Case Study Exercise 1
EXAMPLE: Sarah, a 19-year-old female has a history of a urinary tract infection (UTI) 4 months prior to admission for which she was treated with oral ampicillin without complications. Five days prior to this admission, she began to note nausea without vomiting. One day later she developed left flank pain, fevers and chills, and increased urinary frequency. Sarah noted foul-smelling urine on the day prior to admission. She presents with a temperature of 101.8o F, and physical examination shows left costovertebral angle tenderness. Urinalysis of a clean-catch urine sample is notable for >50 white blood cells per high-power field, 3 to 10 erythrocytes per high-power field, and 3+ bacteria. Urine culture is subsequently positive for >100,000 CFU of a Gram negative, lactose-fermenting rod per ml; this bacterium was indole positive.
E1. What do the urinalysis findings indicate? Explain your answer. The bacterium responsible for the infection is the most common cause of UTIís: What is the pathogen?
E2. How do the biochemical reactions help in the diagnosis?
E3. Why are urinary tract infections more common in
women than in men? Did this woman have cystitis or
Why is it important to differentiate?
A. This 2-year-old child, Felix experienced an upper respiratory infection 2 weeks prior to hospital admission. Four days prior to admission, anorexia and lethargy were noted. The patient was seen in the emergency room three days prior to admission. At that time, Felix had a fever of 103.8o F. Physical examination revealed a clear chest, exudative pharyngitis, and bilaterally enlarged cervical lymph nodes. A throat culture was taken and a course of penicillin was begun. The childís condition worsened and he became increasingly lethargic; he developed respiratory distress the day of admission. It was noted that the throat culture from 3 days prior to admission had not grown any Group A Streptococci. On examination, Felix is febrile to 102o F and has an exudate in the posterior pharynx that is described as a yellowish thick membrane which bleeds when scraped and removed. The patientís medical history reveals that he had received no immunizations.
1. The patient is admitted to the hospital and treatment is begun. Special cultures of the pharynx were requested that subsequently grew the suspected pathogen. What was this pathogen? Explain how you know this.
2. Name a special stain used to find this organism and describe what you would see.
3. To cause disease, does this organism invade the bloodstream? If not, how does it cause disease?
4. Fully describe how can this disease be prevented.
B. A 30-year-old dairy farmer Ralph was in good health until the day prior to admission, when he felt chilled and feverish. He developed nausea, vomiting, diarrhea and lower abdominal discomfort; he presents to the emergency room, where he is noted to be lethargic. His vital signs include temperature of 104o F, blood pressure of 100/60 mmHg in the supine position and 80/60 mmHg sitting and a pulse of 80 beats/min. His physical examination is remarkable for lower abdominal tenderness to palpation bilaterally. A rectal examination reveals occult blood in the stool. Ralph is lethargic but has no focal neurological deficits. Of note, his 3-year-old son had been discharged from the hospital 2 days prior with a similar history. The patient underwent lumbar puncture because of his altered mental status and fever. Lab studies of the CSF are within normal limits and a bacterial culture of the CSF was negative. Ralph is treated with IV fluids and antibiotics, and his condition improves. A stool examination for fecal leukocytes was positive, and a stool culture was diagnostic. Biochemical examination of the microbe revealed it to be a lactose nonfermenter on MacConkey agar, H2S negative, urea negative, and nonmotile at both 77o F, and 98.6o F.
5. Based on the biochemical reactions, what genus is it?
6. Did Ralph have meningitis? Explain your answer.
7. How is dehydration in patients with diarrhea usually treated?
8. Why could the usual therapy not be used in this case?
9. Ralph's wife and child also had this
infection. Was this individualís vocation important in the
epidemiology of this infection in his family? Explain your
C. A college student Michael presents to his primary care physician with a sore throat, high fever and skin rash. On examination, his pharynx has a gray-white exudates and his distended abdomen results from an enlarged liver and spleen. Blood work demonstrates lymphocytes with abnormally large nuclei perforated with holes, a classic symptom of this condition.
10.What disease is Michael suffering from? (Explain what clues in the case history were important to your diagnosis.)
11. How did he likely contract it?
12. Name the etiologic agent.
the usual treatment and his prognosis.
D. Fred presents with a 3-year history of pain and itching of the toes of both feet and of his left palm and fingers. Small red lesions are visible on the left fingers. He is in good health and training for college athletic teams in baseball, volleyball and swimming. During the 3 years, Fred has been using his medication sporadically and has now returned to the clinic since the condition is no longer responding to the current medication. Direct examination of palm skin scrapings with calcofluor reveals septate, nonpigmented hyphae with some coiled. A PDA culture of scrapings from Fred's feet grew a white fungus with thin-walled macroconidia and numerous microconidia.
14. What is wrong with this patient?
15. How did he likely contract it?
16. To which group of organisms does this fungus belong and why is the group so named?
What is the usual treatment for this condition? Why
was it not working for Fred?
E. HIV-positive Stephen with a T-helper cell count of 60/ul presents with headaches, weakness and difficulty balancing when walking. His friend who brought him to the ER states that Stephen was very agitated over the last few days and his speech became slurred and ďrambling.Ē On physical examination Stephen is afebrile, but disoriented and unable to recognize his friend. Brain imaging reveals multiple ring-enhancing lesions containing oocytes of a sporozoan (apicomplexa) parasite.
18. What organism is causing Stephen's symptoms; explain your reasoning.
19. How did Stephen likely become infected and what is his prognosis?
What other groups of patients are at risk of serious
infection from this organism?