D6 Antibacterials

• Historical development of penicillin• How penicillin works• Patient compliance• Overprescription

Bacteria• Bacteria are single cells with a protective cell-wall made up of complex structures of Peptidoglucans

• They have a single chromosome- a plasmid• Anaerobic (no need of oxygen) or aerobic (need oxygen)• Some cause diseases, others are beneficial• Antibacterial are chemicals that prevent growth and

multiplication of bacteria

Early antibacterials• Trypan red, developed by the german chemist

Paul Erlich (1854-1915) to cure sleeping sickness

• Arsenamine, Salvarsan, was developed to cure syphilis. Paul Erlich responsible

• Prontosil, a sulpha drug, used against streptococcal bacteria (1935)

• Penicillin (1928)!

Fleming 1928

• Worked with Staphylococcus aureus• Left petri dish when he went on holiday• Discovered on comeback that it had moulded• The mould produced a substance that

inhibited growth of the bacteria• He called the substance penicillin, but didn’t

pursue his discovery

http://www.youtube.com/watch?v=7qeZLLhx5kU

Florey and Chain 1941• Learned how to isolate and purify penicillin• Used penicillin on policemen who was dying

from septicaemia (blood poisoning)• The structure of penicillin was determined in

1950’s- chemists could start synthesising it!• Fleming, Florey and Chain recieved the Noble

Prize in 1945

How penicillin works• Interferes with the enzyme that build the cell-

wall (which animal cells don’t have)• The weakened cell-wall disintegrates while the

bacterium grows, and it dies• Bacteria can become resistant by producing an

enzyme called penicillinase, which deactivates the penicillin

Benzylpencillin- has to be injected

Modifications of penicillin side chain

Beta-lactam-ring

Benzylpencillin potassium salt- more water soluble and less acidic

Piperacillin- broad spectrum antibiotic

Fluocloxacillin- is beta-lactamase stable

Amoxillin- better absorbed, used orally

Prescription of antibiotics

• It’s important to eat the whole cure of penicillin and to take it reguarly

• To not give the antibiotics to someone else• Specific bacteria crave different penicillins• Broad- and narrow-spectra penicillin• Combination of drugs can be used

Dangers with over-prescription

• Resistant bacteria• Kill ”the good” bacteria• Bacteria becomes immune- by mutation• Precribed although not needed

MRSA-bacteria

• Metillicin- Resistant Staphylococcus Aureus• The ”super bug”• Makes beta-lactamase which degrades

penicillin

Meticillin