Related Experiment Video
Updated: Jun 25, 2026
Isolation and Identification of Waterborne Antibiotic-Resistant Bacteria and Molecular Characterization of their Antibiotic Resistance Genes
Published on: March 3, 2023
Isolation and characterization of biocides resistant bacteria from dental unit water line biofilms
Iram Liaqat1, Anjum Nasim Sabri
1Department of Microbiology and Molecular Genetics, University of the Punjab, Quaid-e-Azam Campus Lahore, Pakistan. iramliaq@hotmail.com
Abstract:
Six biocides resistant isolates were isolated from dental unit water lines (DUWL) in Pakistan. All isolates could tolerate 150 microg ml(-1 )of biocides (5.25% sodium hypocholrite, 35% H2O2, 4% tween 20, 1% povidine iodine, 0.2% chlorohexidine gluconate, 1% ethylene di-amino tetra acetic acid and 1% phenol) on l-agar and 100 microg ml(-1 )in l-broth. The growth rate of all isolates was determined by generating growth curves at 37 degrees C for 48 h. The isolates were found to differ in growth rates with lag phase varying from (4-6 h) in biocides supplemented media compared to 2-4 h in biocides free medium. They have wide temperatures (24-42 degrees C) and pH (5-9) ranges. Traditional ways of identification of bacteria by phenotypic characteristics were accomplished by phenotypic and biochemical characterization. Heavy metals and antimicrobial susceptibility tests indicated that all isolates examined were resistant to trimethoprim, chloramphenicol while sensitive to HgCl2 and Pb (NO3)2. Almost all isolates were opportunistic pathogens. The 16S rRNA-encoding genes from these six isolates were sequenced to confirm the identity of these isolates. 5 different genera (Bacillus, Achromobacter, Pseudomonas and Klebsiella) of bacteria were identified by 16S rDNA genes amplified from genomic DNA of biocides resistant DUWL biofilm isolates. Analysis of 16S rDNA genes revealed a much more clear identification of microorganisms than culture methods. However, different species of the same genera can have the same 16S rRNA gene sequence but are different due to phenotypic differences or different clinical manifestations.
Insights
Six biocides-resistant bacterial isolates from dental unit water lines (DUWL) in Pakistan exhibit tolerance to various disinfectants. Molecular identification revealed five genera, highlighting the need for advanced identification methods in clinical settings.
Area of Science:
- Microbiology
- Environmental Health
- Dental Public Health
Background:
- Dental unit water lines (DUWL) can harbor microbial biofilms resistant to biocides.
- Understanding the characteristics of these resistant bacteria is crucial for infection control in dental settings.
Purpose of the Study:
- To isolate and identify biocide-resistant bacteria from DUWL in Pakistan.
- To characterize their growth, tolerance, and susceptibility profiles.
- To confirm identification using molecular methods (16S rRNA gene sequencing).
Main Methods:
- Isolation of bacteria from DUWL biofilms.
- Determination of biocide tolerance, growth curves, temperature, and pH ranges.
- Phenotypic, biochemical, antimicrobial susceptibility, and heavy metal testing.
- 16S rRNA gene sequencing for precise identification.
Main Results:
- Six isolates demonstrated resistance to multiple biocides commonly used in dental settings.
- Isolates exhibited altered growth rates and wide ranges of temperature and pH tolerance.
- Resistance to trimethoprim and chloramphenicol, sensitivity to mercury and lead.
- Molecular identification confirmed five genera: Bacillus, Achromobacter, Pseudomonas, and Klebsiella.
Conclusions:
- Biocide-resistant bacteria, including opportunistic pathogens, are prevalent in Pakistani DUWL.
- 16S rRNA gene sequencing provides more accurate identification than traditional methods.
- Findings underscore the importance of effective disinfection protocols and advanced diagnostics in dental environments.
