TI 5 Clinical uses of antibiotics Flashcards
How do Gram-positive and Gram-negative bacterial cell walls differ in their structure and staining properties?
Answer: Gram-positive bacteria have a thick peptidoglycan cell wall that retains the crystal violet stain, appearing blue or purple under a microscope (e.g., Staphylococcus aureus). Gram-negative bacteria have a thin peptidoglycan layer and do not retain the crystal violet stain; they counterstain pink or red (e.g., E. coli).
Why aren’t “atypical” bacteria like Mycobacterium tuberculosis detected by a Gram stain?
Atypical bacteria do not have the typical cell wall structures that allow Gram stains to penetrate. For example, Mycobacterium tuberculosis has a waxy, lipid-rich cell wall, making it resistant to the Gram staining process.
What is the difference between broad-spectrum and narrow-spectrum antibacterials? Provide examples.
Broad-spectrum antibacterials act against a wide range of bacteria, including both Gram-positive and Gram-negative organisms (e.g., Tazocin). Narrow-spectrum antibacterials target a narrower range of bacteria, usually either Gram-positive or Gram-negative (e.g., Metronidazole).
Why should broad-spectrum antibiotics be used sparingly in antimicrobial stewardship
Overuse of broad-spectrum antibiotics can lead to the selection of resistant microbes and harm the patient’s gut microbiota, increasing the risk of opportunistic infections such as C. difficile and potentially contributing to the development of inflammatory bowel disease.
What are the steps involved in directed antimicrobial therapy after performing microscopy, culture, and sensitivity (MC&S) tests?
Directed therapy involves a stepwise provision of information:
Culture positive (something is growing).
Identification (we know what it is).
Sensitivities (we know what to treat it with).
What are the pros of using directed therapy for bacterial infections?
Directed therapy allows for:
Accurate identification of the causative organism.
Knowledge about resistance patterns.
Targeted antibiotic treatment.
The use of narrower-spectrum agents, reducing the risk of side effects and nosocomial infections.
what are the cons of using directed therapy for bacterial infections
he possibility of contamination or colonization leading to incorrect treatment.
Not all organisms may grow in culture.
Some tests may take time, delaying treatment.
What are the advantages of empirical therapy in treating infections?
Empirical therapy allows for:
Rapid initiation of treatment.
High efficacy in most cases based on probability and evidence.
Quick action in severe cases like sepsis, where time is critical.
What are the disadvantages of empirical therapy in treating infections?
Disadvantages include:
Risk of incorrect treatment if the pathogen is misidentified.
Use of broader-spectrum antibiotics, increasing side effects and the risk of nosocomial infections.
Potential failure to isolate the causative organism if antibiotics are given before samples are taken.
Why is rapid antibiotic administration critical in septic shock, and what is the “Golden Hour”?
For every hour’s delay in administering antibiotics in septic shock, mortality increases by 7.6%. The “Golden Hour” emphasizes the importance of administering antibiotics as soon as possible to reduce mortality.
What percentage of infective endocarditis cases are caused by Gram-positive organisms, and what is the mortality rate?
80-90% of infective endocarditis cases are caused by Gram-positive organisms, primarily staphylococci, with a mortality rate of 20-40%.
Why is infective endocarditis difficult to eradicate, and what is the recommended approach to treatment?
Eradication is difficult due to the poor vascularization of the endocardium, the bacteria being buried in platelets and fibrin in vegetations, and the slow-growing nature of the pathogens. Empirical treatment should be started promptly, followed by targeted therapy within 24-48 hours based on blood culture results.
What is an ESBL, and why is it significant in the treatment of bacterial infections?
Extended-spectrum beta-lactamases (ESBLs) are enzymes produced by bacteria that break down a wide range of beta-lactam antibiotics, including penicillins and cephalosporins, making infections difficult to treat.
Why should Nitrofurantoin be used cautiously in patients with renal impairment?
Nitrofurantoin’s efficacy depends on renal secretion into the urinary tract, and in patients with renal impairment, this secretion is reduced, decreasing its effectiveness and increasing the risk of side effects such as peripheral neuropathy.
Why is monitoring important for patients on long-term Nitrofurantoin therapy, especially the elderly?
Long-term Nitrofurantoin therapy can cause adverse pulmonary and hepatic reactions, so liver function and pulmonary symptoms must be closely monitored, especially in elderly patients.
