Outcome of cephalosporin treatment for serious infections due to apparently susceptible organisms producing extended-spectrum beta-lactamases: implications for the clinical microbiology laboratory

Surveillance and Resistance of Community-Onset Extended-Spectrum β-Lactamase-Producing Escherichia coli and Klebsiella pneumonia in Oral and Maxillofacial Surgery Site Infections

Background: The prevalence of community-onset infections of extended spectrum β-lactamase (ESBL)-producing strains has increased globally, yet surveillance and resistance in patients with oral and maxillofacial surgery site infections is less investigated. Patients and Methods: A retrospective cohort study was performed to investigate risk factors and resistance of ESBL-producing Escherichia coli (ESBL-EC) and ESBL-producing Klebsiella pneumonia (ESBL-KP) among community-onset patients with oral and maxillofacial surgery during January 2010 to December 2016. Demographic features, predisposing factors, clinical outcomes, and antibiotic agent costs were analyzed. Antimicrobial susceptibility testing of nine antimicrobial agents against ESBL-KP and ESBL-EC were measured. Results: Among 2,183 cultures from infection sites in patients with oral and maxillofacial surgery site (45 cases [2.06%]) were confirmed with community-onset ESBL-KP (24; 1.10%) or ESBL-EC (21; 0.96%) infection. Multivariable analysis showed the independent risk factors for ESBL-producing bacterial infection were prior history of hospitalization (adjusted odds ratio [aOR], 10.984; 95% confidence interval [CI], 5.965-59.879; p = 0.025) and malignant condition (aOR, 3.373; 95% CI 2.947-7.634; p = 0.024). Based on antimicrobial susceptibility testing, 57.8% ESBL-KP and ESBL-EC were found receiving inappropriate antimicrobial therapy, and antibiotic agent costs were higher than non-ESBL-producing bacterial infections ($493.8 ± $367.3 vs. $304.1 ± $334.7; p = 0.031). Conclusions: Infections caused by ESBL-KP and ESBL-EC among patients in sites with oral and maxillofacial surgery are associated with prior history of hospitalization and malignant conditions. Prompt detection and appropriate antibiotic administration for community-onset infections of ESBLs are necessary for such populations.

Pharmacokinetic Analysis of Intravenous Push Cefepime in Burn Patients with Augmented Renal Clearance

Patients with augmented renal clearance (ARC) are a subset of critically ill patients including burn patients that exhibit increased renal elimination of medications beyond that of similarly injured patients. Currently approved maximum regimens of medications primarily eliminated by the kidney, such as cefepime (>90% unchanged in the urine), may be inadequate (eg, compromising the bactericidal activity of cefepime) in patients with ARC. Due to recent resource limitations, centers have changed infusion practices of commonly prescribed medications to intravenous push (IVP), potentially exacerbating the problem of maintaining bactericidal cefepime concentrations. The hypothesis of the study was patients with ARC are not currently achieving adequate target attainment, when receiving cefepime 2 g every 8 h IVP. Eight blood samples were collected from each patient, and concentrations measured via LC-MS/MS. WinNonlin (version 8.3) was used to estimate the pharmacokinetic parameters of cefepime and simulate plasma concentrations of cefepime in each of the ten subjects. Simulations of cefepime plasma concentrations produced by a 2 g dose given every 8 h and a 1 g dose given every 4 h were performed and the time above a MIC of 4 mg/L, 8 mg/L, and 16 mg/L compared. The 2 g every 8 h regimen remained above the breakpoints for 92%, 85%, and 71% of the dosing interval, respectively. The 1 g every 4 h regimen remained above the same breakpoints at a frequency of 100%, 99%, and 92% of the dosing interval. Giving cefepime 1 g every 4 h is a simple approach to increase the likelihood of maintaining the optimal bactericidal activity of cefepime in patients with ARC.

Carbon Dots from Tire Waste for the Photodegradation of Methyl Orange Dye, Antimicrobial Activity, and Molecular Docking Study

In this study, solvothermal pathway was employed for the synthesis of P, N codoped C-dot using tire waste as a sustainable source of carbon and nitrogen. Comprehensive analyses encompassing X-ray diffraction (XRD) analysis, Transmission Electron Microscopy (TEM), FT-IR, cyclic voltammetry, and UV-Vis spectra were used to assess the crystalline structure, purity, size, fluorescence up-conversion, and morphological attributes of the nanomaterial. Subsequently, the produced C-dots were evaluated for their efficacy in the photocatalytic degradation of methylene blue and methyl orange dyes, demonstrating notable success in degrading methyl orange dye within eight hours in the visible region. Furthermore, the same nanomaterial was applied for carrying out agar disk-diffusion assays against a spectrum of microorganisms. Results revealed substantial inhibition zones against Methicillin-Resistant Staphylococcus aureus (MRSA), Escherichia coli, and Pseudomonas aeruginosa. Elucidating the antimicrobial mechanism, molecular-docking simulations were excuted using on AutoDock Vina with designated ligands. The results indicated a strong binding affinity of the C-dots with certain proteins associated with antibacterial activity. This observation suggests that the synthesized C-dots effectively engage with the active sites of these proteins, indicating their potential as promising antibacterial agents. Importantly, this study implies that C-dots do not induce protein denaturation, thereby warranting further investigation of their utility as antibacterial agents.

Hydrothermal Synthesis of Fe-Doped Cadmium Oxide Showed Bactericidal Behavior and Highly Efficient Visible Light Photocatalysis

Cationic dyes present in industrial effluents significantly reduce the effectiveness of remediation operations. Considering the terrible impact of these pollutants on environment and biodiversity, investigating strategies to remove potentially harmful compounds from water is becoming an increasingly intriguing issue. In this work, we employed a simple hydrothermal technique to synthesize Fe-doped CdO (2, 4, and 6 wt %) nanostructures and assessed their efficacy in degrading methylene blue (MB) dye and inhibiting the growth of Staphylococcus aureus and Escherichia coli, respectively. Structural, morphological, and optical characterization of produced nanomaterials was also performed using X-ray diffraction, TEM, and UV absorption spectra. The photocatalytic decomposition of MB was significantly enhanced (58.8%) by using Fe (6 wt %)-doped CdO catalysts for 80 min under irradiation. In addition, 2.05-5.05 mm inhibitory zones were seen against Gram-positive bacteria (S. aureus), whereas the range for Gram-negative bacteria (E. coli) was 1.65-2.75 mm. These nanostructures were shown to be very effective inhibitors of beta-lactamase, d-alanine-d-alanine ligase B, and fatty acid synthase inhibitor by in silico molecular docking investigations.

Study of Plasmid-Mediated Extended-Spectrum Beta-Lactamase-Producing Clinical Strains of Enterobacteriaceae From Tabuk Region

BACKGROUND

Extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae threaten infection treatment globally. This study aims to assess ESBLs-E prevalence and multidrug-resistant organisms (MDR) in clinical specimens from Tabuk, KSA.

METHODS

A cross-sectional research was carried out in March-May 2023. A collective of 90 Enterobacteriaceae isolates were identified from clinical specimens. The specimen was identified by standard methods. The Enterobacteriaceae member was screed for ESBL production by screening and confirmatory as per the Clinical and Laboratory Standards Institute (CLSI).

RESULT

E. coli was the most common isolate, followed by Proteus mirabilis and Citrobacter sp, Klebsiella oxytoca, Klebsiella pneumonia, Proteus vulgaris and Morganella morganii. Among the sample, the majority of isolates were from urine (47.8%) followed by pus (25.6%) and the least from other body fluids (6.7%). The E. coli showed the highest average antibiotic resistance (73.7%) among all the antibiotics used followed by P. mirabilis (70.4%), K. pneumoniae (70%), P. vulgaris (69.8%), M. morganii and Citrobacter (69.4% both), and K. oxytoca (68.8%). There was a 41.2% average reduction in ESBL positivity from phenotypic to confirmatory test results. The highest reduction was observed among M. morganii (66.7%) and the least was observed in E. coli (17.1%).

CONCLUSION

Most of the ESBL-producing isolates were found mainly in blood and urine samples. The most frequent ESBL-producing Enterobacteriaceae were K. pneumoniae and E. coli. The best options for treating Enterobacteriaceae that produce ESBL are Amoxicillin, Amikacin, and Cefoxitin. ESBL-producing isotopes showed a high resistance rate to cefepime and cefotaxime compared to non-ESBL producers. It is of utmost importance to implement reliable infection control measures in healthcare institutions nationwide.

Outcomes associated with empiric cefepime for bloodstream infections caused by ceftriaxone-resistant, cefepime-susceptible Escherichia coli and Klebsiella pneumoniae

BACKGROUND

Cefepime is a first-line agent for empiric sepsis therapy; however, cefepime use may be associated with increased mortality for extended-spectrum beta-lactamase-producing Enterobacterales (ESBL-E) in an MIC-dependent manner. This study aimed to compare the efficacy of empiric cefepime versus meropenem for bloodstream infections (BSI) caused by ceftriaxone-resistant Escherichia coli and Klebsiella pneumoniae with cefepime MICs ≤ 2 mg/L.

METHODS

This single-center retrospective cohort study included patients admitted from October 2010 to August 2020 who received cefepime or meropenem empirically for sepsis with a blood culture growing ceftriaxone-resistant Escherichia coli or Klebsiella pneumoniae. The primary outcome was 30-day mortality; secondary endpoints included 14-day mortality, recurrent BSI, readmission and recurrent infection within 90 days, time to clinical resolution of infection, time to clinical stability, and clinical stability at 48 hours.

RESULTS

Fifty-four patients met inclusion criteria: 36 received meropenem and 18 received cefepime. The median (IQR) treatment durations of cefepime and meropenem were 3 (2-6) days and 7 (5-10) days, respectively. Thirty-day and 14-day mortality were similar between cefepime and meropenem (11.1% vs. 2.8%; P = 0.255 and 5.6% vs. 2.8%; P = 1.00, respectively). Cefepime was associated with longer time to clinical stability compared with meropenem (median 38.48 hours vs. 21.26; P = 0.016).

CONCLUSION

Mortality was similar between groups, although most patients who received cefepime empirically were ultimately transitioned to a carbapenem to complete the full treatment course. Empiric cefepime was associated with a delay in achieving clinical stability when compared with meropenem to treat BSI caused by ceftriaxone-resistant Enterobacterales, even when cefepime-susceptible.

Phenotypes, genotypes and breakpoints: an assessment of β-lactam/β-lactamase inhibitor combinations against OXA-48

BACKGROUND

Two of the three recently approved β-lactam agent (BL)/β-lactamase inhibitor (BLI) combinations have higher CLSI susceptibility breakpoints (ceftazidime/avibactam 8 mg/L; meropenem/vaborbactam 4 mg/L) compared with the BL alone (ceftazidime 4 mg/L; meropenem 1 mg/L). This can lead to a therapeutic grey area on susceptibility reports depending on resistance mechanism. For instance, a meropenem-resistant OXA-48 isolate (MIC 4 mg/L) may appear as meropenem/vaborbactam-susceptible (MIC 4 mg/L) despite vaborbactam's lack of OXA-48 inhibitory activity.

METHODS

OXA-48-positive (n = 51) and OXA-48-negative (KPC, n = 5; Klebsiella pneumoniae wild-type, n = 1) Enterobacterales were utilized. Susceptibility tests (broth microdilution) were conducted with ceftazidime/avibactam, imipenem/relebactam and meropenem/vaborbactam, as well as their respective BL partner. Antimicrobial activity of all six agents was evaluated in the murine neutropenic thigh model using clinically relevant exposures. Efficacy was assessed as the change in bacterial growth at 24 h, compared with 0 h controls.

RESULTS

On average, the three BL/BLI agents resulted in robust bacteria killing among OXA-48-negative isolates. Among OXA-48-positive isolates, poor in vivo activity with imipenem/relebactam was concordant with its resistant phenotypic profile. Variable meropenem/vaborbactam activity was observed among isolates with a 'susceptible' MIC of 4 mg/L. Only 30% (7/23) of isolates at meropenem/vaborbactam MICs of 2 and 4 mg/L met the ≥1-log bacterial reduction threshold predictive of clinical efficacy in serious infections. In contrast, ceftazidime/avibactam resulted in marked bacterial density reduction across the range of MICs, and 96% (49/51) of isolates exceeded the ≥1-log bacterial reduction threshold.

CONCLUSIONS

Data demonstrate that current imipenem/relebactam and ceftazidime/avibactam CLSI breakpoints are appropriate. Data also suggest that higher meropenem/vaborbactam breakpoints relative to meropenem can translate to potentially poor clinical outcomes in patients infected with OXA-48-harbouring isolates.

Graphitic-C3N4/chitosan-doped NiO nanostructure to treat the polluted water and their bactericidal with in silico molecular docking analysis

Different concentrations (2 and 4 wt%) of graphite carbon nitride (g-C3N4) was doped into fixed amount of chitosan (CS) and nickel oxide (NiO) nanoparticles (NPs) via a co-precipitation route. The aim of study is to remove the pollutants from wastewater through catalytic activity (CA) and determine the bactericidal activities of synthesized products. X-ray diffraction pattern confirmed the cubic structure of NiO NPs and peak shifted to higher angle upon g-C3N4 doping. Fourier transform infrared spectroscopy revealed the existence of bending and stretching vibration mode. The absorption decreased gradually accompanied blue-shift and assessed bandgap energy increased upon doping. The high resolution transmission electron microscopy micrographs confirmed the formation of cubic-shaped NPs and elongated nanorods were seen for NiO and co-doped NiO. The catalytic efficiency of samples was examined using methylene blue (MB) in the presence of reducing agent. A remarkable dye de-colorization was confirmed with a g-C3N4 and CS doping; moreover, the bactericidal efficacy compared to Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was observed as 3.15 and 13.8 mm, respectively. In silico, molecular docking investigations targeting against b-lactamaseS. aureus and FabHE. coli enzymes assisted to elaborate the mechanism underlying microbicidal action of the NPs.

Molecular typing methods & resistance mechanisms of MDR Klebsiella pneumoniae

The emergence and transmission of carbapenem-resistant Klebsiella pneumoniae (CRKP) have been recognized as a major public health concern. Here, we investigated the molecular epidemiology and its correlation with the mechanisms of resistance in CRKP isolates by compiling studies on the molecular epidemiology of CRKP strains worldwide. CRKP is increasing worldwide, with poorly characterized epidemiology in many parts of the world. Biofilm formation, high efflux pump gene expression, elevated rates of resistance, and the presence of different virulence factors in various clones of K. pneumoniae strains are important health concerns in clinical settings. A wide range of techniques has been implemented to study the global epidemiology of CRKP, such as conjugation assays, 16S-23S rDNA, string tests, capsular genotyping, multilocus sequence typing, whole-genome sequencing-based surveys, sequence-based PCR, and pulsed-field gel electrophoresis. There is an urgent need to conduct global epidemiological studies on multidrug-resistant infections of K. pneumoniae across all healthcare institutions worldwide to develop infection prevention and control strategies. In this review, we discuss different typing methods and resistance mechanisms to explore the epidemiology of K. pneumoniae pertaining to human infections.

Phenotypes, genotypes and breakpoints: an assessment of β-lactam/ β-lactamase inhibitor combinations against OXA-48

BACKGROUND

Two out of the three recently approved β-lactam (BL)/β-lactamase inhibitors (BLIs) have higher CLSI susceptibility breakpoints (ceftazidime/avibactam 8 mg/L; meropenem/vaborbactam 4 mg/L) compared with the BL alone (ceftazidime 4 mg/L; meropenem 1 mg/L). This can lead to a therapeutic grey area on susceptibility reports depending on resistance mechanism. For instance, a meropenem-resistant OXA-48 isolate (MIC 4 mg/L) may appear as meropenem/vaborbactam-susceptible (MIC 4 mg/L) despite vaborbactam's lack of OXA-48 inhibitory activity.

METHODS

OXA-48-positive (n = 51) and OXA-48-negative (KPC, n = 5; Klebsiella pneumoniae WT, n = 1) Enterobacterales were utilized. Susceptibility tests (broth microdilution) were conducted with ceftazidime/avibactam, imipenem/relebactam and meropenem/vaborbactam, as well as their respective BL partner. Antimicrobial activity of all six agents was evaluated in the murine neutropenic thigh model using clinically relevant exposures. Efficacy was assessed as the change in bacterial growth at 24 h, compared with 0 h controls.

RESULTS

On average, the three BL/BLI agents resulted in robust bacteria killing among OXA-48-negative isolates. Among OXA-48-positive isolates, poor in vivo activity with imipenem/relebactam was concordant with its resistant phenotypic profile. Variable meropenem/vaborbactam activity was observed among isolates with a 'susceptible' MIC of 4 mg/L. Only 30% (7/23) of isolates at meropenem/vaborbactam MICs of 2 and 4 mg/L met the ≥1 log bacterial reduction threshold predictive of clinical efficacy in serious infections. In contrast, ceftazidime/avibactam resulted in marked bacterial density reduction across the range of MICs and 73% (37/51) of isolates exceeded the ≥1 log bacterial reduction threshold.

CONCLUSIONS

Data demonstrate that current imipenem/relebactam and ceftazidime/avibactam CLSI breakpoints are appropriate. Data also suggest that higher meropenem/vaborbactam breakpoints relative to meropenem can translate to potentially poor clinical outcomes in patients infected with OXA-48-harbouring isolates.

Microfluidics for antibiotic susceptibility testing

The rise of antibiotic resistance is a threat to global health. Rapid and comprehensive analysis of infectious strains is critical to reducing the global use of antibiotics, as informed antibiotic use could slow down the emergence of resistant strains worldwide. Multiple platforms for antibiotic susceptibility testing (AST) have been developed with the use of microfluidic solutions. Here we describe microfluidic systems that have been proposed to aid AST. We identify the key contributions in overcoming outstanding challenges associated with the required degree of multiplexing, reduction of detection time, scalability, ease of use, and capacity for commercialization. We introduce the reader to microfluidics in general, and we analyze the challenges and opportunities related to the field of microfluidic AST.

Comparison of the Treatment Outcome of Piperacillin-Tazobactam versus Carbapenems for Patients with Bacteremia Caused by Extended-Spectrum β-Lactamase-Producing Escherichia coli in Areas with Low Frequency of Coproduction of OXA-1: a Preliminary Analysis

Although piperacillin-tazobactam (TZP) was shown to be less effective than carbapenems in treating bacteremia due to extended-spectrum β-lactamase-producing (ESBL)-producing organisms in a randomized controlled trial, the fact that many of the causative organisms co-produced inhibitor-resistant OXA-1 along with ESBLs may have influenced the results. In this study, we compared the therapeutic effectiveness of TZP and carbapenem in treating ESBL-producing Escherichia coli bacteremia in areas with low frequency of OXA-1 co-production. Forty patients, 14 in the TZP treatment group and 26 in the carbapenem treatment group, were included in the analysis. There were no significant differences in patient background between the two groups. Urinary tract infection or cholangitis was the source of bacteremia in 26 patients (65%), and the Pitt bacteremia score was zero or one in 35 patients (87.5%). Only four (11.4%) of the 35 causative isolates available for microbiological analysis harbored bla_OXA-1, and only three (8.6%) were non-susceptible to TZP. Seventeen (48.6%) isolates carried bla_CTX-M-27, none of which carried other β-lactamase genes. No significant difference in the frequency of treatment failure on day 14 of bacteremia was documented between the TZP and carbapenem treatment groups in both the crude analysis and the inverse probability of treatment weighting-adjusted analysis. This study demonstrates that TZP may be a treatment option for non-severe cases of ESBL-producing E. coli bacteremia in areas with low frequency of OXA-1 co-production. IMPORTANCE Although carbapenems are considered the drug of choice for severe infections caused by extended-spectrum β-lactamase-producing (ESBL)-producing organisms, other therapeutic options are being explored to avoid increasing the selective pressure for carbapenem-resistant organisms. In this study, it was suggested that piperacillin-tazobactam may be as effective as carbapenems for the treatment of mild bacteremia caused by ESBL-producing Escherichia coli in areas where OXA-1 co-production by ESBL-producing E. coli is rare. The genetic background of each regional epidemic clone differs even among multidrug-resistant bacteria classified under the same name (e.g., ESBL-producing organisms), resulting in possible differences in the efficacy of therapeutic agents. Exploration of treatment options for multidrug-resistant organisms according to local epidemiology is worthwhile from the perspective of antimicrobial stewardship.

Treatment and Epidemiology of Third-Generation Cephalosporin-Resistant Urinary Tract Infections

BACKGROUND AND OBJECTIVES

Limited data are available on the contemporary epidemiology, clinical management, and health care utilization for pediatric urinary tract infection (UTI) due to third-generation cephalosporin-resistant Enterobacterales (G3CR) in the United States. The objective is to describe the epidemiology, antimicrobial treatment and response, and health care utilization associated with G3CR UTI.

METHODS

Multisite, matched cohort-control study including children with G3CR UTI versus non-G3CR UTI. UTI was defined as per American Academy of Pediatrics guidelines, and G3CR as resistance to ceftriaxone, cefotaxime, or ceftazidime. We collected data from the acute phase of illness to 6 months thereafter.

RESULTS

Among 107 children with G3CR UTI and 206 non-G3CR UTI with documented assessment of response, the proportion with significant improvement on initial therapy was similar (52% vs 57%; odds ratio [OR], 0.81; 95% confidence interval [CI], 0.44-1.50). Patients with G3CR were more frequently hospitalized at presentation (38% vs 17%; OR, 3.03; 95% CI, 1.77-5.19). In the follow-up period, more patients with G3CR had urine cultures (75% vs 53%; OR, 2.61; 95% CI, 1.33-5.24), antimicrobial treatment of any indication (53% vs 29%; OR, 2.82; 95% CI, 1.47-5.39), and subspecialty consultation (23% vs 6%; OR, 4.52; 95% CI, 2.10-10.09). In multivariate analysis, previous systemic antimicrobial therapy remained a significant risk factor for G3CR UTI (adjusted OR, 1.91; 95% CI, 1.06-3.44).

CONCLUSIONS

We did not observe a significant difference in response to therapy between G3CR and susceptible UTI, but subsequent health care utilization was significantly increased.

Potential Antibiotics for the Treatment of Neonatal Sepsis Caused by Multidrug-Resistant Bacteria

Neonatal sepsis causes up to an estimated 680,000 deaths annually worldwide, predominantly in low- and middle-income countries (LMICs). A significant and growing proportion of bacteria causing neonatal sepsis are resistant to multiple antibiotics, including the World Health Organization-recommended empiric neonatal sepsis regimen of ampicillin/gentamicin. The Global Antibiotic Research and Development Partnership is aiming to develop alternative empiric antibiotic regimens that fulfil several criteria: (1) affordable in LMIC settings; (2) activity against neonatal bacterial pathogens, including extended-spectrum β-lactamase producers, gentamicin-resistant Gram-negative bacteria, and methicillin-resistant Staphylococcus aureus (MRSA); (3) a licence for neonatal use or extensive experience of use in neonates; and (4) minimal toxicities. In this review, we identify five antibiotics that fulfil these criteria: amikacin, tobramycin, fosfomycin, flomoxef, and cefepime. We describe the available characteristics of each in terms of mechanism of action, resistance mechanisms, clinical pharmacokinetics, pharmacodynamics, and toxicity profile. We also identify some knowledge gaps: (1) the neonatal pharmacokinetics of cefepime is reliant on relatively small and limited datasets, and the pharmacokinetics of flomoxef are also reliant on data from a limited demographic range and (2) for all reviewed agents, the pharmacodynamic index and target has not been definitively established for both bactericidal effect and emergence of resistance, with many assumed to have an identical index/target to similar class molecules. These five agents have the potential to be used in novel combination empiric regimens for neonatal sepsis. However, the data gaps need addressing by pharmacokinetic trials and pharmacodynamic characterisation.

The potential impact of discrepancies between automated susceptibility platforms and other testing metho`dologies for cefazolin in the treatment of Enterobacterales bloodstream infections

Revised breakpoints for cefazolin (CFZ) against Enterobacterales may be difficult to implement with current automated susceptibility testing platforms and could falsely report organisms as susceptible, leading to inappropriate treatment for bloodstream infections (BSI). This was a retrospective cohort of adult patients with Enterobacterales BSI reported CFZ susceptible per Vitek®2. The primary outcome was the percentage susceptible by minimum inhibitory concentration (MIC) Gradient Test Strips and disk diffusion. Secondary outcomes included clinical outcomes between CFZ and non-CFZ-treated patients. Among 195 isolates reported CFZ-susceptible per Vitek®2, 84 (43.1%) were CFZ susceptible by MIC Gradient Test Strips vs 119 (61%) by disk diffusion. No difference was noted in 30-day all-cause mortality, secondary complications, or 30-day readmissions. Treatment failure was less likely to occur with source control (adjusted OR 0.06) and infectious disease consult (adjusted OR 0.37). There was a large degree of discrepancy between automated testing and manual methods; the clinical impact of this discrepancy warrants further investigation.

An update on cefepime and its future role in combination with novel β-lactamase inhibitors for MDR Enterobacterales and Pseudomonas aeruginosa

Cefepime, a wide-spectrum β-lactam antibiotic, has been in use for the treatment of serious bacterial infections for almost 25 years. Since its clinical development, there has been a dramatic shift in its dosing, with 2 g every 8 hours being preferred for serious infections to optimize pharmacokinetic/pharmacodynamic considerations. The advent of ESBLs has become a threat to its ongoing use, although future coadministration with β-lactamase inhibitors (BLIs) under development is an area of intense study. There are currently four new cefepime/BLI combinations in clinical development. Cefepime/zidebactam is generally active against MBL-producing Enterobacterales and Pseudomonas aeruginosa, in vitro and in animal studies, and cefepime/taniborbactam has activity against KPC and OXA-48 producers. Cefepime/enmetazobactam and cefepime/tazobactam are potential carbapenem-sparing agents with activity against ESBLs. Cefepime/enmetazobactam has completed Phase III and cefepime/taniborbactam is in Phase III clinical studies, where they are being tested against carbapenems or piperacillin/tazobactam for the treatment of complicated urinary tract infections. While these combinations are promising, their role in the treatment of MDR Gram-negative infections can only be determined with further clinical studies.

Novel prism shaped C3N4-doped Fe@Co3O4 nanocomposites and their dye degradation and bactericidal potential with molecular docking study

Novel prism shaped C₃N₄-doped Fe@Co₃O₄ nanocomposites were fabricated via a co-precipitation route for effective removal of organic pollutants from water and for bactericidal applications. Doping of C₃N₄ in the heterojunction significantly enhanced the photocatalytic and sonocatalytic activity against methylene blue ciprofloxacin (MBCF) dye. The main purpose of doping Fe atoms in the cobalt lattice was to generate crystal and surface defects. Moreover, the optimum doping amount of C₃N₄ for maximum degradation performance was evaluated. A detailed examination of the prepared nanocomposites was carried out systematically using various characterization tools for better understanding. HR-TEM images revealed the formation of novel prism shaped structures that exhibited outstanding degradation of the organic dye in water. Significant bactericidal potential was also observed for the synthesized nanocomposites against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria. In silico, molecular docking studies against β-lactamase, DHFR and FabI enzymes served to elucidate the mechanism governing the bactericidal activity of the as-synthesized nanoparticles (NPs). Furthermore, a scavenging study by DPPH (2,2-diphenyl-1-picrylhydrazyl) assay and COD (chemical oxygen demand) analysis was performed in order to evaluate active species and the anti-oxidant potential of prepared composites.

This study provides new insights into the use of cobalt-based heterojunction photocatalysts for dye degradation and antibacterial applications (a) synthesis mechanism of C₃N₄ (b) schematic of synthesis route adopted for fabrication of nanocomposites.

CON: Testing for ESBL production is unnecessary for ceftriaxone-resistant Enterobacterales

Phenotypic testing for Enterobacterales that harbour ESBLs is not additive to accurate in vitro β-lactam MICs for clinical decision-making. ESBL testing is an outdated practice established in an era of higher cephalosporin breakpoints to prevent resistant Enterobacterales carrying Ambler class A β-lactamases with affinity for later-generation β-lactams from being reported as susceptible to later-generation cephalosporins, leading to clinical failures. ESBL testing is problematic because of inaccuracies when multiple classes of β-lactamases are produced by the same organism, thus limiting the testing application to specific species and resistance types. Clinical laboratories should instead focus finite resources on accurate susceptibility testing using contemporary interpretative criteria to help guide therapeutic decisions. With continued emergence of antimicrobial resistance and in the setting of accurate susceptibility testing and current breakpoints the use of ESBL phenotypic testing is not helpful in clinical decision-making.

Three is a crowd: Clinical outcomes of a twice daily versus a thrice daily metronidazole dosing strategy from a multicenter study

This was a multicenter, retrospective study of patients with anaerobic bacteremia comparing metronidazole 500mg every 8 hours versus 500mg every 12 hours. Of 782 patients reviewed, 85 met inclusion criteria. There was no significant difference in mortality, length of stay, or escalation of therapy between dosing strategies.

Silver decorated 2D nanosheets of GO and MoS2serve as nanocatalyst for water treatment and antimicrobial applications as ascertained with molecular docking evaluation

In this work, synthesis of graphene oxide (GO) and reduced graphene oxide (rGO) was realized through a modified Hummers route. Different concentrations (5 and 10 wt%) of Ag were doped in MoS₂and rGO using a hydrothermal technique. Synthesized Ag-MoS₂and Ag-rGO were evaluated through XRD that confirmed the hexagonal structure of MoS₂along with the transformation of GO to Ag-rGO as indicated by a shift in XRD peaks while Mo-O bonding and S=O functional groups were confirmed with FTIR. Morphological information of GO and formation of MoS₂nanopetals as well as interlayer spacing were verified through FESEM and HRTEM respectively. Raman analysis was employed to probe any evidence regarding defect densities of GO. Optical properties of GO, MoS₂, Ag-rGO, and Ag-MoS₂were visualized through UV-vis and PL spectroscopy. Prepared products were employed as nanocatalysts to purify industrial wastewater. Experimental results revealed that Ag-rGO and Ag-MoS₂showed 99% and 80% response in photocatalytic activity. Besides, the nanocatalyst (Ag-MoS₂and Ag-rGO) exhibited 6.05 mm inhibition zones againstS. aureusgram positive (G+) and 3.05 mm forE. coligram negative (G-) in antibacterial activity. To rationalize biocidal mechanism of Ag-doped MoS₂NPs and Ag-rGO,in silicomolecular docking study was employed for two enzymes i.e.β-lactamase and D-alanine-D-alanine ligase B (ddlB) from cell wall biosynthetic pathway and enoyl-[acylcarrier-protein] reductase (FabI) from fatty acid biosynthetic pathway belonging toS. aureus. The present study provides evidence for the development of cost-effective, environment friendly and viable candidate for photocatalytic and antimicrobial applications.

Current evidence for therapy of ceftriaxone-resistant Gram-negative bacteremia

PURPOSE OF REVIEW

This article aims to give a state-of-the-art assessment of treatment options for bloodstream infection because of ceftriaxone-resistant Gram-negative bacilli, especially those caused by extended-spectrum beta-lactamase (ESBL) or AmpC-producing Enterobacteriaceae. In particular, this review assesses whether current data support 'carbapenem-sparing options' for treatment of these serious infections.

RECENT FINDINGS

The MERINO trial refuted earlier observational studies some of which showed equivalence in outcomes between beta-lactam/beta-lactamase inhibitor combinations and carbapenems for treatment of bloodstream infection because of ceftriaxone-resistant Escherichia coli or Klebsiella spp. Although numerous factors influence mortality following bloodstream infection, the variability in piperacillin/tazobactam MICs observed in the MERINO trial make this a less secure option than meropenem. However, the search for carbapenem-sparing options continues with four randomized controlled trials (RCTs) in progress and a number of other options in clinical development.

SUMMARY

Hard outcomes from RCTs are still needed before intravenous carbapenems can be displaced as the treatment of choice for ceftriaxone-resistant Gram-negative bacilli.

PRO: Carbapenems should be used for ALL infections caused by ceftriaxone-resistant Enterobacterales

Ceftriaxone resistance in the Enterobacterales is typically the result of production of ESBLs or AmpC β-lactamases. The genes encoding these enzymes are often co-located with other antibiotic resistance genes leading to resistance to aminoglycosides, quinolones and trimethoprim/sulfamethoxazole. Carbapenems are stable to ESBLs and AmpC giving them reliable in vitro activity against producers of these β-lactamases. In contrast, piperacillin/tazobactam and amoxicillin/clavulanate are compromised by co-production of OXA-1, which is not inhibited by tazobactam or clavulanate. These in vitro findings provide an explanation for the MERINO trial outcomes, where 3.7% (7/191) randomized to meropenem died compared with 12.3% (23/187) randomized to piperacillin/tazobactam as definitive treatment of bloodstream infection due to ceftriaxone-resistant organisms. No randomized trials have yet put cefepime and carbapenems head to head, but some observational studies have shown worse outcomes with cefepime. We argue that carbapenems are the antibiotics of choice for ceftriaxone-resistant Enterobacterales.

Photocatalytic, Bactericidal and Molecular Docking Analysis of Annealed Tin Oxide Nanostructures

Nanosized tin oxide was fabricated with a simple and cost-effective precipitation technique and was analyzed by performing x-ray powder diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, high-resolution transmission electron (HR-TEM) microscopy, energy-dispersive x-ray (EDX) and UV-Vis spectroscopy. The XRD results revealed that tin oxide particles possessed typical orthorhombic structure and exhibited improved crystallinity with annealing. Calcination at 250 °C produced predominantly orthorhombic SnO which transformed to SnO₂ at higher temperatures of 500 and 750 °C. HRTEM and FESEM images showed existence of agglomeration within the particles of tin oxide. The absorption was found to increase up to a certain annealing temperature followed by a decrease, which was recorded via UV-Vis spectroscopy. The effect of annealing temperature on dye decomposition behavior of synthesized photocatalysts was studied. It was noted that annealing temperature affects the size of synthesized particles, band gap width and photoactivity of tin oxide. The sample prepared at 500 °C followed first-order kinetics and exhibited maximum photocatalytic reactivity toward methylene blue. The experimental results obtained from the present study indicate that SnO₂ is a promising and beneficial catalyst to remove contaminants from wastewater and environment. The antimicrobial evaluation of SnO annealed at 500 °C against selected targets such as E. coli and S. aureus depicted significant inhibition zones in comparison with 250 and 750 °C samples. Furthermore, molecular docking predictions of SnO₂ nanoparticles (NPs) were performed against active pocket of β-lactamase and DNA gyrase enzyme belonging to cell wall and nucleic acid biosynthetic pathway, respectively. The fabricated NPs showed good binding score against β-lactamase of both E. coli (- 5.71 kcal/mol) and S. aureus (- 11.83 kcal/mol) alongside DNA gyrase (- 9.57 kcal/mol; E. coli and - 8.61 kcal/mol; S. aureus). These in silico predictions suggested SnO₂ NPs as potential inhibitors for selected protein targets and will facilitate to have a clear understanding of their mechanism of action that may contribute toward new antibiotics discovery.

Clinical Relevance of Antibiotic Susceptibility Profiles for Screening Gram-negative Microorganisms Resistant to Beta-Lactam Antibiotics

The increasing resistance to antibiotics is compromising the empirical treatment of infections caused by resistant bacteria. Rapid, efficient, and clinically applicable phenotypic methods are needed for their detection. This study examines the phenotypic behavior of β-lactam-resistant Gram-negative bacteria grown on ChromID ESBL medium with ertapenem, cefoxitin, and cefepime disks, reports on the coloration of colonies, and establishes a halo diameter breakpoint for the detection of carbapenemase-producing bacteria. We studied 186 β-lactam-resistant Gram-negative microorganisms (77 with extended spectrum beta lactamase (ESBL), 97 with carbapenemases, and 12 with AmpC β-lactamases (AmpC)). Susceptibility profiles of Gram-negative bacteria that produced ESBL, AmpC, and carbapenemases were similar to the expected profiles, with some differences in the response to cefepime of ESBL-producing microorganisms. Coloration values did not differ from those described by the manufacturer of ChromID ESBL medium. In the screening of carbapenemase production, inhibition halo diameter breakpoints for antibiotic resistance were 18 mm for Enterobacterales and ertapenem, 18 mm for Pseudomonas and cefepime, and 16 mm for Acinetobacter baumannii and cefepime. This innovative phenotypic approach is highly relevant to clinical laboratories, combining susceptibility profiles with detection by coloration of high-priority resistant microorganisms such as carbapenemase-producing A. baumannii, carbapenemase-producing Pseudomonas spp., and ESBL and/or carbapenemase-producing Enterobacterales.

Discovery of a Novel Natural Allosteric Inhibitor That Targets NDM-1 Against Escherichia coli

At present, the resistance of New Delhi metallo-β-lactamase-1 (NDM-1) to carbapenems and cephalosporins, one of the mechanisms of bacterial resistance against β-lactam antibiotics, poses a threat to human health. In this work, based on the virtual ligand screen method, we found that carnosic acid¹ (CA), a natural compound, exhibited a significant inhibitory effect against NDM-1 (IC₅₀ = 27.07 μM). Although carnosic acid did not display direct antibacterial activity, the combination of carnosic acid and meropenem still showed bactericidal activity after the loss of bactericidal effect of meropenem. The experimental results showed that carnosic acid can enhance the antibacterial activity of meropenem against Escherichia coli ZC-YN3. To explore the inhibitory mechanism of carnosic acid against NDM-1, we performed the molecular dynamics simulation and binding energy calculation for the NDM-1-CA complex system. Notably, the 3D structure of the complex obtained from molecular modeling indicates that the binding region of carnosic acid with NDM-1 was not situated in the active region of protein. Due to binding to the allosteric pocket of carnosic acid, the active region conformation of NDM-1 was observed to have been altered. The distance from the active center of the NDM-1-CA complex was larger than that of the free protein, leading to loss of activity. Then, the mutation experiments showed that carnosic acid had lower inhibitory activity against mutated protein than wild-type proteins. Fluorescence experiments verified the results reported above. Thus, our data indicate that carnosic acid is a potential NDM-1 inhibitor and is a promising drug for the treatment of NDM-1 producing pathogens.

The Continuing Plague of Extended-Spectrum β-Lactamase Producing Enterbacterales Infections: An Update

Antimicrobial resistance is a common iatrogenic complication of modern life and medical care. One of the most demonstrative examples is the exponential increase in the incidence of extended-spectrum β-lactamases (ESBLs) production among Enterobacteriaceae, that is, the most common human pathogens outside of the hospital setting. Infections resulting from ESBL-producing bacteria are associated with devastating outcomes, now affecting even previously healthy individuals. This poses an enormous burden and threat to public health. This article aims to narrate the evolving epidemiology of ESBL infections and highlights current challenges in terms of management and prevention of these common infections.

Does the presence of multiple β-lactamases in Gram-negative bacilli impact the results of antimicrobial susceptibility tests and extended-spectrum β-lactamase and carbapenemase confirmation methods?

OBJECTIVES

Many multidrug-resistant Gram-negative bacilli (MDR-GNB) harbour multiple β-lactamases. The aim of this study was to assess the impact of multiple β-lactamase carriage on the accuracy of susceptibility tests and extended-spectrum β-lactamase (ESBL) and carbapenemase confirmation methods.

METHODS

A total of 50 MDR-GNB, of which 29 carried multiple β-lactamases, underwent broth microdilution (BMD) and disk diffusion (DD) testing as well as confirmation tests for ESBLs and carbapenemases. Whole-genome sequencing (WGS) was used for β-lactamase gene identification.

RESULTS

Categorical agreement of BMD and DD testing results ranged from 86.5 to 97.7% for 10 β-lactam agents. BMD and DD algorithms for ESBL detection were highly variable; 6 of 8 positive strains carried an ESBL plus a carbapenemase or an AmpC enzyme, which may confound antimicrobial selection. The sensitivity and specificity of the modified carbapenem inactivation method (mCIM) were both 100%, whilst mCIM and EDTA-modified carbapenem inactivation method (eCIM) when used together to differentiate serine from metallo-β-lactamase carriage were both 96%. Xpert® Carba-R results (in vitro diagnostic test) were consistent with WGS results. Predicting phenotypic carbapenem resistance from WGS data overall showed 100% specificity but only 66.7% sensitivity for Enterobacterales isolates that were non-susceptible to imipenem and meropenem.

CONCLUSIONS

Multiple β-lactamases in MDR-GNB does not impact DD results, the utility of mCIM/eCIM tests, or Xpert Carba-R results. However, ESBL algorithms produced inconsistent results and predicting carbapenem resistance from WGS data was problematic in such strains.

Review of phenotypic assays for detection of extended-spectrum β-lactamases and carbapenemases: a microbiology laboratory bench guide

Background

Infections caused by gram-negative antibiotic-resistant bacteria continue to increase. Despite recommendations by the Clinical Laboratory Standards Institute (CLSI) and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) with regards to detection of antibiotic degrading enzymes secreted by these bacteria, the true prevalence of extended-spectrum β-lactamase (ESBL) and carbapenemase producers remains a difficult task to resolve. Describing of previously designed phenotypic detection assays for ESBLs and carbapenemases in a single document avails a summary that allows for multiple testing which increases the sensitivity and specificity of detection.

Methods and aims

This review, therefore, defined and classified ESBLs and carbapenemases, and also briefly described how the several previously designed phenotypic detection assays for the same should be performed.

Conclusion

Extended-spectrum β-lactamase and carbapenemase detection assays, once performed correctly, can precisely discriminate between bacteria producing these enzymes and those with other mechanisms of resistance to β-lactam antibiotics.

Successful de-escalation antibiotic therapy using cephamycins for sepsis caused by extended-spectrum beta-lactamase-producing Enterobacteriaceae bacteremia: A sequential 25-case series

Carbapenems are frequently used to treat infections caused by extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E), but carbapenem-resistant Enterobacteriaceae bacteria are a clinical concern. Although cephamycins (cefmetazole; CMZ) have been shown to be effective against mild cases of ESBL-E infection, data on their use for severe ESBL-E infections with sepsis or septic shock remain scarce. Herein, we discuss a de-escalation therapy to CMZ that could be used after empiric antibiotic therapy in ICU patients with sepsis or septic shock caused by ESBL-E bacteremia. A sequence of 25 cases diagnosed with sepsis or septic shock caused by ESBL-E bacteria was evaluated. The attending infectious disease specialist physicians selected the antibiotics and decided the de-escalation timing. The median SOFA (Sequential Organ Failure Assessment) and APACHE II (Acute Physiology and Chronic Health Evaluation II) severity scores were 8 and 30; the rate of septic shock was 60%. Infections originated most frequently with urinary tract infection (UTI) (56%) and Escherichia coli (85%). Eleven patients were de-escalated to CMZ after vital signs were stable, and all survived. No patients died of UTI regardless of with or without de-escalation. The median timing of de-escalation antibiotic therapy after admission was 4 days (range, 3–6 days). At the time of de-escalation, the median SOFA score fell from 8 to 5, the median APACHE II score from 28 to 22, and the rate of septic shock from 55% to 0%. We conclude that for sepsis in UTI caused by ESBL-E bacteremia, de-escalation therapy from broad-spectrum antibiotics to CMZ is a potential treatment option when vital signs are stable.

Incidence and antimicrobial profile of extended-spectrum β-lactamase producing gram-negative bacterial isolates: An in-vitro and statistical analysis

OBJECTIVES

There is an extensive incidence of extended-spectrum beta-lactamases (ESBLs), principally in the hospital environment across the world. The present study was designed to discover the frequency of ESBL-production among the clinical isolates of Escherichia coli, Klebsiella pneumonia, and Pseudomonas aeruginosa. The study also focused on determining their liability to the selected antimicrobials.

METHODS

Two hundred ten (210) clinical specimens were tested for the occurrence of ESBL using the double-disc synergy test. The molecular, physicochemical, absorption, distribution, metabolism, excretion, and toxicity were checked through an online server.

RESULTS

Among the screened clinical isolates, E. coli (n=44), K. pneumonia (n=34) and P. aeruginosa (n=14) were ESBL markers. The ESBL producing isolates exhibited co-resistance to diverse categories of antibiotics. It was observed that all the ESBL-producing isolates were sensitive towards imipenem and faropenem with minimal proportion of resistance.

CONCLUSION

The imipenem and faropenem can be recommended as the drugs of selection due to a lesser amount of resistance as compared to other antibiotics in this study.

The cost-effectiveness of empirical antibiotic treatments for high-risk febrile neutropenic patients: A decision analytic model

PURPOSE

Febrile neutropenia has a significant clinical and economic impact on cancer patients. This study evaluates the cost-effectiveness of different current empiric antibiotic treatments.

METHODS

A decision analytic model was constructed to compare the use of cefepime, meropenem, imipenem/cilastatin, and piperacillin/tazobactam for treatment of high-risk patients. The analysis was performed from the perspective of U.S.-based hospitals. The time horizon was defined to be a single febrile neutropenia episode. Cost-effectiveness was determined by calculating costs and deaths averted. Cost-effectiveness acceptability curves for various willingness-to-pay thresholds (WTP), were used to address the uncertainty in cost-effectiveness.

RESULTS

The base-case analysis results showed that treatments were equally effective but differed mainly in their cost. In increasing order: treatment with imipenem/cilastatin cost $52,647, cefepime $57,270, piperacillin/tazobactam $57,277, and meropenem $63,778. In the probabilistic analysis, mean costs were $52,554 (CI: $52,242-$52,866) for imipenem/cilastatin, $57,272 (CI: $56,951-$57,593) for cefepime, $57,294 (CI: $56,978-$57,611) for piperacillin/tazobactam, and $63,690 (CI: $63,370-$64,009) for meropenem. Furthermore, with a WTP set at $0 to $50,000, imipenem/cilastatin was cost-effective in 66.2% to 66.3% of simulations compared to all other high-risk options.

DISCUSSION

Imipenem/cilastatin is a cost-effective strategy and results in considerable health care cost-savings at various WTP thresholds. Cost-effectiveness analyses can be used to differentiate the treatments of febrile neutropenia in high-risk patients.

Optimizing therapy of bloodstream infection due to extended-spectrum β-lactamase-producing Enterobacteriaceae

PURPOSE OF REVIEW

Infections due to extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) are increasing worldwide. Carbapenems are usually regarded as the antibiotics of choice for the treatment of serious ESBL infections. However, because of the alarming emergence or carbapenem resistance, interest in effective alternatives has emerged. The present review summarizes the findings published on the antibiotics currently available for treatment of patients with an ESBL-E bloodstream infection (BSI).

RECENT FINDINGS

Meropenem and imipenem are the drugs recommended for treatment of ESBL BSIs in critically ill patients, and in infections with high bacterial loads or elevated β-lactam minimum inhibitory concentrations. Ertapenem should be reserved for patients with less severe presentations, and should be used at high doses. In milder presentations or BSIs from low-risk sources, other carbapenem-sparing alternatives could be considered: cephamycins, fluoroquinolones, and particularly a β-lactam/β-lactam inhibitor combination (particularly piperacillin/tazobactam). Optimized dosing of piperacillin/tazobactam is recommended (high doses and extended infusion). There are few data on the use of the promising newly available drugs (e.g. ceftolozane/tazobactam, ceftazidime/avibactam, cefiderocol, and plazomicin), and it seems reasonable to reserve them as last-resort drugs.

SUMMARY

Carbapenems should be used in patients with serious infections; alternatives could be used individually, particularly for definitive treatment of patients with milder presentations.

Risk Factors for Positive Follow-Up Blood Cultures in Gram-Negative Bacilli Bacteremia: Implications for Selecting Who Needs Follow-Up Blood Cultures

Background

The value of follow-up blood cultures (FUBCs) to document clearance of bacteremia due to Gram-negative bacilli (GNB) has not been well established. Although previous studies suggested that the yield of FUBCs for GNB bacteremia is low, it remains to be elucidated for whom FUBC may be beneficial and for whom it is unnecessary.

Methods

A retrospective cohort study was performed at 4 acute care hospitals to identify risk factors for positive FUBCs with GNB bacteremia and to better guide clinicians’ decisions as to which patients may or may not benefit from FUBCs. Participants included adult patients with GNB bacteremia who had FUBCs and were admitted between January 2017 and December 2018. The primary outcomes were the factors associated with positive FUBCs and the yield of FUBCs with and without the factors.

Results

Of 306 patients with GNB bacteremia who had FUBCs, 9.2% (95% confidence interval, 6.2%–13.0%) had the same GNB in FUBCs. In the multivariate logistic regression analysis, end-stage renal disease on hemodialysis, intravascular device, and bacteremia due to extended-spectrum β-lactamase or carbapenemase-producing organism were identified as independent predictors of positive FUBCs with GNB bacteremia. Approximately 7 FUBCs and 30 FUBCs were needed for patients with ≥1 or no risk factors, respectively, to yield 1 positive result.

SummaryThis multi-site retrospective cohort study found that among patients with gram-negative bacilli (GNB) bacteremia, having ESRD on hemodialysis, intravascular devices, or bacteremia due to multi-drug resistant GNB were each independently associated with having a positive follow-up blood culture.

Conclusions

Follow-up blood culture may not be necessary for all patients with GNB bacteremia and has the highest yield in patients with 1 or more risk factors.

Old In Vitro Antimicrobial Breakpoints Are Misleading Stewardship Efforts, Delaying Adoption of Innovative Therapies, and Harming Patients

The current antimicrobial market and old (pre-2000) in vitro antimicrobial susceptibility test interpretative criteria (STIC) are not working properly. Malfunctioning susceptibility breakpoints and antimicrobial markets have serious implications for both patients (ie, from a safety and efficacy perspective) and antibiotic-focused pharmaceutical and biotechnology company economic viability. Poorly functioning STIC fail both patients and clinicians since they do not discriminate between likely effective and ineffective antimicrobial regimens. Poor economic viability fails patients and clinicians as it decreases the industry’s ability to develop antimicrobial agents that clinicians and patients urgently require now and in the future. Herein, we review how STIC for older antimicrobial agents were determined and how their correction can impact the perceived utility of old relative to new antimicrobial agents. Moreover, we describe the data and analysis needs to systematically reevaluate older STIC values. We call for professional infectious diseases societies, government agencies, and other consensus bodies interested in the appropriate use of antimicrobial agents to join an effort to systematically evaluate and, where warranted, correct STIC for all relevant antimicrobial agents. This effort will amplify the effects of other measures designed to increase appropriate antimicrobial use (ie, good antimicrobial stewardship), development, and regulation.

In vitro activity of ceftolozane/tazobactam against phenotypically defined extended-spectrum β-lactamase (ESBL)-positive isolates of Escherichia coli and Klebsiella pneumoniae isolated from hospitalized patients (SMART 2016)

The Clinical and Laboratory Standards Institute (CLSI)-defined broth microdilution testing method (M07, 11th edition, 2018) was used to determine MICs for ceftolozane/tazobactam and eight comparator agents against 21,952 isolates of Enterobacteriaceae submitted by 161 clinical laboratories in 51 countries in 2016 as a part of the SMART global surveillance program. MICs were interpreted using CLSI breakpoints (M100 29th edition, 2019). 89.7% of isolates of Enterobacteriaceae were susceptible to ceftolozane/tazobactam, compared to 70.0%, 76.3%, 77.7%, 84.7%, 93.6%, and 96.4%, respectively, for ceftriaxone, ceftazidime, cefepime, piperacillin-tazobactam, ertapenem, and meropenem. 82.4% of isolates of ESBL-positive, carbapenemase-negative Enterobacteriaceae were susceptible to ceftolozane/tazobactam, compared to 1.5%, 7.8%, 20.3%, 71.1%, 94.7%, and 98.7%, respectively, for ceftriaxone, cefepime, ceftazidime, piperacillin-tazobactam, ertapenem, and meropenem. In vitro susceptibility to ceftolozane/tazobactam was >60% higher than susceptibility to other advanced-generation cephalosporins among all Enterobacteriaceae and >10% higher than susceptibility to piperacillin-tazobactam among ESBL-positive Enterobacteriaceae collected globally in 2016.

Aztreonam and Vancomycin for Initial Treatment of Febrile Neutropenia in Penicillin-Allergic Patients During Hematopoietic Stem Cell Transplantation

Most patients who undergo hematopoietic stem cell transplantation develop neutropenic fever and are at high risk for developing potentially life-threatening infections. β-lactam antibiotics remain the cornerstone for initial empiric treatment of neutropenic fever. In cancer patients with allergy or intolerance to β-lactams, guidelines recommend using aztreonam with vancomycin (AV) for neutropenic fever treatment. To date, the efficacy of AV for the treatment of neutropenic fever during stem cell transplantation is unknown. A retrospective study was conducted to identify hematopoietic stem cell transplantation recipients who were initially treated with concomitant AV for neutropenic fever between 2007 and 2013. Febrile neutropenia was classified as neutropenia with unexplained fever, neutropenic fever with a local source of infection, or neutropenic fever with a microbiologically documented infection. Seventy-six patients were identified who received AV as initial treatment for neutropenic fever over the study period. Responses to AV for neutropenia with unexplained fever (n = 41), febrile neutropenia with local site of infection (n = 11 [pneumonia = 9, other = 2]), and neutropenic fever with microbiologically documented infection (n = 34) were 75%, 55% (45% pneumonia), and 46% respectively. Infection-related mortality was 5%. Aztreonam with vancomycin was effective in treating neutropenia with unexplained fever. For patients with neutropenic fever and local source or microbiologically documented infection, alternative antibiotic treatments should be considered.

Widespread antimicrobial resistance among bacterial infections in a Rwandan referral hospital

BACKGROUND

Resistance among bacterial infections is increasingly well-documented in high-income countries; however, relatively little is known about bacterial antimicrobial resistance in low-income countries, where the burden of infections is high.

METHODS

We prospectively screened all adult inpatients at a referral hospital in Rwanda for suspected infection for seven months. Blood, urine, wound and sputum samples were cultured and tested for antibiotic susceptibility. We examined factors associated with resistance and compared hospital outcomes for participants with and without resistant isolates.

RESULTS

We screened 19,178 patient-days, and enrolled 647 unique participants with suspected infection. We obtained 942 culture specimens, of which 357 were culture-positive specimens. Of these positive specimens, 155 (43.4%) were wound, 83 (23.2%) urine, 64 (17.9%) blood, and 55 (15.4%) sputum. Gram-negative bacteria comprised 323 (88.7%) of all isolates. Of 241 Gram-negative isolates tested for ceftriaxone, 183 (75.9%) were resistant. Of 92 Gram-negative isolates tested for the extended spectrum beta-lactamase (ESBL) positive phenotype, 66 (71.7%) were ESBL positive phenotype. Transfer from another facility, recent surgery or antibiotic exposure, and hospital-acquired infection were each associated with resistance. Mortality was 19.6% for all enrolled participants.

CONCLUSIONS

This is the first published prospective hospital-wide antibiogram of multiple specimen types from East Africa with ESBL testing. Our study suggests that low-resource settings with limited and inconsistent access to the full range of antibiotic classes may bear the highest burden of resistant infections. Hospital-acquired infections and recent antibiotic exposure are associated with a high proportion of resistant infections. Efforts to slow the development of resistance and supply effective antibiotics are urgently needed.

Prevalence of blaTEM, blaSHV, and blaCTX-M Genes among ESBL-Producing Klebsiella pneumoniae and Escherichia coli Isolated from Thalassemia Patients in Erbil, Iraq

Background

Due to the recent appearance of organisms that are resistant to several drugs (multidrug-resistant) like Enterobacteriaceae that produce extended-spectrum β-lactamase (ESBL, concerns have remarkably increased regarding the suitable treatment of infections. The present study was an investigation into ESBL molecular characteristics among clinical isolates of Klebsiella pneumoniae and Escherichia coli resulting in urinary tract infections (UTIs) and their pattern of antimicrobial resistance in order to come up with helpful information on the epidemiology of these infections and risk factors accompanied with them.

Methods

In order to conduct the study, 20 K. pneumoniae and 48 E. coli were isolated and retrieved from thalassemia center in Erbil, Iraq during July 2016 and September 2016. The collected strains were analyzed and the profile of their antimicrobial susceptibility was specified. In order to spot β-lactamase genes (i.e. blaTEM, blaSHV, and blaCTX-M), polymerase chain reaction was conducted.

Results

The findings obtained from multiplex PCR assay showed that out of the collected strains of ESBL-producing E. coli, had 81% blaTEM, 16.2% blaSHV, and 32.4% blaCTX-M genes. Similarly, 64.7% blaTEM, 35.2% blaSHV, and 41.1% blaCTX-M genes existed in the isolates of K. pneumoniae. It was found that antibiotic resistance pattern of E. coli and K. pneumoniae isolates to 20 antibiotics varied widely. It was also concluded that the majority of the K. pneumoniae and E. coli isolates were multi-drug resistant (MDR). Moreover, 75% and 87.5% of respectively K. pneumoniae and E. coli isolates showed the MDR phenotypes.

Conclusion

TEM prevalence was high among other types of ESBLs. Over all, the most active antimicrobial agents in vitro remained to be the carbapenems.

Role of place of acquisition and inappropriate empirical antibiotic therapy on the outcome of extended-spectrum β-lactamase-producing Enterobacteriaceae infections

The impact of inappropriate empirical antibiotic therapy (IEAT) on the outcome of severe infections due to extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-Ent) remains unclear. Current evidence is limited by study design and lack of confounder control. The main objective of this study was to define the outcome of severe infections due to ESBL-Ent according to clinical parameters and place of infection acquisition. Adult hospitalised patients with ESBL-Ent infections were included in a 3-year multicentre prospective study. Primary outcomes were IEAT rates and crude mortality of severe infections, adjusted by place of acquisition [community-acquired infection (CAI), healthcare-associated infection (HCAI) and hospital-acquired infection (HAI)]. Among 729 patients, 519 (71.2%) were diagnosed with HAI, 176 (24.1%) with HCAI and 34 (4.7%) with CAI. Moreover, 32.9% of patients received IEAT; higher rates of IEAT were observed in pneumonia (23%) and deep surgical site infections (19%). HCAIs were more frequently associated with IEAT than HAIs (48.3% vs. 27.9%; OR = 1.7, 95% CI 1.2-2.4). The overall mortality rate for severe infections (n = 264) was 12.1% and was significantly higher in HCAIs (20%) than HAIs (10%) (RR = 2.3, 95% CI 1.01-5.3). IEAT significantly increased the risk of mortality in bloodstream infections (RR = 8.3, 95% CI 2-46.3). Rates of IEAT and overall mortality of ESBL-Ent severe infections were higher in HCAIs than HAIs. Prompt diagnosis of patients with severe HCAIs due to ESBL-Ent is essential since these infections receive high rates of IEAT and significantly higher mortality than HAIs [ClinicalTrials.gov Identifier: NCT00404625].

Current options for the treatment of infections due to extended-spectrum beta-lactamase-producing Enterobacteriaceae in different groups of patients

BACKGROUND

Extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) are a frequent cause of invasive infections worldwide. Carbapenems are nowadays the most used drugs to treat these infections. However, due to the increasing rates of resistance to these antimicrobials, carbapenem-sparing alternatives are being investigated.

OBJECTIVES AND SOURCES

The aim of this narrative literature review is to summarize the published information on the currently available antibiotics for the treatment of ESBL-E infections, providing specific information on three subgroups of patients: Group 1, patients with severe infections or infections from high-risk sources or in severely immunocompromised patients; Group 2, patients with non-severe infections from intermediate-risk source; and Group 3, patients with non-severe urinary tract infection.

CONTENT AND IMPLICATIONS

For patients in Group 1, the current data would support the use of carbapenems. For milder infections, however, particularly urinary tract infections, other non-carbapenem antibiotics can be considered in selected cases, including beta-lactam/beta-lactam inhibitor combinations, cephamycins, temocillin and aminoglycosides. While specific studies should be performed in these situations, individualized decisions may be taken in order to avoid overuse of carbapenems.

Treatment of infections caused by multidrug-resistant Gram-negative bacteria: report of the British Society for Antimicrobial Chemotherapy/Healthcare Infection Society/British Infection Association Joint Working Party

The Working Party makes more than 100 tabulated recommendations in antimicrobial prescribing for the treatment of infections caused by multidrug-resistant (MDR) Gram-negative bacteria (GNB) and suggest further research, and algorithms for hospital and community antimicrobial usage in urinary infection. The international definition of MDR is complex, unsatisfactory and hinders the setting and monitoring of improvement programmes. We give a new definition of multiresistance. The background information on the mechanisms, global spread and UK prevalence of antibiotic prescribing and resistance has been systematically reviewed. The treatment options available in hospitals using intravenous antibiotics and in primary care using oral agents have been reviewed, ending with a consideration of antibiotic stewardship and recommendations. The guidance has been derived from current peer-reviewed publications and expert opinion with open consultation. Methods for systematic review were NICE compliant and in accordance with the SIGN 50 Handbook; critical appraisal was applied using AGREE II. Published guidelines were used as part of the evidence base and to support expert consensus. The guidance includes recommendations for stakeholders (including prescribers) and antibiotic-specific recommendations. The clinical efficacy of different agents is critically reviewed. We found there are very few good-quality comparative randomized clinical trials to support treatment regimens, particularly for licensed older agents. Susceptibility testing of MDR GNB causing infection to guide treatment needs critical enhancements. Meropenem- or imipenem-resistant Enterobacteriaceae should have their carbapenem MICs tested urgently, and any carbapenemase class should be identified: mandatory reporting of these isolates from all anatomical sites and specimens would improve risk assessments. Broth microdilution methods should be adopted for colistin susceptibility testing. Antimicrobial stewardship programmes should be instituted in all care settings, based on resistance rates and audit of compliance with guidelines, but should be augmented by improved surveillance of outcome in Gram-negative bacteraemia, and feedback to prescribers. Local and national surveillance of antibiotic use, resistance and outcomes should be supported and antibiotic prescribing guidelines should be informed by these data. The diagnosis and treatment of both presumptive and confirmed cases of infection by GNB should be improved. This guidance, with infection control to arrest increases in MDR, should be used to improve the outcome of infections with such strains. Anticipated users include medical, scientific, nursing, antimicrobial pharmacy and paramedical staff where they can be adapted for local use.

Extended-spectrum beta-lactamase production and multi-drug resistance among Enterobacteriaceae isolated in Addis Ababa, Ethiopia

Background

The global emergence and spread of extended-spectrum beta-lactamases (ESBLs) producing Enterobacteriaceae have been threatening the ability to treat an infection. Hence, this study aimed to determine the prevalence of ESBL-producing and multi-drug resistance (MDR) Enterobacteriaceae (ESBLs-E) from different clinical specimens in Addis Ababa, Ethiopia.

Methods

A cross-sectional study was conducted from January 1 to May 30, 2017. A total of 426 Enterobacteriaceae isolates were identified from clinical specimens. The isolates were collected from four laboratories. Antimicrobial susceptibility testing was performed using the Kirby-Bauer disk diffusion method on Muller Hinton agar (MHA). All Enterobacteriaceae were screened for ESBLs production using cefotaxime and ceftazidime as per CLSI guideline. Each ESBL screening positive Enterobacteriaceae were confirmed by a combination disk test (CDT). Data were entered and analyzed by using SPSS version-20.

Result

The most frequent Enterobacteriaceae were E. coli 228 (53.5%) and K. pneumoniae 103 (24.1%). The magnitude of ESBLs-E was 57.7% (246/426). The highest frequencies of ESBLs-E were observed in blood specimesns (84.4%) and the highest ESBLs production was observed in K. pneumoniae (85.4%). The highest resistance level was seen to sulfamethoxazole-trimethoprim (77.0%), amoxicillin with clavulanic acid (71.6%), cefotaxime (62.2%), cefepime (60.3%) and ceftazidime (60.8%). The overall magnitude of multi-drug resistance (MDR) level was 68.3%. Of ESBLs-E, 96.3% of them were MDR (P < 0.001).

Conclusion

There was a high prevalence of ESBLs-E and MDR isolate in Addis Ababa. Most of ESBLs-E was isolated primarily in blood and urine. The highest ESBLs production was observed among K. pneumoniae. Hence, strong infection control strategies must be implemented in hospital settings of the country.

High Prevalence of Antimicrobial Resistance in Gram-Negative Bacteria Isolated from Clinical Settings in Egypt: Recalling for Judicious Use of Conventional Antimicrobials in Developing Nations

This study was designed to investigate, at the molecular level, the antimicrobial resistance mechanisms of different antimicrobial resistance genes, including, extended-spectrum β-lactamases, AmpC β-lactamases, class 1 and 2 integrons, and plasmid-mediated quinolone resistance genes of Gram-negative bacteria isolated from clinical settings in Egypt. A total of 126 nonduplicate Gram-negative isolates were recovered from different clinical samples taken from hospitalized patients in Egypt in 2014. Antimicrobial susceptibility testing showed that, 93.6% (118/126) of the isolates had a multidrug-resistant phenotype. Interestingly, we reported a high level of antimicrobial resistance nearly for all tested antibiotics; to our knowledge, this is the first report from Egypt indicating very high level of antibiotic resistance in Egypt. Polymerase chain reaction screening and DNA sequencing revealed that, 75.4% (95/126) of the isolates harbored at least one extended-spectrum β-lactamase-encoding gene, with bla_CTX-M being the most prevalent (65.9%), followed by bla_SHV (46.8%). The AmpC β-lactamase, bla_CMY, was detected in 7.1% (9/126) of bacterial isolates, with bla_CMY-42 being the most prevalent. Class 1 integrons were detected in 50.8% (64/126) of the isolates, and class 2 integrons were detected in 2.4% (3/126) of the isolates. The plasmid-mediated quinolone resistance gene, qnr, was detected in 58.7% (74/126) of the tested isolates, with qnrS being the most prevalent. Several antimicrobial resistance determinants were identified in Egypt for the first time, such as SHV-27, SHV-28, SHV-33, SHV-63, SHV-71, SHV-82, SHV-142, CMY-42, CMY-6, and the new CMY-72 like. This study highlights the importance of the conscious use of conventional antimicrobials to overcome the multidrug resistance problem.

Evaluation of a Novel Chromogenic Selective Medium for the Improved Detection of Campylobacter from Stool Samples

BD mCCDA Clear-HT (CCHT; Nippon Becton Dickinson Company, Ltd.) , a novel chromogenic selective medium was evaluated for its superior capacity to isolate Campylobacter jejuni/ coli. When CCHT was assessed using 142 microbes including 42 Campylobacter jejuni/ coli strains, all Campylobacter strains were found to form purple-colored colonies on CCHT whereas all the other microbes failed to grow. CCTH was then compared with commercially available selective media using 100 stool samples including 40 Campylobacter positive samples. CCHT detected Campylobacter jejuni/ coli from 39 of 40 (97.5%) stool samples whereas it allowed competitive bacteria to grow as false positive colonies from 1 (1.0%) of 100 stool samples. The values of relative sensitivity (%) and specificity (%) for CCHT were 97.5 and 98.3 in this study. Our results demonstrated that CCHT had the highest detection ratio for Campylobacter jejuni/ coli and the highest inhibition ratio against competitive bacteria among all selective media compared.

Molecular Detection of New SHV β-lactamase Variants in Clinical Escherichia coli and Klebsiella pneumoniae Isolates from Egypt

The emergence of multidrug-resistant (MDR) pathogens was reported worldwide. Herein, SHV extended-spectrum β-lactamase (SHV-ESBL) variants detection was investigated in MDR E. coli and K. pneumoniae isolates recovered from human subjects (n = 144), one day-old chicks (n = 36) and broiler clinical samples (n = 90). All examined samples were positive for E. coli (n = 246/270; 91.11%) and Klebsiella pneumoniae (n = 24/270; 8.89%). Antimicrobial susceptibility testing was performed on E. coli and K. pneumoniae. SHV-ESBL producing isolates were defined followed by SHV-ESBL amino acids sequence and proteins structure-function analyses. Phylogenetic analysis of 11 MDR isolates resistant to at least 6 β-lactams was designed to determine their genetic relationship with those previously identified in Egypt. SHV-ESBL variants were detected in 28% and 16% of E. coli and K. pneumoniae isolates, respectively. Among the 11 SHV-ESBL producing isolates, one isolate displayed 100% blaSHV-12 similarity with three point mutations, while the other 10 isolates displayed amino acid substitutions at previously non-reported sites. Amino acid sequence analyses of these 10 isolates displayed 96-100% identity to blaSHV-10 (2 isolates with 3-6 point mutations), blaSHV-18 (one isolate with 4 point mutations), blaSHV-58 (4 isolates with 4-5 point mutations), and blaSHV-91 (3 isolates with 3-7 point mutations). These mutations altered SHV-enzyme pocket dimensions and its binding sites chargeability. The blaSHV phylogeny analysis revealed occurrence of variants in closely related lineages with blaSHV-5 and blaSHV-12 with possibility of blaSHV gene transfer between human and birds. The occurrence of these variants in Egypt could help in epidemiological studies and could explain the emergent resistance to β-lactams.

Clinical and Molecular Correlates of Escherichia coli Bloodstream Infection from Two Geographically Diverse Centers in Rochester, Minnesota, and Singapore

Escherichia coli bacteremia is caused mainly by sequence type complex 131 (STc131) and two clades within its fluoroquinolone-resistance-associated H30 subclone, H30R1 and H30Rx. We examined clinical and molecular correlates of E. coli bacteremia in two geographically distinct centers. We retrospectively studied 251 unique E. coli bloodstream isolates from 246 patients (48 from the Mayo Clinic, Rochester, MN [MN], and 198 from Tan Tock Seng Hospital, Singapore [SG]), from October 2013 through March 2014. Isolates underwent PCR for phylogroup, STc, bla_CTX-M type, and virulence gene profiles, and medical records were reviewed. Although STc131 accounted for 25 to 27% of all E. coli bacteremia isolates at each site, its extended-spectrum-β-lactamase (ESBL)-associated H30Rx clade was more prominent in SG than in MN (15% versus 4%; P = 0.04). In SG only, patients with STc131 (versus other E. coli STc isolates) were more likely to receive inactive initial antibiotics (odds ratio, 2.8; P = 0.005); this was true specifically for patients with H30Rx (odds ratio, 7.0; P = 0.005). H30Rx comprised 16% of community-onset bacteremia episodes in SG but none in MN. In SG, virulence scores were higher for H30Rx than for H30R1, non-H30 STc131, and non-STc131 isolates (P < 0.02 for all comparisons). At neither site did mortality differ by clonal status. The ESBL-associated H30Rx clade was more prevalent and more often of community onset in SG, where it predicted inactive empirical treatment. The clonal distribution varies geographically and has potentially important clinical implications. Rapid susceptibility testing and clonal diagnostics for H30/H30Rx might facilitate earlier prescribing of active therapy.

Characterization of Extended-Spectrum β-Lactamase-Producing Enterobacteriaceae From Retail Food in China

In this study, we characterized the β-lactamase genes and phenotypic resistance of cephalosporin-resistant Enterobacteriaceae isolated from retail foods in China. Of 1,024 Enterobacteriaceae isolates recovered from raw meat products, aquatic products, raw vegetables, retail-level ready-to-eat (RTE) foods, frozen foods, and mushrooms from 2011 to 2014, 164 (16.0%) showed cefotaxime (CTX) and/or ceftazidime (CAZ) cephalosporin resistance, and 96 (9.4%) showed the extended-spectrum β-lactamase (ESBL) phenotype. More than 30% isolates were resistant to all antimicrobial agents except carbapenems (MEM 3.1% and IPM 5.2%), cefoxitin (FOX 6.3%), and amoxicillin/clavulanic acid (AMC 26%), and 94.8% of the strains were resistant to up to seven antibiotics. Polymerase chain reaction analysis showed that blaTEM (81.9%) was the most common gene, followed by blaCTX-M (68.1%) and blaSHV (38.9%). Moreover, 16.8% (72/429) of food samples contained ESBL-positive Enterobacteriaceae, with the following patterns: 32.9% (23/70) in frozen foods, 27.2% (5/29) in mushrooms, 17.6% (24/131) in raw meats, 13.3% (4/30) in fresh vegetables, 11.1% (8/72) in RTE foods, and 9.3% (9/97) in aquatic products. In addition, 24 of 217 foods collected in South China (11.1%), 25 of 131 foods collected in North of the Yangtze River region (19.1%), and 23 of 81 foods collected in South of the Yangtze River region (28.4%) were positive for ESBL- Enterobacteriaceae. Conjugation experiments demonstrated that the 22 of 72 isolates were transconjugants that had received the β-lactamase gene and were resistant to β-lactam antibiotics as well as some non-β-lactam antibiotics. These findings demonstrated that retail foods may be reservoirs for the dissemination of β-lactam antibiotics and that resistance genes could be transmitted to humans through the food chain; and the predominant ESBL-producing Enterobacteriaceae in China was isolated from in frozen chicken-meat, followed by frozen pork, cold noodles in sauce, cucumber, raw chicken meat, frozen pasta, brine-soaked chicken and tomato.

Potential of high-dose cefepime/tazobactam against multiresistant Gram-negative pathogens

Background

Early β-lactamase inhibitors were combined with established penicillins, but different combinations may be more appropriate to counter current β-lactamase threats, with development facilitated by the US Generating Antibiotic Incentives Now (GAIN) Act. Cefepime/tazobactam is especially attractive, combining an AmpC-stable cephalosporin with a clinically established inhibitor, active against ESBLs and suitable for high-dose administration.

Methods

Organisms (n = 563) were clinical isolates submitted to the UK national reference laboratory. MICs were determined by CLSI agar dilution with tazobactam at 4 mg/L and, for a subset, at 8 mg/L.

Results

Cefepime/tazobactam 8 + 4 mg/L achieved coverage of 96%-100% of Enterobacteriaceae with penicillinases, AmpC, ESBL, K1 or OXA-48 β-lactamases. Even at 1 + 4 mg/L, the combination inhibited >94% of isolates with penicillinases, AmpC enzymes or ESBLs. Most Enterobacteriaceae with KPC and NDM carbapenemase were resistant at current cefepime breakpoints but 80% of those with VIM types were susceptible at 8 + 4 mg/L. Tazobactam did little to potentiate cefepime against non-fermenter groups, though gains were seen against AmpC-producing Acinetobacter spp. and Stenotrophomonas maltophilia. Increasing the tazobactam concentration to 8 mg/L gave further small increases in activity against Enterobacteriaceae groups.

Conclusions

High-dose cefepime/tazobactam, justifying an 8 + 4 or 8 + 8 mg/L breakpoint, can achieve a carbapenem-like spectrum, with some additional coverage of OXA-48 (and maybe VIM) Enterobacteriaceae. Clinical evaluation is warranted.

Can the Ceftriaxone Breakpoints Be Increased Without Compromising Patient Outcomes?

Background

In 2010, the Clinical Laboratory and Standards Institute recommended a 3-fold lowering of ceftriaxone breakpoints to 1 mcg/mL for Enterobacteriaceae. Supportive clinical data at the time were from fewer than 50 patients. We compared the clinical outcomes of adults with Enterobacteriaceae bloodstream infections treated with ceftriaxone compared with matched patients (with exact matching on ceftriaxone minimum inhibitory concentrations [MICs]) treated with extended-spectrum agents to determine if ceftriaxone breakpoints could be increased without negatively impacting patient outcomes.

Methods

A retrospective cohort study was conducted at 3 large academic medical centers and included patients with Enterobacteriaceae bacteremia with ceftriaxone MICs of 2 mcg/mL treated with ceftriaxone or extended-spectrum β-lactams (ie, cefepime, piperacillin/tazobactam, meropenem, or imipenem/cilastatin) between 2008 and 2014; 1:2 nearest neighbor propensity score matching was performed to estimate the odds of recurrent bacteremia and mortality within 30 days.

Results

Propensity score matching yielded 108 patients in the ceftriaxone group and 216 patients in the extended-spectrum β-lactam group, with both groups well-balanced on demographics, preexisting medical conditions, severity of illness, source of bacteremia, and source control interventions. No difference in recurrent bacteremia (odds ratio [OR], 1.16; 95% confidence interval [CI], 0.49–2.73) or mortality (OR, 1.27; 95% CI, 0.56–2.91) between the treatment groups was observed for patients with isolates with ceftriaxone MICs of 2 mcg/mL. Only 6 isolates (1.6%) with ceftriaxone MICs of 2 mcg/mL were extended-spectrum β-lactamase (ESBL)–producing.

Conclusions

Our findings suggest that patient outcomes are similar when receiving ceftriaxone vs extended-spectrum agents for the treatment of Enterobacteriaceae bloodstream infections with ceftriaxone MICs of 2 mcg/mL. This warrants consideration of adjusting the ceftriaxone susceptibility breakpoint from 1 to 2 mcg/mL, as a relatively small increase in the antibiotic breakpoint could have the potential to limit the use of large numbers of extended-spectrum antibiotic agents.