Laboratories often require specific care for samples for microbiological testing. Temperature and time are important factors and are very integral to the whole process. A little slip in the procedures may contaminate the samples and significantly affect the results. 

This is a huge concern because an otherwise positive test may turn out negative, or vice versa. One certainly doesn’t want to be treated with something he or she doesn’t have, but it could be also worse — an infected person may not be given proper and immediate medical attention because of an erroneous laboratory test.  

Therefore, handling of the samples should be given utmost attention and detail. Some tests may require preserving samples in a cold bath or with ice, while some are preferred to be stored at room temperature. Time is also crucial in the process because it also determines the extent of the growth and development of bacteria.

In the case of Legionella, AquaCert has always advocated a 48-hour window for testing as well as the accuracy of water quality testing kits. So long as samples shipped by couriers reach their laboratory within that time frame, the Legionella bacteria will have neither increased nor decreased significantly. Although that guideline was mostly based on experience and investigation, AquaCert now has proof that their method is indeed correct.

Research done by the Special Pathogens Laboratory, an internationally recognised expert in Legionella, confirms the effect of holding time on samples. The study, which included harvesting of Legionella testing samples from 12 different sinks from a hospital administrative and outpatient building, found out that no significant increase or decrease in Legionella viability was observed within 48 hours of collection. The process was done twice a week for almost seven weeks, involving a total of 155 samples.

Three sample bottles were collected from the sites – one was tested immediately, and the other two after 24 and 48 hours. The research showed that “Legionella concentrations were stable during the typical time needed to transport a water sample for culture.” The paper was presented at the Association for Professionals in Infection Control and Epidemiology.

 In part, this new finding led to a realization of the lack of guidelines and has influenced a call for standardized measures in dealing with Legionella. With over three decades since it first gained attention, Legionnaire’s disease has still lingered and remains common throughout the world. According to ASHRAE, a global society advancing human well-being through sustainable technology, recent cases include outbreaks in Australia, Canada and the United States. The standard aims to help identify risk factors for growth and exposure to Legionella.

+Duncan Hollis