Microbes and Normal Flora

Question 1

What are the classes of microbial organisms?

Answer 1

Viruses
Bacteria
Fungi
Protozoa

Question 2

Viruses

Answer 2

RNA or DNA
No independent metabolism- can only exist in other cells
No organelles
Simple protein coat (cell membrane from host cell)

Eg:
Influenza
Rhinovirus
Herpes simplex
Ebola/Lassa
HIV

Question 3

Bacteria

Answer 3

DNA as a single chromosome
Independent metabolism
No organelles
Cell wall

Pepticoglycan cell wall= gram stain -ve

Lipopolysaccharide cell wall= gram stain +ve

Question 4

Fungi

Answer 4

DNA as multiple chromosomes
Independent metabolism and organelles
Cell wall

E.g Candida (candidiasis- thrush)

Question 5

Protozoa

Answer 5

DNA as multiple chromosomes
Independent metabolism
Organelles
Cell membrane

E.g. Giardia

Question 6

What do positive and negative gram stains indicate?

Answer 6

+ve: peptidoglycan cell wall

-ve: lipopolysaccharide cell wall

Question 7

What are the classes of bacteria?

Answer 7

Classified on gram staining and shape:

Gram stain +ve or -ve
Coccus (round) or bacillus (rod/elongated shape)

Question 8

Example of a gram positive cocci

Answer 8

Staphylococcus aureus and streptococcus species

Question 9

Example of gram negative cocci

Answer 9

Haemophilus influenzae

Question 10

Example of gram positive bacilli

Answer 10

Bacillus anthracis and lactobacilli species

Question 11

Example of gram negative bacilli

Answer 11

Salmonella, Escherichia coli (E Coli)

Question 12

Define symbiotic relationships

Answer 12

Close, long term interaction between 2 different species

Can be mutualistic, commensal or parasitic

Question 13

Define mutualistic interactions

Answer 13

Both parties benefit

Question 14

Define commensal interactions

Answer 14

One party benefits, no harm to the other party
E.g. colonisation
Normal gut flora

Question 15

Define parasitic interactions

Answer 15

One party benefits, the other is harmed.

Question 16

Define infection

Answer 16

Invasion and multiplication of microbes in an area of the body where they are not normally present. May cause symptoms or not. Does not necessarily cause disease.

Question 17

Define pathogen

Answer 17

Micro organism able to cause disease

Question 18

Define obligate pathogen

Answer 18

Pathogen that must cause disease in order to be transmitted from one host to another. Must infect host in order to survive.

Question 19

Define opportunistic pathogen

Answer 19

A pathogen that takes advantage of an opportunity not normally present, such as a host with a weak immune system (i.e. breached integumentary barrier, disrupted gut flora)

Question 20

What effects can antibiotics have on normal microbiota?

Answer 20

Can kill normal flora, allowing opportunity for pathological bacteria to invade (e.g. clostridium difficile)