Scenario
Seventeen-year-old Brian has suffered with nonstop headaches for as long as he can remember. When he was 14, he was diagnosed with Lyme disease and treated, and although many symptoms improved, his headaches and overall fatigue did not. When his headaches worsened, he was sent for an extensive battery of blood tests.
Signs and Symptoms
When asked about other symptoms, Brian described a constant ringing in his ears and frequent red eyes that sometimes caused vision problems.
Despite his ongoing physical problems, until recently he had been able to maintain high grades in school (although there were times when he needed to be tutored at home) and had achieved Eagle Scout status.
Testing
Blood smears were prepared and stained with Wright-Giemsa stain for a "differential" count of different types of white blood cells. The technologist who viewed the slide noted several purple-stained, crescent-shaped objects that appeared to be cells with a nucleus.
(Q7) Diagnosis
Brian was diagnosed with toxoplasmosis, based on the observation of the tachyzoite life stage of Toxoplasma gondii in his blood. Although Brian also tested positive for Borrelia burgdorferi, it couldn't be determined from the serological report if he still had Lyme disease, due to limitations in the testing methods.
How do the flagella of a spirochete such as B. burgdorferi differ from those of a typical bacillus such as Escherichia coli?
(Q008) Treatment
Because it could not be determined how long Brian had been infected with Toxoplasma, the decision was made to use a treatment of pyrimethamine combined with sulfadiazine for six weeks. He was also given folinic acid (similar to folic acid, a B vitamin) to protect his bone marrow from toxic side effects. After 6 weeks, many of his symptoms had improved.
Why would an antibiotic like amoxicillin be ineffective as a treatment for toxoplasmosis?
(Q9) Sulfadiazine is a sulfonamide antibiotic that interferes with the ability of bacteria and some protozoa to synthesize folic acid, an essential component needed for DNA synthesis. Discuss what specific effects sulfadiazine would have on treated cells.
(Q10) If the positive blood test for Lyme disease indicated an ongoing infection with the spirochete B. burgdorferi, how might the prescribed treatment with sulfadiazine affect the bacterial cells?
(Q11) Additional Considerations
The Human Microbiome Project (HMP) suggests that the human body is actually a composite of both bacterial and human cells, with bacterial cells in the majority.
The endosymbiont theory of eukaryotic organelles suggests that mitochondria are "former" bacteria. These organelles have distinct genomes and ribosomes that map to present-day bacterial species known to be an obligate intracellular parasite.
Consider and discuss the biological effects that routine use of antibiotics may have on human physiology.
