Lec. 6: Antimicrobial Therapy Flashcards
Name the three major spectrums of antibiotics.
- Narrow
- Extended
- Broad
Name four extended spectrum antibiotics.
- Aminoglycosides
- Cephalosporins
- Imipenem
- Extended-spectrum penicillin
Name six broad spectrum antibiotics.
- Chloramphenicol
- Sulfonamides
- Tetracycline
- Trimethoprim
- Metronidazole
- Fluoroquinolones
Name seven narrow spectrum antibiotics.
- Penicillin G, V
- Erythromycin
- Clindamycin
- Vancomycin
- Polymixins
- Bacitracin
- Linezolid
What are the four main factors that affect antimicrobial therapy?
- Diagnosis of infecting organism
- Choice of antibiotic
- Local Factors
- Host Factors
What are the three categories associated with the choice of the antibiotic?
- Specificity and Spectrum
- Bacteriostatic vs. Bacteriocidal
- Concentration of antibiotic at the site of infection
Give five examples of local factors that affect antimicrobial therapy.
- Presence of pus
- Presence of Hb
- pH
- Anaerobic conditions
- Presence of foreign objects
Give seven examples of host factors that affect antimicrobial therapy.
- Integrity of host defense mechanism
- Age
- Renal and liver function
- Genetic factors
- Pregnancy, nursing
- Drug allergy
- Genetic factors
Both bactericidal and bacteriostatic agents rely upon ? to aid in eliminating the pathogen.
Host defenses
A good rule of thumb to go by when classifying antibiotics as bactericidal or bacteriostatic is that most ? drugs are bacteriostatic and must ? and ? drugs are bactericidal. Name the one exception.
- Broad Spectrum
- Narrow Spectrum
- Extended Spectrum
- Metronidazole is the exception. It is a broad spectrum drug, but is classified as a bactericidal antibiotic.
What are bactericidal antibiotic preferred (4 reasons)?
- Reduces the # of microorganism
- More rapid acting
- Produces irreversible damage
- Complete organism killing is required in some cases
Bactericidal antibiotics make it easier for the host defense to kill all bacteria by ?.
By reducing the # of microorganisms
Why do we want the bactericidal antibiotic to produce irreversible damage?
So you do not have to maintain MIC (minimum inhibitory concentration) for killing effect
Name three examples where bactericidal antibiotics complete organism killing is required.
- Bacterial endocarditis
- Meningitis
- Deficient or suppressed immune defenses (AIDS, chemo/transplant patients)
What are the four factors associated with the concentration of antibiotic at site of infection?
- Dosage and duration of therapy
- Route of administration
- Distribution, metabolism, excretion
- Patient compliance
Who is considered the father of chemotherapy, proposed the idea of drugs as “magic bullets,” and developed arsenic compounds for the treatment of spyhilis?
Paul Ehrlich
T or F. (1) Drugs can be found/developed that will specifically target the site of action on parasite. (2) These sites of action should be present in the organs and tissues of the host.
- True
2. False. These sites of action should NOT be present in the organs and tissues of the host.
Name eight sites of action for antibiotics.
- Cell wall synthesis
- Folic acid metabolism
- Cell membrane
- Protein synthesis (tRNA)
- DNA gyrase
- DNA-directed RNA polymerase
- Protein synthesis (50s inhibitors)
- Protein synthesis (30s inhibitors)
What six antibiotics act on cell wall synthesis?
- Penicillins
- Cephalosporins
- Monobactams
- Carbapenems
- Vancomycin
- Bacitracin
What two antibiotics act on folic acid metabolism?
- Trimethoprim
2. Sulfonamides
What antibiotic acts on the cell membrane?
Polymyxins
What antibiotic acts on the DNA gyrase?
Quinolones
What antibiotic acts on the DNA-driected RNA polymerase?
Rafampin
What six antibiotics act on protein synthesis by inhibiting the 30s subunit?
- Tetracycline
- Spectinomycin
- Streptomycin
- Gentamicin
- Amikacin
What five antibiotics act on protein synthesis by inhibiting the 50s subunit?
- Erythromycin
- Chloramphenical
- Clindamycin
- Streptogramins
- Oxazolidinones
What antibiotic acts on proteins synthesis by inhibiting tRNA?
Mupirocin
What type of drugs work together during combination chemotherapy and take less of the drug to kill all bugs?
Synergistic drugs
What type of drugs oppose each other and therefore take more of the drug to kill all bugs?
Antagonistic drugs
What are the three responses to combinations of drugs during combination chemotherapy?
- Indifferent
- Synergistic
- Antagonistic
What are five indications that combination chemotherapy would be appropriate for use?
- Treatment of MIXED bacterial infections
- Treatment of severe infections of UNKNOWN ETIOLOGY
- Enhancement of activity
- Prevent emergence of resistant organism
- Permit lower dose of one of the antibiotics (reduce toxicity)
How is the frequency of resistance of two drugs determined?
Multiply the individual frequencies of each drug.
Ex. 10e6 x 10e7 = 10e13
List four disadvantages of combination chemotherapy.
- NOT usually necessary
- Antagonism of therapy
- Increased toxicity
- Increased cost
Name three adverse effects seen when taking combination chemotherapy.
- Organ or tissue toxicity
- Drug allergies
- Superinfections
What are the two types of antibiotic resistance?
- Intrinsic
2. Acquired
T or F. Sub-lethal concentrations of antibiotics favor the elimination of resistant microorganisms.
False. Sub-lethal concentrations of antibiotics favor the development of resistant microorganisms.
What type of resistance occurs as a result of stable alterations in the genetic composition of bacterial cell, is a consequence of antibiotic therapy through selection of resistance organisms, and is NOT necessarily caused by the antibiotic.
Acquired resistance
***What are five mechanisms of drug resistance?
- Alteration in receptors for drug!
- Decreased transport of drug across cell wall
- Inactivation of drug
- Alternative and salvage metabolic pathways
- Defect in drug metabolism or activation
Name three indications for prophylactic use of antibiotics.
- Prevent infection by specific organism
- Prevent bacterial endocarditis or recurrence of rheumatic fever
- Patients with compromised host defense mechanisms
T or F. Prophylactic use of antibiotics should not be used to prevent all potential secondary infections in patients ill with other disease.
True.
What are three examples of patients that are at risk of bacterial endocarditis?
- Prosthetic heart valves
- Mitral valve prolapse with mitral regurgitation
- Previous bacterial endocarditis
What is prophylaxis?
It is action taken to prevent disease.
T or F. Prophylaxis should be given to at risk patients concerning dental procedures that induce gingival bleeding (cleaning) and oral surgery procedures involving the teeth and gums.
True
What are five situations of antibiotics being misused?
- Treatment of insensitive infections (viral infections)
- Treatment of fever with undetermined origin
- Treatment without adequate bacteriological data
- Un- or mis-diagnosed etiologic agent
- Improper dosage
What are five examples where antibiotics might fail to succeed?
- Inability to penetrate to site of infection
- Resistant organism
- Superinfections
- Drug reactions
- Competing treatment modalities (hemodialysis)
There are many characteristics of an ideal dental antibiotic. List twelve.
- Bactericidal
- Acid stable
- Well absorbed orally
- No bacterial resistance
- Narrowest antibacterial spectrum possible
- Good antibacterial activity against usual organisms of dental infections
- Good distribution to bones as well as soft tissues
- No effect on food absorption
- High tissue concentration; above MLC
- Long half-life
- Readily excreted
- Ameliorates the infections in at least 5-7 days
Narrow spectrum drugs are usually good against gram-? cocci, and not good against gram-? cocci.
- Gram-positive
2. Gram-negative
