Microbiology

Question 1

Outer surface (cell wall/ membrane) of viruses, bacteria, fungi and protozoa/ helminths

Answer 1

Viruses: Protein capsid made up of capsomeres

Bacteria: Cell wall made up of peptidoglycan

Fungi: Cell wall made up of chitin

Protozoa and helminths: flexible membrane

Question 2

Helminths

Answer 2

Multicellular worms that infest body, mainly GI tract.

Transmission can be direct or indirect via an intermediate non-human host.

Question 3

Protozoa

Answer 3

Single cell organisms. Have a dormant and active stage. Acquired by contaminated water.

Question 4

Fungi

Answer 4

Single cell or brainched or both organisms. Have a cell wall made up of chitin. Disease caused by environment or part of the normal flora.

Question 5

Bacterial cell wall structure

Answer 5

Multilayered structure mainly composed of peptidoglycans, which is glycan chain and tetrapeptide chain.

Question 6

Difference between Gram + and Gram - cell wall

Answer 6

Gram +: thick cell wall, no outer membrane or lipopolysaccharides, no porins. Gram -: Thin cell wall, outer membrane containing lipopolysaccharides, as well as porins.

Question 7

Structure of capsule in Bacteria

Answer 7

gelatinous layer outside cell wall made up of polysaccharides.

Determinant of virulence. Helps with adherence. Helps with identification of a bacteria in lab.

Question 8

2 Roles of pilli

Answer 8

1. Attachement
2. Conjugation (sexual reproduction)

Question 9

Spores in Bacteria

Answer 9

produced by some gram positive bacteria, highly resistant structures resistant to harsh conditions.

Question 10

Components of viruses

Answer 10

DNA or RNA genome, capsid core, polymerase protein. Sometimes envelope.

Question 11

name of the viral genome enclosed by capsid protein coat

and

Subunits of capsid

Answer 11

nucleocapsid

capsomeres

Question 12

Icosahedral capsid

Answer 12

made up of 20 equilateral triangular faces arranged around the surface of a sphere. Each triangle is made of min 3 proteins.

Question 13

Helical capsid

Answer 13

Proteins are arranged in a helix around the DNA.

Question 14

Viral Envelope

Answer 14

Lipid bilayer from host cell membrane surrounding certain viruses.

Has glycoproteins attached to its surface (spikes). It determines the stability of virus: enveloped ones cannot live outside host.

Question 15

Importance of viral surface protein

Answer 15

Attach to membrane proteins and binding sites for antibodies.

Question 16

Describe the three types of symbiotic associations : Commensalism, mutualism and parsitism

Answer 16

Commensalism: one benefits other whatevs Mutualism: both benefit Parasitism: one benefits at expense of other

Question 17

Opportunistic infections

Answer 17

Causes by non pathogenic microorganisms that act as pathogen in certain circumstances.

E.g. normal flora in other part of body, immunicompromisation, lack of normal flora.

Question 18

Microbial pathogenesis

Answer 18

The process by which infection leads to disease

Question 19

Immunopathogenesis

Answer 19

When pathology is caused by overwhelming immune response.

E.g. cytotoxic T Cell mediated attack, antibody-mediated damage to the host, antibody mediated complement fixation

Question 20

Stages of infectious disease (4)

Answer 20

Incubation Prodrome Illness Recovery

Question 21

Communicable vs non communicable disease.

Answer 21

Communicable: Transmissible (directly or indirectly)

Non communicable: non transmissible to humans.

Question 22

Nosocomial infections

Answer 22

Infections acquired in a hospital or medical facility.

Question 23

Iatrogenic infections

Answer 23

Infection caused by distruption to the body’s normal mechanical barriers

e.g. injury associated with therapy, metal/ plastic implants

Question 24

Molecules on bacteria that attach to the host cells and how Viruses attach to host cells

Answer 24

bacteria: Adhesins

Viruses have proteins that bind to receptros on the host cell membrane. This induces a conformational change that leads to membrane penetration. They also have attachement factors which help viruses concentrate at the cell surface.

Question 25

Host range

Answer 25

The range of hosts a pathogen can infect

Question 26

Tissue tropism

Answer 26

tissues within a host that a pathogen can infect

Question 27

Permissive cell

Answer 27

One that allows proliferation of pathogen

Question 28

Virulence: what is it and what determines it (4)

Answer 28

The degree of the ability for a microbe to cause disease

Question 29

Answer 29

Question 30

Steps of viral replication

Answer 30

Question 31

-RNA, +RNA, double stranded DNA in virus how they are converted to mRNA for host cell replication

What retroviruses do?

Answer 31

+RNA: Can be used directly as it is the same as cell mRNA

-RNA: Needs to be made into +RNA by RNA polymerase

DNA: Needs to be made into mRNA by cell

Retroviruses use +RNA and make them into double stranded DNA using reverse transcriptase

Question 32

Superficial or systemic types of infection

Answer 32

Question 33

Types of persistent infections (latent and chronic) what they mean

Answer 33

Question 34

Describe what each of the following invasins (enzymes that help with spread of bacteria) do:

Collagenase and hyaluronidase

Coagulase

Leukocidins

Hemolysins

Answer 34