Oral antibiotics for the treatment of Gram-negative bloodstream infections: A retrospective comparison of three antibiotic classes

Clinical Outcomes of Patients with AmpC-Beta-Lactamase-Producing Enterobacterales Bacteremia Treated with Carbapenems versus Non-Carbapenem Regimens: A Single-Center Study

INTRODUCTION

Bloodstream infections caused by AmpC-producing Enterobacterales pose treatment challenges due to the risk of AmpC overproduction and treatment failure. Current guidelines recommend carbapenems or cefepime as optimal therapy. We aimed to evaluate empiric and definitive non-carbapenem regimens for these infections.

METHODS

In a retrospective study from June 2014 to March 2023, adult bacteremic patients with Enterobacter cloacae complex strains and Morganella morganii were evaluated. Demographic, clinical and lab data and outcomes were assessed.

RESULTS

The cohort comprised 120 bacteremic patients, 17 receiving empiric carbapenem and 103 non-carbapenem regimens. Both groups had similar Charlson and Norton scores and previous antimicrobial exposure. The most common sources of bacteremia were urinary, abdominal and central-line-associated sources. Empiric non-carbapenem regimens (primarily piperacillin-tazobactam and cephalosporins) were not associated with recurrent bacteremia or 30-day mortality. Definitive regimens included mainly carbapenems (n = 41) and ciprofloxacin (n = 46). Beta-lactams were administered to 25 patients. Recurrent bacteremia and 30-day mortality rates were similar among treatment groups. Ciprofloxacin showed comparable outcomes to carbapenems, however, severity of illness among these patients was lower.

CONCLUSIONS

Empiric and definitive non-carbapenem regimens for bacteremia with AmpC-producing organisms were not associated with treatment failure or increased 30-day mortality. Ciprofloxacin appears promising for selected, stable patients, potentially enabling early discharge.

Oral Antibiotics for Treatment of Gram-Negative Bacteremia in Solid Organ Transplant Recipients: A Propensity Score Weighted Retrospective Observational Study

BACKGROUND

We assessed the safety and efficacy of oral antibiotic step-down therapy for uncomplicated gram-negative blood stream infections in solid-organ transplant recipients.

METHODS

We identified all solid-organ transplant recipients within the Massachusetts General and Brigham and Women's Hospital systems from 2016 to 2021 with uncomplicated gram-negative bacteremia involving an organism susceptible to an acceptably bioavailable oral antibiotic agent. Using inverse probability of treatment-weighted models based on propensity scores adjusting for potential clinical confounders, we compared outcomes of those transitioned to oral antibiotics with those who continued intravenous (IV) therapy for the duration of treatment. Primary endpoints were mortality, bacteremia recurrence, and reinitiation of IV antibiotics. Secondary endpoints included length of stay, Clostridioides difficile infection, treatment-associated complications, and tunneled central venous catheter placement.

RESULTS

A total of 120 bacteremia events from 107 patients met inclusion criteria in the oral group and 42 events from 40 patients in the IV group. There were no significant differences in mortality, bacteremia recurrence, or reinitiation of IV antibiotics between groups. Patients transitioned to oral antibiotics had an average length of stay that was 1.97 days shorter (95% confidence interval [CI], -.39 to 3.56 days; P = .005). Odds of developing C. difficile and other treatment-associated complications were 8.4 times higher (95% CI, 1.5-46.6; P = .015) and 6.4 times higher (95% CI, 1.9-20.9; P = .002), respectively, in the IV group. Fifty-five percent of patients in the IV group required tunneled catheter placement. There was no difference in treatment duration between groups.

CONCLUSIONS

Oral step-down therapy was effective and associated with fewer treatment-related adverse events.

Oral β-Lactams, Fluoroquinolones, or Trimethoprim-Sulfamethoxazole for Definitive Treatment of Uncomplicated Escherichia coli or Klebsiella Species Bacteremia From a Urinary Tract Source

Background

Fluoroquinolones (FQs) are effective for oral step-down therapy for gram-negative bloodstream infections but are associated with unfavorable toxic effects. Robust data are lacking for trimethoprim-sulfamethoxazole (TMP-SMX) and high-bioavailability β-lactams (HBBLs).

Methods

In this multicenter observational cohort study, we simulated a 3-arm registry trial using causal inference methods to compare the effectiveness of FQs, TMP-SMX, or HBBLs for gram-negative bloodstream infections oral step-down therapy. The study included adults treated between January 2016 and December 2022 for uncomplicated Escherichia coli or Klebsiella species bacteremia of urinary tract origin who were who were transitioned to an oral regimen after ≤4 days of effective intravenous antibiotics. Propensity weighting was used to balance characteristics between groups. 60-day recurrence was compared using a multinomial Cox proportional hazards model with probability of treatment weighting.

Results

Of 2571 patients screened, 648 (25%) were included. Their median age (interquartile range) was 67 (45-78) years, and only 103 (16%) were male. Characteristics were well balanced between groups. Compared with FQs, TMP-SMX had similar effectiveness (adjusted hazard ratio, 0.91 [95% confidence interval, .30-2.78]), and HBBLs had a higher risk of recurrence (2.19 [.95-5.01]), although this difference was not statistically significant. Most HBBLs (70%) were not optimally dosed for bacteremia. A total antibiotic duration ≤8 days was associated with a higher recurrence rate in select patients with risk factors for failure.

Conclusions

FQs and TMP-SMX had similar effectiveness in this real-world data set. HBBLs were associated with higher recurrence rates but suboptimal dosing may have contributed. Further studies are needed to define optimal BL dosing and duration to mitigate treatment failures.

Oral Antibiotics for Bacteremia and Infective Endocarditis: Current Evidence and Future Perspectives

Bacteremia and endocarditis are two clinical syndromes that, for decades, were managed exclusively with parenteral antimicrobials, irrespective of a given patient's clinical condition, causative pathogen, or its antibiotic susceptibility profile. This clinical approach, however, was based on low-quality data and outdated expert opinions. When a patient's condition has improved, gastrointestinal absorption is not compromised, and an oral antibiotic regimen reaching adequate serum concentrations is available, a switch to oral antibacterials can be applied. Although available evidence has reduced the timing of the oral switch in bacteremia to three days/until clinical improvement, there are only scarce data regarding less than 10-day intravenous antibiotic therapy in endocarditis. Many standard or studied oral antimicrobial dosages are smaller than the approved doses for parenteral administration, which is a risk factor for treatment failure; in addition, the gastrointestinal barrier may affect drug bioavailability, especially when the causative pathogen has a minimum inhibitory concentration that is close to the susceptibility breakpoint. A considerable number of patients infected by such near-breakpoint strains may not be potential candidates for oral step-down therapy to non-highly bioavailable antibiotics like beta-lactams; different breakpoints should be determined for this setting. This review will focus on summarizing findings about pathogen-specific tailoring of oral step-down therapy for bacteremia and endocarditis, but will also present laboratory and clinical data about antibiotics such as beta-lactams, linezolid, and fosfomycin that should be studied more in order to elucidate their role and optimal dosage in this context.

Oral antibiotic step-down therapy for nonstaphylococcal gram-positive bloodstream infections

Bloodstream infections traditionally are treated with intravenous (IV) therapy. This study's purpose is to evaluate if oral step-down therapy is noninferior to IV therapy for gram-positive bloodstream infections (GP-BSIs). This retrospective cohort study included patients who received IV therapy and those who received oral step-down therapy for a nonstaphylococcal GP-BSI from 2017 to 2019. The primary endpoint was a composite outcome of 90-day all-cause mortality and clinical failure. A total of 308 patients were included (n = 94, oral; n = 214, IV). The oral step-down group had a lower incidence of 90-day clinical failure (9% vs 14%; P < 0.001). The IV group had a longer hospital stay (4 vs 6 days, P < 0.001); however, there were no significant differences in secondary outcomes. Bivariate analysis found no predictors of 90-day clinical failure. Oral step-down therapy was found to be noninferior to IV therapy.

Carbapenem alternatives for treatment of bloodstream infections due to AmpC producing enterobacterales

INTRODUCTION

Carbapenems (CR) have traditionally been the first line treatment for bacteremia caused by AmpC-producing Enterobacterales. However, CR have a high ecological impact, and carbapenem-resistant strains continue rising. Thus, other treatment alternatives like Piperacillin-Tazobactam (P-T) or Cefepime (CEF) and oral sequential therapy (OST) are being evaluated.

METHODS

We conducted a retrospective, single-centre observational study. All adult patients with AmpC-producing Enterobacterales bacteremia were included. The primary endpoint was clinical success defined as a composite of clinical cure, 14-day survival, and no adverse events. We evaluated the evolution of patients in whom OST was performed.

RESULTS

Seventy-seven patients were included, 22 patients in the CR group and 55 in the P-T/CEF group (37 patients received CEF and 18 P-T). The mean age of the patients was higher in the P-T/CEF group (71 years in CR group vs. 76 years in P-T/CEF group, p = 0.053). In the multivariate analysis, age ≥ 70 years (OR 0.08, 95% CI [0.007-0.966], p = 0.047) and a Charlson index ≥ 3 (OR 0.16, 95% CI [0.026-0.984], p = 0.048), were associated with a lower clinical success. Treatment with P-T/CEF was associated with higher clinical success (OR 7.75, 95% CI [1.273-47.223], p = 0.026). OST was performed in 47% of patients. This was related with a shorter in-hospital stay (OST 14 days [7-22] vs. non-OST 18 days [13-38], p = 0.005) without difference in recurrence (OST 3% vs. non-OST 5%, p = 0.999).

CONCLUSIONS

Targeted treatment with P-T/CEF and OST could be safe and effective treatments for patients with AmpC-producing Enterobacterales bacteremia.

Capsular polysaccharide-amikacin nanoparticles for improved antibacterial and antibiofilm performance

Natural nanoscale polysaccharide and its application have attracted much attention in recent years. In this study, we report for the first time that a novel naturally occurring capsular polysaccharide (CPS-605) from Lactobacillus plantarum LCC-605, which can self-assemble into spherical nanoparticles with an average diameter of 65.7 nm. To endow CPS-605 with more functionalities, we develop amikacin-functionalized capsular polysaccharide (CPS) nanoparticles (termed CPS-AM NPs) with improved antibacterial and antibiofilm activities against both Escherichia coli and Pseudomonas aeruginosa. They also exhibit faster bactericidal activity than AM alone. The high local positive charge density of CPS-AM NPs facilitates the interaction between the NPs and bacteria, leading to extraordinary bactericidal efficiencies (99.9 % and 100 % for E. coli and P. aeruginosa, respectively, within 30 min) by damaging the cell wall. Very interestingly, CPS-AM NPs exhibit an unconventional antibacterial mechanism against P. aeruginosa, that is, they can induce plasmolysis, along with bacterial cell surface disruption, cell inclusion release and cell death. In addition, CPS-AM NPs exhibit low cytotoxicity and negligible hemolytic activity, showing excellent biocompatibility. The CPS-AM NPs provide a new strategy for the design of next-generation antimicrobial agents that can reduce the working concentration of antibiotics to fight against bacterial resistance.

Highly versus less bioavailable oral antibiotics in the treatment of gram-negative bloodstream infections: a propensity-matched cohort analysis

OBJECTIVES

In this study, we evaluated the clinical outcomes associated with the use of highly bioavailable oral antibiotics (fluoroquinolones and trimethoprim-sulfamethoxazole) compared with the less-bioavailable oral antibiotics (β-lactams) in gram-negative bloodstream infections (BSIs).

METHODS

Among hospitalized older adult patients in Ontario, Canada, discharged home on oral treatment for gram-negative BSI between 1 January 2017 and 31 December 2019, we used a matched cohort design to compare outcomes among those receiving highly versus less-bioavailable agents; hard-matching 1:1 on sex, BSI pathogen (Escherichia coli vs. non-E. coli), and infection source (urinary vs. non-urinary/unknown source) along with a propensity score, incorporating specific pathogen, patient, and infection characteristics. The primary outcome was the composite of 90-day all-cause mortality, recurrent BSI with the same pathogen (genus and species), and re-admission to any Ontario hospital.

RESULTS

A total of 2012 patients were included in the study (1006 in each bioavailability category). Those who received highly (compared with less) bioavailable antibiotics at discharge had lower rates of the composite outcome (171/1006 [17.0%] vs. 216/1006 [21.5%]), adjusted odds ratio being 0.74 (95% CI, 0.60-0.92). Recurrent BSI at 90 days was the main driver for the composite outcome occurring in 64 (5.4%) and 107 (9.4%) patients of the highly and less-bioavailable groups, respectively (p < 0.001) (adjusted odds ratio, 0.56; 95% CI, 0.40-0.78).

DISCUSSION

Use of highly (compared with less) bioavailable antibiotics at discharge was associated with significantly better clinical outcomes among patients with gram-negative BSIs.

Impact of specialty on the self-reported practice of using oral antibiotic therapy for definitive treatment of bloodstream infections

Background:

No established guidelines exist regarding the role of oral antibiotic therapy (OAT) to treat bloodstream infections (BSIs), and practices may vary depending on clinician specialty and experience.

Objective:

To assess practice patterns regarding oral antibiotic use for treatment of bacteremia in infectious diseases clinicians (IDCs, including physicians and pharmacists and trainees in these groups) and non–infectious diseases clinicians (NIDCs).

Design:

Open-access survey.

Participants:

Clinicians caring for hospitalized patients receiving antibiotics.

Methods:

An open-access, web-based survey was distributed to clinicians at a Midwestern academic medical center using e-mail and to clinicians outside the medical center using social media. Respondents answered questions regarding confidence prescribing OAT for BSI in different scenarios. We used χ2 analysis for categorical data evaluated association between responses and demographic groups.

Results:

Of 282 survey responses, 82.6% of respondents were physicians, 17.4% pharmacists, and IDCs represented 69.2% of all respondents. IDCs were more likely to select routine use of OAT for BSI due to gram-negative anaerobes (84.6% vs 59.8%; P < .0001), Klebsiella spp (84.5% vs 69.0%; P < .009), Proteus spp (83.6% vs 71.3%; P < .027), and other Enterobacterales (79.5% vs 60.9%; P < .004). Our survey results revealed significant differences in selected treatment of Staphylococcus aureus syndromes. Fewer IDCs than NIDCs selected OAT to complete treatment for methicillin-resistant S. aureus (MRSA) BSI due to gluteal abscess (11.9% vs 25.6%; P = .012) and methicillin-susceptible S. aureus (MSSA) BSI due to septic arthritis (13.9% vs 20.9%; P = .219).

Conclusions:

Practice variation and discordance with evidence for the use of OAT for BSIs exists among IDCs versus NIDCs, highlighting opportunities for education in both clinician groups.

Intravenous to oral transition of antibiotics for gram-negative bloodstream infection at a University hospital in Thailand: Clinical outcomes and predictors of treatment failure

Background

Limited studies evaluate the outcome of intravenous antibiotics to oral transition in Gram-negative bloodstream infection (GN-BSI), particularly GN-BSI originating outside the urinary tract. This study aimed to evaluate treatment success in patients with GN-BSI treated with either intravenous therapy or intravenous to oral transition and to identify factors associated with treatment failure in those undergoing intravenous to oral transition.

Methods

A retrospective cohort study was conducted at King Chulalongkorn Memorial Hospital, Thailand. Patients were included if they were ≥18 years of age, hospitalized in general medical wards with GN-BSI between August 1, 2015, to July 31, 2020, received intravenous antibiotic agents and had a functioning gastrointestinal tract.

Results

Of 955 patients, 545 (57.1%) were in the intravenous to oral transition group. The urinary tract was the most common source of infection (38.8%). Ciprofloxacin was the most prescribed oral antibiotic (53%). Treatment success occurred in 94.3% in the intravenous antibiotic to oral transition group. There was no significant difference in treatment success between the two groups (P = 0.790) with a concordant result after using propensity score matching (P = 0.223). Independent predictors of treatment failure in the intravenous to oral transition group included metastatic solid cancer (aOR = 4.355), HIV infection with CD₄ < 200 cells/mm³ (aOR = 8.452), qSOFA score ≥ 2 (aOR = 2.545), multidrug-resistant infection (aOR = 2.849), and respiratory tract infection (aOR = 8.447). Hospital length of stay in the intravenous to oral transition group was shorter than in the intravenous group (P < 0.001).

Conclusions

Intravenous to oral transition may be a practical approach in GN-BSI. Patients with Gram-negative bacteremia who have HIV infection with CD₄ < 200 cells/mm³, multidrug-resistant infections, and respiratory tract sources of infection may not be ideal candidates for this approach. Future research is needed from a randomized controlled trial.

Thiamine Demonstrates Bio-Preservative and Anti-Microbial Effects in Minced Beef Meat Storage and Lipopolysaccharide (LPS)-Stimulated RAW 264.7 Macrophages

This study assessed the anti-inflammatory effect of thiamine (TA) in lipopolysaccharide-stimulated RAW264.7 cells and also assessed the preservative properties of TA in minced beef. TA demonstrated a concentration-dependent antimicrobial effect on microbial contaminants. Inhibition zones and MIC from the effect of TA on the tested bacterial strains were respectively within the ranges 15−20 mm and 62.5−700 µg/mL. TA significantly (p < 0.05) decreased all the pro-inflammatory factors [(nitric oxide (NO), prostaglandin E2 (PGE2), TNF-α, IL-6, IL-1β, and nuclear factor-κB (NF-κB)] monitored relative to LPS-stimulated RAW264.7 cells. TA inhibited the expression of both iNOS and COX-2. In minced beef flesh, the growth of Listeria monocytogenes was inhibited by TA. TA improved physicochemical and microbiological parameters of stored minced beef meat compared to control. Principal component analyses and heat maps elucidate the quality of the tested meats.

Immediate hypersensitivity to fluoroquinolones: a cohort assessing cross-reactivity

Background

Fluoroquinolones are the second-most prescribed antimicrobial and are frequently associated with causing hypersensitivity reactions. Existing evidence regarding cross-reactivity of fluoroquinolones is limited, offering clinicians little guidance in understanding the implications of selecting an in-class alternative among patients with histories of allergic reactions to fluoroquinolones. The aim of this study was to compare the frequency of immediate hypersensitivity reactions to either ciprofloxacin, levofloxacin, and/or moxifloxacin among patients with a history of immediate hypersensitivity to a different fluoroquinolone.

Methods

This retrospective chart review included adult patients with a history of an immediate hypersensitivity reaction to ciprofloxacin, levofloxacin, and/or moxifloxacin and a documented prescription for a different fluoroquinolone. The primary outcome was documentation of a hypersensitivity reaction upon second fluoroquinolone exposure.

Results

A total of 321 cases met inclusion criteria. Of these cases, 2.5% experienced an immediate hypersensitivity reaction after second fluoroquinolone exposure to ciprofloxacin, levofloxacin, and/or moxifloxacin. Within the ciprofloxacin, levofloxacin, and moxifloxacin index allergy cohorts, the frequency of cross-reactivity were 2.7%, 2.2%, and 5.3%, respectively.

Conclusion

Our data suggest that patients with a history of immediate hypersensitivity reaction to ciprofloxacin, levofloxacin, and/or moxifloxacin are at low risk of experiencing a cross-reaction when exposed to a different fluoroquinolone. Avoidance of all fluoroquinolones in this patient population may not be warranted.

Genomic Analysis of Carbapenem-Resistant Pseudomonas aeruginosa Isolated From Urban Rivers Confirms Spread of Clone Sequence Type 277 Carrying Broad Resistome and Virulome Beyond the Hospital

The dissemination of antibiotic-resistant priority pathogens beyond hospital settings is both a public health and an environmental problem. In this regard, high-risk clones exhibiting a multidrug-resistant (MDR) or extensively drug-resistant (XDR) phenotype have shown rapid adaptation at the human-animal-environment interface. In this study, we report genomic data and the virulence potential of the carbapenemase, São Paulo metallo-β-lactamase (SPM-1)-producing Pseudomonas aeruginosa strains (Pa19 and Pa151) isolated from polluted urban rivers, in Brazil. Bioinformatic analysis revealed a wide resistome to clinically relevant antibiotics (carbapenems, aminoglycosides, fosfomycin, sulfonamides, phenicols, and fluoroquinolones), biocides (quaternary ammonium compounds) and heavy metals (copper), whereas the presence of exotoxin A, alginate, quorum sensing, types II, III, and IV secretion systems, colicin, and pyocin encoding virulence genes was associated with a highly virulent behavior in the Galleria mellonella infection model. These results confirm the spread of healthcare-associated critical-priority P. aeruginosa belonging to the MDR sequence type 277 (ST277) clone beyond the hospital, highlighting that the presence of these pathogens in environmental water samples can have clinical implications for humans and other animals.

Risk Factors for Adverse Events in Children Receiving Outpatient Parenteral Antibiotic Therapy

BACKGROUND

Outpatient parenteral antibiotic therapy (OPAT) can decrease length of hospital stay but is associated with adverse events (AEs). The purpose of this study was to quantify and identify risk factors for OPAT-associated AEs in children.

METHODS

Retrospective single-center study of children ≤21 years old discharged on OPAT from January 2016 to April 2019 with infectious diseases follow-up. Demographic and clinical factors and medication and central venous catheter (CVC)-associated AEs were assessed through chart review. Univariable and multivariable analyses were performed.

RESULTS

Among 181 OPAT courses, an AE occurred in 70 (39%). Medication AEs occurred in 30 of 181 courses (16.6%). Children residing in an urban area had a 4.5 times higher risk of having a medication-related AE compared with those in a rural area (odds ratio: 4.51; 95% confidence interval: 1.60-12.77; P = .005). CVC AEs occurred in 47 of 181 courses (26%). Every additional day of OPAT increased the odds of having a CVC-related AE by 4% (odds ratio: 1.04; 95% confidence interval: 1.01-1.07; P = .003). Twenty (11.1%) courses resulted in readmission to the hospital because of an AE.

CONCLUSIONS

In this cohort, 39% of children experienced an OPAT-associated AE, and CVC AEs were more common than medication AEs. Longer duration of intravenous therapy and urban residence were independently associated with OPAT-associated AEs, highlighting the importance of converting to oral antibiotic therapy as soon as feasible to reduce OPAT-associated AEs.

A New Water-Soluble Bactericidal Agent for the Treatment of Infections Caused by Gram-Positive and Gram-Negative Bacterial Strains

Grapefruit and lemon pectin obtained from the respective waste citrus peels via hydrodynamic cavitation in water only are powerful, broad-scope antimicrobials against Gram-negative and -positive bacteria. Dubbed IntegroPectin, these pectic polymers functionalized with citrus flavonoids and terpenes show superior antimicrobial activity when compared to commercial citrus pectin. Similar to commercial pectin, lemon IntegroPectin determined ca. 3-log reduction in Staphylococcus aureus cells, while an enhanced activity of commercial citrus pectin was detected in the case of Pseudomonas aeruginosa cells with a minimal bactericidal concentration (MBC) of 15 mg mL⁻¹. Although grapefruit and lemon IntegroPectin share equal MBC in the case of P. aeruginosa cells, grapefruit IntegroPectin shows boosted activity upon exposure of S. aureus cells with a 40 mg mL⁻¹ biopolymer concentration affording complete killing of the bacterial cells. Insights into the mechanism of action of these biocompatible antimicrobials and their effect on bacterial cells, at the morphological level, were obtained indirectly through Fourier Transform Infrared spectroscopy and directly through scanning electron microscopy. In the era of antimicrobial resistance, these results are of great societal and sanitary relevance since citrus IntegroPectin biomaterials are also devoid of cytotoxic activity, as already shown for lemon IntegroPectin, opening the route to the development of new medical treatments of polymicrobial infections unlikely to develop drug resistance.