Chloe Smith is a 10-year-old white female with cystic fibrosis. Cystic fibrosis

Question

Chloe Smith is a 10-year-old white female with cystic fibrosis. Cystic fibrosis (CF) is an autosomal recessive inherited disease. To contract the disease, a child must receive a defective gene from each parent. If both parents are carriers, the child has a 1 in 4, or 25%, chance of developing cystic fibrosis and having two copies of the defective gene; a 25% chance of being unaffected by the disease and having no copies of the defective gene; and a 2 in 4, or 50%, chance of being unaffected but carrying one copy of the defective gene. Cystic fibrosis affects multiple organs. The most common presenting symptoms involve the respiratory and gastrointestinal systems. Typical features include mucus plugging, chronic inflammation, and infection. Symptoms include persistent cough or wheezing and recurrent pneumonia. Respiratory failure is the most common cause of death.

Chloe has been admitted to Parkside Hospital. For the past two weeks, she has been experiencing a dry cough with no production of sputum (mucus expelled from the lungs by coughing). On the day of admission, she is intermittently febrile (feverish), complains of chest pain, and is producing small amounts of thick sputum. Chloe also complains of a stomachache and refuses to eat. Upon admission, she is turned over to Dr. Turner, chief pulmonologist for the Parkside Cystic Fibrosis Center. In reviewing Chloes history, Dr. Turner notes that Chloes last hospitalization occurred 3 years ago. She has been evaluated regularly and has not had any weight loss. Her lung function tests had been stable up to 2 weeks prior to her admission but have worsened on the day of admission. Dr. Turner orders a chest radiograph, CBC (complete blood count), and cultures of sputum and blood. In addition, Dr. Turner orders a test for fecal fat and elastase. (Elastase is a protein-splitting enzyme secreted by the pancreas.) After the cultures are collected, the doctor prescribes cephalexin a daily antimicrobial regimen.

Laboratory and Patient follow-up:

The Burkholderia cepacia complex is a group of genomic species, or genomovars. Genomovar is a term used to describe strains of related organisms that are genetically different but share common traits or characteristics. Microorganisms belonging to a specific genomovar are classified as a species when genetic and or biochemical tests allow specific groups to be differentiated from other related strains. Typically this complex is made up of low-grade nosocomial pathogens most often associated with pneumonia in CF patients. All species within the complex have been isolated from CF patients. However, patients infected with genomovar III tend to have the highest mortality rates and may develop cepacia syndrome, which is a fatal, untreatable necrotizing pneumonia. Burkholderia cepacia may develop resistance rapidly during antibiotic treatment of the patient.

The Cystic Fibrosis Foundation laboratory confirms the identification of the Burkholderia cepacia isolate as genomovar III by 16S ribosomal DNA sequence analysis. Tests are performed to determine whether the organism is susceptible to cephalexin, tobramycin and ticarcillin/clavulanate; the tests yield conflicting results. Dr. Turner switches the antimicrobial regimen to trimethoprim-sulfamethoxazole, ceftazidime, and ciprofloxacin. Chloe has become febrile, and by the seventh day of hospitalization her condition has not improved or stabilized. Dr. Turner orders another set of blood cultures. Chloes oxygen requirements have progressively increased, and her breathing has become more labored. Dr. Turner transfers Chloe to the pediatric intensive care unit (PICU) so that she can be placed on respiratory support.

Q1 Why does Dr. Turner change Chloes initial antimicrobial therapy? Which of the following are valid reasons why Chloes antimicrobial therapy should be changed?

Select all that apply

c>The patient has become febrile.

d>Results of antimicrobial susceptibility testing were conflicting.

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Q2. Which of the following conclusions are supported by the current research data?

Select all that apply:

a>Burkholderia cepacia complex appears to be very diverse in its habitat and distribution.

b>It would appear that the environment may serve as a reservoir for acquiring Burkholderia cepacia complex strains.

c>There appears to be no association between hospital environments and human-to-human transmission of Burkholderia cepacia complex infection.

d>Genomovars III and II appear to be the most virulent or transmissible to humans.

e>Genomovars that inhabit soil can undergo conversion in a human host to become more pathogenic.

Explanation / Answer

1. A. The isolate is confirmed to be Burkholderia cepacia. AND option D. Results of antimicrobial susceptibility testing were conflicting, both are correct. The organisms are resistant to certain antibiotics like aminoglycosides, and hence, the antibiotic therapy is changed.

2.

A. Burkholderia cepacia complex appears to be very diverse in its habitat and distribution.

B. It would appear that the environment may serve as a reservoir for acquiring Burkholderia cepacia complex strains.

D. Genomovars III and II appear to be the most virulent or transmissible to humans.

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