15. General Principles of Antibiotics Flashcards
Paul Ehrlich 1901
Magic bullet
Salvarsan for syphilis
Alexander Fleming 1928
penicillin
Howard Walter Florey and Ernst Boris Chain 1940
penicillin purification
Gerhard Domagk 1939
sulfamides
Antibiotic: (2)
- (old) Anti-infective compound produced by a microorganism.
- Also used to name synthesized chemical drugs
Define Spectrum: (2)
-range of pathogens that are affected by the antibiotic
Activity of a drug is defined by their spectrum: antibacterial, antiviral or antifungal
What germ do antibiotics affect? (3)
Bacteria Mycobacteria Rickettsia, etc
What germ do antivirals affect?
virus
What germ do antifungals affect?
fungi
What germ do antiparasitics affect?
parasites
BACTERICIDES:
are able to produce the destruction of the bacteria
BACTERIOSTATIC: (3)
inhibit bacterial replication (stop bacteria from growing), without eradicating the bacteria
- It is essential the action of the host defense mechanisms
- After discontinuing the antibiotic the microorganism can multiply again.
Common property to all antibiotics is the
selective toxicity
What is selective toxicity? (2)
- common property to all antibiotics
- the toxicity towards invading organisms is greater than the toxicity towards humans (host tissue)
Antimicrobial agents behave as ________ when they produce the death of the organisms responsible for infectious process
Eg: (3)
- BACTERICIDAL
- ex. B-lactams, quinolones, aminoglycosides
Antimicrobial agents behave as _______ when they inhibit bacterial growth and replication although the microorganism remains viable.
eg: (3)
Bacteriostatic
-ex. tetracyclins, macrolides, sulfonamides
How do bacteriostatic drugs work? (2)
inhibit bacterial growth and replication and then the host immune system eliminates the bacteria.
IF you discontinue the antibiotic the microorganism can recover and multiply again
To classify an antimicrobial as bactericide or bacteriostatic depends on: (4)
- Its mechanism of action
- the concentration achieved at its site of action
- inoculum size
- type of microorganism, etc
What are the two types if antibiotic treatment?
- empirical: without knowing the specific germ
- specific: chosen after identifying the germ and knowing the antibiogram
Bacterial strains can be… (3)
- susceptible
- intermediate
- resistant
Types of antibiogram techniques (2)
- diffusion
- dilution
Define MIC (2)
minimum inhibitory concentration.
lowest concentration of antibiotic capable of inhibiting the growth of 10 (5) bacteria in 1 ml of growth medium after 18- 24h of incubation.
Define MBC
minimum bactericidal concentration
lowest concentration that can destroy or kill 10 (5) bacteria in 1 ml of growth medium after 18-24 h of incubation.
The purpose of anti-infective therapeutics will be to achieve …
an antibiotic tissue concentration exceeding the MIC
Information obtained about the MIC of the germ, we will know whether a…
-bacterial strain is sensitive to one or more antibiotics and if it can be treated with standard doses of these antibiotics
If you find a resistant strain on an antibiogram it means…
unlikely a good therapeutic result even with the administration of higher doses
What is the pharmacokinetics / pharmacodynamics relation?
relationship between antibacterial activity and the concentration achieved at the site of action
According to the PK/PD there are 2 antibacterial drug categories:
- Concentration-dependent action antibiotic
- Time-dependent action antibiotic:
What is a Time-dependent action antibiotic?
concentration of the drugs in this group at the site of action has to exceed the MIC for at least half of the dosing interval
What is a Concentration-dependent action antibiotic?
The greatest bactericidal activity is obtained when reaching concentrations above the MIC at the site of action. The higher the concentration, the greater the bactericidal effect
What are the mechanisms of action for antibiotics? (5)
- Increased permeability of the cell membrane.
- Inhibition of cell wall synthesis.
- Altered DNA and RNA synthesis.
- Inhibition of protein synthesis (ribosome: 50S / 30S)
- Antimetabolites
What are the fundamental rules of antibiotics treatment?
- Treatment indications
- Choice of antibiotic
- Route of administration
- Duration of treatment
What are treatment indications for antibiotics? (2)
- FEVER (bacterial origin): do bacteriological study (isolate)
- Pathogen most likely involved by LOCATION
What are contraindications for antibiotic treatments? (3)
- Non-infectious fever
- Fever caused by no susceptible organisms
- Tend to recover spontaneously (viral infections)
When do you give antibiotics in dentistry? (3)
- Important local extension
- Systemic involvement
- High risk
What type of antibiotic treatment is used in dentistry?
empirical
When do you do empirical antibiotic treatment? (3)
- In seriously ill patients
- Impossibility to collect a culture
- Negative cultures in severe infection
Choice of antibiotic depends on.. (4)
Gram Stain
Serology
Culture
Antibiogram
IF a patient has an immune system deficiency what antibiotic do you use?
bactericidal
What are the routes of administration for antibiotics? (7)
- ORAL
- RECTAL
- INTRAVENOUS
- CONTINUOUS INFUSION
- INTRAMUSCULAR
- INTRATHECAL
- INHALED
Antiobiotic treatment duration is usually around…
7-10 days
Why do we use a combination of antibiotics? (3)
- Preventing resistance
- Synergistic effect
- Enlarge spectrum of action
Why does bacterial resistance occur with antibiotics prescribed? (4)
- Misuse of antibiotics
- Inadequate doses
- Duration of therapy (short or long)
- Use of broad spectrum antibiotics
Whats the mechanism of action for bacterial resistance? (3)
- Inactivation of the antibiotic
- Decreasing antibiotic permeability
- Modification of the target structure
Antibiotic prophylaxis in dentistry should occur in pateints with these conditions (6):
- Prior Endocarditis
- Prosthetic valve
- Congenital heart disease (Not repaired)
- Heart transplant
- Valve Disease (stenosis or regurgitation)
- Hypertrophic Cardiomyopathy
What procedures in dentistry need antibiotic prophylaxis? (7)
Bleeding procedures:
- gingival manipulation
- periapical manipulation
- alteration or oral mucosa
- extractions
- perio surgery
- implants
- endodontics
This bacteria is the most frequent cause of infective endocarditis after dental procedures:
streptococcus viridans
What drugs are given for dental prophylaxis if the patient is not allergic to penicillin? dosing? (2)
- Amoxicillin: 2 g oral, 1 hour before intervention.
- Ampicillin: 2 g i.m. or i.v 30 minutes before.
What drugs are given for dental prophylaxis if the patient is allergic to penicillin? dosing? (2)
- Clindamycin: 600mg oral 1hour before intervention.
- Macrolides: (clarithromycin 500mg o., azithromycin 500mg o….)
