It should be noted that the population of CDK assay Legionella represent only the 0.01% of all the compost bacterial flora [21]. Table 1 Table 1 Percentage and no. of samples from wich Legionella spp. were recovered by culture and co-culture   Compost (n = 88) Air (n = 23)   Culture Co-culture Culture Co-culture Lp2-15 60.2% (53) 55.7% (49) – 39.1% (9) Lp1 25% (22) 11.4% (10) – 8.7% (2) Lp 6.8% (6) 3.4% (3) – - L. bozemanii 39.8% (35) 6.8% (6) – 4.3% (1) L. londiniensis 26.1% (23) – - – L. micdadei 12.5% (11) 1.1% (1) – - L. oakridgensis 11.4% (10) – - – L. feeleii 3.4% (3) 2.3% (2) – - L. jamestowniensis 2.3% (2) – -

– check details L. birminghamensis 1.1% (1) – - – L. cincinnatiensis 1.1% (1) – - – L. sainthelensis

1.1% (1) – - – L. longbeachae – 1.1% (1) – - Lp1: L. pneumophila serogroup 1; Lp2-15: L. pneumophila serogroups 2–15. Lspp: undetermined Legionella species. Culture, however, yields apparently a better picture of the biodiversity of Legionella spp. in compost (Table  1); in fact, more species were recovered from each sample, whereas only one or two species per sample were enriched by co-culture (Additional file 1). Up to now, in Switzerland and in Europe mainly L. pneumophila was isolated from compost [4, 22], in contrast to Australia Selleckchem Fosbretabulin and Japan where L. longbeachae was frequently isolated from compost by the conventional culture method [3, 23]. Co-culture allowed enriching Lp1 by up to 6 log units from the starting bacterial cells number; the method is thus potentially useful in environmental monitoring, in particular when low Legionella

loads are expected (e.g. bioaerosol, rain and water). The presumptive concentration of Legionella bacteria in the bioaerosols of composting facility is between 0 to 103 Legionella per m3. The detection of Legionella in environmental samples such as soil and Carbachol compost is hampered by the presence of other microorganisms (mould and bacteria) that grow on selective media and may interfere with the Legionella growth, leading to an underestimation of the effective number of Legionella present in the sample [4]. PCR allows quantification, but the amplification of DNA of dead cells present in a sample makes the interpretation of results difficult; PCR is not an alternative for a reliable quantification of Legionella in environmental samples because humic acids present in the samples may inhibit the reaction [24, 25]. PCR has also been used to detect Legionella spp. in clinical samples, but sensitivity varies greatly (30-90%) depending on the type of specimen studied. In addition, the design of generic Legionella spp. primers is difficult [26]. Previous studies reported that the use of co-culture has allowed the isolation of L.