Biology subjects

Mahmud, Z. H.

Publications and source records attributed to Mahmud, Z. H..

3 recordsLinked to original sources

bioRxiv2025

Dirt floors and domestic animals are associated with soilborne exposure to antimicrobial resistant E. coli in rural Bangladeshi households

Soil can harbor enteropathogens and antimicrobial-resistant organisms in settings with domestic animals. We enrolled 49 households with young children (28 soil floors, 21 concrete floors) in Bangladesh and recorded animal ownership/management. Staff swabbed the floor of childrens sleeping area with a sterile sponge and collected floor dust and a child hand rinse. We used IDEXX QuantiTray/2000 with and without cefotaxime supplementation to enumerate cefotaxime-resistant and generic E. coli. There was 8.0 g/m2 of dust on soil floors vs. 0.2 g/m2 on concrete floors (p-value=0.005). We detected E. coli on 100% of soil vs. 86% of concrete floors and cefotaxime-resistant E. coli on 89% of soil vs. 43% of concrete floors (p-values<0.05). Cefotaxime-resistant E. coli prevalence on floors was 36% in compounds without animals, 79% in compounds with animals and 100% if animals stayed indoors overnight or the floor had animal feces; associations were strongest for chickens. In multivariable models, generic and cefotaxime-resistant E. coli counts were 1.5-2 log higher on soil vs. concrete floors, and counts on floors and child hands were 0.17-0.24 log higher for every 10 additional chickens owned (p-values<0.05). Efforts to mitigate infections and antimicrobial resistance in low-income countries should test flooring improvements and hygienic animal management. SynopsisIn rural Bangladeshi households, generic and cefotaxime-resistant E. coli were more common on soil floors than concrete floors and among households with higher cohabitation intensity with domestic animals, especially chickens.

microbiology↗

bioRxiv2024

Pathogens and Antimicrobial Resistance Genes in Household Environments: A Study of Soil Floors and Cow Dung in Rural Bangladesh

In low- and middle-income countries, living in homes with soil floors and animal cohabitation may expose children to fecal organisms, increasing risk of enteric and antimicrobial-resistant infections. Our objective was to understand whether cow cohabitation in homes with soil floors in rural Bangladesh contributed to the presence and diversity of potential pathogens and antimicrobial resistance genes (ARGs) in the home. In 10 randomly selected households in rural Sirajganj District, we sampled floor soil and cow dung, which is commonly used as sealant in soil floors. We extracted DNA and performed shotgun metagenomic sequencing to explore potential pathogens and ARGs in each sample type. We detected 6 potential pathogens in soil only, 49 pathogens in cow dung only, and 167 pathogens in both soil and cow dung. Pathogen species with relative abundances >5% in both soil floors and cow dung from the same households included E. coli (N=8 households), Salmonella enterica (N=6), Klebsiella pneumoniae (N=2), and Pseudomonas aeruginosa (N=1). Cow dung exhibited modestly higher pathogen genus richness compared to soil floors (Wilcoxon signed-rank test p=0.002). Using Bray-Curtis dissimilarity, pathogen species community composition differed between floors and cow dung (PERMANOVA p<0.001). All soil floors and cow dung samples contained ARGs against antibiotic classes including sulfonamides, rifamycin, aminoglycosides, lincosamides, and tetracycline. Paired floor and cow dung samples shared ARGs against rifamycin. Our findings support the development of interventions to reduce soil and animal feces exposure in rural, low-income settings. ImportanceIn low-income countries, inadequate housing materials and animal cohabitation can lead to fecal contamination of rural homes. Contaminated soil floors are difficult to clean and may harbor organisms causing illness and antibiotic resistance, especially in young children, who frequently ingest soil. We sequenced soil floor and cow dung samples from households in Sirajganj district, Bangladesh and identified pathogens and antibiotic resistance genes. We detected 167 pathogens in both soil and cow dung; pathogens present in both sample types at the highest relative abundances were E. coli, Salmonella enterica, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Antibiotic resistance genes were found in all samples. In cow dung, the most common genes conferred resistance to the antibiotics lincosamide, rifamycin, cephamycin, and tetracycline. In soil floors, the most common genes conferred resistance to rifamycin, sulfonamides, and aminoglycosides. Household soil and cow dung may be important reservoirs of pathogens and antimicrobial resistance in low-income countries.

microbiology↗

bioRxiv2018

Novel cholera toxin variant and ToxT regulon in environmental Vibrio mimicus strains: potential resources for the evolution of Vibrio cholerae hybrid strains

Atypical El Tor strains of Vibrio cholerae O1 harboring variant ctxB genes of cholera toxin (CT) are gradually becoming a major cause of recent cholera epidemics. Vibrio mimicus occasionally contains virulence factors associated with cholera, e.g., CT, encoded by ctxAB on CTX[FE] genome; and TCP, the CTX[FE]-specific receptor. This study carried out extensive molecular characterization of CTX[FE] and ToxT regulon in ctx+ve strains of V. mimicus isolated from the Bengal coast. Southern hybridization, PCR, and DNA sequencing of virulence related-genes revealed the presence of an El Tor type CTX prophage (CTXET) carrying a novel ctxAB, tandem copies of environmental type pre-CTX prophage (pre-CTXEnv), and RS1 elements, which were organized in an array of RS1-CTXET-RS1-pre-CTXEnv-pre-CTXEnv. Additionally, a novel variant of tcpA and toxT respectively, showing clonal lineage to a phylogenetic clade of V. cholerae non-O1/O139, was identified. The V. mimicus strains lacked the RTX and TLC elements, and Vibrio seventh pandemic islands of the El Tor strains, but contained five heptamer (TTTTGAT) repeats in ctxAB promoter region like some classical strains of V. cholerae O1. PFGE analysis showed all the ctx+ve V. mimicus strains were clonally related. However, their in vitro CT production and in vivo toxigenecity were variable, which could be explained by differential transcription of virulence genes along with ToxR regulon. Taken together, our findings strongly suggest that environmental V. mimicus strains act as potential reservoir of atypical virulence factors, including variant CT and ToxT regulon, and may contribute to the evolution of V. cholerae hybrid strains.\n\nIMPORTANCENatural diversification of CTX[FE] and ctxAB genes certainly influences disease severity and shifting patterns in major etiological agents of cholera, e.g., the overwhelming emergence of hybrid El Tor variants, replacing the prototype El Tor strains of V. cholerae. This study showing the occurrence of CTXET comprising a novel variant of ctxAB in V. mimicus points out a previously unnoticed evolutionary event, independent to that of the El Tor strains of V. cholerae. Identification and cluster analysis of the newly-discovered alleles of tcpA and toxT indicates their horizontal transfer from an uncommon clone of V. cholerae. The genomic content of ToxT regulon, and tandemly arranged multiple pre-CTX[FE]Env and a CTX[FE]ET in V. mimicus probably act as salient raw materials inducing natural recombination among the hallmark virulence genes of hybrid V. cholerae strains. This study will facilitate deeper understanding of the evolution of new variant CT and ToxT regulon, influencing cholera epidemiology.

microbiology↗