Optimizing empiric antibiotic therapy in patients with severe β-lactam allergy

Fluoroquinolone resistance among fecal extended spectrum βeta lactamases positive Enterobacterales isolates from children in Dar es Salaam, Tanzania

BACKGROUND

Fluoroquinolones have been, and continue to be, routinely used for treatment of many bacterial infections. In recent years, most parts of the world have reported an increasing trend of fluoroquinolone resistant (FQR) Gram-negative bacteria.

METHODS

A cross-sectional study was conducted between March 2017 and July 2018 among children admitted due to fever to referral hospitals in Dar es Salaam, Tanzania. Rectal swabs were used to screen for carriage of extended-spectrum β-lactamase-producing Enterobacterales (ESBL-PE). ESBL-PE isolates were tested for quinolone resistance by disk diffusion method. Randomly selected fluroquinolone resistant isolates were characterized by using whole genome sequencing.

RESULTS

A total of 142 ESBL-PE archived isolates were tested for fluoroquinolone resistance. Overall phenotypic resistance to ciprofloxacin, levofloxacin and moxifloxacin was found in 68% (97/142). The highest resistance rate was seen among Citrobacter spp. (100%, 5/5), followed by Klebsiella. pneumoniae (76.1%; 35/46), Escherichia coli (65.6%; 42/64) and Enterobacter spp. (31.9%; 15/47). Whole genome sequencing (WGS) was performed on 42 fluoroquinolone resistant-ESBL producing isolates and revealed that 38/42; or 90.5%, of the isolates carried one or more plasmid mediated quinolone resistance (PMQR) genes. The most frequent PMQR genes were aac(6')-lb-cr (74%; 31/42), followed by qnrB1 (40%; 17/42), oqx, qnrB6 and qnS1. Chromosomal mutations in gyrA, parC and parE were detected among 19/42 isolates, and all were in E. coli. Most of the E. coli isolates (17/20) had high MIC values of > 32 µg/ml for fluoroquinolones. In these strains, multiple chromosomal mutations were detected, and all except three strains had additional PMQR genes. Sequence types, ST131 and ST617 predominated among E. coli isolates, while ST607 was more common out of 12 sequence types detected among the K. pneumoniae. Fluoroquinolone resistance genes were mostly associated with the IncF plasmids.

CONCLUSION

The ESBL-PE isolates showed high rates of phenotypic resistance towards fluoroquinolones likely mediated by both chromosomal mutations and PMQR genes. Chromosomal mutations with or without the presence of PMQR were associated with high MIC values in these bacteria strains. We also found a diversity of PMQR genes, sequence types, virulence genes, and plasmid located antimicrobial resistance (AMR) genes towards other antimicrobial agents.

Aerosol inhalation delivery of cefazolin in mice: Pharmacokinetic measurements and antibacterial effect

Aerosol inhalation delivery of cefazolin, a broad-spectrum first-generation cephalosporin antibiotic, was investigated. Inhalation system based on ultrasonic nebulizer was developed for the generation of dry cefazolin aerosol within mean particle diameter range 0.5-3.0 μm and mass concentration 0.01-3 μg/cm³. Pharmacokinetic measurements were carried out for the aerosolized form of cefazolin delivered in mice using nose-only chamber. Cefazolin concentrations in blood serum and in the lungs of mice were measured as a function of time by means of high performance liquid chromatography. Body-delivered dose depending on particle size, concentration and inhalation time as well as other pharmacokinetic parameters were determined. The antibacterial effect of aerosolized cefazolin was assessed through the aerosol inhalation treatment of mice infected with Klebsiella pneumoniae. Survival rate for infected mice after the treatment with cefazolin aerosol demonstrated high antibacterial efficiency of the inhalation delivery of cefazolin in comparison with intraperitoneal delivery.

Why Was There Ever a Warning Not to Use Cephalosporins in the Setting of a Penicillin "Allergy"?

It is now well-established that avoiding β-lactam antibiotics, when they are the drugs of choice, results in significantly worse long-term global outcomes for patients. Much of this avoidable morbidity has been caused by widespread warnings in electronic health care record systems not to use cephalosporins in the setting of penicillin allergy. High rates, up to 1000-fold higher than now seen, of immunologically mediated reactions were associated with early impure penicillin preparations. This instilled a rational fear of β-lactam-associated anaphylaxis in generations of physicians. In the late 1970s, several editorial comments regarding a potential increased risk to patients given cephalosporins who had a history of a penicillin allergy resulted in the warning that became imbedded in the culture of medicine. Over the past 40 years, compelling data have been developed that refute this warning and showed that the risks of avoiding cephalosporins outweighed the benefits. In late 2017, Kaiser Permanente Southern California completely removed all warnings not to use cephalosporins in the setting of a penicillin allergy. The results have recently been published in JAMA Network Open. This Rostrum article provides some of the backstory on the establishment and removal of this warning for physicians who trained over the past 30 years.

Empiric aztreonam is associated with increased mortality compared to beta-lactams in septic shock

PURPOSE

To determine if aztreonam as initial empiric treatment of adult septic shock is associated with increased mortality compared to the use of anti-pseudomonal beta-lactam agents.

METHODS

This was a multicenter, retrospective cohort study of 582 adult emergency department patients admitted to 12 acute care facilities within a single health system from January 2014 to December 2017 with septic shock receiving either aztreonam or an anti-pseudomonal beta-lactam for empiric treatment and discharged with an infection-related ICD-9 or ICD-10 code. The primary endpoint was in-hospital mortality.

RESULTS

Initial exposure to aztreonam was associated with increased hospital mortality compared to treatment with an anti-pseudomonal beta-lactam agent (22.7% vs. 12.9%, OR = 1.98, 95% CI: 1.27-3.11). When adjusted for APACHE II score, the treatment group effect on mortality remained statistically significant (OR = 1.74, 95% CI: 1.08-2.80). Aztreonam use was also associated with increased utilization of aminoglycosides (28.9% vs. 12.4%, p < 0.0001) and fluoroquinolones (50.5% vs. 25.8%, p < 0.01). There was no difference in hospital or intensive care unit length of stay in surviving patients between the two groups.

CONCLUSIONS

Compared to anti-pseudomonal beta-lactams, empiric treatment with aztreonam is associated with increased mortality and greater antibiotic exposure among patients with acute septic shock. These findings suggest that treatment with anti-pseudomonal beta-lactams should be prioritized over allergy avoidance whenever feasible.

Empirical fluoroquinolones versus broad-spectrum beta-lactams for Gram-negative bloodstream infections in the absence of antimicrobial resistance risk factors

OBJECTIVES

Increasing antimicrobial resistance rates limit empirical antimicrobial treatment options for Gram-negative bloodstream infections (GN-BSI). However, antimicrobial resistance may be predicted based on patient-specific risk factors using precision medicine concepts. This retrospective, 1:2 matched cohort examined clinical outcomes in hospitalized adults without major risk factors for antimicrobial resistance receiving empirical fluoroquinolones or broad-spectrum beta-lactams (BSBL) for GN-BSI at Prisma Health-Midlands hospitals in Columbia, SC, USA from January 2010 through June 2015.

METHODS

Multivariable logistic regression was used to examine early treatment failure at 72-96 h from GN-BSI. Cox proportional hazards regression was used to examine 28-day mortality and hospital length of stay (HLOS).

RESULTS

Among 74 and 148 patients receiving empirical fluoroquinolones and BSBL for GN-BSI, respectively, median age was 68 years, 159 (72%) were women, and 152 (68%) had a urinary source of infection. Early treatment failure rates were comparable in fluoroquinolone and BSBL groups (27% vs. 30%, respectively, odds ratio 0.82, 95% confidence intervals [CI] 0.43-1.54, P = 0.53), as well as 28-day mortality (8.9% vs. 9.7%, respectively, hazards ratio [HR] 0.74, 95% CI 0.26-1.90, P = 0.54). Median HLOS was 6.1 days in the fluoroquinolone group and 7.1 days in the BSBL group (HR 0.73, 95% CI 0.54-0.99, P = 0.04). Transition from intravenous to oral therapy occurred sooner in the fluoroquinolone group than in the BSBL group (3.0 vs. 4.9 days, P < 0.001).

CONCLUSIONS

In the absence of antimicrobial resistance risk factors, fluoroquinolones provide an additional empirical treatment option to BSBL for GN-BSI. Shorter HLOS in the fluoroquinolone group may be due to earlier transition from intravenous to oral antimicrobial therapy.

Adequacy of empiric gram-negative coverage for septic patients at an academic medical center

BACKGROUND

Gram-negative organisms (GNOs) have increasing resistance rates to levofloxacin at Virginia Commonwealth University Health System (VCUHS), where levofloxacin is the most common agent added to provide double coverage of gram-negative infections. The goal of this study was to determine the adequacy of empiric gram-negative coverage for septic patients at our institution.

METHODS

A retrospective review of patients admitted to VCUHS, from January 1, 2014, to December 31, 2014, with a diagnosis of sepsis, severe sepsis, or septic shock and documented infection, was performed to determine the adequacy of various empiric antibiotic combinations.

RESULTS

Of 219 patients who met the inclusion criteria, 56% of patients received monotherapy and 21% of patients received combination therapy (2 antibiotics) covering GNOs. GNOs (84%) were susceptible to piperacillin-tazobactam. When used in combination with cefepime and meropenem, levofloxacin did not increase coverage. However, levofloxacin provided an 8% increase in coverage and gentamicin provided an additional 13% increase in coverage, respectively, when used in combination with piperacillin-tazobactam.

CONCLUSIONS

Among septic patients at VCUHS, gentamicin provided increased gram-negative coverage when compared with levofloxacin. Although susceptibility to piperacillin-tazobactam alone was relatively low, the combination of piperacillin-tazobactam and gentamicin provided nearly equivalent coverage to meropenem and gentamicin.

Adherence to antibiotic guidelines and reported penicillin allergy: pooled cohort data on prescribing and allergy documentation from two English National Health Service (NHS) trusts

OBJECTIVE

To investigate documentation of antimicrobial allergy and to determine prescribing adherence to local antibiotic guidelines for inpatients with and without reported penicillin allergy treated for infection in a National Health Service (NHS) context.

SETTING

Data were collected at two English hospital NHS trusts over two time-periods: June 2016 and February 2017.

DESIGN

Cohort study. Trust 1 data were sourced from prospective point prevalence surveys. Trust 2 data were extracted retrospectively from an electronic report.

PARTICIPANTS

Inpatients treated for urinary tract infection (UTI), community-acquired pneumonia (CAP), hospital-acquired pneumonia (HAP) and skin and soft tissue infection (SSTI). Data on allergy were collected, and antibiotic selection assessed for adherence to trust guidelines with differences between groups presented as adjusted ORs.

RESULTS

A total of 1497 patients were included, with 2645 antibiotics orders. Patients were treated for CAP (n=495; 33.1%), UTI (407; 27.2%), HAP (330; 22%) and SSTI (265; 17.7%). There were 240 (16%) patients with penicillin allergy. Penicillin allergy was recorded as allergy (n=52; 21.7%), side effect (27; 11.3%) and no documentation (161; 67.1%). Overall, 2184 (82.6%) antibiotic orders were guideline-adherent. Adherence was greatest for those labelled penicillin allergy (453 of 517; 87.6%) versus no allergy (1731 of 2128; 81.3%) (OR 0.52 (95% CI 0.37 to 0.73) p<0.001). Guideline-adherence for CAP was higher if penicillin allergy (151 of 163; 92.6%) versus no allergy (582 of 810; 71.9%) (OR 0.20 (95% CI 0.10 to 0.37) p<0.001). There was no difference in adherence between those with and without penicillin allergy for UTI, HAP or SSTI treatment.

CONCLUSIONS

A relatively high proportion of patients had a penicillin allergy and two thirds of these had no description of their allergy, which has important implications for patient safety. Patients with penicillin allergy treated for CAP, received more guideline adherent antibiotics than those without allergy. Future studies investigating the clinical impact of penicillin allergy should include data on adherence to antibiotic guidelines.

Predicting Resistance to Piperacillin-Tazobactam, Cefepime and Meropenem in Septic Patients With Bloodstream Infection Due to Gram-Negative Bacteria

Background

Predicting antimicrobial resistance in gram-negative bacteria (GNB) could balance the need for administering appropriate empiric antibiotics while also minimizing the use of clinically unwarranted broad-spectrum agents. Our objective was to develop a practical prediction rule able to identify patients with GNB infection at low risk for resistance to piperacillin-tazobactam (PT), cefepime (CE), and meropenem (ME).

Methods

The study included adult patients with sepsis or septic shock due to bloodstream infections caused by GNB admitted between 2008 and 2015 from Barnes-Jewish Hospital. We used multivariable logistic regression analyses to describe risk factors associated with resistance to the antibiotics of interest (PT, CE, and ME). Clinical decision trees were developed using the recursive partitioning algorithm CHAID (χ2 Automatic Interaction Detection).

Results

The study included 1618 consecutive patients. Prevalence rates for resistance to PT, CE, and ME were 28.6%, 21.8%, and 8.5%, respectively. Prior antibiotic use, nursing home residence, and transfer from an outside hospital were associated with resistance to all 3 antibiotics. Resistance to ME was specifically linked with infection attributed to Pseudomonas or Acinetobacter spp. Discrimination was similar for the multivariable logistic regression and CHAID tree models, with both being better for ME than for PT and CE. Recursive partitioning algorithms separated out 2 clusters with a low probability of ME resistance and 4 with a high probability of PT, CE, and ME resistance.

Conclusions

With simple variables, clinical decision trees can be used to distinguish patients at low, intermediate, or high risk of resistance to PT, CE, and ME.

The 3 Cs of Antibiotic Allergy-Classification, Cross-Reactivity, and Collaboration

Antibiotic allergy labeling is highly prevalent and negatively impacts patient outcomes and antibiotic appropriateness. Reducing the prevalence and burden of antibiotic allergies requires the engagement of key stakeholders such as allergists, immunologists, pharmacists, and infectious diseases physicians. To help address this burden of antibiotic allergy overlabeling, we review 3 key antibiotic allergy domains: (1) antibiotic allergy classification, (2) antibiotic cross-reactivity, and (3) multidisciplinary collaboration. We review the available evidence and research gaps of currently used adverse drug reaction classification systems, antibiotic allergy cross-reactivity, and current and future models of antibiotic allergy care.

Development of Institutional Guidelines for Management of Gram-Negative Bloodstream Infections: Incorporating Local Evidence

Background: Appropriate empirical antimicrobial therapy is associated with improved outcomes of patients with Gram-negative bloodstream infections (BSI). Objective: Development of evidence-based institutional management guidelines for empirical antimicrobial therapy of Gram-negative BSI. Methods: Hospitalized adults with Gram-negative BSI in 2011-2012 at Palmetto Health hospitals in Columbia, SC, USA, were identified. Logistic regression was used to examine the association between site of infection acquisition and BSI due to Pseudomonas aeruginosa or chromosomally mediated AmpC-producing Enterobacteriaceae (CAE). Antimicrobial susceptibility rates of bloodstream isolates were stratified by site of acquisition and acute severity of illness. Retained antimicrobial regimens had predefined susceptibility rates ≥90% for noncritically ill and ≥95% for critically ill patients. Results: Among 390 patients, health care-associated (odds ratio [OR]: 3.0, 95% confidence interval [CI]: 1.5-6.3] and hospital-acquired sites of acquisition (OR: 3.7, 95% CI: 1.6-8.4) were identified as risk factors for BSI due to P aeruginosa or CAE, compared with community-acquired BSI (referent). Based on stratified bloodstream antibiogram, ceftriaxone met predefined susceptibility criteria for community-acquired BSI in noncritically ill patients (95%). Cefepime and piperacillin-tazobactam monotherapy achieved predefined susceptibility criteria in noncritically ill (95% both) and critically ill patients with health care-associated and hospital-acquired BSI (96% and 97%, respectively) and critically ill patients with community-acquired BSI (100% both). Conclusions: Incorporation of site of acquisition, local antimicrobial susceptibility rates, and acute severity of illness into institutional guidelines provides objective evidence-based approach for optimizing empirical antimicrobial therapy for Gram-negative BSI. The suggested methodology provides a framework for guideline development in other institutions.

Effectiveness of oral antibiotics for definitive therapy of Gram-negative bloodstream infections

There is paucity of data evaluating intravenous-to-oral antibiotic switch options for Gram-negative bloodstream infections (BSIs). This retrospective cohort study examined the effectiveness of oral antibiotics for definitive treatment of Gram-negative BSI. Patients with Gram-negative BSI hospitalised for <14 days at Palmetto Health Hospitals in Columbia, SC, from 1 January 2010 through 31 December 2013 and discharged on oral antibiotics were included in this study. The cohort was stratified into three groups based on bioavailability of oral antibiotics prescribed (high, ≥95%; moderate, 75-94%; and low, <75%). Kaplan-Meier analysis and multivariate Cox proportional hazards regression were used to examine treatment failure. Among the 362 patients, high, moderate and low bioavailability oral antibiotics were prescribed to 106, 179 and 77 patients, respectively, for definitive therapy of Gram-negative BSI. Mean patient age was 63 years, 217 (59.9%) were women and 254 (70.2%) had a urinary source of infection. Treatment failure rates were 2%, 12% and 14% in patients receiving oral antibiotics with high, moderate and low bioavailability, respectively (P = 0.02). Risk of treatment failure in the multivariate Cox model was higher in patients receiving antibiotics with moderate [adjusted hazard ratio (aHR) = 5.9, 95% CI 1.6-38.5; P = 0.005] and low bioavailability (aHR = 7.7, 95% CI 1.9-51.5; P = 0.003) compared with those receiving oral antimicrobial agents with high bioavailability. These data demonstrate the effectiveness of oral antibiotics with high bioavailability for definitive therapy of Gram-negative BSI. Risk of treatment failure increases as bioavailability of the oral regimen declines.

Prediction of Fluoroquinolone Resistance in Gram-Negative Bacteria Causing Bloodstream Infections

Increasing rates of fluoroquinolone resistance (FQ-R) have limited empirical treatment options for Gram-negative infections, particularly in patients with severe beta-lactam allergy. This case-control study aims to develop a clinical risk score to predict the probability of FQ-R in Gram-negative bloodstream isolates. Adult patients with Gram-negative bloodstream infections (BSI) hospitalized at Palmetto Health System in Columbia, South Carolina, from 2010 to 2013 were identified. Multivariate logistic regression was used to identify independent risk factors for FQ-R. Point allocation in the fluoroquinolone resistance score (FQRS) was based on regression coefficients. Model discrimination was assessed by the area under receiver operating characteristic curve (AUC). Among 824 patients with Gram-negative BSI, 143 (17%) had BSI due to fluoroquinolone-nonsusceptible Gram-negative bacilli. Independent risk factors for FQ-R and point allocation in FQRS included male sex (adjusted odds ratio [aOR], 1.97; 95% confidence intervals [CI], 1.36 to 2.98; 1 point), diabetes mellitus (aOR, 1.54; 95% CI, 1.03 to 2.28; 1 point), residence at a skilled nursing facility (aOR, 2.28; 95% CI, 1.42 to 3.63; 2 points), outpatient procedure within 30 days (aOR, 3.68; 95% CI, 1.96 to 6.78; 3 points), prior fluoroquinolone use within 90 days (aOR, 7.87; 95% CI, 4.53 to 13.74; 5 points), or prior fluoroquinolone use within 91 to 180 days of BSI (aOR, 2.77; 95% CI, 1.17 to 6.16; 3 points). The AUC for both final logistic regression and FQRS models was 0.73. Patients with an FQRS of 0, 3, 5, or 8 had predicted probabilities of FQ-R of 6%, 22%, 39%, or 69%, respectively. The estimation of patient-specific risk of antimicrobial resistance using FQRS may improve empirical antimicrobial therapy and fluoroquinolone utilization in Gram-negative BSI.

Impact of fluoroquinolone resistance in Gram-negative bloodstream infections on healthcare utilization

There has been a concerning increase in fluoroquinolone resistance among Gram-negative bloodstream isolates. This retrospective cohort study examines the implications of fluoroquinolone resistance on use of healthcare resources in patients with Gram-negative bloodstream infections (BSI). Hospitalized adults with first episodes of community-onset Gram-negative BSI from 2010 to 2012 at Palmetto Health Hospitals in Columbia, SC, USA were identified. Multivariate linear regression was used to examine risk factors for prolonged hospital length of stay (HLOS) in survivors of Gram-negative BSI. Among 474 unique patients, 384 (81%) and 90 (19%) had BSI due to fluoroquinolone-susceptible (FQ-S) and fluoroquinolone non-susceptible (FQ-NS) Gram-negative bacilli, respectively. The FQ-NS bloodstream isolates, particularly Escherichia coli, were more likely than FQ-S isolates to be multi-drug resistant (56% versus 6%, p < 0.001). Compared with patients with BSI due to FQ-S bloodstream isolates, those with FQ-NS isolates were more likely to receive inappropriate empirical antimicrobial therapy (26% versus 3%, p < 0.001), have longer mean HLOS (11.6 versus 9.3 days, p 0.03) and treatment duration with intravenous antibiotics during hospitalization (9.1 versus 7.1 days, p 0.001), and use outpatient intravenous antibiotics at hospital discharge (15% versus 8%, p 0.05). After adjustments in the multivariate model, inappropriate empirical antimicrobial therapy was an independent risk factor for prolonged HLOS in survivors of Gram-negative BSI (parameter estimate 3.65 days, 95% CI 0.43-6.86). Multi-drug resistance among FQ-NS bloodstream isolates limits both empirical and definitive antimicrobial treatment options and poses excessive burdens on the healthcare system.

Stratification of the impact of inappropriate empirical antimicrobial therapy for Gram-negative bloodstream infections by predicted prognosis

The bloodstream infection mortality risk score (BSIMRS) predicts the outcome of patients with Gram-negative bloodstream infections (BSI) with high discrimination. This retrospective cohort study examined the impact of inappropriate antimicrobial therapy on mortality in adult patients with Gram-negative BSI admitted to Palmetto Health Hospitals in Columbia, SC, USA, from 1 January 2011 to 31 December 2012 after stratification by predicted prognosis at initial presentation using BSIMRS. A multivariate Cox regression model was used to identify independent risk factors for 28-day mortality overall and within each predefined BSIMRS category (<5, 5 to 9, and ≥ 10). Relative risk reduction (RRR), absolute risk reduction (ARR), and number needed to treat (NNT) were calculated from a predictive logistic regression model of mortality. Overall, 390 unique patients with first episodes of Gram-negative BSI were identified. The median age was 66 years, and 229 (59%) were women. There was significant association between inappropriate antimicrobial therapy and mortality in patients with BSIMRS of 5 to 9 (adjusted hazard ratio [aHR], 3.55; 95% confidence intervals [CI], 1.22 to 8.31; P = 0.02) and BSIMRS of ≥ 10 (aHR, 4.99; 95% CI, 1.09 to 22.87; P = 0.04) but not in those with BSIMRS of <5 (aHR, 3.34; 95% CI, 0.17 to 22.77; P = 0.34). RRR, ARR, and NNT were 0.25, 0.02, and 63 for BSIMRS of <5; 0.56, 0.32, and 3 for BSIMRS of 5 to 9; and 0.39, 0.39, and 3 for BSIMRS of ≥ 10, respectively. There is a significant benefit from appropriate antimicrobial therapy in patients with Gram-negative BSI with guarded (BSIMRS of 5 to 9) and poor (BSIMRS of ≥ 10) predicted prognosis. Survival difference remains unclear among those with good predicted prognosis (BSIMRS of <5) at initial presentation.