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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

what is lactose
adekanbi Reply
codomint marker such as RELP are useful for
Nandan Reply
how this process start
Radhika Reply
deffination of staining
Bhavanimangali Reply
It's using dies to differentiate microorganism
shalon
Staining can be defined as a process of using stains or dye to differentiate microorganisms in an environment or habitat.
adeolu
with the aid of a well labeled diagram describe the conducting system
Maridad Reply
what is cellular immunity
namugenyi Reply
Cellular Immunity. -Lymphocytes act against target cell. -Acts directly by killing infected cells.
abdinor
What are NK cells
Peter
Natural killer cells
Rahaba
what are Antigen determinant
mary
cellular immunity is the state where the lymphocytes destroy the infected or targeted cell
cynthia
any examples of oedema
cynthia
introduction of microbial diversity-1
Bhavanimangali Reply
List the type of micro organism arround us and how they can be seen and with what kind of instrument
clinton Reply
how is the arrangements of bacteria in bacilli
Vaidah Reply
Provide some examples of bacterial structures that might be used as antibiotic targets and explain why.
Vaidah
Coccobacilli, Club-Shaped bacilli, Bacilli with rounded ends, Fuilform bacilli, Bacilli with ends square.
Enoch
three main antibiotic targets in bacteria: The cell wall or membranes that surrounds the bacterial cell. The machineries that make the nucleic acids DNA and RNA. The machinery that produce proteins
Rushikesh
The bacterial cell wall. Protein production. and DNA synthesis. Why, this is because most drugs (antibiotics) affects the cell wall of the bacteria, which makes the bacteria weak or susceptible in human body.
Enoch
UV rays affecting the..
Mali Reply
what is microbiology
Baba Reply
Microbiology is the study of microorganisms, which are prokaryotic and eukaryotic cell which includes bacteria, fungi, viruses and pathogenic protozoa.
Enoch
Microbiology is the branch of Life science which deals with scientific study of many Microorganisms.
Rushikesh
what is types of microbiology
Alsheikh
Immunology, Bacteriology, Virology, Mycology, Algology etc
Enoch
Virology, Immunology, Bacteriology, Algology, Mycology, Protoozology etc
Enoch
and what is mycology
Alsheikh
Immunology, Serology, Virology, Microbial Genetics, Parasitology, Bacteriology, Mycology, Molecular, Cell Biology, Agricultural, Water,Soil, Food Industrial ,Pharmaceutical, Applied, Environmental, Clinical, Medical,Marine Microbiology, Microbial Systematics, Etc, are & many types of Microbiology.
Rushikesh
study of fungi is called mycology
Munna
Mycology is the branch of Microbiology which deals with scientific study of Fungi.
Rushikesh
Study of microorganisms,which we can't see with our naked eye is called microbiology
Munna
Mycology is the scientific study of Fungi.
Enoch
virology is the study of viruses
Oppah
what is microbiology? microbiology is the study of small microorganisms that we can not with our naked eyes.
Leticia
what is taxonomical classification of microbiology
Bami
The algae, protozoa, slime moulds, fungi, bacteria, archaea and viruses ,are taxonomic classification of Microorganisms
Rushikesh
We have Bacteria, Archaea, Protozoa, Algae, Fungi, Viruses.
Enoch
microbiology is the study of microbes too small to be seen by naked eyes
Maridad
microbiology is a branch of biology which deals with study of smallest living microrganisms such as bacteria protozoa fungi and viruses
Chaitra
microbiology is the study of microorganisms which can't be seen by our naked eyes
Nakaweesi
Micro - Minute Bio - Life Logus - Study
Roshan
what is the meaning of antimicrobial susceptibility testing
Devshree Reply
seven gram positive bacteria
Okocha Reply
seven examples of gram negative bacteria
Okocha
seven examples of gram negative bacteria
Okocha
Physical conditions that would enable selective Isolation of staphylococcus epidermis
shongile Reply
Nutritional requirements that would enable selective Isolation of staphylococcus epidermis
shongile
Nutritional requirements that would enable selective Isolation of staphylococcus epidermis
shongile
what is constant flux but
Jane Reply

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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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