bacteria and antibiotics Flashcards
how can bacteria be a cause of infection ?
when they invade and destroy host tissues, often producing damaging toxins
what is exotoxins ?
molecules released by bacteria into body fluids
what is endotoxins ?
molecules found in the cell walls of bacteria
list ways in which bacteria can gain entry to the body in variety of ways
wounds
intestine and lungs
passed between individuals
how can bacteria be transmitted ?
direct contact ‘droplets in the air food or water or by an intermediate organism known as the vector
how are exotoxins produced ?
released outside the bacterial cell
what are the effects of exotoxins ?
spread around the body in the blood or body fluids where they affect host cells
they have a range of effects
give an example of a pathogen that releases exotoxins
Staphylococcus
how does staphylococcus attack a cell ?
produce toxins that lead to toxic shock
it can be fatal
damage red blood cells
how are endotoxins produced ?
released from the bacterium if breaks down - treatment difficults
what are the effects of endotoxins ?
local to the site of infection
give an example of a pathogen that releases endotoxins
Salmonella
how does salmonella attack a cell ?
in the intestine where the endotoxin causes inflammation prevents water from being reabsorbed
is exotoxins gram positive or negative?
gram positive
is endotoxins gram positive or negative ?
gram negative
what are antibiotics ?
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
what are bactericidal antibiotics ?
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)
what are bacteriostatic antibiotics ?
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)
how does mycobacterium tuberculosis cause disease ?
- 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
what causes antibiotic resistance ?
- 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
why is it difficult to control the spread of antibiotic resistant bacteria ?
horizontal conjugation transfers plasmids with resistance allele from one bacterium to another rapidly
how could you avoid selection of resistant forms ?
- antibiotics should only be used when absolutely necessary
- every course of antibiotics should be completed
how do hospitals minimise the spread of antibiotic resistant bacteria ?
- 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
