Topic 18

Question 1

What is a pathogen?

Answer 1

Microorganism capable of causing disease

Question 2

What is virulence

Answer 2

The degree to which a pathogen causes illness (how sick a person gets)

Question 3

What are two types of pathogens?

Answer 3

1) Parasites; 2) opportunistic pathogen

Question 4

What is a parasite?

Answer 4

Organism that derives nutrients from host tissues; may or may not cause disease symptoms

Question 5

What is an opportunistic pathogen?

Answer 5

Not normally pathogenic, but can cause disease in a host with a compromised immune system

Question 6

What does it mean to be non-pathogenic?

Answer 6

A microorganism unable to cause disease (NOTE: this can be relative, for example, Ecoli is typically non-pathogenic, but can lead to disease in your ears; pathogenicity and virulence are often strain dependent)

Question 7

What were Ignaz Semmelweis’ contributions to microbiology?

Answer 7

1) First to examine germ theory of disease; 2) instituted hand washing to significantly reduce mortality rates

Question 8

What were John Snow’s contributions to microbiology?

Answer 8

1) Contributed to germ theory of disease; 2) helped to explain cholera outbreak in London in 1854 as due to contaminated water

Question 9

What were Robert Koch’s contributions to microbiology?

Answer 9

1) Studied anthrax in cattle; 2) firmly established the Germ Theory of Disease (that microbes cause disease); 3) developed important postulates

Question 10

What are Koch’s Postulates?

Answer 10

1) The microbe has to be present in every case of the disease; 2) the microbe must be isolated and grown in culture; 3) when the cultured microbe is inoculated into another animal, it must cause the same disease; 4) the same microorganism must be re-isolated from the inoculated animal

Question 11

What were Paul Ehrlich’s contributions to microbiology?

Answer 11

1) Considered the “Father of Chemotherapy”; 2) worked to develop stains that would target specific bacteria, but not stain the healthy human cells; 3) result was that compounds could be developed to selectively target a disease causing organism and a toxin could be delivered along with the agent of selectivity

Question 12

What were Ilya Ilyich Mechnikov’s contributions to microbiology?

Answer 12

1) Shared the 1908 Nobel Prize with Paul Ehrlich; 2) first to propose that microbes could be beneficial

Question 13

What are the characteristics of normal flora of humans?

Answer 13

1) Normal healthy individuals have microorganisms living in and on their tissues; 2) most are commensal and even beneficial, while some can be opportunistic; 3) can reside on/in skin, mouth, respiratory tract, stomach, intestines, urogential tract

Question 14

What things must a microorganism be able to do in order to be a successful pathogen?

Answer 14

1) Survive passage from one host to another or from a reservoir to the host; 2) attach to or penetrate the host’s tissues; 3) withstand for a period of time the host’s defense mechanisms; 4) induce damage to or malfunction of the host’s tissues

Question 15

What are potential vehicles of transmission?

Answer 15

1) Repiratory and oral secretions; 2) sloughed off skin cells; 3) insect bites or blood removal; 4) fecal waste; 5) urogenital tract secretions; 6) sexual contact; 7) lesion materials

Question 16

What are three virulence mechanisms that can enable microorganisms to produce disease?

Answer 16

1) Attachment; 2) circumvent of defense mechanism of host; 3) cause tissue damage

Question 17

What are five potential causes of tissue damage?

Answer 17

1) Some bacteria secrete enzymes that contribute to disease by destroying tissue; 2) collagenase and lecithinase are enzymes produced by bacteria that can cause gangrene; 3) hemolysins are enzymes that destroy red blood cells; 4) lipases and nucleases are bacterial enzymes that break down fats and nucleuic acids; 5) some microbes produce toxins

Question 18

What are two types of toxins that can cause disease?

Answer 18

1) Exotoxins; 2) endotoxins

Question 19

What are the characteristics of exotoxins?

Answer 19

1) Extremely powerful poisons; 2) usually proteins that are secreted from the bacterial cell into the surrounding medium

Question 20

What are the characteristics of endotoxins?

Answer 20

1) Less potent; 2) part of the gram negative cell wall; 3) only small amounts may escape into the surrounding fluids from living bacteria; 4) greater amounts of endotoxins are released when bacteria die and their cell walls disintegrate; 5) large amounts are needed to induce disease symptoms; 6) composed of polysaccharides and phospholipids