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[link] lists selected foodborne pathogens and their ID 50 values in humans (as determined from epidemiologic data and studies on human volunteers). Keep in mind that these are median values. The actual infective dose for an individual can vary widely, depending on factors such as route of entry; the age, health, and immune status of the host; and environmental and pathogen-specific factors such as susceptibility to the acidic pH of the stomach. It is also important to note that a pathogen’s infective dose does not necessarily correlate with disease severity. For example, just a single cell of Salmonella enterica serotype Typhimurium can result in an active infection. The resultant disease, Salmonella gastroenteritis or salmonellosis , can cause nausea, vomiting, and diarrhea, but has a mortality rate of less than 1% in healthy adults. In contrast, S. enterica serotype Typhi has a much higher ID 50 , typically requiring as many as 1,000 cells to produce infection. However, this serotype causes typhoid fever , a much more systemic and severe disease that has a mortality rate as high as 10% in untreated individuals.

ID 50 for Selected Foodborne Diseases Food and Drug Administration. “Bad Bug Book, Foodborne Pathogenic Microorganisms and Natural Toxins.” 2nd ed. Silver Spring, MD: US Food and Drug Administration; 2012.
Pathogen ID 50
Viruses
Hepatitis A virus 10–100
Norovirus 1–10
Rotavirus 10–100
Bacteria
Escherichia coli , enterohemorrhagic (EHEC, serotype O157) 10–100
E. coli , enteroinvasive (EIEC) 200–5,000
E. coli , enteropathogenic (EPEC) 10,000,000–10,000,000,000
E. coli , enterotoxigenic (ETEC) 10,000,000–10,000,000,000
Salmonella enterica serovar Typhi <1,000
S. enterica serovar Typhimurium ≥1
Shigella dysenteriae 10–200
Vibrio cholerae (serotypes O139, O1) 1,000,000
V. parahemolyticus 100,000,000
Protozoa
Giardia lamblia 1
Cryptosporidium parvum 10–100
  • What is the difference between a pathogen’s infective dose and lethal dose?
  • Which is more closely related to the severity of a disease?

Primary pathogens versus opportunistic pathogens

Pathogens can be classified as either primary pathogens or opportunistic pathogens. A primary pathogen can cause disease in a host regardless of the host’s resident microbiota or immune system. An opportunistic pathogen , by contrast, can only cause disease in situations that compromise the host’s defenses, such as the body’s protective barriers, immune system, or normal microbiota. Individuals susceptible to opportunistic infections include the very young, the elderly, women who are pregnant, patients undergoing chemotherapy, people with immunodeficiencies (such as acquired immunodeficiency syndrome [AIDS]), patients who are recovering from surgery, and those who have had a breach of protective barriers (such as a severe wound or burn).

An example of a primary pathogen is enterohemorrhagic E. coli ( EHEC ), which produces a virulence factor known as Shiga toxin . This toxin inhibits protein synthesis, leading to severe and bloody diarrhea, inflammation, and renal failure, even in patients with healthy immune systems. Staphylococcus epidermidis , on the other hand, is an opportunistic pathogen that is among the most frequent causes of nosocomial disease. M. Otto. “ Staphylococcus epidermidis --The ‘Accidental’ Pathogen.” Nature Reviews Microbiology 7 no. 8 (2009):555–567. S. epidermidis is a member of the normal microbiota of the skin, where it is generally avirulent. However, in hospitals, it can also grow in biofilms that form on catheters, implants, or other devices that are inserted into the body during surgical procedures. Once inside the body, S. epidermidis can cause serious infections such as endocarditis, and it produces virulence factors that promote the persistence of such infections.

Questions & Answers

Differentiation between electron, proton and neutron
Zainab Reply
what are the roles of microorganisms in human being
Buhari Reply
some causes disease, others are not disease causing
Clark
they're necessary in our digestive system+the skin,everywhere actually the number of them in the human body alone is higher(by millions)than the number of humans cells,they're indispensable in the food industry,others are fundamental to make medicines and more,what exactly are you asking about ?
BENNINI
What are the natural occurring elements found in organisms on earth?
Otu Reply
some of the naturally occurring elements found in organisms are carbon, nitrogen, hydrogen, oxygen
Yashi
thanks
Mariam
some of them are carbon, oxygen, nitrogen, hydrogen, phosphorus and sulfur
Jamal
what is Zika virus?
Somali Reply
Zika virus is a mosquito-borne flavivirus that was first identified in Uganda in 1947 in monkeys. 
Cumar
intracellular vesicles are found in
Akshay Reply
how do i report widal slide results
Isaac Reply
how food can be used as a substrate for the growth of microorganisms
Ashi Reply
what is the importance of understanding chemistry in the field of microbiology and food technology?
Charmaine Reply
What is different between eukaryotes and prokcaryotic
Abia Reply
main difference is that eukaryotic cells possess membrane bound organelles
Iqra
prokaryotes are primitive organisms that doesn't contain membrane bound nucleus or any orgenelle while in eukaryotes membrane bound orgenelles and nucleus is present
Yashi
what s anatomy
jane Reply
its mean body structure, function, and systems
gazi
study of internal structure of living things
Falere
anatomy is the study structure of the made human
isir
anotomy is the actual study of body internally and externally Which include how itis made. for what and what is need of this
Iqra
la science anatomie c'est la science qui nous aide à étudier l'homme
Baraka
okay
Baraka
Ancestor are they real
Rapheal Reply
yes of course
David
yes please
Clark
50 50, depending on the accuracy of the clan records.
Vincent
okay
Baraka
Why protist is not a kingdom of Linnaeus 'S taxonomy?
Neha Reply
I dont know
Jeewraj
Linnaeus used Aristotle's criteria for dividing living organisms into kingdoms. Plants are immobile and insensitive, while animals are mobile and sensitive. the creatures he saw through the microscope were mobile, so he attributed them to animals.
Lad
name the different types of media use in lab to detect the micro organisms
Shehzadi Reply
The different types of media used in the lab to detect the microorganisms is known as cell culture..
Tean
solid media or broth is used to grow and detect microorganisms
Pohor
what is microbiology
Baraka
the study of large living organisms
Pratibha
the study of organisms which are micro in range
Vency
what is autoclaving?
Yashi
process for sterilization
Vency
is a machine used on the process of sterilisation
Clark
what is difference between hot air oven and autoclave as they both are used for sterilization ?
Vency
autoclave basically do moist heat sterilization while hot air oven do sterilization by dry heat.....
Yashi
what is the microbe
HUSSAIN
which method out of these two is best?
Yashi
why human have microbe
HUSSAIN
Hi
Sadam
hi to all
Sadam
depends on what to sterilize
Vency
microbes
Md
what is knowledge
HUSSAIN
well idea
Daniel
what are the importance of microbiologe to a nurse
Enny Reply
it enable a nurse to know the weight and height of a patient
Abotu
it helps the nurse in way as to give first aid to patient on which basis doctor will take diagonos
Iqra
disagree with both of you
Akhtar
ok
Abotu
Your Own idea
Abotu
it helps a nurse to be able to counsel a patient /client
Abotu
cell culture
Tean
Types of micro organisms
Jennifer Reply
Who discovered plant and animal cell
Jennifer
Robert Hooke
Martha

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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