Heme utilization by the enterococci

Heme consists of a tetrapyrrole ring ligating an iron ion and has important roles in biological systems. While well-known as the oxygen-binding molecule within hemoglobin of mammals, heme is also cofactor for several enzymes and a major iron source for bacteria within the host. The enterococci are a diverse group of Gram-positive bacteria that exist primarily within the gastrointestinal tract of animals. However, some species within this genus can transform into formidable opportunistic pathogens, largely owing to their extraordinary adaptability to hostile environments. Although enterococci cannot synthesize heme nor depend on heme to grow, several species within the genus encode proteins that utilize heme as a cofactor, which appears to increase their fitness and ability to thrive in challenging environments. This includes more efficient energy generation via aerobic respiration and protection from reactive oxygen species. Here, we review the significance of heme to enterococci, primarily the major human pathogen Enterococcus faecalis, use bioinformatics to assess the prevalence of hemoproteins throughout the genus, and highlight recent studies that underscore the central role of the heme-E. faecalis relationship in host-pathogen dynamics and interspecies bacterial interactions.

Polymicrobial Septic Peritonitis Caused by Enterococcus faecium and Enterococcus casseliflavus following Uterine Rupture in a Goat

A one-year-old female miniature goat was presented to an emergency service after calving a dead goatling. Physical and ultrasonographic examination revealed the presence of a viable fetus; therefore, the goat was submitted to an emergency cesarean section. In the postoperative period, the animal had septic peritonitis caused by Enterococcus faecium and Enterococcus casseliflavus. Both bacterial strains showed contrasting antimicrobial resistance profiles. Laparohysterectomy and abdominal cavity lavage were performed, but, once the animal had adhesions and necrotic lesions in abdominal organs, euthanasia was executed. A post-mortem examination revealed fibrino-necrotic septic peritonitis secondary to uterine rupture. To the authors' knowledge, this is the first detailed report of polymicrobial septic peritonitis in a miniature goat and the first report of septic peritonitis caused by E. faecium and E. casseliflavus.

Clinical Features and Genomic Epidemiology of Bloodstream Infections due to Enterococcal Species Other Than Enterococcus faecalis or E. faecium in Patients With Cancer

Background

Non-Enterococcus faecium, non-E. faecalis (NFF) enterococci are a heterogeneous group of clinically pathogenic enterococci that include species with intrinsic low-level vancomycin resistance. Patients with cancer are at increased risk for bacteremia with NFF enterococci, but their clinical and molecular epidemiology have not been extensively described.

Methods

We conducted a retrospective review of all patients (n = 70) with NFF bacteremia from 2016 to 2022 at a major cancer center. The main outcomes assessed were 30-day mortality, microbiological failure (positive blood cultures for ≥4 days), and recurrence of bacteremia (positive blood culture <14 days after clearance). Whole-genome sequencing was performed on all available NFF (n = 65).

Results

Patients with hematological malignancies made up 56% of the cohort (77% had leukemia). The majority of solid malignancies (87%) were gastrointestinal in origin. The majority of infections (83%) originated from an intra-abdominal source. The most common NFF species were E. gallinarum (50%) and E. casseliflavus (30%). Most (61%) patients received combination therapy. Bacteremia recurred in 4.3% of patients, there was a 30-day mortality of 23%, and 4.3% had microbiological failure. E. gallinarum and E. casseliflavus isolates were genetically diverse with no spatiotemporal clustering to suggest a single strain. Frequencies of ampicillin resistance (4.3%) and daptomycin resistance (1.9%) were low. Patients with hematologic malignancy had infections with NFF enterococci that harbored more resistance genes than patients with solid malignancy (P = .005).

Conclusions

NFF bacteremia is caused by a heterogeneous population of isolates and is associated with significant mortality. Hematological malignancy is an important risk factor for infection with NFF resistant to multiple antibiotics.

Prevalence and Molecular Characteristics of Enterococci Isolated from Clinical Bovine Mastitis Cases in Ningxia

Purpose

This study aimed to investigate the prevalence and genetic characterization of enterococcal isolates (Enterococcus faecalis, Enterococcus faecium and Enterococcus hirae) isolated from clinical bovine mastitis cases in Ningxia, China.

Patients and Methods

The enterococci were identified by 16S rRNA amplification and sequencing. Antimicrobial resistance was determined by disc diffusion method. Virulence and antimicrobial resistance genes were detected by PCR assays.

Results

Overall, 198 enterococcal isolates were identified from 2897 mastitis samples, including 137 (4.7%) E. faecalis, 50 (1.7%) E. faecium and 11 (0.4%) E. hirae. E. faecalis, E. faecium and E. hirae isolates showed high resistance to tetracycline (92.7%, 68.0%, 90.9%), followed by erythromycin (86.9%, 76.0%, 72.7%). The multidrug-resistant strains of E. faecalis and E. faecium were 29 (21.2%) and 13 (26.0%), respectively. The resistance of E. faecalis, E. faecium and E. hirae isolates to tetracycline is mainly attributed to the presence of tetL (alone or combined with tetM and/or tetK), the erythromycin resistance to ermB (alone or combined with ermC and/or ermA). Moreover, cpd (94.2%), gelE (77.4%), efaAfs (93.4%), and esp (79.6%) were the most common virulence genes in E. faecalis. In E. faecium, except for the gene efaAfs (82.0%), other virulence genes are rarely found. Only two strains of E. hirae carrying asa1 gene were detected.

Conclusion

The results of this study can provide a reference for the prevention and treatment of bovine mastitis caused by enterococci.

Evaluation of Antimicrobial Resistancein Clinical Isolates of Enterococcus spp. Obtained from Hospital Patients in Latvia

Background and Objective: Enterococci are typically found in a healthy human gastrointestinal tract but can cause severe infections in immunocompromised patients. Such infections are treated with antibiotics. This study addresses the rising concern of antimicrobial resistance (AMR) in Enterococci, focusing on the prevalence of vancomycin-resistant enterococcus (VRE) strains. Materials and Methods: The pilot study involved 140 Enterococci isolates collected between 2021 and 2022 from two multidisciplinary hospitals (with and without local therapeutic drug monitoring protocol of vancomycin) in Latvia. Microbiological assays and whole genome sequencing were used. AMR gene prevalence with resistance profiles were determined and the genetic relationship and outbreak evaluation were made by applying core genome multi-locus sequence typing (cgMLST). Results: The acquired genes and mutations were responsible for resistance against 10 antimicrobial classes, including 25.0% of isolates expressing resistance to vancomycin, predominantly of the vanB type. Genetic diversity among E. faecalis and E. faecium isolates was observed and seven potential outbreak clusters were identified, three of them containing sequence types ST6, ST78 and ST80. The prevalence of vancomycin resistance was highest in the hospital without a therapeutic drug-monitoring protocol and in E. faecium. Notably, a case of linezolid resistance due to a mutation was documented. Conclusions: The study illustrates the concerning prevalence of multidrug-resistant Enterococci in Latvian hospitals, showcasing the rather widespread occurrence of vancomycin-resistant strains. This highlights the urgency of implementing efficient infection control mechanisms and the need for continuous VRE surveillance in Latvia to define the scope and pattern of the problem, influencing clinical decision making and planning further preventative measures.

Enterococci facilitate polymicrobial infections

Enterococci are ubiquitous members of the gut microbiota in human beings and animals and are among the most important nosocomial organisms. Due to their opportunistic pathogenicity, enterococci are referred to as pathobionts and play decisive roles in a diverse array of polymicrobial infections. Enterococci can promote the colonization, pathogenesis, and persistence of various pathogens, compromise the efficacy of drugs, and pose a severe threat to public health. Most current treatments tend to focus on the sole pathogenic bacteria, with insufficient attention to the driving role of enterococci. In this review, we summarize the characteristics of enterococci in infections, the factors facilitating their outgrowth, as well as the sites and types of enterococci-associated polymicrobial infections. We present an overview of the underlying mechanisms of enterococci-mediated pathogenesis in polymicrobial infections. Furthermore, we discuss alternative strategies and potential intervention approaches to restrict such infections, shedding light on the discovery and development of new therapies against polymicrobial infections.

In vitro study of biogenic amine production and gastrointestinal stress tolerance by some enterococci strains

BACKGROUND

Owing to the toxic effects of enterococci, their biogenic amine production is a negative aspect of safe strain selection and unfavourable activity in food. Additionally, the ability to tolerate acid and bile are two important traits for the selection of probiotic strains since they show the probiotic bacteria's capacity to survive throughout gastrointestinal transit. In the present work, six enterococci strains belonging to Enterococcus gallinarum and Enterococcus hirae were subjected to in vitro evaluation of their ability to produce biogenic amines and to tolerate gastrointestinal stress in order to investigate their possibility for future intended use as probiotics.

RESULTS

All enterococci isolates possessed good viability at low pH (pH 4) and in the presence of bile salts (0.3%), indicating their ability to survive passage through the gastrointestinal tract. In addition, selected strains had a high ability to produce tyramine in tyrosine decarboxylase broth, while medium levels of histamine were detected (below 74 mg L-1 ) in experimental media in vitro. Other biogenic amines were also formed at various levels by most of the enterococci strains.

CONCLUSION

All enterococci strains, with the exception of E. gallinarum DM 29, are powerful tyramine producers, and their capacity to create histamine is inferior to that of tyramine. However, more investigations are needed before considering their use as bio-preservatives or starter cultures in foods. © 2023 Society of Chemical Industry.

Enterococci, Van Gene-Carrying Enterococci, and Vancomycin Concentrations in the Influent of a Wastewater Treatment Plant in Southeast Germany

Vancomycin-resistant (VR) Enterococcus spp. can be detected in high concentrations in wastewaters and pose a risk to public health. During a one-year study (September 2022-August 2023), 24 h composite raw wastewater samples (n = 192) of a municipal wastewater treatment plant were investigated for cultivable enterococci. After growth on Slanetz-Bartley agar (SBA), a mean concentration of 29,736 ± 9919 cfu/mL was calculated. Using MALDI-TOF MS to characterize randomly picked colonies (n = 576), the most common species were found to be Enterococcus faecium (72.6%), E. hirae (13.7%), and E. faecalis (8.0%). Parallel incubation of wastewater samples on SBA and VRESelect agar resulted in a mean rate of VR enterococci of 2.0 ± 1.5%. All the tested strains grown on the VRESelect agar (n = 172) were E. faecium and carried the vanA (54.6%) or vanB gene (45.4%) with limited sequence differences. In susceptibility experiments, these isolates showed a high-level resistance to vancomycin (>256 µg/mL). Concentration of vancomycin was determined in 93.7% of 112 wastewater samples (mean: 123.1 ± 64.0 ng/L) and varied between below 100 ng/L (the detection limit) and 246.6 ng/L. A correlation between the concentration of vancomycin and the rate of VR strains among the total enterococci could not be found. The combination of incubation of samples on SBA and a commercial vancomycin-containing agar applied in clinical microbiology with a multiplex PCR for detection of van genes is an easy-to-use tool to quantify and characterize VR Enterococcus spp. in water samples.

Health risk assessment of swimming beaches microbial contamination: a case study - Mahmoudabad, Iran

Waterborne organisms in marine water generally originate from untreated wastewater discharged into the sea. The presence of numerous leisure beaches in Mahmoudabad city, Iran, annually attracts thousands of tourists from all over the country to participate in recreational swimming activities. This study probabilistically characterized the health risks associated with recreational swimming engendered by waterborne pathogens, such as intestinal enterococci and Escherichia coli (E. coli) at 15 sampling points along the beaches of the study using quantitative microbial risk assessment (QMRA). The mean annual infection risk of E. coli in children and adults was 0.424 and 0.229, respectively. The respective risk in terms of enterococci was 0.999 and 0.997, which were higher than the level recommended by the WHO and EPA. The results show that the risk of infection for children was higher than adults. Related authorities have to consider measures to improve environmental quality to protect tourists' and residents' well-being.

Genomic insights into Enterococcus faecium isolates from marine bivalves highlight One Health concerns and healthcare linkages

Enterococci, especially Enterococcus faecium, are one of today's leading causes of multidrug-resistant infections in hospital settings. The marine environment may harbour enterococci, but its role as an evolutionary niche and as a vector for the spread of enterococci is sparsely investigated. Hence, by applying enterococci in bivalves as a sentinel tool, this study aimed to describe the prevalence of enterocooci along the Norwegian coast and in addition the phylogeny of E. faecium in particular. Enterococci in batch samples of marine bivalves, harvested from 86 different locations, were quantitatively examined by a culture-dependent most probable number (MPN) method. Isolates were identified by MALDI-TOF-MS prior to antimicrobial susceptibility testing by broth microdilution. In-detail analyses of a representative selection of E. faecium isolates (n=148) were done by Illumina whole-genome sequencing, and assembled genomes were compared to closed E. faecium genomes in the public databases and to genomes from commensal and clinical isolates from Norway. Diversity among E. faecium within the same batch sample of bivalves was also explored. Enterococci were detected in 287 of the 471 examined bivalve samples, but in low concentrations with a median value of <18 MPN /100 g. From positive samples, 479 isolates of enterococci were identified belonging to ten different species, where E. faecium (n=247), Enterococcus hirae (n=114) and Enterococcus faecalis (n=66) were most frequently found. Resistance towards one or more antimicrobial agents was observed in 197 isolates (41 %), none of the isolates showed acquired resistance to vancomycin or linezolid. Phylogenetic analyses revealed high diversity among the E. faecium isolates and showed that the marine niche is dominated by strains from the non-clinical setting belonging to clade A2 (n=85) and B (E. lactis) (n=60). Only three isolates belonged to the hospital-associated clade A1 (ST80 and ST117). Two of these clustered with one isolate from a hospitalized patient and one from a non-hospitalized person. This study demonstrated a high prevalence, but low concentrations of enterococci in bivalves, and low levels of antimicrobial resistance. E. faecium genomes showed high population diversity and that very few E. faecium isolates in bivalves may have arisen from the human healthcare system. A systematic surveillance of target micro-organisms applying methods examining multiple isolates from the same bivalve sample provides important data to assess the enterococcal phylogeny, antimicrobial resistance and the level of faecal pollution in the marine environment.

Insight into the Postbiotic Potential of the Autochthonous Bacteriocin-Producing Enterococcus faecium BGZLM1-5 in the Reduction in the Abundance of Listeria monocytogenes ATCC19111 in a Milk Model

This study aimed to explore the probiogenomic characteristics of artisanal bacteriocin-producing Enterococcus faecium BGZLM1-5 and its potential application in reducing Listeria monocytogenes in a milk model. The BGZLM1-5 strain was isolated from raw cow's milk from households in the Zlatar Mountain region. The whole genome sequencing approach and bioinformatics analyses reveal that the strain BGZLM1-5 is non-pathogenic to humans. Bacteriocin-containing supernatant was thermally stable and antimicrobial activity retained 75% of the initial activity compared with that of the control after treatment at 90 °C for 30 min. Antimicrobial activity maintained relative stability at pH 3-11 and retained 62.5% of the initial activity compared with that of the control after treatment at pH 1, 2, and 12. The highest activity of the partially purified bacteriocin was obtained after precipitation at 40% saturation with ammonium sulfate and further purification by mixing with chloroform. Applying 3% and 5% (v/v) of the bacteriocin-containing supernatant and 0.5% (v/v) of the partially purified bacteriocin decreased the viable number of L. monocytogenes ATCC19111 after three days of milk storage by 23.5%, 63.5%, and 58.9%, respectively.

Characterizing the impact of Enterococcus cecorum infection during late embryogenesis on disease progression, cecal microbiome composition, and early performance in broiler chickens

Enterococcus cecorum (EC) has been associated with septicemia and early mortality in broiler chickens. There is limited research investigating the pathogenicity of EC field strains obtained from affected birds. The purpose of this study was to evaluate the effect of in-ovo administration into the amnion with different EC field isolates at d 18 of embryogenesis (DOE18). In Exp 1, 7 EC field isolates alone or in combination (EC1-EC3, EC4-EC5, EC6, and EC7) were selected based on phenotypic characteristics and evaluated at different concentrations (1 × 102, 1 × 104, and 1 × 106 CFU/200 µL/embryo) to assess the impact on early performance and macroscopic lesions. Three isolates (n = 3; EC2, EC5, EC7) were selected for additional evaluation based on the significant (P < 0.05) BWG reduction (d 0-21) compared to the negative control (NC) and the presence of macroscopic lesions observed during posting sessions at d 14 and d 21. An additional isolate associated with enterococcal spondylitis was included in Exp 2 (EC11B). Treatment groups for Exp 2 include: 1) NC, 2) EC2, 3) EC5, 4) EC7, and 5) EC11B (n = 90-120/embryos/group). Groups 2 to 5 were challenged at 1 × 102 CFU/200 µL/embryo by in-ovo injection into the amnion at DOE18. Chicks were placed in battery cages for the duration of the study (21 d), and pen weights were recorded at d 0, d 7, d 14, and d 21 to calculate average BW and BWG. At d 14 and d 21 posthatch, liver, spleen, free thoracic vertebrae (FTV), and femoral head (FH) were aseptically collected to enumerate Enterococcus spp. using Chromagar Orientation as the selective media. Cecal contents were collected at d 21 to evaluate the effect of EC challenge on the cecal microbiome composition. There was a significant (P < 0.05) reduction in BW at d 21, and BWG from d 14 to 21 and d 0 to 21, for EC7 and EC11B. Enterococcus cecorum was recovered from the FTV of all challenged groups at d 14 and d 21. The most representative lesions were pericarditis, hydropericardium, focal heart necrosis, and FH osteomyelitis. However, lesions were not uniform across challenged groups or ages (d 14 and d 21). Alpha diversity of the cecal contents was markedly lower in EC5 and EC11B compared to all treatment groups suggesting that EC exposure during late embryogenesis affect the cecal microbiome up to 21 d posthatch. Additionally, these results highlight the differences in pathogenicity of EC strains isolated from field cases and suggest that hatchery exposure to EC during late embryogenesis is a potential route of introduction into a flock.

Intestinal microbiota modulation at the strain level by the olive oil polyphenols in the diet

Introduction

Previously we have reported a r16S gene next generation sequencing study on the effect of high fat diets in the intestinal microbiota using a murine model. However, many important microbial traits occur at strain level and, in order to detect these population changes, culture-dependent approaches need to be applied. With this goal, we decided to study a very well-known commensal genus, Enterococcus, and therefore, intestinal enterococci methodically isolated during the above-mentioned experiment were analyzed.

Materials and methods

A collection of 75 distinct enterococcal strains isolated from feces of mice fed a standard diet or high-fat diets enriched with butter, refined olive oil, or extra virgin olive oil and after 0, 6 or 12 weeks of diet, were genetically and phenotypically characterized in search of virulence factors, biogenic amine production and antibiotic resistance. All strains were tested for the susceptibility in vitro to two virgin olive oil polyphenols, oleuropein (the bitter principle of olives) and hydroxytyrosol (derived from oleuropein by enzymatic hydrolysis and responsible for the high stability of olive oil).

Results

No drastic polyphenol effect was found except at high concentrations. However, when carrying out a comparative statistical study in the 75 strains of the collection according to the different diets, we have detected significant differences between the strains isolated from mice fed with a diet enriched with virgin olive oil and the rest of the diets. EVOO strains also presented less resistance to antibiotics and a more beneficial profile overall.

Discussion

These results support the prebiotic role of polyphenols, showing how they are able to modulate the set of strains that comprises a genus in the gut, allowing them to adapt to a changing environment in the host's intestine and possibly exerting effects on its physiology.

Antimicrobial overproduction sustains intestinal inflammation by inhibiting Enterococcus colonization

Loss of antimicrobial proteins such as REG3 family members compromises the integrity of the intestinal barrier. Here, we demonstrate that overproduction of REG3 proteins can also be detrimental by reducing a protective species in the microbiota. Patients with inflammatory bowel disease (IBD) experiencing flares displayed heightened levels of secreted REG3 proteins that mediated depletion of Enterococcus faecium (Efm) from the gut microbiota. Efm inoculation of mice ameliorated intestinal inflammation through activation of the innate immune receptor NOD2, which was associated with the bacterial DL-endopeptidase SagA that generates NOD2-stimulating muropeptides. NOD2 activation in myeloid cells induced interleukin-1β (IL-1β) secretion to increase the proportion of IL-22-producing CD4+ T helper cells and innate lymphoid cells that promote tissue repair. Finally, Efm was unable to protect mice carrying a NOD2 gene variant commonly found in IBD patients. Our findings demonstrate that inflammation self-perpetuates by causing aberrant antimicrobial activity that disrupts symbiotic relationships with gut microbes.

Evaluation of Enterococcal Probiotic Usage and Review of Potential Health Benefits, Safety, and Risk of Antibiotic-Resistant Strain Emergence

Enterococci are often used in probiotics but can also cause nosocomial infections. As such, enterococcal consumption may have beneficial health effects, but a thorough evaluation of virulence absence and risk of antibiotic resistance spread is needed at the strain level. This article reviewed ten online health product shopping websites in the US. On these websites, 23 probiotic products using enterococci were found across 12 companies. In addition, this article reviewed studies that demonstrated the probiotic potential of enterococcal consumption (e.g., gastrointestinal and respiratory disease, hyperlipidemia alleviation, as well as infection prevention). To investigate the safety aspects of enterococci, the present work examined studies evaluating virulence factors and antibiotic resistance. Furthermore, this article assessed research that explored these virulent factors, specifically in probiotics containing enterococci, as well as the potential transfer mechanism of their antibiotic resistance. Based on reviewed data, enterococcal probiotic consumption has been proven beneficial for conditions or symptoms of multiple diseases without any apparent adverse effects. However, due to the plasmid- or transposon-mediated gene transfer ability of enterococci, surveillance monitoring and further studies regarding enterococcal consumption are warranted. Future studies that identify enterococcal strains safe to use in probiotics without virulence factors and antibiotic resistance are imperative for evidence-based decisions by health organizations and government agencies.

Microbial Spoilage of Traditional Goose Sausages Produced in a Northern Region of Italy

Recently, during the ripening of goose sausage, a defect consisting of ammonia and vinegar smell was noticed. The producer of the craft facility, located in Lombardia, a Northern region of Italy, asked us to identify the cause of that defect. Therefore, this study aimed to identify the potential responsible agents for the spoilage of this lot of goose sausages. Spoilage was first detected by sensory analysis using the "needle probing" technique; however, the spoiled sausages were not marketable due to the high ammonia and vinegar smell. The added starter culture did not limit or inhibit the spoilage microorganisms, which were represented by Levilactobacillus brevis, the predominant species, and by Enterococcus faecalis and E. faecium. These microorganisms grew during ripening and produced a large amount of biogenic amines, which could represent a risk for consumers. Furthermore, Lev. brevis, being a heterofermentative lactic acid bacteria (LAB), also produced ethanol, acetic acid, and a variation in the sausage colour. The production of biogenic amines was confirmed in vitro. Furthermore, as observed in a previous study, the second cause of spoilage can be attributed to moulds which grew during ripening; both the isolated strains, Penicillium nalgiovense, added as a starter culture, and P. lanosocoeruleum, present as an environmental contaminant, grew between the meat and casing, producing a large amount of total volatile nitrogen, responsible for the ammonia smell perceived in the ripening area and in the sausages. This is the first description of Levilactobacillus brevis predominance in spoiled goose sausage.

Mitro-aortic infective endocarditis on bicuspid aortic valve multicomplicated: a case report

Infective endocarditis (IE) is a rare but serious disease, and despite improvements in diagnostic and therapeutic tools, it remains associated with high mortality. It can develop in a healthy heart, but most commonly in underlying heart disease. The authors discuss a 34-year-old patient, who has presented for 4 months with generalized asthenia, fever, and chills, without any notion of chest pain, arthralgias. On admission, the patient was conscious, hemodynamically, and respiratory stable, the temperature was 38.5°C. The cardiac exam heart revealed a systolic murmur rated 4/6th at the mitral focus. Transthoracic echocardiography showing vegetation on the mitral and aortic valve. Three blood cultures were taken at 1 h intervals, all positive for enterococci, thoracoabdominal and brain computed tomography scan with contrast injection was performed showing, ischemic stroke, aortic coarctation, splenic and renal infarction, mycotic aneurysms in the descending aort. IE can be the cause of several extracardiac manifestations, through vascular and/or immunological phenomena. Embolic complications are the most frequent extracardiac complications and are secondary to septic emboli from the vegetations. The prognosis of IE is worsened by the addition of cardiac and extracardiac complications such as mycotic aneurysms and septic embolic events.

Rifampicin in periprosthetic joint infections: where do we stand and where are we headed?

INTRODUCTION

A periprosthetic joint infection (PJI) is a major complication of arthroplasty. Treatment of PJI consists of surgical debridement with or without the exchange of the implant and long-term antimicrobial treatment. Rifampicin is regarded as one of the cornerstones of antimicrobial treatment for staphylococcal PJI, but the exact role of rifampicin for PJI in different clinical scenarios remains to be elucidated.

AREAS COVERED

In this perspective article, an overview is provided of in vitro, in vivo and clinical studies that were the basis of the current guidelines and recommendations for rifampicin use in daily practice for PJI. Controversial issues on indication, dosing, timing, duration and antibiotic drug interactions will be addressed. Finally, the most urgent clinical questions on rifampicin use that need answering in the nearby future will be formulated.

EXPERT OPINION

Many inquiries remain concerning the exact indications and clinical use of rifampicin in PJI. Randomized controlled trials are needed to answer these questions.

Enterococci in Diabetic Foot Infections: Prevalence, Clinical Characteristics, and Outcomes

Background

Diabetic foot infections (DFIs) are frequently polymicrobial, yet the relevance of each isolated pathogen, remains ill-defined. Specifically, the prevalence and pathogenicity of enterococcal DFIs and the impact of targeted antienterococcal treatment remain elusive.

Methods

We collected demographic, clinical, and outcome-related data on patients admitted with DFIs to the Hadassah Medical Center diabetic foot unit between 2014 and 2019. The primary outcome was a composite of in-hospital death or major amputation. Secondary outcomes included any amputation, major amputation, length of stay (LOS), and 1-year major amputation or mortality rate.

Results

Enterococci were isolated in 35% of 537 eligible DFI case patients, who were notable for a higher prevalence of peripheral vascular disease, increased levels of C-reactive protein, and higher Wagner scores. Infection in enterococci-positive individuals was mostly polymicrobial (96.8% vs 61.0% in non-enterococci-infected patients; P < .001). Enterococci-infected patients were more likely to undergo amputation (72.3% vs 50.1%; P < .001) and had longer hospital stays (median LOS, 22.5 vs 17 days; P < .001), but the primary end point of major amputation or in-hospital death did not differ between groups (25.5% vs 21.0%; P = .26). Appropriate antienterococcal antibiotics were used in 78.1% of enterococci-infected patients and, compared with results in untreated patients, were associated with a trend toward a lower rate of major amputations (20.4% vs 34.1%; P = .06) but longer hospitalization (median LOS, 24 vs 18 days; P = .07).

Conclusions

Enterococci are common in DFIs and associated with higher rates of amputation and longer hospitalization. A reduction in major amputation rates with appropriate enterococci treatment is suggested retrospectively, meriting validation by future prospective studies.

Microbial Communities in the Water Surface Microlayer and Associations with Microbes in Aerosols, Beach Sand, and Bulk Water

The water surface microlayer (SML) serves as a boundary through which microbes can be exchanged. To evaluate exchanges of microbes, this study compared microbial communities within different reservoirs, with an emphasis on the water SML and aerosols. Additionally, the microbial communities during a sewage spill and perigean tides were evaluated and the results were compared to times without these events. Results show that during perigean tides and during the sewage spill, levels of culturable bacteria were highest and showed an increase via sequencing in potential pathogenic bacteria (Corynebacterium and Vibrio, which increased from 3.5%-1800% depending on sample type). In the aerosol samples, Corynebacterium (average of 2.0%), Vibrio (1.6%), and Staphylococcus (10%), were the most abundant genera. Aerosolization factors, which were used to examine the transfer of the microbes, were high for these three genera. Measurements of general marine bacteria (GMB) by culture showed a weak but significant correlation between culturable GMB in aerosol samples versus in water and in SML. More research is needed to evaluate the exchange of pathogens between the SML and air, given the increase in potentially pathogenic microbes within the SML during rare events and evidence that suggests that microbes maintain viability during transfers across reservoirs.

Impact of Enterococci vs. Staphylococci Induced Infective Endocarditis after Transcatheter Aortic Valve Implantation

BACKGROUND

The two most common organisms found in infective endocarditis following transcatheter aortic valve implantation (TAVI-IE) are enterococci (EC-IE) and staphylococci (SC-IE). We aimed to compare clinical characteristics and outcomes of patients with EC-IE and SC-IE.

METHODS

TAVI-IE patients from 2007 to 2021 were included in this analysis. The 1-year mortality was the primary outcome measure of this retrospective multi-center analysis.

RESULTS

Out of 163 patients, 53 (32.5%) EC-IE and 69 (42.3%) SC-IE patients were included. Subjects were comparable with regard to age, sex, and clinically relevant baseline comorbidities. Symptoms at admission were not significantly different between groups, except for a lower risk for presenting with septic shock in EC-IE than SC-IE. Treatment was performed in 78% by antibiotics alone and in 22% of patients by surgery and antibiotics, with no significant differences between groups. The rate of any complication, in particular heart failure, renal failure, and septic shock during treatment for IE, was lower in EC-IE compared with SC-IE (p < 0.05). In-hospital (EC-IE: 36% vs. SC-IE: 56%, p = 0.035) and 1-year mortality (EC-IE: 51% vs. SC-IE: 70%, p = 0.009) were significantly lower in EC-IE compared with SC-IE.

CONCLUSIONS

EC-IE, compared with SC-IE, was associated with a lower morbidity and mortality. However, absolute numbers are high, a finding that should trigger further research in appropriate perioperative antibiotic management and improvement of early IE diagnosis in the case of clinical suspicion.

Loss of erm(B)-Mediated rRNA Dimethylation and Restoration of Erythromycin Susceptibility in Erythromycin-Resistant Enterococci Following Induced Linezolid Resistance

Linezolid has been reported to restore erythromycin susceptibility in erythromycin-resistant Staphylococcus aureus. This phenomenon has not been reported in enterococci and the mechanisms involved therein are still unknown. The purpose of this study was to investigate the mechanisms involved and the effect of combining linezolid with erythromycin on erythromycin-resistant enterococci. Checkerboard techniques were used to determine drug interactions, and 12 of 14 isolates showed a synergistic effect between erythromycin and linezolid (fractional inhibitory concentration <0.5). We observed that the erm(B) gene, which encodes a dimethyltransferase responsible for erythromycin resistance, was expressed from transposon Tn1545 in the tested erythromycin-resistant enterococci. After exposure to linezolid, erm(B)-mediated rRNA dimethylation at A2071 could not be detected, and the erm(B) gene was lost following acquisition of erythromycin susceptibility. Thus, in conclusion, linezolid combined with erythromycin exerts a synergistic effect against erythromycin-resistant enterococci. Linezolid treatment suppressed erm(B)-mediated rRNA dimethylation at A2071, which could lead to loss of the erm(B) gene.

Improving the antimicrobial activity of old antibacterial drug mafenide: Schiff bases and their bioactivity targeting resistant pathogens

Background: Increasing rates of acquired resistance have justified the critical need for novel antimicrobial drugs. One viable concept is the modification of known drugs. Methods & results: 21 mafenide-based compounds were prepared via condensation reactions and screened for antimicrobial efficacy, which demonstrated promising activity against both Gram-positive and Gram-negative pathogens, pathogenic fungi and mycobacterial strains (minimum inhibitory concentrations from 3.91 μM). Importantly, they retained activity against a panel of superbugs (methicillin- and vancomycin-resistant staphylococci, enterococci, multidrug-resistant Mycobacterium tuberculosis) without any cross-resistance. Unlike mafenide, most of its imines were bactericidal. Toxicity to HepG2 cells was also investigated. Conclusion: Schiff bases were significantly more active than the parent drug, with iodinated salicylidene and 5-nitrofuran/thiophene-methylidene scaffolds being preferred in identifying the most promising drug candidates.

Targeting Enterococci with Antimicrobial Activity against Clostridium perfringens from Poultry

Necrotic enteritis (NE), caused by Clostridium perfringens, is an emerging issue in poultry farming. New approaches, other than antibiotics, are necessary to prevent NE development and the emergence of multidrug-resistant bacteria. Enterococci are commensal microorganisms that can produce enterocins, antimicrobial peptides with activities against pathogens, and could be excellent candidates for protective cultures. This study aimed to screen and characterize Enterococcus strains of poultry origin for their inhibitory activity against C. perfringens. In total, 251 Enterococcus strains of poultry origin plus five bacteriocin-producing (BP+) E. durans strains of other origins were screened for antimicrobial activity against the indicator C. perfringens X2967 strain using the "spot on the lawn" method. We detected thirty-two BP+ strains (eleven Enterococcus faecium, nine E. gallinarum, eight E. faecalis, three E. durans, and one E. casseliflavus). We further studied the antimicrobial activity of the supernatants of these 32 BP+ strains using agar well diffusion and microtitration against a collection of 20 C. perfringens strains. Twelve BP+ enterococci that were found to exhibit antimicrobial activity against C. perfringens were characterized using whole genome sequencing. Among these, E. faecium X2893 and X2906 were the most promising candidates for further studies as protective cultures for poultry farming. Both strains belong to the sequence type ST722, harbor the genes encoding for enterocin A and enterocin B, do not possess acquired resistance genes, do not carry plasmids, and present the acm gene, which is implicated in host colonization. Further research is needed to determine the utility of these strains as protective cultures.

Should Perirectal Swab Culture Be Performed in Cases Admitted to the Neonatal Intensive Care Unit? Lessons Learned from the Neonatal Intensive Care Unit

Serial perirectal swabs are used to identify colonization of multidrug-resistant bacteria and prevent spread. The purpose of this study was to determine colonization with carbapenem-resistant Enterobacterales (CRE) and vancomycin-resistant Enterococci (VRE). An additional purpose was to establish whether sepsis and epidemic associated with these factors were present in the neonatal intensive care unit (NICU), to which infants with hospital stays exceeding 48 h in an external healthcare center NICU were admitted. Perirectal swab samples were collected in the first 24 h by a trained infection nurse using sterile cotton swabs moistened with 0.9% NaCl from patients admitted to our unit after hospitalization exceeding 48 h in an external center. The primary outcome was positivity in perirectal swab cultures, and the secondary outcomes were whether this caused invasive infection and significant NICU outbreaks. A total of 125 newborns meeting the study criteria referred from external healthcare centers between January 2018 and January 2022 were enrolled. Analysis revealed that CRE constituted 27.2% of perirectal swab positivity and VRE 4.8%, and that one in every 4.4 infants included in the study exhibited perirectal swab positivity. The detection of colonization by these microorganisms, and including them within the scope of surveillance, is an important factor in the prevention of NICU epidemics.