EFFICACY OF DAPTOMYCIN FOR VANCOMYCIN-REFRACTORY METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS SEPSIS ASSOCIATED WITH VENOUS HYPERTENSION IN VASCULAR ACCESS -A CASE REPORT-

Methicillin-resistant staphylococcus aureus (MRSA) is one of the major causes of hospital-acquired infections, and in recent years, its susceptibility to various anti-MRSA drugs has been reported to be declining. Vancomycin (VCM)-resistant MRSA infections are thought to be caused by poor drug penetration into deep tissue infections and resistant strains. Daptomycin (DAP) has strong bactericidal activity and is considered a useful option for treating refractory infections.

A case in which long-term administration of DAP was effective for VCM-resistant MRSA sepsis triggered by vascular access (VA) venous hypertension and skin erosion was observed. We report the clinical course with a discussion.

The patient was a 79-year-old man who had been diagnosed with chronic kidney disease (CKD) underlying hypertensive nephrosclerosis for the past nine years. Two years ago, an aortic arch total replacement was performed for aortic dissection. Due to the progression of CKD, an arteriovenous fistula (AVF) was created in the left forearm five months ago. Swelling and skin erosion of the left upper limb appeared soon after surgery. Two months ago, hemodialysis was initiated. He was transferred to our hospital for rehabilitation of disuse atrophy. The left upper limb had severe edema and skin damage, making the puncture procedure difficult. Imaging findings indicated a thrombus at the confluence of the left internal jugular vein and subclavian vein, and it was also suggested that the left brachiocephalic vein may have been severed during a major vascular surgery. The patient was diagnosed with intractable edema associated with central venous hypertension, and the left AVF was closed and an arteriovenous graft was inserted newly in the right upper extremity. Postoperatively, the patient developed a high fever, and blood cultures revealed MRSA. A periaortic graft abscess and septic pulmonary embolism were present. Surgical approach was difficult, and conservative treatment with VCM for two weeks failed to produce a clinical response. Therefore, the antibiotic was changed to DAP and rifampicin (RFP) was administered in combination. After the antibiotic modification, blood cultures became negative, and fever and inflammatory response improved. DAP was administered for eight weeks, and the abscess shrank and the pulmonary embolism disappeared. After switching to oral minocycline (MINO), there was no relapse, and the patient was discharged five months after admission. This case showed VCM-resistant MRSA sepsis. Drug susceptibility testing presented a minimum inhibitory concentration of 0.5-1.0 ug/mL, indicating no VCM resistance. In addition, trough levels were maintained at around 15 ug/mL, suggesting that the dosage was appropriate. In cases of bloodstream infections involving artificial blood vessels where surgical removal is difficult, MRSA may form a biofilm on the surface of the artificial vessel, which is resistant to conventional treatment. DAP has been reported to be highly effective in sterilizing MRSA within biofilms, and in this case, altering the anti-MRSA drug was thought to be successful. Combination use of RFP and MINO has also been reported to be useful. DAP is affected by pulmonary surfactant and therefore not indicated for respiratory infections, but these findings suggest it may be effective for septic pulmonary embolism. Venous hypertension and skin erosion in the VA were suspected as causes of MRSA sepsis. Since changes in central venous patency may occur after major vascular surgery, careful consideration is required for the location of VA creation.

These results indicate that DAP may be an effective treatment option for VCM-resistant MRSA sepsis associated with artificial materials.