Anti-infectives Flashcards
What are common causes of drug resistance?
- Overuse of broad-spectrum abx.
- Over prescription of abx. for viral illnesses
- Use of abx in animals that enter the food chain
Gram + organisms definition
Type of bacteria has a cytoplasmic membrane surrounded by a touch rigid mesh cell wall.
- Ex: staph aureus, strep pneumoniae, clostridium
- stain purple
Gram - organisms definition
Type of bacteria has a thin cell wall surrounded by a second lipid membrane.
- Ex: E. coli, pseudomonas, H. pylori, Neisseria, gonerrhea, salmonella - stain pink
Obligate aerobes
Organism needs oxygen to survive
Obligate anaerobes
Organism is poisoned by oxygen
Facilitative anaerobes
Can grow with or without oxygen because they can metabolize aerobically or anaerobically.
Bacteriostatic
Antibiotic which stops growth of bacteria but does not kill bacteria
Typically requires a higher concentration
Bactericidal
Antibiotic which kills bacteria
- important to use this type in patients that are immunocompromised
What are mechanisms of action for antibiotics?
Important factors to keep in mind when prescribing antibiotics:
- immune system function
- renal and hepatic function
- Age
- Pregnancy/lactation
- Risk for multi-drug-resistance organisms
- Patient adherence: lowest frequency for the shortest duration - cost effective
- for kids: taste good and most concentrated dose
Name common gram + organisms and where the common infections they cause
•Staphylococcus aureus
-Commonly causes skin infections
–Can also cause endocarditis, sepsis, osteomyelitis, pneumonia
•Streptococcus
–Pyogenes (pharyngitis [GAS], impetigo, cellulitis)
–Pneumoniae (pneumonia, meningitis, sepsis)
–Agalactiae: meningitis, vaginitis [GBS], UTI, endocarditis, skin infection
•Enterococcus
–Anaerobic
–Can cause UTI, prostatitis, intra-abdominal infections, cellulitis, endocarditis
•Bacilli
–Lactobacilli -present in the mouth, vagina
–C. difficile
Name common gram negative organisms and the infectiosn they cause
•Escherichia coli
–Found in the intestines of humans and animals
–Responsible for food-borne illness and UTI
–Can also cause cholecystitis, traveler’s diarrhea and sepsis
•Pseudomonas aeruginosa
–Most common in hospitalized patients
–Can cause otitis externa, Pneumonia, wound infection, UTI, sepsis
•Klebsiella pneumoniae
–Colonizes the human mouth and gut
–Commonly causes Pnuemonia, UTI, sepsis
- Neisseria gonorrhoeae
- Haemophilus influenzae
–Pneumonia bronchitis, otitis media, cellulitis, infectious arthritis
What is the MOA of the penicillins?
Inhibit the biosynthesis of peptidoglycan bacterial cell wall (weakens cell wall)
-Bactericidal
Penicillin G Benzathine is active against what type of organisms?
Narrow spectrum antibiotic
- gram + mostly: S. pneumoniae, group A strep
- Pen G (IV) best for syphilis infection (T. pallidum)
Penicillin V is active against what type of organisms?
Narrow spectrum antibiotic
- best for group A beta-hemolytic strep
- strep throat/pharyngitis
What is Clavulanic acid?
A compound that inhibitis beta lactamase (made by bacteria to inactivate penicillin).
Used in Augmentin (amoxicillin/clavulanic acid) to increase spectrum of susecptible bacteria.
Amoxicillin and Augmentin (Amox/Clavulanic Acid) are active against what type of organisms?
More broad spectrum - Same gram + organisms as Pen V/Pen G but also some activity against gram - organisms
Amoxicillin - 1st line for AOM and sinusitis
Augmentin - 1st line fx for bites, UTI in pregnancy
Adverse drug reactions of penicillins
- serious allergic reaction
- Rash
- GI (N/V/D)
- Fungal overgrowth/candidiasis
Cephalosporin MOA
- Inhibit mucopeptide synthesis in the bacterial cell wall
- Bactericidal
How does spectrum of activity differ between classes of cephalosporins?
Earlier generations have good gram + coverage and less gram - coverage
Later generations have better gram - coverage and less gram + coverage
Cephalosporins Adverse Drug Reactions
- C. diff
- hypersensitivity rx
- hemolytic anemia
- neutropenia and leukopenia
- coagulation abnormalities
Cephalosporins cautions
- cross reactivity with history of penicillin allergy with anaphylaxis or hypersensitivity reaction
- safe in pregnancy/lactation and pediatrics
- The stronger the drug (5th generation is strongest; 1st generation is weakest) - the more chance of a C. Diff infection
What drugs are in the glycopeptide class?
Vancomycin and Lipoglycopeptides
Vancomycin MOA and indication
- Inhibits cell wall synthesis by binding to the D-A1a-D-A1a protein in the cell wall
- Bactericidal
- Not well absorbed orally, given IV except for C. diff
- Stays in the GI tract
- First line for C. diff. infection
Vancomycin (oral) Adverse Drug Reactions
- Ototoxicity
- Nephrotoxicity
- Red Man Syndrome
- Thrombocytopenia
Tetracyclines mechanism of action and indications
Tetracycline and Doxycycline
- Inhibit protein synthesis by reversibly binding to the 30S subunit of the bacterial ribosome
- Bacteriostatic
- Indications include mild to moderate respiratory infections, acne, Lyme disease, and chlamydia
Tetracyclines cautions and adverse drug reactions
- Preg Cat D -
- avoid in children < 8 years old due to teeth discoloring
- nephrotoxic
- photosensitivity
- hepatotoxicity
Tetracyclines patient teaching
Take with a full glass of water - do not take with milk or milk products (binds to calcium)
Can cause stomach upset/esophagitis
Wear sunscreen
Macrolides mechanism of action and indications
Azithromycin, Erythromycin, Clarithromycin
- Effective against gram + and gram - organisms
- Bacteriostatic (can be bactericidal at higher doses)
- Inhibits RNA-dependent protein synthesis by binding to the 50S subunit
1st line CAP
1st line pertussis
1st line chlamydia
Macrolides adverse drug reactions
- potent CYP450 inhibitor
- combination with statins may increase risk of myopathy
- skin rash urticaria, bullous eruptions, eczema, and Steven Johnsons syndrome
- GI distress (esp. E-mycin)
- QT prolongation (Azithromycin)
Lincosamides mechanism of action and indications
Clindamycin
- Gram + organisms
- inhibits protein synthesis by binding to the 50S subunit of bacterial ribosome
- bacteriostatic
- MRSA skin infections, dental infections, acne (topical)
High risk for C. Diff
Clindamycin patient education
- Call clinic if diarrhea occurs (high risk for C. diff infection)
Nitroimidazoles Mechanism of Action and Example
Metronidazole, Tinidazole
Disrupts electron transport of anaerobic bacteria
Indications: bacterial vaginosis, trichomoniasis - more for fungal, protozoan, parasitic infections - not as much bacterial
Nitroimidazoles Adverse Reactions
Seizures
Peripheral neuropathy
Metronidazole Mechanism of Action and Indications
Flagyl
- Interacts with DNA structure causing strand breakage, inhibition of protein synthesis, and cell death
- Bacteriostatic
- Broad spectrum (bacterial and parasitic)
Indications: C. diff, bacterial vaginosis, stool infections, trichomoniasis (think below the belt infections) - anaerobic, protozoans, fungals
Metronidazole Adverse Drug Reactions
- metallic taste
- dark urine
- hepatotoxicity
- superinfections (rare)
- disufiram like reaction with ETOH
- Black Box Warning: possibly carcinogenic
Metronidazole cautions/patient education
- do not use in the 1st trimester of pregnancy
- avoid alcohol during and for 2 days after tx (can cause disulfiram rx: N/V, H/A, flushing, dizziness, chest and abdominal discomfort)
Nitrofurantoin Mechanism of Action and Indications
- Multifactorial MOA
- Bacteriostatic in low concentrations, Bactericidal in higher concentrations
May inhibit acetyl coenzymes - interferes with bacterial protein synthesis, cell wall synthesis, and aerobic energy metabolism Indications:
Indication: uncomplicated UTI (1st line), not indicated in complicated infections or pyelonephritis
Nitrofurantoin Adverse Drug Reactions
- neuropathy
- pulmonary reactions
Fluoroquinolones Mechanism of Action and Indications
Ciprofloxacin, Levofloxacin
- Interferes with bacterial enzymes required for the synthesis of bacterial DNA
- Breakage of DNA strands
Indications: Complicated infections
- pyelonephritis (1st line)
- complicated UTIs
- CAP (3rd line)
Fluoroquinolones cautions/CIs
- Black box warning: risk of tendon rupture and tendonitis
- risk of QT prolongation
- seizures
- dizziness and confusion
- photosensitivity
- no children < 18 (unless pyelonephritis, anthrax, allergies to other meds)
- not for use in pregnancy and lactation
- high risk of superinfection (C. diff and candida)
- increasing resistance, do not use for minor uncomplicated infections
Sulfonamides/Trimethoprim Mechanism of Action and Indications
Sulfonamides block folic acid synthesis
- Trimethoprim inhibits DNA synthesis
- UTI
- Community acquired MRSA
- excellent gram negative coverage and coverage of stap/strep (gram +)
Sulfonamides/Trimethoprim Adverse Drug Reactions
- Hypersensitivity reactions: rash, fever, Stevens-Johnson syndrome (more common in HIV + patients)
- Not for use in pregnancy (anti-folate effects)
- Avoid in pediatrics < 2 months old
- Hyperkalemia (reduces K+ excretion)
- Avoid concomitant administration with K+ sparing drugs (triamterene, ACE, ARB)
MRSA skin and soft tissue infections
High risk in military, students, athletes, and inpatient populations
Mupirocin
Used topically to treat impetigo 3x/day for 5-14 days for up to 5 lesions
Cephalexin (oral) if there are 5 or more impetigo lesions
Oral medication options for skin lesions
- give if moderate to severe impetigo (5 or more lesions), boils, perianal strep, cellulitis cephalexin, bactrim (amox/clavulanate), dicloxacillin If MRSA skin infection is suspected: CBD (cephalexin, bactrim, doxycycline)
Carbapenums Mechanism of Action and Examples
Eg: Imipenem, meropenem, etrapenem, doripenem
Impair bacterial wall structure
Carbapenem Adverse Effects
Diarrhea, rash, seizure
Monobactams Mechanism of Action and Examples
Aztreonam
Interfers with bacterial cell wall
Monobactram adverse effects
Diarrhea, rash, anaphylaxis
Aminogylcosides Mechanism of Action and Examples
Gentamicin, Tobramycin, Amikacin
Inhibits bacterial DNA synthesis/replication
Aminogylcoside adverse effects
Nephrotoxic, ototoxic, neuromuscular blockade
Oxazolidinones Examples and Mechanism of Action
Linezolid, Tedizolid
Inhibits ribosomal proteins
Oxazolidinones Adverse Effects
Bone marrow suppression
Peripheral neuropathy
Optic neuropathy
Lactic acidosis
Lipopeptide Example and Mechanism of Action
Daptomycin
Accumulates in cell membrane of G+ organisms
Daptomycin Adverse Effects
Thrombocytopenia
Skeletal muscle toxicity
Polypeptides Mechanism of Action and Example
Colistin
Disrupts outer membrane of G- organisms
Polypeptides Adverse Effects
Nephrotoxicity
Reversible neurotoxicity
Rifamycins Mechanism of Action and Examples
Rifampin, rifabutin, rifaximin
Block RNA polymerase from interacting with DNA
Rifamycins Adverse Effects
Discoloration of body fluids
Hepatotoxicity
Drug-drug interactions
Antifungal (PO) Adverse Effects
QT prolongation
Torsades de pointes
