Antibiotics Flashcards
_______________ is responsible for an estimated 2 million infections and 23,000 deaths per year in the united states.
Antibiotic resistance
Approximately half of outpatinet antibiotic prescribing in humans might be inappropriate.
At least 30% of outpatient antibiotic prescriptions in the United States are unnecessary.
Urgent threats:
-Carbapenem-resistant Acinetobacter
-Candida auris (C. auris)
-Clostridioides difficile (C. difficile)
-Carbapenem-resistant Enterobacteriaceae (CRE)
-Drug-resistant Neisseria gonorrhoeae (N. gonorrhoeae)
Serious threats:
-Drug resistant campylobacter
-drug resistant candida
-extended spectrum beta lactamase (ESBL) producing Enterobacteriaceae
-Vancomycin resistant enterococci (VRE)
-Multidrug resistant pseudomonas aeruginosa (P. aeruginosa)
-Drug resistant nontyphoidal salmonella
-Drug resistant shigella
-Methicillin resistant staphylococcus aureus (MRSA)
-Drug resistant streptococcus pneumoniae (S. pneumoniae)
-Drug resistant tuberculosis (TB)
Concerning threats:
-Erythromycin resistant group A streptococcus
-Clindamycin resistant group B streptococcus
Watch list:
-Azole resistant aspergillus fumigatus (A. fumigatus)
-Drug resistant mycoplasma genitalium (M. genitalium)
-Drug resistant Bordetella pertussis (B. pertussis)
Mechanisms of antibiotic resistance:
-Modifications of the antibiotic molecule
-Decreased antibiotic penetration and efflux
-Changes in target sites
-Resistance due to global cell adaptations
Antibiotic stewardship:
-to measure antibiotic prescribing
-to improve antibiotic prescribing by clinicians and use by patients so that antibiotics are only prescribed and used when needed.
-To minimize misdiagnoses or delayed diagnoses leading to the underuse of antibiotics
-to ensure that the right drug, dose, and duration are selected when an antibiotic is needed
Bactericidal:
kills sensitive organisms so that number of viable organisms falls rapidly after exposure
Bacteriostatic:
inhibits growth of bacteria but does not kill them
Narrow antimicrobial spectrum:
agent is active against a single species or limited group of pathogens
Broad antimicrobial spectrum:
agent is active against a wide range of pathogens
Extended antimicrobial spectrum:
agents falls in between (intermediate)
Mechanism of action:
-All beta-lactam antibiotics interfere with bacterial cell wall synthesis
-Inhibition of bacterial transpeptidase (also called penicillin-binding protein) which inhibits peptidoglycan cross-linking making cell wall synthesis impossible
-Generally, confers bactericidal activity
Penicillin V:
-Narrow spectrum antibiotic
-Typically administered in an oral suspension
-Adverse effects include GI upset, nausea, vomiting, diarrhea, and rash. In rare instances can cause severe hypersensitivity reactions.
-Considered the drug of choice for group A streptococcal pharyngitis
-Dosed by weight for adults and children
-People over 27 kg: 300mg TID or 600mg BID PO for 10 days
-People 27 kg or under: 40mg/kg/day divided BID or TID for 10 days with a maximum daily dose of 750 mg
Amoxicillin:
-An extended spectrum penicillin
-Essentially a modified version of penicillin that results in greater activity against additional gram-negative bacteria
-Generally well tolerated but can cause the same adverse effects as penicillin V
-Typically used more often asit is more palatable than penicillin V
-Dosed by body weight for all patients
-50mg/kg once daily or divided BID PO for 10 days with a maximum daily dose of 1000mg
Cephalosporins:
-A very large group of antibiotics
-The different generations are used to define their antimicrobial spectrum
-Have greater structural diversity which is more resistant to beta-lactamases and increases their range of antimicrobial activity
Cefadroxil:
-A first-generation cephalosporin
-May be used if treatment failure with penicillin or in individuals with nonimmediate hypersensitivity to penicillins
-Adverse effects include GI upset, nausea, vomiting, diarrhea, hypersensitivity (some cross-reactivity with penicillins)
Adults: 1g/gay PO as a single dose or divided BID for 10 days
Ceohalexin:
-A first generation cephalosporin
-Same adverse effect profile as cefadroxil and may also be used if treatment failure with penicillins or in individuals with nonimmediate hypersensitivity to penicillins
-Also available as a suspension
Adults: 500mg BID PO for 10 days
Children: 40mg/kg/day divided BID PO for 10 days with a maximum daily dose of 1000 mg
Protein synthesis inhibitors:
-Prokaryotic ribosomes are composed of a 30S and 50S subunit
-Eukaryotic mRNA translation proteins are far more complex than those in prokaryotic cells
Macrolides:
-Inhibit peptidyl transferase which functions to link amino acids together int he growing peptide chain
-Also interferes with translocation (movement of the nucleotide from the A position to the P position to allow for reading the next spot on the mRNA)
-Confers bacteriostatic activity
Azithromycin:
-An alternative for patients who are allergic to penicillin
-Less likely than other macrolide antibiotics to interact with other drugs
-Adverse effects include GI upset, nausea, vomiting, diarrhea, rash, QTc interval prolongation
Adults: 500mg PO for one day, then 250 mg PO daily for 4 days.
Children: 12 mg/kg PO for 5 days with a maximum daily dose of 500mg
Clarithromycin:
-An alternative for patients who are allergic to penicillin
-Same adverse effect profile as azithromycin
-Also available as a suspension
-Increase the levels of some common drugs like atorvastatin, lovastatin, simvastatin, and prednisone
Adults: 250mg BID PO for 10 days
Children: 15mg/kg/day divided BID PO for 10 days with a maximum daily dose of 500mg
Lacosamide:
-Interfere with translocation like macrolides but do not inhibit peptidyl transferase
-Approximately 4 times more likely to cause clostridium difficile infections compared to other antibiotics
-Generally bacteriostatic but can be bactericidal at high doses
Clindamycin:
-An alternative for patients who are allergic to penicillin
-May be used for treatment in symptomatic patients with multiple, recurrent episodes of pharyngitis
Commonly causes diarrhea as an adverse effect. Increased risk of C. difficile colitis
Adult: 300mg TID PO for 10 days
Children: 21 mg/kg/day divided TID PO for 10 days with a maximum daily dose of 900mg
Group A streptococcus pharyngitis:
-Antibiotic therapy is most beneficial for people who are at high risk of developing acute rheumatic fever and who have confirmed streptococcal infection
-Watchful waiting may be appropriate in patients at low risk for acute rheumatic fever as antibiotics have a minimal impact on the natural course of group A streptococcal pharyngitis
-According to evidence, antibiotics reduce duration of symptoms by approximately 16 hours
-Given the small benefit antibiotic therapy could be withheld for 48 -72 hours in adult patients with more severe symptoms
-Antibiotic therapy is not generally recommended for mild cases
Which of the following antibiotics is suitable for use in a patient with an immediate hypersensitivity reaction to penicillin?
A. Amoxicillin
B. Cephalexin
C. Cefadroxil
D. Azithromycin
D. Azithromycin
