Microbiology + Pathogens

Question 1

What type of organisms are bacteria?

Answer 1

Bacteria are prokaryotic organisms.

Question 2

Can bacteria remain within body cavities or cells without being pathogenic?

Answer 2

Yes, bacteria can remain within body cavities or cells without being pathogenic.

Question 3

What is tuberculosis and how is it transmitted?

Answer 3

Tuberculosis is a disease that causes coughing and blood in the sputum. It is caused by the bacterium Mycobacterium tuberculosis.

Question 4

How do bacteria divide?

Answer 4

Bacteria divide by binary fission. The DNA is replicated, and a regulated number of plasmids are inherited. The cytoplasm splits into two, and daughter cells contain a variable number of plasmids. The cell division mechanism is regulated so that is both daughter cells do not contain identical DNA they die.

Question 5

What are endotoxins in bacteria?

Answer 5

Endotoxins are lipopolysaccharides found in the cell wall of gram-negative bacteria. The lipid part acts as a toxin, and the polysaccharide stimulates the immune response, causing symptoms such as fever, vomiting, and diarrhea, as seen in Salmonella (inflammation in intestine causing no water absorption and spasms of peristalsis. If treated with antibiotics that treat lysis it could cause the further release of toxins.

Question 6

What are exotoxins in bacteria?

Answer 6

Exotoxins are soluble proteins produced by both types of bacteria. They have more widespread effects as they act at distant sites. They can cause the breakdown of cell membranes, internal bleeding and act as competitive inhibitors to neurotransmitters

Question 7

How do bacteria invade host tissues?

Answer 7

Bacteria invade host tissues by causing damage and producing toxins. In tuberculosis, a tubercle is formed with dead bacteria and macrophages as it produces a coating to avoid macrophage digestion

Question 8

What are bactericidal antibiotics?

Answer 8

Bactericidal antibiotics kill bacteria. Examples include:
- Cell wall agents: Prevent cross-linking of cell walls, causing bacterial lysis (e.g., beta-lactams).
- Cell membrane agents: Cause metabolites to leak out and water to move in (e.g., penicillin).
- DNA gyrase inhibitors: Stop DNA from coiling, preventing it from fitting inside the bacterial cell (e.g., quinolones).

Question 9

What are bacteriostatic antibiotics?

Answer 9

Bacteriostatic antibiotics prevent bacterial growth. Examples include:
- Antimetabolites: Interrupt metabolic pathways like DNA synthesis (e.g., sulfonamides).
- Protein synthesis inhibitors: Prevent transcription and translation (e.g., tetracyclines).

Question 10

How does the local pH affect the effects of antibiotics?

Answer 10

The effects of antibiotics can depend on the local pH.

Question 11

What is antibiotic resistance?

Answer 11

Antibiotic resistance occurs when antibiotics exert selection pressure, and resistant alleles provide an advantage therefore more survive and reproduce which increases allele frequency in the population so the whole species may become resistant.

Question 12

What are healthcare-associated infections (HCAIs)?

Answer 12

Healthcare-associated infections (HCAIs) include infections like C. difficile (some antibiotics can destroy normal gut flora and reduce competition for this bacteria so it produces spores) and MRSA.

Question 13

What are the issues with antibiotic resistance?

Answer 13

Issues with antibiotic resistance include:
- Bacteria may become multi-resistant.
- Non-pathogenic bacteria may pass on resistant genes to other bacteria through horizontal gene transfer by plasmids.

Question 14

How can antibiotic resistance be prevented?

Answer 14

Antibiotic resistance can be prevented by regulating antibiotic use to prevent overuse and ensuring patients complete the full course of antibiotics, using narrow spectrum antibiotics, changing the type of antibiotic used to vary the selection pressure, control the use of antibiotics in agriculture and good hygiene + isolation of infected px.

Question 15

What are the methods for culturing bacteria?

Answer 15

Methods for culturing bacteria include:
- Cell counts: Using a microscope and haemocytometer which is diluted by trypan blue stain which only identifies living cells and is calibrated per volume of broth.
- Turbidity: A type of colorimetry, where the solution becomes more turbid as bacteria grow so that haemocytometer can be used to produce a calibration curve to relate number of bacteria to turbidity
- Dilution plating: Diluting the original culture until single colonies can be identified

Question 16

What is generation time in bacteria?

Answer 16

Generation time is the time between bacterial reproductions, which is limited by nutrient availability and the accumulation of waste.
- can be represented logarithmically

Question 17

What are the phases of bacterial growth?

Answer 17

The phases of bacterial growth include:
1. Lag phase: Bacteria are adapting to a new environment.
2. Log phase: Maximum reproduction occurs.
3. Stationary phase: The total growth rate is zero as the number of new cells formed = number of cells formed by binary fission
4. Death phase: The number of dying cells exceeds the number of new cells.

Question 18

What determines the tissue specificity of viruses?

Answer 18

Viruses are specific to particular tissues due to the presence of antigenic markers.

Question 19

What is the structure of the influenza virus?

Answer 19

The influenza virus has three main types: A (dangerous), B, and C. They are RNA viruses, which makes them more prone to mutation and antigenic variation

Question 20

What are protists?

Answer 20

Protists are unicellular eukaryotes.

Question 21

How is malaria caused and transmitted?

Answer 21

Malaria is caused by Plasmodium falciparum and is spread by the Anopheles mosquito vector

Question 22

How does sickle cell anemia provide resistance to malaria?

Answer 22

Individuals with sickle cell anemia have resistance to malaria.

Question 23

What is the life cycle of the malaria parasite?

Answer 23

Anopheles mosquitoes has mouth parts which contains anticoagulants to prevent blood clotting. The malaria parasite travels to the liver in the blood, where it invades red blood cells (RBCs) and reproduces asexually and burst to become gametophytes which are taken into female mosquitoes to respire sexually

Question 24

How can malaria be treated?

Answer 24

Malaria can be treated soon after infection with quinine, chloroquine, and artemisinin shortly after infection. But it is becoming resistant.

Question 25

What is the structure of fungi?

Answer 25

Fungi have a structure similar to plants. Their bodies are made up of hyphae filaments, cell walls made of chitin and large vacuoles

Question 26

How are fungi spread?

Answer 26

Fungi can be spread by spores.

Question 27

How can fungi be cultured?

Answer 27

Fungi can be cultured by measuring the diameter of growth patches or testing the dry mass of the microbe in a liquid growth medium.

Question 28

How can infectious diseases be transmitted?

Answer 28

Infectious diseases can be transmitted by contact with infected individuals, droplet infection, and exchange of bodily fluids even across placenta, food and vector

Question 29

How does the proportion of resistant or immune individuals affect transmission?

Answer 29

A higher proportion of resistant or immune individuals in the population leads to lower transmission rates.

Question 30

What factors affect disease transmission?

Answer 30

Factors affecting transmission include deprivation, migration, and cultural beliefs of humans.

Question 31

How can bacteria be cultured in a laboratory?

Answer 31

Bacteria can be cultured in nutrient broth or medium following aseptic techniques.

Question 32

How can a pure culture be obtained in a laboratory?

Answer 32

A pure culture can be achieved by growing under aerobic or anaerobic conditions, using a selective medium (required for genetically engineered organisms as antibiotic resistance is also engineered alongside a desired gene marker) and indicator media in order to separate the healthy microbiome of the body from pathogenic species.