High-Grade Staphylococcus lugdunensis Bacteremia in a Patient on Home Hemodialysis
Background: Staphylococcus lugdunensis (S lugdunensis) is a species of coagulase-negative Staphylococcus and a constituent of human skin flora. S lugdunensis has gained notoriety for its virulence, which resembles Staphylococcus aureus (S aureus). S lugdunensis is now recognized as an important nosocomial pathogen and cause of prosthetic device infections, including vascular catheter infections.
Case Presentation: A 60-year-old man with a history of uncontrolled type 2 diabetes mellitus and end-stage renal disease on home hemodialysis via arteriovenous fistula (AVF) presented to the emergency department for evaluation of subacute progressive low back pain. Initial laboratory tests were notable for elevated inflammatory markers. Magnetic resonance imaging with contrast of the thoracic and lumbar spine revealed abnormal marrow edema in the T11-T12 vertebrae with abnormal fluid signal in the T11-T12 disc space. Cultures grew methicillin-sensitive S lugdunensis. The patient’s antibiotic regimen was narrowed to IV oxacillin. He was transitioned to IV cefazolin dosed 3 times weekly after hemodialysis and an outpatient dialysis center.
Conclusions: Treatment of bacteremia caused by S lugdunensis or S aureus should be managed with prompt initiation of IV antistaphylococcal therapy, a thorough evaluation for the source of bacteremia as well as metastatic complications, and consultation with an infectious disease specialist. This case highlights AVF as a potential source for infection even without localized signs of infection. The buttonhole method of AVF cannulation was thought to be a major contributor to the development and persistence of our patient’s bacteremia. This risk should be discussed with patients using a shared decision-making approach when developing a dialysis treatment plan.
Two sets of blood cultures were obtained, and empiric IV vancomycin and ceftriaxone were started. Interventional radiology was consulted for consideration of vertebral biopsy but deferred while awaiting blood culture data. Neurosurgery also was consulted and recommended nonoperative management given his nonfocal neurologic examination and imaging without evidence of abscess. Both sets of blood cultures collected on admission later grew methicillin-sensitive S lugdunensis, a species of CoNS. A transthoracic and later transesophageal echocardiogram did not show any valvular vegetations. The patient’s antibiotic regimen was narrowed to IV oxacillin based on susceptibility data. It was later discovered that both blood cultures obtained during his outside ED encounter were also growing S lugdunensis.
The patient’s S lugdunensis bacteremia persisted for the first 8 days of his admission despite appropriate dosing of oxacillin. During this time, the patient remained afebrile with stable vital signs and a normal WBC count. Positron emission tomography was obtained to evaluate for potential sources of his persistent bacteremia. Aside from tracer uptake in the T11-T12 vertebral bodies and intervertebral disc space, no other areas showed suspicious uptake. Neurosurgery reevaluated the patient and again recommended nonoperative management. Blood cultures cleared and based on recommendations from an infectious disease specialist, the patient was transitioned to IV cefazolin dosed 3 times weekly after HD, which was transitioned to an outpatient dialysis center. The patient continued taking cefazolin for 6 weeks with subsequent improvement in back pain and normalization of inflammatory markers at outpatient follow-up.
Discussion
CoNS are a major contributor to human skin flora, a common contaminant of blood cultures, and an important cause of nosocomial bloodstream infections.1,2 These species have a predilection for forming biofilms, making CoNS a major cause of prosthetic device infections.3S lugdunensis is a CoNS species that was first described in 1988.4 In addition to foreign body–related infections, S lugdunensis has been implicated in bone/joint infections, native valve endocarditis, toxic shock syndrome, and brain abscesses.5-8 Infections due to S lugdunensis are notorious for their aggressive and fulminant courses. With its increased virulence that is atypical of other CoNS, S lugdunensis has understandably been likened more to S aureus.
Prior cases have been reported of S lugdunensis bacteremia in patients using HD. However, the suspected source of bacteremia in these cases has generally been central venous catheters.9-12
Notably, our patient’s AVF was accessed using the buttonhole technique for his home HD sessions, which involves cannulating the same site along the fistula until an epithelialized track has formed from scar tissue. At later HD sessions, duller needles can then be used to cannulate this same track. In contrast, the rope-ladder technique involves cannulating a different site along the fistula until the entire length of the fistula has been used. Patients report higher levels of satisfaction with the buttonhole technique, citing decreased pain, decreased oozing, and the perception of easier cannulation by HD nurses.14 However, the buttonhole technique also appears to confer a higher risk of vascular access-related bloodstream infection when compared with the rope-ladder technique.13,15,16
