Systemic Absorption Resulting from Tobramycin-Loaded Antibiotic Cement Spacers Used in the Treatment of Prosthetic Joint Infection.

Purpose: Antimicrobial cement spacer (ACS) placement has been a cornerstone of two-stage management of prosthetic hip and knee infection. Pharmacokinetic modelling has described peak systemic antibiotic concentrations within the first 24-48 h post-operatively, followed by rapid clearance. A few studies have, however, identified detectable tobramycin levels in patients with a post-operative decline in creatinine clearance. Our study sought to determine how frequently detectable serum tobramycin levels occurred within the first 72 h following ACS placement in all patients regardless of baseline or subsequent changes in renal function, whether these levels correlated with tobramycin spacer dosage, creatinine clearance, or potential nephrotoxicity risk factors, and whether any patients developed acute kidney injury within the 14-day post-operative period. Methods: We prospectively enrolled patients with prosthetic hip or knee infections and subsequent ACS placement from October 2017 to February 2020. Patient comorbidities (chronic kidney disease, diabetes mellitus, chronic liver disease, chronic obstructive pulmonary disease, and atrial fibrillation), Charleston Comorbidity Index score, risk factors for post-operative nephrotoxicity (perioperative hypotension and nephrotoxic agent receipt), total tobramycin dosage, post-operative days 1 and 3 serum tobramycin concentrations, and serum creatinine and creatinine clearance throughout a 14-day post-operative period were recorded. Results: A total of 20 patients were enrolled, comprising 20 spacers with a median total tobramycin dosage of 4.80 g with an interquartile range (IQR) of 4.13-7.20 g. Thirteen patients had a median detectable post-operative day 1 serum tobramycin concentration of 0.80 (IQR 0.50-1.60) mcg/mL. Five of these 13 patients had a median detectable post-operative day 3 serum tobramycin concentration of 0.80 (IQR 0.50-1.10) mcg/mL. A correlation was not found between serum tobramycin drug levels and patient comorbidities, receipt of nephrotoxic medications, or baseline and subsequent post-operative creatinine clearance up to day 14. Conclusion: The majority of patients who underwent tobramycin ACS placement had detectable serum tobramycin levels in the immediate post-operative period, but most reached undetectable levels within 72 h. There were no reliable perioperative predictors of detectable drug levels.

Utility of Direct Specimen Sequencing in Addition to Conventional Testing in Management of Infections in an Urban Referral Health Center.

BACKGROUND: Direct specimen sequencing (DSS) offers the promise of enhanced pathogen detection and disease diagnosis. METHODS: A single healthcare network, retrospective chart review over a 3-year period was completed for all cases in which DSS was submitted, in addition to conventional testing (CT) for workup of an infectious disease. We sought to compare results (concordance and discordance) from these 2 techniques in order to evaluate any additional yield from DSS over CT. Additionally, we calculated mean turnaround time (TAT) and average cost for obtaining DSS on all specimens. RESULTS: A total of 23 patients' specimens were sent for DSS. DSS and CT concordance occurred in 91% (21/23) of cases. DSS testing was able to identify specific pathogens in 17.4% (4/23) of patients, out of which 4% (1/23) were discordant. The respective mean TAT and total cost per specimen for DSS were 6 days and $821.52 (range $573-$1590), respectively. CONCLUSIONS: In our limited cohort of patients, there was significant concordance between the 2 testing modalities primarily due to negative tests. DSS did not provide significant additional yield in the infectious diagnosis in our cohort compared to CT. Short TAT may provide advantage in the detection of fastidious organisms, but high cost remains a limitation. Larger sample size may reveal a clinically meaningful difference.

Scedosporium apiospermum mediastinitis in an orthotopic heart transplant recipient.

Scedosporiosis is an opportunistic mycosis that may cause disseminated disease in transplant recipients. This article reports a case of recurrent Scedosporium apiospermum mediastinitis without pneumonia in an orthotopic heart transplant recipient, with durable control achieved by long-term antifungal therapy and serial debridement. This case highlights the importance of an opportunistic scedosporium infection in immunocompromised hosts, given the challenges in microbiological identification and limited treatment options.

Pott's puffy tumor caused by Actinomyces naeslundii.

Pott's puffy tumor is characterized by forehead swelling from subperiosteal abscess and frontal bone osteomyelitis. It is encountered mainly in children; rarely in adults. When it does occur in the latter population, the most common risk factors include head trauma, sinusitis, or cocaine abuse. Generally, the organisms thought to be involved include streptococci, staphylococci and oral anaerobic flora. We present a case of a 53 year old female who presented with forehead swelling of 3 month duration after a dental procedure, found to be secondary to Actinomyces naeslundii. Actinomyces is a very rare etiology of this disease and has been reported only twice earlier in the literature. We present an uncommon infectious disease along with summary of clinical characteristics of this entity in the adult population.

Retrospective Analysis of Adverse Drug Events Between Nafcillin Versus Cefazolin for Treatment of Methicillin-Susceptible Staphylococcus aureus Infections.

Background: Nafcillin or cefazolin are drugs of choice for methicillin-susceptible Staphylococcus aureus (MSSA) infections. Prior studies indicate a higher incidence of acute kidney injury (AKI) with nafcillin, although AKI classification and time to occurrence is not well described. Objective: To characterize the incidence and time to adverse drug events for nafcillin versus cefazolin in the inpatient setting. Methods: A retrospective cohort study evaluated hospitalized, adult patients receiving intravenous nafcillin or cefazolin for treatment of MSSA infection. Incidence and time to AKI based on RIFLE criteria were measured. Secondary end points included antibiotic discontinuation and incidence of neutropenia, thrombocytopenia, elevated transaminases, and Clostridioides difficile infection (CDI). Results: Of 324 patients who received nafcillin (n = 119) or cefazolin (n = 205), higher rates of AKI were found for nafcillin versus cefazolin (19% vs 2%, respectively; P < 0.0001). Median time to AKI with nafcillin was 6.5 days (range, 3-14 days). The majority of patients were classified as RIFLE "Risk" stratum. Nafcillin treatment discontinuations were more frequent than for cefazolin (17.6% vs 0.9%, respectively; P < 0.0001). Nafcillin was an independent predictor of AKI (odds ratio = 12.4; 95% CI = 4.14-47.60, P < 0.0001). No differences in neutropenia, thrombocytopenia, elevated transaminases, or CDI were observed. Conclusion and Relevance: Nafcillin displayed higher rates of AKI at a median of 1 week of therapy, which provides a framework for clinician monitoring and consideration of antibiotic modification. Most patients developed "Risk" class AKI (RIFLE classification), which may be reversible with prompt intervention.

Potential false-positive urine Legionella enzyme immunoassay test results.

The objective of this study was to identify potential false-positive urine Legionella pneumophila (Legionella) enzyme immunoassay test results. A total of 107 consecutive patients with positive EIA tests were retrospectively analyzed over a 34-month period. Concurrent blood, urine, and sputum cultures, as well as chest radiographic findings, were reviewed in these patients. Twenty patients (19%) had no radiographic evidence of pulmonary disease despite a positive EIA test. In those 20 patients, 14 also had growth of non-Legionella bacteria. Of patients with an infiltrate or opacity on chest imaging, only 27 had Legionella sputum cultures obtained, with Legionella culture growth occurring in 7 (26%). Nine other patients had negative Legionella sputum cultures but the growth of another pathogenic organism in blood, sputum, and/or urine cultures. Pseudomonas aeruginosa was the most common organism isolated, found in 20% of patients in the entire cohort. Twenty-five patients (23%) were characterized as having probable false-positive Legionella urinary antigen EIA testing, and an additional 17 patients (16%) were characterized as having possible false-positive Legionella EIA tests. Our findings suggest that urine Legionella EIA tests may lead to a substantial number of cases being misdiagnosed as Legionaries' disease in patients with non-Legionella bacterial colonization or infection.

Adenoviral nephritis in a renal transplant recipient: Case report and literature review.

Adenovirus (AdV) infections in transplant recipients may cause invasive disease. We present a case of granulomatous interstitial nephritis secondary to AdV infection in a renal transplant recipient that was initially interpreted as acute graft rejection on histopathology. Specific testing based on clinical suspicion, however, aided in making an accurate diagnosis. We present a retrospective review of all cases of AdV infection in renal transplant recipients to date, and analyze outcomes based on different treatment modalities for this disease.

Propionibacterium acnes: Time-to-Positivity in Standard Bacterial Culture From Different Anatomical Sites.

BACKGROUND: Propionibacterium acnes infections are likely under-recognized and underreported. This is partly because of low clinical suspicion, perceived non-pathogenicity, or lack of adequate culture incubation time. We conducted a study to assess the optimal incubation period to recover P. acnes from specimens acquired during the workup of suspected clinical infections. METHODS: A 5-year retrospective chart review was conducted between January 2010 and December 2014 at a single tertiary-care hospital. All patient cases from which P. acnes was recovered were included for analysis. Source of infection, antibiotic use, and culture time-to-positivity (TTP) were recorded. RESULTS: Implanted devices comprised the single most common source of P. acnes infection. In the majority of cases, P. acnes was the only organism identified. The mean incubation TTP for all isolates was 5.73 days. CONCLUSIONS: Standard 5-day culture incubation periods are insufficient to recover P. acnes. As a result, P. acnes is likely a much more common etiology of a variety of clinical infections than previously reported.