Clinical Topics Conference: Chapter 9a, Clinical Microbiology and Virology

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  1. Influenza virus pneumonia
  2. Hepatitis C Infection
  3. Neonatal CMV
  4. Rabies
  5. Strep Pneumo Menningitis
    Case 1: Influenza virus pneumonia

    Clinical vignette 1

    A 10-year-old institutionalized female presented to her doctor in early March with a 5-day history of a fever, headache, nonproductive cough, nausea, and lack of energy. She also had severe myalgias and nasal congestion. On the day she presented to her physician, her mother became ill, having headache, fever, and myalgias. Physical examination showed a temperature of 39oC and an increased respiratory rate of 35/min. Rales were heard at the base of the right lung. Analysis of arterial blood gases showed mild hypoxemia and respiratory alkalosis. A chest radiograph revealed a right lower lobe infiltrate. An induced sputum sample was obtained and sent for routine bacterial and viral culture. The sputum Gram stain was unremarkable.

    She was admitted to the hospital and given supplemental oxygen and intravenous fluids. Oral erythromycin therapy was started. Over the next 4 days the patient improved steadily and culture results revealed growth of influenza type A.

    Discussion topics

    1. What antipyretic agent should not be used in this patient? Explain.

    2. What strategies are available to prevent infections with this virus? Why are changes made in this vaccine each year?

    References

    1. CDC flu vaccination recommendations for 1996.

    2. Anti-viral drugs for influenza.

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    Case 2: Hepatitis C Infection

    Clinical vignette 2

    A 60-year-old female came to the emergency room of a university hospital with complaints of increasing weakness. The patient had been seen previously by a physician in the hosital for assessment of liver cirrohosis secondary to Hepatitis C infection. The patient had a history of heroin addiction 40 years ago and had recieved several transfusions in 1976 during open heart surgery. She was first dagnosed with Hepatitis C infection in 1992 when an antibody test was positive. The antibody test was confirmed positive with an immunoblot assay. Recently a Hepatitis C RNA assay showed 5.5 X 106 viral equivalents per mL of plasma with a genotype of 1b

    The patient was evaluated for orthotopic liver transplantation and found to be an acceptable candidate.

    Table 1: Enzyme levels
    TestsReference
    Ranges    		Patients
    AST7-40 U/L76
    ALT7-56 U/L647
    ALK PHOS25-110 U/L187
    Total bilirubin0.2-1.0 mg/dL5.4
    Lipase140-280 U/L3,038
    Amylase20-110 U/L227

    Discussion topics

    1. Who is at risk for hepatitis C infection?

    2. What does a positive serologic test for hepatitis C indicate?

    3. What does a positive PCR for hepatitis C indicate?

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    Case 3: Neonatal CMV

    Clinical vignette 3

    The patient was a premature female of 28 weeks gestation born to an 18 year old G2, PO, TAb1 mother by Cesarean section following premature rupture of the placental membranes (PROM). The pregnancy had been uneventful up to PROM. There was no history of infection elicited from the mother. The infant died 12 hrs following delivery from intractable respiratory failure thought to be due to severe hyaline membrane disease. Premortem blood culture was negative, as were the TORCH titers of IgG antibodies: toxoplasmosis negative; rubella, 1:10; CMV, 1:16; Herpes virus, < 1:8.

    At autopsy, the liver showed intranuclear CMV inclusions in bile duct epithelial cells.

    Discussion topics

    1. Is there a treatment available for CMV in a normal host? in an immunocompromised host? Is a vaccine available?

    2. What possible explanations can you think of to explain the negative TORCH titer for CMV in this patient?

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    Case 4: Rabies

    Clinical vignette 4

    The patient was a 6-year-old child who came home crying, saying she had been bitten by a dog. She was taken to a local physician (in Mexico City). Several small wounds on the face were treated with an antiseptic and sutured. Anti-tetanus serum was administered. The dogbite was more or less forgotten until four weeks later, when the child became extremely irritable, with choking attacks. Subsequently she became so excitable that she was bound down to the bed with cold sheets. Her temperature reached 106 oF. Death occurred one week after onset of maniacal symptoms and 3 days after transfer to a general hospital in Mexico City. An autopsy was performed.

    During the autopsy, the prosector cut himself during the removal of the brain. He treated the cut with tincture of iodine. Only when the diagnosis of rabies was made from the autopsy slides about 3 weeks later was it recalled that the child had been bitten by a dog. The prosector was given the Pasteur treatment. He did not develop rabies.

    Discussion Topics

    1. According to the MMWR 40 (RR03):1-19, 1991 guidelines, what anti-rabies treatment, in addition to tetanus and antibiotics, should the autopsy prosector have received, and by extension, the little girl?

    2. What is the percent mortality in untreated rabies?

    3. What animals in the United States are most likely to transmit the disease? What animals in Central America are most likely to transmit the disease?

    4. How does the virus gain access to the CNS?

    References:

    1. Morbidity & Mortality Weekly Report 40: (RR3) 1-19, 1991. Rabies Prevention, 1991.

    2. MMWR 44 (RR02), 1996. Compendium of Animal Rabies, 1996

    3. Journal of the American Medical Association, vol. 284, #18, Nov. 12, 1982. Fatal encephalitis due to rabies, after treatment with human diploid cell vaccine, but not rabies immune globulin.

    4. JAMA Vol. 236, #24, Dec. 13, 1976. Successful protection of humans exposed to rabies. (Includes a description of the "Pasteur Treatment".)

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    Case 5: Bacterial meningitis

    Strep Pneumo Menuingitis 5A

    A 65-year-old male with a history of tuberculosis as a child was admitted to the hospital in a semi-comatose condition. During the past week, he developed fever, chills, headache and nausea.

    BP was 120/70 mm Hg; Temperature of 103o F; ptosis of the right eyelid; dilation of the right pupil; nuchal rigidity; and a positive Kernig's sign.

    Hematocrit 50%: WBC 14,500 with 56% PMNS, 24% bands, 15% lymphocytes; 3% monocytes and 2% eosinophils. The cerebrospinal fluid (lumbar tap) showed an opening pressure of 250 mm Hg, protein 100 MG%, 2500 PMNS and 250 Mononuclear cells/mm3.

    A gram-stained smear of the CSF showed numerous WBCs and lancet shaped, Gram-positive diplococci. Bacterial latex agglutination was performed and was psitive for strep pneumonial. Bacterial culture of ESF and blood yeilded Strep Pneumonial within 24hrs.

    Test
    Reference Ranges
    Patient A
    Patient B
    		Protein
    15-45 mg/dL
    1092 mg/dL
    913 mg/dL
    Glucose
    50-75 mg/dL
    <10 mg/dL
    <10 mg/dL
    WBC count
    0-5
    2,300/mL
    15,600/mL
    Neutrophils
    <5%
    90%
    98%

    Discussion topics

    1. On the basis of the Gram stain, latex agglutination test, and culture results what is the correct diagnosis?
    2. What were the probable routes of entry of microorganisms into the CSF?
    3. Were bacterial latex agglutination tests used appropriately in this case?
    4. What is the role of bacterial antigen detection tests in the diagnosis and treatment of meningitis?

    References

    1. Discussion: CSF Bacterial antigen testing

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