Question

The patient was a 23 y/o female with an autoimmune connective tissue disorder who presented with fever, left foot, and right upper quadrant pain, nausea, and vomiting. An exploratory la performed duri peritoneum. revealed ing which 300 ml of greenish, nonodorous purulent material was aspirated from the An appendectomy was performed as well. A gram stain of the aspirate of the peritoneum the presence of moderate polymorphonuclear leukocytes (PMNs) and a few gram positive cocci. Gram staining an aspirate of the fourth metatarsal joint revealed numerous PMNs, but no organisms were seen. A blood culture collected on admission, joint, and peritoneal aspirates grew the same organism. On a sheep blood agar plate the organism produced large, transparent to translucent co lonies with large zones of beta hemolysis. The gram positive cocci were catalase negative. When colonies are mucoid, this usually indicates the presence of which virulence factor? Based on the sites of the infection, which three types of infections does this patient have? On the basis of the Gram stain and the infections observed, this organism belongs to which genus? What further characteristics of this organism would be helpful in determining its identity? What organism is this? What life-threatening, non-suppurative sequelae can follow infection with this organism? 1. 2. 3. 4. 5. 6.

Answer 1

1. The mucoid colonies indicate the presence of capsuled organisms. The capsule helps bacteria to adhere to host cells, protect them from action of complementary proteins, antibodies and toxins. It hosts surface antigens. The capsule also protects the bacteria from the phagocytic action of leukocytes.
2. Based on the sites of infection the patient suffers from septic arthritis, cellulitis and abdominal abscess.
3. On the basis of Gram stain and infections, the organism belongs to genus Streptococcus.
4. The other characteristics that help in identification of this organism are catalase negative, blood culture with transparent to translucent colonies having large zones of beta hemolysis, joints and peritoneal involvement. The other factors that can be helpful are presence of bacitracin sensitivity, hemolysins O and S, anti DNAse B enzyme and streptozyme enzyme.
5. The organism here is Beta hemlolytic Streptococcus pyogenes.
6. The non suppurative sequele following the infection from this organism are acute rheumatic fever and acute glomerulonephritis.

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