Antimicrobial agentsPHG 423

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Antibiotic

• Chemicals that are produced by microorganisms (now include the synthetics (ciprofloxacin) and semi-synthetics (Ampicillin)) and that have the capacity to inhibit (static) the growth of, or to kill (cidal), bacteria and other microorganisms

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Microbial Origin of Antibiotics

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Microbial Origin of Antibiotics• Bacteria

– Bacillus sp (Gramicidin, Bacitracin, Polymyxins)• Fungi

– Penicillum sp (Penicillin)– Cephalosporium sp (Cephalosporins)– Fusidium sp (Fusidic acid)

• Actinomycetes– Streptomyces sp (Amino glycoside, tetracycline,

macrolide)– Micromonospora sp. (Gentamycin and netilmicin)

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Definitions• Antifungal agent: That kills or inhibits the growth of fungi.• Antiviral agent: That kills or inhibits the growth of virus.• Anti-infective agents: An agent natural or synthetic that

inhibits micro-organism or other infective organisms.

• The ability of the antibiotic to kill or inhibit the pathogenic microorganism without affecting the patient cell, this can be achieved when the antibiotic has a specific mechanism of action (specific target) not present in humans and it is effective at very low concentration.

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• Minimal inhibitory concentration is the lowest concentration of antibiotic producing inhibition of visible growth. The inhibition zone diameters have been correlated with MIC of the antibiotic obtained by serial dilution tests with standard bacterial inoculate.

• Minimum Bactericidal Concentration is the lowest concentration of antibiotic that yield no growth or results in 99.9% decline in the numbers of colonies counted in standardized volume that is subculture overnight in an antibiotic free medium.

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Mode of Action

• bactericidal = kill • bacteriostatic = stop multiplication• Bacteriostatic

– E.g. chloramphenicol, erythromycin, tetracyclines– Inhibit bacterial cell replication but do not kill the

organism• Bactericidal

– E.g. penicillins, cephalosporins, aminoglycoside– Cause microbial cell death and lysis

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Types of Antibiotics

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* 1910 Arsphenamine * 1912 Neosalvarsan * 1928 Penicillium chrysogenum * 1935 Prontosil * 1936 Sulfanilimide * 1939 sulfacetamide * 1940 sulfamethizole * 1942 benzylpenicillin * 1942 sulfadimidine * 1943 sulfamerazine * 1944 streptomycin * 1947 sulfadiazine * 1948 chlortetracycline * 1949 chloramphenicol * 1949 neomycin * 1950 oxytetracycline * 1950 penicillin G procaine * 1952 erythromycin * 1954 benzathine penicillin * 1955 spiramycin * 1955 tetracycline * 1955 thiamphenicol * 1955 vancomycin * 1956 phenoxymethylpenicillin * 1958 colistin * 1958 demeclocycline * 1959 virginiamycin * 1960 methicillin * 1960 metronidazole * 1961 ampicillin * 1961 spectinomycin * 1961 sulfamethoxazole * 1961 trimethoprim * 1962 cloxacillin * 1962 fusidic acid * 1963 fusafungine * 1963 lymecycline * 1964 gentamicin * 1966 doxacycline * 1967 carbenicillin * 1967 rifampicin * 1968 clindamycin * 1970 cefalexin

* 1971 cefazolin * 1971 pivampicillin * 1971 tinidazole * 1972 amoxicillin * 1972 cefradine * 1972 minocycline * 1972 pristinamycin * 1973 fosfomycin * 1974 talampicillin * 1975 tobramycin * 1975 bacampicillin * 1975 ticarcillin * 1976 amikacin * 1977 azlocillin * 1977 cefadroxil * 1977 cefamandole * 1977 cefoxitin * 1977 cefuroxime * 1977 mezlocillin * 1977 pivmecillinam * 1979 cefaclor * 1980 cefmetazole * 1980 cefotaxime * 1980 cefsulodin * 1980 piperacillin * 1981 amoxicillin/clavulanic acid * 1981 cefperazone * 1981 cefotiam * 1981 cefsulodin * 1981 latamoxef * 1981 netelmicin * 1982 apalcillin * 1982 ceftriaxone * 1982 micronomicin * 1983 cefmenoxime * 1983 ceftazidime * 1983 ceftiroxime * 1983 norfloxacin * 1984 cefonicid * 1984 cefotetan * 1984 temocillin * 1985 cefpiramide * 1985 imipenem/cilastatin

* 1985 ofloxacin * 1986 mupirocin * 1986 aztreonam * 1986 cefoperazone/sulbactam * 1986 ticarcillin/clavulanic acid * 1987 ampicillin/sulbactam * 1987 cefixime * 1987 roxithromycin * 1987 sultamicillin * 1987 ciprofloxacin * 1987 rifaximin * 1988 azithromycin * 1988 flomoxef * 1988 isepamycin * 1988 midecamycin * 1988 rifapentine * 1988 teicoplanin * 1989 cefpodoxime * 1989 enrofloxacin * 1989 lomefloxacin * 1990 arbekacin * 1990 cefozidime * 1990 clarithromycin * 1991 cefdinir * 1992 cefetamet * 1992 cefpirome * 1992 cefprozil * 1992 ceftibufen * 1992 fleroxacin * 1992 loracarbef * 1992 piperacillin/tazobactam * 1992 rufloxacin * 1993 brodimoprim * 1993 dirithromycin * 1993 levofloxacin * 1993 nadifloxacin * 1993 panipenem/betamipron * 1993 sparfloxacin * 1994 cefepime * 1999 quinupristin/dalfopristin * 2000 linezolid * 2001 telithromycin * 2003 daptomycin * 2005 tigecycline

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Bacterial Response to Therapy

• Antibiotic misuse– Use of antibiotics to treat infections they are inactive

against (viral infection )– Use of antibiotics in conditions of noninfectious

etiology because of misdiagnosis– Inappropriate prophylactic therapy– Misuse of antibiotics by the patients

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Bacterial Response to Therapy

• Host determinants – Sensitivity of MO to the drug– The appropriate dosage– Pharmacokinetics– Duration of therapy

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Mechanism of Action

• How the antibiotic perform its effect on micro-organisms– Inhibition of cell wall synthesis (β- lactams)– Destruction of cell membrane (Polyene)– Inhibition of protein synthesis (tetracycline)– Inhibition of nucleic acid function (rifampin inhibits

RNA polymerase and fluoroquinolones inhibit DNA gyrase)

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History of antibiotics• Ancient culture more than 2500 years ago old china

used mouldy bread to treat infection diseases.• North Americans and Indians used mouldy moccasins to

treat foot infections.• Middle ages (1600-1900): Europeans treated syphilis

using Hg and used quinine to treat malaria.• Pasteur noticed that one microorganism can kill another

when placed together.• Modern history (after 1928): Alexander Fleming (1929)

discover penicillin, he found that his penicillin was more harmful to bacteria and strongly active against Staphylococci and many other Gram-positive and Gram-negative Cocci.

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History of antibiotics• 1935 Florey and Chain: reinvestigated the discovery of

Fleming.• 1938 They isolated the first penicillin (Penicillin I) from

Penicillium notatum (fungi); it’s very effective against Staph. aureus but it was isolated in very small yield so it was very expensive to produce.

• 1939 Americans form search team to find a fungi similar to Penicillium notatum. They were able to isolate (penicillin II) the fungus Penicillium chrysogenum. They were able to isolate from the fungus a compound that very similar to penicillin I.

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History of antibiotics• 1939 Rane Bubous isolated the two antibiotics tyrocidine

and gramicidin (polypeptide) from the bacteria Bacillus brevis growing in soil.

• 1941 First clinical trial of penicillin G.• 1943 FDA approves Penicillin G for production and

marketing.• 1945 Fleming, Florey and Chain get the Nobel Prize.• 1949 Determination of the chemical structure of penicillin G

by X-ray.• Mid 1940's to late 1950's Most famous antibiotics were

discovered as tetracycline, chloramphenicol, streptomycine and erythromycine.

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History of antibiotics

• 1960's- 1970's Improvement of the characteristics of natural antibiotics ( pharmacokientics, potency and spectrum) through chemical modification as semisynthesis and derivatization.

• 1980's Discovery of new antibiotics through total chemical synthesis.

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History of antibiotics

• At the present time: All discovery and development and activities are as following: – Positive:– New natural sources for antibiotics.– 30% of hospital patients use antibiotics leading to

increases in health condition and increases of survival of patients.

– Negative:– Increases of the treatment coast and hospitalization.– Increases of development of resistance by pathogenic

organisms.

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Fermentation

• Derived from the latin word fervere which means to boil• In biotechnology, any process by which MOs are grown

in large quantities to produce any type of useful materials

• Production in huge amount … fermenters

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Microbial Growth

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Growth Curve

• Lag phase– Adaptation– Should be reduced to avoid the wastage of time and

to reduce the medium consumption– Reduced by using of previously inoculated cells

• Log phase– Exponential growth– Growth rate >> death rate– Primary metabolites production (required either for

growth or for energy, e.g., acetic acid, ethanol, citric acid)

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Growth Curve

• Stationary phase– Reduced level of nutrients, and accumulation of toxic

metabolites– Growth rate = death rate– Secondary metabolites production (toxins, alkaloids,

antibiotics, steroids), which produced in response to depletion of nutrients

• Death or decline phase

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Growth Medium

• Minerals & Vitamins (plant growth and differentiation)• Carbon/energy source (due to lack of photosynthesis)• Growth regulators (cell enlargement, division, and

differentiation)

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Minerals

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Factors affecting the Growth

• Temperature (Mesophils (39°C), Thermophiles (60°C), Psychrophiles (4°C))

• Oxygen (Aerobic, Anerobic, Faculative, Microaerophilic (low oxygen))

• pH (Neutrophiles, Acidophiles, Alkalinophiles)• Water (Halophiles (survive in NaCl (1-15%)),

Osmophiles (survive in high sugar), Xerophiles (survive in very dry environments))

• Light• Nutrients