Penicillin-Binding Proteins and Alternative Dual-Beta-Lactam Combinations for Serious Enterococcus faecalis Infections with Elevated Penicillin MICs.

Ampicillin-ceftriaxone has become a first-line therapy for Enterococcus faecalis endocarditis. We characterized the penicillin-binding protein (PBP) profiles of various E. faecalis strains and tested for synergy to better inform beta-lactam options for the treatment of E. faecalis infections. We assessed the affinity of PBP2B from elevated-MIC strain E. faecalis LS4828 compared to type strain JH2-2 using the fluorescent beta-lactam Bocillin FL. We also characterized pbp4 and pbpA structures and PBP4 and PBP2B expression and used deletion and complementation studies to assess the impact of PBP2B on the levels of resistance. We tested penicillin-susceptible and -resistant E. faecalis isolates against ceftriaxone or ceftaroline combinations with other beta-lactams in 24-h time-kill studies. Two penicillin-susceptible strains (JH2-2 and L2052) had identical pbp sequences and similar PBP expression levels. One reduced-penicillin-susceptibility strain (L2068) had pbp sequences identical to those of the susceptible strains but expressed more PBP4. The second decreased-penicillin-susceptibility strain (LS4828) had amino acid substitutions in both PBP4 and PBP2B and expressed increased quantities of both proteins. PBP2B did not appear to contribute significantly to the elevated beta-lactam MICs. No synergy was demonstrable against the strains with both mutated PBPs and increased expression (L2068 and LS4828). Meropenem plus ceftriaxone or ertapenem plus ceftriaxone demonstrated the most consistent synergistic activity. PBP2B of strain LS4828 does not contribute significantly to reduced penicillin susceptibility. Neither the MIC nor the level of PBP expression correlated directly with the identified synergistic combinations when tested at static subinhibitory concentrations.

Houston, We Have a Problem: Reports of Clostridioides difficile Isolates With Reduced Vancomycin Susceptibility.

During the past 4 decades, oral vancomycin has been a mainstay of Clostridioides difficile infection (CDI) therapy with no reports of treatment failure due to emergence of vancomycin resistance. However, C. difficile isolates with high-level phenotypic resistance to vancomycin have recently been reported in 3 distinct geographic regions. There is an urgent need for surveillance to determine if strains with reduced vancomycin susceptibility are circulating in other areas. In a Cleveland-area hospital, screening of 176 CDI stool specimens yielded no C. difficile isolates with reduced vancomycin susceptibility and highlighted the potential for false-positive results due to contamination with vancomycin-resistant enterococci. Additional studies are needed to clarify whether reduced vancomycin susceptibility is an emerging problem that will alter clinical practice. Clinicians should alert their health department if they observe a substantial increase in the frequency of vancomycin treatment failure in patients diagnosed with CDI with no alternative explanation for diarrhea.

Meropenem plus Ceftaroline Is Active against Enterococcus faecalis in an In Vitro Pharmacodynamic Model Using Humanized Dosing Simulations.

The standard of care for serious Enterococcus faecalis infections is ampicillin plus ceftriaxone. Ampicillin's inconvenient dosing schedule, drug instability, allergy potential, along with ceftriaxone's high risk for Clostridioides difficile infection and its promotion of vancomycin-resistant enterococci (VRE), led our team to explore alternative options. This work aimed to understand the role of carbapenems in combination with cephalosporins in these infections. We selected two ampicillin and penicillin susceptible E. faecalis strains (AMP-MIC 0.5-2 µg/mL; PCN-MIC 2 µg/mL) and simulated human therapeutic dosing regimens in a 48-h in vitro pharmacodynamic model (IVPD) with ampicillin (2g q4h), ertapenem (1g q24h), meropenem (2g q8h), ceftriaxone (2g q12h), and ceftaroline (600 mg q8h). As expected, ampicillin plus ceftriaxone demonstrated enhanced activity compared with ampicillin monotherapy with no MIC increases in either isolate. Meropenem and ceftaroline demonstrated significant kill against both isolates, with no regrowth or MIC increases occurring. Meropenem plus ceftriaxone also demonstrated significant kill, and while no MIC increases were identified for meropenem, there was minor regrowth and larger standard deviations. Ertapenem combined with either ceftriaxone or ceftaroline enhanced activity at 24 h, but at 48 h, regrowth occurred, and ertapenem MIC increases were noted. Meropenem-based combination therapy against E. faecalis may provide clinicians with another regimen to treat severe E. faecalis infections. Meropenem plus ceftaroline was as active as the standard of care treatment (ampicillin plus ceftriaxone) and may serve as an alternative for serious E. faecalis infections. Further studies are warranted to determine the clinical efficacy.

An Updated History of Antimicrobial Agents and Chemotherapy: 2000-2020.

Since its inaugural issue nearly half a century ago, Antimicrobial Agents and Chemotherapy has served as a premier source for reports on scientific and clinical advances in the field of antimicrobial chemotherapy. As a follow-up to the previous "History of Antimicrobial Agents and Chemotherapy from 1972 to 1998" written by George A. Jacoby (Antimicrob Agents Chemother 43:999-1002, 1999, https://doi.org/10.1128/AAC.43.5.999), we herein highlight the further evolution of this comprehensive and authoritative journal in response to changing science, demographics, and information technology.

The Enterococcus: a Model of Adaptability to Its Environment.

The genus Enterococcus comprises a ubiquitous group of Gram-positive bacteria that are of great relevance to human health for their role as major causative agents of health care-associated infections. The enterococci are resilient and versatile species able to survive under harsh conditions, making them well adapted to the health care environment. Two species cause the majority of enterococcal infections: Enterococcus faecalis and Enterococcus faecium Both species demonstrate intrinsic resistance to common antibiotics, such as virtually all cephalosporins, aminoglycosides, clindamycin, and trimethoprim-sulfamethoxazole. Additionally, a remarkably plastic genome allows these two species to readily acquire resistance to further antibiotics, such as high-level aminoglycoside resistance, high-level ampicillin resistance, and vancomycin resistance, either through mutation or by horizontal transfer of genetic elements conferring resistance determinants.

Indicators of Healthy Architecture-a Systematic Literature Review.

The design of the built environment plays an important role as a determinant of health. As a society, we are spending an increasing proportion of our time indoors and now spend over 80% of our life inside, so the design of buildings can greatly impact on human health. Accordingly, architecture health indices (AHIs) are used to evidence the effects on human health associated with the design of buildings. AHIs provide quantitative and empirical data upon which architects, clients, users and other stakeholders might monitor and evaluate the healthiness (or otherwise) of architectural design. A systematic literature review was conducted to reveal the current state of knowledge, reveal gaps, explore potential usage and highlight best practice in this area. Whilst there are a number of different health indicators for the built/urban environments more generally, the scope of this review is limited to the scale of a building and specifically those aspects within the remit of a professional architect. In order to examine the range and characteristics of AHIs currently in use, this review explored three electronic bibliographic databases from January 2008 to January 2019. A two-stage selection was undertaken and screening against eligibility criteria checklist carried out. From 15 included studies, 127 documents were identified, and these included 101 AHI. A sample of the most commonly used AHIs was then analysed at an item level. The review reveals that most AHIs are limited to measuring communicable diseases that directly affect physical health through e.g. air quality or water quality. There are very few indicators focusing on factors affecting mental and social health; given the increase in mental and social health problems, greater focus on AHIs related to these health issues should be included. Furthermore, the research reveals an absence of AHIs that address non-communicable diseases (NCDs). As the majority of all poor health outcomes globally are now related to NCDs, and many are associated with the design of the built environment, there is an urgent need to address this situation.

Fosfomycin for Injection (ZTI-01) Versus Piperacillin-tazobactam for the Treatment of Complicated Urinary Tract Infection Including Acute Pyelonephritis: ZEUS, A Phase 2/3 Randomized Trial.

BACKGROUND: ZTI-01 (fosfomycin for injection) is an epoxide antibiotic with a differentiated mechanism of action (MOA) inhibiting an early step in bacterial cell wall synthesis. ZTI-01 has broad in vitro spectrum of activity, including multidrug-resistant Gram-negative pathogens, and is being developed for treatment of complicated urinary tract infection (cUTI) and acute pyelonephritis (AP) in the United States. METHODS: Hospitalized adults with suspected or microbiologically confirmed cUTI/AP were randomized 1:1 to 6 g ZTI-01 q8h or 4.5 g intravenous (IV) piperacillin-tazobactam (PIP-TAZ) q8h for a fixed 7-day course (no oral switch); patients with concomitant bacteremia could receive up to 14 days. RESULTS: Of 465 randomized patients, 233 and 231 were treated with ZTI-01 and PIP-TAZ, respectively. In the microbiologic modified intent-to-treat (m-MITT) population, ZTI-01 met the primary objective of noninferiority compared with PIP-TAZ with overall success rates of 64.7% (119/184 patients) vs 54.5% (97/178 patients), respectively; treatment difference was 10.2% (95% confidence interval [CI]: -0.4, 20.8). Clinical cure rates at test of cure (TOC, day 19-21) were high and similar between treatments (90.8% [167/184] vs 91.6% [163/178], respectively). In post hoc analysis using unique pathogens typed by pulsed-field gel electrophoresis, overall success rates at TOC in m-MITT were 69.0% (127/184) for ZTI-01 versus 57.3% (102/178) for PIP-TAZ (difference 11.7% 95% CI: 1.3, 22.1). ZTI-01 was well tolerated. Most treatment-emergent adverse events, including hypokalemia and elevated serum aminotransferases, were mild and transient. CONCLUSIONS: ZTI-01 was effective for treatment of cUTI including AP and offers a new IV therapeutic option with a differentiated MOA for patients with serious Gram-negative infections. CLINICAL TRIAL REGISTRATION: NCT02753946.

Updating the determinants of health model in the Information Age.

In 1991, Dahlgren and Whitehead produced a highly influential model of the determinants of health that has since been used by numerous national and international public health organizations globally. The purpose of the model is to enable interventions that improve health to be addressed at four key policy levels. It is not a model of health or disease; instead the model is structured around health policy decision-making. However the model needs an update, since it was devised there has been a digital revolution that has transformed every aspect of: human life, our cities, society and the fundamental principles upon which the global economy operates. The article examines the impact of Information and Communication Technologies (ICT) on the determinants of health. ICT has given rise to a new Information Age that is implicated in many of the major global health issues today. Addressing contemporary health issues requires intervention at the level of ICT, particularly as health communication online is central to the delivery and dissemination of public health policies.

A Review of Combination Antimicrobial Therapy for Enterococcus faecalis Bloodstream Infections and Infective Endocarditis.

Enterococci, one of the most common causes of hospital-associated infections, are responsible for substantial morbidity and mortality. Enterococcus faecalis, the more common and virulent species, causes serious high-inoculum infections, namely infective endocarditis, that are associated with cardiac surgery and mortality rates that remained unchanged for the last 30 years. The best cures for these infections are observed with combination antibiotic therapy; however, optimal treatment has not been fully elucidated. It is the purpose of this review to highlight treatment options and their limitations, and provide direction for future investigative efforts to aid in the treatment of these severe infections. While ampicillin plus ceftriaxone has emerged as a preferred treatment option, mortality rates continue to be high, and from a safety standpoint, ceftriaxone, unlike other cephalosporins, promotes colonization with vancomycin resistant-enterococci due to high biliary concentrations. More research is needed to improve patient outcomes from this high-mortality disease.

High-Level Fosfomycin Resistance in Vancomycin-Resistant Enterococcus faecium.

Of 890 vancomycin-resistant Enterococcus faecium isolates obtained by rectal screening from patients in Pittsburgh, Pennsylvania, USA, 4 had MICs >1,024 µg/mL for fosfomycin. These isolates had a Cys119Asp substitution in the active site of UDP-N-acetylglucosamine enolpyruvyl transferase. This substitution increased the fosfomycin MIC >4-fold and rendered this drug inactive in biochemical assays.

Ampicillin in Combination with Ceftaroline, Cefepime, or Ceftriaxone Demonstrates Equivalent Activities in a High-Inoculum Enterococcus faecalis Infection Model.

Ampicillin-ceftriaxone combination therapy has become a predominant treatment for serious Enterococcus faecalis infections, such as endocarditis. Unfortunately, ceftriaxone use is associated with future vancomycin-resistant enterococcus colonization. We evaluated E. faecalis in an in vitro pharmacodynamic model against simulated human concentration-time profiles of ampicillin plus ceftaroline, cefepime, ceftriaxone, or gentamicin. Ampicillin-cefepime and ampicillin-ceftaroline demonstrated activities similar to those of ampicillin-ceftriaxone against E. faecalis.

Homologous Recombination within Large Chromosomal Regions Facilitates Acquisition of ß-Lactam and Vancomycin Resistance in Enterococcus faecium.

The transfer of DNA between Enterococcus faecium strains has been characterized both by the movement of well-defined genetic elements and by the large-scale transfer of genomic DNA fragments. In this work, we report on the whole-genome analysis of transconjugants resulting from mating events between the vancomycin-resistant E. faecium C68 strain and the vancomycin-susceptible D344RRF strain to discern the mechanism by which the transferred regions enter the recipient chromosome. Vancomycin-resistant transconjugants from five independent matings were analyzed by whole-genome sequencing. In all cases but one, the penicillin binding protein 5 (pbp5) gene and the Tn5382 vancomycin resistance transposon were transferred together and replaced the corresponding pbp5 region of D344RRF. In one instance, Tn5382 inserted independently downstream of the D344RRF pbp5 gene. Single nucleotide variant (SNV) analysis suggested that entry of donor DNA into the recipient chromosome occurred by recombination across regions of homology between donor and recipient chromosomes, rather than through insertion sequence-mediated transposition. The transfer of genomic DNA was also associated with the transfer of C68 plasmid pLRM23 and another putative plasmid. Our data are consistent with the initiation of transfer by cointegration of a transferable plasmid with the donor chromosome, with subsequent circularization of the plasmid-chromosome cointegrant in the donor prior to transfer. Entry into the recipient chromosome most commonly occurred across regions of homology between donor and recipient chromosomes.

Differential Effects of Penicillin Binding Protein Deletion on the Susceptibility of Enterococcus faecium to Cationic Peptide Antibiotics.

Beta-lactam antibiotics sensitize Enterococcus faecium to killing by endogenous antimicrobial peptides (AMPs) of the innate immune system and daptomycin through mechanisms yet to be elucidated. It has been speculated that beta-lactam inactivation of select E. faecium penicillin binding proteins (PBPs) may play a pivotal role in this sensitization process. To characterize the specific PBP inactivation that may be responsible for these phenotypes, we utilized a previously characterized set of E. faecium PBP knockout mutants to determine the effects of such mutations on the activity of daptomycin and the AMP human cathelicidin (LL-37). Enhanced susceptibility to daptomycin was dependent more on a cumulative effect of multiple PBP deletions than on inactivation of any single specific PBP. Selective knockout of PBPZ rendered E. faecium more vulnerable to killing by both recombinant LL-37 and human neutrophils, which produce the antimicrobial peptide in high quantities. Pharmacotherapy targeting multiple PBPs may be used as adjunctive therapy with daptomycin to treat difficult E. faecium infections.

Mutation landscape of acquired cross-resistance to glycopeptide and ß-lactam antibiotics in Enterococcus faecium.

Bypass of the d,d-transpeptidase activity of penicillin-binding proteins by an l,d-transpeptidase (Ldtfm) results in resistance to ampicillin and glycopeptides in Enterococcus faecium M9, a mutant obtained by nine consecutive selection steps. Resistance requires activation of a cryptic locus for production of the essential tetrapeptide-containing substrate of Ldtfm and impaired activity of protein phosphatase StpA. Here, whole-genome sequencing revealed a high mutation rate for the entire selection procedure (79 mutations in 900 generations). Acquisition of a mutation in the mismatch repair gene mutL had little impact on the frequency of rifampin-resistant mutants although the mutation spectrum of M9 was typical of impaired MutL with high transversion to transition (40/11) and substitution to deletion (51/28) ratios. M9 did not mainly accumulate neutral mutations since base substitutions occurred more frequently in coding sequences than expected (χ(2) = 5.0; P < 0.05) and silent mutations were underrepresented (χ(2) = 5.72; P < 0.02). None of the mutations directly affected recognition of the tetrapeptide substrate of Ldtfm by peptidoglycan synthesis enzymes. Instead, mutations appear to remodel regulatory circuits involving two-component regulatory systems and sugar metabolism. The high number of mutations required for activation of the l,d-transpeptidase pathway may strongly limit emergence of cross-resistance to ampicillin and glycopeptides by this mechanism.

Vancomycin-resistant enterococci colonization among dialysis patients: a meta-analysis of prevalence, risk factors, and significance.

BACKGROUND: Vancomycin-resistant enterococci (VRE) have become important nosocomial pathogens causing outbreaks worldwide. Patients undergoing dialysis represent a vulnerable population due to their comorbid conditions, frequent use of antibacterial agents, and frequent contact with health care settings. STUDY DESIGN: Systematic review and meta-analysis of cross-sectional studies of screening for VRE colonization. SETTING & POPULATION: Patients receiving long-term dialysis treatment. SELECTION CRITERIA FOR STUDIES: We performed a systematic literature search of PubMed and EMBASE databases to identify studies performing screening for VRE colonization among dialysis patients. PREDICTOR: Region, recent use of vancomycin or other antibiotics, previous hospitalization. OUTCOMES: (1) VRE colonization and (2) rate of VRE infection among colonized and noncolonized individuals. Relative effects were expressed as ORs and 95% CIs. RESULTS: We identified 23 studies that fulfilled the inclusion criteria and provided data for 4,842 dialysis patients from 100 dialysis centers. The pooled prevalence of VRE colonization was 6.2% (95% CI, 2.8%-10.8%), with significant variability between centers. The corresponding number for North American centers was 5.2% (95% CI, 2.8%-8.2%). Recent use of any antibiotic (OR, 3.62; 95% CI, 1.22-10.75), particularly vancomycin (OR, 5.15; 95% CI, 1.56-17.02), but also use of antibiotics other than vancomycin (OR, 2.92; 95% CI, 0.99-8.55) and recent hospitalization (OR, 4.55; 95% CI, 1.93-10.74) significantly increased the possibility of a VRE-positive surveillance culture. Colonized patients had a significantly higher risk of VRE infection (OR, 21.62; 95% CI, 5.33-87.69) than their noncolonized counterparts. LIMITATIONS: In 19 of 23 studies, a low percentage of dialysis patients (<80%) consented to participate in the screening procedure. 4 of 8 studies in which patients were followed up for more than 1 month reported VRE infections and only 5 of 23 studies provided extractable data for antibiotic consumption prior to screening. CONCLUSIONS: VRE colonization is prevalent in dialysis centers. Previous antibiotic use, in particular vancomycin, and recent hospitalization are important predicting factors of colonization, whereas the risk of VRE infection is significantly higher for colonized patients.