Biology subjects

Ray, A. P.

Publications and source records attributed to Ray, A. P..

4 recordsLinked to original sources

bioRxiv2026

Identification and Antibiogram Assay of Escherichia coli Isolated from Chicken Eggs

BackgroundEscherichia coli contamination of chicken eggs is an important food-safety concern, while antimicrobial-resistant E. coli may contribute to the dissemination of antimicrobial resistance through the food chain. However, information on egg-associated E. coli and its antimicrobial susceptibility in Natore District, Bangladesh, is limited. ObjectivesThis study aimed to determine the prevalence of E. coli in chicken eggs collected from commercial farms, markets and indigenous/backyard flocks in Natore District, identify the isolates based on cultural, morphological and biochemical characteristics, and assess their antimicrobial susceptibility. Materials and MethodsA total of 84 egg-shell swab samples, comprising 28 samples each from commercial farms, markets and indigenous chicken flocks, were collected from seven upazillas of Natore District between January and June 2023. Samples were cultured on selective and differential media, and presumptive isolates were confirmed by Gram staining, motility and biochemical tests. Antimicrobial susceptibility was determined using the Kirby-Bauer disc-diffusion method against seven antimicrobial agents. ResultsE. coli was detected in 56/84 (66.67%) egg samples. Prevalence was highest in indigenous eggs (22/28, 78.57%), followed by farm eggs (18/28, 64.28%) and market eggs (16/28, 57.14%). Among 22 confirmed isolates tested for antimicrobial susceptibility, resistance was highest to neomycin (90.91%) and erythromycin (86.36%), followed by oxytetracycline (77.27%), amoxicillin (68.18%), ciprofloxacin (63.63%), levofloxacin (59.09%) and doxycycline (36.36%). No isolate was sensitive to neomycin or erythromycin. ConclusionThe high prevalence of E. coli and substantial antimicrobial resistance among egg-associated isolates indicate an important food-safety and public-health concern. Improved hygienic egg handling, prudent antimicrobial use and continued antimicrobial-resistance surveillance are warranted throughout the poultry production and marketing chain.

microbiology↗

bioRxiv2026

Isolation, Identification and Antibiogram Assay of Escherichia coli from the Environment of Live Bird Markets in Bangladesh

BackgroundLive bird markets (LBMs) may facilitate the persistence and dissemination of Escherichia coli and antimicrobial-resistant bacteria because of intensive bird handling, environmental contamination and inadequate sanitation. However, information on E. coli contamination and antimicrobial susceptibility in LBM environments in Rajshahi District, Bangladesh, remains limited. ObjectiveThis study aimed to determine the prevalence, identify the cultural and biochemical characteristics, and assess the antimicrobial susceptibility pattern of E. coli isolated from water, soil and bird-dropping samples collected from LBMs in Rajshahi District. MethodsA total of 60 environmental samples, comprising 20 water, 20 soil and 20 bird-dropping samples, were collected from LBMs across all ten upazillas of Rajshahi District between January and June 2023. E. coli was isolated and identified using cultural characteristics, Gram staining and biochemical tests. Antimicrobial susceptibility was determined by the Kirby- Bauer disc diffusion method against seven antimicrobial agents using CLSI interpretive criteria. ResultsE. coli was detected in 33 of 60 samples, giving an overall prevalence of 55.00%. Prevalence was highest in bird-dropping samples (75.00%), followed by water (55.00%) and soil (35.00%). Among the 33 isolates, resistance was highest to oxytetracycline (78.79%) and amoxicillin (63.64%), followed by ciprofloxacin (48.48%), doxycycline (33.33%), levofloxacin (9.09%), erythromycin (9.09%) and neomycin (6.06%). Sensitivity was highest to neomycin (60.61%), followed by levofloxacin and erythromycin (51.51% each). ConclusionThe high prevalence of E. coli and substantial resistance to several commonly used antimicrobials indicate considerable microbiological and antimicrobial-resistance concerns in LBM environments. Improved sanitation, biosecurity, hygienic poultry handling and prudent antimicrobial use are warranted to reduce environmental contamination and potential transmission of resistant bacteria.

microbiology↗

bioRxiv2026

Molecular Detection and Antibiogram Assay of Escherichia coli Isolated from Poultry Farm Environments

BackgroundEscherichia coli is a common environmental and zoonotic bacterium that serves as an important indicator of fecal contamination and antimicrobial resistance (AMR) in poultry production systems. The emergence of multidrug-resistant (MDR) E. coli in poultry farm environments poses a significant One Health threat to animal, human, and environmental health. ObjectiveThis study aimed to isolate, identify, determine the prevalence, assess the antibiotic susceptibility pattern, and molecularly confirm Escherichia coli isolated from poultry farm environments in Lalmonirhat district, Bangladesh. Materials and MethodsA cross-sectional study was conducted from January to June 2024 using 60 environmental samples comprising water (n = 20), soil (n = 20), and bird-dropping (n = 20) samples collected from poultry farms in five upazilas of Lalmonirhat district. Isolation and identification of E. coli were performed using standard cultural, morphological, and biochemical techniques. Antimicrobial susceptibility was determined by the Kirby-Bauer disc diffusion method following CLSI guidelines. Ten randomly selected isolates were confirmed by polymerase chain reaction (PCR) targeting the species-specific uidA gene. ResultsThe overall prevalence of E. coli was 50% (30/60). Source-wise prevalence was highest in bird-dropping samples (75%), followed by water (45%) and soil (30%). Area-wise prevalence ranged from 33.33% in Patgram to 66.67% in Hatibandha. The isolates exhibited the highest resistance to oxytetracycline (66.67%) and ciprofloxacin (60%), while the highest susceptibility was observed to erythromycin (63.33%), neomycin (56.67%), and amoxicillin (56.67%). All ten isolates subjected to PCR produced the expected 486 bp uidA gene amplicon, confirming their identity as E. coli. ConclusionThe findings demonstrate a considerable prevalence of antimicrobial-resistant E. coli in poultry farm environments of Lalmonirhat district. Strengthening farm biosecurity, improving hygiene and waste management, implementing antimicrobial stewardship, and maintaining continuous molecular surveillance are essential to minimize the dissemination of resistant E. coli within a One Health framework.

microbiology↗

bioRxiv2026

Spatial Organization of Lipids Drives GPCR Conformational Equilibria

Despite the widespread use of lipid nanodiscs for structure-function studies of membrane proteins, little is known about how lipids are spatially organized within nanodiscs and how this organization influences embedded proteins. The activity and conformational equilibria of the human A2A adenosine receptor, a class A G protein-coupled receptor, are highly sensitive to anionic lipids that directly interact with the receptor. We leverage this lipid-dependent sensitivity to probe the accessibility of anionic lipids across nanodiscs of varying sizes. We identify a threshold concentration of anionic lipids required to fully populate active receptor conformations that is higher for POPS than for POPG. Computational simulations reveal that POPS and POPG each form lipid clusters reducing the effective availability of anionic lipids to interact with the receptor. This effect is stronger for POPS and scales with increasing nanodisc size, correlating with experimental biophysical and biochemical measurements. Simulations further identify positively charged residues within the membrane scaffold protein that coordinate anionic lipid headgroups. Targeted protein engineering reduces the threshold concentration of anionic lipids required for receptor activation, supporting strategies to control lipid accessibility within nanodiscs. Because membrane scaffold proteins are derived from apolipoprotein A-I, similar lipid-protein interactions may also influence lipid organization within biological systems such as HDL particles.

biophysics↗