Therapeutic Drug Monitoring (TDM) of Suspension (SUS), Extended-Release (ER), and Intravenous (IV) Posaconazole (POS) at a Large Transplant Center

Background

Data on ER and IV POS among organ transplant recipients (OTRs) are limited, and the role of TDM is unclear.

Methods

Retrospective study of patients (pt) receiving any formulation of POS who had serum troughs checked. Therapeutic was defined as ³ 1 mcg/mL.

Results

We analyzed 88 pt and 340 levels (SUS: 88, ER: 197, IV: 55). Eighty-five pt were OTRs (97%), 73 were lung transplant recipients (LT) (83%), 17 had cystic fibrosis (CF) (19%). POS was used for treatment (70%) (probable aspergillosis (38%), possible aspergillosis (10%), mucormycosis (16%), other mycoses (6%)), prophylaxis (19%), and pre-emptive therapy (14%). POS was given for intolerance of or contraindication to other azoles (47%), salvage therapy (10%), resistance (19%), and failure to achieve therapeutic levels with other azoles (6%). Serum concentration/dose ratios were lower with SUS vs. ER/IV (P < 0.0001) but were similar in ER/IV groups (P = 0.51) (Figure). There was no difference in serum levels between pt receiving ER vs. IV POS at 300 mg once daily (median 1.2 vs. 1.3 mcg/mL, therapeutic 70% vs. 73%, P = 0.57 and >0.99, respectively). 3 pt had levels £ 0.2 mcg/mL on 300 mg ER: 2 had CF and had undergone LT (0.2 and 0 mcg/mL) and 1 had short-gut syndrome (0.1 mcg/mL). Sixty-six percent and 67 % of pt receiving ER or IV POS (300 mg once daily) achieved initial therapeutic levels, respectively; of these, 87% and 83% had median therapeutic follow-up levels, respectively. Serial levels were available for 7 pt whose dose was increased from 300 to 400 mg ER once daily for subtherapeutic levels. 4/7 pt achieved therapeutic levels on 400 vs. 0/7 on 300 mg ER once daily (P = 0.069). Metoclopramide use and CF were associated with subtherapeutic vs. therapeutic levels (25% vs. 4% and 37% vs. 13%, respectively, P = < 0.05). When pt with CF were excluded, neither age nor body mass index were associated with POS levels. CF pt had lower levels than non-CF pt on a dose of 300 mg ER once daily (median 0.8 vs. 1.3 mcg/mL, P = 0.018).

Conclusion

Therapeutic levels are more reliably achieved with ER & IV POS compared with SUS POS. Serial TDM is unnecessary for most, but is recommended for pt with CF or those on metoclopramide. Dose increases may effectively increase levels. Novel dosing strategies are needed for CF.

Disclosures

R. K. Shields, Astellas: Received research funding, Research support. Merck: Received research funding, Research support. C. J. Clancy, Merck: Received research funding, Research support. Astellas: Received research funding, Research support. Cidara: Received research funding, Research support. Astellas: Scientific Advisor, Advisory board. Merck: Scientific Advisor, Advisory board. Cidara: Scientific Advisor, Advisory board. Medicines Company: Scientific Advisor, Advisory board.

Ceftazidime-Avibactam Is Superior to Other Treatment Regimens against Carbapenem-Resistant Klebsiella pneumoniae Bacteremia

There are no data comparing outcomes of patients treated with ceftazidime-avibactam versus comparators for carbapenem-resistant Enterobacteriaceae infections. At our center, ceftazidime-avibactam treatment of carbapenem-resistant Klebsiella pneumoniae bacteremia was associated with higher rates of clinical success (P = 0.006) and survival (P = 0.01) than other regimens. Across treatment groups, there were no differences in underlying diseases, severity of illness, source of bacteremia, or strain characteristics (97% produced K. pneumoniae carbapenemase). Aminoglycoside- and colistin-containing regimens were associated with increased rates of nephrotoxicity (P = 0.002).

Ceftolozane-Tazobactam for the Treatment of Multidrug-Resistant Pseudomonas aeruginosa Infections: Clinical Effectiveness and Evolution of Resistance

Background

Data on the use of ceftolozane-tazobactam and emergence of ceftolozane-tazobactam resistance during multidrug resistant (MDR)-Pseudomonas aeruginosa infections are limited.

Methods

We performed a retrospective study of 21 patients treated with ceftolozane-tazobactam for MDR-P. aeruginosa infections. Whole genome sequencing and quantitative real-time polymerase chain reaction were performed on longitudinal isolates.

Results

Median age was 58 years; 9 patients (43%) were transplant recipients. Median simplified acute physiology score-II (SAPS-II) was 26. Eighteen (86%) patients were treated for respiratory tract infections; others were treated for bloodstream, complicated intraabdominal infections, or complicated urinary tract infections. Ceftolozane-tazobactam was discontinued in 1 patient (rash). Thirty-day all-cause and attributable mortality rates were 10% (2/21) and 5% (1/21), respectively; corresponding 90-day mortality rates were 48% (10/21) and 19% (4/21). The ceftolozane-tazobactam failure rate was 29% (6/21). SAPS-II score was the sole predictor of failure. Ceftolozane-tazobactam resistance emerged in 3 (14%) patients. Resistance was associated with de novo mutations, rather than acquisition of resistant nosocomial isolates. ampC overexpression and mutations were identified as potential resistance determinants.

Conclusions

In this small study, ceftolozane-tazobactam was successful in treating 71% of patients with MDR-P. aeruginosa infections, most of whom had pneumonia. The emergence of ceftolozane-tazobactam resistance in 3 patients is worrisome and may be mediated in part by AmpC-related mechanisms. More research on treatment responses and resistance during various types of MDR-P. aeruginosa infections is needed to define ceftolozane-tazobactam's place in the armamentarium.

Emergence of Ceftazidime-Avibactam Resistance and Restoration of Carbapenem Susceptibility in Klebsiella pneumoniae Carbapenemase-Producing K pneumoniae: A Case Report and Review of Literature

We used meropenem to successfully treat a patient with bacteremia due to ceftazidime-avibactam-resistant, meropenem- susceptible Klebsiella pneumoniae that carried mutant bla_KPC-3. Meropenem was bactericidal against ceftazidime-avibactam- resistant K pneumoniae isolates in vitro. Nevertheless, the role of carbapenems in treating such infections remains uncertain, because meropenem resistance is selected readily during passage experiments.

Risk Factors Associated With Outpatient Parenteral Antibiotic Therapy Program Failure Among Intravenous Drug Users

Sixty-one percent of intravenous drug users (IVDUs) who received outpatient parenteral antibiotic therapy (OPAT) failed treatment. Hospital readmission and adverse drug reactions occurred in 25%. By multivariate analysis, time since last IVDU was associated with failure (P = .04). Intravenous drug users requiring OPAT are at high risk for failure; additional studies are needed to explore alternatives.

Defining the incidence and risk factors of colistin-induced acute kidney injury by KDIGO criteria

Background

Acute kidney injury (AKI) remains a treatment-limiting toxicity of colistin. Recently developed clinical practice guidelines from the Kidney Disease: Improving Global Outcomes (KDIGO) group have harmonized definitions of AKI, but have not been widely applied to patients receiving colistin.

Methods

We retrospectively defined AKI by KDIGO definitions among adult patients receiving intravenous colistin for ≥ 3 days. Risk factors for AKI within 48 hours and 7 days of initiating colistin were determined by multivariable logistic regression.

Results

Among 249 patients treated with colistin, rates of AKI were 12% and 29% at 48 hours and 7 days, respectively. At 48 hours, patients in the intensive care unit were at increased risk for AKI. Within 7 days, colistin daily doses >5mg/kg, chronic liver disease, and concomitant vancomycin were independent predictors. Seven percent of patients required renal replacement therapy at a median of 5 days (range: 3–7) following colistin initiation.

Conclusion

Safe use of colistin is promoted by early detection of AKI with KDIGO criteria, avoiding nephrotoxins, and limiting duration of therapy.

The hidden societal cost of antibiotic resistance per antibiotic prescribed in the United States: an exploratory analysis

Background

Ambulatory antibiotic prescribing contributes to the development of antibiotic resistance and increases societal costs. Here, we estimate the hidden societal cost of antibiotic resistance per antibiotic prescribed in the United States.

Methods

In an exploratory analysis, we used published data to develop point and range estimates for the hidden societal cost of antibiotic resistance (SCAR) attributable to each ambulatory antibiotic prescription in the United States. We developed four estimation methods that focused on the antibiotic-resistance attributable costs of hospitalization, second-line inpatient antibiotic use, second-line outpatient antibiotic use, and antibiotic stewardship, then summed the estimates across all methods.

Results

The total SCAR attributable to each ambulatory antibiotic prescription was estimated to be $13 (range: $3–$95). The greatest contributor to the total SCAR was the cost of hospitalization ($9; 69 % of the total SCAR). The costs of second-line inpatient antibiotic use ($1; 8 % of the total SCAR), second-line outpatient antibiotic use ($2; 15 % of the total SCAR) and antibiotic stewardship ($1; 8 %). This apperars to be an error.; of the total SCAR) were modest contributors to the total SCAR. Assuming an average antibiotic cost of $20, the total SCAR attributable to each ambulatory antibiotic prescription would increase antibiotic costs by 65 % (range: 15–475 %) if incorporated into antibiotic costs paid by patients or payers.

Conclusions

Each ambulatory antibiotic prescription is associated with a hidden SCAR that substantially increases the cost of an antibiotic prescription in the United States. This finding raises concerns regarding the magnitude of misalignment between individual and societal antibiotic costs.

Clinical Outcomes, Drug Toxicity, and Emergence of Ceftazidime-Avibactam Resistance Among Patients Treated for Carbapenem-Resistant Enterobacteriaceae Infections

Thirty-seven carbapenem-resistant Enterobacteriaceae (CRE)-infected patients were treated with ceftazidime-avibactam. Clinical success and survival rates at 30 days were 59% (22/37) and 76% (28/37), respectively. In 23% (5/22) of clinical successes, CRE infections recurred within 90 days. Microbiologic failure rate was 27% (10/37). Ceftazidime-avibactam resistance was detected in 30% (3/10) of microbiologic failures.

Predicting the risk of nephrotoxicity in patients receiving colistimethate sodium: a multicentre, retrospective, cohort study

OBJECTIVES

With increasing rates of infections caused by MDR Gram-negative organisms, clinicians resort to older agents such as colistimethate sodium (CMS) despite a significant risk of nephrotoxicity. Several risk factors for CMS-associated nephrotoxicity have been reported, but they have yet to be validated. We compared the performance of published mathematical models in predicting the risk of CMS-associated nephrotoxicity.

METHODS

In a multicentre, retrospective, cohort study, adult patients (≥18 years of age) were evaluated from five large academic medical centres in the USA. Patients with normal renal function (baseline serum creatinine ≤1.5 mg/dL) who received intravenous CMS for ≥72 h were followed for up to 30 days. The development of nephrotoxicity was as defined by the RIFLE criteria. Each published model was conditioned using patient-specific variables to predict the risk of nephrotoxicity. The predictive performance of the models was evaluated using the observed-to-expected (O/E) ratio. The most significant cut-off threshold for stratifying patients into high and low risk of nephrotoxicity was identified using classification and regression tree analysis.

RESULTS

A total of 106 patients were examined (mean age 53.3 ± 14.9 years, 66% male); the overall observed nephrotoxicity rate was 52.8%. We identified a simple model demonstrating reasonable overall nephrotoxicity risk assessment [O/E ratio of 1.07 (95% CI = 0.81-1.39)] and high sensitivity (92.9%) in predicting nephrotoxicity development in patients on CMS therapy.

CONCLUSIONS

We identified a model that could be incorporated into patient management strategies to reduce the risk of nephrotoxicity in patients requiring CMS therapy.

Intra-Abdominal Candidiasis: The Importance of Early Source Control and Antifungal Treatment

Intra-abdominal candidiasis (IAC) is poorly understood compared to candidemia. We described the clinical characteristics, microbiology, treatment and outcomes of IAC, and identified risk factors for mortality. We performed a retrospective study of adults diagnosed with IAC at our center in 2012–2013. Risk factors for mortality were evaluated using multivariable logistic regression. We identified 163 patients with IAC, compared to 161 with candidemia. Types of IAC were intra-abdominal abscesses (55%), secondary peritonitis (33%), primary peritonitis (5%), infected pancreatic necrosis (5%), and cholecystitis/cholangitis (3%). Eighty-three percent and 66% of secondary peritonitis and abscesses, respectively, stemmed from gastrointestinal (GI) tract sources. C. albicans (56%) and C. glabrata (24%) were the most common species. Bacterial co-infections and candidemia occurred in 67% and 6% of patients, respectively. Seventy-two percent of patients underwent an early source control intervention (within 5 days) and 72% received early antifungal treatment. 100-day mortality was 28%, and highest with primary (88%) or secondary (40%) peritonitis. Younger age, abscesses and early source control were independent predictors of survival. Younger age, abscesses and early antifungal treatment were independently associated with survival for IAC stemming from GI tract sources. Infectious diseases (ID) consultations were obtained in only 48% of patients. Consulted patients were significantly more likely to receive antifungal treatment. IAC is a common disease associated with heterogeneous manifestations, which result in poor outcomes. All patients should undergo source control interventions and receive antifungal treatment promptly. It is important for the ID community to become more engaged in treating IAC.

Bone architecture adaptations after spinal cord injury: impact of long-term vibration of a constrained lower limb

SUMMARY

This study examined the effect of a controlled dose of vibration upon bone density and architecture in people with spinal cord injury (who eventually develop severe osteoporosis). Very sensitive computed tomography (CT) imaging revealed no effect of vibration after 12 months, but other doses of vibration may still be useful to test.

INTRODUCTION

The purposes of this report were to determine the effect of a controlled dose of vibratory mechanical input upon individual trabecular bone regions in people with chronic spinal cord injury (SCI) and to examine the longitudinal bone architecture changes in both the acute and chronic state of SCI.

METHODS

Participants with SCI received unilateral vibration of the constrained lower limb segment while sitting in a wheelchair (0.6g, 30 Hz, 20 min, three times weekly). The opposite limb served as a control. Bone mineral density (BMD) and trabecular micro-architecture were measured with high-resolution multi-detector CT. For comparison, one participant was studied from the acute (0.14 year) to the chronic state (2.7 years).

RESULTS

Twelve months of vibration training did not yield adaptations of BMD or trabecular micro-architecture for the distal tibia or the distal femur. BMD and trabecular network length continued to decline at several distal femur sub-regions, contrary to previous reports suggesting a "steady state" of bone in chronic SCI. In the participant followed from acute to chronic SCI, BMD and architecture decline varied systematically across different anatomical segments of the tibia and femur.

CONCLUSIONS

This study supports that vibration training, using this study's dose parameters, is not an effective anti-osteoporosis intervention for people with chronic SCI. Using a high-spatial-resolution CT methodology and segmental analysis, we illustrate novel longitudinal changes in bone that occur after spinal cord injury.

Effects of Klebsiella pneumoniae carbapenemase subtypes, extended-spectrum β-lactamases, and porin mutations on the in vitro activity of ceftazidime-avibactam against carbapenem-resistant K. pneumoniae

Avibactam is a novel β-lactamase inhibitor with affinity for Klebsiella pneumoniae carbapenemases (KPCs). In combination with ceftazidime, the agent demonstrates activity against KPC-producing K. pneumoniae (KPC-Kp). KPC-Kp strains are genetically diverse and harbor multiple resistance determinants, including defects in outer membrane proteins and extended-spectrum β-lactamases (ESBLs). Mutations in porin gene ompK36 confer high-level carbapenem resistance to KPC-Kp strains. Whether specific mechanisms of antimicrobial resistance also influence the activity of ceftazidime-avibactam is unknown. We defined the effects of ceftazidime-avibactam against 72 KPC-Kp strains with diverse mechanisms of resistance, including various combinations of KPC subtypes and ESBL and ompK36 mutations. Ceftazidime MICs ranged from 64 to 4,096 μg/ml and were lowered by a median of 512-fold with the addition of avibactam. All strains exhibited ceftazidime-avibactam MICs at or below the CLSI breakpoint for ceftazidime (≤4 μg/ml; range, 0.25 to 4). However, the MICs were within two 2-fold dilutions of the CLSI breakpoint against 24% of the strains, and those strains would be classified as nonsusceptible to ceftazidime by EUCAST criteria (MIC > 1 μg/ml). Median ceftazidime-avibactam MICs were higher against KPC-3 than KPC-2 variants (P = 0.02). Among KPC-2-Kp strains, the presence of both ESBL and porin mutations was associated with higher drug MICs compared to those seen with either factor alone (P = 0.003 and P = 0.02, respectively). In conclusion, ceftazidime-avibactam displays activity against genetically diverse KPC-Kp strains. Strains with higher-level drug MICs provide a reason for caution. Judicious use of ceftazidime-avibactam alone or in combination with other agents will be important to prevent the emergence of resistance.

Spontaneous fungal peritonitis: a devastating complication of cirrhosis

Spontaneous bacterial peritonitis is a well-known complication of cirrhosis; however, spontaneous fungal peritonitis (SFP) is less well-recognised and described. Our objective was to determine the clinical characteristics, treatment outcomes and factors associated with death among patients with SFP. We performed a retrospective cohort study using the primary outcome of all-cause mortality at 28 days. Twenty-five patients were included; Candida species were the causative pathogen in all cases. At the onset of SFP, patients were critically ill, median APACHE II and MELD scores were 22 and 30.3, respectively. The 28-day mortality rate was 56%; six patients died prior to culture positivity. Among the remaining patients, there were no differences in rates of death by treatment regimen (P = 0.55). APACHE II score at the onset of SFP was an independent predictor of death (OR = 1.46, 95% CI = 1.02-2.08, P = 0.04). In conclusion, SFP develops among critically ill patients with cirrhosis and is associated with high rates of death. Directed antifungal therapy did not improve patient outcomes. Future studies assessing the benefit of early or pre-emptive antifungal therapy are warranted.

Colistin-resistant Acinetobacter baumannii: beyond carbapenem resistance

BACKGROUND

With an increase in the use of colistin methansulfonate (CMS) to treat carbapenem-resistant Acinetobacter baumannii infections, colistin resistance is emerging.

METHODS

Patients with infection or colonization due to colistin-resistant A. baumannii were identified at a hospital system in Pennsylvania. Clinical data were collected from electronic medical records. Susceptibility testing, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST) were performed. To investigate the mechanism of colistin resistance, lipid A was subjected to matrix-assisted laser desorption/ionization mass spectrometry.

RESULTS

Twenty patients with colistin-resistant A. baumannii were identified. Ventilator-associated pneumonia was the most common type of infection. Nineteen patients had received intravenous and/or inhaled CMS for treatment of carbapenem-resistant, colistin-susceptible A. baumannii infection prior to identification of colistin-resistant isolates. The 30-day all-cause mortality rate was 30%. The treatment regimen for colistin-resistant A. baumannii infection associated with the lowest mortality rate was a combination of CMS, a carbapenem, and ampicillin-sulbactam. The colistin-susceptible and -resistant isolates from the same patients were highly related by PFGE, but isolates from different patients were not, suggesting evolution of resistance during CMS therapy. By MLST, all isolates belonged to the international clone II, the lineage that is epidemic worldwide. Phosphoethanolamine modification of lipid A was present in all colistin-resistant A. baumannii isolates.

CONCLUSIONS

Colistin-resistant A. baumannii occurred almost exclusively among patients who had received CMS for treatment of carbapenem-resistant, colistin-susceptible A. baumannii infection. Lipid A modification by the addition of phosphoethanolamine accounted for colistin resistance. Susceptibility testing for colistin should be considered for A. baumannii identified from CMS-experienced patients.