Heterotrophic Plate Count Can Predict the Presence of Legionella spp. in Cooling Towers
Abstract
:1. Introduction
2. Materials and Methods
2.1. Water Samples
2.2. Culture Methods and Methodology
2.3. Statistical Analyses
3. Results and Discussion
3.1. Results of HPC and Legionella spp. and Values of Residual Chlorine and Temperature
3.2. Relationship between HPC and Legionella Concentrations
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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Microbiological Parameter/Frequency | Threshold | Interventions |
---|---|---|
HPC/monthly * | ≤10,000 cfu/mL | Continue with the management plan |
>10,000 cfu/mL | Check the efficacy of disinfection (doses and biocide) and perform immediate sampling for Legionella analysis | |
Legionella spp./quarterly * | ≤100 cfu/L | Continue with the management plan |
>100 cfu/L | >100 ≤1000 cfu/L review the management plan, introducing corrections if needed, and take new samples after 15 days * (until Legionella levels are ≤100 cfu/L) | |
>1000 ≤10,000 cfu/L review the maintenance program, perform cleaning and disinfection, and resample as above | ||
>10,000 cfu/L shut down the cooling tower |
Type of Samples (n/%) | HPC Positive Samples (%) | Geometric Mean (GM) | Free-Residual Chlorine (Mean mg/L) | Mean Temperature (Range) | |
---|---|---|---|---|---|
HPC (cfu/mL) | Legionella (cfu/L) | ||||
Legionella negative (LN) (1138/82.7) | 95.1 % | 83 * | ─ | 1.003 | 22.4 °C (2–40) |
Legionella positive (LP) (238/17.3) | 100 % | 135 * | 177 | 0.93 | 20.9 °C (5–35) ** |
Range HPC (cfu/mL) | Number of Samples (%) | Number (%) of Legionella-Positive Samples Distributed by Their Concentration Range (cfu/L) | ||||
---|---|---|---|---|---|---|
≤ 100 | >100 ≤1000 n = 74 | >1000 ≤10,000 n = 33 | >10,000 n = 8 | Total 115/238 (48.3) | ||
≤ 100 | 128 (53.7) | 64 (50.0) | 48 (37.5) | 15 (11.7) | 1 (0.8) | 64 (55.7) |
100 ≤ 1000 | 47 (19.9) | 19 (40.4) | 15 (31.9) | 10 (21.3) | 3 (6.4) | 28 (24.3) |
>1000 ≤ 10,000 | 35 (14.8) | 12 (34.3) | 11 (31.4) | 8 (22.9) | 4 (11.4) | 23 (20.0) |
>10,000 | 28 (11.6) | 12 (42.9) | 11 (39.3) | 2 (7.1) | 3 (10.7) | |
Total (%) | 238 (100) | 107 (45.0) | 85 (35.7) | 35 (14.7) | 11 (4.6) |
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Sanchis, M.; Inza, I.; Figueras, M.J. Heterotrophic Plate Count Can Predict the Presence of Legionella spp. in Cooling Towers. Pathogens 2023, 12, 466. https://doi.org/10.3390/pathogens12030466
Sanchis M, Inza I, Figueras MJ. Heterotrophic Plate Count Can Predict the Presence of Legionella spp. in Cooling Towers. Pathogens. 2023; 12(3):466. https://doi.org/10.3390/pathogens12030466
Chicago/Turabian StyleSanchis, Marta, Isabel Inza, and Maria José Figueras. 2023. "Heterotrophic Plate Count Can Predict the Presence of Legionella spp. in Cooling Towers" Pathogens 12, no. 3: 466. https://doi.org/10.3390/pathogens12030466
APA StyleSanchis, M., Inza, I., & Figueras, M. J. (2023). Heterotrophic Plate Count Can Predict the Presence of Legionella spp. in Cooling Towers. Pathogens, 12(3), 466. https://doi.org/10.3390/pathogens12030466