Infectious diseases Flashcards
What are the macrolide antibiotics, and how do they exert their activity?
Azithromycin and clarithromycin are the modern macrolides. They are synthetic modifications of the original macrolide - erythromycin - which, ironically, was isolated origiannly from a bacterium that produces it. Macrolides work by binding to the eryhtromycin ribosom methylase (erm) region of the 50S subunit of the bacterial ribosome, inhibiting protein synthesis be preventing tRNA binding. Furthermore, macrolides exert an antiinflammatory effect by reducing the production of IL-8, TNF-alpha, and IL-1beta. Their benefits are seen primarily in the treatment of neutrophil heavy inflammatory diseases (e.g. neutrophilic asthma).
Name a bacteriocidal antibiotic and explain the concept.
Bacteriocidal antibiotics cause the death of a bacterium, don’t just inhibit its growth. For example, penicillins cause the disinhibition of cell wall lytic enzymes in sensitive organisms leading to cell wall lysis. Cf with anti-folate synthesis abx such as trimethoprim that lead to a failure to grow and reproduce, and are therefore considered bacteriostatic.
Tetracylcines (doxycycline, tigecycline, minocycline etc) work by doing what? And are they bacteriostatic or bacteriocidal?
Tetracyclines work by binding to the 30s prokaryotic ribosome in the ‘A’ binding position for tRNA. They do so in a reversible manner and so are considered bacteriostatic.
Fluoroquinolones - how do they work?
They work by inhibiting the activity of prokaryotic DNA gyrase - the enzyme responsible for the allowing DNA to coil into and out of superstructures to allow it to be transcribed.
Aminoglycocides - how do they work? What group of organisms is intrinsically resistant to this group?
Once transported actively into some bacterial cells, they bind to the 30S ribosomal subunit in a manner that is not reversible, and causes misreading of the mRNA transcript, effectively causing fram shifts. This leads to rapid bacteriocidal killing due to failure to produce any essential protiens. Anaerobes are intrinsically resistant to aminoglycosides. Interestingly, aminoglycosides are much less effective in low pH envirements like the lungs.
What is the cause of bowel damage in C. diff colitis?
C. diff exotoxin causing damage
What is first line treatment for C. auris at present?
Anidulafungin
What are the echinocandins?
Antifungal medications including caspofungin, micafungin and anidulafungin.
How do the echinocandins work?
Inhibit fungal cell well polysaccharide beta-1,3 glucan synthesis.
How do the azole antifungals work?
Inhibit C14-alpha sterol demtylase, which leads to the accumulation of sterol precursors and reduction to ergotseol.
Which CYP450 enzymes do the azoles inhibit?
CYPC219, CYP3A4, and CYPC29.
What size effects are associated with azole use?
QT prolongation (except for isavuconazole which shortens the QT interval), hepatotoxicity (espeicially with voriconazole).
What clasee of durg is amphotericin B? How does it work?
Polyene. bind to cell membrane ergosterol, forming artificial pores which permit potassium efflux and cell death.
What are the common adverse effects associated with amphotericin B use?
AKI uin 30% of cases. Can also cause heptatotoxicity.
What is 5-fluorocytosine?
Pyramidine analogue used to treat pathogenic yeasts. Indicated in combination with amphotericin B intravenously in the treatment of cryptococcal meningitis
Is Chlamydia normally symptomatic in females?
No
Does screening for Chlamydia reduced the incidence of PID?
Yes
Does negatvie CPE screening of a patient with previous CPE positive status allow them to avoid CPE isolation next hospital admission?
No
What treatment should be used for patients with dengue haemorrhagic fever?
Crystalloid, and if they need it, blood products. NSAIDs contraindicated. Steroids don’t do anything.
What is an important human bite wound microbe that doesn’t come up in other contexts?
E. corrodens (anaerobe) - senstivie to augmentin
