Leclercia adecarboxylata causing necrotising soft tissue infection in an immunocompetent adult
- 1 School of Medicine, Uniformed Services University of the Health Sciences F Edward Hebert School of Medicine, Bethesda, Maryland, USA
- 2 General Surgery, Madigan Army Medical Center, Tacoma, Washington, USA
- Correspondence to Dr Cody J Phillips; cjphillips10@gmail.com
Abstract
A 72-year-old woman presented with concern for a necrotising soft tissue infection (NSTI) 6 days after a tree branch impaled her left lower extremity while hiking in Hawaii. The wound was irrigated and closed at a local clinic in Hawaii. She completed a 5-day course of clindamycin. She presented to our emergency department 1 day after completion of antibiotics due to worsening erythema and malodorous drainage. Local wound exploration revealed bullae and easy dissection of fascial planes. CT scan revealed complex heterogeneous fluid and inflammatory stranding in the posterior calf. Clinical and radiographic findings raised concern for NSTI prompting initiation of broad spectrum antibiotics and urgent operative debridement. Wound cultures and deep tissues cultures returned positive for pansusceptible Leclercia adecarboxylata. She underwent two additional operative debridements and transitioned to negative pressure wound therapy during her hospitalisation. She was discharged home on oral amoxicillin/clavulanate on hospital day 6.
Background
Leclercia adecarboxylata is a motile, lactose-fermenting, gram-negative rod and a member of the Enterobacteriaceae family found in the normal gut flora of animals and humans. First described by Leclerc, historically it has been an uncommon human pathogen, except in immunocompromised hosts.1–4 . However, recent case reports suggest L. adecarboxylata has the pathogenicity to cause a wide variety of infections in immunocompetent individuals ranging in severity from folliculitis to septic shock and death after cholecystitis.4 5 L. adecarboxylata has previously been isolated from wounds including two instances of Leclercia isolated from abscesses.6 To our knowledge, this case describes the first instance of a monomicrobial necrotising soft tissue infection (NSTI) caused by L. adecarboxylata. All identified human cases of L. adecarboxylata have been pansensitive and therefore treatable with antibiotics that provide broad gram-negative coverage. Given that the true pathogenicity of this bacteria is still unknown, proper identification and appropriate antibiotic coverage are important to prevent the emergence of antimicrobial resistance.7 8
Case presentation
A 72-year-old woman with a medical history of hypertension, non-steroid dependent asthma and hypothyroidism presented to our emergency department (ED) 6 days after sustaining a wound to her left calf. She was hiking on a lava field in Hawaii when she lost her footing and impaled her leg on a ground-level tree branch. Both the soft tissue and fascia of her left posterior calf were involved (figure 1). The wound was irrigated with saline at the local ED and closed with nylon sutures. She was discharged with a 5-day course of oral clindamycin. Over the following days, erythema developed along the borders of the laceration. On arrival to Washington state on postinjury day 6, bullae and foetid fluid drainage had developed prompting her presentation to the ED.
Image showing the initial laceration wound.
On arrival she was afebrile, with a heart rate of 96 and a blood pressure of 186/90. She was awake and alert; the previously closed wound on the posteromedial aspect of her left calf had expanding erythema and blistering along the wound edges (figure 2). Dishwater appearing fluid was present, and she was tender to palpation. Examination did not reveal pain out of proportion or crepitus. Local wound exploration was significant for easy dissection along the fascial planes and the decision to take her to the operating room (OR) was made.
Image showing the wound 12 hours prior to patient presentation in our emergency department.
Investigations
An X-ray showed no evidence of associated fracture or air in the tissues. Contrasted CT scan performed in the ED demonstrated a heterogeneous fluid collection with irregular margins measuring approximately 1.1×3.8×4.9 cm in the posterior calf abuting the underlying calf musculature. There was surrounding diffuse soft tissue inflammation without evidence of air (figure 3). Cultures of the wound were performed in the ED. Calculated LRINEC score of 1. Laboratory values at the time of presentation are listed below:
CT image demonstrating approximately 1.1×3.8×4.9 cm area of heterogeneous fluid collection, (white arrows) with irregular margins in the posterior calf abuting the underlying calf musculature.
Erythrocyte sedimentation rate (ESR)
59 (normal range: 0–30).
C reactive protein
2 mg/dL (normal range: 0.04–0.50).
White blood cell (WBC)
6.9 (neutrophils 74%, lymphocytes 12.8%, eosinophils 3.6%, basophils 0.9%).
Remainder of CBC within normal limits.
Basic metabolic panel
Within normal limits.
Liver function panel
Within normal limits.
Differential diagnosis
The patient was haemodynamically stable with evidence of soft tissue infection on physical exam and imaging. The wound easily separated along fascial planes during local wound exploration, and there was clear evidence of blistering necrosis of the skin causing concern for devascularised tissue versus necrotising fasciitis versus NSTI.
Treatment
The patient was started on broad-spectrum antibiotics including intravenous vancomycin, piperacillin/tazobactam, clindamycin and ciprofloxacin and taken to the OR for surgical wound debridement. This revealed that the overlying skin was completely necrotic with underlying areas of infected, necrotic, subcutaneous tissues that required debridement. There was a laceration to the soleus muscle with soft tissue loss overlying the fascia. Deep wound and tissue cultures were performed. Susceptibilities are presented in table 1. The underlying fascia and muscle appeared grossly free of infection. Following debridement, the wound measured approximately 8×10 cm. Dakin’s soaked kerlex gauze packing was used for dressings. The patient was brought to the OR the following day to evaluate for progression of the infection (figure 4A). Minimal debridement was required and a negative pressure wound vacuum was placed. Subsequent negative pressure wound vacuum changes were performed on hospital days four and six at which time the wound was partially closed using ‘Jacob’s ladder’ (Shoelace) technique.9 Cultures finalised as pan-sensitive L. adecarboxylata on hospital day 5. Antibiotics were narrowed to oral amoxicillin/clavulanate, and the patient was discharged on hospital day 6. She was discharged with ongoing negative pressure wound therapy and a Controlled Ankle Movement (CAM) boot to prevent Achilles tendon contracture. She continued on oral amoxicillin/clavulanate on discharge for a total of 10 days of antibiotic coverage.
Final susceptibility report for Leclercia adecarboxylata cultured from deep tissue sample during initial operative debridement
| Drug | L. adecarboxylata | |
| MIC* interpretation | MIC* dilution | |
| Amoxicillin/clavulanate | S | ≤2 |
| Ampicillin | S | ≤2 |
| Ampicillin/sulbactam | S | ≤2 |
| Cefepime | S | ≤1 |
| Ceftazidime | S | ≤1 |
| Ceftriaxone | S | ≤1 |
| Ciprofloxacin | S | ≤0.25 |
| Gentamicin | S | ≤1 |
| Imipenem | S | ≤0.25 |
| Levofloxacin | S | ≤0.12 |
| Piperacillin/tazobactam | S | |
| Tobramycin | S | ≤1 |
| Timethoprim/sulfamethoxazole | S | ≤20 |
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*MIC: Minimum Inhibitory Concentration
(A) Image showing extent of wound debridement approximately 24 hours after initial operation. There was no evidence of ongoing tissue necrosis or progression of infection at this time. (B) Image showing progression of wound healing during outpatient follow-up with continued use of negative pressure dressing and CAM boot. (C) Image showing ongoing healing and the result of definitive wound closure with full thickness skin graft.
Outcome and follow-up
The patient followed up for ongoing negative pressure wound therapy with excellent healing. She was without functional impairment and was able to walk without difficulty in a CAM boot. She ultimately went on to have a full thickness skin graft with full take and healing on follow-up (figure 4B,C).
Discussion
This case highlights, to our knowledge, the first reported case of L. adecarboxylata causing a NSTI in an immunocompetent individual. However, this may be due to a misclassification error, as it has similar laboratory characteristics to Escherichia coli when using traditional plating techniques (figure 5). Additionally, L. adecarboxylata was only fully genome sequenced in 2017.10 This more accurate method of identification relies on computerised identification machines, which must be kept up to date to ensure emerging pathogens, such as L. adecarboxylata, can be properly identified.11–13 On a global scale, although computerised technology is widely available in resource-rich nations, its utility is limited in resource-poor nations. The difficulty in proper identification indicates that infection due to L. adecarboxylata is likely under-recognised and subsequently under reported in medical literature. Increasingly widespread use of modern computerised identification techniques will likely aid in the proper differentiation of these two similar microbes moving forward.11–14
Image showing a side-by-side comparison of Escherichia coli (left) and Leclercia adecarboxylata (right) plated on MacConke agar. While both bacteria are lactose fermenters and thus produce pink colonies, the degree of fermentation is higher in E. coli leading to the formation of larger, darker pink colonies.
Fortunately, it seems that L. adecarboxylata has a favourable susceptibility profile. Thus, it is responsive to a number of common antibiotics. Stock et al examined the susceptibility patterns of 101 L. adecarboxylata strains and found broad sensitivity to tetracyclines, aminoglycocides, beta-lactams, quinolones, folate pathway inhibitors, chloramphenicol, nitrofurantoin and azithromycin.11 There is, however, one case report of multidrug-resistant Leclercia species among bovine herds in India.14 Out of concern for NSTI based on this patient’s initial presentation, she was treated with broad-spectrum antibiotics while undergoing initial and repeat operative debriedments. Since the patient had completed a 5-day course of clindamycin prior to presentation, there was concern for antibiotic-resistant organisms. Fortunately, susceptibility patterns from our patient were similar to those described by Stock et al,11 and she was able to complete her antibiotic treatment with oral amoxicillin/clavulanate as an outpatient.
The initial treatment of penetrating soft tissue injuries and superficial lacerations is largely defined by the mechanism of injury, the patient’s comorbidities, and the environment in which the injury occurred. Superficial lacerations become infected at a rate of 2%–5%, so there is little benefit in treating these wounds with prophylactic antibiotics at the time of initial presentation in the absence of obvious signs of infection.15 16 However, it is not uncommon to prescribe antibiotics for penetrating injuries if there is concern for retained foreign body or significant environmental contamination.15 17 The choice of antibiotics should be directed at likely causative pathogens based on the factors listed above. Although L. adecarboxylata is an unlikely pathogen to cause infection in this immunocompetent host, its similarity to E. coli suggests that physicians should give consideration to this microbe anytime there is a concern for infection with gram-negative bacteria, especially in and around aquatic environments or possible animal exposures. In this case, the patient sustained a deep penetration injury to her lower extremity from a tree branch. Thus, suspicion for infection due to gram-negative organisms such as E. coli and L. adecarboxylata, as well as Staphylococcus and Streptococcus, should be considered.18 This patient denied any direct contact with fresh or saltwater, however, given that the injury occurred near a marine environment, initial coverage for Vibrio species in a case like this should also be considered.19 Based on these factors, the initial choice of clindamycin was not adequate coverage for this patient.
Learning points
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Leclercia adecarboxylata continues to demonstrate its ability to cause various infections in immunocompetent hosts and likely has a much broader spectrum of pathogenicity than has historically been described. Modern identification techniques are likely to identify cases of significant infection with increasing frequency.
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Although current evidence suggests broad antibiotic susceptibility of L. adecarboxylata, antimicrobial stewardship must still be employed to prevent the development of resistant strains, especially given the unknown extent of this microbe’s true pathogenicity.
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While prophylactic antibiotic therapy for laceration wounds is controversial, if it is to be initiated, careful thought should be given to the pathogens likely to cause infection based on the mechanism of injury, environmental exposures and patient comorbidities.
Footnotes
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Contributors The unique nature of this case was identified by MKL who was also responsible for the literature review, writing, editing and preparation of the manuscript. RJD provided preliminary edits. CJP served as senior author and final editor.
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Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
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Competing interests None declared.
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Patient consent for publication Obtained.
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Provenance and peer review Not commissioned; externally peer reviewed.
- © BMJ Publishing Group Limited 2020. No commercial re-use. See rights and permissions. Published by BMJ.
References
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