, and environmental sensing applications

Molecular Characterization of Multidrug Resistant Salmonella Isolates From Food Animals and Animal Products in Tanzania

Food animals are major sources of human salmonellosis. Animals raised for food play an important role in transmission of antimicrobial resistant Salmonella strains to humans. The aim of this study was to determine the antimicrobial resistance profile, the occurrence of class 1 integrons and the resistance gene cassettes mobilized in the class 1 integrons of Salmonella isolates. A cross-sectional design was carried out in pastoral regions of Tanzania with large population of livestock. Salmonella isolates were recovered from 4.2% of the total of 1540 samples from apparently healthy animals and the animal products. The results showed that Salmonella isolates were detected in 5.2%, 3.7% and 3.8% of the swine, cattle and chicken, respectively. Sixty-one Salmonella isolates belonged to Salmonella enterica subsp. enterica. Predominant serotypes were Salmonella I 8,20:i:- (32.8%), S. Hadar (10.9%), S. Colindale (6.3%), S. Anatum (6.3%) and S.  Heidelberg (6.3%). S.  I 8,20:i:- isolates were widespread in different samples from different food animals. Of 64 Salmonella isolates, about 35.9% were resistant to at least one antimicrobial, whereas, 82.6% were multi-drug resistant (MDR) Salmonella. About 8.7% of the MDR Salmonella isolates were found to also carry integrons (intI1) and 100% of intI1-positive isolates contained resistance gene cassettes known as aac(3)-Id-aadA7 showing high rate of MDR. The occurrence of clonal MDR Salmonella isolates in food animals and animal products from pastoral communities indicates the high significance of informal traditional sector as an important source of foodborne pathogens in the food chain and the entry of pathogens to the pastoralist communitie