bacteria and antibiotics

Question 1

how can bacteria be a cause of infection ?

Answer 1

when they invade and destroy host tissues, often producing damaging toxins

Question 2

what is exotoxins ?

Answer 2

molecules released by bacteria into body fluids

Question 3

what is endotoxins ?

Answer 3

molecules found in the cell walls of bacteria

Question 4

list ways in which bacteria can gain entry to the body in variety of ways

Answer 4

wounds
intestine and lungs
passed between individuals

Question 5

how can bacteria be transmitted ?

Answer 5

direct contact ‘droplets in the air food or water or by an intermediate organism known as the vector

Question 6

how are exotoxins produced ?

Answer 6

released outside the bacterial cell

Question 7

what are the effects of exotoxins ?

Answer 7

spread around the body in the blood or body fluids where they affect host cells
they have a range of effects

Question 8

give an example of a pathogen that releases exotoxins

Answer 8

Staphylococcus

Question 9

how does staphylococcus attack a cell ?

Answer 9

produce toxins that lead to toxic shock
it can be fatal
damage red blood cells

Question 10

how are endotoxins produced ?

Answer 10

released from the bacterium if breaks down - treatment difficults

Question 11

what are the effects of endotoxins ?

Answer 11

local to the site of infection

Question 12

give an example of a pathogen that releases endotoxins

Answer 12

Salmonella

Question 13

how does salmonella attack a cell ?

Answer 13

in the intestine where the endotoxin causes inflammation prevents water from being reabsorbed

Question 14

is exotoxins gram positive or negative?

Answer 14

gram positive

Question 15

is endotoxins gram positive or negative ?

Answer 15

gram negative

Question 16

what are antibiotics ?

Answer 16

chemicals that target differences in structure or biochemistry between bacteria calls and mammalian cells, in order to stop bacterial cells, in order to stop bacterial cells from growing in one body

Question 17

what are bactericidal antibiotics ?

Answer 17

Antibiotics that kill bacteria by destroying cell walls causing bacteria to burst

Especially effective against Gram-positive as cell wall is so thick

(e.g. penicillin)

Question 18

what are bacteriostatic antibiotics ?

Answer 18

Antibiotics that inhibit the growth of bacteria by stopping protein synthesis and production of nucleic acids so bacteria cannot replicate

Especially effective against Gram-negative as lipid bilayer is damaged

(e.g. tetracycline)

Question 19

how does mycobacterium tuberculosis cause disease ?

Answer 19

• triggers inflammatory response by infecting phagocytes in lungs
• infected phagocytes are sealed in waxy coated tubercles so bacteria remain dormant first infection has no symptoms
• if another factor weakens immune system, bacteria become active and destroy lung tissue

Question 20

what causes antibiotic resistance ?

Answer 20

• random gene mutation, often on plasmid, confers resistance
• these bacteria have selective advantage in the presence of antibiotics, reproduce and pass allele for resistance to offspring
• directional selection results in resistant strain

Question 21

why is it difficult to control the spread of antibiotic resistant bacteria ?

Answer 21

horizontal conjugation transfers plasmids with resistance allele from one bacterium to another rapidly

Question 22

how could you avoid selection of resistant forms ?

Answer 22

• antibiotics should only be used when absolutely necessary
• every course of antibiotics should be completed

Question 23

how do hospitals minimise the spread of antibiotic resistant bacteria ?

Answer 23

• alcohol based gels to be used by medical staff, patients and visitors
• doctors and other staff should wear clean clothing
• through cleaning the hospital wards
• isolation of infected patients
• screening patients for infection as they come into hospital
• monitoring levels of healthcare - acquired infections