All lectures of the course Antimicrobial Compounds of the Minor "Topics in Biomedical Sciences"
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LECTURES – PART 1
1.1 – HISTORY OF ANTIBIOTICS
ANTIMICROBIALS
Importance of antimicrobials
= One of most successful medications ever discovered
1) Huge benefit for patient
2) Low toxicity
3) Low costs
- Reduction surgical wound infection 40% → 2%
- Antibiotics increased average life span with 10 years
o In perspective: Curing cancer would increase average lifespan by 3 years
- Antimicrobials: compounds active against
1) Bacteria
2) Viruses
3) Protozoa
4) Yeasts and fungi
5) Worms
FIRST ANTIBIOTICS
SALVARSAN
Paul Ehrlich (1854-1915)
- “To achieve success in antimicrobial research, one needs the four G’s: Geld, Geduld, Geschick
and Gluck – money, patience, intelligence and luck.”
- Trained as a chemist
- 1908: Nobel prize
- Development and testing different staining techniques for blood cells
o Discovery of mast cells – staining of specifically mast cells
→ Development idea of specific receptor for stains: something in the cells specific for binding
to a dye → “If tissues and cells can be specifically targeted by dyes, they might also be
specifically targeted by toxic dyes”
- Therapia Sterilisans Magna – Magic Bullet: Discover a treatment that could, in a single dose,
destroy all microorganisms in the infected organism
o To achieve this, the optimal agents would combine high parasitotropism with low
organotropism
- Discovery of Salvarsan
1. Focus on arsenic derivatives → combination: basic dye + aniline +
toxin (arsenic acid)
→ Arsanilic acid
§ Active
§ Highly toxic
2. Modification of amino group
→ Arsacetin
§ Less toxic
§ Activity in vivo
§ No activity in vitro
→ Hypothesis: compounds activated in vivo by modification
• Now known modification = reduction
3. Focus on arsenobenzenes → reduction toxicity
→ Arsanenophenylglycine
, → Arsenophenol
§ Difficult to produce
§ Prone to oxidation
4. Addition of amino group to arsenophenol
→ Diaminodioxyarsenobenzol – Salvarsan, Compound 606
o First antimicrobial drug
o Use of Salvarsan: working against spirochetes – Treponema
pallidum = cause of syphilis
o Activation of Salvarsan in vivo → Oxophenarsine
o Treatment with arsenicals prolonged (18 months) + unpleasant → combination
therapy with mercury and/or bismuth → destruction all spirochetes
§ Prevention appearance of resistance + disease recurrence
PRONTOSIL
Gerhard Domagk (1895-1964)
- German physician
- Failure of medicine to treat battle wounds in World War I → find cure for infectious diseases
- Continued in line of research initiated by Ehrlich at IG Farben laboratories in Wuppertal
1. Synthesis of potential antibacterials by chemists
2. Testing by Domagk on animals + in vitro
o Particularly: test organism against highly virulent Streptococcus hemolyticus
o Involvement of assistants + animal-care support staff
o 1929: Around 30 new products tested per week
3. Abandonding work with quinine derivatives and compounds containing gold →
working with azo dyes
§ Binding to various cells
§ Used as bacterial stains
4. 1932: Addition sulfur atoms to the dye
5. Success after one improvement
→ Sulfamidechrysoidine – Prontosil
§ No activity against streptococci in vitro
§ Activity/protection of infected mice
= active in vivo, not active in vitro
§ 1936: Tested on humans
• Side-effect: red skin (due to the dye)
• Recovery from infection
- 1939: Nobel Prize
- Discovery of Sulfanilamide
o In vivo metabolization of Prontosil → breakdown into active form: Sulfanilamide
o Function in bacteria: competitive inhibitor of
hydropteroate synthetase (DHPS)
§ DHPS: enzyme involved in folate biosynthesis
• Folate: produced by bacteria → needed
for growth
• Blocking folate = blocking growth of
bacteria
o Used in combination with trimethoprim
§ Trimethoprim: folate biosynthesis blocker
• Different part of pathway of folate production blocked compared to
sulfanilamide
, → Co-trimoxazol
PENICILLIN
Alexander Fleming (1881-1955)
- Studied use of Salvarsan
- Studied antimicrobial activity in nasal mucus and tear fluid
→ discovery of lysozyme
o Too big molecule to use
- 1928: Contamination on Staphylococci plates → Penicillium notatum fungus killed
staphylococci
→ Penicilin
o Activity secreted by fungus
o Low toxicity
o Drawbacks
1. Unable to isolate compound in high quantities
2. Not tested on infected animals
3. Unable to determine structure
→ not of interest to chemist
Florey and Chain
- Chemists working on antibacterial compounds
- Studied Fleming’s work on lysozyme
- Studied Fleming’s other discovery → interest in Penicillin
a) Different fungus: Penicillium chrysogenum
b) Different culturing techniques
→ successful isolation larger quantities penicillin → testing possible on
patients
- 1945: Nobel Prize
- Penicillin
o Treatment
§ Wounds on battlefield
§ Surgical wounds
§ Use for STDs → soldiers with gonorrhoea
• Treatment of STD = faster recovery than wounds = first use of
Penicillin during war – soldier back to fight quicker
o One class of β-lactam antibiotics
Penicillins Cephalosporins Carbapenems
STREPTOMYCIN
Selman Waksman (1882-1973)
- Soil microbiologist
- 1940: Systematical screening soil microorganism for production antimicrobial compounds
o Natural compounds produced by one microorganism against other microorganisms
- Discovery 10 different antibiotics
o Term ‘antibiotic’: opposite of symbiose between microorganisms = antibiosis –
compounds needed to fight other microorganisms, involved in antibiosis = antibiotics
→ Streptomycin
, o Produced by Streptomyces griseus
o First antibiotic effective against Mycobacterium
tuberculosis
§ Disease: tuberculosis
o Treatment of tuberculosis
§ Effective: 2-3 weeks → recovery
§ High relapse rate: >80%
§ Relapsed patients more difficult to treat
§ Prolonged combination therapy successful
• Cause: biphasic killing
= First days of treatment sensitive
population (95-99%) killed, persistent
population stays, different state =
more difficult to kill, more time
necessary
• Treatment
1. Two months intensive course
o Isoniazid
o Ethambutol
o Pyrazinamide
o Rifampicin
2. Four months continuation course
o Isoniazid
o Rifampicin
- 1952: Nobel Prize
- Waksman screening platform → golden age of antibiotics
o After Wakmans screening discovery → discovery lots of antibiotics in short period of
time
o Antibiotic Innovation Gap
§ (Almost) no new discoveries
§ Reasons
1) Scientifically: ‘easy’ targets were found, drug screening for new
antibiotics leading to re-discovery same lead compounds → discovery +
development antibiotics scientifically more complex, expensive and time
consuming
2) Economically: antibiotics provide poor return on investment relative to
other classes of drugs + new promising drugs only used in problematic
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