Donna R. Burgess

Increasing Incidence of Multidrug Resistance Among Cystic Fibrosis Respiratory Bacterial Isolates

Pseudomonas aeruginosa and Staphylococcus aureus are common pathogens in cystic fibrosis (CF) patients with increasing multidrug resistance (MDR). This study characterized antimicrobial susceptibility trends among organisms isolated from the respiratory tract of CF patients. Microbiological culture and sensitivity results for all CF patients were collected from January 2010 through December 2014. Minimum inhibitory concentrations were obtained using Phoenix® and Etest® methods. Clinical and Laboratory Standards Institute guidelines were used to remove duplicate isolates and develop antimicrobial susceptibility reports. MDR was defined as resistance to one agent in three or more antibiotic classes or oxacillin resistance in S. aureus. Overall, 542 bacterial isolates from 376 cultures were analyzed for trends. P. aeruginosa (41%), S. aureus (40%), and Stenotrophomonas maltophilia (8%) were the most commonly isolated organisms. Multidrug-resistant organism isolation increased from 39% to 49% (r = 0.76, p = 0.13), while representing 47.6% of all isolates. Multidrug-resistant P. aeruginosa incidence increased each year from 26% to 43% (r = 0.89, p = 0.046), while P. aeruginosa isolation decreased from 47% to 38% over the study period (r = -0.93, p = 0.02). MRSA accounted for 62.6% of all S. aureus isolated, while overall multidrug-resistant S. aureus incidence was 73.1% in all cultures. MDR among common pathogens in CF continues to increase. Empiric therapy for CF exacerbations should be targeted to previous antimicrobial susceptibility, and P. aeruginosa and S. aureus should be empirically covered.

ACUTE KIDNEY INJURY IN PATIENTS TREATED WITH VANCOMYCIN AND PIPERACILLIN-TAZOBACTAM: A RETROSPECTIVE COHORT ANALYSIS

BACKGROUND: Empiric antimicrobial therapy often consists of the combination of gram‐positive coverage with vancomycin (VAN) and gram‐negative coverage, specifically an antipseudomonal beta‐lactam such as piperacillin‐tazobactam (PTZ). Nephrotoxicity is commonly associated with VAN therapy; however, recent reports show higher nephrotoxicity rates among patients treated with the combination of VAN and PTZ. OBJECTIVE: This study evaluated the effect of the VAN/PTZ combination on acute kidney injury (AKI) compared to VAN and PTZ monotherapies. DESIGN, SETTING, AND PATIENTS: This is a retrospective cohort analysis of adult patients without renal disease receiving VAN, PTZ, or the combination from September 1, 2010 through August 31, 2014 at an academic medical center. MEASUREMENTS: The primary outcome was AKI incidence as defined by the Risk, Injury, Failure, Loss, End‐stage (RIFLE) criteria. METHODS: Continuous and categorical variables were assessed with appropriate tests. Univariate and multivariate logistic regressions were performed to assess for associations between variables and AKI incidence. Subanalyses based on severity of illness were performed. RESULTS: Overall, 11,650 patients were analyzed, with 1647 (14.1%) developing AKI. AKI was significantly more frequent in the VAN/PTZ group (21%) compared to either monotherapy group (VAN 8.3%, PTZ 7.8%, P < 0.001 for both). Combination therapy was independently associated with higher AKI odds compared to monotherapy with either agent (adjusted odds ratio [aOR], 2.03; 95% confidence interval [CI], 1.74‐2.39; aOR, 2.31; 95% CI, 1.97‐2.71, for VAN and PTZ, respectively). Receipt of concomitant nephrotoxic drugs was independently associated with increased AKI rates, as were increased duration of therapy, hospital length of stay, increasing severity of illness, and increasing baseline renal function. CONCLUSIONS: In this study of more than 10,000 patients, VAN combined with PTZ was associated with twice the odds of AKI development compared to either agent as monotherapy. This demonstrates the need for judicious use of combination empiric therapy.

Nephrotoxicity during Vancomycin Therapy in Combination with Piperacillin-Tazobactam or Cefepime

ABSTRACT Recent reports have demonstrated that vancomycin (VAN) may lead to an increase in the incidence of acute kidney injury (AKI) when it is combined with antipseudomonal beta-lactams. This study compared the incidence of AKI associated with VAN plus piperacillin-tazobactam (TZP) or cefepime (FEP). This was a retrospective, matched cohort study that was conducted at an academic medical center between September 2010 and September 2014 and that included adult patients without severe chronic or structural kidney disease, dialysis, pregnancy, cystic fibrosis, or a hospital transfer receiving TZP-VAN or FEP-VAN for at least 48 h. The primary outcome was the difference in the AKI incidence between the TZP-VAN and FEP-VAN groups, evaluated using the risk, injury, failure, loss of kidney function, and end-stage kidney disease (RIFLE) criteria. Patients in the two groups were matched on the basis of age, sex, severity of illness, baseline creatinine clearance, hypotension, number of nephrotoxicity risk factors, and intravenous contrast exposure. In total, 4,193 patients met all inclusion criteria (3,605 received TZP-VAN and 588 received FEP-VAN). The unadjusted AKI incidence was 21.4% in patients receiving TZP-VAN, whereas it was 12.6% in patients receiving FEP-VAN (P < 0.001). After the patients were matched, 1,633 patients receiving TZP-VAN and 578 patients receiving FEP-VAN were evaluated. The AKI incidence remained higher in patients receiving TZP-VAN than in those receiving FEP-VAN (21.4% versus 12.5%, P < 0.0001). This trend remained true for all classifications of the RIFLE criteria. After controlling for remaining confounders, TZP-VAN therapy was associated with 2.18 times the odds of AKI than FEP-VAN therapy (95% confidence interval, 1.64 to 2.94 times) in logistic regression. AKI was significantly more common in patients receiving vancomycin in combination with piperacillin-tazobactam than in those receiving vancomycin in combination with cefepime. This finding reinforces the need for the judicious use of combination empirical antimicrobial therapy.

Pharmacokinetic and Pharmacodynamic Analyses of Ceftaroline in Adults with Cystic Fibrosis.

To evaluate the pharmacokinetics and pharmacodynamics of ceftaroline in adults with cystic fibrosis (CF).

Influence of β -Lactam Infusion Strategy on Acute Kidney Injury

ABSTRACT Limited literature is available assessing nephrotoxicity with prolonged β-lactam infusions. This study compared the incidence of acute kidney injury (AKI) associated with a prolonged β-lactam infusion or an intermittent infusion. This was a retrospective, matched-cohort study at an academic medical center from July 2006 to September 2015. Adult patients who received piperacillin-tazobactam (TZP), cefepime (FEP), or meropenem (MEM) for at least 48 h were evaluated. Patients were excluded for preexisting renal dysfunction or pregnancy. The primary outcome was difference in incidence of AKI evaluated using the RIFLE (risk, injury, failure, loss, and end-stage) criteria. Patients in the intermittent group were matched 3:1 to patients in the prolonged-infusion group based on the following: β-lactam agent, age, gender, Charlson comorbidity index, baseline creatinine clearance, hypotension, receipt of vancomycin, and treatment in an intensive care unit. A total of 2,390 patients were included in the matched analysis, with 1,700 receiving intermittent infusions and 690 receiving prolonged infusion. The incidence of AKI was similar in the prolonged-infusion group to that in the intermittent-infusion group (21.6% versus 18.6%; P = 0.1). After multivariate regression, prolonged infusion was not associated with increased odds of AKI (odds ratio [OR], 1.07; 95% confidence interval [95% CI], 0.83 to 1.39). Independent predictors of AKI included TZP therapy, concomitant nephrotoxins, hypotension, and heart failure. Although AKIs were numerically more common in patients receiving prolonged β-lactam infusions than those receiving intermittent infusions, prolonged infusion was not an independent risk factor for AKI.

Nephrotoxicity in patients with or without cystic fibrosis treated with Polymyxin B compared to colistin

ABSTRACT Nephrotoxicity is the primary adverse effect of the polymyxins. The relative rates of toxicity of polymyxin B and colistin have not been fully elucidated, especially in patients with cystic fibrosis (CF). A retrospective cohort study of adults treated with polymyxin B or colistin for at least 48 h was conducted. The primary endpoint was the incidence of kidney injury assessed by RIFLE (i.e., risk, injury, failure, loss, end-stage renal disease) criteria. Risk factors for kidney injury were evaluated using multivariate Cox regression. A total of 414 patients were evaluated, 220 of whom had CF. In patients without CF, there was no difference in kidney injury with polymyxin B and colistin (42.9% versus 50.3%, P = 0.46). Loop diuretic exposure was a risk factor for kidney injury (adjusted hazard ratio [aHR], 1.82; 95% confidence interval [CI], 1.16 to 2.83) in this population. In patients with CF, polymyxin B and colistin were associated with similar rates of kidney injury (34.5% versus 29.8%, P = 0.77). Diabetes (aHR, 2.68; 95% CI, 1.01 to 7.11), loop diuretics (aHR, 3.02; 95% CI, 1.36 to 6.73), and progressive care unit admission (aHR, 8.21; 95% CI, 2.55 to 26.46) were risk factors for kidney injury, while higher baseline serum creatinine levels (per 1 mg/dl) were protective (aHR, 0.08; 95% CI, 0.01 to 0.48). Total unadjusted kidney injury in polymyxin-treated patients was less frequent in those who had CF (30.5% versus 48.5%, P < 0.001). Polymyxin B and colistin are associated with a high incidence of kidney injury; cystic fibrosis may be protective against polymyxin nephrotoxicity, but further investigation is needed to confirm this conjecture.

Utilizing Monte Carlo Simulations to Optimize Institutional Empiric Antipseudomonal Therapy

Pseudomonas aeruginosa is a common pathogen implicated in nosocomial infections with increasing resistance to a limited arsenal of antibiotics. Monte Carlo simulation provides antimicrobial stewardship teams with an additional tool to guide empiric therapy. We modeled empiric therapies with antipseudomonal β-lactam antibiotic regimens to determine which were most likely to achieve probability of target attainment (PTA) of ≥90%. Microbiological data for P. aeruginosa was reviewed for 2012. Antibiotics modeled for intermittent and prolonged infusion were aztreonam, cefepime, meropenem, and piperacillin/tazobactam. Using minimum inhibitory concentrations (MICs) from institution-specific isolates, and pharmacokinetic and pharmacodynamic parameters from previously published studies, a 10,000-subject Monte Carlo simulation was performed for each regimen to determine PTA. MICs from 272 isolates were included in this analysis. No intermittent infusion regimens achieved PTA ≥90%. Prolonged infusions of cefepime 2000 mg Q8 h, meropenem 1000 mg Q8 h, and meropenem 2000 mg Q8 h demonstrated PTA of 93%, 92%, and 100%, respectively. Prolonged infusions of piperacillin/tazobactam 4.5 g Q6 h and aztreonam 2 g Q8 h failed to achieved PTA ≥90% but demonstrated PTA of 81% and 73%, respectively. Standard doses of β-lactam antibiotics as intermittent infusion did not achieve 90% PTA against P. aeruginosa isolated at our institution; however, some prolonged infusions were able to achieve these targets.

Respiratory Muscle Paralysis Associated With Colistin, Polymyxin B, and Muscle Relaxants Drugs A Case Report

Polymyxins B and E (colistin) exert a bactericidal effect on the gram-negative bacterial cell wall, causing permeability changes in the cytoplasmic membrane, leading to cell death. Their use was substantially decreased in clinical practice from the 1970s to 2000s due to their significant nephrotoxicity and neurotoxicity compared to the newly introduced antibiotics. The increasing prevalence of multidrug-resistant gram-negative bacteria infections in this century has led to an upsurge in the use of these “older” drugs. Respiratory paralysis caused by neuromuscular blockage associated with the use of polymyxin B and E was reported mostly in literature published in the 1960s to 1970s with a few reports after 2000. In addition, such a reaction might be enhanced by the presence of other classes of drugs. We report a case of polymyxin B and E–induced apnea in a patient receiving “muscle relaxants.”

Optimizing beta-lactam pharmacodynamics against Pseudomonas aeruginosa in adult cystic fibrosis patients

BACKGROUND Patients with cystic fibrosis (CF) exhibit increased clearance of beta-lactams. The purpose of this study was to predict the probability of beta-lactam target attainment (PTA) against Pseudomonas aeruginosa in adult CF patients based on local microbiological data. METHODS CF-specific pharmacokinetic parameters were obtained from published data for aztreonam, cefepime, ceftazidime, meropenem and piperacillin-tazobactam. Pharmacodynamic modeling was used to determine the PTA for bolus, prolonged infusion, and continuous infusion regimens. RESULTS Prolonged infusion of meropenem 2g every 8h performed the best among all regimens tested, with a PTA of 83%. The PTA was increased with both prolonged and continuous infusion; however, no regimen reached the target PTA of >90% against P. aeruginosa in CF patients at our institution. CONCLUSIONS Prolonged and continuous infusion provided higher PTA than bolus for all regimens. Further investigation of novel regimens in CF patients is needed.

Impact of an Antimicrobial Stewardship Initiative Focused on Staphylococcus aureus Bacteremia

Abstract Background Data exists to support a mortality reduction from S. aureus bacteremia with adherence to evidence-based recommendations. Therefore, our Antimicrobial Stewardship Team instituted a guideline focused on S. aureus bacteremia management. This study outlines improvements achieved through the implementation at an academic medical center. Methods A quasi-experimental approach evaluated pre-implementation (2014–15) and post-implementation (2015–17) periods. The Antimicrobial Stewardship Team provided a detailed standardized note and management guidelines. Adult patients with S. aureus bacteremia identified by a rapid diagnostic system were evaluated. Patients were excluded if discharged within 48 hours of a first positive blood culture or transitioned to comfort care. The primary outcome was all-cause 30-day mortality and secondary outcomes were total guideline adherence (TGA) and appropriateness of therapy. Results Overall, 263 patients (105 pre-implementation; 158 post-implementation) were included. No significant differences were observed in baseline characteristics (e.g., age, gender, ethnicity); however, the mean Pitt Bacteremia score was significantly lower in the post-implementation group (2 vs. 1; P = 0.01). Although no difference was observed in all-cause 30-day mortality (13% vs. 15%; P = 0.8), improved TGA (29% vs. 44%; P = 0.01) and appropriateness of therapy (68% vs. 74%; P = 0.26) were noted while duration of bacteremia decreased (3.6 days vs. 2.8 days; P = 0.02) in the post-implementation period. In uncomplicated bacteremia, TGA (15% vs. 38%; P = 0.02) and adequate duration of therapy (54% vs. 77%; P = 0.02) significantly improved. In complicated bacteremia, TGA (36% vs. 48%; P = 0.14) and targeted agents utilized (92% vs. 100%; P < 0.01) increased post-implementation. Additionally, achieving TGA significantly reduced all-cause 30-day mortality in complicated (33% vs. 1.5%; P < 0.01) and uncomplicated (26% vs. 5.6%; P = 0.01) bacteremia for the entire sample. Conclusion The Antimicrobial Stewardship initiative significantly improved adherence to evidence-based guidelines for S. aureus bacteremia management. Though no impact on all-cause mortality was observed, a significant effect was noted when TGA was achieved. Disclosures All authors: No reported disclosures.