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L. monocytogenes is generally introduced into food items by contamination with soil or animal manure used as fertilizer. Foods commonly associated with listeriosis include fresh fruits and vegetables, frozen vegetables, processed meats, soft cheeses, and raw milk. US Centers for Disease Control and Prevention, “ Listeria Outbreaks,” 2016. Accessed June 29, 2016. https://www.cdc.gov/listeria/outbreaks/index.html. Unlike most other foodborne pathogens, Listeria is able to grow at temperatures between 0 °C and 50 °C, and can therefore continue to grow, even in refrigerated foods.

Ingestion of contaminated food leads initially to infection of the gastrointestinal tract. However, L. monocytogenes produces several unique virulence factors that allow it to cross the intestinal barrier and spread to other body systems. Surface proteins called internalins (InlA and InlB) help L. monocytogenes invade nonphagocytic cells and tissues, penetrating the intestinal wall and becoming disseminating through the circulatory and lymphatic systems. Internalins also enable L. monocytogenes to breach other important barriers, including the blood-brain barrier and the placenta. Within tissues, L. monocytogenes uses other proteins called listeriolysin O and ActA to facilitate intercellular movement, allowing the infection to spread from cell to cell ( [link] ).

L. monocytogenes is usually identified by cultivation of samples from a normally sterile site (e.g., blood or CSF ). Recovery of viable organisms can be enhanced using cold enrichment by incubating samples in a broth at 4 °C for a week or more. Distinguishing types and subtypes of L. monocytogenes —an important step for diagnosis and epidemiology—is typically done using pulsed-field gel electrophoresis. Identification can also be achieved using chemiluminescence DNA probe assays and MALDI-TOF.

Treatment for listeriosis involves antibiotic therapy, most commonly with ampicillin and gentamicin . There is no vaccine available.

a) Micrograph of a rod shaped cell. b) Diagram of infection. Step 1: Listeria monocytogenes enters cell via phagocytosis. Diagram shows rod shaped cell (Listeria monocytogens) in a phagosome. 2: Pathogen escapes when phagosome is lysed. 3: Pathogen reproduces. 4: Pahtogen produces actin filaments from host cytoskeleton components. The diagram shows tails on the cell labeled actin filaments. 5: Actin pushes the pathogen from one cell to another through a protrusion of the host membrane. 6: The protrusion is engulfed by another cell. This forms a vesicle with the pathogen inside. 7: cycle repeats.
(a) An electron micrograph of Listeria monocytogenes infecting a host cell. (b) Listeria is able to use host cell components to cause infection. For example, phagocytosis allows it to enter host cells, and the host’s cytoskeleton provides the materials to help the pathogen move to other cells. (credit a: modification of work by the Centers for Disease Control and Prevention; credit b: modification of work by Keith Ireton)
  • How does Listeria enter the nervous system?

Hansen’s disease (leprosy)

Hansen’s disease (also known as leprosy ) is caused by a long, thin, filamentous rod-shaped bacterium Mycobacterium leprae , an obligate intracellular pathogen. M. leprae is classified as gram-positive bacteria, but it is best visualized microscopically with an acid-fast stain and is generally referred to as an acid-fast bacterium . Hansen’s disease affects the PNS, leading to permanent damage and loss of appendages or other body parts.

Hansen’s disease is communicable but not highly contagious; approximately 95% of the human population cannot be easily infected because they have a natural immunity to M. leprae . Person-to-person transmission occurs by inhalation into nasal mucosa or prolonged and repeated contact with infected skin. Armadillos, one of only five mammals susceptible to Hansen’s disease, have also been implicated in transmission of some cases. Sharma, Rahul, Pushpendra Singh, W. J. Loughry, J. Mitchell Lockhart, W. Barry Inman, Malcolm S. Duthie, Maria T. Pena et al., “Zoonotic Leprosy in the Southeastern United States,” Emerging Infectious Diseases 21, no. 12 (2015): 2127-34.

Questions & Answers

Explain about enzyme transportation
Shahla Reply
Enzyme transportation
it looks reallllyyyyy coooooooollll. i love enzymes theyre so cooll and i also like protein transportation so i think it would be really cool so an enzyme transport something so ill do some research and come back to ya in that
they be ridin' dirty
what is the infectious disease process
Patience Reply
what are differences between endotoxins and exotoxins
sabote Reply
endo toxins work in the nuceus. i think
tell me if im right tho
Exotoxins are toxic substances secreted by bacteria and released outside the cell. Both gram positive and gram negative bacteria can produce and secrete exotoxins. Whereas Endotoxins are bacterial toxins consisting of lipids that are located within a cell. Only lysed gram negatives.
Remebr the Lipid A portion of LPS is what's toxic.
oh yeah. thanks
Your welcome :)
How did you learn this?
For me personally the best book is 'microbiology made ridiculously simple'
I got my basics from there and slowly added information from other sources.
thats cool! yeah i like microbiology too! especially the molecular proteins theyre sooooooooooo cool!
what are the prokaryotic
Lungu Reply
prokaraytotic is a unicellular organizm that lacks membrane bound nucleus
and whats eukaryotic
eukaryotic cell are cell which contain anuclues and organells
eukaryotes are the cells that have organells which are protected by membranes
eukaryotic is are multicellular organisms which are open nucleus.
Explain on the Francisco reddi did to prove the theory of spontaneous generation
Diana Reply
what is parasite
Abdirizack Reply
parasite are organisms feeds on a host for food and survival.e.g round worm for animal, Dodder for plant parasites.
parasite are organisms that feeds on a host for food and survival.e.g round worm for animal and mistletoe for plant parasites.
parasite are organisms that feed on their host
designing of aseptic area
Aashish Reply
I don't know
what is rickettsia
what is microbiology
Is the science that works with microorganisms.
richettsa is small microorganisms that cause disease in human like typhus; they are like viruses that can grow only inside living cells, they're transmitted by mites, ticks or lices.
what is plasmid?
plasmid is extra chromosomal body present in bacteria...which have additional genetic functions example... antibiotic resistance genes....etc etc
state the theory of spontaneous generation of micro oranisms and germ theory of disease
what are the advantages of high note numerical aperture
Genius Reply
list if non flagellated pritozoa
Mepung Reply
Can someone that's understanding of the Kreb Cycle please explain & breakdown it down to me in the simplest way without giving me the dictionary version or Google version. Basically in there own words of knowledge....!
please can someone help explain positive and negative feedback in simple term
negative feedback is the arresting of reaction or reverse of the reaction according to the response and postive feed back is the direct response without reversing or arresting a reaction.
pls can someone explained Kinney stone in memorising in shot time
what tyoebif microorganism will be killed by antibiotic trwatmeant
Mary Reply
I don't really don't understand aerobic respiration anaerobic respiration and fermentation. Can someone explain & breakdown this in the simplest way please.
Anaerobic Respiration in which foodstuffs are partially oxidized, with the release of chemical energy, in a process not involving atmospheric oxygen, such as alcoholic fermentation, in which one of the end products is ethanol.
aerobic respiration A type of respiration in which foodstuffs are completely oxidized to carbon dioxide and water, with the release of chemical energy, in a process requiring atmospheric oxygen.
please can someone explain what pseudomonas species and biofilm is?
Fermentation is the growth of cells or microorganisms in bioreactors (fermenters) to synthesize special products. Fermentation in biochemistry refers to the biodegradation of carbon compounds by cells or organisms under anaerobic (lack of oxygen) conditions.
Please under which conditions does pathogens become established in the human tissues and can cause diseases
please the life cycle of plasmodium parasite
who is John Needham
Mary Reply
John Needham is one of the researcher in microbiology. He also experimented when scientists did not believe animals could arise spontaneously ,but did believe microbes could.
okay is he late
by the way what are the list of courses offered by a newly admitted student for microbiology
Needham's experiments with beef gravy and infusions of plants material reinforced this idea.
what drugs are given to a person with Otis nerve problem(ear problem)
Gum Reply
good morning to you all.
Muhammad Reply
Dr.A.K.S.P.G. college Akbarpur Ambedkar Nagar
Shailesh Vishwakarma BSc 1st year

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