Chapter 38, 39, 40 (Learning Outcomes) Flashcards
What is a narrow-spectrum antibacterial drug effective against?
Effective against only a few specific bacteria
What is a broad-spectrum antibacterial drug effective against?
Effective against many types of bacteria
What are three examples of bacteriostatic drugs?
- Sulfonamides
- Erythromycin
- Tetracyclines
Define selective toxicity
The ability to suppress or kill an infecting microbe without injury to the host
What are the two ways that drug-resistant microbes develop?
- Spontaneous mutation
2. Conjugation (transfer of genetic material)
What are the classifications by mechanism of action for antimicrobial drugs (6)?
- Inhibition of bacterial cell wall synthesis
- Inhibition of protein synthesis
- Inhibition of nucleic acid synthesis
- Inhibition of metabolic pathway
- Disruption of cell wall permeability
- Inhibition of viral enzymes
How do some antimicrobial affect the cell wall synthesis of certain microbes?
Drugs weaken the cell wall, allowing the cell to absorb water and rupture
= leads to cell death (lysis)
How do some antimicrobial affect the protein synthesis of certain microbes?
Drugs disrupt the bacteria protein synthesis process
- without affecting the protein synthesis in human cells
How do some antimicrobial affect the metabolic pathways of certain microbes?
Nucleic acid synthesis requires folic acid
- microbes must synthesize it
- drugs can act to inhibit folic acid synthesis
How do some antimicrobial affect the cell wall permeability of certain microbes?
Drugs that disrupt the integrity of the bacterial cell wall
- cause the cell to leak the components that are vital to its survival
What is a nosocomial infection?
An infection that originates or occurs in a hospital (or hospital like setting)
What are the 7 considerations for selecting antimicrobial therapy?
- Identification of the pathogen
- Drug susceptibility
- Drug spectrum
- Drug dose
- Time to affect the pathogen
- Site of infection
- Patient assessment
Define empiric therapy
Prescribing antibiotic treatment before the pathogen has been definitely indentified
What is the most common test to identify drug susceptibility?
Culture and sensitivity
What is the course of action if multiple microbes are though to be the causative agent?
A culture specimen of the infected area should be taken BEFORE treatment
- antimicrobials might make identification difficult
What does the culture determine? What does the sensitivity determine?
Culture = determines the identity of the microbe Sensitivity = determines which antimicrobial agent will be therapeutic
Why is it important to choose a drug with the narrowest possible spectrum?
The benefit of a narrow-spectrum antimicrobial agent is that it limits the potential for adverse effects
- such as a superinfection
What is a superinfection?
An infection that occurs during the course of treatment for a primary infection
- ex: antibiotics keep in check ALL microbes (even the good ones) - could give an opportunistic resistant microbe the chance to multiply
What are two possible consequences of NOT using narrow-spectrum antibiotics?
- Secondary infections
2. Development of drug-resistant microbes
When should antibiotics be used prophylactically (5)?
- Exposure to sexually transmitted diseases
- Recurrent UTIs
- Neutropenia (low levels of neutrophils)
- Surgery (GI)
- Bacterial endocarditis (bacteria in the heart)
True or False:
Prophylactic use of antibiotics may contribute to the development of resistant organisms
True
Why is it important to educate patients on taking the FULL dose and duration of an antibiotic treatment?
Stopping therapy early may result in reinfection with the same pathogen
- pathogen will probably have become more drug resistant as a result of inadequate treatment
True or False:
Immunocompromised patients should receive drugs that are quickly bacteriostatic because of patients’ immune responses are limited
False
- they should receive bacterioCIDAL drugs b/c their immune systems are compromised
What body systems must be taken into account when administering antibiotics?
- Liver
- Kidneys
- patient might have difficulty metabolizing or excreting the drug
What adjustment should be made when prescribing an antibiotic to an elderly patient?
Lowering the dose
- minimize the risk for toxicity
Why are nosocomial infections so difficult to treat (3)?
- high prevalence of pathogens
- high prevalence of compromised hosts
- efficient mechanism of transmission
What is the minimum inhibitory concentration (MIC)?
The minimum concentration of an antibiotic that completely suppresses bacterial growth
What is the minimum bactericidal concentration (MBC)?
Concentration of an antibiotic that kills 99.9% of the initial inoculum in a broth dilution
What is the most important element of patient education regarding antibiotics?
Take the entire course of therapy
- taking the prescribe dose at the prescribed intervals
What is the prototype drug for the penicillin drugs?
Penicillin G
- narrow spectrum
What are the different classifications of penicillin (4)?
- Narrow-spectrum penicillin
- Aminopenicillin
- Extended-spectrum penicillin
- Penicillinase-resistant penicillian
What do beta-lactamases do?
Enzymes that disrupt the beta-lactam ring
- inactivates beta-lactam drugs
What should you recommend to your patient if they are allergic to penicillin?
Suggest that they never take an “cillin” drug
- they might be allergic to it as well
What are the two broad-spectrum aminopenicillins?
- Ampicillin
2. Amoxicillin
What are the two extended-spectrum penicillins?
- Piperacillin
2. Ticarcillin
How are aminopenicillins different than penicillins?
Effective against gram-negative microorganisms
Why can resistance to beta-lactams (such as penicillin) occur?
Because of the bacteria’s ability to produce beta-lactamase
Describe the pharmacodynamics of beta-lactamase inhibitors
On their own, they exhibit only weak antibacterial effects
- when combined with other penicillins they are much more effective
- Beta-lactamase inhibitors bind to the enzymes’ active site allowing the penicillin to reach the target site
How many generations of cephalosporins are there?
4
What is important to know about 1st generation cephalosporins?
- Most active against gram-positive bacteria (esp. staphylococci and nonenterococcal)
- Most are destroyed by beta-lactamases and minimal ability to concentrate in CSF
What is important to know about 2nd generation cephalosporins?
- Less sensitive to destruction by Beta-lactamases than 1st gen
- Still cannot achieve effective concentration in CSF
- Has broader coverage against gram-negative bacteria
- Can penetrate gram(-) cell wall better
What is important to know about 3rd generation cephalosporins?
- Drugs are highly resistant to destruction by beta-lactamases
- highly effective against gram(-) aerobes
- used for severe infections or in immunocompromised patients
What is important to know about 4th generation cephalosporins?
- active against (-) and (+) bacteria
- Greater spectrum than 3rd generation
- Highly resistant to destruction by beta-lactamases
What is cefazolin (cephalosporin) used to treat?
Many kinds of infections:
- skin
- bone
- heart
- respiratory
- GI
- sinus/ear
- urinary
What is important to know about cephalosporins and penicillins?
Because of structural similarities …
- patients who are allergic to one, typically are allergic to the other
Why should cefazolin be used cautiously in elderly patient?
In case they have a renal insufficiency
Why is the use of Vancomycin limited?
B/c of its ability to produce toxic effects
- therefore, it is only used when other antibiotics fail
What is VRE
Vancomycin-resistant enterococci (VRE)
What is vancomycin used to treat?
- bacterial septicemia
- endocarditis
- bone and joint infections
- pseudomembranous colitic caused by C. difficile
What antibiotic can be used if a patient is allergic to penicillin?
Vancomycin
- exceptionally effective for treating gram (+)
True or False:
Gram-negative bacteria and mycobacteria are resistant to Vancomycin
True
What are adverse effects of taking Vancomycin (6)?
- Ototoxicity (hearing loss, tinnitus, vertigo, nausea)
- Nephrotoxicity
- Anaphylactic reactions (due to histamine release)
- Phlebitis
- Leukopenia
- Thrombocytopenia
When can ototoxicity occur with Vancomycin?
When it is infused too quickly through IV
- serum concentration > 60 - 80 mcg/mL
What are penicillin drugs also known as?
Beta-lactam antibiotics
How can penicillin be inactivated?
By beta-lactamases (an enzyme produced by the bacteria)
What are penicillins most effective against?
Gram-positive bacteria
- they have difficult penetrating the gram-negative cell envelope
Process of protein synthesis is divided into what two sections?
- Transcription
2. Translation
Where does transcription occur?
Nucleus
Where does translation occur?
Cytoplasm
What do aminoglycoside agents do?
Affect protein synthesis
What are serious adverse effects of aminoglycosides (4)?
- Ototoxicity
- Nephrotoxicity
- Neurotoxicity
- Neuromuscular blockade
What is the prototype drug for aminoglycosides?
Gentamicin (Garamycin)
What is Gentamicin used for?
Serious infections:
- UTIs
- pyelonephritis
- gynecologic infections
- peritonitis
- endocarditis
- pneumonia
- bacteremia
- sepsis
What is Gentamicin effective against?
Gram-negative bacilli
What is ototoxicity?
Being toxic to the ear
What is the most common Gentamicin-induced nephrotoxicity?
Acute tubular necrosis
If using Gentamicin, what can the neuromuscular blockade, result in?
Respiratory depression
What is monitored throughout the course of Gentamicin therapy? Why?
Peak and trough drug levels
- because the therapeutic margin is very narrow
For Gentamicin therapy when is blood drawn to measure peak levels?
30 minutes after the completion of a 30 minute IV administration
OR
Immediately after a 60 minute IV administration
OR
45 - 60 minutes after an IM injection
For Gentamicin therapy, when is blood drawn to measure trough levels?
Just before the next dose
What are the common adverse effects of Gentamicin?
- nausea
- vomiting
- diarrhea
- weight loss
What is the prototype drug for lincosamides?
Clindamycin (Cleocin)
What is clindamycin active against?
A wide range of aerobic gram-positive cocci and several anaerobic gram-negative and gram-positive organisms
What is clindamycin used to treat?
- Skin and skin structure infections
- Respiratory tract infections
- Septicemia
- Intra-abdominal infections
- Osteomyelitis
Why are Lincosamides rarely used?
They are very toxic drugs
What is the most serious adverse effect of Clindamycin?
Clostridium difficile colitis (psudomembranous colitis)
- diarrhea, abdominal cramps, abdominal tenderness
What are common adverse effects of Clindamycin
- nausea
- vomiting
- abdominal pain
- rash
- pruitus
What is erythromycin used for?
Treating Legionnaire’s disease
What do tetracyclines affect?
Positive and negative bacteria
Why is tetracycline not used as frequently as it once was?
It has acquired substantial resistance patterns
What is the most serious adverse effect of tetracycline?
Azotemia - abnormally high nitrogen levels in the blood Also: - anaphylaxis - angioedema - blood dyscrasias - damage to the teeth - hepatotoxicity - nephrotoxicity
What are common adverse effects of Tetracycline?
- discoloration of teeth
- nausea
- vomiting
- photosensitivity
What is tetracycline used for?
- Rickettsia
- Mycoplasma pneumonia
- Chlamydia
- Acne
True or False:
Drugs that inhibit protein synthesis may be bactericidal or bacteriostatic
True
When assessing a patient prior to administering an initial dose of IV penicillin, you should …?
Examine the patient’s skin for any rashes or lesions
- to provide a baseline to avoid the misdiagnosis of an allergic reaction
Immunocompromised patients should receive antimicrobials that are …?
Fact-acting bacteriocidals
Prior to the initiation of long-term clindamycin therapy, what would you assess for?
A baseline CBC (complete blood count)
What are the populations most vulnerable to drug toxicity?
- Infants
2. Elderly
What is the nosocomial transmission of MRSA predominately attributable to?
The non-adherence to aspectic guidelines by healthcare providers
Vancomycin would be the antimicrobial agent of choice when treating …?
Bacterial septicemia
What is an adverse effect of aminoglycoside therapy?
Neuromuscular blockade
True or False:
Tetracyclines are use to treat bacteria that are both gram (-) and gram (+)
True
Describe the pharmacodynamics of penicillin
Changes the osmotic pressure of the bacterial cell
What does a hypersenitivity to Cefazolin most frequently present with?
A maculopapular rash that develops several days after the onset of therapy
