Erysipelothrix Bacteremia; is Endocarditis a Rule?

Abstract

Erysipelothrix rhusiopathiae is a Gram-positive bacillus, a zoonotic pathogen rarely causing human infections ranging from localized skin infections to invasive infections such as endocarditis. In this report, we present two cases of Erysipelothrix bacteremia. The first case is a native valve tricuspid endocarditis, which is a highly unusual valve to be involved. The second case is bacteremia, probably secondary to a minor skin breach, which did not involve heart valves. Erysipelothrix bacteremia is considered highly associated with infective endocarditis and a high mortality rate, which could be a bias due to underreporting of Erysipelothrix bacteremia without endocarditis. Erysipelothrix is intrinsically resistant to vancomycin, the first-line agent for Gram-positive bacteremia. Both the patients in this report were treated successfully with ceftriaxone.

INTRODUCTION

Erysipelothrix rhusiopathiae is an anaerobic, Gram-positive to Gram variable rod. It is primarily a zoonotic pathogen; human infections are rare and are due to exposure to infected animals, such as fish or swine. Individuals with occupational exposures to animals, such as veterinarians, abattoir workers, and fisherman, are at greater risk of infection. We report two cases of E. rhusiopathiae infection from our center.

CASE REPORTS

Case 1

A 31-year-old female homemaker presented with complaints of fever and chills of a 1-month duration. She did not have any localizing symptoms or signs. She was investigated and treated elsewhere for her nonresolving fever with two courses of 5 days of oral antibiotics, which gave her intermittent relief; however, the fever relapsed. She had a significant past medical history of systemic lupus erythematosus (SLE). She was diagnosed with lupus nephritis 1 month before the onset of fever and initiated on mycophenolate mofetil. She was on mycophenolate mofetil (500 mg twice daily), oral steroids (prednisone 50 mg once daily) along with antihypertensive medication at the time of admission for fever. On examination, she was afebrile, pulse 110/min, respiratory rate 22/min, and blood pressure 117/51 mmHg. Bilateral basal crepitations were present on auscultation of the lung fields. Cardiac auscultation revealed S3 gallop.

Chest X-ray showed an increased cardiothoracic ratio and prominent vascular markings. Two-dimensional Doppler and color echocardiography showed multiple vegetation attached to the tricuspid valve, Grade 2 tricuspid regurgitation, moderate pulmonary hypertension, and global hypokinesia of left ventricle and right ventricle dysfunction as well. The leukocyte count was 10,100/mm³ with neutrophilia (84%) and hemoglobin level of 5.7 gm%. C-reactive protein was 299 mg/l. Erythrocyte sedimentation rate was 106 mm/h.

After three sets of blood cultures were drawn, she was empirically started on intravenous ceftriaxone and vancomycin. All three sets of blood cultures showed Gram-positive to Gram-variable pleomorphic rods morphologically resembling E. rhusiopathiae, which was subsequently confirmed by biochemical tests and automated identification (Vitek) [Figure 1]. On retrospective questioning, she had a cut injury on her right hand with a fishbone while cutting the fish. Drug susceptibility testing on blood culture was reported to be sensitive to penicillin, ceftriaxone, ofloxacin, carbapenem, clindamycin, and doxycycline. Her antibiotic was switched to ceftriaxone alone. Her repeat blood cultures were negative. Follow-up echo at 10 days showed a significant reduction of the size of vegetations. She was discharged with advice to continue oral ampicillin for a total duration of 6 weeks. She was followed up as an outpatient and did well.

Figure 1: Blood agar plate showing colonies of Erysipelothrix rhusiopathiae (Case 1)

Case 2

A 55-year-old male supervisor in the sanitation department presented with chief complaints of high-grade fever and severe headache for 1 day. The fever was high grade and associated with chills, rigors, generalized body pain, and headache. He gave a history of a boil in the left leg and swelling and redness, which preceded the fever by 2 days. He had applied manual pressure and expressed the pus out, following which it developed into a small nonhealing ulcer. There was no history of similar lesions elsewhere on the body, no painful inguinal swelling. No other localizing symptoms were present. He, however, gave a history of working throughout the monsoon season in the sanitation department supervising garbage collection and disposal. There was also a history of poor hygiene practices involving his feet. Social history included regular alcohol consumption for the past 10 years, with current consumption just before the onset of fever. There was no significant past medical history.

On examination, he was hemodynamically stable and febrile. Physical examination was normal except for hepatomegaly and an ulcer on the lateral malleolus of the left leg [Figure 2]. The lesion was not warm or tender, and there was no active oozing or bleeding.

Figure 2: Ulcer over the foot (Case 2)

Basic blood investigations showed neutrophilia and thrombocytopenia, predominantly conjugated hyperbilirubinemia, mild transaminitis, and elevated creatinine of 2.1 mg/dL. The urine routine was within normal limits. COVID-19 RT-PCR was negative.

IV cefoperazone-sulbactam and doxycycline were started empirically after drawing blood for culture and sensitivity. He was treated with thiamine, ursodeoxycholic acid, and IV fluids. He was symptomatically better and was afebrile within 48 h of starting antibiotics. Blood culture showed the growth of E. rhusiopathiae [Figures 3 and 4]. Drug susceptibility patterns showed sensitivity to penicillin, erythromycin, third-generation cephalosporins, meropenem, and clindamycin. Antibiotics were changed to IV ceftriaxone 2 gm, once a day. A transesophageal echo (TEE) was done to rule out infective endocarditis, and no vegetations were found. Repeat investigations showed improvement in the serum electrolytes, liver, and renal functions. He improved clinically and was discharged after 7 days of antibiotic therapy. He was followed up as an outpatient and did well.

Figure 3: Blood agar plate showing colonies of Erysipelothrix rhusiopathiae (Case 2)

Figure 4: Gram stain × 100 showing Gram-positive bacilli-Erysipelothrix rhusiopathiae (Case 2)

DISCUSSION

E. rhusiopathiae is a genus of aerobic, nonsporing, nonmotile, Gram-positive bacillus and is primarily a zoonotic pathogen.^[1] Human infections are rare and are usually associated with animal exposure.^[2] Various wild and domestic animals, including fish and birds, may shed E. rhusiopathiae, but the swine are the most crucial reservoir.^[3] In the absence of occupational exposures, invasive E. rhusiopathiae infection risk factors include immunocompromising conditions, such as chronic kidney disease, diabetes mellitus, and treatment with high-dose steroids. Major virulence factors in the pathogenesis are surface protective antigen, capsule polysaccharide gene (cpsA-C), rhusiopathiae surface protein (rspA and rspB), hyaluronidase (hylA-C), neuraminidase (nanH.1 and nanH.2), and adhesin.^[4] Around 200 human infections have been reported so far worldwide.^[2,5] To the best of our knowledge, three cases of Erysipelothrix infection have been reported so far from India.^[6–8] In this report, two cases of E. rhusiopathiae infection with unique clinical features are presented.

Human infections can manifest in one of the following three forms: (i) a localized cutaneous lesion or erysipeloid, (ii) a generalized cutaneous form, and (iii) a septicemic form, which is associated with infectious endocarditis.^[9]

The first patient in our report (Case 1) presented with prolonged fever and had a history of cut injury with a fishbone before the illness. She was also immunocompromised with a background of SLE and lupus nephritis. In past literature, reported cases of E. rhusiopathiae endocarditis had shown a proclivity towards the aortic valve, and there is a male predilection.^[10,11] There are few reported cases of tricuspid valve involvement in the past and only one case explicitly involving the tricuspid valve.^[12,13] Our case is a young female with multiple vegetations on the tricuspid valve, an unusual presentation of this rare organism.

The second patient in our report (Case 2), who presented with fever and a small nonhealing ulcer on his foot, had no significant animal exposure. He did not have any other risk factors except for chronic alcoholism. He had a history of a small boil on his leg preceding the illness, which might have been the source of the infection. This patient grew E. rhusiopathiae in two sets of blood cultures. However, there was no evidence of endocarditis on TEE. E. rhusiopathiae bloodstream infection (BSI) was thought to have a high incidence (close to 90%) of endocarditis, but Tan et al. believe that it is due to case bias and underreporting of E. rhusiopathiae BSI without endocarditis.^[14] Our case is bacteremia without endocarditis. Very few cases of bacteremia without endocarditis have been reported in the past.^[15] There are also case reports regarding E. rhusiopathiae-related septic arthritis, prosthetic joint infection, and osteomyelitis. However, none of them was associated with endocarditis.^[16]

E. rhusiopathiae differs from most other Gram-positive organisms due to its intrinsic resistance to vancomycin, one of the initial regimens for Gram-positive bacteremia. The isolates from our patients were susceptible to penicillin, ceftriaxone, carbapenems, and clindamycin. Both the patients were treated successfully with an injection of ceftriaxone. These susceptibility patterns are in accordance with prior reports.^[17] Venditti et al. tested ten isolates of E. rhusiopathiae (nine swine isolates and one human isolate) and found that penicillin and imipenem were the most effective antimicrobials. Clindamycin and fluoroquinolone are suitable alternatives.^[18]

CONCLUSIONS

E. rhusiopathiae is a zoonotic infection-causing various localized and diffused skin diseases, including bacteremia with or without endocarditis. Our cases emphasize the unusual presentation of this rare pathogen in the immunocompetent and immunosuppressed host. E. rhusiopathiae is intrinsically resistant to vancomycin, the usual first-line drug for Gram-positive organisms. Clinicians should be aware of this rare and yet important microorganism for better management of patients.

Declaration of patient consent

The patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published and due efforts will be made to conceal his identity, but anonymity cannot be guaranteed.

Research quality and ethics statement

The authors followed applicable EQUATOR Network guidelines (http://www.equator-network.org/), notably the CARE guidelines, during the conduct of this report.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.