AntibioticsAntibiotics

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Dr. Humodi A. SaeedDr. Humodi A. SaeedAssociate Prof. of Medical MicrobiologyAssociate Prof. of Medical MicrobiologyCollege of Medical Lab. ScienceCollege of Medical Lab. ScienceSudan University of Science and TechnologySudan University of Science and TechnologyE mail address: Biotechsust@hotmail.comE mail address: Biotechsust@hotmail.com

Definition of AntibioticA substance of biological, semisynthetic or

synthetic origin of low molecular weight (non-protein )produced by a fungus or

bacterium as secondary metabolites that inhibits or stop growth of other

microorganisms in vitro and in vivo selectively, when it used in low

concentration.

Characteristics of AntibioticsCharacteristics of AntibioticsIt must be able to It must be able to

reach the part of the reach the part of the human body where human body where

the infection is the infection is occurringoccurring..

Characteristics of AntibioticsCharacteristics of AntibioticsIt should not cause It should not cause

the development of the development of resistant forms of resistant forms of

parasitesparasites..

Characteristics of AntibioticsCharacteristics of AntibioticsIt should not It should not

produce undesirable produce undesirable side effects in the side effects in the host such as host such as allergic reaction, allergic reaction, nerve damage or nerve damage or irritation of the irritation of the kidneys and kidneys and gastrointestinal gastrointestinal tracttract..

Characteristics of AntibioticsCharacteristics of AntibioticsIt should be given It should be given

orally without orally without inactivation by inactivation by

stomach acid, or by stomach acid, or by injection injection

)parenterally( )parenterally( without binding to without binding to the blood proteinsthe blood proteins..

Characteristics of AntibioticsCharacteristics of AntibioticsFinally, it should Finally, it should

have a high level of have a high level of solubility in the solubility in the

body fluids and be body fluids and be possible to achieve possible to achieve concentrations in concentrations in

the tissue or blood, the tissue or blood, which are which are

sufficiently high to sufficiently high to inhibit or kill the inhibit or kill the infectious agentinfectious agent..

Major groups of AntibioticsMajor groups of AntibioticsBeta-lactam antibioticBeta-lactam antibiotic

11 . .PenicillinPenicillin22 . .CephalosporinsCephalosporins

33 . .CarbapenemsCarbapenems44 . .MonobactamsMonobactams

Toxicity ProblemToxicity ProblemThe main toxicity The main toxicity

problem with these problem with these antibiotics is an antibiotics is an

allergic reaction that allergic reaction that occurs because of occurs because of formation of beta-formation of beta-

lactam/serum lactam/serum protein conjugate protein conjugate

that elicits an that elicits an inflammatory inflammatory

immune responseimmune response..

Mode of ActionMode of ActionThe beta-lactam The beta-lactam

antibiotics inhibit the antibiotics inhibit the last step in last step in

peptidoglycan peptidoglycan synthesis, the synthesis, the

transformation reaction transformation reaction that cross links the that cross links the

peptide side chains of peptide side chains of the polysaccharide the polysaccharide

peptidoglycan peptidoglycan backbonebackbone..

SpectrumSpectrumSome are effective Some are effective

against both Gram-against both Gram-positive and Gram-positive and Gram-negative bacteria negative bacteria

whereas others are whereas others are more effective more effective against Gram-against Gram-

positive than Gram-positive than Gram-negative bacteria or negative bacteria or

vice versavice versa..