Determination of ciprofloxacin and nalidixic acid resistance in Campylobacter jejuni with a fluorogenic polymerase chain reaction assay

A fluorogenic polymerase chain reaction assay for the gyrA gene was used to determine the frequency of a Thr-86 mutation in Campylobacter jejuni isolates from food animals and humans in northern Thailand and to investigate the correlation between this mutation and bacterial resistance to fluoroquinolones. Eighty-four isolates of C. jejuni were used: 65 from healthy chickens on farms, 16 from chickens at the slaughterhouse, 1 from chicken meat at the market, and 1 from a healthy farm worker. The microbroth dilution technique was used for in vitro susceptibility testing. MIC breakpoints established by the National Antimicrobial Resistance Monitoring System were used to categorize the resistance of C. jejuni to ciprofloxacin and nalidixic acid. Sixty of the 84 C. jejuni isolates tested carried the Thr-86 mutation in the gyrA gene. All isolates with ciprofloxacin MICs of > or = 2 mg/liter carried the mutation, and no isolates with nalidixic acid MICs of < or = 16 mg/liter carried the Thr-86-to-Ile mutation. There was a very strong association between ciprofloxacin resistance and the presence of the mutation (kappa = 0.971, P < 0.01). The association between the presence of the Thr-86-to-Ile mutation and nalidixic acid resistance was weaker (kappa 0.859: P < or = 0.01).     

Salmonella in food animals and humans in northern Thailand

A study was conducted to describe the epidemiology of Salmonella spp. in chickens, pigs, dairy cows, farm workers with and without livestock contact, and children with diarrhea. Samples were collected in the Chiangmai and Lampoon provinces of northern Thailand during 2000-2003. A total of 2141 samples were processed. The prevalences of Salmonella in chickens at the farm, slaughterhouse and chicken meat at the market were 4%, 9% and 57%, respectively. In pigs, the prevalence at the farm, slaughterhouse and pork at the market were 6%, 28% and 29%, respectively. The prevalence of Salmonella in dairy cows was 3%. Salmonella was isolated from 36% of farm workers with livestock contact and 33% of those with no livestock contact, and from 7% of diarrheal children at the hospital. The longitudinal study of Salmonella in pigs showed that the incidences of Salmonella isolation at the farm, slaughterhouse, and market were 7%, 50% and 20%, respectively. The most frequently isolated serotypes of Salmonella were Weltevreden in chickens and humans, and Rissen in pigs. Serotypes varied between farm, slaughterhouse and market for isolates from chickens and pigs. Antimicrobial resistance was present in isolates from all types of animals and humans in the study, with widespread resistance to tetracycline and nalidixic acid. The proportions of resistant organisms among Salmonella from diarrheal children were high, and higher proportions of multi-drug resistant organisms were observed among Salmonella isolates from farm workers with livestock contact than among isolates from workers with no livestock contact.     

A prediction of defluidization time in biomass fired fluidized bed combustion

Two mathematical models to describe the complete defluidization time in biomass FBC were presented in this study; one was newly developed and another was a modified model. They considered the effects of the chemical properties of fuel ash and bed operating conditions such as air velocity, bed particle size and static bed height. The model formulations employed the approach of force balance, defining the viscous flow sintering and the gas bubble behaviors to evaluate the adhesive and segregated forces, respectively. The models were achieved by the statistical regression analyzes with the early laboratory scale experimental results and then verified by the pilot scale experimental results and previous published data. The regression analyzes revealed that the inorganic composition of ash in the fuel and temperature were most significant. In addition, the fluidizing velocity showed a strong effect among the observed operating variables. The model predictive results followed the lab scale data with the error range of ±22% and ±35% and provided fairly well predictability with the pilot scale and published data of previous bed agglomeration tests, carried out with several kinds of biomass fuels.     

Camera operation estimation from video shot using 2D motion vector histogram

Multimedia Tools and Applications - This paper presents a novel technique for classifying several camera operations in videos. First of all, we obtain a series of 2D motion vector (MV) fields by...     

Campylobacter in food animals and humans in northern Thailand

Cross-sectional, longitudinal, and case-control studies were conducted to describe the epidemiology of Campylobacter in chickens, swine, dairy cows, farm workers, nonfarm residents, and children with diarrhea. Samples were collected in Chiang Mai and Lamphung provinces of northern Thailand from 2000 through 2003. A total of 2,360 samples were processed. Results from the cross-sectional study indicated that the prevalences of Campylobacter in chickens at the farm, slaughterhouse, and market were 64, 38, and 47%, respectively. In swine, the prevalences at the farm, slaughterhouse, and market were 73, 69, and 23%, respectively. Campylobacter prevalence was 14% in dairy cows and 5% in raw milk. The prevalence of Campylobacter on farms was lower in environmental samples than in samples collected from live animals. No Campylobacter isolates were obtained from healthy nonfarm residents, but isolates were obtained from 5 and 18% of farm workers and children with diarrhea, respectively. The prevalence of Campylobacter in pigs in the longitudinal study was 61% at the farm, 46% at the slaughterhouse, and 33% at the market. The majority of Campylobacter isolates from chickens (52%), swine (98%), and farm workers (66%) were Campylobacter coli, whereas the majority of isolates from dairy cows (63%) and children with diarrhea (62%) were Campylobacter jejuni. Most Campylobacter isolates from diarrheal children had single-strand conformation polymorphism profiles similar to those of isolates from chickens. None of the risk factors for infection in children with diarrhea were significantly associated with the isolation of Campylobacter.     

Heat transfer in a crater bed

The aim of this work is to study heat transfer in a laboratory scale crater bed, which was set up from a cylindrical acrylic/quartz tube, using sand as the bed particle. The bed employs a downward gas jet from a nozzle which causes the particles to ascend fountain-like into the freebroad, leaving a crater on the bed surface. After reaching a certain height, these particles will descend again to the bed surface and move into the crater, where the cycle or circulation pattern starts again. The study had been separated into three parts. Firstly, the void fraction of the bed fountain zone was studied by direct measurement of the ascending sand weight within the specific volume. Secondly, the convection heat transfer coefficients between the fountain zone and the external surface of the gas inlet tube were determined by measuring the quantity of heat loss from an electrical heater that was wrapped on the outside surface at desired positions of the gas inlet tube. Thirdly, the radiation heat transfer coefficients were evaluated by heat balance of LPG combustion in the crater bed. From experimental results, the void fraction of the fountain zone could be approximated as a dilute bed (>0.98). For convective heat transfer coefficients, the value found experimentally varied from 80–260 W/m² K depending on the experimental conditions, showing an increase when the gas velocity increases, and a decrease along the height of the gas inlet tube. Radiation heat transfer coefficients, the values of which are (within the experimental temperature range), the same order as the convective mode, increase when the bed temperature is increased and when the bed particle diameter is decreased. Empirical correlations for both bed voidage and heat transfer coefficients are proposed. The combined model, gas and particle convection and the published data on radiation heat transfer, showed good prediction when compared with experimental data.     

Identification of Campylobacter jejuni isolates from cloacal and carcass swabs of chickens in Thailand by a 5' nuclease fluorogenic polymerase chain reaction assay

A rapid 5' nuclease fluorogenic polymerase chain reaction (PCR) assay for identifying Campylobacter jejuni was applied to Campylobacter isolates from chicken cloacal and carcass swabs collected from three chicken farms and a slaughterhouse in Thailand. The primers and the probe were based on the sequence of the gyrA gene in C jejuni. C. jejuni isolates were identified by fluorogenic PCR assay of bacterial cells directly from Campylobacter-selective agar medium. This assay allowed the identification of C. jejuni within 1 day after colonies appeared on selective media. The fluorogenic PCR assay yielded results comparable to those of the conventional test kit (kappa = 0.76) but required less time. When the two methods disagreed with regard to species identification, results were confirmed by PCR restriction fragment length polymorphism of 23S rRNA genes. In these instances, the fluorogenic PCR assay correctly identified more isolates of C. jejuni than did the conventional test kit (six of seven isolates were unidentifiable by the conventional test kit). The fluorogenic PCR assay is a rapid and specific method that outperforms the conventional test kit in the identification of C. jejuni from environmental samples.     

Optimizing the early detection of low pathogenic avian influenza H7N9 virus in live bird markets

In Southeast Asia, surveillance at live bird markets (LBMs) has been identified as crucial for detecting avian influenza viruses (AIV) and reducing the risk of human infections. However, the design of effective surveillance systems in LBMs remains complex given the rapid turn-over of poultry. We developed a deterministic transmission model to provide guidance for optimizing AIV surveillance efforts. The model was calibrated to fit one of the largest LBMs in northern Vietnam at high risk of low pathogenic H7N9 virus introduction from China to identify the surveillance strategy that optimizes H7N9 detection. Results show that (i) using a portable diagnostic device would slightly reduce the number of infected birds leaving the LBM before the first detection, as compared to a laboratory-based diagnostic strategy, (ii) H7N9 detection could become more timely by sampling birds staying overnight, just before new susceptible birds are introduced at the beginning of a working day, and (iii) banning birds staying overnight would represent an effective intervention to reduce the risk of H7N9 spread but would decrease the likelihood of virus detection if introduced. These strategies should receive high priority in Vietnam and other Asian countries at risk of H7N9 introduction.