A MASSIVE LESION: CULTURE NEGATIVE MRSA ENDOCARDITIS IN AN IV DRUG USER

Abstract

SESSION TITLE: Monday Medical Student/Resident Case Report Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/21/2019 02:30 PM - 03:15 PM INTRODUCTION: The rate of hospitalization for endocarditis in IV drug use has increased from 6% to 12% from 2000 to 2013. The most commonly involved heart valve In IV drug use is the tricuspid valve, with the pulmonic valve being involved at a rate of 1-2%. Studies from Europe show that around 20% of cases of infectious endocarditis have negative blood cultures, Here, we present a rare case of blood culture negative MRSA endocarditis associated with a massive valvular lesion involving the tricuspid and pulmonic valves. CASE PRESENTATION: Our patient is a 32 year old male with a past medical history of hepatitis C, MRSA cellulitis 1 year ago, and active IV drug abuse who presented during the night complaining of right sided chest pain for 2 days described as sharp, worse with deep inspiration, & coughing. He also had flank pain radiating to his lower back bilaterally. At presentation, he was afebrile with mild tachycardia and hypertension, but otherwise stable. Initial labwork showed a leukocytosis of 19.8, ESR of 43, and a CRP of 22. CT of the abdomen and pelvis, showed an enlarged quadratus lumborum muscle with attenuation suspicious for abscess. CTA showed multiple peripheral cavitary lesions suspicious for septic emboli. At this time, blood cultures were drawn prior to initiating the patient on vancomycin for suspected endocarditis. The patient underwent a transesophageal echocardiogram, which revealed a 5cm x 1.5cm freely mobile echogenicity that stretched from the pulmonic to the tricuspid valve. MRI of his spine revealed a 5.2 cm multiloculated enhancing collection within the right iliacus. Blood cultures were preliminary negative, so interventional radiology obtained a fluid sample from his right iliacus which came back positive for MRSA. Cardiothoracic surgery recommended watchful waiting, as there was no underlying valvular damage. He was discharged on day 11, and his blood cultures were still negative on discharge. DISCUSSION: Negative blood culture for common endocarditis pathogens such as MRSA does not rule out endocarditis. In our case, sterile site culture was helpful to establish the bacterial pathogen rather than blood culture. This is particularly important in patients whom history of previous antibiotic therapy may not be clear, or blood cultures had already cleared spontaneously. CONCLUSIONS: Blood cultures are vital in making the diagnosis of infective endocarditis, however there is always a chance that the infection has cleared from the blood. In these cases, blood cultures may be negative, however the patient may still have a pathogen that risks being undertreated. Evaluation of all sources of metastatic infection could be very helpful in making the correct diagnosis of infective endocarditis. Reference #1: Baddour LM, Wilson WR. 2015, et al. Infective Endocarditis in Adults: Diagnosis, Antimicrobial Therapy, and Management of Complications. Circ. 2015;132:1435-1486. doi:10.1161/CIR.0000000000000296 Reference #2: Wurcel AG, Anderson JE, Chui KKH, et al. Increasing Infectious Endocarditis Admissions Among Young People Who Inject Drugs. Open Forum Infectious Diseases. 2016;3(3):ofw157. doi:10.1093/ofid/ofw157. Reference #3: Miranda WR, Connolly HM, et. Al. Infective Endocarditis Involving the Pulmonary Valve. The American Journal of Cardiology. 2015;116: 1928-1931. doi:/10.1016/j.amjcard.2015.09.038 DISCLOSURES: No relevant relationships by Syed Aleem, source=Web Response No relevant relationships by Brendan Gill, source=Web Response No relevant relationships by Mahwish Hussain, source=Web Response No relevant relationships by Sunil Ramaswamy, source=Web Response No relevant relationships by Mohamed Yassin, source=Web Response