Amy Hanson

Treatment Outcomes with Cefazolin versus Oxacillin for Deep-Seated Methicillin-Susceptible Staphylococcus aureus Bloodstream Infections

ABSTRACT Clinical preference for a semisynthetic penicillin (oxacillin or nafcillin) over cefazolin for deep-seated methicillin-susceptible Staphylococcus aureus (MSSA) bloodstream infections (BSI) perseveres despite limited data to support this approach. A retrospective cohort study of patients treated for MSSA BSI with either oxacillin or cefazolin was performed across two medical centers in Chicago, IL. The outcome measures included documented in-hospital treatment failure, all-cause in-hospital mortality, duration of MSSA BSI, and incidence of documented adverse events. Of 161 patients with MSSA BSI, 103 (64%) received cefazolin, and 58 (36%) received oxacillin. The identified sources of BSI were central line (37.9%), osteoarticular (18%), and skin and soft tissue (17.4%). Patients with endocarditis (29/52 [44.2%]) and other deep-seated infections (23/52 [55.8%]) were classified under the subset of deep-seated infections (52/161 [32.3%]). Multivariate models found deep-seated infection (adjusted odds ratio [aOR], 4.52; 95% confidence interval [CI], 1.23 to 16.6; P = 0.023), metastatic disease (aOR, 4.21; 95% CI, 1.13 to 15.7; P = 0.033), and intensive care unit (ICU) onset of infection (aOR, 4.80; 95% CI, 1.26 to 18.4; P = 0.022) to be independent risk factors for in-hospital treatment failure. Treatment group was not an independent predictor of failure (aOR, 3.76; 95% CI, 0.98 to 14.4; P = 0.053). The rates of treatment failure were similar among cefazolin-treated (5/32 [15.6%]) and oxacillin-treated (4/20 [20.0%]) patients (P = 0.72) in the subset of deep-seated infections. Mortality was observed in 1 (1%) and 3 (5.2%) cases of cefazolin- and oxacillin-treated patients, respectively (P = 0.13). Cefazolin was not associated with higher rates of treatment failure and appears to be an effective alternative to oxacillin for treatment of deep-seated MSSA BSI.

Diffuse Desquamating Rash Following Exposure to Vancomycin-Impregnated Bone Cement

Objective: To describe a case of systemic desquamating dermatitis following implantation of vancomycin antibiotic–laden cement (ABLC) in a patient with prior history of Stevens-Johnson (SJS) reaction to vancomycin. Case Summary: A 59-year-old man with a history of SJS reaction to systemic vancomycin and recurrent methicillin-susceptible Staphylococcus aureus prosthetic knee infection developed a painful, blistering rash after implantation of bone cement that had been mixed with 2 g of vancomycin. He was started empirically on steroids by his primary care provider and had desquamation about 1 week later. Discussion: Systemic absorption of antibiotics from ABLC has been well documented in the literature. Reports of systemic toxicity are rare, and none have described systemic allergic reactions to vancomycin. This patient’s prior episode of SJS was diagnosed at another academic medical center 6 years ago, and records are unavailable. Following low-level reexposure to vancomycin, he developed a diffuse painful desquamating rash. Application of the Naranjo nomogram yielded a score of 8 (probable adverse reaction). Although he did not experience fever, sore throat, or mucous membrane involvement to fulfill classic features of SJS, we believe that his severe rash represented a less-severe form of a systemic hypersensitivity reaction to vancomycin. Conclusion: Antibiotics contained in ABLC are systemically absorbed, though at low levels, and have been associated with systemic toxicities. Antibiotics to which a patient has had a potentially life-threatening reaction should not be used in ABLC. Particular attention should be paid to an individual’s antibiotic allergy history prior to implantation of any ABLC.

A Case of Linezolid Induced Toxicity

Adverse effects of linezolid are typically limited to diarrhea, nausea, and headache when shorter durations are used; however, as extended durations of linezolid therapy are increasingly more common, additional monitoring parameters should be considered in these patients. We describe a unique case of hypoglycemia, lactic acidosis, and pancreatitis related to an extended duration of linezolid therapy. A 52-year-old woman presented with altered mental status, abdominal pain, and hypotension following six weeks of linezolid and ertapenem therapy. Laboratory data revealed an initial blood glucose of 40 mg/dL and metabolic acidosis secondary to lactic acidosis. Finally, her abdominal pain on admission was likely related to an enlarged pancreas noted on computed tomography of her abdomen. Due to suspected linezolid toxicity, the patient received two intermittent hemodialysis sessions to remove linezolid and correct the metabolic acidosis. Given limited data on long-term monitoring of patients receiving extended durations of linezolid therapy, we suggest periodic monitoring of lactate, arterial blood gas, and blood glucose. If patients present with this triad of symptoms secondary to linezolid therapy, adverse effects should be treated with dextrose and intravenous thiamine while reserving hemodialysis for those with metabolic acidosis refractory to thiamine.

Improving time to optimal Staphylococcus aureus treatment using a penicillin-binding protein 2a assay

The penicillin-binding protein 2a (PBP2a) assay is a quick, accurate and inexpensive test for determining methicillin susceptibility in Staphylococcus aureus. A pre-post-study design was conducted using a PBP2a assay with and without the impact of an antimicrobial stewardship intervention to improve time to optimal therapy for methicillin-susceptible and methicillin-resistant S. aureus isolates. Our results demonstrate significantly improved time to optimal therapy and support the use of a PBP2a assay as part of an programme for all healthcare facilities, especially those with limited resources.

Erratum for Rao et al., Treatment Outcomes with Cefazolin versus Oxacillin for Deep-Seated Methicillin-Susceptible Staphylococcus aureus Bloodstream Infections

Volume 59, no. 9, p. [5232–5238][1], 2015. Page 5235, left column, lines 18–20: “had a shorter median (IQR) time to achieving source control (1.5 [0 to 3] days versus 2 [1 to 4] days” should read “had a longer median (IQR) time to achieving source control (2 [1 to 4] days versus 1.5 [0 to