Pathogens- Bacteria

Question 1

What are cocci?

Answer 1

Round cells

Question 2

What are bacilli?

Answer 2

Rod-shaped cells

Question 3

What are the different formations of bacterial cocci?

Answer 3

Monococcus- single cells
Diplococcus - paired cells
Staphylococcus- grouped cells
Streptococcus- chained cells

Question 4

What are the different formations of bacterial bacilli?

Answer 4

Single rod- bacillus
As groups or clusters
Chains

Question 5

What are fimbrilae/pilli?

Answer 5

They are thin protein tubule projections from the cytoplasmic membrane of many bacteria
-found in almost all gram-negative bacteria but not many found in gram-positive

Question 6

What is an endospore?

Answer 6

An endospore is a resistant asxual spore that develops inside some bacterial cells

Question 7

What are the 2 types of bacterial cell wall?

Answer 7

Gram-positive

Gram-negative

Question 8

What are the properties of a gram-negative cell wall ?

Answer 8

• Has 2 membranes, 1 inner and 1 outer
• Smaller PG layer (peptidoglycan)
• Has a peroplasmic space between PG layer and outer membrane

Question 9

What are the properties of a gram-postive cell wall?

Answer 9

• Only has an inner membrane

- Has a much thicker PG (peptidoglycan) layer than gram negative bacteria

Question 10

How are some bacterial spores resistant?

Answer 10

• Has a core of DNA that is resistant to heat and radiation
• Has a coat that is resistant to chemical and enzymes such as lysozyme
• Has an exosporium that provides adherence and biocide protection

Question 11

What is the sequence of treatment of infectious diseases?

Answer 11

Observation of patient-symptoms
Sampling
Lab observation and culture
Identifcation tests
Treatment- antibiotic therapy
Observation of population- epidemiology
Prevention of transmission

Question 12

What are Koch’s postulates?

Answer 12

Four criteria designed to prove a causative relationship between a microbe and a disease

1. The microorganism must be found in diseased but not healthy individuals
2. The microorganism must be cultured from the diseased individual
3. Inoculation of a healthy individual with the cultered microorganism, it must produce the same disease
4. The microorganism must be re-isolated from the inoculated and match the orginal microorganism

Question 13

What are the negatives to Koch’s postulates?

Answer 13

Less evident to prove conditions that are chronic, have multiple causes or when the pathogen cannot be grown in vitro

Question 14

What is the iceberg concept of infection?

Answer 14

The iceberg concept decribes a situation in which a large percentage of the problem is subclinical, unreported or otherwise hidden from view. Thus, only the ‘tip of the iceberg’ is apparent to the epidemiologist

Question 15

What is normal flora?

Answer 15

Normal flora are those organisms living in benign symbiosis with the host

• they outcompete pathogens
• some may be pathogenic but are unable to enter the disease process

Question 16

What are the hazards with normal flora?

Answer 16

• If conditions change microbes can grow more extensively and cause infections
• a pathogen may blend in with normal flora
• Normal flora is essential and treatment may target them

Question 17

What factors influence the success of transmission in the disease process?

Answer 17

Number of microbes- more the better
Size, density, surface features, hydrophobicity
Spore formation, adhesion to surfaces
Distribution in the host

Question 18

What are the critical stages in disease success in the disease process?

Answer 18

Adhesion-depends on microbe and host features
Invasion- depends on breaks in the surafce layer or active procedures from microbe
Motility of the microbe- chemotaxis
Attachment to site- using pilli
Penetration of epithelium- using enzymes like proteases

Question 19

What are the consequences of disease success in the disease process?

Answer 19

• Growth in tissues require cells to resist host responses
• May have means to neutralise host cells
• Growth takes away nutrients from host cells and tissues
• Tissue damage results in host cell death- due to toxins and ezymes

Question 20

What does pathogenicity mean?

Answer 20

The ability of a pathogen to produce an infectious disease in an organism

Question 21

What does virulence mean?

Answer 21

The relative degree of damage done by a pathogen, or the degree of pathogenicity of a pathogen

Question 22

What is a pathogenicity/virulence factor?

Answer 22

A microbial product that contributes to virulence or pathogenicity

Question 23

How does a bacterial capsule help in penetration of host defenses?

Answer 23

Help in attachment of the microbe

Prevents phagocytosis of the microbe- may be resistant to lysozymes so can be broken down

Question 24

What are hemolysins and how to bacteria utilize them?

Answer 24

Hemolysins are enzymes that cause the complete or incomplete lysis of red blood cells
-bacterial can then utilize the nutrients (e.g iron) from the red blood cells to grow and replicate

Question 25

What is coagulase and how do bacteria utilize it?

Answer 25

Coagulase is an enzyme which causes the clotting of blood or plasma - this protects the bacteria from white blood cells and other host defenses that are either in the blood or move via the bloodstream

Question 26

What is collagenase and how do bacteria utilize it?

Answer 26

Collagenase is an enzyme which breaks down collagen | -this increases the mobility of bacteria and allows them to spread through muscle tissue

Question 27

What are leukocidins and how do bacteria utilize them?

Answer 27

Leukocidins is a type of cytotoxin created by some types of bacteria -Targets phagocytes, NK cells, dendritic cells and T cells which weakens both the innate and adaptive immunity for the microbe to survive

Question 28

What is a toxin?

Answer 28

A poisonous substance produced by a bacteria | - most work by damaging the eukaryotic cell membrane in some way

Question 29

What are the 2 main classes of toxins?

Answer 29

Exotoxins | Endotoxins- also known as LPS (lipopolysaccharides)

Question 30

What is difference between exotoxins and endotoxins?

Answer 30

- Exotoxins are secreted outside of the bacterial cell by mostly gram-positive bacteria - Where as endotoxins are a part of the outer cell wall of gram negative bacteria. They are freed when the bacteria dies and the cell wall breaks.

Question 31

What are the 3 types of exotoxins?

Answer 31

Enterotoxin Neurotoxin Cytotoxin

Question 32

What are enterotoxins?

Answer 32

A toxin that is produced in or affects the intestines

Question 33

What are neurotoxins?

Answer 33

Toxins that are destructive to nervous tissue

Question 34

What are cytotoxins?

Answer 34

A cytotoxin is any substance that has a toxic effect on an important cellular function

Question 35

What is bacillus cereus?

Answer 35

A gram positive rod shaped bacteri commonly found in soil or food

Question 36

What toxins do bacillus cereus produce?

Answer 36

- the 3 component enterotoxin haemolysin BL (HBL) - the 3 component non-haemolytic enterotoxin (NHE) - the 1 component enterotoxin cytotoxin K - Cereulide cytotoxin

Question 37

What are the symptoms of bacillus cereus?

Answer 37

Abdominal pain, watery diarrhoea for 12-24 hours | Nause, vomiting and malaise (discomfort) for 6-24 hours

Question 38

What happens to a patient if all 4 toxins are produced by the bacillus cereus?

Answer 38

If all 4 toxins are present, the patient will express all the symptoms

Question 39

What is a beta-lactam antibiotic?

Answer 39

A type of antibiotics that contain a beta-lactam ring in their molecular structure e.g amoxicillin

Question 40

How do beta-lactams antibiotics kill bacteria?

Answer 40

They inhibit the synthesis of the peptidoglycan layer of bacterial cell walls, which is inportant for cell wall structural integrity (especially in gram-positive bacteria)