Case Report: Shewanella algae, a rare cause of osteosynthesis-associated infection

Shewanella is an emerging human pathogen. It mostly causes skin and soft tissue infections. Osteosynthesis-associated infection involving Shewanella are rare and in most cases are secondary to direct contamination following open fractures in aquatic environments. Here, we present a rare case of hematogenous osteosynthesis-associated infection involving Shewanella algae affecting an 18-year-old patient who was operated on for 12 th thoracic vertebrae and 4th lumbar vertebrae fractures occurring in an aquatic environment. We performed surgical debridement with subsequent double course parenteral antibiotherapy that was then adapted to bacteria sensitivities for three weeks. After a follow-up of six months, the patient had no signs of recurrent infection. The presence of infected dermabrasions and the concordance between germs isolated in operative samples and in blood cultures presumes that the contamination was hematogenous.


Background
Shewanella is an aquatic Gram-negative bacillus and is widely found throughout the environment.The most commonly reported clinical presentation is skin and soft tissue infection, [1][2][3] often preceded by exposure to seawater. 4Bacteremia is often found in premature neonates with congenital pneumonia, patients with infections of the soft tissues of the lower limbs and with underlying health issues such as chemical esophagitis, cholangitis and liver abscess. 57][8][9] We report the first case of osteosynthesis-associated infection caused by Shewanella algae via haemathogenic route.

Case presentation
An 18-year-old patient with no previous medical history of note was admitted to the intensive care unit after he fell into a well resulting in polytrauma.In addition to head and thoracic injuries, the whole body CT revealed a burst fracture of 12 th thoracic vertebra with section of the spinal cord and complete paraplegia, burst fracture of 4 th lumbar vertebra (Figure 1).Both fractures were closed.In cutaneous clinical examination we found multiple water-soiled dermabrasions in both legs.
The patient was reoperated on the 11 th post-operative day.Intraoperatively, we found abundant pus with infected necrotic tissues that were then cleaned and debrided.We took five deep bacteriological samples.The operative wound

REVISED Amendments from Version 1
In this second version of the article, we have emphasized in the presentation of the case that it was a closed fracture of the thoraco-lumbar spine associated with dermabrasions on both lower limbs, thus supporting our theory of hematogenous infection.We also specified the method used to identify this bacterial species.
was closed on aspiratifs Redon drain.One of the blood cultures became positive, Gram staining performed from culture showed Gram-negative rods.They were identified as Shewenella algae by vitek 2. Intraoperative deep tissue specimens grew Shewanella algae and Klebsiella pneumoniae.Shewanella algae was resistant to amoxicillin, amoxicillinclavulanic acid and levofloxacin, had intermediate susceptibility to trimethoprim-sulfamethoxazole and was sensitive to imipenem/cilastatin. Klebsiella pneumoniae was multi-resistant and was only sensitive to colistin.The patient had a double course of parenteral antibiotics (Imipenem/cilastatin at a dose of 500/500 mg/6 hours and colistin at a dose of 3 MUI/8 hours) for 25 days.The patient had minor adverse events such as epigastralgia and vomiting, which resolved with symptomatic treatment.
After three weeks of antibiotics, white cell count and C-reactive protein normalized.The surgical wound healed with no fistula.The patient was addressed to physical medicine and rehabilitation department.At eight months follow-up, the patient had no signs of recurrent infection.

Discussion
Shewanella has been regarded as an uncommon source of human infection.Despite being identified more than 70 years ago, 1 our understanding of the bacterium's spread and the symptoms it causes comes primarily from a restricted set of individual case studies.Predominantly concentrated in tropical regions, the highest frequency of occurrences is noted within Southeast Asia, Southern Europe, and Africa. 10They naturally exist in various environments like water of all types, raw fish, oily food, and soils. 2,5Human infections involve Shewanella algae, putrefaciens, halitosis, and xiamenensis.2][13][14] The route of infection is more likely cutaneous (wounds, leg ulcers, etc.), and, less frequently hepatobiliary or respiratory. 156][17] Although the patient received routine preoperative antibioprophylaxis based on 2 g of cefazolin and had no medical history, he developed infection.
In this case, Klebsiella pneumoniae was co-isolated in deep bacteriological samples.In fact, Shewanella algae are frequently identified in polymicrobial infections and the most common bacterial strains co-isolated are Enterobacteriaceae and marine flora bacteria. 2ses of osteosynthesis-associated infection caused by Shewanella are rare.In our review of the literature, all cases were secondary to open fractures of lower limbs occurring in an aquatic environment. 6,8,9,18To the best of our knowledge, this is the first case in which osteosynthesis implant contamination was secondary to bacteremia.Shewanella algae have a significant ability to haematogenous diffusion.Indeed, Vignier 9 and Yousfi 19 observed that bacteremia occurred in respectively 28% and 18% of the cases they studied.Mortality rates were respectively 13 and eight per cent.1][22][23] The concordance between germs isolated in operative samples and in blood cultures presumes that the contamination was haematogenous, probably originating from infected dermabrasions in both legs.
As in other cases of osteosynthesis-associated infection reported in the literature, we performed surgical debridement with subsequent double course parenteral antibiotherapy that was then adapted to bacteria sensitivities.Colistin was selected because it was the only effective antibiotic against Klebsiella pneumonae.Imipenem/cilastatin was the only antibiotic available in the hospital to which Shewanella was sensitive.Typically, Shewanella displays susceptibility to erythromycin, fluoroquinolones, chloramphenicol, third and fourth generation cephalosporins, aminoglycosides, carbapenems, and to some degree, trimethoprim-sulfamethoxazole and tetracyclines.However, it exhibits resistance against first and second generation cephalosporins, penicillin, and colistin. 24An emergence of resistance has been documented towards imipenem and piperacillin/tazobactam, which can be attributed to the presence of the class D beta-lactamase enzyme. 23Hopefully, our microbial stain was sensitive to imipenem/cilastatin.Currently, there are no established guidelines for the management of shewanella infections.However, certain reports have indicated that addressing Shewanella infections may necessitate a proactive approach involving both surgical debridement and administration of appropriate antimicrobial agents.This particular case underscores the importance of recognizing Shewanella algae as a potential offending pathogen in osteosynthesis-associated infection coming within the framework of secondary hematogenous infection even in patients without significant underlying medical conditions.

Consent
Written informed consent for publication of clinical details and clinical images was obtained from the patient.by a relatively rare pathogen, but one for which there is a growing number of There have been only a few cases reported in the literature in recent years.

General comments:
-Quality of presentation and structure of the manuscript: Satisfactory -To what extent are the conclusions supported by the data:Satisfactory -Do you have any concerns about possible image manipulation, plagiarism or any other unethical practice?: No -If this manuscript involves human and/or animal work, have the subjects been treated ethically and have the authors followed appropriate guidelines?: Yes specific comments: -authors should specify in their report the method used to identify this bacterial species (maldi-tof or classical method...) -why did the authors speak of contamination via the blood-borne route, when the patient had open fractures exposed to aquatic, saprophytic and cutaneous flora?It may be that the osteosynthesis material was contaminated at the time of insertion and then infected, giving rise to bacteremia at the starting point of the osteosynthesis material.clarification is required in this case.

Are enough details provided of any physical examination and diagnostic tests, treatment given and outcomes? Partly
Is sufficient discussion included of the importance of the findings and their relevance to future understanding of disease processes, diagnosis or treatment?Yes

Is the case presented with sufficient detail to be useful for other practitioners? Yes
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: medical microbiologymolecular biologyinfectious diseases I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.

Sofiane Masmoudi
Dear Dr Elmostafa, Thank you for reviewing our article.Your constructive comments made us aware of the lack of precision in certain aspects of our article.Indeed, it enabled us to give more details about microbiological techniques used to identify germs.Regarding your question about our theory of hemothogenic contamination, we have retained this theory given that the case involved a closed fracture of the thoracolumbar spine associated with water soiled dermabrations at a distance (on the both lower limbs) and the identification of shewanella algae on blood cultures.in this second version of the article, we have emphasized these elements in order to make the clinical case clearer for the reader.Masmoudi et al presents a case of Shewanella algae osteosynthesis-associated infection with the specificity that the pathogen was isolated in blood culture.They describe well the sequence that resulted in the infection, and their hypothesis is sound.English is good, the manuscript is well written and easy to read.I don't see any issue to be addressed.

Are enough details provided of any physical examination and diagnostic tests, treatment given and outcomes? Yes
Is sufficient discussion included of the importance of the findings and their relevance to future understanding of disease processes, diagnosis or treatment?Yes Is the case presented with sufficient detail to be useful for other practitioners?

Figure 1 .
Figure 1.CT scan showing a burst fracture of 12 th thoracic vertebra and the 4 th lumbar vertebra.

Figure 3 .
Figure 3.A clinical photograph of the surgical wound showing inflammatory signs with serous discharge.

Competing Interests:
No competing interests were disclosed.Reviewer Report 11 June 2024 https://doi.org/10.5256/f1000research.155595.r272741© 2024 Beraud G.This is an open access peer review report distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Guillaume Beraud 1 University Hospital of Poitiers, Poitiers, France 2 University Hospital of Poitiers, Poitiers, France