Table 4. Culture of Coxiella burnetii on Vero cell lines from dust sample homogenates collected inside a cave, Bizkaia, Spain, March 2021–February 2023 (n = 9).

Sampling date	Inoculated amount (GE/mL)	Culture on Vero E6 cell lines (GE/mL)
		Day 6 p.i.	Passage 1	Passage 2	Passage 3	Viable C. burnetii
Mar 2021	3.68 × 104	7.39 × 104	4.27 × 105	5.17 × 105	2.63 × 106	Yes
May 2021	3.56 × 104	8.56 × 103	Contaminated	Not performed
Aug 2021	4.67 × 107	8.17 × 107	1.31 × 108	1.29 × 108	4.76 × 107	Yes
Nov 2021	2.43 × 107	2.54 × 107	5.73 × 107	5.05 × 107	9.09 × 107	Yes
Feb 2022	3.96 × 106	4.91 × 106	1.35 × 107	1.27 × 107	1.94 × 107	Yes
May 2022	4.88 × 105	8.24 × 105	1.82 × 106	2.98 × 106	4.71 × 106	Yes
Sep 2022	1.78 × 106	2.46 × 106	2.94 × 106	8.59 × 105	1.27 × 106	No
Dec 2022	5.33 × 105	1.61 × 106	1.04 × 106	1.15 × 106	0	Yes
Feb 2023	6.47 × 105	8.65 × 105	2.04 × 105	3.45 × 105	0	No

GE: genome equivalents of C. burnetii determined by quantitative real-time PCR targeting the com1 gene; p.i.: post-inoculation.