TABLE 3.

Linear regression-based correlations and relationships between log-transformed data on biofilm characteristics, including Legionella colony counts, for biofilms in the boiler biofilm monitor for groundwater supplies A, B, and C

Comparison (n)a	All data			Data for water supplyb
				A		B		C
	Mean slope ± SE	R2 value	P value	R2 value	P value	R2 value	P value	R2 value	P value
TCC vs HPC (60)	1.07 ± 0.07	0.78	<10−20	0.55	<10−3	0.20	<0.05	0.64	<10−3
TCC vs ATP (68)	1.05 ± 0.07	0.78	<10−20	0.53	<10−3	0.41	<10−3	0.79	<10−5
HPC vs ATP (111)	0.84 ± 0.04	0.78	<10−20	0.65	<10−8	0.22	<10−3	0.59	<10−6
Legionella count vs TCC (50)	2.09 ± 0.26	0.57	<10−9	0.26	NS	0.31	<0.01	0.27	NS
Legionella count vs HPC (80)	1.69 ± 0.19	0.49	<10−12	0.29	0.01	0.04	NS	0.23	0.01
Legionella count vs ATP (180)	1.58 ± 0.09	0.62	<10−12	0.19	<0.01	0.18	<10−4	<0.01	NS
Legionella countavg vs ATPavg (9)c	2.00 ± 0.42	0.76	0.002	NA	NA	NA	NA	NA	NA
Legionella countavg vs ATPavg (10)d	1.99 ± 0.26	0.88	5 × 10−5	NA	NA	NA	NA	NA	NA

^an = number of data pairs.

^bNS, not significant (P > 0.05); NA, not applicable.

^cData pairs for location A_T were excluded from the calculations.

^dData pairs for location A_T were excluded, and data for growth of an L. pneumophila serogroup 1, sequence type 1 strain in a biofilm on soft PVC (18) were included (Fig. 3).