Comparison of selective procedures for isolation and enumeration ofLegionellaspecies from hot water systems

Abstract

E. LEONI AND P.P. LEGNANI. 2001. Various sample pre‐treatment techniques and different growth media for the isolation of Legionellae from hot water supplies in public buildings were compared. A total of 102 hot water samples from taps and showers was examined. The highest recovery frequency was obtained with the heat pre‐treatment method and using the selective medium GVPC. However, the results differed according to the concentration of legionellas. In the case of low plate counts (≤5000 cfu l−1), the heat pre‐treatment technique gave a significantly higher percentage of positive samples compared with other techniques (P < 0·05). With increasing concentration, the differences between the procedures decreased until they became statistically not significant for concentrations above 50 000 cfu l−1. The direct inoculum method allowed a significantly higher detection of concentrations (P < 0·001) compared with heat and acid decontamination methods, which brought about a 67–68% reduction in detectable Legionellae. Heat decontamination techniques show greater sensitivity and specificity. However, they underestimate the number of legionellas. In environmental surveillance programmes, this underestimate must be taken into consideration when assessing the health risk.

Identification of Legionella spp. in Environmental Water Samples by ScanVIT-Legionella™ Method in Spain

“…In our case, in 6 samples the results were higher with culture technique too (54.54 %). These contrasting results between authors could be due to differences in the examined water in terms of higher / lower level of contamination, presence / absence of concomitant microbial flora, supply and structure type, all factors possibly influencing the bacteria detection by the culture method [36]. Other reasons of this difference could be attributed to the different pore size of the filter membranes (0.45 lm for the ScanVIT test and 0.22 lm for culture); decontamination of the filter with acid buffer; growth of only on MWY agar containing antibiotics and antifungals.…”

High Diversity and Abundance of Legionella spp. in a Pristine River and Impact of Seasonal and Anthropogenic Effects

“…in all samples throughout the year. Indeed, it is widely recognized that some Legionella species, such as L. lytica, and other Legionella-like amoebal pathogens (LLAPs) remain unculturable on the medium normally used to grow Legionella and on other media tested (29,39). Although L. pneumophila could be quantified by the culture method, this species could not be quantified reliably by qPCR because the concentrations fell below the QL.…”

Bacteria electrical detection using 3D silicon nanowires based resistor

“…Classical methods for the detection of pathogens are polymerase chain reaction (PCR) [2], colony culture and enumeration methods [3], immunological methods [4] and more recently detection of pathogens bacteria using mass spectrometry [5]. The main drawbacks of these methods are significant analysis time, high cost equipment, and complexity of detection process.…”