Bilateral cellulitis with lymphangitis, caused by Shewanella algae, after travel to the Cook Islands

A 68-year-old Cook Island Māori man presented to the emergency department with 4 days of fevers, bilateral leg pain, swelling and blistering, without preceding injury. He had recently returned from the Cook Islands, where he visited family.

His background included cardiomyopathy with an implanted cardiac resynchronisation device in situ, poorly controlled type 2 diabetes mellitus, obesity, stage 4 chronic kidney disease, gout and historic colonisation with extended-spectrum beta-lactamase–producing Escherichia coli (E. coli).

At presentation, he was hypotensive (90/56mmHg), febrile (38.2 degrees Celsius) and tachypnoeic (20/min). There was markedly tender bilateral erythema up to the proximal calves and linear erythema tracking up to the groin, consistent with cellulitis and lymphangitis. Chronic venous changes were evident bilaterally. There was no crepitus. He had generally poor skin quality in his lower limbs, as well as areas of distal paraesthesia, felt secondary to his diabetes.

Initial blood tests showed a marked inflammatory response with acute kidney injury (see Appendix Table 1).

Three sets of peripheral blood cultures were obtained pre-treatment. Broad-spectrum antibiotics were commenced (ceftriaxone, clindamycin and vancomycin) due to pain deemed out of proportion with clinical findings. However, further serial clinical review discounted the likelihood of a necrotising soft tissue infection. Overnight, all three sets of cultures isolated Gram-negative bacilli. Subsequent review by the infectious diseases team led to a recommendation to change ceftriaxone to meropenem.

On further enquiry, he denied seawater immersion or coral injury while in the Cook Islands, though he had stayed in a coastal area of an outer Cook Island. He had, however, consumed raw fish.

The blood culture isolates were subsequently identified as Shewanella algae (S. algae), susceptible to ceftazidime, ciprofloxacin, gentamicin, trimethoprim-sulfamethoxazole and piperacillin-tazobactam; antibiotic treatment was rationalised thereafter (see Appendix Table 1). The patient completed 10 days of treatment, with improving symptoms, before being discharged. Unfortunately, due to poor tissue healing in the setting of his diabetes and residual infection in his left foot, he was subsequently readmitted later that year with polymicrobial osteomyelitis of his left foot and ankle, leading to a left below-knee amputation. Intraoperative bone samples had mixed growth, including S. algae.

Discussion

Unlike non-infectious cellulitis mimics such as stasis dermatitis or lipodermatosclerosis, which commonly present bilaterally,³ true bilateral cellulitis remains an uncommonly described clinical entity, with scattered case reports over the last three decades.⁴

Local data^1,2 describe unilateral involvement in most cellulitis cases, though one retrospective study noted 16% of cases were described as bilateral;² how these were judged to be instances of “true” bilateral cellulitis is not detailed. Prospective diagnostic aids (the ALT-70 Score for Cellulitis and the New HAvUN criteria) score against cellulitis if there is bilateral limb involvement.⁵

Mechanistically, it is conceivable, although unlikely, that bacterial invasion through a skin breach, leading to cellulitis,³ could occur near-simultaneously in both limbs. A more commonly implicated mechanism for bilateral cellulitis is secondary to haematogenous spread to the lower limbs from another primary site (i.e., after gastrointestinal invasion).⁴

Beta-haemolytic streptococci, primarily Streptococcus dysgalactiae and Streptococcus pyogenes, are the leading causes of non-purulent cellulitis.^3,6 In contrast, available literature on bilateral cellulitis identifies a more diverse range of pathogens.⁴ Shewanella are Gram-negative bacteria found in aquatic environments.³ Most infections are caused by S. algae and Shewanella putrefaciens.⁷ Clinical syndromes caused by Shewanella overlap with those of Vibrio—highlighted as a cause of bilateral cellulitis⁴—and other environmental Gram-negative bacteria,^7–9 including skin and soft tissue infections and bacteraemia.

Locally acquired Shewanella infections have only been reported twice in Aotearoa New Zealand: a case from the Bay of Plenty describes unilateral lower limb cellulitis¹⁰ after lacerations were sustained from a fishing bin in local waters, and another case from the Rotorua Lakes District¹¹ after freshwater exposure. International literature regarding Shewanella infections in general—including skin and soft-tissue, bacteraemia, and visceral infections—describes preceding water exposure across all infectious clinical syndromes,⁷ though recent studies from Northern Australia⁸ and Hong Kong⁹ found this association less consistent, with the caveat of retrospective determination of water exposure from available documentation. Interestingly, contaminated seafood ingestion was posited to be an explanation for the relatively large number of cases seen in Hong Kong.⁹

It was thought that the likely route of infection for our patient was gut translocation of S. algae with subsequent haematogenous dissemination to the lower limbs, secondary to ingestion of raw fish. An alternative hypothesis was near-simultaneous inoculation of both lower limbs by sea or by shower water.

Conclusion

True bilateral cellulitis is an uncommon clinical entity, but it may occur via haematogenous dissemination or near-simultaneous inoculation of both limbs. Bilateral cellulitis should not be discounted as a cellulitis “mimic” in the presence of sepsis. Recent travel, aquatic exposure and seafood ingestion should be routinely considered risk factors for uncommon causes of cellulitis that may be resistant to standard empiric antibiotic treatment, such as Shewanella.

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