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Rhizobium radiobacter Endocarditis in an Intravenous Drug User: Clinical Presentation, Diagnosis, and Treatment
Rhizobium radiobacter Endocarditis in an Intravenous Drug User: Clinical Presentation, Diagnosis, and Treatment Bilal A. Zahoor,1,2 Brisbane, Queensland, Australia
Rhizobium radiobacter, a soil-based organism, is not, usually, pathogenic unless in the immunecompromised. Endocarditis, in the immunocompromised, is a typical presentation generally as a result of catheter-based infections. We describe the presentation of R. radiobacter prosthetic valve endocarditis and the inherent challenges in its presentation and diagnosis. A patient presented with acute limb ischemia secondary to R. radiobacter-mediated endocarditis and subsequent thromboembolization of the distal superior femoral and proximal popliteal arteries in the left lower limb. He underwent an uneventful thrombolectomy that restored blood flow distal to the occlusion and restored the patency of the affected arteries. Postoperatively, the patient maintained several unexplained febrile episodes. Blood cultures remained negative for infection. A cardiac work-up demonstrated the presence of vegetative growth on the prosthetic mitral and native aortic valves. Histopathologic analysis of the extracted thrombus confirmed the presence of R. radiobacter. On further history, it was elucidated that the patient was an intravenous drug user who routinely stored drug paraphernalia in plant beds. The patient recovered uneventfully after Piptazobactam was administered. R. radiobacter, and similarly other soil-based pathogens, should be considered as a potential source of endocarditic infection and thromboembolization in patients who similarly describe a history of intravenous drug use.
Rhizobium radiobacter is a soil-based pathogen that rarely causes disease in humans other than in the immunecompromised.1,2 It presents with bacteremia as a consequence of improper catheter hygiene.2 Clinically, the infection has been associated with peritonitis, endocarditis, and urinary tract infections.3e5 To date, 2 cases of R. radiobacter-mediated endocarditis have been published.6,7 This is the first report describing R. radiobacter-mediated endocarditis of a prosthetic mitral valve; previous reports describe
1 Department of Surgery, School of Medicine, University of Queensland, Brisbane, QLD, Australia. 2 Department of Trauma, Royal Brisbane & Women’s Hospital, Brisbane, QLD, Australia.
Correspondence to: Bilal A. Zahoor, MBBS, MPH, Surgery, School of Medicine, University of Queensland, Herston Rd. Brisbane, QLD 4005, Australia; E-mail: [email protected] Ann Vasc Surg 2016; 35: 206.e9–206.e11 http://dx.doi.org/10.1016/j.avsg.2016.01.041 Ó 2016 Elsevier Inc. All rights reserved. Manuscript received: October 6, 2015; manuscript accepted: January 18, 2016; published online: 27 May 2016
native valve endocarditis exclusively. In addition, our case describes the unique sequale of this endocarditic infection, in particular the challenges in its diagnosis and unique etiology of infection.
CASE REPORT A 44-year-old male patient reported a 12-hour history of acute pain of the lower left limb. On developing sensorimotor deficits in the affected limb, the patient was transferred emergently to a tertiary care medical center where a diagnosis of acute limb ischemia of the lower left limb was made. On examination, the patient was febrile, tachycardic, and tachypneic. The affected limb was noted to have a bluish hue, pulseless, and poikilothermic when compared with the unaffected limb. A limited history of prior endocarditis secondary to cocaine abuse, prior mitral valve replacement, and an active hepatitis C infection was reported by the patient. Given the acute nature of the patient’s presentation, a computed tomography angiography study was completed expediently, confirming the presence of a thrombus, 206.e9
206.e10 Case reports
greater than 10 cm in length, in the left distal superior femoral and proximal popliteal arteries. Radiologically, no contrast was seen distal to the site of occlusion. No other consideration to identify the source of the thrombus was given at the time owing to acuity and delayed presentation of the patient’s symptoms. To save the affected limb expediently, the patient underwent an uneventful femoralpopliteal thromboembolectomy, using a balloon catheter. This restored the patency of the occluded arteries and pedal pulses in the lower left limb. The extracted thrombus was sent for histopathologic analysis wherein it was confirmed to contain R. radiobacter. Its sensitivity was reported to be greatest to Piptazobactam. Of note, blood cultures, to identify other potential embolic sources, were reported to be negative. Postoperatively (on day 4), after the patient had recovered significantly, the patient underwent several tests to identify the source of thrombus. Cultures of blood samples remained negative for bacteremia on serial examination. Similarly, Holter monitoring was negative for any cardiac arrhythmia or related significant findings. However, a transthoracic echocardiogram revealed severe mitral regurgitation with a mean gradient of 12 mm Hg across a prosthetic mitral valve in addition to a hyperdynamic left ventricular function. On additional inquiry, a transesophageal echocardiogram (TOE) described ‘‘the presence of fulminant vegetation on the anterior leaflet of the prosthetic mitral valve (1.2 cm) and vegetation (0.7 0.5 cm2) on the noncoronary cusp of the aortic valve.’’ On further inquiry, the patient revealed he was an active intravenous drug user and stored his drug paraphernalia (including syringes and needles) in plant beds before use. The patient’s history and physical examination were otherwise unremarkable apart from a 2of 6 holosystolic murmur which, we attribute to the vegetative growth on the valves and left ventricular function. Given the patient’s prior surgical history, his active hepatitis C infection, his overall immunecompromised status and most important, his unwillingness to abstain from further intravenous drug use (IVDU), he was an extremely high-risk candidate for prosthetic valve replacement. Therein, it was decided to continue medical treatment for his R. radiobacter-mediated endocarditic infection. He was commenced on a 6-week course of IV Piptazobactam (4.5 gm IV q6h) and discharged to a step-down facility where he recovered uneventfully.
DISCUSSION R. radiobacter is a gram-negative bacilli often found in soil-based environments and is usually a plant pathogen.1,2 R. radiobacter infections are rare among humans and are almost always associated with a catheter-related sepsis.3 Our patient had several
Annals of Vascular Surgery
risk factors that would predispose him or her for R. radiobacter-mediated endocarditis. Our patient was an intravenous drug user and had a chronic illness (hepatitis C). Furthermore, although blood cultures were negative, histopathologic diagnosis of the arterial thrombus confirmed R. radiobacter consistent with the vegetation seen on Trans-Esophageal Echocardiogram (TEE). We were able to elicit that most of the patient’s drug paraphernalia was hidden, to avoid detection, in plant beds. This provides insight into identifying the potential source of the R. radiobacter infection in our patient. This demands further scrutiny of plant- and/or soil-based organisms, which may otherwise be indolent, as potential and causative sources of endocarditic infections and thromboembolic episodes observed in intravenous drug users. Recently, Delftia acidovorans, also a plant- and/or soil-based opportunistic pathogen, was reported to cause newly onset acute infective endocarditis.8 Nocardia asteroides, also a soil-borne pathogen, has been only recently reported to result in native valve endocarditisda departure from typical presentations seen in prosthetic valve endorcarditis.9 Finally, an emerging spectra of new and atypical opportunistic pathogens, (bacterial and fungal) which result in previously encountered novel infection is a concern for alarm. Quintessentially, our patient injected contraband drugs intravenously using soil-contaminated syringes and needles. R. radiobacter is not ubiquitously fatal1; however, its sequela can have a very deleterious effectdas evident in this case. R. radiobacter is susceptible to most antibiotics, Piptazobactam being the most sensitive.1 In conclusion, this case emphasizes the unique and novel instances of prosthetic mitral valve and native aortic valve endocarditis by a rare and mostly unencountered plant-based pathogen. In conclusion, R. radiobacter is common soil-based organism, which generally poses no direct pathogenicity to humans unless immunecompromised. As demonstrated in the previously mentioned case, sources of infection are generally limited to catheter-based sources. Unexplained febrile episodes should warrant additional history. Histopathologic analysis is critical for accurate diagnosis of infection. Routine laboratory tests may routinely mask signs of active infection delaying subsequent treatment. In patients who report IVDU, unexplained febrile episodes should warrant further consideration of soil-based organisms such as R. radiobacter. Piptazobactam generally offers the most sensitive antimicrobial therapy.
Volume 35, August 2016
REFERENCES 1. Edmond MB, Riddler SA, Baxter CM, et al. Agrobacterium radiobacter: a recently recognized opportunistic pathogen. Clin Infect Dis 1993;16:388e91. 2. Plotkin GR. Agrobacterium radiobacter prosthetic valve endocarditis. Ann Intern Med 1980;93:839e40. 3. Paphitou NI, Rolston KV. Catheter-related bacteremia caused by Agrobacterium radiobacter in a cancer patient: case report and literature review. Infection 2003;31: 421e4. 4. Jankauskiene A, Baciulis V, Baliukynaite V, Kaltenis P. Peritonitis caused by Agrobacterium tumefaciens in a child on peritoneal dialysis. Nephrol Dial Transplant 2003;18: 2456e7.
Case reports 206.e11
5. Mastroianni A, Coronado O, Nanetti A, et al. Agrobacterium radiobacter pneumonia in a patient with HIV infection. Eur J Clin Microbiol Infect Dis 1996;15:960e3. 6. Gonsalvez JF, Zambrano Infantinot Rdel C, Calca~ no C, et al. Infective endocarditis by Rhizobium radiobacter. A case report. Invest Clin 2013;54:68e73. 7. Guerra NC, Nobre A, Cravino J. Native mitral valve endocarditis due to Rhizobium radiobacterefirst case report. Rev Port Cir Cardiotorac Vasc 2013;20:203e5. 8. Mahmood S, Taylor KE, Overman TL, McCormick MI. Acute infective endocarditis caused by Delftia acidovorans, a rare pathogen complicating intravenous drug use. J. Clin. Microbiol 2012;50:3799e800. 9. Watson A, French P, Wilson M. Nocardia asteroides Native Valve Endocarditis. Clin Infect Dis 2001;32:660e1.
Rhizobium radiobacter, a soil-based organism, is not, usually, pathogenic unless in the immunecompromised. Endocarditis, in the immunocompromised, is a typical presentation generally as a result of catheter-based infections. We describe the presentation of R. radiobacter prosthetic valve endocarditis and the inherent challenges in its presentation and diagnosis. A patient presented with acute limb ischemia secondary to R. radiobacter-mediated endocarditis and subsequent thromboembolization of the distal superior femoral and proximal popliteal arteries in the left lower limb. He underwent an uneventful thrombolectomy that restored blood flow distal to the occlusion and restored the patency of the affected arteries. Postoperatively, the patient maintained several unexplained febrile episodes. Blood cultures remained negative for infection. A cardiac work-up demonstrated the presence of vegetative growth on the prosthetic mitral and native aortic valves. Histopathologic analysis of the extracted thrombus confirmed the presence of R. radiobacter. On further history, it was elucidated that the patient was an intravenous drug user who routinely stored drug paraphernalia in plant beds. The patient recovered uneventfully after Piptazobactam was administered. R. radiobacter, and similarly other soil-based pathogens, should be considered as a potential source of endocarditic infection and thromboembolization in patients who similarly describe a history of intravenous drug use.
Rhizobium radiobacter is a soil-based pathogen that rarely causes disease in humans other than in the immunecompromised.1,2 It presents with bacteremia as a consequence of improper catheter hygiene.2 Clinically, the infection has been associated with peritonitis, endocarditis, and urinary tract infections.3e5 To date, 2 cases of R. radiobacter-mediated endocarditis have been published.6,7 This is the first report describing R. radiobacter-mediated endocarditis of a prosthetic mitral valve; previous reports describe
1 Department of Surgery, School of Medicine, University of Queensland, Brisbane, QLD, Australia. 2 Department of Trauma, Royal Brisbane & Women’s Hospital, Brisbane, QLD, Australia.
Correspondence to: Bilal A. Zahoor, MBBS, MPH, Surgery, School of Medicine, University of Queensland, Herston Rd. Brisbane, QLD 4005, Australia; E-mail: [email protected] Ann Vasc Surg 2016; 35: 206.e9–206.e11 http://dx.doi.org/10.1016/j.avsg.2016.01.041 Ó 2016 Elsevier Inc. All rights reserved. Manuscript received: October 6, 2015; manuscript accepted: January 18, 2016; published online: 27 May 2016
native valve endocarditis exclusively. In addition, our case describes the unique sequale of this endocarditic infection, in particular the challenges in its diagnosis and unique etiology of infection.
CASE REPORT A 44-year-old male patient reported a 12-hour history of acute pain of the lower left limb. On developing sensorimotor deficits in the affected limb, the patient was transferred emergently to a tertiary care medical center where a diagnosis of acute limb ischemia of the lower left limb was made. On examination, the patient was febrile, tachycardic, and tachypneic. The affected limb was noted to have a bluish hue, pulseless, and poikilothermic when compared with the unaffected limb. A limited history of prior endocarditis secondary to cocaine abuse, prior mitral valve replacement, and an active hepatitis C infection was reported by the patient. Given the acute nature of the patient’s presentation, a computed tomography angiography study was completed expediently, confirming the presence of a thrombus, 206.e9
206.e10 Case reports
greater than 10 cm in length, in the left distal superior femoral and proximal popliteal arteries. Radiologically, no contrast was seen distal to the site of occlusion. No other consideration to identify the source of the thrombus was given at the time owing to acuity and delayed presentation of the patient’s symptoms. To save the affected limb expediently, the patient underwent an uneventful femoralpopliteal thromboembolectomy, using a balloon catheter. This restored the patency of the occluded arteries and pedal pulses in the lower left limb. The extracted thrombus was sent for histopathologic analysis wherein it was confirmed to contain R. radiobacter. Its sensitivity was reported to be greatest to Piptazobactam. Of note, blood cultures, to identify other potential embolic sources, were reported to be negative. Postoperatively (on day 4), after the patient had recovered significantly, the patient underwent several tests to identify the source of thrombus. Cultures of blood samples remained negative for bacteremia on serial examination. Similarly, Holter monitoring was negative for any cardiac arrhythmia or related significant findings. However, a transthoracic echocardiogram revealed severe mitral regurgitation with a mean gradient of 12 mm Hg across a prosthetic mitral valve in addition to a hyperdynamic left ventricular function. On additional inquiry, a transesophageal echocardiogram (TOE) described ‘‘the presence of fulminant vegetation on the anterior leaflet of the prosthetic mitral valve (1.2 cm) and vegetation (0.7 0.5 cm2) on the noncoronary cusp of the aortic valve.’’ On further inquiry, the patient revealed he was an active intravenous drug user and stored his drug paraphernalia (including syringes and needles) in plant beds before use. The patient’s history and physical examination were otherwise unremarkable apart from a 2of 6 holosystolic murmur which, we attribute to the vegetative growth on the valves and left ventricular function. Given the patient’s prior surgical history, his active hepatitis C infection, his overall immunecompromised status and most important, his unwillingness to abstain from further intravenous drug use (IVDU), he was an extremely high-risk candidate for prosthetic valve replacement. Therein, it was decided to continue medical treatment for his R. radiobacter-mediated endocarditic infection. He was commenced on a 6-week course of IV Piptazobactam (4.5 gm IV q6h) and discharged to a step-down facility where he recovered uneventfully.
DISCUSSION R. radiobacter is a gram-negative bacilli often found in soil-based environments and is usually a plant pathogen.1,2 R. radiobacter infections are rare among humans and are almost always associated with a catheter-related sepsis.3 Our patient had several
Annals of Vascular Surgery
risk factors that would predispose him or her for R. radiobacter-mediated endocarditis. Our patient was an intravenous drug user and had a chronic illness (hepatitis C). Furthermore, although blood cultures were negative, histopathologic diagnosis of the arterial thrombus confirmed R. radiobacter consistent with the vegetation seen on Trans-Esophageal Echocardiogram (TEE). We were able to elicit that most of the patient’s drug paraphernalia was hidden, to avoid detection, in plant beds. This provides insight into identifying the potential source of the R. radiobacter infection in our patient. This demands further scrutiny of plant- and/or soil-based organisms, which may otherwise be indolent, as potential and causative sources of endocarditic infections and thromboembolic episodes observed in intravenous drug users. Recently, Delftia acidovorans, also a plant- and/or soil-based opportunistic pathogen, was reported to cause newly onset acute infective endocarditis.8 Nocardia asteroides, also a soil-borne pathogen, has been only recently reported to result in native valve endocarditisda departure from typical presentations seen in prosthetic valve endorcarditis.9 Finally, an emerging spectra of new and atypical opportunistic pathogens, (bacterial and fungal) which result in previously encountered novel infection is a concern for alarm. Quintessentially, our patient injected contraband drugs intravenously using soil-contaminated syringes and needles. R. radiobacter is not ubiquitously fatal1; however, its sequela can have a very deleterious effectdas evident in this case. R. radiobacter is susceptible to most antibiotics, Piptazobactam being the most sensitive.1 In conclusion, this case emphasizes the unique and novel instances of prosthetic mitral valve and native aortic valve endocarditis by a rare and mostly unencountered plant-based pathogen. In conclusion, R. radiobacter is common soil-based organism, which generally poses no direct pathogenicity to humans unless immunecompromised. As demonstrated in the previously mentioned case, sources of infection are generally limited to catheter-based sources. Unexplained febrile episodes should warrant additional history. Histopathologic analysis is critical for accurate diagnosis of infection. Routine laboratory tests may routinely mask signs of active infection delaying subsequent treatment. In patients who report IVDU, unexplained febrile episodes should warrant further consideration of soil-based organisms such as R. radiobacter. Piptazobactam generally offers the most sensitive antimicrobial therapy.
Volume 35, August 2016
REFERENCES 1. Edmond MB, Riddler SA, Baxter CM, et al. Agrobacterium radiobacter: a recently recognized opportunistic pathogen. Clin Infect Dis 1993;16:388e91. 2. Plotkin GR. Agrobacterium radiobacter prosthetic valve endocarditis. Ann Intern Med 1980;93:839e40. 3. Paphitou NI, Rolston KV. Catheter-related bacteremia caused by Agrobacterium radiobacter in a cancer patient: case report and literature review. Infection 2003;31: 421e4. 4. Jankauskiene A, Baciulis V, Baliukynaite V, Kaltenis P. Peritonitis caused by Agrobacterium tumefaciens in a child on peritoneal dialysis. Nephrol Dial Transplant 2003;18: 2456e7.
Case reports 206.e11
5. Mastroianni A, Coronado O, Nanetti A, et al. Agrobacterium radiobacter pneumonia in a patient with HIV infection. Eur J Clin Microbiol Infect Dis 1996;15:960e3. 6. Gonsalvez JF, Zambrano Infantinot Rdel C, Calca~ no C, et al. Infective endocarditis by Rhizobium radiobacter. A case report. Invest Clin 2013;54:68e73. 7. Guerra NC, Nobre A, Cravino J. Native mitral valve endocarditis due to Rhizobium radiobacterefirst case report. Rev Port Cir Cardiotorac Vasc 2013;20:203e5. 8. Mahmood S, Taylor KE, Overman TL, McCormick MI. Acute infective endocarditis caused by Delftia acidovorans, a rare pathogen complicating intravenous drug use. J. Clin. Microbiol 2012;50:3799e800. 9. Watson A, French P, Wilson M. Nocardia asteroides Native Valve Endocarditis. Clin Infect Dis 2001;32:660e1.