Molecular Detection of Legionella in Water Samples

Detection of legionellae in environmental and building water samples by PCR has been centered on hospital and cooling tower water samples. Target genes included the 16S and 5S rRNA gene of Legionella spp. and the mip gene of L. pneumophila.

Compared to conventional culture, the published PCR protocols showed a sensitivity of 71.8% to 98.1% and 54.5% to 82.1% for the detection of legionellae and L. pneumophila, respectively. However, the main limitation of all PCR assays is the high prevalence of PCR inhibitors in water samples. The presence of waterborne PCR inhibitors that will be enriched during concentration of the water samples also limits the sample size and thus the sensitivity of the PCR assays. Nevertheless, legionellae were detected in 60% to 100% of culture-negative water samples in several studies.[12,14,15] Because of the labor- and time-intensive nature of Legionella culture and the presence of viable and infectious but nonculturable Legionellae and Legionella-like organisms in water samples, PCR methods are a valuable tool for the detection of legionellae in water samples. However, further studies are necessary to clarify the significance of PCR-positive but culture-negative

Table 1 Nucleic acid amplification tests for detection of legionellae in respiratory samples [bronchoalveolar lavage (BAL), sputum, bronchial washing]

Ref.

Target gene

Specificity

Type of test

Analytical sensitivity

PCR-positive per culture-positive samples

PCR-positive per culture-negative samples

Jaulhac et al.[18]

mip

L. pneumophila

PCR/Southern Blot

25 CFU/mL 50 fg DNA/PCR

8/8

7/60

Matsiota-Bernard et al.[20]

5S rRNA

mip

Legionella spp. L. pneumophila

EnviroAmp Legionella PCR kit (PCR/dot blot)

100 CFU/PCR

11/12

0/17

Jonas et al.[19]

16S rRNA

Legionella spp.

PCR/ELISA

100 CFU/mL 200 fg DNA/PCR

8/8

6/250

Bernander et al.[23]

mip

L. pneumophila

Nested PCR

1-5 CFU/PCR

13/14

0/33

Cloud et al.[16]

16S rRNA

Legionella spp.

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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