A dip slide (or dipslide) is a test for the presence of

microorganism A microorganism, or microbe, is an organism of microscopic scale, microscopic size, which may exist in its unicellular organism, single-celled form or as a Colony (biology)#Microbial colonies, colony of cells. The possible existence of unseen ...

s in

liquid Liquid is a state of matter with a definite volume but no fixed shape. Liquids adapt to the shape of their container and are nearly incompressible, maintaining their volume even under pressure. The density of a liquid is usually close to th ...

s. The use of dip slides is the method most frequently used to measure and observe microbial activity in liquid-based systems. It is often used in testing cooling systems. Dip slides are often used to determine the presence of slime forming bacteria in cooling & industrial water systems. The

Health and Safety Executive The Health and Safety Executive (HSE) is a British public body responsible for the encouragement, regulation and enforcement of workplace health, safety and welfare. It has additionally adopted a research role into occupational risks in Great B ...

's (HSE) recommends the use of dipslides to monitor the general activity of aerobic bacteria. The dip slide test consists of a sterile

culture medium A growth medium or culture medium is a solid, liquid, or semi-solid designed to support the growth of a population of microorganisms or cells via the process of cell proliferation or small plants like the moss '' Physcomitrella patens''. Diffe ...

on a plastic carrier that is dipped into the liquid to be sampled. The culture is then incubated, allowing for microbial growth. Most Dip slides consist of 1 - 2 agars attached to a flexible plastic paddle, this allows full contact of the agar onto the desired area for testing. Most Dipslides come in a circular clear shatterproof tube that can be inserted into a dip-slide incubator.

Method

Most Dip slides are incubated at 30 °C for 48 hours after being dipped into the sample to ensure that the results are accurate. Some dipslides require different temperatures and incubation times depending on the type of agar used, and which organism is being tested for. After being dipped into the sample the dip slide is returned and secured in its original container for the incubation process. Multiple tests at varying periods are recommended to increase accuracy. It is important that

biocides A biocide is defined in the European legislation as a chemical substance or microorganism intended to destroy, deter, render harmless, or exert a controlling effect on any harmful organism. The US United States Environmental Protection Agency, En ...

are not applied to the water prior to testing as this would significantly alter the results. The

clarity Clarity may refer to: Music Albums * ''Clarity'' (Jimmy Eat World album) or the title song, 1999 * ''Clarity'' (Sifow album) or the title song, 2006 * ''Clarity'' (Zedd album) or the title song (see below), 2012 * ''Clarity'' (mixtape), by K ...

of the sample is not necessarily reflective of the presence of

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

as seemingly clear water may still have bacteria present. For some water systems a weekly dip slide test is recommended. For multiple tests the

incubation period Incubation period (also known as the latent period or latency period) is the time elapsed between exposure to a pathogenic organism, a chemical, or ionizing radiation, radiation, and when symptoms and signs are first apparent. In a typical infect ...

and

temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

should be the same each time a new sample is assessed. Bacteria present in the sample liquid will grow and form colonies. A bacterial reference chart is used to determine the number of bacteria in the sample. Appropriate treatment is applied to the water source once abnormal levels of bacterial activity are noticed. Once water treatment is effective the bacterial count produced by the dip slide test should be low, approximately <10⁴. Dip slides are normally used when microbiological activity is relatively high (1,000 - 100,000 CFU per milliliter of water). The dip slide results should be used only as a guide as the accuracy of the dip slide is limited as a result of the small sample size that is analyzed and the method used to obtain results. Nevertheless, dip slides may be very useful as they are very convenient, simple to use and cost effective.

References

{{Clinical microbiology techniques Bacteriology Microbiology equipment