Antibiotics in children

1. ANTIBIOTICS
 Antibiotics can be defined as substances capable ofkilling & inhibiting
the growthof micro organisms
 Mechanismof action
Inhibition of cellwall synthesis Penicillins
Cephalosporins
Monobactams
Vancomycin
Inhibition of DNA gyrase: Quinolones
RNA polymerase Rifampicin
Inhibition of protein synthesis: Aminoglycosides
Tetracyclines
Erythromycin
Chloramphenicol
Inhibition of folic acid metabolism: Trimethoprim
Sulfonamides
 Bacteriostatic vs. bactericidal drugs
• Bacteriostatic
– arrest the growth and replication of bacteria

2. – at serum levels achievable in the patient - limit the spread of infection
while the body's immune system attacks, immobilizes, and eliminates
the pathogens.
– If the drug is removed before the immune system has scavenged the
organisms, enough viable organisms may remain to begin a second
cycle of infection.
• Bactericidal
– kill bacteria at drug serum levels achievable in the patient. - often
drugs of choice in seriously ill patients.
• It is possible for ATB to be bacteriostatic for one organism and bactericidal
for another.
 Antimicrobial activity
• Antimicrobial activity: the ability that a drug kills or suppresses the growth
of microorganisms.
• Minimum inhibitory concentration(MIC)
– the minimum amount of a drug required to inhibit the growth of
bacteria in vitro.
• Minimum bactericidalconcentration(MBC)
– the minimum amount of a drug required to kill bacteria in vitro
 Classificationofantibacterialagents:
bactericidal bacteriostatic
β-lactam agents Erythromycin
Aminoglycosides Tetracyclines
Co-trimoxazole Chloramphenicol
Vancomycin Sulfonamides

3.  Chemotherapeutic spectra
 Narrow spectrum
only against a single or a limited group of microorganisms,
e.g. INH is active only against mycobacteria.
 Broadspectrum
e.g. tetracycline and chloramphenicol
affect a wide variety of microbial species.
!!! alter the normal bacterial flora
precipitate a superinfection of an organism, e.g., candida.
 Drug resistance
growth of bacteria is not halted by the maximal level of that antibiotic that can be
tolerated by the host.
 Primary
Some organisms are inherently resistant to an antibiotic
e.g., gram-negative organisms are inherently resistant to vancomycin.
 Secondary
spontaneous mutation or acquired resistance and selection.
 Cross-resistance
resistant to more than one antibiotic.