40 Questions
What is a major cause of preterm birth?
Infection
What is the purpose of prescribing antibiotics to women with preterm prelabour rupture of membranes?
To delay delivery and reduce the incidence of infection
What are the agents of first choice in pregnancy?
Penicillins and cephalosporins
What is the risk associated with using most antibiotics in pregnancy?
Increased risk of fetal malformation
What is the concept of selective toxicity?
Toxicity to the parasite or the unwanted cell but non-toxic to the host
What is the pivot of chemotherapy?
Selective toxicity
What is the reason why a drug can be highly toxic to microbes but harmless to the host?
Differences in the cellular chemistry of mammals and microbes
What are biochemical processes critical to microbial well-being that do not take place in mammalian cells?
Metabolic pathways
What is the main difference between antimicrobials and antineoplastic agents?
Antimicrobials act on microbes, while antineoplastic agents act on malignant cells.
What is the term for the ability of an antibiotic to inhibit the growth of bacteria?
Bacteriostatic
What is the characteristic of Gram-positive bacteria?
Thick cell wall with peptidoglycan directly accessible from the environment
Who is known as the 'Father of Chemotherapy'?
Paul Ehrlich
What is the term for the phenomenon of antibiosis?
Antibiosis
What is the term for the destruction or dissolution of bacterial cells?
Bacteriolytic
When was penicillin discovered?
1929
What is the term for antibiotics that are produced from microbes?
Antibiotics
What is one of the prophylactic applications of penicillin G?
Preventing syphilis in sexual partners of infected individuals
What is the route of elimination of penicillin from the body?
Kidney excretion
What is the main mechanism of renal excretion of penicillin?
Active tubular secretion
What is the half-life of penicillin in older children and adults?
About 30 minutes
What happens to the half-life of penicillin in patients with renal impairment?
It increases dramatically
Why was probenecid used concurrently with penicillin in the past?
To prolong antibacterial effects
What is the main difference between penicillin G and penicillin V?
Penicillin V is similar to penicillin G in most respects
When is monitoring of kidney function recommended for patients taking penicillin?
For patients at high risk of toxicity (those with renal impairment, the acutely ill, the very young, older adults)
What is an alternative to penicillins in patients with penicillin allergy?
Vancomycin
How many carbapenems are available?
Four
What is the mechanism of action of imipenem?
Weakening of the bacterial cell wall
Why is imipenem effective against anaerobic bacteria?
All of the above
How is imipenem administered?
Intravenously
What is the role of cilastatin in imipenem therapy?
It inhibits destruction of imipenem by renal enzymes
What happens to imipenem when it is employed alone?
It is inactivated by dipeptidase
What is the primary route of elimination of imipenem?
Renal
What is unique about vancomycin compared to other drugs discussed?
It does not contain a beta-lactam ring
What is vancomycin typically used to treat?
Serious infections caused by MRSA or Staph.epidermidis
Why is vancomycin used as an alternative to penicillins and cephalosporins?
Because patients are allergic to beta-lactam antibiotics
What is a common adverse effect of vancomycin infusion?
All of the above
Why is vancomycin administered slowly?
To reduce the risk of red man syndrome
What is red man syndrome?
A constellation of disturbing effects caused by rapid infusion of vancomycin
What can increase the risk of ototoxicity when using vancomycin?
All of the above
What is bacitracin used for?
Topical treatment of skin, eye, and ear infections
Study Notes
Infection and Pregnancy
- Infection is a major cause of preterm birth
- Antibiotic prophylaxis has not proven useful in preventing preterm birth, but prescribing antibiotics to women with preterm prelabour rupture of membranes can delay delivery and reduce the incidence of infection
- Penicillins and cephalosporins are generally considered the agents of first choice in pregnancy, as they are associated with lower risks of fetal malformation
Antimicrobials and Chemotherapy
- Selective toxicity is the pivot of chemotherapy, referring to the ability of a drug to be toxic to parasites or unwanted cells while leaving the host or environment relatively unharmed
- Chemotherapeutic agents act selectively against microbes or malignant cells, without affecting body cells
- Antimicrobials are used to treat infectious diseases, and can be classified into different types based on their chemical structure, mechanism, and spectrum
Mechanisms of Action
- Bacteriostatic agents stop the growth of bacteria
- Bactericidal agents kill bacteria
- Bacteriolytic agents cause the destruction or dissolution of bacterial cells
Gram Positive and Gram Negative Bacteria
- Gram positive bacteria have a thick cell wall and peptidoglycan directly accessible from the environment
- Gram negative bacteria have a thin cell wall, surrounded by inner and outer membranes, and are resistant to diffusion of antibiotics
Historical Perspectives
- Louis Pasteur discovered the phenomenon of antibiosis in 1877
- Paul Ehrlich coined the term "chemotherapy" in 1906 and is considered the father of chemotherapy
- Gerhard Domagk discovered sulfonamides in 1935
- Alexander Fleming, Ernst Chain, and Howard Florey discovered penicillin in 1929, 1939, and 1941
- Selman Waksman discovered streptomycin and coined the term "antibiotic" in 1944
Antimicrobial Classification
- Antimicrobials can be classified based on their chemical structure, mechanism, and spectrum
- Examples of antimicrobial classes include:
- Penicillins
- Cephalosporins
- Aminoglycosides
- Chloramphenicol
- Tetracyclines
- Macrolides
- Glycopeptides
- Rifamycins
- Nitroimidazoles
- Quinolones
- Trimethoprim
- Oxazolidinones
- Lipopeptides
Penicillin
- Penicillin is a bactericidal agent that inhibits bacterial cell wall synthesis
- Penicillin G has important prophylactic applications, including preventing syphilis and recurrent attacks of rheumatic fever
- Penicillin distributes well to most tissues and body fluids, but penetration into the meninges and into fluids of joints and the eyes is poor in the absence of inflammation
- Penicillin undergoes minimal metabolism and is eliminated by the kidneys, primarily as the unchanged drug
- Renal impairment can cause the half-life of penicillin to increase dramatically and may necessitate a reduction in dosage
Vancomycin
- Vancomycin is a bactericidal agent that inhibits bacterial cell wall synthesis
- Vancomycin should be reserved for serious infections, and is the drug of choice for infections caused by MRSA or Staph. epidermidis
- Vancomycin is also used to treat severe Clostridium difficile infections
- Common adverse effects of vancomycin include:
- Ototoxicity
- Red man syndrome (flushing, rash, pruritus, urticaria, tachycardia, and hypotension)
- Thrombophlebitis
- Nephrotoxicity
Carbapenems
- Carbapenems are beta-lactam antibiotics with a broad antimicrobial spectrum
- Examples of carbapenems include:
- Imipenem
- Meropenem
- Ertapenem
- Doripenem
- Carbapenems are active against most bacterial pathogens, including organisms resistant to other antibiotics
- Imipenem is supplied in fixed-dose combinations with cilastatin, which inhibits destruction of imipenem by renal enzymes
This quiz covers the use of antimicrobials in pregnancy, specifically the prescription of antibiotics to women with preterm prelabour rupture of membranes. Learn about the impact of infection on preterm birth and the role of antibiotics in delaying delivery.
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