|Year : 2020 | Volume
| Issue : 1 | Page : 2-5
Comparative analysis of a rapid detection method and conventional method to ensure microbial quality of drinking water
B Isabella Princess
Department of Microbiology, Apollo Speciality Hospitals, Chennai, Tamil Nadu, India
|Date of Submission||30-Nov-2019|
|Date of Acceptance||30-Dec-2019|
|Date of Web Publication||17-Mar-2020|
B Isabella Princess
Junior Consultant, Department of Microbiology, Apollo Speciality Hospitals, Vanagaram, Chennai, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Objective: Drinking water analysis is an important quality monitor and forms an integral part of the infection control policy of every hospital. On an average daily basis, 1750 liters of drinking water are used by patients and hospital staff. Presence of contaminating microorganisms in drinking water should therefore be identified at the earliest and necessary action be taken in order to prevent outbreaks through contaminated water. This study was conducted to compare two methods for drinking water analysis and document benefits of the new method. Methods: This cross sectional study was conducted over a period of two years at a tertiary care hospital in Chennai. A newer rapid method of drinking water analysis was evaluated for two years from July 2017 to June 2019. Parallel testing with conventional multiple tube method was performed. All samples collected from various sources during the study period were subjected to parallel testing by multiple tube method (conventional method for most probable number) and presence absence method (new method). Results: The new commercial kit for drinking water analysis comprehensively detects all water borne bacterial pathogens associated with gastroenteritis within 18 hours. The major advantage is marked reduction in turnaround time by 54 hours. False positive/false negative results were not encountered compared to the standard conventional method. Conclusion: Safer, healthier and high quality of water is ensured for use at an earlier and cost effective as well as environment friendly system. There was marked reduction in turnaround time, cost of testing, manpower usage, reagent wastage, waste generation using the kit based presence absence method. The new commercial kit can effectively replace the conventional method as an effective screening tool for drinking water analysis.
Keywords: Drinking water analysis, drinking water, most probable number, potable water, presence-absence method
|How to cite this article:|
Princess B I. Comparative analysis of a rapid detection method and conventional method to ensure microbial quality of drinking water. Apollo Med 2020;17:2-5
|How to cite this URL:|
Princess B I. Comparative analysis of a rapid detection method and conventional method to ensure microbial quality of drinking water. Apollo Med [serial online] 2020 [cited 2020 Mar 31];17:2-5. Available from: http://www.apollomedicine.org/text.asp?2020/17/1/2/280918
| Introduction|| |
Potable water should be of Class I quality, i.e., ultrapure with no contaminating bacteria present during use. In our health-care facility, on an average daily basis, 1750 L of drinking water (25 L × 70 cans) are used by patients and hospital staff. Apart from canned water, bottled drinking water is also available for the patient as well as common use. The presence of contamination in drinking water should, therefore, be identified at the earliest, and necessary action is taken to prevent outbreaks through contaminated water.
Water analysis for ensuring the microbial quality of drinking water is performed on a quarterly basis as per standard national guidelines. The red alert organisms in drinking water are coliform Gram-negative organisms belonging to Enterobacteriaceae family and fecal streptococci (Enterococci). These organisms signify poor water quality and propagation of these microbes to the patient environment might have deleterious effects.
The conventional method of performing water analysis is still being followed in almost all health-care facilities. The final identification of pathogens by this method requires 72 h. Within 72 h, there is a high risk of spread of infection through the water to patients. This method is more labor-intensive, requires special media preparation, equipment, and glassware usage is high with, of course, increased turnaround time.
All these factors paved the way to identify an alternative method whose advantages outweigh the conventional method.
The aim of the study was to compare two methods of drinking water analysis and document the benefits of the new method.
| Methodology|| |
This cross-sectional study was conducted at our tertiary care center from July 2017 to June 2019. Drinking water samples were first processed with multiple-tube method. During the study period, a new commercial kit was also tested. This media employs the presence-absence method to rapidly detect microbial contamination in drinking water using preformed substrates in a single bottle. Quality control was performed to test this new media, namely, HiH2S test bud. All possible microorganisms known to contaminate drinking water were included in the quality control of the new kit such as Escherichia More Details coli, Klebsiella pneumoniae, Salmonella More Details species, and Pseudomonas aeruginosa. Satisfactory observations, as described in the kit were seen within 18 h of incubation. The identification of the organism was easy and reliable when counterchecked. Parallel testing was done along with the conventional multiple-tube method with all possible organisms, and the correlation was appropriate [Figure 1]. No discrepancy was noted between the two methods. After standardization of the new media for water analysis using internal quality control and parallel testing, water analysis was being performed using the new method successfully [Figure 2].
|Figure 1: The procedure of conventional multiple-tube method (most probable number)|
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Conventional multiple-tube method (Most Probable Number) was performed by adding potable water in the following order: 50 ml water in 50 ml double strength broth, five 10 ml samples in 10 ml double strength media, and five 1 ml samples in 5 ml single strength broth. The count was determined as the most probable number using Mc Crady's chart. The presence-absence method was performed by adding 100 ml of potable water into the commercial HiH2S test bud bottle. The results were interpreted as per the manufacturer's instructions and documented.
| Results|| |
The conventional method for bacteriological analysis of drinking water relies on color change and gas production [Figure 1]. The new method employed to test drinking water quality employs detection based on color change, indole production, and H2S production [Figure 3]. It is easy to perform, cost-effective, turnaround time is decreased, special media is not necessary, additional equipment, and glassware can be eliminated and overall waste generated is less.
|Figure 3: Color change, H2S production, and indole production seen in HiH2S test bud|
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The commercially available kit for drinking water analysis comprehensively detects all waterborne bacterial pathogens associated with gastroenteritis within 18 h. The major advantage is marked reduction in turnaround time by 54 h. In our study, false-positive/false-negative results were not encountered when compared to the standard conventional method.
Advantages after implementation of the new method are as follows:
- There is a significant reduction in turnaround time by 54 h
- Reports of water analysis are available within 18 h using the new method, whereas the old method took 72 h
- We were able to achieve better infection control by ensuring the quality of drinking water within 18 h (54 h earlier than the old method)
- Early turnaround time helps to detect organisms in case of water contamination. Patient safety is ensured
- Contaminated water is immediately removed from the hospital environment
- There is the elimination of the tedious procedure which was previously followed leading to better utilization of technician's time
- Special media (MacConkey broth) preparation is not required
- Solid media subculture and biochemical identification steps have been eliminated
- Reagent and glassware washing have been eliminated.
Cost incurred for procuring the new media was lesser than the total cost used in the older method.
| Discussion|| |
Since there are many advantages and benefits for patients and laboratory personnel performing the test and marked reduction in turnaround time and sample processing time, we continue to use the new method for the analysis of drinking water [Table 1]. The conventional method mandatorily requires subculture and biochemical identification of the organism from the primary broth. This makes the process of multiple-tube method tedious and results in a longer turnaround time. Whereas, the new method allows direct detection of microorganisms from the primary broth, thereby making the process simple. Identification is done based on color change, indole production, and H2S production detected within 18–24 h of incubation. Based on these properties, specific organisms suggestive of water contamination are identified. In the new method, color change to yellow denotes the presence of coliform bacteria, H2S producers are detected as black color deposits, indole production of E. coli is detected by adding indole, and appearance of the pink ring above the media.
The importance of drinking water analysis is evident from recommendations in various national and international as well as infection control guidelines. The choice of testing method should be based on the type of water source, feasibility, and cost of testing and population served. There are no specific recommendations for testing packaged and canned drinking water. Previous studies on the microbiological quality of packaged drinking water have employed multiple-tube method, total viable count, membrane filtration method, and presence-absence method for enzyme detection., The most commonly used method in developing nations is the multiple-tube method for estimating the most probable number. This method may be ideal for testing water from common sources such as wells, ponds, and lakes. In our setting, drinking water is of ultrapure quality since the source is mineral water. The normal amount of contamination is very negligible, thereby warranting a more sensitive method in such scenarios. This makes us reemphasize the usefulness of the presence-absence method in similar settings where packaged mineral water is used for drinking purposes.
| Conclusion|| |
Safer, healthier, and high quality of water is ensured for use at an earlier and cost-effective as well as environment-friendly system. There was a marked reduction in turnaround time, cost of testing, workforce usage, reagent wastage, and waste generation using the kit based presence-absence method. The new commercial kit can effectively replace the conventional method as an effective screening tool for drinking water analysis. It can be easily used in laboratories in rural areas that do not have facilities for media preparation. Another major advantage is the ease in the interpretation of results.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]