Symptoms of staphylococcal enterotoxicosis occur within __________ after eating contaminated food.

• Infectious diseases are caused by microorganisms such as viruses, bacteria, fungi or parasites.
• Microorganisms that cause disease are collectively called pathogens.
• Pathogens cause disease either by disrupting the bodies normal processes and/or stimulating the immune system to produce a defensive response, resulting in high fever, inflammation and other symptoms.
• Infectious diseases can be spread from one person to another, for example through contact with bodily fluids, by aerosols (through coughing and sneezing), or via a vector, for example a mosquito.

Close up of a mosquito feeding on human blood.
Image credit: Shutterstock

• Infectious diseases are one of the leading causes of death worldwide.
• Many diseases become difficult to control if the infectious agents evolve resistance to commonly used drugs:
  • For example, bacteria can accumulate mutations in their DNA or acquire new genes that allow them to survive contact with antibiotic drugs that would normally kill them.
• Scientists are currently searching for new approaches to treat infectious diseases, focusing on exactly how the pathogens change and drug resistance evolves.

What causes an infectious disease?

Viruses

• Viruses are tiny infectious agents that replicate only in the living cells of other organisms.
• Viruses have a very simple structure consisting of genetic material in the form of DNA or RNA within a protein capsule.
• They can infect all types of life forms, from animals to plants and bacteria to amoebae.
• Viruses can be spread in many ways including:
  • From plant to plant by insects that feed on plant sap. For example, Potato virus Y which is spread by aphids.
  • From animal to animal by blood-sucking insects. For example, Dengue virus which is spread by mosquitos.
  • Spread by aerosols (through coughing and sneezing). For example, influenza virus or the novel coronavirus SARS-CoV-2.
  • Spread by not washing hands after going to the toilet. For example, norovirus or rotavirus.
  • Spread by sexual contact. For example, HIV and Human Papillomavirus (HPV).
  • Spread by exposure to infected blood. For example, Hepatitis B.
• Viruses can often be prevented through vaccines.

The basic structure of a virus
Image credit: Ben Taylor, via Wikipedia commons

Bacteria

• Bacteria are single-celled microorganisms.
• They come in many shapes including ball-, rod- and spiral-shaped.
• Most bacteria are not harmful and some are actually beneficial. Less than one per cent of bacteria will actually make you ill.
• Infectious bacteria can grow, divide and spread in the body, leading to infectious disease.
• Some infectious bacteria give off toxins which can make some diseases more severe.
• Bacteria are spread in many ways including:
  • Spread by aerosols (through coughing and sneezing). For example, Streptococcus.
  • Spread by surface and skin contact. For example, Staphylococcus aureus, including MRSA.
  • Spread through body fluids, such as blood and saliva. For example, meningococcal disease (meningitis).
• Antibiotics are usually given to treat severe bacterial infections.
• Antibiotic resistance in bacteria is a significant problem.

Streptococcus bacteria.
Image credit: Shutterstock

Fungi

• Fungi are microorganisms characterised by cell walls made from a substance called chitin.
• Most fungi are harmless to humans and some are edible.
• Other fungi can be infectious and may lead to life-threatening diseases.
• Fungi reproduce by releasing spores that can be picked up by direct contact or even inhaled.
• Fungal infections often affect the lungs, skin or nails. Some infections may also penetrate the body to affect organs and cause whole-body infections.
• Examples of fungal infections include:
  • Athlete’s foot: itching, scaling or cracking of the skin
  • Ringworm: reddish, itchy, scaly rash usually on the skin and scalp
  • Thrush: caused by the fungus Candida albicans which can infect the mouth, vagina, stomach and urinary tract.

Parasites

• Parasites are organisms that live in or on another organism and benefit by getting nutrients at the expense of their host.
• Parasites can be found in many different body sites, for example in the blood, liver, digestive system, brain and even the eyes.
• There are several groups of parasites that infect humans:
  • Roundworms: these are nematode worms that can get into humans by ingestion, directly penetrating the skin or through insect bites.
    • Examples: whipworm (ingested), hookworms (directly penetrate the skin), Wuchereria bancrofti (transmitted by mosquitos)
  • Protozoa: these are single-celled parasites. Many are delivered by biting insects or are ingested with contaminated water or food. They invade or eat host cells, or swim around the bloodstream and quickly reproduce by copying themselves.
    • Examples: Giardia (ingested), Plasmodium falciparum (causes malaria and is transmitted by mosquitos), Trichomonas (sexually transmitted)
  • Tapeworms: these are flatworms whose heads hook on to the intestinal wall of their host. Their larvae migrate to other parts of the body. They can live in the host for decades.
  • Flukes: blood flukes are flatworms that are caught through contact with contaminated water. Blood fluke larvae are released from infected snails into freshwater. Liver flukes can be found in raw or undercooked fish or water plants and can live in the body of the host for decades.
    • Example: Schistosomes (blood flukes).

Male and female schistosomes. The female can be seen lying within a groove on th e surface of the male (stained pink).
Image credit: Shutterstock

Can you spare 5-8 minutes to tell us what you think of this website? Open survey

1

Diseases of the ___________ are the second most common illnesses in the United States.

2

Diseases of the digestive system usually result from ingesting _____________________________

microorganisms or their toxins in food
and water

3

The fecal–oral cycle of transmission can be broken by the: ____________________ ____________________

____________________.

proper disposal of sewage, the disinfection of drinking water,

and proper food preparation and storage

4

True or False
Small numbers of bacteria colonize the mouth

False:
Large numbers of bacteria colonize the mouth

5

True or False:
The stomach and small intestine have a lot of resident microorganisms

False
The stomach and small intestine have few resident microorganisms

6

Bacteria in the large intestine assist ______________________________________

in degrading food and synthesizing vitamins

7

Up to _____ of fecal mass is microbial cells

8

_______________, found in the mouth, uses sucrose to form dextran from glucose and lactic acid
from fructose

9

Bacteria adhere to teeth by the sticky _________, forming dental plaque

10

Caries of the cementum and gingivitis are caused by - -

-

streptococci, actinomycetes,

and anaerobic gram-negative bacteria

11

Acute necrotizing ulcerative gingivitis is often caused by -----------------

12

Staphylococcal food poisoning is caused by the ingestion of an _________ produced in improperly
stored foods.

13

S. aureus is inoculated into foods during __________. The bacteria grow and produce enterotoxin in food stored at room temperature

14

True or False
Boiling for 30 minutes is not sufficient to denature the exotoxin

15

Foods with high osmotic pressure (like salt) and those not cooked immediately before consumption are most
often the source of _____________________________

staphylococcal enterotoxicosis

16

Shigellosis (Bavillary Dysentery) is caused by any of four species of ______________

17

Symptoms include blood and mucus in stools, abdominal cramps, and fever.

18

Infections by __________result in ulceration of the intestinal mucosa

19

Salmonellosis, or Salmonella gastroenteritis, is caused by many ____________________________

Salmonella enterica serovars.

20

Symptoms include nausea, abdominal pain, and diarrhea and begin 12 to 36 hours after eating large numbers of Salmonella

21

True or False
Salmonellosis can cause Septic shock to occur in infants and in the elderly

22

True or False
Cooking food will usually kill Salmonella

23

_________ causes typhoid fever; the bacteria are transmitted by contact with human feces

24

S. typhi is harbored in the ___________ of carriers

25

Typhoid fever is treated with ___________ and ________

quinolones and cephalosporins

26

Vibrio cholerae O:1 and O:139 produce an exotoxin that ________________________________________

alters the membrane permeability of the intestinal
mucosa

27

Vibrio gastroenteritis can be caused by ______________________ and _______________________

V. parahaemolyticus and V. vulnificus

28

Noncholera Vibrios diseases are contracted by __________________________________

eating contaminated crustaceans or contaminated mollusks

29

Traveler’s diarrhea may be caused by enterotoxigenic or enteroinvasive strains of __________.

30

___________ is the second most common cause of diarrhea in the United States

31

Campylobacter is transmitted in

unpasteurized cow’s milk or fruit juices and poorly cooked

32

___________________ produces ammonia, which neutralizes stomach acid; the bacteria colonize the stomach
mucosa and cause peptic ulcer disease.

33

with Yersinia Gastroenteritis ____________ and _______________ are transmitted in meat and milk.

Y. enterocolitica and Y. pseudotuberculosis

34

True or False:
Yersinia can grow at refrigeration temperatures

35

Growth of__________ following antibiotic therapy can result in mild diarrhea or severe colitis.

36

True or false C. diff condition is usually associated with hospitalized patients and nursing home residents.

37

Mumps virus enters and exits the body through the ____________________

38

This virus causes inflammation of the parotid glands, fever, and
pain during swallowing. About 4 to 7 days later, orchitis may occur in males.

39

With Mumps After onset of the symptoms, the virus is found in the - -

-

40

Inflammation of the liver is called _________

41

Viral causes of hepatitis include hepatitis viruses, _____________ (___), and ____________ (___).

Epstein-Barr virus (EBV), and cytomegalovirus (CMV)

42

_____________ (____) causes hepatitis A

43

HAV is ingested in contaminated food or water

ingested in contaminated food or water,

cells of the intestinal mucosa, and
spreads to the liver, kidneys, and spleen in the blood

45

The virus is eliminated with ________

46

_____________ causes hepatitis B, which is frequently serious

blood transfusions, contaminated syringes, saliva, sweat, breast milk, and
semen

48

True or False The average incubation period is 3 months; recovery is usually complete, but some patients develop

a chronic infection or become carriers.

49

Hepatitis C virus (HCV) is transmitted via

50

Viral gastroenteritis is most often caused by a ___________ or _________________

51

Ergot poisoning, or ergotism, is caused by the mycotoxin produced by _______________

52

____________ are the crop most often contaminated with the Claviceps mycotoxin

53

Giardia lamblia grows in the intestines of humans and wild animals and is transmitted in

54

Cryptosporidiosis causative agent is

55

Crytosporidium hominis causes diarrhea

56

Crytosporidium hominis is transmitted in

57

Cyclospora Diarrheal Infection is caused by

58

Cyclospora Diarrheal Infection is transmited by

59

Amoebic dysentery is caused by ___________________ growing in the large intestine

60

Tapeworms are contracted by the consumption of _____________________ containing
encysted larvae (cysticerci

undercooked beef, pork, or fish

61

The ________ attaches to the intestinal mucosa of humans (the definitive host) and matures into an adult
tapeworm

62

_________________ in humans occurs when the pork tapeworm larvae encyst in humans

63

Humans are the __________ host for pinworms

64

is acquired by ingesting Enterobius eggs

65

how do you contract hookworms

Hookworm larvae bore through skin and migrate to the intestine to mature into adults

66

hookworm larvae hatch from eggs _________

67

68

Ascaris lumbricoides adults live in _________________

69

Ascariasis is acquired by _____________

70

Trichinellosis is contracted by

contracted by ingesting undercooked meat containing larvae

71

Adult females mature in the 1._______ and lay eggs; the new larvae migrate to invade 2._______

72

Trichinellosis Symptoms include

fever, swelling around the eyes, and gastrointestinal upset