| || |
(A) What is BACTO- H2S Kit?
LTEK'S BACTO-H2S is ready to use simple device based on waterborne hydrogen sulphide indicator bacteria for carrying out bacteriological examination of drinking water for presence of faecal coliform. It is an improved version of present H2S Strip Test Kit and is more sensitive and more acceptable.
(B) How BACTO- H2S differs from original H2S Strip Test?
|1)In BACTO- H2S water sample to be taken is 100 ml instead of 20 ml as proposed in original test. This is more logical and justified on the theory that no coliform bacterial should be present in 100 ml drinking water sample. This also increases the magnitude of detection of harmful bacteria. |
2) L-cystine is added to original medium in order to increase the sensitivity of the test.
3) Instead of absorbing the media on a strip of paper, it is filled in nitrogen atmosphere into a hand breakable glass ampoule of highest quality, sealed and sterilized. This assures the integrity and sterility of medium and also helps to increase the shelf life. The new type of glass ampoule can be easily broken by hand.
4) Appropriate additional quantity of media is added in proportion to 100 ml water sample.
Bottle is made up of a special grade of compounded polymer, compatible with the components of medium, transparent and does not leach any harmful additive in water sample to affect the test result.
6) All the articles of BACTO-H2S kit are sterilized by latest process of sterilization well accepted for biological products in pharmaceutical industry. The sterilization process does not affect bottle or deposit or leave any harmful residue in bottle to affect the test.
7) Raw materials used in preparation of medium are of highest purity.
(C) How to use BACTO-H2S ?
| ||Ready to use, presterilized BACTO-H2S kit contains BACTO-H2S bottle, cap, and pre-measured media filled into ampoule. Water sample is poured into the bottle. Media from ampoule is added to sample water, mixed. Bottle is kept at a room temperature (about 30-37 degree C) and observed for 24 hours. |
Directions For Use With Schematic Diagrams
It is expected from user to carry out the test in sanitary conditions. Washing of hands with soap and water, avoidance of contamination in handling of bottle and cap during performing the test and filling of bottle with water sample are some of the matter of concern. This is a must to maintain the "sterile and aseptic" conditions required for the test. Failure to meet these may result in false positive result.
|(D) Interpretation of Results : |
| ||Water Positive result is indicated when the water sample turns
black. From the sample source is contaminated with harmful bacteria and is not safe for drinking. If water sample does not turn black water from the source is free from harmful bacteria and safe for drinking. 24
to 48 hours of incubation at room temperature is an ideal period for observation. There is a relationship between the degree of contamination and time required for change in colour. If there is high degree of contamination water sample will turn black within 12 to 16 hours with the present kit. If contamination is very low it may take 24-48
hours. Similarly room temperature also affects the time required to turn water sample black. Temperature range of 30 degree C to 37 degree C is most favorable for the test. At extreme low temperature i.e. less than 30 degree C, it takes long period for change of colour. During winter in northern states this situation is most likely to occur. In this case it is advisable that BACTO-H2S bottle with sample should be kept in an incubator or a warm place having the necessary temperature. In a UNICEF sponsored study for assessment of kits 120 hours of incubation period at 30 to 35 ° C is advocated to establish the total absence of faecal coliform. Such a long period of observation for "YES-NO" type of kit is not desirable for various reasons. Some times false positive results may be observed with prolonged period of Incubation. After all it is an "indicative" test and not the replacement of conventionally used laboratory methods. "Quick and Reliable" approach should not be sacrificed for a kit to be used predominantly in rural area. || |
|(E) Course of Action: |
| ||Samples from water source showing positive results should be sent to Public Health Laboratory for confirmation and water from these sources should be chlorinated with bleaching powder or boiled prior to use it for drinking. || |
(F) Shelf Life:
| ||If kept in a cool dry place one should expect the long shelf life of the medium. We propose one year from date of manufacture. || |