Topic: Shewanella species: Case series on a rare emerging pathogen

Abstract

Introduction: Shewanella is a gram negative marine bacterium of which S. putrefaciens and S. algae are pathogenic in immunocompromised patients and patients with pre-existing chronic ulcers. They can cause a broad range of human infections. Aims and Objectives: To describe four cases of Shewanella infection in susceptible patients. Materials and Mehtods: Shewanella algae was isolated from blood (2) and pus (2) of four patients admitted to the ward. The first case was an 18 year old female, known case of osteomyelitis following hip fracture surgery 12 years back. She presented with discharging sinus from the surgical site which grew Shewanella algae repeatedly. The second case was a 38 years old male patient with history of trauma to left knee at a beach. He was operatedand intra-op tissue grew Shewanella algae resistant to 3rd generation cephalosporins and susceptible to quinolones, aminoglycoside, carbapenems and piperacillin-tazobactam. Both patients were successfully treated based on the AMST profile. The other two cases were dialysis patients from whom Shewanella putrefaciens was isolated from blood. The isolate had similar antibiogram being resistant to quinolones, 3rd generation cephalosporins, carbapenem and aztreonam and susceptible to piperacillin-tazobactam, cefepime, aminoglycosides & polymyxin. One of the patients expired while the other patient was successfully treated based on AMST profile. Conclusion: Isolation of Shewanella species from invasive specimen highlights importance of this organism as an emerging pathogen. Though it is known to be sensitive, in the mentioned study, Shewanella algae was resistant to 3rd generation cephalosporins or fluoroquinolones and Shewanella putrefaciens was multi-drug resistant including to carbapenems. Keywords: Shewanella, Opportunistic pathogen, Bacteremias, Skin and soft tissue infection, Shewanella algae, Shewanella putrefaciens.