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Background and Aim: The emergence of antimicrobial resistance (AMR) in commensal organism, such as Escherichia coli of food animals, is an alarming issue for global health. It increases the possibility of transmitting AMR determinant(s) to human bacterial pathogens by transferable genetic materials, particularly by plasmids. Hence, it is important to know which resistant genes are being carried by commensal organisms in food chain in a country and their level of temporal loads. As a result, pre-emptive measures can be advocated with an aim to reduce their risks in their primary source of circulation which consequently would benefit the public health. Materials and Methods: Commensal E. coli strains from broiler chickens on randomly selected 30 farms and the farm environments were examined for the frequencies of isolation of resistant strains to oxytetracycline and ciprofloxacin. Five birds were randomly selected from each farm to collect cloacal swab samples (total of 150 samples). Furthermore, a total of 150 environmental samples comprising one each from feed, water, soil, litter, and litter damping site of each farm were screened for the isolation of commensal E. coli strains. Strains thus obtained were initially tested for their resistance to oxytetracycline and ciprofloxacin by Kirby–Bauer disk diffusion method. Oxytetracycline-resistant strains were further screened for the presence of resistance determining genes, namely, tetA, tetB, and tetC by uniplex polymerase chain reactions. Risks associated with the isolation frequency of oxytetracycline- and ciprofloxacin-resistant E. coli were also assessed by univariable logistic regression analysis. Results: The results revealed that all E. coli isolates, regardless of the source of origin, were resistant to oxytetracycline, while 78.4% (95% confidence interval [CI] 69.1-85.5%) showed resistance to ciprofloxacin. All the randomly selected (20) oxytetracycline-resistant strains harbored the tetA gene, whereas tetB and tetC were reported in three and two isolates, respectively. After univariable analysis, only one variable, that is, strain 1 of broiler chickens compared to two other strains was found to be positively associated with the isolation of ciprofloxacin-resistant E. coli (odds ratio 12.75 [95% CI 1.0- 157.1], p=0.047). Conclusion: Resistance emerged against oxytetracycline and ciprofloxacin in commensal E. coli strains circulating in live poultry and farm environments in Bangladesh seems to be very high. Thus, human infection with drug-resistant E. coli strains through food chain will critically compromise the therapeutic measures currently available.

Background and Aim: Newcastle disease is one of the most common diseases affecting poultry in Bangladesh. The disease can cause up to 100% mortality but is preventable if birds are timely and properly vaccinated with a vaccine of standard virus titer. Different live vaccines are commercially available in the country - most, if not all, are produced using lentogenic strains of the virus with variable virulence. One of the disadvantages of these vaccines is that they are not stable at high environmental temperature, and therefore, a proper cold chain must be maintained during transportation and storage. Information on how long these vaccine viruses can withstand environmental temperature, which is near the vicinity of 37°C in the summer season in Bangladesh, is scanty. The aim of this research was to measure the effect of temperature on virus titer of live ND virus vaccines and to develop a real-time reverse transcription polymerase chain reaction (rRT-PCR) standard curve to indirectly determine hemagglutination (HA) titer of virus by this highly sensitive method. Materials and Methods: In this study, thermostability of five commercial live vaccines containing LaSota, F, Clone 30, and B1 type LaSota strains was observed for up to 35 days keeping them at 37°C. From the most thermostability yielding sample, two rRT-PCR standard curves were developed: (1) By plotting the cycle threshold (CT) values as obtained from 10-fold serial dilutions up to 10-3 against their corresponding log (to the base 10) dilutions and (2) by plotting the CT values obtained from serial HA dilutions up to 2-4 against their corresponding HA titer dilutions. The PCR efficiencies based on which the graphs were fitted were also evaluated. Results: The vaccine from the LaSota strain withstood 37°C for 35 days with a gradual declination of HA titer over time, and this vaccine also had the highest initial HA titer, which was 211. The vaccine made from F strain was inactivated quickly, and it had the lowest HA titer at the beginning of the study. The first standard curve developed can be used to assess the level of virus titer in a diluted sample compared with the titer in the original undiluted vaccine preparation by plotting the CT value obtained from the dilution by rRT-PCR. The second standard curve can be used to calculate the HA titer of a vaccine dilution by plotting the CT value as obtained from the dilution by rRT-PCR. Conclusion: The regression equations for the first and second graphs were y=–3.535x+14.365 and y=–1.081x+13.703, respectively, suggesting that, for every 3.53 cycles, the PCR product would have increased 10 times and 2 times for every 1.08 cycles, respectively, indicating nearly (but not exactly) 100% PCR efficiency.