# How to Handle and Transport Water Samples for Microbiology Testing Water sample handling and transport for microbiology testing covers every step between the tap, well, or waterway and the laboratory bench. The objective is narrow and unforgiving. The bacterial count the laboratory reports should describe the water at the moment of collection, not the effects of a warm vehicle, an overfilled bottle, or a day on a shelf. Bacteria in water are few, stressed, and sensitive to time and temperature, so the sample is a living measurement that starts changing the second it leaves its source. This guide walks through the full workflow for routine bacteriological water testing, including total coliforms, *Escherichia coli* (E. coli), fecal coliforms, and heterotrophic plate count. It applies to drinking water compliance samples, treatment plant process monitoring, building water systems, outbreak investigations, and environmental or recreational water surveys. Time budget. Hands-on work runs 10 to 15 minutes per sample, roughly an hour for a ten-sample round including setup and documentation. Elapsed time matters more than hands-on time. Samples should reach the laboratory the same day, with delivery targeted within 8 hours of collection and a customary maximum of 24 hours. Routine culture results are ready 24 to 48 hours after receipt, and confirmatory steps can extend some results to 72 hours. ## What This Procedure Achieves and When to Use It Careful handling preserves two things. First, it preserves the true bacterial concentration, so a compliant sample is not failed by growth inside the bottle and a contaminated sample is not passed by die-off. Second, it preserves the integrity of the record, because compliance decisions and public health responses rest on documented times, temperatures, and chain of custody. Use this procedure whenever water will be cultured or quantified for bacteria: - Regulatory compliance sampling of treated drinking water - Sanitary surveys that follow water from the raw intake through each treatment stage to distribution points - Investigation of suspected waterborne illness or boil-water advisories - Routine monitoring in schools, healthcare facilities, and other buildings - Environmental, recreational, and source water surveys The stakes are visible in surveillance data. In a school-based survey across all six districts of Belize, 83% of tested schools had at least one water sample below the World Health Organization (WHO) recommended free chlorine residual, coliforms were detected in samples from 66% of schools, and E. coli from 22% [1]. Those findings informed public health responses only because the samples behind them were valid. ## The Principle Behind Careful Handling Water microbiology works with small numbers of organisms in a hostile matrix, which makes it fundamentally different from culturing a clinical specimen. Treated drinking water may carry a chlorine residual measured in fractions of a milligram per liter, and a compliant sample contains no detectable E. coli at all. The bacteria that are present have already survived nutrient scarcity, disinfection, and temperature swings, so they sit close to the edge of detectability. Three processes inside the bottle can move the count: - **Growth.** Warm temperatures and residual nutrients let survivors multiply and inflate counts. - **Die-off.** Cold shock, prolonged starvation, and continuing disinfectant action reduce counts. - **Loss of culturability.** Stressed cells can remain alive but stop dividing on culture media, so culture underestimates them. Fecal indicator bacteria (FIB) are the usual targets. These are organisms such as E. coli and fecal coliforms whose presence signals fecal contamination and whose concentration serves as a surrogate for pathogen risk. Because the entire result rests on a small number of cells, the two variables that most change an FIB result are holding time and storage temperature. Controlled holding trials confirm this. One study held river water and post-irrigation canal water in 500 mL aliquots for intervals from 0 to 216 hours under three storage treatments, processed the aliquots in triplicate by standard membrane filtration for E. coli and fecal coliforms, and found that stability depended on both temperature and water type [2]. The specific holding times appear in the storage section below, and they are the reason the clock on a water sample starts at collection, not at the bench. Chlorine is the second enemy inside the bottle. A chlorinated sample keeps disinfecting itself after collection unless the residual is neutralized with sodium thiosulfate, which is why pre-dosed bottles are standard for chlorinated sources. Finally, a valid result depends on the whole chain, not the bench alone. Quality management system (QMS) principles for water surveillance span sample collection, laboratory analysis, data interpretation, and reporting, and treating the workflow as one managed system is what makes results reproducible and comparable across sites [3]. Laboratory performance itself varies with testing method and accreditation status, which is why external quality assessment exists as a risk management resource for drinking water microbiology [4]. ## Materials and Reagents | Item | Specification or working concentration | Purpose | |--|--|--| | Sterile wide-mouth sample bottles | 120 to 250 mL, certified sterile, lot documented | Collection container | | Sodium thiosulfate | 10% (w/v) sterile solution, 0.1 mL per 120 mL bottle, or factory pre-dosed bottles | Neutralizes chlorine residual at the moment of collection | | Insulated rigid cooler | Large enough for bottles upright with packs around the walls | Transport vessel | | Frozen gel packs | Enough to hold 2-8°C for the full transit | Cold chain | | Cardboard or bubble wrap divider | Fits between packs and bottles | Prevents freezing on contact | | Cooler thermometer or logger | Reads to 1°C | Verifies transport temperature | | Nitrile gloves | Single use | Aseptic technique and personal protection | | 70% alcohol wipes or bleach wipes, lighter or alcohol lamp | For metal taps | Tap outlet disinfection | | Waterproof labels and permanent marker | Pre-applied where possible | Identification | | Chain-of-custody and field sheets | Program template | Documentation | | Field blank bottles | Filled with sterile buffered dilution water | Contamination control | | Free chlorine test kit | Strips or colorimetric, readable below 1 mg/L | On-site residual measurement | | Membrane filtration apparatus | 0.45 µm sterile membranes | Laboratory analysis | | Culture media | Chromogenic coliform agar or lauryl-based media, m-FC agar for fecal coliforms | Culture and confirmation | | Sterile buffered dilution water | pH 7.2 phosphate buffer or 0.1% (w/v) peptone water | Rinses, dilutions, field blanks | | Incubators | 35 ± 0.5°C and 44.5 ± 0.2°C | Culture conditions | **Safety note.** Alcohol lamps and bleach products carry burn and irritation hazards. Handle them under institutional safety rules, and keep bleach away from open sample bottles because splashes and vapor can contaminate or chemically alter the sample. ## Step-by-Step Water Sample Handling and Transport for Microbiology Testing ### Before You Leave the Laboratory ![Worked example of 0.1 mL of 10% (w/v) sterile sodium thiosulfate added per 120 mL sample bottle to neutralize chlorine.](/article-images/illustrations/water-sample-handling-transport-microbiology-testing-thiosulfate-dose.webp) 1. **Write the sampling plan.** Define each sampling point, the volume and tests required, the route order, and who collects what. A treatment plant survey typically moves from the raw water intake through each treatment stage to the auxiliary and distribution points, the design used in a Malaysian assessment that sampled 14 stations under American Public Health Association (APHA) procedures [5]. Reason: representative samples and an intact cold chain both depend on planning, and ad hoc rounds produce ad hoc results. 2. **Verify the bottles.** Confirm sterile, lot-documented bottles. For chlorinated sources, confirm each bottle carries sodium thiosulfate, either as a factory pre-dosed bottle or as 0.1 mL of 10% (w/v) sterile solution added aseptically per 120 mL bottle. Reason: residual chlorine keeps killing bacteria after collection and biases counts downward, and an undocumented bottle lot can seed false positives. 3. **Pre-chill the cooler.** Load gel packs and chill the empty cooler for at least 30 minutes before the round. Reason: cold thermal mass holds temperature far longer than packs dropped in at the door. 4. **Label in advance.** Apply waterproof labels with the sampling point, date, and test before leaving. Reason: field labeling is where transcription errors creep in, and an unlabeled bottle is uninterpretable no matter how well it was collected. ### Collecting the Sample 5. **Prepare the tap.** Remove aerators, screens, and point-of-use filters where the plan allows. Reason: aerators and screens trap biofilm and particles, so water passing through them does not represent the supply. 6. **Flush the line.** Run cold water for 2 to 3 minutes for routine distribution samples. Reason: flushing clears stagnant water and recently sloughed biofilm so the sample reflects the supply rather than the plumbing dead zone. Some investigations deliberately target stagnation, in which case the plan, not habit, decides the flush time. 7. **Disinfect the outlet.** Wipe the spout with 70% alcohol or a bleach wipe, then flame a metal spout briefly or run water to cool and rinse. Reason: the outlet surface carries biofilm that can seed the bottle during filling. 8. **Open the bottle aseptically.** Put on gloves, hold the cap face down without setting it down, and never touch the rim, the cap interior, or the inside of the neck. Reason: hands and surfaces transfer bacteria directly into the sample, and the field blank cannot catch what happens at every bottle. 9. **Fill to about 80% of capacity.** Leave roughly 2 to 3 cm of headspace below the cap. Reason: the laboratory must invert the bottle to redistribute bacteria before analysis, and a brim-full bottle cannot be mixed. 10. **Confirm the thiosulfate.** For chlorinated water, verify the powder or crystals are visible or that pre-dosing is documented on the bottle lot. Reason: without neutralization the disinfectant keeps working in the bottle and the count comes back falsely low. 11. **Measure free chlorine on site.** Record the residual with a test kit readable at low concentrations. Reason: the residual pairs with the microbiology at interpretation, and a chlorinated sample with no residual tells a different story than one with a healthy residual. 12. **Take environmental samples correctly.** For surface water, wells, and tanks, collect a grab sample 15 to 30 cm below the surface with the bottle mouth facing into the current, avoiding the surface film and stirred-up sediment. Reason: surface films and sediment are concentrated microhabitats that do not represent the water column. 13. **Collect a field blank.** At least once per round, open a bottle of sterile buffered water at the sampling site and handle it exactly like a real sample. Reason: a positive field blank exposes contamination from bottles, hands, or air before it corrupts real results. **Safety note.** Untreated surface water and wastewater can carry *Salmonella*, *Leptospira*, hepatitis A virus, and other pathogens. Wear gloves, avoid splashing, cover cuts, and wash hands after sampling. ### Cooling, Documentation, and Transport 14. **Pack upright and buffered.** Stand bottles upright in the pre-chilled cooler with a cardboard or bubble wrap layer between bottles and gel packs. Reason: direct contact with frozen packs can freeze the sample, and freezing damages cells and lowers culture recovery. 15. **Complete the record.** Fill in collection date and time, sampler, exact location, source type, chlorine residual, appearance, and recent weather including rain. Reason: metadata drives interpretation. Rainfall reshapes surface water contamination quickly, and a study along a major river supplying drinking water treatment plants found bacterial contamination varied significantly between dry and wet seasons as runoff spread pollutants [6]. 16. **Transport the same day.** Keep samples at 2-8°C and dark, deliver within 8 hours where possible, and never exceed the 24-hour customary maximum. Reason: holding time and temperature are the two variables that most move FIB results, as the storage data later in this article show. ### Receiving and Starting Analysis at the Laboratory ![Decision path checking a water sample for time, temperature, bottle condition, thiosulfate, volume and labels before it is accepted for culture.](/article-images/illustrations/water-sample-handling-transport-microbiology-testing-rejection-triage.webp) 17. **Log arrival and temperature.** Record the receipt time and measure the sample temperature. Accept samples at 2-8°C, with many programs tolerating up to 10°C for short transits. Reason: temperature abuse is a documented rejection ground. 18. **Screen against rejection criteria.** Reject or flag samples that exceed 24 hours from collection, arrive warm, leak, lack thiosulfate for a chlorinated source, contain too little volume for the requested tests, or arrive unlabeled or without times. Reason: an invalid sample wastes incubator space and can misdirect public health action. 19. **Mix before analysis.** Invert the bottle 25 times immediately before taking the aliquot. Reason: bacteria settle and adsorb to surfaces during transport, and mixing restores a uniform suspension so the aliquot represents the bottle. 20. **Start analysis without delay.** Filter 100 mL through a 0.45 µm membrane to a coliform medium and incubate at 35 ± 0.5°C for 22 to 24 hours, or inoculate a defined-substrate tray read as most probable number, or plate for heterotrophic plate count. Fecal coliform confirmation runs on m-FC agar at 44.5°C. Reason: the clock from collection to incubation is the holding time the result depends on. ### Field Tips That Save Samples - Pack a spare sterile bottle. Bottles crack and caps cross-thread. - Write times as you go, not at the end of the round. - Keep the field sheet in a plastic sleeve. Wet paper does not document anything. - Photograph the sampling point when the location is hard to describe. - If a bottle is compromised in the field, discard it and start again rather than topping it up. ## Controls and Microbiology Quality Checks Field controls: - **Field blank.** Sterile buffered water opened and poured at the site. A positive blank implicates bottles, hands, or air. - **Trip blank.** A sealed bottle of sterile water rides the cooler unopened and is cultured on arrival. A positive trip blank implicates the transport environment itself. - **Duplicate samples.** Collected at the frequency the program defines. Wide disagreement between duplicates flags mixing or homogeneity problems. Analytical controls: - Media sterility checks on each lot, and positive and negative culture controls with each run, typically a known E. coli strain as the positive control and a non-target organism to confirm media selectivity. - Incubator temperature logs, calibrated thermometers, and verified volumes for filtration and dilution. External quality assessment. Proficiency testing (PT) challenges laboratories with blinded samples of unknown content. The Canadian drinking water program operated by Proficiency Testing Canada with the Canadian Microbiological Proficiency Testing program has issued twice-yearly challenges since 1996, each consisting of four samples with unknown concentrations of E. coli and *Enterobacter* spp., and a cross-sectional analysis of 150 participating laboratories examined how detection accuracy varied with testing method and accreditation status [4]. Participation in such programs is a core risk management resource, because it tests the entire process the way a real sample would. Laboratory quality management. A QMS ties the chain together, from documented sampling procedures and training records through corrective action when a blank turns positive or a proficiency result misses. Water surveillance guidance frames the workflow as one managed architecture spanning collection, analysis, interpretation, and reporting, with cross-site comparability as the goal [3]. ## Expected Results and How to Read Them - **E. coli in drinking water.** The compliance target is no detectable E. coli in a 100 mL sample, expressed as 0 CFU/100 mL. Bhutan's national surveillance program applied that standard across 31 urban and 242 rural surveillance sites and found only 52.8% of urban samples compliant, with residual chlorine compliance at just 11.9% [7]. Any E. coli detection in treated water triggers repeat sampling and investigation under most programs. - **Total coliforms without E. coli.** This pattern usually points to biofilm growth or non-fecal coliforms in the distribution system rather than fresh fecal contamination. It still warrants a repeat sample and a look at the pipe run, residuals, and recent work on the system. - **Quantitative results.** Membrane filtration reports colony-forming units (CFU) per 100 mL. Defined-substrate trays report a most probable number (MPN) index with statistical confidence limits. Report samples with no growth as "not detected in 100 mL" or "<1 CFU/100 mL", never as zero bacteria, because the detection limit is one organism in the volume tested. - **Heterotrophic plate count (HPC).** High HPC values indicate regrowth or stagnant plumbing rather than fecal risk by themselves. They also interfere with coliform recovery, which is why high-HPC samples deserve dilution or smaller filtration volumes. - **Fecal coliforms.** Growth on m-FC at 44.5°C with the characteristic colony appearance presumptively indicates fecal coliforms, subject to confirmation per the method in use. - **Chlorine residual.** Read the microbiology against the field residual. A contaminated sample with a healthy residual suggests post-treatment contamination or a sampling artifact. A contaminated sample with no residual points to treatment or distribution failure. ## Troubleshooting Guide | Symptom | Likely cause | Fix | |--|--|--| | Sample arrives above 10°C | Under-packed cooler, long transit, thawed packs | Reject or flag per SOP, resample if the result drives action, add packs and a logger next round | | Field blank grows coliforms | Contaminated bottle lot, dirty technique, airborne contamination while pouring | Quarantine the bottle lot, review technique, collect blanks every round until clean | | Plates overgrown, colonies uncountable | Heavy background flora with no dilution | Filter smaller volumes (10 mL, 1 mL) or dilute in buffered water, high-load sources such as processing wash water can reach 2.54 × 10^8 CFU/mL [8] | | E. coli detected with a documented healthy chlorine residual | Post-collection contamination (missing thiosulfate, leaking cap) or genuine breakthrough | Check bottle integrity and dosing records, verify the residual reading, resample before enforcement | | Coliforms present, E. coli absent, repeatedly | Biofilm or non-fecal coliforms in plumbing | Flush longer, remove the aerator, resample, inspect the pipe run | | Duplicates disagree widely | Poor mixing, non-homogeneous sample, low-count sampling error | Invert 25 times before splitting, filter larger volumes, interpret low counts with MPN confidence limits | | No growth anywhere, including control organisms | Media or incubator failure, expired medium | Check incubator logs and media sterility, rerun with positive controls | | Counts far above site history | Stagnant tap, biofilm slough after plumbing work, disturbed sediment | Flush and resample, ask about recent system work | | Sample frozen on arrival | Direct contact with gel packs | Reject per SOP, add a divider and pack packs along the cooler walls | | Laboratory rejects the sample | Any rejection criterion above | Resample promptly, document the cause, correct the failed step | ## Variations for Special Sample Types **Point-of-use testing.** When transport is impossible, portable kits bring the test to the water. A Kampala program used a Portable Microbiology Laboratory to classify the disease risk of spring wells and boreholes on site and to correlate findings with typhoid admissions [9]. On-site testing trades the laboratory's controlled environment for immediacy, so field quality steps like blanks become even more important. **Defined-substrate MPN tests.** Enzyme-substrate tests read as MPN suit drinking water work with minimal dilution handling. The same approach covers total coliforms, fecal coliforms, and fecal streptococci, as applied across 200 tap water, groundwater, spring, and treatment plant samples in a Kashmir surveillance study [10]. **Somatic coliphages.** These are viruses that infect E. coli and serve as operational indicators of viral contamination risk and treatment performance, because bacterial indicators do not track viruses or protozoa well. EU Directive 2020/2184 added somatic coliphages as an operational parameter for raw water, measured under ISO 10705-2 methods. In a Polish survey of water treatment stations, coliphages appeared in 89% of surface water intake samples versus 8% of groundwater intakes, and in none of the treated waters [11]. Collection and transport follow the same bottle and cold chain rules, with larger volumes filtered when counts are expected to be low. **Molecular and viability methods.** Standard qPCR amplifies DNA from live and dead cells alike, which overestimates viable loads. A newer viability PCR reagent that chemically crosslinks DNA from non-viable cells, compatible with filter-concentrated water samples, demonstrated detection of viable *Legionella* reduction after heat treatment and targets building water safety applications [12]. Transport conditions for molecular assays follow each assay's validated requirements, which sometimes tolerate warmer transit than culture. **High-biomass industrial samples.** Wash water in fresh-cut produce processing carries bacterial loads far beyond drinking water ranges and demands dilution series with smaller filtration volumes [8]. The transport rules do not change, but the laboratory plan must anticipate the load. **Wastewater surveillance.** Composite and grab samples for population-level pathogen monitoring operate under the same QMS logic, with tiered analytical approaches from RT-qPCR to digital PCR and sequencing [3]. Biosafety practices rise accordingly, because raw sewage concentrates a much wider range of pathogens than environmental water. **Building water systems.** *Legionella* sampling uses liter-volume samples from hot water systems, cooling towers, and outlets, with thiosulfate for chlorinated water and the same cold chain as coliform work. ## Storage and Stability Notes - Hold samples cold at 2-8°C, dark and upright, and analyze the same day. Professional standards direct examination as soon as possible after collection, with 24 hours as the customary maximum when cold transport is maintained. - The stability data behind that ceiling come from controlled holding trials. Post-irrigation canal water kept E. coli and fecal coliform concentrations similar to time zero for at least 72 hours at 4°C, at least 48 hours under cycling conditions between roughly 4°C and 21°C, and at least 30 hours at 21°C, while river water samples showed a different, less forgiving pattern [2]. The safe window therefore depends on the water type, and the compliance limit does not expand just because the sample stayed cold. - Do not freeze water samples. Freezing damages cells and lowers culture recovery. - The cold chain buys stability, not authorization. A sample held 72 hours cold may read accurately and still be rejected for compliance purposes. ## Common Mistakes and Limitations The mistakes below account for most invalid water microbiology results: 1. Sampling chlorinated water in an undosed bottle. The count reads falsely low. 2. Overfilling the bottle. The laboratory cannot mix it, so the aliquot is not representative. 3. Sampling through hoses, filters, or softeners. The device, not the supply, gets tested. 4. Leaving the aerator on. Biofilm trapped in the screen seeds the sample. 5. Skipping or shortening the flush. Stagnant water overstates system contamination. 6. Warm transport. Ambient rides move counts in unpredictable directions. 7. Freezing samples against gel packs. Cell damage lowers recovery. 8. Missing times and residuals on the form. An uninterpretable result is a lost sample. 9. Topping up or reusing a bottle. Sterility is gone the first time it opens. 10. Reading one snapshot as the system's usual state. Contamination shifts with season and rainfall, so a single dry-day sample does not describe a monsoon-week system. 11. Sending samples the laboratory must reject. Late, warm, or unlabeled samples waste the entire trip. Limitations. Indicators are surrogates, so absence of E. coli does not prove absence of viruses or protozoa, which is why coliphage monitoring exists as a complementary parameter. Culture misses cells that are alive but no longer culturable, so counts can underestimate live populations, while molecular methods that detect DNA from dead cells can overestimate them. Laboratory accuracy varies with method and accreditation, so identical samples can yield different results across laboratories, which is exactly what proficiency testing is designed to expose. One negative sample does not clear a system, and one positive sample does not always condemn it. Individual sampling decisions belong with the responsible microbiologist and the program's documented procedures, and public health interpretation belongs with the responsible authorities. ## Frequently Asked Questions ### How cold should water samples be during transport? Keep samples at 2-8°C in an insulated cooler with gel packs, never in direct contact with frozen packs, and never above 10°C. Record the temperature when the sample reaches the laboratory. ### How long can a water sample wait before testing? Same day is the target, within 8 hours where possible, with 24 hours as the customary maximum for most programs. Cold transport protects the sample, but it does not extend the compliance limit. ### Why is there a tablet or powder in the bottle? That is sodium thiosulfate, which neutralizes the chlorine residual so disinfection stops the moment the bottle is filled. Without it, chlorine keeps killing bacteria in the sample and the count comes back falsely low. ### How full should the bottle be? About 80% full, leaving 2 to 3 cm of headspace. The laboratory inverts the bottle to mix before analysis, and a brim-full bottle cannot be mixed. ### Can I use my own bottle? No. Use sterile, certified, lot-documented bottles, pre-dosed with thiosulfate for chlorinated water. Household containers leak, contaminate, and give the laboratory no way to verify sterility. ### What makes a laboratory reject a water sample? Common rejection criteria are transport beyond 24 hours, arrival above 10°C, a leaking or broken bottle, missing thiosulfate in a chlorinated sample, insufficient volume, or missing labels and times. ### What is a field blank? A bottle of sterile water that you open and pour at the sampling site, then handle exactly like a real sample. If it grows bacteria, the problem is the bottles, the hands, or the air, not the water. ### Does PCR replace culture for water testing? Not for routine compliance work. Culture remains the standard for coliform and E. coli counts. Molecular methods add value for specific targets such as *Legionella*, and viability PCR is emerging to separate live from dead cells, but transport and interpretation rules differ by assay. ## Sources 1. [Assessment of Water Quality among Handwashing and Drinking Water Stations in Schools in Belize, 2022.](https://pubmed.ncbi.nlm.nih.gov/40199266/) 2. [Evaluation of fecal indicator bacteria concentration in different water sources, storage treatments, and holding times.](https://pubmed.ncbi.nlm.nih.gov/42563276/) 3. [Toward a quality-managed operational architecture for wastewater surveillance of zoonotic and emerging pathogens.](https://pubmed.ncbi.nlm.nih.gov/42429767/) 4. [Improving drinking water quality through proficiency testing-the impact of testing method and accreditation status on Escherichia coli detection by Canadian environmental testing laboratories.](https://pubmed.ncbi.nlm.nih.gov/38756531/) 5. [From tap to table: An assessment of drinking water quality in Perak, Malaysia.](https://pubmed.ncbi.nlm.nih.gov/38555880/) 6. [Spatio-temporal variation of microbial indicators of river water and treatment efficiencies of drinking water treatment plants along the upper Mahaweli river segment of Sri Lanka.](https://pubmed.ncbi.nlm.nih.gov/39753190/) 7. [Drinking water quality surveillance in Bhutan: trend and compliance (2017-2024).](https://pubmed.ncbi.nlm.nih.gov/41026136/) 8. [In the Depths of Wash Water: Isolation of Opportunistic Bacteria from Fresh-Cut Processing Plants.](https://pubmed.ncbi.nlm.nih.gov/39338959/) 9. [Assessing the environmental and climatic influences on the incidence of severe typhoid in Kampala, Uganda.](https://pubmed.ncbi.nlm.nih.gov/40245013/) 10. [Coliform pollution in drinking water sources of urban and semi-urban settings of Kashmir: a growing concern for public health.](https://pubmed.ncbi.nlm.nih.gov/42243458/) 11. [Assessment of occurrence of somatic coliphages in drinking water in Poland.](https://pubmed.ncbi.nlm.nih.gov/40586496/) 12. [A photoactivation-free viability PCR reagent for rapid, culture-independent detection of live bacteria.](https://pubmed.ncbi.nlm.nih.gov/41757880/)