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Related Concept Videos

Microbial Growth Measurement: Direct Methods01:23

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Direct methods for measuring microbial populations in a culture are essential tools in microbiology, providing quantitative data for various applications. Among these, microscopic counts, plate counts, and serial dilution are widely used techniques, each with unique principles and applications.Microscopic CountsMicroscopic counting involves the use of a Petroff-Hausser chamber, a specialized microscope slide with a grid and defined depth. By observing a liquid culture under a microscope,...
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Substituents on the benzene ring that direct an incoming electrophile to undergo substitution at the meta position are called meta directors. All meta directors either have a positive charge on the atom directly bonded to the ring or a partial positive charge. These groups function by withdrawing electrons from the ring through inductive and resonance effects. Consider the carbocation intermediates formed upon the addition of an electrophile on nitrobenzene at the...
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Directing Effect of Substituents: ortho–para-Directing Groups01:14

Directing Effect of Substituents: ortho–para-Directing Groups

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Ortho–para directors are substituent groups attached to the benzene ring and direct the addition of an electrophile to the positions ortho or para to the substituent. All electron-donating groups are considered ortho–para directors. They donate electrons to the ring and make the ring more electron-rich. The ring is therefore susceptible to the addition of electrophiles. Substituents such as amino, hydroxy, or alkoxy, containing lone pairs on the atom adjacent to the ring, donate...
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Directional Relays

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Directional relays, essential for managing unidirectional fault currents, enhance the safety and efficiency of power systems. On power lines equipped with directional relays, faults downstream (to the right) of the current transformer typically cause the fault current to lag the bus voltage by approximately 90 degrees, known as the forward direction. In contrast, upstream (left-side) faults may result in the fault current leading the bus voltage by nearly 90 degrees, termed the reverse...
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Directional Terms01:14

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Directional terms are essential for describing the relative locations of different body structures. For instance, an anatomist might describe one band of tissue as "inferior to" another, or a physician might describe a tumor as "superficial to" a deeper body structure. These terms often use comparative terms in pairs to trace out the relative locations of one body part to another or descriptions of body tissues like the deeper ones from superficially present with reference to...
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Direct Motor Pathways

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The direct motor pathways, also known as the pyramidal tracts, are a group of neural pathways that originate in the brain and descend through the spinal cord. They control the voluntary movement of the body. There are two major direct motor pathways: the corticospinal and the corticobulbar tracts.
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Listeria monocytogenes Infection of the Brain
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A Direct Viable Count Method Suitable for Use With Listeria monocytogenes.

Joseph F Frank1, Mustafa A Gassem1, Revis A N Gillett1

  • 1Department of Food Science and Technology, University of Georgia, Athens, Georgia 30602.

Journal of Food Protection
|May 16, 2019
PubMed
Summary

A new direct microscopic method accurately detects viable Listeria monocytogenes by observing cell elongation after incubation. This viable count method is effective for pure cultures and detecting starved Listeria monocytogenes cells.

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Area of Science:

  • Microbiology
  • Food Safety
  • Cell Biology

Background:

  • Accurate enumeration of viable Listeria monocytogenes is crucial for food safety.
  • Traditional methods may underestimate viable cell counts, especially under stress conditions.

Purpose of the Study:

  • To develop and validate a direct microscopic method for determining viable Listeria monocytogenes.
  • To assess the survival of Listeria monocytogenes under starvation conditions.

Main Methods:

  • A novel direct viable count method utilizing epifluorescent microscopy and acridine orange staining.
  • Incubation of samples in tryptic soy broth with yeast extract and novobiocin.
  • Monitoring cell elongation as an indicator of viability.

Main Results:

  • Viable Listeria monocytogenes cells elongated significantly (0.8–1.5 μm to 2.4–4.8 μm) without dividing during a 6-hour incubation.
  • Novobiocin addition inhibited cell division, enhancing the viability signal.
  • The direct viable count method detected higher numbers of starved Listeria monocytogenes cells compared to conventional plate counts.

Conclusions:

  • The developed direct microscopic method provides a reliable way to enumerate viable Listeria monocytogenes.
  • This method is particularly useful for studying Listeria monocytogenes survival under starvation or stress.
  • The technique offers improved sensitivity for detecting viable but non-culturable Listeria monocytogenes.