What underlying infection should a physician immediately suspect when confronted with a patient with confirmed cryptococcal meningoencephalitis caused by Cryptococcus neoformans, and why?
A. Influenza infection. The 2 viruses are often transmitted together in respiratory droplets.
B. HIV infection. People with normal immune systems generally fend off this fungal infection before it becomes clinically symptomatic.
C. Varicella zoster virus (chicken pox). During the incubation period for chicken pox, and during its latency, C. neoformans has an increased ability to colonize the respiratory tract.
D. Syphilis. This sexually-transmitted illness depletes CD4+ helper T cells that are necessary to directly attack the fungal infection of C. neoformans.
You're a famous eye surgeon, specializing in corneal transplants. Give your choice, would you rather have a cornea for transplantation from a 20 year old individual, or a 60 year old individual (assuming there are no optical defects due to age), and why?
A. The 60 year old-clearly, if the individual has gone 60 years with no optical defects, this is a very good organ for transplantation. The 20 year old cornea may have defects that simply haven't become apparent yet.
B. The 20 year old cornea-younger is always better when dealing with tissue transplants. You want to give the transplant the longest possible time for survival in the recipient.
C. The 20 year old cornea-while extremely rare, it may be possible to transmit prions through corneal transplants. It's less likely that a 20 year old would have encountered and become contaminated by prions than the 60 year old.
D. The 20 year old cornea-never mind prions, there are a variety of agents that can hide in corneal tissues and that might cause disease. It's far more likely that the 60 year old would be harboring one or more of these pathogens than the 20 year old.
Why would the Sabin oral polio vaccine need to be eliminated as we get closer and closer to eradication of the polio virus?
A. Since it is a live, attenuated viral vaccine, there's always the chance it could revert back into a pathogenic state by mutation. This would introduce new strains still capable of causing the illness into human populations, thwarting elimination.
B. The Sabin vaccine is cheaper than the Salk (killed virus) vaccine, but it isn't as effective at producing a protective response. We'll need to shift to the more effective Salk vaccine worldwide eventually to complete the eradication process.
C. The Salk vaccine is far cheaper than the Sabin vaccine. To effectively eradicate polio, we'll need to shift all of our resources into the cheapest and easiest to deliver vaccine possible. That is the Salk vaccine.
D. The Sabin vaccine can only be administered to human beings. We need to vaccinate bird populations as well to effectively control the spread of polio. Birds are a natural reservoir for the virus.
Why are such a high percentage of infant botulism cases associated with ingestion of honey?
A. Bees cultivate C. botulinum bacteria within their hives as a food source, so it gets mixed in with the honey.
B. The infant digestive tract is far more susceptible to the effects of botulism toxin (found in the honey in relatively high levels) than the adult digestive tract.
C. The spores of C. botulinum produce a strong endotoxin. This endotoxin has little effect on adults due to their overall size. Infants, however, are significantly smaller (and therefore far more susceptible) than adults.
D.
There can be endospores from C. botulinum in honey. They may germinate in the intestines of infants following consumption of honey, leading to colonization and pathogenesis as the bacteria begin forming botulism toxin. Adults' normal intestinal microbiota will out-compete the new microbes, but very young infants may not yet have this normal flora established.
Why can an infection in the brain's ventricles usually be detected in spinal fluid obtained from the lower back (lumbar region)?
A. Cerebrospinal fluid (CSF) originates in the ventricles, but percolates over and around the brain and spinal cord.
B. There is a high degree of vascularity that exists, allowing easy transfer of bacteria in the cerebrospinal fluid (CSF) and the blood.
C. There is a set of lymph nodes specifically in place to drain the cerebrospinal fluid (CSF) from the ventricles. They are housed in the lumbar region of the spinal column, adjacent to the spinal cord.
D. This is an incorrect statement. Since the central nervous system (CNS) is a protected site due to the blood-brain barrier, there can never BE an infection in the ventricles.
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