Discarded old antibiotics as a new arsenal for multi-resistant isolates in diabetic foot ulcer infections: Therapeutic value of parenteral Colistin versus multi-resistant Pseudomonas speciesisolate strains. Case Report

Abstract Background Antimicrobial resistance to current novel antibiotics is posing a major threat to both human and zoonotic life. This poses a serious potential of rolling back to pre-antibiotic era clinical settings. Antimicrobial discovery pipeline has dried up as major pharmaceutical brands have shifted to long term chronic illness drugs production. In the absence of new novel antibiotics molecules, clinicians have resorted into a desperate last resort to review and re-introduce prior discarded antibiotics as their new weaponry in the fight against multi-resistant Gram-negative bacteria. Case presentation: We report a case of a 77 years old bed ridden diabetic and hypertensive with renal impairment diagnosed with bilateral lower limbs wet gangrene. She underwent transfemoral on her right and transtibial amputation on her left lower limb. She developed Surgical site infection on her right stump and wet gangrene on her left stump. Surgical toilet, debridement and stump revision was done on her right stump and a transfemoral amputation on her left lower limb. Pus swab on her right stump revealed carbapenem resistant strains of Pseudomonas aeruginosa. She was instituted on parenteral colistin and showed no bacterial growth 7 days post treatment. She suffered an ischaemic cerebral vaso-occlusive stroke during her hospital stay. CT angiography revealed distal infra-renal abdominal aorta multiple calcified plaques, multiple calcified plaques and completely obstructing thrombus both on common and external iliac arteries, seen downstream to both superficial femoral arteries with multiple collaterals in both thighs. The included portion of the lower lung fields showed a large filling defect in the right main pulmonary artery extending to the lower lobe branches suggestive of right-sided pulmonary embolism. She developed hypostatic pneumonia, bed sores and her condition deteriorated and she unfortunately succumbed from her comorbidities. Despite our patient succumbing to her multiple co-morbidities we report this case to highlight the isolation of carbapenem resistant strains of Pseudomonas aeruginosa and the efficacy and safety of colistin as a salvage antibiotic in renal impaired patients. Conclusions Colistin can be safely used as a last reserve antibiotic for multi-resistant strains of Pseudomonas aeruginosa infection even in patients with renal impairment.