Question

A 68 year old women was admitted to a hospital because of headaches that began a month earlier. She was in good health, prior to developing severe headaches, vertigo, photophobia, lethargy, and forgetfulness. Her temperature was 98.9 degrees F, and she knew her name but not the date. She had some resistance to bending her neck, consistent with mild inflammation of the meninges. She also had past-pointing when reaching for objects. A lumbar puncture revealed a total white blood cell count of 18/microliter ( normal is up to 4) and 75% polymorphonuclear leukocytes. CSF glucose was low suggesting a microbe was present in the subarachnoid space. The lab tech performing the wbc count noticed cells that were not wbc. To investigate further, the tech centrifuged the CSF, and stained the sediment with India ink. The round cell appeared to be budding, much like yeasts. In addition, the cell appeared to have a capsule.

1. What type of microbe could be causing the meningitis? Give one reason to support your answer based on the information provided.

2. Of the following eukaryotic microbes, which one is characterized by having polysaccharide capsules? Candida albicans, Histoplasma capsulatum, Crytococcus neoformans.

In July of 2003 a construction worker came to a hospital in Palm Beach County complaining of fever, headaches, chills, nausea and malaise. After being treated for dehydration he was discharged. Two days later he returned to the hospital with worsening symptoms, and was admitted with a diagnosis of malaria. The next day his blood smear revealed Plasmodium. During July and August a plumber who worked outside, a fisherman who fished in the evenings, a golfer, a homeless individual, a carpenter and an outdoorsman all had Plasmodium infections. Six of the seven men had never traveled to a malarious region, none had had recent blood transfusions or was an IV drug user. Targeted mosquito trapping produced no Plasmodium-infected mosquitoes.

3. What could an epidemiologist infer from the interviews of the seven patients? What disease did all seven have?

4. How is this disease transmitted? How was it transmitted in this case?

Answer 1

• According to the information that is given, the disease is Fungal meningitis, as the signs of the disease include :
• Fever
• Headache
• Stiff neck
• Nausea and vomiting
• Photophobia (sensitivity to light)
• Altered mental status (confusion)
• Fungal meningitis is usually a rare disease and caused by fungus spreading through blood to the spinal cord. Although anyone can get fungal meningitis, people with weakened immune systems have a higher chance of contracting the infection.
• Fungal meningitis can develop after a fungus spreads through the bloodstream from somewhere else in the body to the brain or spinal cord or from an infection next to the brain or spinal cord.

1. It is given that the organism has a capsule, and round cell appearance like yeast. Of the various yeast that can cause fungal meningitis, the signs and appearance match with the organism Cryptococcus neoformans. This organism is an encapsulated yeast, which replicates by budding, and the same is given in the question. Under the microscope, the India ink stain is used for easy visualization of the capsule in cerebral spinal fluid. The particles of ink do not enter the capsule which surrounds the spherical yeast cell, resulting in a zone of clearance or "halo" around the cells.
2. Of the following organisms, the one which produces a characteristic polysaccharide capsule is Cryptococcus neoformans. Under host-relevant conditions such as low glucose, serum, 5% carbon dioxide, and low iron, among others, the cells produce thic characteristic polysaccharide capsule.

• Plasmodium is a genus of unicellular parasites, many of which usually cause malaria in their hosts. It is given that the construction worker was diagnosed with malaria, as there was Plasmodium in the blood smear.

3. It is given that all the men had Plasmodium infection. Usually it can be inferred that the disease produced by this organism is malaria. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. This disease is a mosquito-borne infectious disease affecting humans and other animals caused by parasitic protozoans belonging to the Plasmodium type. Symptoms can usually be seen ten to fifteen days after being bitten. Malaria infection develops via two phases: one that involves the liver (exoerythrocytic phase), and one that involves red blood cells, or erythrocytes (erythrocytic phase). In some cases, P. vivax sporozoites do not immediately develop into exoerythrocytic-phase merozoites, but instead, produce hypnozoites that remain dormant for periods ranging from several months (7–10 months is typical) to several years. After a period of dormancy, they reactivate and produce merozoites. It might have happened that the mosquito that bit the construction worker, bit the other en as well, and transmitted the infection.

4. The disease is caused by a mosquito bite, in this case also it looks like a case of mosquito bite. Malaria is rarely transmitted by blood transfusion or any other routes, and also it is given in the question that the patients did not have any blood transfusion.