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Ann Thorac Surg 2005;80:1489-1490
© 2005 The Society of Thoracic Surgeons

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Case report

Infective Endocarditis Associated With a Scorpion Sting

Department of Cardiovascular and Thoracic Surgery, University of Texas at Southwestern Medical Center, Dallas, Texas

Accepted for publication April 1, 2004.

^_* Address reprint requests to Dr Jessen, University of Texas Southwestern Medical Center at Dallas, 5939 Harry Hines Blvd, Dallas, TX 75390-8879 (Email: michael.jessen{at}utsouthwestern.edu).

	Abstract

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We report the successful surgical intervention in two cases of aortic valve bacterial endocarditis after scorpion stings. Infective endocarditis developed in both patients several weeks after they suffered repeated scorpion stings. Both patients had similar, but uncommon features: (1) the isolated organisms were unusual causes of infective endocarditis (streptococcus group G and Streptococcus milleri), (2) annular abscesses developed that required either aortic root replacement with a homograft or annular patch repair with pericardium, and (3) complete heart block developed postoperatively, requiring permanent pacemaker implantation. Both patients completed a 6-week postoperative course of antibiotic therapy and are without recurrent infection.

	Introduction

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Scorpion stings are not uncommon occurrences around the world, including regions of the southwestern United States. Two medical sequelae can result from the sting of a scorpion. A local, painful swelling may develop at the sting site. These superficial wounds usually heal without difficulty. Second, a scorpion's sting can cause a systemic reaction through envenomation. In rare instances, severe scorpion envenomation can be fatal.

Scorpion venom has been shown to stimulate the autonomic nervous system, causing a release of catecholamines [1]. A reversible cardiomyopathy can result from the direct, toxic effect of the venom on cardiac fibers [2, 3]. Although there are no known effects of the toxin on valvular function or structure, secondary infection of the sting lesions can lead to a cellulitis and the development of associated bacteremia. Patients with diseased native valves, or patients who have already had a valve replaced with a prosthesis, are at increased risk for developing infective endocarditis (IE) [4]. We report two unusual cases of aortic valve IE associated with scorpion stings.

	Case Reports

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Patient 1
A 55-year-old man with a 23-mm Medtronic-Hall mechanical prosthesis (Minneapolis, MN) presented with complaints of fevers. The patient had recently suffered repeated scorpion stings, and swollen, painful skin lesions had developed. He was treated for 7 days with oral antibiotics, with only minor improvement in his symptoms. He was admitted to the hospital and broad-spectrum intravenous antibiotics were initiated. Multiple blood cultures grew group G streptococcus (GGS). After receiving antibiotics, the inflammation surrounding the sting sites had completely resolved.

A transesophageal echocardiogram demonstrated a prosthetic aortic valve vegetation, a perivalvular leak, and an annular abscess at the noncoronary aortic valve sinus. Preoperative cardiac catheterization revealed an occluded right coronary artery.

He underwent removal of the infected prosthesis, aortic root replacement with a 23-mm cryopreserved human cadaveric homograft, and coronary artery bypass grafting of the posterior descending coronary artery with saphenous vein. Postoperatively, he developed complete heart block. After completing a 6-week course of intravenous penicillin G, he underwent the implantation of a permanent transvenous pacemaker. Subsequent echocardiograms have revealed no problems with his aortic homograft, and no evidence of recurrent infection.

Patient 2
A 34-year-old man sustained several scorpion stings. He was prescribed oral antibiotics for swollen, painful sting lesions. Despite his failure to complete the antibiotic therapy, the skin lesions resolved. Chest discomfort, shortness of breath, and fever developed 2 weeks later. He was admitted to the hospital and started on intravenous penicillin G. Multiple blood cultures grew Streptococcus milleri.

A transesophageal echocardiogram demonstrated a bicuspid aortic valve, aortic valve vegetations, 4+ aortic insufficiency, an annular abscess involving the right and noncoronary aortic sinuses, and purulent pericarditis. An electrocardiogram revealed first-degree atrioventricular block with a PR interval of 0.32 seconds.

The patient immediately underwent aortic valve replacement with a 29-mm Medtronic-Hall mechanical prosthesis, and bovine pericardial patch repair of the annular abscess. His postoperative course was complicated by third-degree heart block, for which he received a permanent transvenous pacemaker. He received 6 weeks of intravenous gentamicin postoperatively. In follow-up, he has had no recurrent signs of infection.

	Comment

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Streptococci are the most common cause of IE in the general population, accounting for 50% to 70% of cases [4]. However, only 5% to 7% of IE cases secondary to streptococci are from species other than viridans streptococci, enterococci, or S. bovis [5]. S. milleri and GGS are both organisms characterized by a propensity for invasive pyogenic infections that often lead to abscess formation [5]. Skin is the most common portal of entry for these pathogens (61%), with cellulitis being the most common infectious manifestation (50%) [6]. Endocarditis occurs in only 8% of the cases.

A study by the Beta-Hemolytic Streptococci Infective Endocarditis Study Group compared the physiologic and pathogenic properties of S. milleri and GGS. In 89 cases of IE that were due either to S. milleri (30) or GGS (59), patients infected with GGS were younger and had more underlying diseases with fewer cardiomyopathies [5]. Additionally, patients with endocarditis from GGS had a more aggressive presentation and evolution of their disease.

There are more than 90 species of scorpions in the United States and approximately 1500 species worldwide. They usually hide under rocks and debris, including shoes. Ninety percent of scorpion stings, however, are isolated to the hands. Most of the lesions resolve with local therapy. In older, or immunocompromised patients, secondary bacterial cellulitis can develop at the sting site. Common skin flora, such as streptococci, are the usual offending microorganisms. If the cellulitis goes untreated, or is insufficiently treated, a bacteremia can result.

IE is more likely to occur in patients with native valve disease or with mechanical valve prostheses. Many cases of IE from streptococci can be cleared with a course of intravenous antibiotics. However, infection with more aggressive organisms, such as S. milleri and GGS, may mandate early surgical intervention consisting of valve replacement and débridement. If treatment is delayed, an annular abscess may result that may dramatically increase the mortality from this disease. The mortality rate for patients diagnosed with IE resulting from infection with either S. milleri or GGS ranges between 14% to 27% [7].

We chose to perform an aortic root replacement with a homograft in the first patient because the IE resulted in an extensive annular abscess in the setting of a prior aortic valve prosthesis [8]. In the second patient, urgent operative intervention was necessary because of progressive electrocardiogram changes that suggested a rapidly progressing annular abscess affecting the conduction system. An appropriate homograft could not be acquired, and we chose to simply replace the valve and débride and patch the annular abscess. Pathologic analysis of the excised valvular tissue was unremarkable in both patients.

It is possible, but unlikely, that the scorpion was a vector for the streptococcal cellulitis and associated IE. Unfortunately, the species of scorpion was not identified in either case, and knowing the species of the offending scorpions might help with assessing the potential severity of the sting and any associated illnesses. It is not known if scorpions are capable of transmitting bacteria through their stings. More likely, the scorpion sting initiated a series of events that led to IE in patients who were at increased risk of developing infection.

S. milleri is a normal inhabitant of the oropharynx and gastrointestinal tracts in humans, and is less frequently the cause of skin or soft tissue infections. The unusual situation of two patients developing IE with organisms that are not commonly associated with soft tissue infections might suggest that scorpions may be able to transmit bacterial infections. Additional studies are needed to better answer this question. We are unaware of previous reported cases of IE resulting from a scorpion sting, but our experience suggests that treating physicians should be aware of serious infectious sequelae when determining the care plan for patients with scorpion stings.

Local sting wounds should be carefully evaluated and treated with antibiotics capable of covering a broad spectrum of streptococci species. Both elderly and immunocompromised patients should be treated aggressively and followed closely. In addition, patients with known valvular disease, or who have previously undergone valve replacement, may benefit from extended antibiotic coverage. Any signs of continued or recurrent infection should prompt early evaluation for IE by transthoracic or transesophageal echocardiography. If signs of IE are present, particularly if virulent organisms are implicated, aggressive surgical therapy may be required.

	References

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1. Gueron M, Ilia R, Sofer S. The cardiovascular system after scorpion envenomation. A review J Toxicol Clin Toxicol 1992;30(2):245-258.[Medline]
2. Hering SE, Jurca M, Vichi FL, Azevedo-Marques MM, Cupo P. ‘Reversible cardiomyopathy' in patients with severe scorpion envenoming by Tityus serrulatus evolution of enzymatic, electrocardiographic and echocardiographic alterations. Ann Trop Paediatr 1993;13(2):173-182.[Medline]
3. Bentur Y, Taitelman U, Aloufy A. Evaluation of scorpion stingsthe poison center perspective. Vet Hum Toxicol 2003;45(2):108-111.[Medline]
4. Mylonakis E, Calderwood S. Infective endocarditis in adults N Engl J Med 2001;345:1318-1330.[Free Full Text]
5. Lefort A, Lortholary O, Cassus P, Selton-Suty C, Guillevin L, Mainardi J. Comparison between adult endocarditis due to Beta-hemolytic streptococci (serogroups A, B, C, and G) and Streptococcus milleri Arch Intern Med 2002;162:2450-2456.[Abstract/Free Full Text]
6. Lewthwaite P, Parsons HK, Bates CJ, McKendrick MW, Dockrell DH. Group G streptococcal bacteraemiaan opportunistic infection associated with immune senescence. Scand J Infect Dis 2002;34(2):83-87.[Medline]
7. Smyth EG, Pallett AP, Davidson RN. Group G streptococcal endocarditistwo case reports, a review of the literature and recommendations for treatment. J Infect 1988;16(2):169-176.[Medline]
8. Gulbins H, Kilian E, Roth S, Uhlig A, Kreuzer E, Reichart B. Is there an advantage in using homografts in patients with acute infective endocarditis of the aortic valve? J Heart Valve Dis 2002;11(4):492-497.[Medline]

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Michael A. Wait Michael E. Jessen Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Wheatley, G. H. Articles by Jessen, M. E. Search for Related Content PubMed PubMed Citation Articles by Wheatley, G. H., III Articles by Jessen, M. E.