Fecal Bacterial Enumeration
Fecal Bacterial Enumeration - Related Videos
01:18
Detection of Human Fecal Metabolites Using a Bacterial Biosensor
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2026
Begin with a bacterial biosensor culture suspended in a medium.These engineered bacteria produce a transcription factor that, upon binding to a specific fecal metabolite, activates a promoter associated with a fluorescent reporter gene.To this culture, add a filtered human fecal sample containing metabolites, such as lactate, that are involved in host-microbiome interactions.Dilute this mixture with a fresh medium to maintain an optimal reaction volume.Incubate without shaking to mimic the...
03:16
Processing of Infected Tissues for Bacterial Enumeration in a Mouse Co-Infection Model
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2026
Source: Lenhard, A., et al. A Mouse Model for the Transition of Streptococcus pneumoniae from Colonizer to Pathogen upon Viral Co-Infection Recapitulates Age-Exacerbated Illness. J. Vis. Exp. (2022)This video demonstrates the processing of lungs from a mouse co-infected with a pathogenic bacterium and a virus. Mincing, homogenizing, and plating the lung tissue allows quantification of bacterial load, indicating bacterial spread to the lungs and disease severity.
02:49
Assessing the Antimicrobial Potential of Bacteriocin-Producing Murine Fecal Bacterial Isolates
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2025
This video demonstrates the detection of bacteriocin-producing lactic acid bacteria derived from mouse fecal matter. The assay determines the antimicrobial activity of bacteriocin on specific bacterial strains.
10:58
Isolation of Fecal Bacteria from Water Samples by Filtration
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2023
Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona Demonstrating Author: Luisa Ikner The quality of water destined for use in agricultural, recreational, and domestic settings is of great importance due to the potential for outbreaks of waterborne disease. Microbial agents implicated in such events include parasites, bacteria, and viruses that are shed in high numbers in the feces of infected people and animals. Transmission to new and susceptible hosts may...
10:57
Culturing and Enumerating Bacteria from Soil Samples
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2023
Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona Demonstrating Authors: Bradley Schmitz and Luisa Ikner Surface soils are a heterogeneous mixture of inorganic and organic particles that combine together to form secondary aggregates. Within and between the aggregates are voids or pores that visually contain both air and water. These conditions create an ideal ecosystem for bacteria, so all soils contain vast populations of bacteria, usually over 1 million...
FAQs
Viable-cell counts indicate bacteria capable of producing colonies under the selected growth and incubation conditions. This makes the result useful for comparing living intestinal bacterial loads between experimental groups. In infection studies, changes in colony-forming units can therefore reflect altered colonization or microbial burden more directly than a measurement based only on bacterial components or genetic material.
Selective and nonselective agar provide different measurement windows. Nonselective plates support broader enumeration of bacteria able to grow under the incubation conditions, whereas selective plates help focus the count on organisms compatible with the chosen selection. Consequently, agar type affects which microbial changes become visible and must be considered when comparing results across experiments.
Homogenization distributes bacteria throughout the measured fecal portion, while serial dilution reduces the concentration to a level suitable for counting separate colonies. Together, these steps support calculation from countable plates rather than from crowded growth. Reporting the result as colony-forming units per gram also connects the measurement to the original sample amount.
Comparing colony-forming units across experimental conditions can show whether intestinal bacterial loads rise or fall during pathogen colonization or disease progression. These differences provide a quantitative link between microbial burden and host-related outcomes, including intestinal inflammation. The method is therefore useful for examining how infection-associated microbial shifts correspond with changes in immune or intestinal status.
A basic workflow requires a measured fecal sample, a way to homogenize it, dilution steps, agar plates, and incubation conditions. Aliquots from the dilutions are spread onto selective or nonselective agar, and resulting colonies are counted. The count is then converted to colony-forming units per gram, allowing results from samples of different measured amounts to be compared.
The method is useful when an experiment tests whether an antibiotic or probiotic changes intestinal microbial load. Counts obtained under treated and untreated conditions can indicate shifts in viable bacterial abundance, while comparisons with infection-related groups can show whether treatment corresponds with altered colonization. These measurements provide a quantitative outcome for interpreting microbial effects alongside host responses.
In immunology and infection studies, bacterial counts can be paired with observations of intestinal inflammation and disease progression. A change in viable bacterial load may help researchers examine relationships between microbial shifts and host responses, although the count itself is a microbial measurement. This pairing supports comparisons among infected, treated, and other experimental conditions.
Results represent colonies recovered from the measured sample under the chosen agar and incubation conditions, so comparisons should use consistent procedures and conditions. Counts are most informative when experimental groups are assessed using the same workflow and reported in comparable colony-forming units per gram. Interpretation should then connect microbial differences with colonization, treatment, inflammation, or disease outcomes.