Module 9 Flashcards
Why is prontosil active in vivo but inactive in killing bacteria in a test tube? Who was the first patient Domagk treated with prontosil?
The active agent is sulfanilamide, which is formed by the reduction of the azo group of prontosil to form diaminopyridine and sulfanilamide. Most of this reduction is mediated by bacteria in the gut
Otitis media should always be treated with antibiotics?
False
most otitis has a viral origin, and obviously an antibiotic would not be effective in a viral infection.
○ Even when it is bacterial, otitis media usually resolves on its own. It has been shown that watchful waiting does not increase the risk of complications. It is likely that frequent use of antibiotics leads to a change in the normal bacterial flora and increases the risk of subsequent infections, although this is difficult to demonstrate.
Cranberry juice decreases the risk of urinary tract infections.
○ This appears to be a myth. In the first place, the rationale is that cranberry juice contains proanthocyanidin, which binds to fimbriae on E. Coli and prevents them from sticking to the bladder wall, which would result in the bacteria being flushed out of the bladder.
○ However, only about 1/3 of E. Coli have such fimbriae; therefore, one would expect that it would just select for the E. Coli that did not have fimbriae.
○ More important, there is no evidence that the proanthocyanidin is absorbed from the gut and excreted in urine. In fact, these are polyphenol molecules, and in general such molecules have poor oral bioavailability and are not extensively excreted intact in the urine.
Is it safe to eat steaks cooked medium/rare?
○ It should be, but it depends.
○ Poultry can harbor salmonella, which is present throughout the flesh; therefore it should be thoroughly cooked.
○ In contrast, if beef is contaminated with E. Coli, it is only on the surface; therefore, it should be safe to eat as long as the surface is cooked.
Why might treatment of an E. Coli 0157 infection with antibiotics be a bad idea?
○ Antibiotics increase the production of toxin by 0157, and it is the toxin that causes the morbidity and mortality associated with this infection. Some antibiotics appear to induce toxin production more than others, but there are clear dangers in using antibiotics to treat E. Coli 0157.
What appears to be an effective alternative to antibiotics to treat C. difficile?
○ fecal transplants.
○ C. difficile does not compete well with other gut flora, and that is why the use of antibiotics markedly increases the risk of C. difficile infections.
○ The transplantation of fecal bacteria from healthy donors appears to be more effective in the long run than antibiotics, especially for recurrent infections. However, antibiotics are usually required to treat a serious acute C. difficile infection
The microbiology susceptibility profile for a blood culture growing Enterococcus faecalis indicates that the organism is susceptible to trimethoprim-sulfamethoxazole. The physician wants to prescribe this combination to treat the patient’s bloodstream infection. As the pharmacist on service what do you advise?
○ In vitro susceptibility does not always indicate that the antibiotic will be effective.
○ You have to know whether the antibiotic will get to the bug, and you have to know the mechanism of action of the agent and whether there are mechanisms of resistance in vivo
○ In the case of sulfamethoxazole-trimethoprim, the sulfonamide prevents the synthesis of folate, and the trimethoprim prevents the folate from being reduced to its active form. But in vivo the bacteria may be able to use folate in the blood stream and bypass the block in folate synthesis. Folate does not penetrate bacteria very well, and even more effective in bypassing the mechanism of action is in puss in which there are a lot of dead cells that release thymine, and the synthesis of thymine is the most important function of folate.
The susceptibility profile for an anaerobic brain abscess shows that the organism is most sensitive to clindamycin. Does that make it the drug of choice to treat this infection?
○ Clindamycin has very poor brain penetration, and therefore is not effective for CNS infections.
Treatment with antibiotics before the age of 2 increases the risk of obesity
○ Maybe
○ A study found that more than 3 courses of antibiotics before the age of 2 is associated with an increase risk of obesity at age 4. It is plausible that antibiotic treatment could change the microbiome, and this could lead to obesity. However, there are several caveats with this study.
Association does not prove causation, although it would be virtually impossible to perform a prospective controlled trial.
This is only one study. I rarely trust the results of one study, especially this type of study.
The odds ratio was only 1.4. Most children still did not develop obesity.
The association was with obesity at age 4; does the risk persist?
This is from one geographic region (Northern Ireland, Wales, Scotland, England) and it may not represent other populations.
