Microbiology Case Study: a 77 Year Old Woman with a Splenic Abscess

Case History

The patient is a 77 year old woman with a past medical history significant for hypertension, hyperlipidemia, diverticulitis, and advanced vascular disease with mesenteric ischemia and post-prandial pain who presented to an outside hospital with severe diffuse abdominal pain. Of note she was scheduled to undergo endovascular repair of a known occluded celiac artery. Imaging at the outside hospital showed intraperitoneal free air and a fluid collection by the tail of the pancreas. The inferior mesenteric artery was patent but the celiac and superior mesenteric artery were occluded. The lesion at the tail of the pancreas was previously known to the patient, work up showed it was benign. The patient was transferred to our facility and was taken urgently to the OR for exploratory laparotomy for diffuse peritonitis. During surgery the patient was found to have an infarcted spleen with a splenic abscess; no ischemic bowel was seen. A surgical mesh was in place from a previous hernia surgery and was removed. A drain was placed in the abscess and the abdomen was closed. The patient was placed on Zosyn intraoperatively and remained on Zosyn following transfer to the ICU. On post-operative day 6, Zosyn was switched to Ertepenam due to IV and dosing problems.

Laboratory Identification

An aspirate from the abscess was sent to the lab for aerobic and anaerobic culture. Cultures from the abscess showed mixed gram positive and gram negative aerobic and anaerobic organisms. Of note, there was a gram positive rod which showed a double zone of beta hemolysis on the Schaedler blood plate, which grew only in anaerobic conditions. The colonies are clear/gray. The organism is catalase negative and indole positive, and was identified by the MALDI as Clostridium perfringens.

Discussion

C. perfringens is an anaerobic gram positive spore forming rod. This organism is known to cause myonecrosis, gas gangrene, gangrenous cholecystitis, bacteremia, food poisoning, and is a worldwide cause of necrotizing enterocolitis (1). The main virulence factor is the alpha toxin, which is a hemolytic toxin with both phospholipase C and sphingomyelinase activities and is essential in disease. The toxin can rapidly breakdown phospholipid membranes, which is particularly dangerous because it can cause massive intravascular hemolysis in bacteremic patients (1, 2). It is important to recognize the signs of infection early as bacteremia can have a mortality rate of up to 75% (1). Splenic abscess with C. perfringens is rare with only a few case reports in the literature. Typically, splenic abscess are caused by aerobes such as Escherichia coli, Staphylococcus ssp., Streptococcus ssp., and Salmonella ssp. Infection with anaerobes account for only 10% of splenic infections (3). Those with clostridial infections typically had a predisposing condition such as colitis, diabetes, trauma, or malignancy (3).

References

1. Hashiba M, Tomino A, Takenaka N, et al. Clostridium Perfringens Infection in a Febrile Patient with Severe Hemolytic Anemia. The American Journal of Case Reports. 2016;17:219-223. doi:10.12659/AJCR.895721.
2. Awad MM, Bryant AE, Stevens DL, Rood JI.  Virulence studies on chromosomal alpha-toxin and theta-toxin mutants constructed by allelic exchange provide genetic evidence for the essential role of alpha-toxin in Clostridium perfringens-mediated gas gangrene. Molecular Microbiology. 1995;15(2):191.
3. Chalasani, Rajendra MD; Siripurapu, Shantipriya MD; Hasan, Saqib MD. Splenic Abscess due to Clostridium perfringens: A Rare Entity. Infectious Diseases in Clinical Practice. 2007;15(2);137-138.

-Casey Rankins, DO, is a 1^st year Anatomic and Clinical Pathology resident at the University of Vermont Medical Center.

-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Associate Professor at the University of Vermont.