Case 1 A 28-year-old patient arrives at the emergency room complaining of leg pain near the site of a recent surgical incision. The patient has a fever, and the surgical site is red, swollen, and purulent. Red streaks in the skin near the surgical site are also present. Exhibiting the early signs of necrotizing fasciitis, the patient is scheduled for surgical debridement of the wound, and during the procedure a tissue sample is collected and sent to the microbiology laboratory for culture. The specimen is streaked on standard microbiology media, including mannitol salt agar and blood agar. After 24 hours of incubation, small colonies with a large zone of beta hemolysis are growing on the blood agar, while no colonies were observed on the mannitol salt agar. • What does "purulent" mean? • What is necrotizing fasciitis? • What does "debridement" mean? • What component of blood agar makes the medium differential? • What color is uninoculated blood agar? • What color will the medium become next to an alpha hemolytic colony? • What color will the medium become next to a beta hemolytic colony? • What color will the medium become next to a gamma hemolytic colony? • Based on the reported results, which organism is most likely the cause of the patient’s infection – Staphylococcus aureus or Streptococcus pyogenes? Explain your reasoning.
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Step 1: Purulent means containing or producing pus (a thick, often yellowish fluid made up of dead neutrophils, bacteria, and cellular debris), indicating a bacterial infection. Show more…
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The patient is a 4 year-old male who presented to the emergency room with a 2 hour history of vomiting, diarrhea, fever, irritability, and lethargy. The child had gone to sleep on the living room couch at 11 p.m. His grandmother found him on the floor at 3 a.m. covered with feces. When she picked him up to carry him to the bathtub, she noticed he was febrile. She bathed him, and brought him to the emergency room. The patient's medical history indicated that he was in group day care. In the emergency room, he had two episodes of vomiting. His temperature was 38.9°C, pulse 160 beats per min, respiratory rate 36/min, and he was noted to be dehydrated. His stool contained bloody streaks, and on microscopic examination many white blood cells were observed. He had a negative stool examination for ova and parasites as well as a negative blood culture. A MacConkey agar plate culture of the isolated organism revealed colorless colonies. The organism was negative for H2S production, nonmotile and indole negative. In Addition to identifying this infection disease and the infectious agent, ANSWER THE FOLLOWING QUESTIONS: 1. In addition to the microorganism that you have selected, given his clinical (not laboratory) picture, what bacterial pathogens are likely candidates for the etiology of this infection? 2. Why were there white blood cells in the patient's stool sample? What factors contributed to his lethargy?? 3. What was the significance of his being in group-day care? 4. How would you treat this patient and what steps should be taken to prevent transmission of the disease? Also include your interpretation of relevant history and clinical/lab findings!
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Adi S.
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