Rapid detection of Legionella spp in water samples by ScanVIT method: comparison of acid vs heat treatment

BACKGROUND

A rapid detection of Legionella bacteria in water samples is crucial to minimize the risk of acquiring infections, especially in health care facilities. Different detection methods and different decontamination procedures have been reported to affect the recovery of Legionella spp. Our goal was to test the recovery of Legionella pneumophila and Legionella non-pneumophila species using a kit based on non-specific and species-specific probes to treat water samples after two different decontamination procedures.

METHODS

The study was conducted with samples collected in the teaching hospital "Le Scotte" of Siena (Italy). Waters samples were analyzed by: i) ScanVIT method after treatment with acids; ii) ScanVIT method after heating; and iii) cultural standard method after heating. The results of the decontamination procedures and the detection methods were evaluated by comparing the number of Legionella-positive and -negative samples, and the recovery rates (CFU l-1) obtained by ScanVIT and the standard method.

RESULTS

We find that ScanVIT method is highly sensitive with both decontamination treatments, yielding a higher recovery of L. pneumophila compared to the standard method. Conversely, ScanVIT associated with the acid-treatment yielded the highest recovery of L. non-pneumophila.

CONCLUSIONS

The acid-treatment combined to the ScanVIT method increases the recovery of L. non-pneumophila in water samples compared to both ScanVIT associated with heat-treatment and standard culture method. Thus, this method may represent the best choice to detect L. non-pneumophila in water samples and reduce the risk of infection due to underestimation of Legionella loads.

Could chips and nuts be vector of food-borne outbreaks during happy hour?

Background

A Greater tendency to eat meals outside the home has led to an increase in the attendance of restaurants, cafes, and fast food. That is one of the reasons why the global interest in handling food has risen over the years. The aim of this study is to understand the level of microbial contamination in the food that is served along happy hour in cafe.

Methods

This cross sectional pilot study was performed from April to May 2018 in the city of Siena, central Italy (<60000 citizens). Ten cafes were randomly selected. Samples of peanuts and potatoes were obtained in three different moments, at the beginning (T0), in the middle (T1), at the end (T2) of happy hours events. Collection of the samples was obtained using sterile kit and laboratory analysis was conducted in the University lab. The samples were located on selective medium and the growth of microbial pathogens were checked at 24 and 48 hours. The tested microorganisms were Enterococci, Staphylococci, Coliforms bacteria, Molds, and Yeasts. The statistical analyses were conducted using the Wilcoxon test using Stata 12.

Results

A significant Yeasts contamination appeared only on chips at T0, while within T0 and T1 we found a significant increase of Enterococci, Staphylococci, and Yeasts (p < 0.05) both in peanuts and chips. Comparing T1 and T2 only Yeasts showed significant growth in potatoes (p = 0.04). Between T0 and T2 we also found the growth of Coliforms bacteria in peanuts (p = 0.03).

Conclusions

We showed an increase in the microbial load associated with food handling, mostly of Enterococci. Long exposure time increased the likelihood of contamination and the possibility to exceed the dose for the occurrence of good outbreak. It is likely that offering small portions of handling food would reduce the manipulation by participants and the risk of food-borne outbreaks.

Key messages

Define the most frequent microrganisms could be associated with backed food and evaluate which one of these can exceed the dose for the occurrence of disease in long time. Reflect on the likelihood that the risk of food-borne outbreak caused by manipulation of happy hour participants, may result in an increase in hospital admissions.