Comparative study of suspected biofilm characteristics of Escherichia coli isolated from in tubewell and tap water

Abstract

Access to clean water remains a critical public health challenge, particularly due to microbial contamination. This study analyzed 400 water samples, equally divided between tubewell and tap water systems from 50 urban and rural locations, to assess E. coli contamination, water quality, and biofilm formation. A total of 400 samples were analyzed, out of which 115 samples tested positive for E. coli (28.75%). Contamination was significantly higher in tap water (46.5%) than in tubewell water (11.0%), with 93 tap water samples and 22 tubewell water samples testing positive. Among tap water samples, 30% were safe for drinking, 50% were safe for household use but not for drinking, and 20% tap water samples were unsafe for any use, based on fecal coliform count whereas tubewell water showed 40% were safe for drinking, 50 % were safe for household use but not for drinking and 20% tubewell water samples were unsafe for any use. The study assessed the antibiotic resistance patterns of Escherichia coli isolates from tap and tubewell water sources. The findings revealed a high prevalence of multidrug resistance (MDR), with the majority of isolates showing resistance to critical antibiotics. Meropenem (90.43%) and Piperacillin-Tazobactam (92.04%) exhibited the highest resistance, indicating potential carbapenemase-producing strains. Fluoroquinolone resistance was also significant, with Levofloxacin (80.73%) and Norfloxacin (70.75%) showing high resistance rates. Additionally, Cefepime (88.7%) and Ceftriaxone (70.37%) demonstrated strong resistance, raising concerns about the effectiveness of beta-lactam antibiotics. Sulfamethoxazole-Trimethoprim resistance reached 92.42%, while Azithromycin exhibited the lowest resistance (53.76%). The high resistance rates highlight urgent concerns regarding antimicrobial resistance (AMR) in waterborne E. coli isolates, emphasizing the need for enhanced water treatment, stricter antibiotic stewardship, and continuous surveillance to prevent the spread of resistant strains. This study evaluated biofilm formation in Escherichia coli isolates from tap and tubewell water samples using optical density (OD) measurements at 570 nm. The results revealed strong biofilm formation in 22.5% of samples, moderate biofilm formation in 70%, and weak biofilm formation in 7.5%, indicating a high prevalence of bacterial persistence. Tap water samples exhibited higher biofilm OD values (mean: 1.18 ± 0.45) compared to tubewell water (mean: 1.02 ± 0.35), suggesting that municipal water pipelines provide a more conducive environment for biofilm development. Locations such as Shariatpur, Rupganj, Comilla, and Joydevpur had the highest biofilm OD values, raising concerns about long-term microbial contamination and potential pathogen retention in drinking water systems. These findings emphasize the need for regular biofilm monitoring, improved water infrastructure, and enhanced disinfection strategies to mitigate health risks associated with biofilm-associated pathogens. The molecular analysis for the blaTEM gene, a marker associated with beta-lactam resistance, revealed no detectable bands in any of the isolates. This absence suggests that blaTEM is not contributing to the observed resistance patterns in this study population. To evaluate this finding statistically, the antibiotic susceptibility test (AST) results for beta-lactam antibiotics commonly associated with blaTEM—including ampicillin, amoxicillin, ceftriaxone, cefepime, cefixime, and ceftazidime—were analyzed. The analysis of Escherichia coli isolation and detection of the fliCH7 gene across 50 locations provides valuable insights into the prevalence and pathogenic potential of E. coli in water sources. Among 115 positive samples, molecular screening identified 18 samples as positive for the pathogenic fliCH7 gene, which is a key virulence determinant associated with pathogenic E. coli strains. Statistically, this accounts for 15.65% of the E. coli-positive samples and 4.5% of the total water samples screened. The locations with fliCH7-positive samples demonstrated a diverse geographical distribution.