<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 2-year-old boy is brought to the physician because of fever, productive cough, and shortness of breath. Since birth, he has had multiple respiratory infections requiring treatment with antibiotics. His immunizations are up-to-date. He is in the 10th percentile for height and weight. His temperature is 38C 100.3F. Examination detects diffuse bilateral wheezing and cervical lymphadenopathy. Flow cytometric analysis of a serum sample from the patient fails to fluoresce after incubation with dihydrorhodamine. This patient is at greatest risk of infection with which of the following organisms?? A: Enterococcus faecium, B: Serratia marcescens, C: Streptococcus pneumoniae, D: Clostridioides difficile, E: Streptococcus pyogenes,  <response>: This is a clinical vignette describing a 2-year-old boy with recurrent respiratory infections, fever, cough, shortness of breath, wheezing, and lymphadenopathy. His growth is impaired as evidenced by low height and weight percentiles. The key finding is that flow cytometric analysis of his serum sample failed to fluoresce after incubation with dihydrorhodamine. This indicates a defect in NADPH oxidase function, which is characteristic of chronic granulomatous disease CGD. CGD is a primary immunodeficiency caused by defective phagocyte oxidative burst, leading to recurrent life-threatening bacterial and fungal infections. The organisms listed in the answer choices are potential pathogens in CGD. Based on the clinical history provided, the boy is most likely infected with Staphylococcus aureus or Burkholderia cepacia complex, but these are not answer options. Of the choices provided, patients with CGD are at greatest risk of infection with Serratia marcescens.B: Serratia marcescens 