Journal of Korean Society of Dental Hygiene (J Korean Soc Dent Hyg)

4

Weeks in Review

2

Weeks to Publication

Journal of Korean Society of Dental Hygiene
Open access, Peer Reviewed

pISSN 2287-1705, eISSN 2288-2294

Original Article

Infection control-related factors associated with microbial contamination in dental unit waterlines

Ju-Yeon Cho1*, Geun-Yeong Kim2*, Joon Sakong3, Eun-Kyong Kim4†, Eun-Young Park5†

1Department of Dentistry, Dongsan Hospital, Keimyung University
2Department of Public Health, Graduate School of Environment and Public Health Studies, Yeungnam University
3Department of Preventive Medicine and Public Health, College of Medicine, Yeungnam University
4Department of Preventive Dentistry, School of Dentistry, Kyungpook National University
5Department of Dentistry, College of Medicine, Yeungnam University

Correspondence to Eun-Kyong Kim, Department of Preventive Dentistry, School of Dentistry, Kyungpook National University, 2177 Dalgubeol-daero, Jung-gu, Daegu-si, 41944, Korea. Tel: +82-53-660-6870, Fax: +82-53-423-2947, E-mail: ekkim99@knu.ac.kr

Correspondence to Eun-Young Park, Department of Dentistry, College of Medicine, Yeungnam University, 170 Hyeonchung-ro, Nam-gu, Daegu-si, 42415, Korea. Tel: +82-53-620-3282, Fax: +82-53-629-1772, Email: acidic@yu.ac.kr

*The author is a co-first author.

Volume 25, Number 5, Pages 373-80, October 2025.
J Korean Soc Dent Hyg 2025;25(5):373-80. https://doi.org/10.13065/jksdh.2025.25.5.2
Received on July 08, 2025, Revised on July 21, 2025, Accepted on August 04, 2025, Published on October 30, 2025.
Copyright © 2025 Journal of Korean Society of Dental Hygiene.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License(http://creativecommons.org/licenses/by-nc/4.0).

Abstract

Objectives: Although dental unit waterlines (DUWLs) could harbor biofilms that pose an infection risk to patients and staff, data on infection control factors related to the microbial contamination of DUWLs in Korea remains limited. Therefore, in this study, we aimed to analyze the microbial load in DUWL according to infection control factors using a survey. Methods: In this cross-sectional study, we surveyed 58 dental institutions for characteristics (chair number, daily patient load, and accreditation status) and infection-control status (written guidelines, designated managers, monitoring, and staff training). Simultaneously, we examined the microbial contamination levels of the high-speed handpieces and three-way air-water syringes via water sampling, expressing contamination as arithmetic and geometric means (GM)±geometric standard deviation (GSD). We used the Mann-Whitney U test to compare bacterial contamination according to institutional characteristics and infection control factors (p<0.05). Results: Overall GM contamination was 1,141 and 411 CFU/mL for high-speed handpieces and syringes, respectively, exceeding the CDC guideline of ≤500 CFU/mL. We observed significant differences in microbial loads according to the institution type, unit chair count, and average patient count. Moreover, the existence of infection control guidelines revealed significant effects. Conclusions: DUWL microbial quality varied according to the clinic size and infection control program quality. Institutions with detailed guidelines, routine surveillance, and skill-based training have achieved better microbial control. Standardized guidelines and incentivized training could help reduce infection control gaps, especially in small private clinics.

Keywords

Biofilm, Dental clinic water quality, Dental unit waterlines, Infection control

Introduction

The waterline of dental clinics are critical components that require careful management to ensure patient safety [1]. Dental unit waterlines (DUWLs) can harbor dangerous microbial biofilms, which might proliferate rapidly in the stagnant environment of these systems [2,3]. These biofilms might present substantial risks to both patients and the medical team, underscoring the need for effective waterline management to uphold rigorous infection control standards in dental practices [4-7].

Although the importance of maintaining proper water quality is widely recognized, significant variation exists in how dental clinics implement guidelines for cleaning, flushing, and monitoring their waterlines [8,9]. Some previous studies conducted across multiple countries have revealed significant discrepancies between recommended protocols and actual practice [10]. Resource limitations and inconsistent protocols in dental offices often result in inadequate management of dental unit waterlines (DUWLs) [11]. The study by the ADA Science & Research Institute highlighted that while many dental professionals acknowledge the importance of infection control, they encounter barriers such as knowledge gaps, time constraints, financial limitations, and staffing shortages, which impede proper DUWL management [12]. Consequently, these challenges may lead to suboptimal management practices for DUWL, increasing the risk of infection for both patients and dental healthcare workers.

Addressing these barriers requires a multi-faceted approach that includes improved training programs, better resource allocation and the development of standardized protocols to ensure consistent practices across all dental settings. [12]. To this end, it can be said that the first task is to identify vulnerable conditions for infection control related to microbial loads of DUWLs. Gathering data through surveys as well as microbial contamination examinations might be helpful to understand the challenges faced by dental professionals in maintaining optimal waterline management.

For example, it may be useful to consider various factors such as the size and operation of the facility, the presence of dedicated infection managers, and the availability of relevant manuals and training programs. Especially, trained infection control managers have been demonstrated to have a substantial impact on enhancing compliance with guidelines and protocols [13]. In addition, access to up-to-date manuals and effective training programs is crucial for ensuring that dental professionals are well-informed about infection control measures [12].

Therefore, by analyzing microbial contamination level in DUWLs in conjunction with survey data, oral healthcare providers or dental infection control specialists can better understand the impact of their efforts and identify gaps that need to be addressed. To achieve this objective, we conducted a study aimed at evaluating the relationship between various factors associated with infection control and the bacterial load of water used for dental treatment in clinics.

Methods

1. Study design

This cross-sectional study was designed to assess waterline management related factors including practices, guidelines, and existence of assigned managers in dental clinics through a comprehensive questionnaire survey, which had been conducted over 2-month period from 2020 Feb. This study was approved by the Institutional Review Board (IRB) of Yeungnam University (IRB No. YU2019-06-008-002). Informed consents were obtained from a representative director of dental clinics prior to their involvement in the study. Finally, 58 dental clinics in Daegu metropolitan city were included in this study. The required sample size was calculated using G*power 3.1 software. With a significance level (α) of 0.05, an effect size of 0.8, and a statistical power of 0.8, the minimum required sample size for t-test was determined to be 52 dental clinics. To account for potential non-responses and incomplete surveys, the target sample size was decided as 58 clinics.

2. Questionnaire survey

The survey was conducted using a self-administered method through in-person visits, following sufficient prior explanation and understanding about study. Participants completed and sealed the questionnaire by themselves. The questionnaire comprised a total of 13 items and consists of three main sections addressing key aspects of waterline management The first section focuses on general characteristics of dental institutions, including type of institution, dental chair count, operation period, average patient count per day, and participation in medical institution accreditation assessment (7 items). The second section examines specific waterline management practices, including monitoring for infectious control status, existence of assigned infection control manager, and education for infectious control (3 items). The third section assesses knowledge and attitudes toward waterline management, including existence of infectious control guidelines, detailed guidelines according to infectious control target, and type of education for infectious control such as lecture only, lecture with practice or e-lecture only (3 items). Most questions were multiple-choice or yes/no type, while a few required short written answers (e.g., year of establishment, replacement period of dental units).

At each participating institution, one infection control manager was asked to complete the questionnaire; if no such staff was assigned, a worker responsible for sterilization or environmental hygiene was designated as the respondent. The completed forms were sealed in envelopes and collected on-site by the research team.

3. Water sampling

In addition to questionnaire data collection, water samples were collected to assess microbial contamination levels. Samples were obtained from two components of each dental unit: high-speed handpieces and three-way air-water syringes. Prior to sample collection, a 30-second flush was performed to eliminate stagnant water from each component. Water samples were collected in sterile 100 mL bottles, with two samples taken from each dental clinic (one from each component). All samples were stored at 4°C in sterile cooling bags and transported to the laboratory within four hours to examine bacterial loads.

4. Microbiological analysis

The collected water samples underwent standardized microbiological analysis to assess bacterial contamination levels. First, the samples were serially diluted corresponding to plates yielding 30 to 300 colonies. Then, R2A agar (Difco™, Becton, Dickinson and Company, Sparks, MD, USA), which was pre-sterilized and maintained at 44-46 °C, was dispensed into petri dishes and mixed with the diluted samples. R2A agar is a low-nutrient medium specifically developed for the recovery of heterotrophic bacteria from potable water systems such as tap water. After solidification of the medium at 21.0±1.0°C for 72±3 hours. Although R2A agar is commonly incubated for 5-7 days, previous studies have demonstrated that stable colony counts can be obtained within 72 h under these conditions; therefore, a 3-day incubation was adopted in this study. [13,14] The number of bacterial colonies formed on each plate was counted. Colony counts within the valid dilution range were averaged, and the result was multiplied by the corresponding dilution factor to calculate the number of colony-forming units (CFU) per mL to yield bacterial load.

5. Statistical analysis

All collected data was analyzed using IBM SPSS program (ver. 19.0; IBM Corp., Armonk, NY, USA). Mann-Whiteny U or KruskalWallis test was employed to compare bacterial contamination levels according to general characteristics or infection control characteristics of dental institutions, respectively. After Kruskal-Wallis test, if result was significant, Mann-whitney + Bonferroni was analyzed for nonparametric post-hoc tests. As bacterial loads, Arithmetic mean as well as Geometric mean±Geometric standard deviation was used. Because when the data distribution is skewed or exhibits high variability, the geometric mean and standard deviation (STD) could be used as statistical indicators to more accurately represent the central tendency and dispersion than the simple arithmetic mean [15]. Statistical significance will be set at p<0.05 for all analyses.

Results

At <Table 1>, microbial contamination levels were compared according to general characteristics of dental institutions. Dental clinics exhibited significantly higher microbial loads in handpieces (AM: 13,073 CFU; GM±GSD: 1,885±7.40) compared to dental hospitals (AM: 2,263 CFU; GM±GSD: 373±10.96) (p<0.05). Similarly, air-water syringes in dental clinics showed higher contamination levels (AM: 7,995 CFU; GM±GSD: 635±11.28) compared to larger hospitals (AM: 1,271 CFU; GM±GSD: 156±13.24), though this difference did not reach statistical significance. Also, according to both unit chair count and patient count per day, there were significant differences in microbial contamination levels. Dental institutions with 11-20 unit-chairs or having fewer patients than 50 patients per day showed the most contaminated handpiece and air-water syringe in geometric mean (p<0.05). However, operation period or healthcare accreditation did not relate to microbial contamination levels at both handpiece and air-water syringe.

The microbial contamination levels demonstrated significant variation depending on infection control characteristics implemented in dental institutions, as summarized in <Table 2>. Institutions with designated infection control personnel exhibited lower microbial loads in handpieces and air-water syringes compared to clinics without designated personnel. However, these differences were not statistically significant. In contrast, the presence of infection control guidelines yielded statistically significant reductions in microbial contamination. Institutions with infection control guidelines reported substantially lower microbial loads in handpieces (GM±GSD: 562±11.56) compared to those without guidelines (GM±GSD: 2,754±4.99, p=0.018). Similarly, air-water syringes in Institutions following guidelines had lower contamination levels (GM±GSD: 215±1,260) than those without guidelines (GM±GSD: 912±10.47, p=0.032). In addition, detailed guidelines according to infectious control target, monitoring for Infectious control status, and education for infectious control showed similar significant results, in which institution having detailed guidelines, doing monitoring for infectious control status, or education for infectious control showed lower microbial loads in both handpiece and air-waysyringe than those did not.

Table 1. Microbial load according to general characteristics of dental institution

Characteristics N(%) Handpiece Air-water syringe
AM GM±GSD p* AM GM±GSD p*
Type of dental institution
Clinic 40(69.0) 13,073 1,885±7.40 0.014 7,995 635±11.28 0.067
Hospital 18(31.0) 2,263 373±10.96 1,271 156±13.24
Operation period (yr)
≤5 10(17.2) 7,987 1,184±24.74 3,525 438±31.04
6-10 11(19.0) 1,902 478±12.03 0.505 1,291 385±14.11 0.445
11-15 16(27.6) 24,230 1,800±5.67 15,548 307±17.78
≥16 21(36.2) 3,580 1,248±1.25 2,118 514±5.97
Dental chair count
≤10 39(67.2) 12,934 1,637±8.17b 7,915 601±10.65b
11-20 6(10.3) 7,470 2,383±6.21ab 0.047 4,663 2,867±2.87b 0.000
≥21 13(22.4) 1,108 275±10.64a 464 53±10.37a
Average count of patients per day
≤50 37(63.8) 14,607 2,045±8.96b 8,861 761±11.74b
51-100 8(13.8) 1,158 871±2.30b 0.01 1,006 416±6.11ab 0.012
≥101 13(22.4) 1,071 256±10.43a 522 70±11.38a
Participation in medical institution accreditation assessment
Yes 4(6.9) 963 288±6.76 93 89±1.41
No 54(93.1) 10,367 1,263±9.44 0.141 6,339 460±13.38 0.061
Total 58(100.0) 9,718 1,141±9.40 5,909 411±12.64

N: Number of responding dental institutions
AM: Arithmetic means of microbial load
GM, GSD: Geometric mean and Geometric standard deviation of microbial load
*by mann-whiteny U or Kruskal-wallis test according to the number of groups compared (2 or 3, 4)
Bonferroni method post hoc test (a<b)

Table 2. Microbial load according to infection control characteristics of dental institution

Characteristics N(%) Handpiece Air-water syringe
AM GM±GSD p* AM GM±GSD p*
Assigned infection control manager
Yes 33(56.9) 13,925 817±14.54 0.258 8,974 319±18.75 0.233
No 25(43.1) 4,166 1,771±4.13 1,862 571±6.73
Infectious control guidelines
Yes 32(55.2) 2,972 562±11.56 0.018 1,616 215±12.60 0.032
No 26(44.8) 18,022 2,754±4.99 11,191 912±10.47
Detailed guidelines according to infectious control target
Yes 27(46.6) 2,967 505±12.33 0.021 1,766 183±14.70 0.024
No 31(53.4) 15,598 2,317±5.57 9,516 830±9.09
Monitoring for infectious control status
Yes 28(48.3) 1,740 409±9.61 0.001 1,195 132±14.20 0.002
No 30(51.7) 17,164 2,968±5.88 10,308 1,180±6.86
Education for infectious control
Yes 36(62.1) 12,255 610±10.65 0.001 5,771 239±16.05 0.052
No 22(37.9) 7,203 3,172±4.92 6,133 998±6.14
Type of education for infectious control
No 22(37.9) 7,203 3,172±4.91 0.009 6,133 998±6.14b 0.043
Lecture only 14(24.1) 2,502 728±5.28 1,915 442±6.27b
Lecture/practice 9(15.5) 1141 233±14.35 422 48±14.45a
E-lecture only 13(22.4) 27,684 981±15.78 13,627 371±29.62b
Total 58(100.0) 9,718 1,141±9.40 5,909 411±12.64

N: Number of responding dental institutions
AM: Arithmetic means of microbial load
GM, GSD: Geometric mean and Geometric standard deviation of microbial load
*by mann-whiteny U or Kruskal-wallis test according to the number of groups compared (2 or 3, 4)
Bonferroni method post hoc test (a<b)

Discussion

This study evaluated microbial contamination in dental unit waterlines (DUWLs) across 58 dental institutions and analyzed how their general characteristics and infection-control–related factors influenced contamination levels of handpiece and air-water syringe. The overall geometric mean (GM) of microbial lode was 1,141 CFU/mL for handpieces and 411 CFU/mL for air–water syringes, in which microbial lode of handpieces exceeded the U.S. CDC guideline of ≤500 CFU/mL [16]. In case of GM in handpiece, contamination was relatively high in the clinics (11-20 chairs) or treated ≤50 patients per day, which is exceeding U.S. CDC guideline [16]. In contrast, large facilities with ≥21 chairs met the safety criteria.

According to previous study, bacterial loads in DUWLs can exceed 10⁴ CFU/mL [17]. Several institutions in the present study also surpassed this threshold. Pankhurst et al. [4] highlighted the risk of opportunistic pathogens such as Legionella spp. during routine dental procedures, and a recent multinational survey by Vinh et al. [10] reported that 46% of facilities continued treatment even when counts exceeded 500 CFU/mL. The high exceedance rate in Korean small-scale clinics mirrors these global shortcomings. The CDC and American Dental Association recommend maintaining <500 CFU/mL even for non-surgical care [16]. Small facilities treating ≤50 patients per day showed microbial load of GM= 2,045 CFU/mL, far above the standard. These clinics often have limited staff and budgets, which might make it difficult to maintain consistent flushing or chemical disinfection protocols [18,19]. Deploying automated DUWL maintenance systems and offering financial or regulatory incentives could help sustain infection-control activities.

Also, dental institutions having infectious control guidelines exhibited 4.9-fold and 4.2-fold lower contamination in handpieces and air–water syringes, respectively (p<0.05). Regular monitoring, detailed protocols, and staff education were likewise associated with significant reductions, underscoring the importance of infection control programs. The mere presence of an assigned infection control manager did not reach statistical significance, suggesting that human resources alone are insufficient without accompanying detailed infection control programs. These findings therefore corroborate the core CDC guidance that written protocols alone are insufficient unless coupled with ongoing surveillance and feedback loops [20,21]. Therefore, the data might support a multicomponent strategy—written, detailed protocols, ongoing surveillance, and hands-on education acting synergistically to minimize reservoirs of pathogens in DUWLs.

Strengths of the present study include the integration of field-collected water samples with organizational survey data, enabling simultaneous assessment of structural determinants and microbial contamination outcomes. Especially, all DUWL samples were stored at 4℃ and processed within 4 h, limiting bacterial regrowth during the sampling-transport-analysis chain and improving data reliability [22-24]. Finally, this is the largest Korean DUWL microbial survey to date to examine 58 dental institutions, to our knowledge.

However, limitations are: (1) the cross-sectional design precluded evaluation of seasonal or longitudinal trends; (2) the regional sample (one city) may limit generalizability; (3) CFU enumeration did not capture viral or fungal constituents of the biofilm; and (4) Logistic regression analysis was not performed due to the limited sample size; therefore, further studies with a larger number of institutions are necessary. Future multicenter cohort studies incorporating molecular techniques (e.g., 16S rRNA sequencing) are warranted.

In conclusion, several suggestions could be made based on the result of this study. First, given that infectious control guidelines were the most affecting factor, national dental associations should distribute and mandate standardized manuals. In addition, specialized hands-on education program blended learning (lecture + practice) could attribute to lower contamination.

Conclusions

This study evaluated microbial contamination levels in dental unit waterlines (DUWLs) across multiple dental institutions to identify key infection control factors associated with water quality. The findings provide important insights into how institutional size and infection control comprehensiveness affect microbial contamination in clinical environments.

1. Microbial contamination of DUWLs varies significantly by institution size and the comprehensiveness of infection-control systems.

2. Only the combination of written protocols, regular monitoring, and skills-based training achieved water quality ≤500 CFU/mL.

In conclusion, the results highlight the need for integrated infection-control frameworks that combine structured protocols, continuous surveillance, and practical staff education. Establishing standardized guidelines and expanding training programs nationwide will be crucial to sustaining safe and reliable dental waterline management.

Notes

Author Contributions

Conceptualization: J Sakong; Data collection: KY Kim; Formal analysis: EK Kim; Writing-original draft: KY Kim; Writing-review & editing: JY Cho, EY Park, EY Kim

Conflicts of Interest

The authors declared no conflicts of interest.

Funding

None.

Ethical Statement

This study was approved by the Institutional Review Board (IRB) of Yeungnam University (IRB No: YU2019-06-008-002).

Data Availability

Data can be obtained from the coauthor.

Acknowledgements

None.

References

  1. Samaranayake L, Fakhruddin K, Sobon N, Osathanon T. Dental unit waterlines: disinfection and management. Int Dent J 2024;74(Suppl2):S437–S45. https://doi.org/10.1016/j.identj.2024.07.1269

  2. Kgabi SP, Mthethwa SR. The effect of A-dec ICX TM on microbiological water quality in self-contained dental units’ water systems. South African Dental Journal 2020;75(7):367–72. https://doi.org/10.17159/2519-0105/2020/v75no7a3

  3. Barbot V, Robert A, Rodier MH, Imbert C. Update on infectious risks associated with dental unit waterlines. FEMS Immunol Med Microbiol 2012;65(2):196–204. https://doi.org/10.1111/j.1574-695X.2012.00971.x

  4. Pankhurst CL. Risk assessment of dental unit waterline contamination. Prim Dent Care 2003;10(1):5–10. https://doi.org/10.1308/135576103322504030

  5. Hikal W, Kačániova M, Hussein DE, Ghit A, Smaoui S, Aleem M, et al. Dental unit waterlines and health risks of pathogenic microbial contamination: an update review. Journal of Biological Studies 2023;6(4):282–98. https://doi.org/10.62400/jbs.v6i4.8729

  6. Liaqat I, Sabri AN. Biofilm, dental unit water line and its control. Afr J Clin Exp Microbiol 2011;12(1):15-21. https://doi.org/10.4314/ajcem.v12i1.61041

  7. Canares G, Allison D. Dental unit waterlines. In: DePaola LG, Grant LE, ‘editors’. Infection control in the dental office: a global perspective. Cham: Springer International Publishing; 2020: 157–67. https://doi.org/10.1007/978-3-030-30085-2_11

  8. Murdoch-Kinch CA, Andrews NL, Atwan S, Jude R, Gleason MJ, Molinari JA. Comparison of dental water quality management procedures. J Am Dent Assoc 1997;128(9):1235-43. https://doi.org/10.14219/jada.archive.1997.0400

  9. Baudet A, Lizon J, Martrette JM, Camelot F, Florentin A, Clément C. Dental unit waterlines: a survey of practices in Eastern France. Int J Environ Res Public Health 2019;16(21):4242. https://doi.org/10.3390/ijerph16214242

  10. Vinh R, Azzolin KA, Stream SE, Carsten D, Eldridge LA, Estrich CG, et al. Dental unit waterline infection control practice and knowledge gaps. J Am Dent Assoc 2024;155(6):515-25. https://doi.org/10.1016/j.adaj.2024.02.011

  11. O’DONNELL MJ, Boyle MA, Russell RJ, Coleman DC. Management of dental unit waterline biofilms in the 21st century. Future Microbiol 2011;6(10):1209-26. https://doi.org/10.2217/fmb.11.104

  12. Depaola LG, Mangan D, Mills SE, Costerton W, Barbeau J, Shearer B, et al. A review of the science regarding dental unit waterlines. JADA 2002;133(9):1199-206. https://doi.org/10.14219/jada.archive.2002.0361

  13. Lee SH, Park JH, Sakong J. Quantitative and qualitative analysis of microorganisms in dental unit water. J Korean Soc Dent Hyg 2018;18(4):433-40. https://doi.org/10.13065/jksdh.20180040

  14. American Public Health Association (APHA). Standard methods for the examination of water and wastewater. 23rd ed. Washington (DC): American Public Health Association; 2017: 35-41.

  15. World Health Organization. Statistical aspects of microbiological criteria related to foods: A Risk Manager’s Guide. Vol. 24. Rome: Food & Agriculture Organization of the United Nations; 2019: 112-8.

  16. Centers for Disease Control and Prevention. Best practices for dental unit water quality [Internet].[cited 2025 May 02]. Available from: https:// www.cdc.gov.

  17. Bayani M, Raisolvaezin K, Almasi-Hashiani A, Mirhoseini SH. Bacterial biofilm prevalence in dental unit waterlines: a systematic review and meta-analysis. BMC Oral Health 2023;23(1):158. https://doi.org/10.1186/s12903-023-02885-4

  18. American Dental Association. Dental unit waterlines: oral health topics [Internet].[cited 2025 May 02]. Available from: https://www.ada.org.

  19. Wu M, Shi Z, Yu X, Xu Y, Jin X, Zhang L, et al. Disinfection methods of dental unit waterlines contamination: a systematic review. J Med Microbiol 2022;71(6). https://doi.org/10.1099/jmm.0.001540.

  20. Baudet A, Lizon J, Lozniewski A, Florentin A, Mortier É. Bacterial contamination of new dental unit waterlines and efficacy of shock disinfection. BMC Microbiol 2024;24(1):529. https://doi.org/10.1186/s12866-024-03678-7

  21. Kohn WG, Collins AS, Cleveland JL, Harte JA, Eklund KJ, Malvitz DM. Guidelines for infection control in dental health-care settings-2003. MMWR Recomm Rep 2003;52(17):1-61.

  22. Centers for Disease Control Prevention. Summary of infection prevention practices in dental settings: basic expectations for safe care. Atlanta, GA: Centers for Disease Control and Prevention, US Deptment of Health and Human Services; 2016: 33–6.

  23. McCarthy JA. Storage of water samples for bacteriologic examinations. Am J Public Health Nations Health 1957;47(8):971-4. https://doi.org/10.2105/AJPH.47.8.971

  24. Poulsen CS, Kaas RS, Aarestrup FM, Pamp SJ. Standard sample storage conditions have an impact on inferred microbiome composition and antimicrobial resistance patterns. Microbiol Spectr 2021;9(2):e0138721. https://doi.org/10.1128/Spectrum.01387-21

PDF
Section