Principles of Antibiotic Penetration into Abscess Fluid

Safety and Feasibility of Photodynamic Therapy for Percutaneous Image-guided Abdominopelvic Abscess Drainage: Phase 1 Trial

Background Standard-of-care abscess management includes image-guided percutaneous drainage and antibiotics; however, cure rates vary, and concern for antibiotic-resistant bacteria is growing. Photodynamic therapy (PDT), which uses light-activated dyes to generate cytotoxic reactive oxygen species, could complement the standard of care by sterilizing the abscess at the time of drainage. Purpose To evaluate safety and feasibility of PDT with methylene blue (hereafter, MB-PDT) at the time of percutaneous abscess drainage. Materials and Methods This prospective, open-label, dose-escalation, first-in-humans, registered phase 1 clinical study of MB-PDT included participants who underwent percutaneous abdominal or pelvic abscess drainage with CT or US guidance from January 2015 to March 2020 and September 2022 to September 2023. Following drainage, MB-PDT was performed with laser illumination at a fluence rate of 20 mW/cm2, with fluence groups of 6, 12, 18, 24, 30, and 36 J/cm2 (n = 3 each). The primary outcome was safety, indicated by absence of fat embolism, MB escape, abscess wall damage, and need for surgery to remove optical fibers. Preliminary efficacy end points included the time to drainage catheter removal, drainage catheter output volume, and clinical symptom and fever duration. Relationships between fluence and outcomes were analyzed with Spearman correlation and linear regression analyses, and ordinary one-way analysis of variance was used for group comparisons. Results MB-PDT was safe and feasible in all 18 participants (mean age, 60.1 years ± 18.3 [SD]; 10 female), with no negative safety outcomes observed for any participant. No study-related adverse events were encountered, and the procedure did not increase reported pain (P = .1). Clinical symptom and fever duration was shorter in participants receiving higher fluences (30 and 36 J/cm2 vs 6 J/cm2) (P = .03). The presence of antibiotic-resistant bacteria was not predictive of clinical symptom and fever duration (β = 0.13, P = .37). Conclusion MB-PDT was a safe and feasible adjunct to image-guided percutaneous abscess drainage. Clinical measures indicated a dose-dependent response to PDT. ClinicalTrials.gov registration no.: NCT02240498 © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Johnston and Goldberg in this issue.

Imaging of MSK infections in the ER

Musculoskeletal infections in the ER are not an uncommon presentation. The clinical context is critical in determining the suspicion for infection and degree of tissue involvement which can involve all layers from the skin to bones. The location, extent, and severity of clinically suspected infection directly relate to the type of imaging performed. Uncomplicated cellulitis typically does not require any imaging. Localized and superficial infections can mostly be evaluated with ultrasound. If there is a diffuse site (an entire extremity) or suspected deeper involvement (muscle/deep fascia), then CT is accurate in diagnosing, widely available, and performed quickly. With potential osseous involvement, MRI is the gold standard for diagnosing acute osteomyelitis; however, it has the drawbacks of longer scan times, artifacts including patient motion, and limited availability.

Ten common misconceptions about antibiotic use in the hospital

Antimicrobials are one of the most administered medications in hospitals. Thoughtful and rational antibiotic prescribing by clinicians are important in reducing the adverse effects to both the host that takes the antibiotic and also the individuals in the host's community. Principles informing antibiotic prescribing in the hospital are commonly rooted in misconceptions. We review 10 common myths associated with antibacterial usage in hospitalized patients and share contemporary evidence in hopes of enhancing evidence-informed practice in this patient care setting.

Resistance development in Escherichia coli to delafloxacin at pHs 6.0 and 7.3 compared to ciprofloxacin

Understanding the resistance mechanisms of antibiotics in the micro-environment of the infection is important to assess their clinical applicability and potentially prevent resistance development. We compared the laboratory resistance evolution of Escherichia coli to delafloxacin (DLX) compared to ciprofloxacin (CIP), the co-resistance evolution, and underlying resistance mechanisms at different pHs. Three clones from each of the eight clinical E. coli isolates were subjected to subinhibitory concentrations of DLX or CIP in parallel at either pH 7.3 or 6.0. Minimum inhibitory concentrations (MICs) were regularly tested (at respective pHs), and the antibiotic concentration was adjusted accordingly. After 30 passages, MICs were determined in the presence of the efflux pump inhibitor phenylalanine-arginine-β-naphthylamide. Whole genome sequencing of the parental isolates and their resistant derivatives (n = 54) was performed. Complementation assays were carried out for selected mutations. Quantitative PCR and efflux experiments were carried out for selected derivatives. For DLX-challenged strains, resistance to DLX evolved much slower in acidic than in neutral pH, whereas for CIP-challenged strains, the opposite was the case. Mutations in the quinolone resistance-determining region were mainly seen in CIP-challenged E. coli, whereas a multifactorial mechanism including mutations in efflux-related genes played a role in DLX resistance evolution (predominantly at pH 6.0). This work provides novel insights into the resistance mechanisms of E. coli to delafloxacin and highlights the importance of understanding micro-environmental conditions at the infection site that might affect the true clinical efficacy of antibiotics and challenges our current antibiotic susceptibility-testing paradigm.

Photodynamic therapy is a safe and feasible adjunct to percutaneous drainage of deep tissue abscesses: Results of a first in humans Phase 1 clinical trial

Background

Standard of care for abscess management includes image-guided percutaneous drainage and antibiotics. However, cure rates vary between patients and there is growing concern for antibiotic-resistant bacteria. Photodynamic therapy (PDT), which utilizes light-activated dyes to generate cytotoxic reactive species, could complement the standard of care by sterilizing the abscess at time of drainage.

Purpose

The goal of this study was to perform a first in humans Phase 1 clinical study evaluating safety and feasibility of PDT with methylene blue (MB) at the time of percutaneous abscess drainage. This was accomplished through an open-label dose escalation study, with duration of light delivery escalated from 5-30 minutes.

Materials and Methods

We performed MB-PDT in 18 subjects undergoing percutaneous abscess drainage. Following standard of care drainage, 1 mg/mL MB was delivered for 10 minutes. MB was aspirated, and 1% lipid emulsion infused to homogenize light dose at the cavity wall. An optical fiber was advanced to the approximate center of the abscess for 665 nm laser illumination at 20 mW/cm 2 .

Results

MB-PDT at the time of abscess drainage was safe and feasible in all cases, with no evidence of fat embolism due to lipid emulsion or adverse reaction to MB observed. No study-related adverse or serious adverse events were encountered, and the procedure was well tolerated by all subjects. While the study was not designed or powered to determine efficacy, time to resolution of clinical symptoms was significantly decreased in subjects receiving higher fluences (p=0.028). Additionally, drainage catheter output post-procedure was decreased in subjects receiving higher fluences (ρ=-0.18), although this difference was not significant (p=0.43).

Conclusion

MB-PDT is a safe and feasible adjunct to image-guided percutaneous abscess drainage. Clinical measures indicate a dose-dependent response to PDT, motivating future Phase 2 studies evaluating the efficacy of MB-PDT in this patient population.

Understanding the coordination behavior of antibiotics: Take tetracycline as an example

Gaining insight into the occurrence states of residual antibiotics is crucial to demystify their environmental behavior. However, the complexation of heteroatoms functioned on antibiotic molecules to metal ions in the water environment is not fully understood. This study reports that a fluorescence response was unexpectedly triggered by tetracycline (TC) and Al3+, serving as solid evidence to visualize the Al3+-TC coordination reaction. Differential electron absorption spectroscopy shows a quantifiable signal of the redshifted n-π* transition with a coordination reaction, which is also proportional to the fluorescence. The occurrence of Al3+-complexed TC also caused a split in retention time in liquid chromatogram. The TC ligands were re-released in the presence of stronger ligands competing for central Al3+. The complex ratio of Al3+-TC is confirmed to be 1:1 using Job's plot with a stability constant of 1.01 × 106. Quantum chemical computations coupled with Gibbs free energy analysis simulated the formation of octahedral Al3+-TC configuration through a spontaneous bidentate chelation. This study helps convey a broad consensus and opens a new door in the mechanistic study of metal-involved antibiotic transformation process, leading to a better understanding that can ultimately be essential to reach the final goal of alleviating the antibiotic crisis.

Readmission and Associated Factors in Surgical Versus Non-Surgical Management of Spinal Epidural Abscess: A Nationwide Readmissions Database Analysis

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

Spinal epidural abscess (SEA) is a rare but potentially life-threatening infection treated with antimicrobials and, in most cases, immediate surgical decompression. Previous studies comparing medical and surgical management of SEA are low powered and limited to a single institution. As such, the present study compares readmission in surgical and non-surgical management using a large national dataset.

METHODS

We identified all hospital admissions for SEA using the Nationwide Readmissions Database (NRD), which is the largest collection of hospital admissions data. Patients were grouped into surgically and non-surgically managed cohorts using ICD-10 coding and compared using information retrieved from the NRD such as demographics, comorbidities, length of stay and cost of admission.

RESULTS

We identified 350 surgically managed and 350 non-surgically managed patients. The 90-day readmission rates for surgical and non-surgical management were 26.0% and 35.1%, respectively (P < .05). Expectedly, surgical management was associated with a significantly higher charge and length of stay at index hospital admission. Surgically managed patients had a significantly lower risk of readmission for osteomyelitis (P < .05). Finally, in patients with a low comorbidity burden, we observed a significantly lower 90-day readmission rate for surgically managed patients (surgical: 23.0%, non-surgical: 33.8%, P < .05).

CONCLUSION

In patients with a low comorbidity burden, we observed a significantly lower readmission rate for surgically managed patients than non-surgically managed patients. The results of this study suggest a lower readmission rate as an advantage to surgical management of SEA and emphasize the importance of SEA as a not-to-miss diagnosis.

Nanotechnology: a contemporary therapeutic approach in combating infections from multidrug-resistant bacteria

In the 20th century, the discovery of antibiotics played an essential role in the fight against infectious diseases, including meningitis, typhoid fever, pneumonia and Mycobacterium tuberculosis. The development of multidrug resistance in microflora due to improper antibiotic use created significant public health issues. Antibiotic resistance has increased at an alarming rate in the past few decades. Multidrug-resistant bacteria (superbugs) such as methicillin-resistant Staphylococcus aureus (MRSA) as well as drug-resistant tuberculosis pose serious health implications. Despite the continuous increase in resistant microbes, the discovery of novel antibiotics is constrained by the cost and complexities of discovery of drugs. The nanotechnology has given new hope in combating this problem. In the present review, recent developments in therapeutics utilizing nanotechnology for novel antimicrobial drug development are discussed. The nanoparticles of silver, gold and zinc oxide have proved to be efficient antimicrobial agents against multidrug-resistant Klebsiella, Pseudomonas, Escherichia Coli and MRSA. Using nanostructures as carriers for antimicrobial agents provides better bioavailability, less chances of sub-therapeutic drug accumulation and less drug-related toxicity. Nanophotothermal therapy using fullerene and antibody functionalized nanostructures are other strategies that can prove to be helpful.

BACTERIAL IDENTIFICATION AND ANTIBIOTIC SENSITIVITY FROM THE ABSCESSES OF CAPTIVE TORTOISES-CLINICAL ANTIBIOTIC RECOMMENDATIONS

Bacterial abscesses are commonly seen in tortoises. The morbidity and the resultant mortality are high. Multifactorial problems, antibiotics misapplication. and antibiotic-resistant bacteria make abscess treatment complicated and ineffective. This study identifies the etiological bacterial species and determines the best antibiotics for abscess treatment in captive tortoises. Sterile swab specimens from 40 tortoises with abscesses were analyzed using the Analytical Profile Index (API) system. Sixty-five bacteria species were identified covering facultative anaerobic gram-negative (n = 30, 46.2%), facultative anaerobic gram-positive (n = 19, 29.2%), and aerobic gram-negative bacteria (n = 16, 24.6%). The antibiotic sensitivity of these bacteria to 30 antibiotics was assessed using the Kirby-Bauer disk-diffusion method. Greater than 80% anaerobic gram-negative bacterial species showed sensitivity to amikacin and ceftazidime. Greater than 80% anaerobic gram-positive bacterial species were sensitive to amoxicillin, ampicillin, carbenicillin, and penicillin. In addition, more than 80% aerobic gram-negative bacterial species were sensitive to ceftazidime, colistin sulphate, amikacin, gentamicin, kanamycin, polymyxin B, and tobramycin. This study provides clinicians significant information for initial antibiotic options, which could elevate the abscess therapy success rate and improve the life quality of tortoises.

Treatment for parotid abscess: a systematic review

A parotid abscess is a dangerous complication of parotitis. In this study, we aimed to define current treatment concepts for parotid abscess, focusing on different management options. The authors performed a PRISMA-compliant systematic review across multiple databases including all original studies published until January 2021 focusing on treatment of parotid abscess. Studies specifying treatment modalities and treatment success rates were included based on abstract and full-text selection. The authors assessed study quality, demographics, success rates, management modalities and adverse events. Among 1,318 citations, 18 studies met our inclusion criteria. Twelve studies relied only on incision and drainage with antibiotic therapy; the remaining 6 compared different treatment modalities (incision and drainage versus exclusive medical therapy or ultrasound-guided drainage). Heterogeneity between studies precluded meta-analysis of data. The review showed that antibiotics remain the mainstay of treatment for parotid abscess. Conversely, the role of incision and drainage, and aspiration should be studied further. The higher rate of complications following incision and drainage suggests a more conservative approach is needed. Incision and drainage remain the main salvage option for conservative treatment failures.

The Evidence for a Causal Link Between Disease and Damaging Behavior in Pigs

Damaging behaviors (DB) such as tail and ear biting are prevalent in pig production and reduce welfare and performance. Anecdotal reports suggest that health challenges increase the risk of tail-biting. The prevalence of tail damage and health problems show high correlations across batches within and between farms. There are many common risk factors for tail-biting and health problems, notably respiratory, enteric and locomotory diseases. These include suboptimal thermal climate, hygiene, stocking density and feed quality. The prevalence of tail damage and health problems also show high correlations across batches within and between farms. However, limited evidence supports two likely causal mechanisms for a direct link between DB and health problems. The first is that generalized poor health (e.g., enzootic pneumonia) on farm poses an increased risk of pigs performing DB. Recent studies indicate a possible causal link between an experimental inflammation and an increase in DB, and suggest a link between cytokines and tail-biting. The negative effects of poor health on the ingestion and processing of nutrients means that immune-stimulated pigs may develop specific nutrient deficiencies, increasing DB. The second causal mechanism involves tail-biting causing poor health. Indirectly, pathogens enter the body via the tail lesion and once infected, systemic spread of infection may occur. This occurs mainly via the venous route targeting the lungs, and to a lesser extent via cerebrospinal fluid and the lymphatic system. In carcasses with tail lesions, there is an increase in lung lesions, abscessation, arthritis and osteomyelitis. There is also evidence for the direct spread of pathogens between biters and victims. In summary, the literature supports the association between poor health and DB, particularly tail-biting. However, there is insufficient evidence to confirm causality in either direction. Nevertheless, the limited evidence is compelling enough to suggest that improvements to management and housing to enhance pig health will reduce DB. In the same way, improvements to housing and management designed to address DB, are likely to result in benefits to pig health. While most of the available literature relates to tail-biting, we suggest that similar mechanisms are responsible for links between health and other DB.

Collateral Sensitivity Interactions between Antibiotics Depend on Local Abiotic Conditions

Mutations conferring resistance to one antibiotic can increase (cross-resistance) or decrease (collateral sensitivity) resistance to others. Antibiotic combinations displaying collateral sensitivity could be used in treatments that slow resistance evolution. However, lab-to-clinic translation requires understanding whether collateral effects are robust across different environmental conditions. Here, we isolated and characterized resistant mutants of Escherichia coli using five antibiotics, before measuring collateral effects on resistance to other paired antibiotics. During both isolation and phenotyping, we varied conditions in ways relevant in nature (pH, temperature, and bile). This revealed that local abiotic conditions modified expression of resistance against both the antibiotic used during isolation and other antibiotics. Consequently, local conditions influenced collateral sensitivity in two ways: by favoring different sets of mutants (with different collateral sensitivities) and by modifying expression of collateral effects for individual mutants. These results place collateral sensitivity in the context of environmental variation, with important implications for translation to real-world applications. IMPORTANCE When bacteria become resistant to an antibiotic, the genetic changes involved sometimes increase (cross-resistance) or decrease (collateral sensitivity) their resistance to other antibiotics. Antibiotic combinations showing repeatable collateral sensitivity could be used in treatment to slow resistance evolution. However, collateral sensitivity interactions may depend on the local environmental conditions that bacteria experience, potentially reducing repeatability and clinical application. Here, we show that variation in local conditions (pH, temperature, and bile salts) can influence collateral sensitivity in two ways: by favoring different sets of mutants during bacterial resistance evolution (with different collateral sensitivities to other antibiotics) and by modifying expression of collateral effects for individual mutants. This suggests that translation from the lab to the clinic of new approaches exploiting collateral sensitivity will be influenced by local abiotic conditions.

Case of infant invasive Streptococcus intermedius infection suggesting the need for anaerobic cultures

We report the case of an immunocompetent 6-month-old boy with a lung abscess and empyema caused by Streptococcus intermedius detected only from anaerobic cultures. Invasive S. intermedius infection in infants is rare. S. intermedius has been infrequently reported as a causative microorganism of lung abscess and empyema as most of the S. intermedius infections in children have been head and neck infections. While anaerobic cultures are often not performed for infant patients, we suggest the need for these cultures, including blood cultures, especially in cases of pediatric empyema, brain abscess, and liver abscess, which can be caused by S. intermedius.

Clinical Outcome of Transcervical Infusion of a Combination of Procaine Penicillin and Gentamicin in Late-term Pregnant Mares

Transcervical intrauterine infusion of antibiotics may more effectively treat pathogens associated with fetal and neonatal disease in pregnant mares than standard systemic routes. The objective of this study was to assess the safety of transcervical antibiotic infusion by characterizing the gestational outcome in nine healthy pregnant pony mares following a single transcervical infusion of 2.4 million IU of procaine penicillin and 200 mg of gentamicin in a 10 mL volume during late gestation. Assessment of fetal-placental health was performed through serial measurement of the combined thickness of the uterus and placenta (CTUP) and fetal heart rate and mares and foals were closely monitored in the periparturient period. Fetal heart rate and CTUP remained unchanged after infusion, with no evidence of fluid accumulation or significant increase at the time-points 24, 48, and 72 hours. All mares foaled without complication 12-58 days after antibiotic infusion at a mean gestational age of 322.7 ± 12.7 days. Two out of nine foals displayed signs of mild neonatal maladjustment syndrome that responded to minimal supportive care and all foals survived to weaning without further complications.

Molecular reprogramming and phenotype switching in Staphylococcus aureus lead to high antibiotic persistence and affect therapy success

Staphylococcus aureus causes invasive infections and easily acquires antibiotic resistance. Even antibiotic-susceptible S. aureus can survive antibiotic therapy and persist, requiring prolonged treatment and surgical interventions. These so-called persisters display an arrested-growth phenotype, tolerate high antibiotic concentrations, and are associated with chronic and recurrent infections. To characterize these persisters, we assessed S. aureus recovered directly from a patient suffering from a persistent infection. We show that host-mediated stress, including acidic pH, abscess environment, and antibiotic exposure promoted persister formation in vitro and in vivo. Multiomics analysis identified molecular changes in S. aureus in response to acid stress leading to an overall virulent population. However, further analysis of a persister-enriched population revealed major molecular reprogramming in persisters, including down-regulation of virulence and cell division and up-regulation of ribosomal proteins, nucleotide-, and amino acid-metabolic pathways, suggesting their requirement to fuel and maintain the persister phenotype and highlighting that persisters are not completely metabolically inactive. Additionally, decreased aconitase activity and ATP levels and accumulation of insoluble proteins involved in transcription, translation, and energy production correlated with persistence in S. aureus, underpinning the molecular mechanisms that drive the persister phenotype. Upon regrowth, these persisters regained their virulence potential and metabolically active phenotype, including reduction of insoluble proteins, exhibiting a reversible state, crucial for recurrent infections. We further show that a targeted antipersister combination therapy using retinoid derivatives and antibiotics significantly reduced lag-phase heterogeneity and persisters in a murine infection model. Our results provide molecular insights into persisters and help explain why persistent S. aureus infections are so difficult to treat.

Antimicrobial Treatment and Prophylaxis of Plague: Recommendations for Naturally Acquired Infections and Bioterrorism Response

This report provides CDC recommendations to U.S. health care providers regarding treatment, pre-exposure prophylaxis, and postexposure prophylaxis of plague. Yersinia pestis, the bacterium that causes plague, leads to naturally occurring disease in the United States and other regions worldwide and is recognized as a potential bioterrorism weapon. A bioweapon attack with Y. pestis could potentially infect thousands, requiring rapid and informed decision making by clinicians and public health agencies. The U.S. government stockpiles a variety of medical countermeasures to mitigate the effects of a bioterrorism attack (e.g., antimicrobials, antitoxins, and vaccines) for which the 21st Century Cures Act mandates the development of evidence-based guidelines on appropriate use. Guidelines for treatment and postexposure prophylaxis of plague were published in 2000 by a nongovernmental work group; since then, new human clinical data, animal study data, and U.S. Food and Drug Administration approvals of additional countermeasures have become available. To develop a comprehensive set of updated guidelines, CDC conducted a series of systematic literature reviews on human treatment of plague and other relevant topics to collect a broad evidence base for the recommendations in this report. Evidence from CDC reviews and additional sources were presented to subject matter experts during a series of forums. CDC considered individual expert input while developing these guidelines, which provide recommended best practices for treatment and prophylaxis of human plague for both naturally occurring disease and following a bioterrorism attack. The guidelines do not include information on diagnostic testing, triage decisions, or logistics involved in dispensing medical countermeasures. Clinicians and public health officials can use these guidelines to prepare their organizations, hospitals, and communities to respond to a plague mass-casualty event and as a guide for treating patients affected by plague.

Pharmacokinetics and pharmacodynamics of doxycycline in a Streptococcusequi subsp. zooepidemicus infection model in horses

The objectives of this study were to investigate the pharmacokinetics (PK), pharmacodynamics (PD), and the efficacy of oral administration of doxycycline (DXC) in horses with Streptococcus zooepidemicus tissue infections. Tissue chambers (TC) were implanted subcutaneously in the cervical region of 7 horses and inoculated with a single S. zooepidemicus isolate with a minimum inhibitory concentration (MIC) of 0.25 µg/ml, determined by agar dilution. Doxycycline hyclate (10 mg/kg, orally, q 12 h, for 5 days) mixed with poloxamer gel was started following inoculation. The TC fluid was sampled prior to and following inoculation for cytology analysis, quantitative culture, and DXC determination. Plasma DXC concentrations were measured over 48 h following the last dose of DXC administered. The mean plasma peak concentration (C_max ) of DXC was 0.32 µg/ml, and concentrations above the MIC were only reached in 3 TC samples. In plasma, mean T > MIC was 2.4 h, mean C_max /MIC was 1.30, and mean AUC_last /MIC was 11.63 h. These PK/PD indices did not reach the suggested targets for DXC treatments of infections, and the TC abscessed in all horses. This is the first study to evaluate the recommended dose of DXC in horse in an infection model.

Salmonella Renal Abscess in an Immunocompetent Child: Case Report and Literature Review

We describe a case of a 10-year-old immunocompetent girl with a left renal abscess due to Group C Salmonella (Salmonella serovar Oranienburg). Percutaneous drainage of the abscess was done. She also received 2 weeks of intravenous ceftriaxone, followed by 4 weeks of oral co-trimoxazole with resolution seen on ultrasound. A review of pediatric Salmonella renal abscesses is also presented.

RegAB Homolog of Burkholderia pseudomallei is the Master Regulator of Redox Control and involved in Virulence

Burkholderia pseudomallei, the etiological agent of melioidosis in humans and animals, often occupies environmental niches and infection sites characterized by limited concentrations of oxygen. Versatile genomic features enable this pathogen to maintain its physiology and virulence under hypoxia, but the crucial regulatory networks employed to switch from oxygen dependent respiration to alternative terminal electron acceptors (TEA) like nitrate, remains poorly understood. Here, we combined a Tn5 transposon mutagenesis screen and an anaerobic growth screen to identify a two-component signal transduction system with homology to RegAB. We show that RegAB is not only essential for anaerobic growth, but also for full virulence in cell lines and a mouse infection model. Further investigations of the RegAB regulon, using a global transcriptomic approach, identified 20 additional regulators under transcriptional control of RegAB, indicating a superordinate role of RegAB in the B. pseudomallei anaerobiosis regulatory network. Of the 20 identified regulators, NarX/L and a FNR homolog were selected for further analyses and a role in adaptation to anaerobic conditions was demonstrated. Growth experiments identified nitrate and intermediates of the denitrification process as the likely signal activateing RegAB, NarX/L, and probably of the downstream regulators Dnr or NsrR homologs. While deletions of individual genes involved in the denitrification process demonstrated their important role in anaerobic fitness, they showed no effect on virulence. This further highlights the central role of RegAB as the master regulator of anaerobic metabolism in B. pseudomallei and that the complete RegAB-mediated response is required to achieve full virulence. In summary, our analysis of the RegAB-dependent modulon and its interconnected regulons revealed a key role for RegAB of B. pseudomallei in the coordination of the response to hypoxic conditions and virulence, in the environment and the host.

An Unusual Presentation of Pyelonephritis: Is It COVID-19 Related?

In severe cases of COVID-19, late complications such as coagulopathy and organ injury are increasingly described. In milder cases of the disease, the exact time frame and causal path of late-onset complications have not yet been determined. Although direct and indirect renal injury by SARS-CoV-2 has been confirmed, hemorrhagic renal infection or coagulative problems in the urinary tract have not yet been described. This case report describes a 35-year-old female without relevant medical history who, five days after having recovered from infection with SARS-CoV-2, had an unusual course of acute pyelonephritis of the right kidney and persistent fever under targeted antibiotic treatment. A hemorrhagic ureteral obstruction and severe swollen renal parenchyma preceded the onset of fever and was related to the developing pyelonephritis. Sudden thrombotic venous occlusion in the right eye appeared during admission. Symmetrical paresthesia in the limbs in combination with severe lower back pain and gastro-intestinal complaints also occurred and remained unexplained despite thorough investigation. We present the unusual combination of culture-confirmed bacterial hemorrhagic pyelonephritis with a blood clot in the proximal right ureter, complicated by retinal vein thrombosis, in a patient who had recovered from SARS-CoV-2-infection five days before presentation. The case is suspect of a COVID-19-related etiology.

Activation of Neutrophil Granulocytes by Platelet-Activating Factor Is Impaired During Experimental Sepsis

Platelet-activating factor (PAF) is an important mediator of the systemic inflammatory response. In the case of sepsis, proper activation and function of neutrophils as the first line of cellular defense are based on a well-balanced physiological response. However, little is known about the role of PAF in cellular changes of neutrophils during sepsis. Therefore, this study investigates the reaction patterns of neutrophils induced by PAF with a focus on membrane potential (MP), intracellular pH, and cellular swelling under physiological and pathophysiological conditions and hypothesizes that the PAF-mediated response of granulocytes is altered during sepsis. The cellular response of granulocytes including MP, intracellular pH, cellular swelling, and other activation markers were analyzed by multiparametric flow cytometry. In addition, the chemotactic activity and the formation of platelet-neutrophil complexes after exposure to PAF were investigated. The changes of the (electro-)physiological response features were translationally verified in a human ex vivo whole blood model of endotoxemia as well as during polymicrobial porcine sepsis. In neutrophils from healthy human donors, PAF elicited a rapid depolarization, an intracellular alkalization, and an increase in cell size in a time- and dose-dependent manner. Mechanistically, the alkalization was dependent on sodium-proton exchanger 1 (NHE1) activity, while the change in cellular shape was sodium flux- but only partially NHE1-dependent. In a pathophysiological altered environment, the PAF-induced response of neutrophils was modulated. Acidifying the extracellular pH in vitro enhanced PAF-mediated depolarization, whereas the increases in cell size and intracellular pH were largely unaffected. Ex vivo exposure of human whole blood to lipopolysaccharide diminished the PAF-induced intracellular alkalization and the change in neutrophil size. During experimental porcine sepsis, depolarization of the MP was significantly impaired. Additionally, there was a trend for increased cellular swelling, whereas intracellular alkalization remained stable. Overall, an impaired (electro-)physiological response of neutrophils to PAF stimulation represents a cellular hallmark of those cells challenged during systemic inflammation. Furthermore, this altered response may be indicative of and causative for the development of neutrophil dysfunction during sepsis.

Advanced finger infection: more frequent than expected and mostly iatrogenic

Some patients present at an advanced stage of their fingertip infection with an extension of the infection in anatomical spaces or into fragile structures. One hundred and twenty-five patients have been operated on for a finger infection. Forty-one patients (33%) have been treated at the "complication" stage, while 84 cases (67%) were considered "non-complicated". The delay between initial injury and the surgical treatment was 12 days in the "non-complicated" group versus 30 in the "complication" group (p < 0.001). Osteitis (39% of the complications), and flexor sheath infection (37%) were the most frequent complications. Prescribing preoperative antibiotics increases the risk of being in the "complicated" group at p = 0.09. One hundred and thirteen patients (90.4%) were cured of their infection after a single operation. Neither the cause of infection, nor the type of germ or associated diabetes increased the risk of complication in our series. A better education of the first interveners (general practitioner or emergency doctor) in hand infection care could reduce the rate of complication allowing a faster access to hand surgeons.

When antibiotics fail: a clinical and microbiological perspective on antibiotic tolerance and persistence of Staphylococcus aureus

Staphylococcus aureus is a major human pathogen causing a vast array of infections with significant mortality. Its versatile physiology enables it to adapt to various environments. Specific physiological changes are thought to underlie the frequent failure of antimicrobial therapy despite susceptibility in standard microbiological assays. Bacteria capable of surviving high antibiotic concentrations despite having a genetically susceptible background are described as 'antibiotic tolerant'. In this review, we put current knowledge on environmental triggers and molecular mechanisms of increased antibiotic survival of S. aureus into its clinical context. We discuss animal and clinical evidence of its significance and outline strategies to overcome infections with antibiotic-tolerant S. aureus.

Reasons for antimicrobial treatment failures and predictive value of in-vitro susceptibility testing in veterinary practice: An overview

The choice of the most suitable antimicrobial agent for the treatment of an animal suffering from a bacterial infection is a complex issue. The results of bacteriological diagnostics and the in-vitro antimicrobial susceptibility testing (AST) provide guidance of potentially suitable antimicrobials. However, harmonized AST methods, veterinary-specific interpretive criteria and quality control ranges, which are essential to conduct AST in-vitro and to evaluate the corresponding results lege artis, are not available for all antimicrobial compounds, bacterial pathogens, animal species and sites of infection of veterinary relevance. Moreover, the clinical benefit of an antimicrobial agent (defined as its in vivo efficacy) is not exclusively dependent on the in-vitro susceptibility of the target pathogen. Apart from the right choice of an antibacterial drug with suitable pharmacokinetic properties and an appropriate pharmaceutical formulation, the success of treatment depends substantially on its adequate use. Even if this is ensured and in-vitro susceptibility confirmed, an insufficient improvement of clinical signs might be caused by biofilm-forming bacteria, persisters, or specific physicochemical conditions at the site of infection, such as pH value, oxygen partial pressure and perfusion rate. This review summarizes relevant aspects that have an impact on the predictive value of in-vitro AST and points out factors, potentially leading to an ineffective outcome of antibacterial treatment in veterinary practice. Knowing the reasons of inadequate beneficial effects can help to understand possible discrepancies between in-vitro susceptibility and in vivo efficacy and aid in undertaking strategies for an avoidance of treatment failures.

Purulent infectious myositis (formerly tropical pyomyositis)

Purulent infectious myositis (PIM), formerly known as tropical pyomyositis, is a pyogenic infection of skeletal muscles. Staphylococcus aureus, a normal human skin inhabitant, is the main pathogen involved, but multiple other microorganisms have been implicated. Although usually a progressive febrile disease with pain in the affected muscle(s), severe, life-threatening forms have been described, especially in immunosuppressed patients and children. PIM may elude early diagnosis given the lack of overlying skin changes. Hence, high index of suspicion followed by imaging modalities (ultrasonography when superficial and computed tomography or magnetic resonance imaging with contrast when deep) help confirm the diagnosis. Treatment requires combination of percutaneous or open surgical drainage along with antimicrobial therapy guided by culture results. The rising incidence of cases due to methicillin-resistant Staphylococcus aureus (MRSA) strains, makes the inclusion of vancomycin be recommended. This paper reviews PIM highlighting its global distribution, causative agents, predisposing factors, management, and potential complications.

Indication for an additional postoperative antibiotic treatment after surgical incision of serious odontogenic abscesses

INTRODUCTION

Serious abscesses of an odontogenic origin occur frequently in the oral and maxillofacial surgery departments. Rapid surgical incision and drainage constitutes the most important therapeutic action. However, additional surgical therapy and supplementary administration of antibiotics is often carried out, such that the efficiency of this supplementary therapeutic option has been questioned.

METHODS

All patients with severe odontogenic infections who received surgical treatment under general anaesthesia were recruited to this retrospective study. We determined whether they received additional antibiotic therapy on the ward and if it was possible to improve therapeutic outcomes using this option.

RESULTS

A total of 258 patients with a severe odontogenic infection between January 2008 and August 2014 were included. The most frequent infection observed was a submandibular abscess (56%), followed by a perimandibular abscess (18%) and a submental abscess (9%). About 65% of the patients were treated with antibiotics in addition to surgery. The median CRP level prior to surgical treatment was 87.8 mg/l (Q₁: 40.3 mg/l; Q₃: 143.5 mg/l) in patients who were administered an additional antibiotic and 83.8 mg/l (Q₁: 37.3 mg/l; Q₃: 135.0 mg/l) in those who received no antibiotic treatment after surgery. The postoperative median CRP levels were 116.5 mg/l (Q₁: 52.1 mg/l; Q₃: 159.3 mg/l) and 106.5 mg/l (Q₁: 40.6 mg/l; Q₃: 152.6 mg/l), respectively. Neither the preoperative CRP level (p = 0.546) nor the postoperative CRP level (p = 0.450) differed significantly between the groups. But patients who received additional antibiotic therapy had a significantly longer hospital stay (median: 6 days; range: 1-22 days) than patients who had no additional antibiotic therapy (median: 4 days; range: 1-19 days) (p = 0.002).

CONCLUSIONS

This study did not show an improvement in the therapeutic outcome with administration of supplementary antibiotics in addition to surgery. Thus, surgically incising an abscess is the most important therapeutic action and administration of antibiotics must be critically scrutinised.

Antibiotic instillation for a chronic lung abscess

Introduction

Antibiotic treatment of lung abscesses fails in 10-20% of cases and require surgery, however, some are unsuitable for resection. Alternative options carry significant morbidity.

Case report

A 47 year old man with inoperable non-small cell lung cancer developed a lung abscess following definitive radiotherapy. Initial antibiotic therapy was successful, however four years later his symptoms recurred. Despite multiple courses his symptoms recurred despite long-term antibiotics. Immediately following a diagnostic aspiration, ceftriaxone and metronidazole were instilled into the abscess with subsequent clinical and radiological resolution.

Discussion

Lung abscesses are an uncommon complication of radiotherapy. Antibiotic therapy can fail for a number of reasons. Although instillation of antibiotics has not been described in the management of lung abscesses, the direct application of antifungals for aspergillomas is well documented and case series report success in other abscess sites.

Conclusion

Direct antibiotic instillation following lung abscess aspiration adds minimal risk and is potentially curative.

Antimicrobial susceptibility of bacterial isolates from ambulatory practice and from a referral hospital

BACKGROUND

Responsible use of antimicrobials in equine practice relies on knowledge of common bacterial isolates and their antimicrobial sensitivities.

OBJECTIVES

To assess the frequency of bacterial resistance to a combination of parenteral penicillin and gentamicin and to trimethoprim and sulfamethoxazole for PO use in a selection of clinical isolates, and subsequently to determine the prevalence of resistance to antimicrobials that might then be used as alternatives to first-line antimicrobials for the same isolates.

METHODS

Retrospective analysis of minimal inhibitory concentrations (MICs) of antimicrobials for 6354 bacterial isolates from 365 ambulatory practices and 519 isolates from a referral hospital. The MICs were used to indicate sensitivity or resistance to commonly used antimicrobials and the prevalences of resistance were compared between origin of the isolates, and among antimicrobial drugs.

RESULTS

Isolates from the referral hospital were significantly (P < .05) more likely to be resistant to the antimicrobials tested than those derived from ambulatory practice. Overall, 91% of the ambulatory isolates and 64% of the hospital isolates were sensitive to penicillin-gentamicin. For trimethoprim-sulfamethoxazole combination, 82% of the ambulatory practice isolates and 56% of the referral hospital isolates were sensitive.

CONCLUSIONS AND CLINICAL IMPORTANCE

Most isolates were sensitive to penicillin and gentamicin as well as trimethoprim-sulfamethoxazole. No predictable efficacious second choice antimicrobial was identified for those isolates resistant to the first-line antimicrobials. The likelihood of isolates being sensitive to second choice antimicrobials was variable but generally higher for ambulatory isolates compared to referral isolates. Bacterial identification and measurement of MIC are essential to make the appropriate antimicrobial choice.

From Petri Dish to Patient: Bioavailability Estimation and Mechanism of Action for Antimicrobial and Immunomodulatory Natural Products

The new era of multidrug resistance of pathogens against frontline antibiotics has compromised the immense therapeutic gains of the 'golden age,' stimulating a resurgence in antimicrobial research focused on antimicrobial and immunomodulatory components of botanical, fungal or microbial origin. While much valuable information has been amassed on the potency of crude extracts and, indeed, purified compounds there are too many reports that uncritically extrapolate observed in vitro activity to presumed ingestive and/or topical therapeutic value, particularly in the discipline of ethnopharmacology. Thus, natural product researchers would benefit from a basic pharmacokinetic and pharmacodynamic understanding. Furthermore, therapeutic success of complex mixtures or single components derived therefrom is not always proportionate to their MIC values, since immunomodulation can be the dominant mechanism of action. Researchers often fail to acknowledge this, particularly when 'null' activity is observed. In this review we introduce the most up to date theories of oral and topical bioavailability including the metabolic processes affecting xenobiotic biotransformation before and after drugs reach the site of their action in the body. We briefly examine the common methodologies employed in antimicrobial, immunomodulatory and pharmacokinetic research. Importantly, we emphasize the contribution of synergies and/or antagonisms in complex mixtures as they affect absorptive processes in the body and sometimes potentiate activity. Strictly in the context of natural product research, it is important to acknowledge the potential for chemotypic variation within important medicinal plants. Furthermore, polar head space and rotatable bonds give a priori indications of the likelihood of bioavailability of active metabolites. Considering this and other relatively simple chemical insights, we hope to provide the basis for a more rigorous scientific assessment, enabling researchers to predict the likelihood that observed in vitro anti-infective activity will translate to in vivo outcomes in a therapeutic context. We give worked examples of tentative pharmacokinetic assessment of some well-known medicinal plants.

Role of Interventional Radiology in the Management of Infection

Interventional radiology (IR) is plays a crucial role in the management of localized infections, utilizing percutaneous access to loculated fluid collections for drainage and source control. Interventions have been developed in multiple organs and systems and used over decades, allowing the IR physician to provide patient care in many cases where surgical options are not optimal. In this review, we will examine the emergent, urgent, and routine nature of various IR procedures in the infectious context and timelines for each in regards to the decision making process. An algorithmic approach should guide the clinician's decision making for IR procedures in both large academic centers and smaller community hospitals. This approach and the pertinent procedural technique are described for multiple systems and organs including the biliary tree, gallbladder, genitourinary tract, and thoracic, abdominal, and pelvic abscesses. Increased awareness of the abilities and limitations of IR physicians in clinical scenarios needs to be implemented, to allow multispecialty input in efforts to decrease morbidity and mortality.

Infections of the Hepatobiliary System

Hepatobiliary infections account for a small but clinically important proportion of emergency department presentations. They present a clinical challenge due to the broad range of imaging characteristics on presentation. Recognition of complications is imperative to drive appropriate patient care and resource utilization to avoid diagnostic pitfalls and avert adverse patient outcomes. A thorough understanding of anatomy infectious pathology of hepatobiliary system is essential in the emergency setting to confidently diagnose and guide medical intervention. Many presentations of hepatobiliary infection have characteristic imaging features on individual imaging modalities with others requiring the assimilation of findings of multiple imaging modalities along with incorporating the clinical context and multispecialist consultation. Familiarity with the strengths of individual imaging modalities in the radiologists' arsenal is imperative to guide the appropriate utilization of resources, particularly in the emergent time sensitive setting. Accurate identification and diagnosis of hepatobiliary infections is vital for appropriate patient care and management stratification.

Transition to Oral versus Continued Intravenous Antibiotics for Patients with Pyogenic Liver Abscesses: A Retrospective Analysis

INTRODUCTION

The management of pyogenic liver abscesses usually requires 4 weeks of antibiotic therapy. It is unknown if oral (PO) antibiotics are as effective as intravenous (IV) antibiotics for this indication.

OBJECTIVES

To compare 30-, 60-, and 90-day readmission rates between patients with pyogenic liver abscesses receiving IV antibiotics for the duration of therapy and those who were transitioned to PO antibiotics after discharge from the hospital.

METHODS

This retrospective study included patients with pyogenic liver abscesses who had undergone percutaneous drainage and received IV antibiotics while in the hospital. Patients were grouped based on receipt of either PO or IV antibiotics at discharge.

RESULTS

The final cohort resulted in 99 patients, 48 in the PO group and 51 in the IV group. The most common organisms identified were Klebsiella sp, Escherichia coli, and Streptococcus sp. The most common antibiotic received at discharge in the IV group was ertapenem or ceftriaxone plus metronidazole. Patients in the PO group most commonly received levofloxacin plus metronidazole at discharge. Thirty-day readmission occurred more frequently in the PO group (PO 39.6% vs IV 17.6%, p=0.03). The most common reasons for readmission were complications related to abscess or antibiotic. Univariate logistic regression for readmission identified PO antibiotics at discharge as an independent predictor of readmission at 30 days (odds ratio [OR] 3.1), 60 days (OR 3.9), and 90 days (OR 3.1).

CONCLUSION

Transition to PO antibiotics that consisted mostly of fluoroquinolones for patients with pyogenic liver abscesses was associated with a higher rate of 30-day readmission compared with patients treated with IV antibiotics that consisted mostly of β-lactams.

Antimicrobial Activity of Ceftiofur and Penicillin With Gentamicin Against Escherichia coli and Streptococcus equi Subspecies zooepidemicus in an Ex Vivo Model of Equine Postpartum Uterine Disease

The use of antimicrobials for the management of equine uterine disease is commonplace, with antibiotic selection generally based on empirical evidence or in vitro sensitivity results. However, the potential disconnect between these laboratory results and clinical efficacy in the mare raises concern for antibiotic failure and subsequent development of resistant organisms. In this work, we attempt to bridge this gap by using an ex vivo model of the equine postpartum uterus to quantitatively evaluate the antimicrobial activity of two commonly used antibiotic treatments in the mare (ceftiofur and penicillin with gentamicin). The activity of both of these treatments was evaluated in two different fluid environments (standard bacterial culture broth and equine postpartum uterine fluid) against clinical isolates of E. coli and S. zooepidemicus. Although treatment with ceftiofur was effective at reducing growth of S. zooepidemicus in equine postpartum uterine fluid, it did not reduce bacterial growth of E. coli. Treatment with procaine penicillin G with gentamicin achieved at least bacteriostatic activity against E. coli in both fluid types, and bactericidal activity against S. zooepidemicus in both fluid types. The intrauterine infusion of procaine penicillin G with gentamicin in cases of postpartum uterine disease caused by E. coli or S. zooepidemicus is supported by the results of this work.

Efficacy of Non-Beta-lactam Antibiotics for Prevention of Cesarean Delivery Surgical Site Infections

Objective  To examine the association between perioperative Beta ( β ))-lactam versus non- β -lactam antibiotics and cesarean delivery surgical site infection (SSI). Study Design  Retrospective cohort of women undergoing cesarean delivery from January 1 to December 31, 2014. All women undergoing cesarean after 34 weeks with a postpartum visit were included. Prevalence of SSI was compared between women receiving β -lactam versus non- β -lactam antibiotics. Bivariate analyses were performed using Pearson's Chi-square, Fisher's exact, or Wilcoxon's rank-sum tests. Logistic regression models were fit controlling for possible confounders. Results  Of the 929 women included, 826 (89%) received β -lactam prophylaxis and 103 (11%) received a non- β -lactam. Among the 893 women who reported a non-type I (low risk) allergy, 819 (92%) received β -lactam prophylaxis. SSI occurred in 7% of women who received β -lactam antibiotics versus 15% of women who received a non- β -lactam ( p  = 0.004). β -Lactam prophylaxis was associated with lower odds of SSI compared with non- β -lactam antibiotics (odds ratio [OR] = 0.43; 95% confidence interval [CI] = 0.22-0.83; p  = 0.01) after controlling for chorioamnionitis in labor, postlabor cesarean, endometritis, tobacco use, and body mass index (BMI). Conclusion   β -Lactam perioperative prophylaxis is associated with lower odds of a cesarean delivery surgical site infection compared with non- β -lactam antibiotics.

The Concept of an Ideal Antibiotic: Implications for Drug Design

The emergence and spread of antibiotic-resistant pathogens is a major public health issue, which requires global action of an intersectoral nature. Multidrug-resistant (MDR) pathogens-especially "ESKAPE" bacteria-can withstand lethal doses of antibiotics with various chemical structures and mechanisms of action. Pharmaceutical companies are increasingly turning away from participating in the development of new antibiotics, due to the regulatory environment and the financial risks. There is an urgent need for innovation in antibiotic research, as classical discovery platforms (e.g., mining soil Streptomycetes) are no longer viable options. In addition to discovery platforms, a concept of an ideal antibiotic should be postulated, to act as a blueprint for future drugs, and to aid researchers, pharmaceutical companies, and relevant stakeholders in selecting lead compounds. Based on 150 references, the aim of this review is to summarize current advances regarding the challenges of antibiotic drug discovery and the specific attributes of an ideal antibacterial drug (a prodrug or generally reactive compound with no specific target, broad-spectrum antibacterial activity, adequate penetration through the Gram-negative cell wall, activity in biofilms and in hard-to-treat infections, accumulation in macrophages, availability for oral administration, and for use in sensitive patient groups).

New sequence type ST3756 of Staphylococcus aureus subspecies anaerobius as the causative agent of abscessing lymphadenitis in sheep

Morel's disease is a form of abscessing lymphadenitis of sheep and goats caused by Staphylococcus aureus subspecies anaerobius. In Europe and Africa, the disease is linked to S. aureus of multilocus sequence type 1464. In an outbreak recorded in 2015 in a flock of 530 animals in the district of Nymburk, Czech Republic, Europe, the causative agent was cultured and subsequently confirmed by Maldi-TOF. Neither antibiotic therapy nor surgical interventions met any success, although the strain isolated was found to be sensitive to antibiotics used. Vaccination and revaccination with inactivated autogenous vaccine administered subcutaneously was relatively successful. Subsequent multilocus sequence typing revealed the presence of new S. aureus sequence type 3756, different from 1464 in three out of seven genes typed. The isolate thus represents a new sequence type of Staphylococcus aureus ssp. anaerobius which should be considered as a causative agent of Morel's disease.

Prolonged bacterial lag time results in small colony variants that represent a sub-population of persisters

Persisters are a subpopulation of bacteria that are not killed by antibiotics even though they lack genetic resistance. Here we provide evidence that persisters can manifest as small colony variants (SCVs) in clinical infections. We analyze growth kinetics of Staphylococcus aureus sampled from in vivo conditions and in vitro stress conditions that mimic growth in host compartments. We report that SCVs arise as a result of a long lag time, and that this phenotype emerges de novo during the growth phase in various stress conditions including abscesses and acidic media. We further observe that long lag time correlates with antibiotic usage. These observations suggest that treatment strategies should be carefully tailored to address bacterial persisters in clinics.

Persisters are bacterial subpopulations that are not killed by antibiotics even though they lack genetic resistance. Here, the authors show that persisters can manifest as small colony variants in clinical infections, and arise as a result of a long lag time in stress conditions including antibiotic exposure.

Evaluation of local instillation of antibiotics in infected walled-off pancreatic necrosis

BACKGROUND

Infected walled-off pancreatic necrosis (WON) is associated with increased morbidity and mortality. Systemic antibiotics are the main treatment, but are associated with adverse reactions and risk of superinfections. This study evaluates the efficacy of local instillation of antibiotics into WON.

METHODS

We performed a retrospective cohort study of all consecutive patients with infected WON, who were treated with endoscopic transmural drainage and necrosectomy (ETDN) at a tertiary referral hospital between 2012 and 2016. A total of 91 patients were included. Patients often received concomitant intravenous and local antibiotics. Local antibiotics were added to the irrigation fluid depending on microbiological findings. A beneficial response was defined as the eradication of a microbe on subsequent culturing. Univariable and multivariable logistic regression analyses were used to evaluate antimicrobial efficacy.

RESULTS

At the first drainage 81 (86%) patients had infected and 10 sterile WON. Among patients with bacterial infections, neither local nor systemic antibiotics were associated with the eradication of microbes between first and second culture. Between the second and third culture, the use of local antibiotics was associated with the eradication of microbes (OR, 2.54; 95% CI, 1.25-5.18; p = 0.01), but not systemic antibiotics (OR, 0.75; 95% CI, 0.38-1.38; p = 0.33). Twelve patients had fungal infections treated with local amphotericin B between first and second culture. The fungus was eradicated in all 12 patients.

CONCLUSION

Local instillation of antibiotics may be a promising supplement to systemic administration.

Drug permeation and metabolism in Mycobacterium tuberculosis: Prioritising local exposure as essential criterion in new TB drug development

Anti-tuberculosis (TB) drugs possess diverse abilities to penetrate the different host tissues and cell types in which infecting Mycobacterium tuberculosis bacilli are located during active disease. This is important since there is increasing evidence that the respective "lesion-penetrating" properties of the front-line TB drugs appear to correlate well with their specific activity in standard combination therapy. In turn, these observations suggest that rational efforts to discover novel treatment-shortening drugs and drug combinations should incorporate knowledge about the comparative abilities of both existing and experimental anti-TB agents to access bacilli in defined physiological states at different sites of infection, as well as avoid elimination by efflux or inactivation by host or bacterial metabolism. However, while there is a fundamental requirement to understand the mode of action and pharmacological properties of any current or experimental anti-TB agent within the context of the obligate human host, this is complex and, until recently, has been severely limited by the available methodologies and models. Here, we discuss advances in analytical models and technologies which have enabled investigations of drug metabolism and pharmacokinetics (DMPK) for new TB drug development. In particular, we consider the potential to shift the focus of traditional pharmacokinetic-pharmacodynamic analyses away from plasma to a more specific "site of action" drug exposure as an essential criterion for drug development and the design of dosing strategies. Moreover, in summarising approaches to determine DMPK data for the "unit of infection" comprising host macrophage and intracellular bacillus, we evaluate the potential benefits of including these analyses at an early stage in the preclinical drug development algorithm. © 2018 IUBMB Life, 70(9):926-937, 2018.

Clinically applicable irreversible electroporation for eradication of micro-organisms

Irreversible electroporation (IRE) damages cell membranes and is used in medicine for nonthermal ablation of malignant tumours. Our aim was to evaluate the antimicrobial effect of IRE. The pathogenic micro-organisms, Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli, Pseudomonas aeruginosa and Candida albicans were subjected to IRE. Survival was measured as a function of voltage and the number of pulses applied. Combined use of IRE and oxacillin for eradication of Staph. aureus was also tested. Log10 reduction in micro-organisms positively correlated with the number of applied pulses. The colony count of Strep. pyogenes and E. coli declined by 3·38 and 3·05 orders of magnitude, respectively, using an electric field of 2000 V and 100 pulses. Killing of Staph. aureus and P. aeruginosa was achieved with a double cycle of IRE (2000, 1500 V and repeated 1250 V respectively) of 50-100 IRE pulses. The addition of subclinical inhibitory concentrations of oxacillin to the Staph. aureus suspension prior to IRE led to total bacterial death, demonstrating synergism between oxacillin and IRE. Our results demonstrate that using IRE with clinically established parameters has a marked in vitro effect on pathogenic micro-organisms and highlights the potential of IRE as a treatment modality for deep-seated infections, particularly when combined with low doses of antibiotics.

SIGNIFICANCE AND IMPACT OF THE STUDY

Irreversible electroporation (IRE) is utilized in interventional radiology to treat cancer patients. In this study we evaluated in vitro the antimicrobial effect of IRE. We demonstrated that using IRE with clinically established parameters has a marked effect on pathogenic micro-organisms and is synergistic to antimicrobials when both are combined. Our results point to the potential of IRE as a treatment modality for deep-seated infections.

Defining Host Responses during Systemic Bacterial Infection through Construction of a Murine Organ Proteome Atlas

Group A Streptococcus (GAS) remains one of the top 10 deadliest human pathogens worldwide despite its sensitivity to penicillin. Although the most common GAS infection is pharyngitis (strep throat), it also causes life-threatening systemic infections. A series of complex networks between host and pathogen drive invasive infections, which have not been comprehensively mapped. Attempting to map these interactions, we examined organ-level protein dynamics using a mouse model of systemic GAS infection. We quantified over 11,000 proteins, defining organ-specific markers for all analyzed tissues. From this analysis, an atlas of dynamically regulated proteins and pathways was constructed. Through statistical methods, we narrowed organ-specific markers of infection to 34 from the defined atlas. We show these markers are trackable in blood of infected mice, and a subset has been observed in plasma samples from GAS-infected clinical patients. This proteomics-based strategy provides insight into host defense responses, establishes potentially useful targets for therapeutic intervention, and presents biomarkers for determining affected organs during bacterial infection.

Nanoparticle-based local antimicrobial drug delivery

Despite the wide success of antibiotics in modern medicine, the treatment of bacterial infections still faces critical challenges, especially due to the rapid emergence of antibiotic resistance. As a result, local antimicrobial treatment aimed at enhancing drug concentration at the site of infection while avoiding systemic exposure is becoming increasingly attractive, as it may alleviate resistance development. Meanwhile, therapeutic nanoparticles, especially liposomes, polymeric nanoparticles, dendrimers, and inorganic nanoparticles, are gaining traction to improve the therapeutic efficacy with many applications specifically focused on local antimicrobial treatment. This review highlights topics where nanoparticle-based strategies hold significant potential to advance treatment against local bacterial infections, including (1) promoting antibiotic localization to the pathogen, (2) modulating drug-pathogen interaction against antibiotic resistance, and (3) enabling novel anti-virulence approaches for 'drug-free' antimicrobial activity. In each area, we highlight the innovative antimicrobial strategies tailored for local applications and review the progress made for the treatment of bacterial infections.

Suppurative Inflammation and Local Tissue Destruction Reduce the Penetration of Cefuroxime to Infected Bone Implant Cavities

Treatment of post-traumatic and implant-associated osteomyelitis (IAO) includes surgical debridement, removal of implants and long-term antibiotic therapy. The success of antibiotic therapy relies not only on activity towards the infecting pathogen, but also on sufficient penetration of the target site. The aim of the present study was to characterize the local pathological changes associated with reduced penetration of cefuroxime to infected bone implant cavities. Previously, reduced penetration of systemically administrated cefuroxime was demonstrated in the implant cavity of 10 pigs with Staphylococcus aureus IAO present for 5 days. In the present study, a comprehensive histopathological characterization of the peri-implant bone tissue was performed and correlated with the reduced penetration of cefuroxime. In two pigs, the levels of oxygen, pyruvate and lactate was estimated in the implant cavity. A peri-implant pathological bone area (PIBA) developed with a width of 1.2 up to 3.8 mm. PIBAs included: (1) suppuration, resulting in destruction of the implant cavity contour, and (2) a non-vascular zone of primarily necrotic bone tissue. A strong negative correlation was seen between PIBA width and cefuroxime area under the concentration time curves (AUC_[0-last]) and peak concentration of cefuroxime (C_max). All metabolic measurements demonstrated hypoxia. In conclusion, subacute suppurative bone inflammation with local tissue destruction can result in decreased penetration of antibiotics and insufficient oxygen supply.

Spinal Implants Can Be Inserted in Patients With Deep Spine Infection: Results From a Large Cohort Study

STUDY DESIGN

A retrospective, cohort study of 84 patients with deep spine infection managed at a major tertiary hospital over 14 years with a minimum follow up of 2 years.

OBJECTIVE

To determine the role of instrumentation in spines with deep infection.

SUMMARY OF BACKGROUND DATA

It is often believed that implants should not be inserted in patients with deep spine infection because of the risk of persistent or recurrent infection. However, there are often concerns about spinal stability and a paucity of evidence to guide clinical practice in this field.

METHODS

We compared the mortality, reoperation, and reinfection rates in patients with spine infection treated with antibiotics alone, antibiotics with debridement, and antibiotics with debridement and instrumentation. Significant outcome predictors were determined using multivariable logistic regression model.

RESULTS

Forty-nine males and 35 females with a mean age was 62.0 years had spine infection affecting the lumbar spine predominantly. The most common form of infection was osteomyelitis and spondylodiscitis (69.4%). Staphylococcus aureus was the most common causative organism (61.2%).There was no difference in terms of reoperation or relapse for patients treated with antibiotics alone, antibiotics with debridement, or antibiotics with debridement and instrumentation. However, compared with antibiotics alone, the crude inhospital mortality was lower for patients treated with instrumentation (odds ratio, OR, 0.82; P = 0.01), and antibiotics with debridement (OR 0.80; P = 0.02).

CONCLUSION

Spinal instrumentation in an infected spine is safe and not associated with higher reoperation or relapse rates. Mortality is lower for patients treated with instrumentation.

LEVEL OF EVIDENCE

3.

Magnetic nanoparticles as a drug delivery system that enhance fungicidal activity of polyene antibiotics

This study was designed to assess the antifungal/anti-biofilm and hemolytic properties of two polyene antibiotics, amphotericin B (AMF) and nystatin (NYS), attached to the surface of magnetic nanoparticles (MNP) against clinical isolates of Candida species and human red blood cells, respectively. The developed nanosystems, MNP@AMF and MNP@NYS, displayed stronger fungicidal activity than unbound AMF or NYS. Synergistic activity was observed with a combination of polyenes and MNPs against all tested Candida strains. Nanosystems were more potent than unbound agents when tested against Candida strains in the presence of pus, and as agents able to prevent Candida biofilm formation. The observed inactivation of catalase Cat1 in Candida cells upon treatment with the nanosystems suggests that disruption of the oxidation-reduction balance is a mechanism leading to inhibition of Candida growth. The significant decrease of polyenes lytic activity against host cells after their attachment to MNPs surface indicates improvement in their biocompatibility.

The Effects of Early Antibiotic Administration on Bacterial Culture Growth From Hand Abscesses

BACKGROUND

Traditional management of hand abscesses consists of withholding antibiotics prior to drainage to optimize bacterial culture growth and outcome. The purpose of this study was to determine the effect of preoperative empiric antibiotics on the rate of culture growth and rate of adverse events in patients with acute hand abscesses.

METHODS

We performed a retrospective review of prospectively collected data on 88 consecutive hand abscesses that received empiric antibiotics prior to incision and drainage from 2012 to 2013 at an urban academic institution. We analyzed patient demographics, bacteriology, culture growth results, time to surgery, and frequency of adverse events.

RESULTS

The overall rate of positive culture growth was 90% (n = 79) despite running the antibiotics for a mean of 31 hours prior to debridement. Furthermore, 96% of the isolates were given a susceptible antibiotic during that time. The mean number of debridements was 1.5 per patient, but 4 re-operations were necessary for wound complications. No patients required an amputation or were upgraded to intensive care.

CONCLUSIONS

Preoperative empiric antibiotic administration does not appear to greatly reduce bacterial culture growth from hand abscesses. The adverse events are relatively few for simple abscesses treated with pre-surgical antibiotics and decompression within 24 hours.

Theoretical approach to local infusion of antibiotics for infected pancreatic necrosis

BACKGROUND/OBJECTIVES

Infected pancreatic necrosis is a major complications of acute pancreatitis. If drainage is required, local administration of antibiotics through transmural nasocystic or percutaneous catheter may allow increasing local antibiotic concentrations. Drug diffusion becomes the main factor influencing local drug tissue penetration. The present study aims at providing the rationale for the design of new research protocols evaluating the efficacy of local antibiotics for infected pancreatic necrosis.

METHODS

A review of microbiological data was performed for the most common organisms causing the infection, antibiotics spectrum and minimum inhibitory concentrations (MIC). A search of the physico-chemical properties of antibiotics was performed to calculate the diffusion coefficients. An estimation of the antibiotic concentrations in pancreatic tissue was obtained using a mathematical model. Efficacy factors (EF) were calculated and the stability of the antibiotic solutions were evaluated to optimize the dosing regimen.

RESULTS

Piperacillin, vancomycin and metronidazole achieve high concentrations in the surrounding tissue very fast. Imipenem, ceftriaxone, ciprofloxacin, gentamicin, linezolid and cloxacillin achieve intermediate concentration values. Tigecycline, showed the lowest concentration values (<2 mg/L). Calculated EF is highest for piperacillin and imipenem short after administration and near to surface diffusion area (0.5 cm), but EF of imipenem is higher at deeper areas and longer time after administration.

CONCLUSIONS

Considering obtained results, some solutions are proposed using saline as diluent and 25 °C of temperature during administration. Imipenem has the best theoretical results in empiric local treatment. Linezolid and tigecycline solutions are not recommended.