Clinical Impact of Ceftriaxone Resistance in Escherichia coli Bloodstream Infections: A Multicenter Prospective Cohort Study.

Background: Ceftriaxone-resistant (CRO-R) Escherichia coli bloodstream infections (BSIs) are common. Methods: This is a prospective cohort of patients with E coli BSI at 14 United States hospitals between November 2020 and April 2021. For each patient with a CRO-R E coli BSI enrolled, the next consecutive patient with a ceftriaxone-susceptible (CRO-S) E coli BSI was included. Primary outcome was desirability of outcome ranking (DOOR) at day 30, with 50% probability of worse outcomes in the CRO-R group as the null hypothesis. Inverse probability weighting (IPW) was used to reduce confounding. Results: Notable differences between patients infected with CRO-R and CRO-S E coli BSI included the proportion with Pitt bacteremia score ≥4 (23% vs 15%, P = .079) and the median time to active antibiotic therapy (12 hours [interquartile range {IQR}, 1-35 hours] vs 1 hour [IQR, 0-6 hours]; P < .001). Unadjusted DOOR analyses indicated a 58% probability (95% confidence interval [CI], 52%-63%) for a worse clinical outcome in CRO-R versus CRO-S BSI. In the IPW-adjusted cohort, no difference was observed (54% [95% CI, 47%-61%]). Secondary outcomes included unadjusted and adjusted differences in the proportion of 30-day mortality between CRO-R and CRO-S BSIs (-5.3% [95% CI, -10.3% to -.4%] and -1.8 [95% CI, -6.7% to 3.2%], respectively), postculture median length of stay (8 days [IQR, 5-13 days] vs 6 days [IQR, 4-9 days]; P < .001), and incident admission to a long-term care facility (22% vs 12%, P = .045). Conclusions: Patients with CRO-R E coli BSI generally have poorer outcomes compared to patients infected with CRO-S E coli BSI, even after adjusting for important confounders.

Locally delivered antistaphylococcal lysin exebacase or CF-296 is active in methicillin-resistant Staphylococcus aureus implant-associated osteomyelitis.

Introduction: Staphylococcus aureus is the most common cause of orthopedic infections and can be challenging to treat, especially in the presence of a foreign body. The antistaphylococcal lysins exebacase and CF-296 have rapid bactericidal activity, a low propensity for resistance development, and synergize with some antibiotics. Methods: Rabbit implant-associated osteomyelitis was induced by drilling into the medial tibia followed by locally delivering exebacase, CF-296, or lysin carrier. A titanium screw colonized with methicillin-resistant S. aureus (MRSA) IDRL-6169 was inserted. Intravenous daptomycin or saline was administered and continued daily for 4 d. On day 5, rabbits were euthanized, and the tibiae and implants were collected for culture. Results were reported as log 10 colony forming units (cfu) per gram of bone or log 10  cfu per implant, and comparisons among the six groups were performed using the Wilcoxon rank sum test. Results: Based on implant and bone cultures, all treatments resulted in significantly lower bacterial counts than those of controls ( P ≤ 0.0025 ). Exebacase alone or with daptomycin as well as CF-296 with daptomycin were more active than daptomycin alone ( P ≤ 0.0098 ) or CF-296 alone ( P ≤ 0.0154 ) based on implant cultures. CF-296 with daptomycin was more active than either CF-296 alone ( P = 0.0040 ) or daptomycin alone ( P = 0.0098 ) based on bone cultures. Conclusion: Local delivery of either exebacase or CF-296 offers a promising complement to conventional antibiotics in implant-associated infections.

Dual antimicrobial-loaded biodegradable nanoemulsions for synergistic treatment of wound biofilms.

Wound biofilm infections caused by multidrug-resistant (MDR) bacteria constitute a major threat to public health; acquired resistance combined with resistance associated with the biofilm phenotype makes combatting these infections challenging. Biodegradable polymeric nanoemulsions that encapsulate two hydrophobic antimicrobial agents (eugenol and triclosan) (TE-BNEs) as a strategy to combat chronic wound infections are reported here. The cationic nanoemulsions efficiently penetrate and accumulate in biofilms, synergistically eradicating MDR bacterial biofilms, including persister cells. Notably, the nanoemulsion platform displays excellent biocompatibility and delays emergence of resistance to triclosan. The TE-BNEs are active in an in vivo murine model of mature MDR wound biofilm infections, with 99% bacterial elimination. The efficacy of this system coupled with prevention of emergence of bacterial resistance highlight the potential of this combination platform to treat MDR wound biofilm infections.

Activity of Omadacycline in Rat Methicillin-Resistant Staphylococcus aureus Osteomyelitis.

Omadacycline, vancomycin, and rifampin, as well as rifampin combination therapies, were evaluated in an experimental rat model of methicillin-resistant Staphylococcus aureus (MRSA) osteomyelitis. All treatment groups had less MRSA recovered than saline-treated animals. The emergence of rifampin resistance was observed in 3 of 16 animals with rifampin monotherapy and none with rifampin combination therapy. After treatment, the median tibial bacterial loads were 6.04, 0.1, 4.81, and 5.24 log10 CFU/g for saline-, rifampin-, vancomycin-, and omadacycline-treated animals, respectively. Omadacycline or vancomycin administered with rifampin yielded no detectable MRSA. Omadacycline administered with rifampin deserves evaluation in humans as a potential treatment for osteomyelitis.

Nanotherapeutics using all-natural materials. Effective treatment of wound biofilm infections using crosslinked nanoemulsions.

Bacterial wound infections are a threat to public health. Although antibiotics currently provide front-line treatments for bacterial infections, the development of drug resistance coupled with the defenses provided through biofilm formation render these infections difficult, if not impossible, to cure. Antimicrobials from natural resources provide unique antimicrobial mechanisms and are generally recognized as safe and sustainable. Herein, an all-natural antimicrobial platform is reported. It is active against bacterial biofilms and accelerates healing of wound biofilm infections in vivo. This antimicrobial platform uses gelatin stabilized by photocrosslinking using riboflavin (vitamin B2) as a photocatalyst, and carvacrol (the primary constituent of oregano oil) as the active antimicrobial. The engineered nanoemulsions demonstrate broad-spectrum antimicrobial activity towards drug-resistant bacterial biofilms and significantly expedite wound healing in an in vivo murine wound biofilm model. The antimicrobial activity, wound healing promotion, and biosafety of these nanoemulsions provide a readily translatable and sustainable strategy for managing wound infections.

Polymeric Nanoparticles Active against Dual-Species Bacterial Biofilms.

Biofilm infections are a global public health threat, necessitating new treatment strategies. Biofilm formation also contributes to the development and spread of multidrug-resistant (MDR) bacterial strains. Biofilm-associated chronic infections typically involve colonization by more than one bacterial species. The co-existence of multiple species of bacteria in biofilms exacerbates therapeutic challenges and can render traditional antibiotics ineffective. Polymeric nanoparticles offer alternative antimicrobial approaches to antibiotics, owing to their tunable physico-chemical properties. Here, we report the efficacy of poly(oxanorborneneimide) (PONI)-based antimicrobial polymeric nanoparticles (PNPs) against multi-species bacterial biofilms. PNPs showed good dual-species biofilm penetration profiles as confirmed by confocal laser scanning microscopy. Broad-spectrum antimicrobial activity was observed, with reduction in both bacterial viability and overall biofilm mass. Further, PNPs displayed minimal fibroblast toxicity and high antimicrobial activity in an in vitro co-culture model comprising fibroblast cells and dual-species biofilms of Escherichia coli and Pseudomonas aeruginosa. This study highlights a potential clinical application of the presented polymeric platform.

Activity of Biodegradable Polymeric Nanosponges against Dual-Species Bacterial Biofilms.

Infections caused by multidrug-resistant (MDR) bacteria present an emerging global health crisis, and the threat is intensified by the involvement of biofilms. Some biofilm infections involve more than one species; this can further challenge treatment using traditional antibiotics. Nanomaterials are being developed as alternative therapeutics to traditional antibiotics; here we report biodegradable polymer-stabilized oil-in-water nanosponges (BNS) and show their activity against dual-species bacterial biofilms. The described engineered nanosponges demonstrated broad-spectrum antimicrobial activity through prevention of dual-species biofilm formation as well as eradication of preformed biofilms. The BNS showed no toxicity against mammalian cells. Together, these data highlight the therapeutic potential of this platform.

In situ Generation of Antibiotics using Bioorthogonal "Nanofactories".

Prodrug strategies use chemical modifications to improve the pharmacokinetic properties and therefore therapeutic effects of parent drugs. Traditional prodrug approaches use endogenous enzymes for activation. Bioorthogonal catalysis uses processes that endogenous enzymes cannot access, providing a complementary strategy for prodrug uncaging. Site-selective activation of prodrugs to drugs (uncaging) using synthetic catalysts is a promising strategy for localized drug activation. We discuss here recent studies that incorporate metal catalysts into polymers and nanoparticle scaffolds to provide biocompatible "enzyme-like" catalysts that can penetrate bacterial biofilms and activate prodrug antibiotics in situ, affording a new strategy to treat bacterial biofilm infections with the potential for reduced off-target effects.

Nanomaterial-based therapeutics for antibiotic-resistant bacterial infections.

Antibiotic-resistant bacterial infections arising from acquired resistance and/or through biofilm formation necessitate the development of innovative 'outside of the box' therapeutics. Nanomaterial-based therapies are promising tools to combat bacterial infections that are difficult to treat, featuring the capacity to evade existing mechanisms associated with acquired drug resistance. In addition, the unique size and physical properties of nanomaterials give them the capability to target biofilms, overcoming recalcitrant infections. In this Review, we highlight the general mechanisms by which nanomaterials can be used to target bacterial infections associated with acquired antibiotic resistance and biofilms. We emphasize design elements and properties of nanomaterials that can be engineered to enhance potency. Lastly, we present recent progress and remaining challenges for widespread clinical implementation of nanomaterials as antimicrobial therapeutics.

Novel Use of Rifabutin and Rifapentine to Treat Methicillin-Resistant Staphylococcus aureus in a Rat Model of Foreign Body Osteomyelitis.

BACKGROUND: Owing to patient intolerance or drug interactions, alternative agents to rifampin are needed for management of staphylococcal periprosthetic joint infection. In the current study, we evaluated rifabutin, rifapentine and rifampin, with and without vancomycin, in a rat model of foreign body osteomyelitis. METHODS: Proximal tibiae were inoculated with methicillin-resistant Staphylococcus aureus (MRSA) and a Kirschner wire (K-wire) implanted in each. After 4 weeks of infection, rifampin, rifabutin, or rifapentine were administered, alone or with vancomycin. Tibiae and K-wires were cultured, and medians were reported as log10 colony-forming units (CFUs) per gram of bone or log10 CFUs per K-wire, respectively. RESULTS: Rifampin, rifabutin or rifapentine administered with vancomycin yielded less MRSA from bones (0.10, 3.02, and 0.10 log10 CFUs/g, respectively) than did no treatment (4.36 log10 CFUs/g) or vancomycin alone (4.64 log10 CFUs/g) (both P ≤ .02). The K-wires of animals receiving no treatment or vancomycin monotherapy recovered medians of 1.76 and 2.91 log10 CFUs/g per K-wire, respectively. In contrast, rifampin, rifabutin and rifapentine administered with vancomycin yielded medians of 0.1 log10 CFUs per K-wire, respectively. Rifampin resistance was detected in a single animal in the rifampin monotherapy group. CONCLUSIONS: Rifabutin or rifapentine with vancomycin were as active as rifampin with vancomycin against MRSA in rat foreign body osteomyelitis, suggesting that rifabutin and/or rifapentine may be alternatives to rifampin in the clinical management of staphylococcal periprosthetic joint infections.

Planktonic and Biofilm Activity of Eravacycline against Staphylococci Isolated from Periprosthetic Joint Infections.

MIC and minimum biofilm bactericidal concentration (MBBC) values of eravacycline against 185 staphylococci from periprosthetic joint infections were determined. Staphylococcus aureus had MICs of ≤0.25 µg/ml. MICs for methicillin-susceptible and -resistant Staphylococcus epidermidis were ≤1 and ≤2 µg/ml, respectively. S. aureus and S. epidermidis MBBC50 and MBBC90 values were 8 and 16 µg/ml for each, showing poor anti-staphylococcal biofilm activity using the method studied.

Imipenem-Relebactam Susceptibility Testing of Gram-Negative Bacilli by Agar Dilution, Disk Diffusion, and Gradient Strip Methods Compared with Broth Microdilution.

This study aimed to determine whether agar dilution, research-use-only disk diffusion (Mast Group Ltd., Bootle Merseyside, UK), Etest (bioMérieux, Inc., Durham, NC), and MIC test strip (MTS) (Liofilchem, Inc., Waltham, MA) methods yield equivalent results to those of broth microdilution (BMD) for imipenem-relebactam susceptibility testing using a collection of 297 Gram-negative bacilli, including members of the order Enterobacterales and Pseudomonas aeruginosa, enriched for drug resistance. MIC and disk diameter results were interpreted using United States Food and Drug Administration breakpoints. Overall, 76.8% of the isolates tested were susceptible to imipenem-relebactam by BMD. MIC values for agar dilution, Etest, and MTS were not significantly different from that for BMD, although they tended to be 1 to 2 dilutions higher. Essential agreement was 95.6% for agar dilution, 90.6% for Etest, and 85.2% for MTS. Categorical agreement was 98.0% for agar dilution, 73.1% for disk diffusion, 96.3% for Etest, and 96.6% for MTS. In conclusion, agar dilution and Etest yielded comparable results to BMD for imipenem-relebactam.

In vitro activity of TNP-2092 against periprosthetic joint infection-associated staphylococci.

Staphylococci are the most common causes of periprosthetic joint infection (PJI). TNP-2092 is an investigational hybrid drug composed of rifamycin and quinolizinone pharmacophores conjugated via a covalent linker. We determined minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and minimum biofilm bactericidal concentration (MBBC) values of TNP-2092 against 80 PJI-associated Staphylococcus aureus and Staphylococcus epidermidis isolates compared to ciprofloxacin and rifampin alone and in combination, alongside daptomycin and vancomycin. TNP-2092 exhibited the following activity against S. aureus: MIC50/MIC90, ≤0.0075/0.015 µg/mL; MBC50/MBC90, 0.5/4 µg/mL; and MBBC50/MBBC90, 0.5/2 µg/mL, and the following activity against S. epidermidis: MIC50/MIC90, ≤0.0075/0.015 µg/mL; MBC50/MBC90, 0.015/0.125 µg/mL; and MBBC50/MBBC90, 0.06/0.25 µg/mL. TNP-2092 MIC, MBC, and MBBC values were >8 µg/mL for 1 isolate, while MIC values were ≤0.25 µg/mL and MBC and MBBC values were ≤4 µg/mL for all other isolates. Results of this study show that TNP-2092 has promising in vitro activity against PJI-associated staphylococci.

A novel rat model of foreign body osteomyelitis for evaluation of antimicrobial efficacy.

The most common organism-type causing orthopedic foreign body infection is the staphylococci, of which Staphylococcus aureus and Staphylococcus epidermidis are especially common. These organisms form biofilms on orthopedic foreign body surfaces, rendering such infections challenging and time consuming to treat. Our group evaluates novel therapeutics for orthopedic foreign body infection in animal models. A current limitation of most animal models is that that they only allow for the removal of one sample per animal, at the time of sacrifice. Herein, we describe a novel rat model of foreign body osteomyelitis that allows removal of foreign bodies at different time points, from the same infected animal. We demonstrate that this model can be used for both S. aureus and S. epidermidis orthopedic foreign body infection, with 3.56, 3.60 and 5.51 log10 cfu/cm2 S. aureus recovered at four, five and six weeks, respectively, after infection, and 2.08, 2.17 and 2.62 log10 cfu/cm2 S. epidermidis recovered at four, five and six weeks, respectively, after infection We evaluated the model with S. aureus infection treated with rifampin 25 mg/kg twice daily for 21 days. Using quantitative cultures, we were no longer able to detect bacteria as of the 14th day of treatment with bacteria becoming detectable again 7 days following die discontinuation of rifampin a period. This novel model allows monitoring of evolution of infection at the infection site in the same animal.

Exebacase in Addition to Daptomycin Is More Active than Daptomycin or Exebacase Alone in Methicillin-Resistant Staphylococcus aureus Osteomyelitis in Rats.

Bacteriophage-derived lysins are being developed as anti-infective agents. In an acute osteomyelitis methicillin-resistant Staphylococcus aureus (MRSA) model, rats receiving no treatment or treatment with daptomycin, exebacase (CF-301), or daptomycin plus exebacase had means of 5.13, 4.09, 4.65, and 3.57 log10 CFU/gram of bone, respectively. All treated animals had fewer bacteria than did untreated animals (P ≤ 0.0001), with daptomycin plus exebacase being more active than daptomycin (P = 0.0042) or exebacase (P < 0.001) alone.

Effect of Direct Electrical Current on Bones Infected with Staphylococcus epidermidis.

We are developing electrical approaches to treat biofilm-associated orthopedic foreign-body infection. Although we have previously shown that such approaches have antibiofilm activity, the effects on bone have not been assessed. Herein, low-amperage 200 µA fixed direct current (DC) was compared with no current, in a rat femoral foreign-body infection model. In the infected group, a platinum implant seeded with S. epidermidis biofilm (105 CFU/cm2), plus 50 µL of a 109 CFU suspension of bacteria, were placed in the femoral medullary cavity of 71 rats. One week later, rats were assigned to one of four groups: infected with no current or DC, or uninfected with no current or DC. After 2 weeks, bones were removed and subjected to histopathology, micro-computed tomography (µCT), and strength testing. Histopathology showed no inflammation or bony changes/remodeling in the uninfected no current group, and some osteoid formation in the DC group; bones from the infected no current group had evidence of inflammation without bony changes/remodeling; along with inflammation, there was moderate osteoid present in the DC group. µCT showed more cortical bone volume and density, trabecular thickness, and cancellous bone volume in the DC group compared with the no current group, for both uninfected and infected bones (p < 0.05). There was no difference in torsional strength or stiffness between the no current versus DC groups, for both infected and uninfected bones (p > 0.05). © 2018 The Authors. JBMR Plus Published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

Oritavancin polymethylmethacrylate (PMMA)-compressive strength testing and in vitro elution.

BACKGROUND: Polymethylmethacrylate (PMMA) is used for local antimicrobial delivery in orthopedic infection. Oritavancin is a long half-life lipoglycopeptide with broad activity against Gram-positive bacteria. Herein, we addressed if 7.5% w/w oritavancin mixed into PMMA affects PMMA strength and whether it elutes from PMMA, compared to vancomycin. METHODS: Elution was assessed by placing an oritavancin- or vancomycin-loaded bead in a flow system with human plasma. Compressive strength of bland compared to oritavancin- or vancomycin-loaded PMMA was assessed after 0, 3, and 7 days of soaking in 1 ml of pooled normal human plasma at 37 °C, by testing to failure in axial compression using a servo-hydraulic testing machine. RESULTS: Median compressive strength on days 0, 3, and 7 for bland PMMA compared to oritavancin- or vancomycin-loaded PMMA was 80.1, 79.4, and 72.4 MPa, respectively; 93.3, 86.4, and 65.3 MPa, respectively; and 97.8, 82.7, and 65.9 MPa, respectively. Oritavancin reduced PMMA compressive strength after 3 and 7 days (P = 0.0250 and 0.0039, respectively), whereas vancomycin reduced the PMMA compressive strength after 0, 3, and 7 days (P = 0.0039, 0.0039, and 0.0062, respectively) as compared to bland PMMA. Oritavancin-loaded PMMA had higher compressive strength than vancomycin-loaded PMMA on days 3 and 7 (P = 0.0039 and 0.0062, respectively). Compressive elastic moduli were 1226, 1299, and 1394 MPa for bland PMMA; 1253, 1078, and 1245 MPa for oritavancin-loaded PMMA; and 986, 879, and 779 MPa for vancomycin-loaded PMMA on days 0, 3 and 7, respectively. Oritavancin-loaded PMMA had higher compressive elastic moduli than vancomycin-loaded PMMA on days 0 and 7 (P = 0.0250 and 0.0062, respectively). Following polymerization, 1.0% and 51.9% of the initial amount of oritavancin and vancomycin were detected, respectively. Cmax, Tmax, and AUC0-24 were 1.7 µg/ml, 2 h, and 11.4 µg/ml for oritavancin and 21.4 µg/ml, 2 h, and 163.9 µg/ml for vancomycin, respectively. CONCLUSIONS: Oritavancin-loaded PMMA had higher compressive strength than vancomycin-loaded PMMA on days 3 and 7 and higher compressive elastic moduli than vancomycin-loaded PMMA on days 0 and 7. However, proportionally less oritavancin than vancomycin eluted out of PMMA.

Activity of fixed direct electrical current in experimental Staphylococcus aureus foreign-body osteomyelitis.

Fixed DC was compared to ceftriaxone, ceftriaxone with 200 µA fixed DC, or no treatment in a rat model of methicillin-susceptible Staphylococcus aureus foreign-body osteomyelitis. After 3 weeks, fewer bacteria were present in bones of the ceftriaxone group (5.71 log10cfu/g [P = 0.0004]) and the ceftriaxone/DC group (3.53 log10cfu/g [P = 0.0002]) than untreated controls (6.70 log10cfu/g). Fewer bacteria were present in the ceftriaxone/DC group than in the ceftriaxone-alone and DC-alone groups (P = 0.0012 and 0.0008, respectively). There were also fewer bacteria on the implanted wires in the groups treated with ceftriaxone (5.47 log10cfu/cm2) or ceftriaxone/DC (2.82 log10cfu/cm2) than in the untreated controls (6.44 log10cfu/cm2 [P = 0.0003 and 0.0002, respectively]). There were fewer bacteria in the ceftriaxone/DC rats than in the ceftriaxone-alone- and fixed DC-alone-treated rats (P = 0.0017 and 0.0016, respectively). Fixed DC with an antibiotic may be useful for treating foreign-body infections caused by S. aureus.