Antimicrobial Drugs Rsistance
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Antimicrobial Drugs Rsistance
Dr. Mejbah Uddin Ahmed
Antibiotic resistance is the ability of a microorganism to withstand the effects of Antibiotics.
Mechanism of Drug resistance
The mechanisms by which microorganisms exhibit resistance to antimicrobials are:
Drug inactivation or modification: e.g. enzymatic deactivation of penicillin by production of β-lactamases.
Mechanism of Drug resistance
Alteration of target site:
♦ Alteration of PBP - Penicillins. ♦ Mutation in 30S ribosomal subunit Aminoglycosides. ♦ Replacement alanine with lactate in peptidoglycane – Vancomycin. ♦ Mutation in DNA gyrase – Quinolones. ♦ Mutation in RNA polymerase – Rifampicin.
Mechanism of Drug resistance
Alteration of metabolic pathway: e.g. some sulfonamide-resistant bacteria do not require para-aminobenzoic acid (PABA), an important precursor for the synthesis of folic acid and nucleic acid.
Mechanism of Drug resistance
Reduced drug accumulation: By decreasing drug permeability and/or increasing active efflux (pumping out) of the drugs across the cell surface - Tetracycline, Aminoglycoside.
Drug Resistance may be due to: ♦ Genetic: Chromosomal mutation Plasmid Transposon ♦ Non genetic.
Chromosome Mediated Resistance: * Due to mutation in the gene. * Frequency ranges from 107 – 109.
Plasmid Mediated Resistance: * Occurs in many different species. * Frequently to multiple drugs. * High rate of transfer from one bacteria to another bacteria.
Transposon Mediated Resistance Transfer drug resistance gene from one bacteria to another.
Nongenetic Basis of Resistance: Several factors are responsible nongenetic drug resistance: * Abscess cavity. * Wrong - dose, route, drug. * Protoplast stage. * Presence of foreign body.
What To Do ??? When you are prescribing an antibiotic:
Should follow right drug, dose, route, duration.
Do not save any antibiotics for the next time.
Do not take antibiotics prescribed for someone else. The antibiotic may not be appropriate for your illness. Taking the wrong medicine may delay correct treatment and allow bacteria to multiply.
Antibiotics not for Colds and Flu Taking antibiotics for viral infections like - cold, cough & flu: ▪ Will not cure the infection ▪ Will not inhibit spread to other individuals. ▪ Will not help a person feel better ▪ May cause an unnecessary, harmful side effect
Antibiotic susceptibility test
Minimum inhibitory concentration (MIC): Lowest concentration of drug that
inhibits
growth of bacteria.
▪ Minimum bactericidal concentration (MBC): Lower concentration of drug that kill bacteria.
Antibiotic susceptibility test
There are two method for antibiotic susceptibility tests:
Disc diffusion method
Tube dilution method
8 m g / L
4 m g / L
2 m g / L
a m o u n to f a n tib io tic M IC = 2 m g /L
1 m g / L
0 .5 m g /L
c lo u d in e s s m e a n s b a c te r ia c a n g r o w a t th a tc o n c e n tr a tio n o f a n tib io tic
0 .2 5 m g /L
Disc diffusion method
MRSA: stands for Methicillin-resistant Staphylococcus aureus. This type of bacteria causes “staph” infections that are resistant to usual antibiotics.
VRE (vancomycin-resistant enterococci): Enteroccocci are normally present in the human intestines and in the female genital tract and in the environment.
VISA
Dr. Mejbah Uddin Ahmed
Antibiotic resistance is the ability of a microorganism to withstand the effects of Antibiotics.
Mechanism of Drug resistance
The mechanisms by which microorganisms exhibit resistance to antimicrobials are:
Drug inactivation or modification: e.g. enzymatic deactivation of penicillin by production of β-lactamases.
Mechanism of Drug resistance
Alteration of target site:
♦ Alteration of PBP - Penicillins. ♦ Mutation in 30S ribosomal subunit Aminoglycosides. ♦ Replacement alanine with lactate in peptidoglycane – Vancomycin. ♦ Mutation in DNA gyrase – Quinolones. ♦ Mutation in RNA polymerase – Rifampicin.
Mechanism of Drug resistance
Alteration of metabolic pathway: e.g. some sulfonamide-resistant bacteria do not require para-aminobenzoic acid (PABA), an important precursor for the synthesis of folic acid and nucleic acid.
Mechanism of Drug resistance
Reduced drug accumulation: By decreasing drug permeability and/or increasing active efflux (pumping out) of the drugs across the cell surface - Tetracycline, Aminoglycoside.
Drug Resistance may be due to: ♦ Genetic: Chromosomal mutation Plasmid Transposon ♦ Non genetic.
Chromosome Mediated Resistance: * Due to mutation in the gene. * Frequency ranges from 107 – 109.
Plasmid Mediated Resistance: * Occurs in many different species. * Frequently to multiple drugs. * High rate of transfer from one bacteria to another bacteria.
Transposon Mediated Resistance Transfer drug resistance gene from one bacteria to another.
Nongenetic Basis of Resistance: Several factors are responsible nongenetic drug resistance: * Abscess cavity. * Wrong - dose, route, drug. * Protoplast stage. * Presence of foreign body.
What To Do ??? When you are prescribing an antibiotic:
Should follow right drug, dose, route, duration.
Do not save any antibiotics for the next time.
Do not take antibiotics prescribed for someone else. The antibiotic may not be appropriate for your illness. Taking the wrong medicine may delay correct treatment and allow bacteria to multiply.
Antibiotics not for Colds and Flu Taking antibiotics for viral infections like - cold, cough & flu: ▪ Will not cure the infection ▪ Will not inhibit spread to other individuals. ▪ Will not help a person feel better ▪ May cause an unnecessary, harmful side effect
Antibiotic susceptibility test
Minimum inhibitory concentration (MIC): Lowest concentration of drug that
inhibits
growth of bacteria.
▪ Minimum bactericidal concentration (MBC): Lower concentration of drug that kill bacteria.
Antibiotic susceptibility test
There are two method for antibiotic susceptibility tests:
Disc diffusion method
Tube dilution method
8 m g / L
4 m g / L
2 m g / L
a m o u n to f a n tib io tic M IC = 2 m g /L
1 m g / L
0 .5 m g /L
c lo u d in e s s m e a n s b a c te r ia c a n g r o w a t th a tc o n c e n tr a tio n o f a n tib io tic
0 .2 5 m g /L
Disc diffusion method
MRSA: stands for Methicillin-resistant Staphylococcus aureus. This type of bacteria causes “staph” infections that are resistant to usual antibiotics.
VRE (vancomycin-resistant enterococci): Enteroccocci are normally present in the human intestines and in the female genital tract and in the environment.
VISA
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