The patient was a 34-year old male who was first diagnosed with HIV infection 18 months previously. He presented with a 2-month history of increasing night sweats which "soak the sheets," severe fatigue, fevers, and chills.  He also was severely constipated, with no bowel movements in approximately 2 weeks. On physical examination, the patient was cachectic with a distended abdomen and an enlarged liver by palpation 5 cm below the costal margin. He was febrile to 40 degree centigrade and complained of fatigue, chills and abdominal pain. Admission laboratory tests were significant for a white blood cell (WBC) count 3,300/ micro liter with a CD4 count of 10/micro liter and a hemoglobin of 6.9g/dl. Other tests including blood gases, electrolytes, chemistries and urinalysis were normal. Enemas gave symptomatic relief of his constipation, while transfusion of 3 units of packed RBCs relieved his fatigue. Ova and parasite examination was negative. Blood and stool cultures were positive for the etiology of his current illness only after prolonged incubation (4weeks). An acid-fast pain of the organism infecting the patient is shown in Fig. 1. Despite therapy with 5 different agents, the patient's condition worsened over the next 6 months, and he died. 

1. What organisms showing the acid-fast characteristics seen in fig 1 can cause disseminated infection in HIV-infected patients? Which organism is most likely infecting this patient?

2. Explain the natural history pf infection in this patient. Include in your explanation the importance of his CD4 count, and explain the pathogenesis of his hepatomegaly and anemia. 

3. Why is it so important to notify the laboratory that this organism is being sought when blood is cultured from patients suspected of being infected with this organism?

4. How is the organism causing this infection usually spread? What infection control precautions should have been taken with this patient?

5. What other types of patient population can have clinical disease with this organism?