NSC 830 EKU PHARMACOLOGY-ANTIBIOTICS
Narrow spectrum
-Treats limited # of organisms
-Less likely to disrupt normal flora
-Used when organism has been identified
Extended spectrum
-Treats multiple organisms
-More likely to disrupt normal flora
-Used when specific causative organism is unknown
Gram-positive bacteria
-bacteria that give a positive result
in the gram-stain test. Gram-positive bacteria take up the crystal violet stain used in the
test, and then appear to be purple-colored when seen through a microscope. This is
because the thick peptidoglycan layer in the bacterial cell wall
retains the stain after it is washed away from the rest of the sample, in the
decolorization stage of the test.
-Despite their thicker peptidoglycan layer, gram-positive bacteria are more receptive to
antibiotics than gram-negative, due to the absence of the outer membrane.
-Gram + had a thick peptidoglycan layer in their cell wall (stain purple)
Examples of Gram-positive bacteria
• Group A beta-hemolytic streptococci
• Streptococcus pneumonia
Gram-negative bacteria
-cannot retain the violet stain after the
decolorization step; alcohol used in this stage degrades the outer membrane of gram-
negative cells making the cell wall more porous
and incapable of retaining the crystal violet stain. -Their peptidoglycan layer is much
thinner and sandwiched between an inner cell membrane and a bacterial outer
membrane, causing them to take up the counterstain (safranin or fuchsine) and appear
Red or Pink
-Gram - had a thin peptidoglycan layer, but has an outer membrane (stain red/pink)
,Examples of Gram-negative bacteria
• Haemophilus influenza
• Neiserria gonococcus
Atypical bacteria
-bacteria that do not color with gram-staining, but remain colorless: they are neither
gram-positive nor gram-negative.
-The atypical organisms lack a peptidoglycan layer so do not retain crystal violet or
safranin,
resulting in no color
-Peptidoglycans are the site of action of beta-lactam antibiotics such as penicillins and
cephalosporins, so atypical bacteria are naturally resistant to these drugs, which in this
sense
also makes them "atypical" in the treatment of their infections. Macrolides such as
erythromycin however, are usually effective.
Examples of Atypical bacteria
• Chlamydia pneumoniae
• Mycoplasma pneumoniae
• Legionella
Drug Resistant Strep Pneumoniae (DRSP) risk factors
• Recent antibiotic use
• Older (>65 yo)
• Multiple comorbidities (COPD, DM, HF, renal failure)
• Daycare worker
• Alcoholism
• Immunosuppressed (including chronic corticosteroid use >10 mg/day long term)
Drug Resistant Strep Pneumoniae (DRSP) Treatment
• High dose amoxicillin (3-4 g/day)
• Respiratory fluoroquinolones: moxifloxacin, gemifloxacin, levofloxacin (broad
spectrum)
• telithromycin (Ketek) - use limited due to hepatotoxicity
*this bacteria wont be suseptible to regular AB doses
Other factors to consider when determining drug selection
, • Allergy history
• Penicillins -risk of cross-allergy to cephalosporins
• Age
• Renal function - neonates & elderly
• Pregnancy
• Example: Contraindicated: tetracyclines (tetrogenic), fluoroquinolone (interfere w joints
and cartilidge/bone growth
-Immunocompromised status: Immunomompromised require bactericidals & extended
therapy
• Affordability: PCNs inexpensive
• Taste & convenience-Liquid
• Number of times of dosing/day
What is Bacteriostatic-
Restrains reproduction of bacteria (arrest the growth)
*would need a good immune sx for the AB to work-not be immunocomprimised
What is Bactericidal
Kills the bacteria
Minimum Inhibitory Concentration (MIC)
• Lowest concentration of an antimicrobial that will inhibit visible growth of a
microorganism after overnight incubation under standard conditions
Antibiotics usually dosed at level to 2-4 times MIC
• "overkill" refers to the amount to allow for variations in absorption, distribution
Beta-Lactam Antibiotics Include which meds for primary and hospital
1. Primary care: penicillins &
2. cephalosporins
Hospital: 3. Monobactams &
4. carbapenems
-These antibiotics have a beta lactam ring that is part of their chemical Structure
What is the beta-lactum ring
-The beta-lactam ring works by disrupting the biosynthesis of the bacterial cell wall
-Several bacteria produce beta-lactamase enzymes that open the beta-lactam ring &
inactivate the antibiotic
-Intact ring essential for antibacterial activity
Narrow spectrum
-Treats limited # of organisms
-Less likely to disrupt normal flora
-Used when organism has been identified
Extended spectrum
-Treats multiple organisms
-More likely to disrupt normal flora
-Used when specific causative organism is unknown
Gram-positive bacteria
-bacteria that give a positive result
in the gram-stain test. Gram-positive bacteria take up the crystal violet stain used in the
test, and then appear to be purple-colored when seen through a microscope. This is
because the thick peptidoglycan layer in the bacterial cell wall
retains the stain after it is washed away from the rest of the sample, in the
decolorization stage of the test.
-Despite their thicker peptidoglycan layer, gram-positive bacteria are more receptive to
antibiotics than gram-negative, due to the absence of the outer membrane.
-Gram + had a thick peptidoglycan layer in their cell wall (stain purple)
Examples of Gram-positive bacteria
• Group A beta-hemolytic streptococci
• Streptococcus pneumonia
Gram-negative bacteria
-cannot retain the violet stain after the
decolorization step; alcohol used in this stage degrades the outer membrane of gram-
negative cells making the cell wall more porous
and incapable of retaining the crystal violet stain. -Their peptidoglycan layer is much
thinner and sandwiched between an inner cell membrane and a bacterial outer
membrane, causing them to take up the counterstain (safranin or fuchsine) and appear
Red or Pink
-Gram - had a thin peptidoglycan layer, but has an outer membrane (stain red/pink)
,Examples of Gram-negative bacteria
• Haemophilus influenza
• Neiserria gonococcus
Atypical bacteria
-bacteria that do not color with gram-staining, but remain colorless: they are neither
gram-positive nor gram-negative.
-The atypical organisms lack a peptidoglycan layer so do not retain crystal violet or
safranin,
resulting in no color
-Peptidoglycans are the site of action of beta-lactam antibiotics such as penicillins and
cephalosporins, so atypical bacteria are naturally resistant to these drugs, which in this
sense
also makes them "atypical" in the treatment of their infections. Macrolides such as
erythromycin however, are usually effective.
Examples of Atypical bacteria
• Chlamydia pneumoniae
• Mycoplasma pneumoniae
• Legionella
Drug Resistant Strep Pneumoniae (DRSP) risk factors
• Recent antibiotic use
• Older (>65 yo)
• Multiple comorbidities (COPD, DM, HF, renal failure)
• Daycare worker
• Alcoholism
• Immunosuppressed (including chronic corticosteroid use >10 mg/day long term)
Drug Resistant Strep Pneumoniae (DRSP) Treatment
• High dose amoxicillin (3-4 g/day)
• Respiratory fluoroquinolones: moxifloxacin, gemifloxacin, levofloxacin (broad
spectrum)
• telithromycin (Ketek) - use limited due to hepatotoxicity
*this bacteria wont be suseptible to regular AB doses
Other factors to consider when determining drug selection
, • Allergy history
• Penicillins -risk of cross-allergy to cephalosporins
• Age
• Renal function - neonates & elderly
• Pregnancy
• Example: Contraindicated: tetracyclines (tetrogenic), fluoroquinolone (interfere w joints
and cartilidge/bone growth
-Immunocompromised status: Immunomompromised require bactericidals & extended
therapy
• Affordability: PCNs inexpensive
• Taste & convenience-Liquid
• Number of times of dosing/day
What is Bacteriostatic-
Restrains reproduction of bacteria (arrest the growth)
*would need a good immune sx for the AB to work-not be immunocomprimised
What is Bactericidal
Kills the bacteria
Minimum Inhibitory Concentration (MIC)
• Lowest concentration of an antimicrobial that will inhibit visible growth of a
microorganism after overnight incubation under standard conditions
Antibiotics usually dosed at level to 2-4 times MIC
• "overkill" refers to the amount to allow for variations in absorption, distribution
Beta-Lactam Antibiotics Include which meds for primary and hospital
1. Primary care: penicillins &
2. cephalosporins
Hospital: 3. Monobactams &
4. carbapenems
-These antibiotics have a beta lactam ring that is part of their chemical Structure
What is the beta-lactum ring
-The beta-lactam ring works by disrupting the biosynthesis of the bacterial cell wall
-Several bacteria produce beta-lactamase enzymes that open the beta-lactam ring &
inactivate the antibiotic
-Intact ring essential for antibacterial activity
