Erysipelothrix rhusiopathiae cellulitis with associated bacteraemia following seafood preparation

Abstract

Erysipelothrix rhusiopathiae is a pleomorphic Gram-positive bacillus, zoonotic pathogen of mammals, birds and fish. Human disease caused by this organism most commonly occurs following occupational or recreational exposure to infected animals and typically presents as a localised cutaneous disease. Invasive infection resulting in bacteraemia, endocarditis or other distant sequelae is infrequently seen. Most commonly, invasive infection is seen in patients with predisposing risk factors including diabetes, immunocompromising conditions, alcohol use disorder or chronic kidney disease. The organism is highly susceptible to penicillin-class drugs which serve as first-line antimicrobial therapy with prolonged courses typically prescribed for invasive disease, given the predilection of this organism to cause endocarditis. In this report, we present an interesting case of a polymicrobial finger abscess with E. rhusiopathiae bacteraemia following laceration with a fish spine in an immunocompetent patient in Southern US state. This bacteraemic episode was successfully treated with a fluoroquinolone course owing to patient’s penicillin allergy.

Background

Erysipelothrix rhusiopathiae is a zoonotic pathogen of mammals, birds and fish that produces a diverse array of manifestations in infected animals including localised cutaneous lesions, bacteraemia and endocarditis.¹ Infected animals shed organisms in both urine and faeces, which can then be transmitted to human hosts through direct contact via breaks in skin, most commonly seen following occupational or recreational exposure to infected animals. Within human hosts, E. rhusiopathiae typically causes a self-limited localised cutaneous disease but can progress to an invasive bacteraemic variant occasionally associated with endocarditis.¹ In this report, we present an interesting case of a polymicrobial finger abscess with E. rhusiopathiae bacteraemia following laceration with a fish spine in an immunocompetent patient.

Case presentation

A woman in her 60s with a medical history of tobacco use and type I hypersensitivity reaction to penicillin presented to our emergency department with worsening right index finger pain for 1 week and a day of fevers following a puncture injury. The patient reported that she initially punctured her finger 1 week prior while deboning and cleaning redfish (Sciaenops ocellatus) purchased from a local market after a spine from a fin lodged in her finger (figure 1). The small puncture wound developed into a fluctuant violaceous lesion with surrounding cellulitis over the following few days, prompting the patient to attempt an incision and drainage of the wound at home. Using a knife from her kitchen which had been cleaned with soap and water, she made a small incision over the lesion with an expression of minimal purulence. She attempted to remove the small piece of fin retained in the wound unsuccessfully. Over the following 24 hours, she developed fevers, rigours and malaise in addition to worsening pain and swelling of her more proximal arm, prompting presentation to our emergency department.

Figure 1.

Necrotic wound to right index finger on day of admission.

On arrival in the emergency department, she was noted to be febrile (40°C) but was otherwise haemodynamically stable. Examination revealed a swollen, tender right second digit with a 1 cm purpuric papule at the site of her puncture wound without active drainage (figure 1). Laboratory evaluation was remarkable for a leucocytosis of 14 800 cells/µL (normal range 4500–11 000 cells/µL), normal serum lactic acid and elevated inflammatory markers with an erythrocyte sedimentation rate (ESR) of 34 mm/hour (normal<29 mm/hour) and C reactive protein (CRP) of 5 mg/dL (normal<1.0 mg/dL). Blood cultures were drawn, and the patient was started on empiric vancomycin, cefepime and doxycycline to cover possible skin and soft tissue infection with exposure to fish from regional brackish water. Plastic surgery performed incision and debridement of the wound at the bedside to obtain cultures using aseptic technique. MRI of the hand was concurrently performed that was unremarkable apart from diffuse soft tissue oedema of the affected digit consistent with cellulitis without evidence of osteomyelitis or abscess. Tetanus vaccine was given. Defervescence and resolution of leucocytosis occurred within the first 24 hours of admission on antimicrobial therapy.

On day 2 of admission, blood cultures from presentation resulted as positive for Gram-positive bacilli in four of four bottles with alpha-haemolytic colonies on blood agar (figure 2A–C). Ultimately on day 3 of admission, organism identity was confirmed as E. rhusiopathiae via matrix-assisted laser desorption/ionization–time of flight (MALDI–TOF) mass spectrometry. Repeat blood cultures from day 2 remained sterile indicating clearance on therapy. Concurrent wound cultures also grew the same pathogen as well as Enterobacter cloacae complex confirmed by MALDI–TOF mass spectrometry. Given the historical association of E. rhusiopathiae with endocarditis, a transthoracic echocardiogram was obtained that revealed no evidence of vegetation or valve dysfunction. Cardiology declined to perform transoesophageal echocardiogram because they could see all four valves well on the transthoracic echocardiogram and the patient did not want to have another procedure or stay longer for one due to her lack of health insurance.

Figure 2.

(A,B) Small, alpha-haemolytic colonies of Erysipelothrix rhusiopathiae growing on 5% sheep blood agar after 3 days of incubation. (C) Gram stain of positive blood culture demonstrating Gram-positive bacilli.

Infectious diseases were consulted given the rarity of the organism and antibiotic therapy was narrowed to cefepime monotherapy. Disposition was complicated by the patient’s history of type I hypersensitivity allergy to penicillin and lack of health insurance, which rendered home intravenous antibiotic therapy financially prohibitive. Ultimately, it was decided to discharge the patient with 4 weeks of oral ciprofloxacin 750 mg every 12 hours for her polymicrobial cellulitis and transient bacteraemia as both organisms were susceptible to this agent with a minimum inhibitory concentration (MIC) of <0.25 µg/mL. Plastic surgery recommended no further intervention, as the wound was healing well with no further purulence. At the time of discharge on day 4 of admission, the patient was afebrile, with no leucocytosis, and felt at her baseline state of health.

Investigations

Laboratory evaluation was remarkable for a leucocytosis of 14 800 cells/µL (normal range 4500–11 000 cells/µL), normal serum lactic acid and elevated inflammatory markers with an ESR of 34 mm/hour (normal<29 mm/hour) and CRP of 5 mg/dL (normal<1.0 mg/dL). Blood cultures were drawn in the emergency room. Plastic surgery performed incision and debridement of the wound at the bedside to obtain cultures using aseptic technique. MRI of the hand was concurrently performed that was unremarkable apart from diffuse soft tissue oedema of the affected digit consistent with cellulitis without evidence of osteomyelitis or abscess.

On day 2 of admission, blood cultures from presentation resulted as positive for Gram-positive bacilli in four of four bottles with alpha-haemolytic colonies on blood agar (figure 2A–C). Ultimately on day 3 of admission, organism identity was confirmed as E. rhusiopathiae via MALDI–TOF mass spectrometry. Repeat blood cultures from day 2 remained sterile indicating clearance on therapy. Concurrent wound cultures also grew the same pathogen as well as E. cloacae complex confirmed by MALDI–TOF mass spectrometry. Given the historical association of E. rhusiopathiae with endocarditis, a transthoracic echocardiogram was obtained that revealed no evidence of vegetation or valve dysfunction.

Treatment

Antibiotic choice was complicated by the patient’s history of type I hypersensitivity allergy to penicillin and lack of health insurance, which rendered home intravenous antibiotic therapy financially prohibitive. Ultimately, it was decided to discharge the patient with 4 weeks of oral ciprofloxacin 750 mg every 12 hours for her polymicrobial cellulitis and transient bacteraemia as both organisms were susceptible to this agent with an MIC of <0.25 µg/mL.

Outcome and follow-up

In conclusion, this case represents an interesting presentation of polymicrobial finger cellulitis with associated transient E. rhusiopathiae bacteraemia in an immunocompetent patient following high risk exposure via skin laceration with a redfish spine. Southern US state hosts a large recreational fishing community, placing recreational fishermen in this region at greater risk of aquatic and zoonotic infections, such as E. rhusiopathiae. Contrary to historical literature reports, our patient was not found to have endocarditis on transthoracic echocardiography with excellent windows to assess for valvular disease. It is likely that the short course of her illness with prompt presentation to the emergency department at the onset of systemic symptoms likely prevented endovascular spread of infection. As her bacteraemia was transient and she promptly improved on empiric antibiotic therapy, her invasive disease was treated with an alternative agent based on her allergy profile and strong desire to be discharged from the hospital on oral antimicrobials. She did well on oral ciprofloxacin, which was chosen owing to its equivalent bioefficacy when compared with parenteral therapy (figure 3).

Figure 3.

Right index finger following debridement and 4 weeks of ciprofloxacin.

Discussion

E. rhusiopathiae is a pleomorphic, non-spore forming, Gram-positive bacillus known to cause localised cutaneous disease, septic arthritis, bacteraemia and endocarditis in swine, sheep, rodents, poultry and fish.¹ Erysipelothrix infection in humans remains a rare occurrence, with fewer than 200 cases reported in the medical literature to date.² Human infection is acquired via direct contact through non-intact skin with an infected animal, its secretions, or its waste following occupational exposure in veterinarians, butchers, fisherman, farmers or food handlers.³

A key factor in its pathogenicity in humans is its ability to survive in animal waste or decaying matter for several months as a saprophyte.¹

Within human hosts, E. rhusiopathiae causes three distinct clinical infectious syndromes: (1) a painful, localised, well-demarcated, violaceous lesion referred to as ‘erysipeloid’; (2) a generalised cutaneous variant consisting of numerous erysipeloid or bullous lesions; and (3) an invasive bacteraemic variant that is often associated with endocarditis.¹ Invasive disease typically stems from initial cutaneous infection in hosts with specific risk factors, including immunocompromising conditions, diabetes, chronic kidney disease or alcohol use disorder.¹

Since 2018, over 50 cases of invasive disease with bacteraemia have been documented in the literature with endocarditis as the most commonly encountered distant sequelae, although distant spread to the central nervous system, lungs, liver and musculoskeletal system have been described.² Historically, endocarditis was identified in close to 90% of invasive cases in the prior century but a more recent review notes a declining incidence of this sequela, with endocarditis complicating only 34% of bacteraemia cases, likely owing to advances in microbiologic techniques that have allowed for more prompt identification and treatment.^{4 5}

In the clinical microbiology laboratory, E. rhusiopathiae is described as a slender, non-motile, facultative anaerobic, Gram-positive bacillus that is non-acid fast and non-sporulating (figure 2C). Initial microscopic diagnosis of E. rhusiopathiae can be challenging since the pleomorphic organism takes up Gram stain reagents poorly, often initially being falsely identified as a Gram-negative organism.¹ Colonies on blood agar appear clear, circular, small and have two variations: alpha-haemolytic smooth colonies and gamma-haemolytic rough colonies (figure 2A,B).⁶ Microbiologic diagnosis can be made easily from blood cultures of bacteraemic patients but deep tissue cultures by biopsy or debridement are needed to confirm a diagnosis associated with localised cutaneous disease alone since the organisms reside in the subdermal layer of the skin.¹ Once growth has occurred in media, the organism is easily identified by most conventional automated identification systems, including MALDI–TOF mass spectrometry.³

The treatment of E. rhusiopathiae invasive infections is typically with a prolonged 4–6-week course of antimicrobial therapy tailored to final culture results, given historical concerns regarding the high probability of concurrent endovascular infection. First-line therapy is typically a penicillin-class agent, given nearly universal susceptibility to these drugs.⁷ Acceptable alternative therapies used in the medical literature have included third-generation cephalosporins, clindamycin and fluoroquinolones.³ Notably, the organism is intrinsically resistant to vancomycin, aminoglycosides, trimethoprim–sulfamethoxazole and polymyxins.⁷ Given the frequent association of invasive disease with endocarditis, transthoracic and possibly transoesophageal echocardiography are recommended to exclude endocarditis prior to ascribing a treatment duration.

Learning points.

• Erysipelothrix rhusiopathiae is a pleomorphic Gram-positive bacillus, zoonotic pathogen of mammals, birds and fish that causes skin and soft tissue infections and rare invasive bacteraemic infections in human hosts.

• Infection follows contact of non-intact skin with infected animals, their secretions or waste products and most commonly occurs following occupational exposure in veterinarians, butchers, fisherman, farmers and food handlers.

• Echocardiography is important to exclude endocarditis in invasive disease, given concurrent valve infection noted in 34% of bacteraemic cases per a recent review.

• Penicillin-class agents are first-line antimicrobial therapy owing to near-universal susceptibility with cephalosporins and fluoroquinolones noted to be acceptable alternatives. Erysipelothrix is notably resistant to vancomycin.

Ethics statements

Patient consent for publication

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