Biology subjects

Azad, M. A. K.

Publications and source records attributed to Azad, M. A. K..

7 recordsLinked to original sources

bioRxiv2026

Knowledge, Attitudes and Practices (KAP) of Cat Owners Towards Flea Infestation and Flea-Borne Diseases (FBDs) in Selected Regions of Bangladesh

Background: Flea infestation is an important companion-animal health problem and a prime source of zoonotic exposure. However, information on cat owners awareness and preventive behavior regarding fleas and flea-borne diseases (FBDs) in Bangladesh is limited. This study assessed the knowledge, attitudes and practices (KAP) of cat owners regarding flea infestation and flea-borne diseases in selected areas of central Bangladesh. Methods: A cross-sectional survey was conducted from November 2025 to July 2026 among 238 cat owners attending veterinary clinics in Savar, Dhamrai and Manikganj Upazila. Data were collected using a pretested structured questionnaire covering respondent characteristics, flea biology and transmission, perceived risks, and flea-prevention and control practices. Descriptive statistics were used to summarize the findings, and respondents were classified according to their overall KAP scores. Results: Of the respondents, 47.1% owned cats with outdoor access and 77.7% reported that their pets had previously experienced flea infestation. Although 65.5% used flea-control treatments, awareness of zoonotic and disease-transmission risks was limited. Only 14.7% recognized that fleas can parasitize humans, while 17.6% knew that fleas can transmit infectious agents. Overall, 83.2% of respondents had poor knowledge, whereas 69.7% demonstrated moderate attitudes and 63.9% showed moderate practices. Good knowledge and good practice were uncommon, accounting for only 3.8% and 4.6% of respondents, respectively. Veterinary recommendation was the most frequently reported motivation for using flea-control products. Conclusions: Cat owners attending in the surveyed areas frequently reported flea exposure and treatment use, but substantial gaps remained in their understanding of flea biology, zoonotic potential and comprehensive control. Targeted veterinary education emphasizing routine prevention, treatment of all susceptible household animals and environmental management is needed. These findings provide regional baseline evidence and should not be interpreted as nationally representative. Keywords: Bangladesh; cat owners; ectoparasites; flea-borne diseases; flea control; knowledge, attitudes and practices; One Health.

scientific communication and education↗

bioRxiv2026

The structure-interaction model of polymyxin lipopeptides with human oligopeptide transporter 2

Multidrug-resistant (MDR) Gram-negative bacteria pose a critical global health threat, while polymyxins remain a last-line therapy. However, their clinical use is limited by nephrotoxicity. Human oligopeptide transporter 2 (hPepT2) is a membrane transporter mediating the reabsorption of polymyxins in renal cells and contributes to their nephrotoxicity, but the molecular basis of their interaction remains unclear. Here, we investigated the structure-interaction relationship (SIR) of polymyxins with hPepT2 by integrating computational, chemical, and cell biology approaches. Bioinformatic modelling predicted an outward-facing hPepT2 structure and a potential transport pathway, with polymyxins interacting at the lateral opening, particularly E214, D215, D317, D342, and E622. Transporter mutagenesis and molecular analyses confirmed that D215 is critical for polymyxin binding, while other residues influence transporter turnover and/or expression. We subsequently synthesised polymyxin analogues with modifications at Dab1, Dab3, Dab5, and Dab9 of polymyxins, which reduced interactions with hPepT2. Notably, alanine substitution at Dab3 reduced nephrotoxicity in mice while retaining antibacterial activity. Overall, this proof-of-concept study demonstrates that the hPepT2-polymyxin SIR model provides a viable strategy for developing novel, safer lipopeptide antibiotics.

biochemistry↗

bioRxiv2026

Integrated physiological performance and Nax1-mediated sodium exclusion reveal mechanisms of salinity tolerance in spring wheat (Triticum aestivum L.)

Soil salinity is a rapidly intensifying abiotic stress that significantly limits wheat productivity, particularly in coastal and irrigated agroecosystems. Although sodium (Na+) ion exclusion has been recognized as a key tolerance mechanism, the integration of physiological performance with Nax1-mediated molecular regulation among regionally adapted wheat genotypes remains insufficiently characterized. The present study aimed to dissect salinity tolerance by combining hydroponic phenotyping, multivariate trait analysis, molecular marker profiling, and quantitative expression analysis of the Na+ ion transporter gene Nax1. Seventeen spring wheat genotypes were evaluated under four salinity levels (0.0, 10, 12, and 14 dS m-{superscript 1}). Germination and survival rate, shoot and root growth, and biomass accumulation were measured. Principal component analysis (PCA) and hierarchical clustering were performed to classify genotypes, while SSR (simple sequence repeat) and Nax-linked markers assessed genetic diversity. Relative Nax1 expression was quantified using qRT-PCR (quantitative real-time polymerase chain reaction). Salinity significantly reduced germination, survival, elongation, and biomass, with strong genotype-dependent variation. Multivariate analyses clearly separated tolerant and sensitive genotypes, with biomass retention and survival contributing most to total variation. Marker analysis revealed moderate genetic polymorphism. Notably, tolerant genotypes exhibited 3-6-fold induction of Nax1 under severe salinity, positively correlating with biomass maintenance. These findings demonstrate that salinity tolerance in wheat is associated with coordinated physiological resilience and enhanced Nax1-mediated Na ion exclusion, thereby advancing mechanistic understanding and supporting molecular-assisted breeding for salt-affected environments.

plant biology↗

bioRxiv2025

Characterisation of SpoT-disruption induced metabolic shift in bacteria

SpoT, a pivotal stringent response regulatory enzyme, serves a dual function of both synthesizing and hydrolyzing the stress alarmones ppGpp and pppGpp, collectively known as (p)ppGpp. These alarmones act as global regulators, governing bacterial metabolic and physiological adaptation to diverse environmental stresses. Our previous investigation revealed that multidrug-resistant Acinetobacter baumannii notably upregulates SpoT in response to polymyxin treatment. Intriguingly, disrupting spoT gene enhances polymyxin killing. To comprehend SpoT metabolic regulatory function in mediating polymyxin tolerance, we conducted untargeted metabolomics, comparing metabolic perturbations upon polymyxin B (PMB) treatment between a spoT-disrupted A. baumannii mutant and its wild-type counterpart. Depletion of guanine-based purines GTP and GDP in the PMB-treated spoT-disrupted mutant suggests impaired (p)ppGpp hydrolysis, potentially leading to lethal accumulation of these molecules. PMB also induced more pronounced depletion of carbon sources (i.e., phosphoenolpyruvate, succinate, coenzyme A), energy metabolites (i.e., NADH biosynthesis pathway, ADP), amino acids, and the antioxidative system (i.e., glutathione, gamma-L-glutamyl-L-cysteine, (R)-S-lactoylglutathione) in the spoT-disrupted mutant. Interestingly, a distinctive time-dependent perturbation of fatty acyls was also observed following polymyxin treatment, with multiple fatty acyl conjugates significantly elevated in the spoT-disrupted mutant at 1 hour. However, this situation reversed at 4 hours, with more elevated fatty acyl groups in the wild-type compared to the spoT-disrupted mutant, indicating greater and more rapid PMB-induced membrane disruption in the spoT-disrupted mutant. Collectively, our findings suggest a potential role for SpoT in intricately coordinating A. baumannii energy expenditure and metabolite repertoire to ensure optimal functionality in stress tolerance and repair machineries (e.g., glutathione system, fatty acid regulation) following polymyxin treatment. IMPORTANCEPolymyxins, the last-resort antibiotics for multidrug-resistant Gram-negative bacteria, face increasing challenges due to growing tolerance. To tackle Acinetobacter baumannii polymyxin tolerance, we turned to SpoT, a (p)ppGpp synthetase/hydrolase protein. Our study focused on spoT-disrupted mutant, which exhibited heightened polymyxin antibacterial killing, yet the underlying mechanisms remained elusive. Through metabolomics, we unraveled key insights. Enhanced polymyxin killing in spoT-disrupted mutant likely resulted from lethal accumulation of stress alarmones (p)ppGpp, perturbations in carbon and energy metabolism, thiol-based antioxidant system depletion, and disrupted lipidic membrane repair. These findings illuminate the intricate metabolic signaling networks driving polymyxin tolerance in A. baumannii. By untangling pathogen-directed stress tolerance mechanisms, we deepen our understanding and identify potential therapeutic targets. Our discoveries offer new avenues to combat polymyxin resistance, paving the way for more effective treatments against superbugs. Through continued exploration, we can harness this knowledge to develop innovative strategies and overcome the challenges posed by polymyxin tolerance.

microbiology↗

bioRxiv2024

Transcriptomic interplay between Acinetobacter baumannii, human macrophage and polymyxin

Optimization of antibiotic therapy has been hindered by our dearth of understanding on the mechanism of the host-pathogen-drug interactions. Here, we employed dual RNA-sequencing to examine transcriptomic perturbations in response to polymyxin B in a co-culture infection model of Acinetobacter baumannii and human macrophages. Our findings revealed that polymyxin B treatment induced significant transcriptomic response in macrophage-interacting A. baumannii, exacerbating bacterial oxidative stress, disrupting metal homeostasis, affecting osmoadaptation, triggering stringent stress response, and influencing pathogenic factors. Moreover, infected macrophages adapt heme catabolism, coagulation cascade, and hypoxia-inducible signaling to confront bacterial invasion. Disrupting rcnB, ompW, and traR/dksA genes in A. baumannii impairs metal homeostasis, osmotic stress defense and stringent responses, thereby enhancing antibacterial killing by polymyxin. These findings shed light on the global stress adaptations at the network level during host-pathogen-drug interactions, revealing promising therapeutic targets for further investigation. IMPORTANCEIn the context of the development of bacterial resistance during the course of antibiotic therapy, the role of macrophages in shaping bacterial response to antibiotic killing remains enigmatic. Herein we employed dual RNA-sequencing and an in vitro tripartite model to delve into the unexplored transcriptional networks of the Acinetobacter baumannii-macrophage-polymyxin axis. Our findings uncovered the potential synergy between macrophages and polymyxin B which appear to act in co-operation to disrupt multiple stress tolerance mechanisms in A. baumannii. Notably, we discovered the critical roles of bacterial nickel/cobalt homeostasis (rcnB family), osmotic stress defense (ompW family), and stringent response regulator (traR/dksA C4-type zinc finger) in tolerating the last-line antibiotic polymyxin B. Our findings may lead to potential targets for the development of novel therapeutics against the problematic pathogen A. baumannii.

microbiology↗

bioRxiv2022

Diversified repertoire of phage defenses in Klebsiella pneumoniae: Bi-directional steering effects impacting antibiotic susceptibility

Bacteriophage (phage) therapy is rising as a promising anti-infective option to combat antimicrobial resistance; however, its clinical utilization is severely hindered by the potential emergence of phage resistance. Fortunately, certain phage resistance mechanisms can restore bacterial antibiotic susceptibility, making the combination of phages with antibiotics a potential strategic approach. Here, we demonstrated that phage resistance can also lead to increased antibiotic resistance and provided mechanistic insights into bacterial phage defense mechanisms. We discovered a repertoire of phage resistance mechanisms in Klebsiella pneumoniae, including the disruption of phage binding site (fhuA::Tn and tonB::Tn), extension of phage latent period (mnmE::Tn and rpoN::Tn) and increased mutation frequency (mutS::Tn and mutL::Tn). Different from the prevailing view that phage resistance re-sensitizes antibiotic-resistant bacteria, we revealed a bidirectional steering effect on the bacterial antibiotic susceptibility. Specifically, it was uncovered that, while rpoN::Tn became more susceptible to colistin, mutS::Tn and mutL::Tn caused increased resistance to rifampicin and colistin. Our findings highlight the diversified strategies utilized by K. pneumoniae to overcome phage infection and the parallel effect on the antibiotic susceptibility. Mechanism-guided phage steering represents a rational strategy that should be incorporated into phage therapy to better inform clinical decisions.

microbiology↗

bioRxiv2018

Phylogeny and distinct properties of major intrinsic proteins in the genomes of six Phytophthora species suggest their novel functions in Phytophthora

ABSTRACTMajor intrinsic proteins (MIPs), commonly known as aquaporins, facilitate the membrane diffusion of water and some other non- polar solutes. MIPs might be involved in host-pathogen interactions. Herein, we identified 17, 24, 27, 19, 19, and 22 full-length MIPs, respectively, in the genomes of six Phytophthora species, P. infestans, P. parasitica, P. sojae, P. ramorum, P. capsici, and P. cinnamomi. These Phytophthora species are devastating plant pathogens and members of oomycetes, a distinct lineage of fungus-like eukaryotic microbes. Phylogenetic analysis showed that the Phytophthora MIPs (PMIPs) formed a completely distinct clade from their counterparts in other taxa and were clustered into nine subgroups. Sequence and structural properties indicated that the primary selectivity-related constrictions, including aromatic arginine (ar/R) selectivity filter and Froger’s positions in PMIPs were distinct from those in other taxa. The substitutions in the conserved Asn-Pro-Ala motifs in loops B and E of many PMIPs were also divergent from those in plants. We further deciphered group-specific consensus sequences/motifs in different loops and transmembrane helices of PMIPs, which were distinct from those in plants, animals, and microbes. The data collectively supported the notion that PMIPs might have novel functions.Competing Interest StatementThe authors have declared no competing interest.View Full Text

bioinformatics↗