Phytochemical Evaluation of Terminalia canescens DC. Radlk. Extracts with Antibacterial and Antibiotic Potentiation Activities against Selected ß-Lactam Drug-Resistant Bacteria.

Terminalia canescens DC. Radlk. (family: Combretaceae) is native to northern Australia. Species of the genus Terminalia are widely used as traditional medicines to treat diverse ailments, including bacterial infections. However, we were unable to find any studies that had examined the antimicrobial activity of T. canescens. In this study, T. canescens was screened against a panel of bacterial pathogens, including multi-antibiotic-resistant strains. Solvents with different polarities were used to extract different complements of phytochemicals from T. canescens leaves. Methanolic and aqueous extracts exhibited substantial antimicrobial activity against various pathogens, including those that are multidrug-resistant strains. When combined with some selected clinical antibiotics, some extracts potentiated the antibacterial inhibitory activity. This study identified two synergistic, eleven additive, eleven non-interactive and eight antagonistic interactions. The toxicities of the plant extracts were examined in the Artemia franciscana nauplii assay and were found to be non-toxic, except the aqueous extract, which showed toxicity. Metabolomic liquid chromatography-mass spectrometry (LC-MS) analyses highlighted and identified several flavonoids, including vitexin, quercetin, orientin and kaempferol, as well as the tannins ellagic acid and pyrogallol, which may contribute to the antibacterial activities observed herein. The possible mechanism of action of these extracts was further explored in this study.

Do dietary interventions exert clinically important effects on the bioavailability of ß-lactam antibiotics? A systematic review with meta-analyses.

BACKGROUND: Managing drug-food interactions may help to achieve the optimal action and safety profile of ß-lactam antibiotics. METHODS: We conducted a systematic review with meta-analyses in adherence to PRISMA guidelines for 32 ß-lactams. We included 166 studies assessing the impact of food, beverages, antacids or mineral supplements on the pharmacokinetic (PK) parameters or PK/pharmacodynamic (PK/PD) indices. RESULTS: Eighteen of 25 ß-lactams for which data on food impact were available had clinically important interactions. We observed the highest negative influence of food (AUC or Cmax decreased by >40%) for ampicillin, cefaclor (immediate-release formulations), cefroxadine, cefradine, cloxacillin, oxacillin, penicillin V (liquid formulations and tablets) and sultamicillin, whereas the highest positive influence (AUC or Cmax increased by >45%) for cefditoren pivoxil, cefuroxime and tebipenem pivoxil (extended-release tablets). Significantly lower bioavailability in the presence of antacids or mineral supplements occurred for 4 of 13 analysed ß-lactams, with the highest negative impact for cefdinir (with iron salts) and moderate for cefpodoxime proxetil (with antacids). Data on beverage impact were limited to 11 antibiotics. With milk, the extent of absorption was decreased by >40% for cefalexin, cefradine, penicillin G and penicillin V, whereas it was moderately increased for cefuroxime. No significant interaction occurred with cranberry juice for two tested drugs (amoxicillin and cefaclor). CONCLUSIONS: Factors such as physicochemical features of antibiotics, drug formulation, type of intervention, and patient's health state may influence interactions. Due to the poor actuality and diverse methodology of included studies and unproportionate data availability for individual drugs, we judged the quality of evidence as low.

Comprehensive stability analysis of 13 ß-lactams and ß-lactamase inhibitors in in vitro media, and novel supplement dosing strategy to mitigate thermal drug degradation.

Non-clinical antibiotic development relies on in vitro susceptibility and infection model studies. Validating the achievement of the targeted drug concentrations is essential to avoid under-estimation of drug effects and over-estimation of resistance emergence. While certain ß-lactams (e.g., imipenem) and ß-lactamase inhibitors (BLIs; clavulanic acid) are believed to be relatively unstable, limited tangible data on their stability in commonly used in vitro media are known. We aimed to determine the thermal stability of 10 ß-lactams and 3 BLIs via LC-MS/MS in cation-adjusted Mueller Hinton broth at 25 and 36°C as well as agar at 4 and 37°C, and in water at -20, 4, and 25°C. Supplement dosing algorithms were developed to achieve broth concentrations close to their target over 24 h. During incubation in broth (pH 7.25)/agar, degradation half-lives were 16.9/21.8 h for imipenem, 20.7/31.6 h for biapenem, 29.0 h for clavulanic acid (studied in broth only), 23.1/71.6 h for cefsulodin, 40.6/57.9 h for doripenem, 46.5/64.6 h for meropenem, 50.8/97.7 h for cefepime, 61.5/99.5 h for piperacillin, and >120 h for all other compounds. Broth stability decreased at higher pH. All drugs were ≥90% stable for 72 h in agar at 4°C. Degradation half-lives in water at 25°C were >200 h for all drugs except imipenem (14.7 h, at 1,000 mg/L) and doripenem (59.5 h). One imipenem supplement dose allowed concentrations to stay within ±31% of their target concentration. This study provides comprehensive stability data on ß-lactams and BLIs in relevant in vitro media using LC-MS/MS. Future studies are warranted applying these data to antimicrobial susceptibility testing and assessing the impact of ß-lactamase-related degradation.

Present and future of resistance in Pseudomonas aeruginosa: implications for treatment.

Pseudomonas aeruginosa is a pathogen that has a high propensity to develop antibiotic resistance, and the emergence of multidrug-resistant strains is a major concern for global health. The mortality rate associated with infections caused by this microorganism is significant, especially those caused by multidrug-resistant strains. The antibiotics used to treat these infections include quinolones, aminoglycosides, colistin, and ß-lactams. However, novel combinations of ß-lactams-ß-lactamase inhibitors and cefiderocol offer advantages over other members of their family due to their better activity against certain resistance mechanisms. Selecting the appropriate empiric antibiotic treatment requires consideration of the patient's clinical entity, comorbidities, and risk factors for multidrug-resistant pathogen infections, and local epidemiological data. Optimizing antibiotic pharmacokinetics, controlling the source of infection, and appropriate collection of samples are crucial for successful treatment. In the future, the development of alternative treatments and strategies, such as antimicrobial peptides, new antibiotics, phage therapy, vaccines, and colonization control, holds great promise for the management of P. aeruginosa infections.

DNA Nanoflower Eye Drops with Antibiotic-Resistant Gene Regulation Ability for MRSA Keratitis Target Treatment.

Methicillin-resistant Staphylococcus aureus (MRSA) biofilm-associated bacterial keratitis is highly intractable, with strong resistance to ß-lactam antibiotics. Inhibiting the MRSA resistance gene mecR1 to downregulate penicillin-binding protein PBP2a has been implicated in the sensitization of ß-lactam antibiotics to MRSA. However, oligonucleotide gene regulators struggle to penetrate dense biofilms, let alone achieve efficient gene regulation inside bacteria cells. Herein, an eye-drop system capable of penetrating biofilms and targeting bacteria for chemo-gene therapy in MRSA-caused bacterial keratitis is developed. This system employed rolling circle amplification to prepare DNA nanoflowers (DNFs) encoding MRSA-specific aptamers and mecR1 deoxyribozymes (DNAzymes). Subsequently, ß-lactam antibiotic ampicillin (Amp) and zinc oxide (ZnO) nanoparticles are sequentially loaded into the DNFs (ZnO/Amp@DNFs). Upon application, ZnO on the surface of the nanosystem disrupts the dense structure of biofilm and fully exposes free bacteria. Later, bearing encoded aptamer, the nanoflower system is intensively endocytosed by bacteria, and releases DNAzyme under acidic conditions to cleave the mecR1 gene for PBP2a down-regulation, and ampicillin for efficient MRSA elimination. In vivo tests showed that the system effectively cleared bacterial and biofilm in the cornea, suppressed proinflammatory cytokines interleukin 1ß ï¼ˆIL-1ß） and tumor neocrosis factor-alpha （TNF-α）, and is safe for corneal epithelial cells. Overall, this design offers a promising approach for treating MRSA-induced keratitis.

Amoxicillin therapeutic drug monitoring for endocarditis: A comparative study (EI-STAB).

INTRODUCTION: International guidelines recommend high doses of ß-lactams for most cases of infective endocarditis (IE). Therapeutic drug monitoring (TDM) is increasingly used to adjust ß-lactam dose based on plasma concentrations, although there are no comparative studies to support this practice. The benefit of amoxicillin TDM during IE was evaluated. METHODS: An observational, retrospective, cohort study of adults treated with high-dose amoxicillin for enterococcal or streptococcal IE was conducted in two referral centers. Patients with, or without TDM were compared. The primary outcome was mean daily amoxicillin dose. RESULTS: A total of 206 cases of streptococcal (n=140, 68%) or enterococcal (n=66, 32%) IE were included. IE occurred on prosthetic valves in 77 (37%) cases, and on intracardiac devices in 28 (14%) cases. Aortic valve was involved in 136 (66%) cases. There were 154 men (75%), mean age was 70 ± 14 years, valve surgery was performed in 81/206 (39%) patients, and in-hospital mortality was 8% (17/206). All patients in the TDM group and most patients in the group without TDM received amoxicillin as continuous infusion. Amoxicillin TDM was performed for 114 patients (55.3%), with a mean of 4.7 ± 2.3 measures per patient, a mean plasma steady-state concentration of 41.2 ± 19 mg/L, most (82/114, 72%) being within the therapeutic target (20-80 mg/L). Mean amoxicillin dose was lower in patients with TDM (10.0 ± 3.3 g/day) than those without TDM (11.3 ± 2.0 g/day) (P=0.003). CONCLUSION: Amoxicillin TDM was associated with a reduction in daily doses, with no impact on adverse events and prognosis. Individualized treatment of IE through TDM may contribute to decreased use of antibiotics.

Mycobacterium abscessus Infections in Cystic Fibrosis Individuals: A Review on Therapeutic Options.

Mycobacterium abscessus is an opportunistic pathogen that mainly colonizes and infects cystic fibrosis patients' lungs. M. abscessus is naturally resistant to many antibiotics such as rifamycin, tetracyclines and ß-lactams. The current therapeutic regimens are not very effective and are mostly based on repurposed drugs used against Mycobacterium tuberculosis infections. Thus, new approaches and novel strategies are urgently needed. This review aims to provide an overview of the latest ongoing findings to fight M. abscessus infections by analyzing emerging and alternative treatments, novel drug delivery strategies, and innovative molecules.

A conserved zinc-binding site in Acinetobacter baumannii PBP2 required for elongasome-directed bacterial cell shape.

Acinetobacter baumannii is a gram-negative bacterial pathogen that causes challenging nosocomial infections. ß-lactam targeting of penicillin-binding protein (PBP)-mediated cell wall peptidoglycan (PG) formation is a well-established antimicrobial strategy. Exposure to carbapenems or zinc (Zn)-deprived growth conditions leads to a rod-to-sphere morphological transition in A. baumannii, an effect resembling that caused by deficiency in the RodA-PBP2 PG synthesis complex required for cell wall elongation. While it is recognized that carbapenems preferentially acylate PBP2 in A. baumannii and therefore block the transpeptidase function of the RodA-PBP2 system, the molecular details underpinning cell wall elongation inhibition upon Zn starvation remain undefined. Here, we report the X-ray crystal structure of A. baumannii PBP2, revealing an unexpected Zn coordination site in the transpeptidase domain required for protein stability. Mutations in the Zn-binding site of PBP2 cause a loss of bacterial rod shape and increase susceptibility to ß-lactams, therefore providing a direct rationale for cell wall shape maintenance and Zn homeostasis in A. baumannii. Furthermore, the Zn-coordinating residues are conserved in various ß- and γ-proteobacterial PBP2 orthologs, consistent with a widespread Zn-binding requirement for function that has been previously unknown. Due to the emergence of resistance to virtually all marketed antibiotic classes, alternative or complementary antimicrobial strategies need to be explored. These findings offer a perspective for dual inhibition of Zn-dependent PG synthases and metallo-ß-lactamases by metal chelating agents, considered the most sought-after adjuvants to restore ß-lactam potency against gram-negative bacteria.

In-Silico molecular screening of natural compounds as a potential therapeutic inhibitor for Methicillin-resistant Staphylococcus aureus inhibition.

Methicillin-resistant Staphylococcus aureus (MRSA) is a life-threatening superbug causing infectious diseases such as pneumonia, endocarditis, osteomyelitis, etc. Conventional antibiotics are ineffective against MRSA infections due to their resistance mechanism against the antibiotics. The Penicillin Binding Protein (PBP2a) inhibits the activity of antibiotics by hydrolyzing the ß-lactam ring. Thus, alternate treatment methods are needed for the treatment of MRSA infections. Natural bioactive compounds exhibit good inhibition efficiency against MRSA infections by hindering its enzymatic mechanism, efflux pump system, etc. The present work deals with identifying potential and non-toxic natural bioactive compounds (ligands) through molecular docking studies through StarDrop software. Various natural bioactive compounds which are effective against MRSA infections were docked with the protein (6VVA). The ligands having good binding energy values and pharmacokinetic and drug-likeness properties have been illustrated as potential ligands for treating MRSA infections. From this exploration, Luteolin, Kaempferol, Chlorogenic acid, Sinigrin, Zingiberene, 1-Methyl-4-(6-methylhepta-1,5-dien-2-yl)cyclohex-1-ene, and Curcumin have found with good binding energies of -8.6 kcal/mol, -8.4 kcal/mol, -8.2 kcal/mol, -7.5 kcal/mol, -7.4 kcal/mol, -7.3 kcal/mol, and -7.2 kcal/mol, respectively.

Jumping into the future: overcoming pharmacokinetic/pharmacodynamic hurdles to optimize the treatment of severe difficult to treat-Gram-negative infections with novel beta-lactams.

INTRODUCTION: The choice of best therapeutic strategy for difficult-to-treat resistance (DTR) Gram-negative infections currently represents an unmet clinical need. AREAS COVERED: This review provides a critical reappraisal of real-world evidence supporting the role of pharmacokinetic/pharmacodynamic (PK/PD) optimization of novel beta-lactams in the management of DTR Gram-negative infections. The aim was to focus on prolonged and/or continuous infusion administration, penetration rates into deep-seated infections, and maximization of PK/PD targets in special renal patient populations. Retrieved findings were applied to the three most critical clinical scenarios of Gram-negative resistance phenotypes (i.e. carbapenem-resistant Enterobacterales; difficult-to-treat resistant Pseudomonas aeruginosa, and carbapenem-resistant Acinetobacter baumannii). EXPERT OPINION: Several studies supported the role of PK/PD optimization of beta-lactams in the management of DTR Gram-negative infections for both maximizing clinical efficacy and preventing resistance emergence. Optimizing antimicrobial therapy with novel beta-lactams based on the so called 'antimicrobial therapy puzzle' PK/PD concepts may represent a definitive jump into the future toward a personalized patient management of DTR Gram negative infections. Establishing a dedicated and coordinated multidisciplinary team and implementing a real-time TDM-guided personalized antimicrobial exposure optimization of novel beta-lactams based on expert clinical pharmacological interpretation, could represent crucial cornerstones for the proper management of DTR Gram-negative infections.

Purine Nucleosides Interfere with c-di-AMP Levels and Act as Adjuvants To Re-Sensitize MRSA To ß-Lactam Antibiotics.

The purine-derived signaling molecules c-di-AMP and (p)ppGpp control mecA/PBP2a-mediated ß-lactam resistance in methicillin-resistant Staphylococcus aureus (MRSA) raise the possibility that purine availability can control antibiotic susceptibility. Consistent with this, exogenous guanosine and xanthosine, which are fluxed through the GTP branch of purine biosynthesis, were shown to significantly reduce MRSA ß-lactam resistance. In contrast, adenosine (fluxed to ATP) significantly increased oxacillin resistance, whereas inosine (which can be fluxed to ATP and GTP via hypoxanthine) only marginally increased oxacillin susceptibility. Furthermore, mutations that interfere with de novo purine synthesis (pur operon), transport (NupG, PbuG, PbuX) and the salvage pathway (DeoD2, Hpt) increased ß-lactam resistance in MRSA strain JE2. Increased resistance of a nupG mutant was not significantly reversed by guanosine, indicating that NupG is required for guanosine transport, which is required to reduce ß-lactam resistance. Suppressor mutants resistant to oxacillin/guanosine combinations contained several purine salvage pathway mutations, including nupG and hpt. Guanosine significantly increased cell size and reduced levels of c-di-AMP, while inactivation of GdpP, the c-di-AMP phosphodiesterase negated the impact of guanosine on ß-lactam susceptibility. PBP2a expression was unaffected in nupG or deoD2 mutants, suggesting that guanosine-induced ß-lactam susceptibility may result from dysfunctional c-di-AMP-dependent osmoregulation. These data reveal the therapeutic potential of purine nucleosides, as ß-lactam adjuvants that interfere with the normal activation of c-di-AMP are required for high-level ß-lactam resistance in MRSA. IMPORTANCE The clinical burden of infections caused by antimicrobial resistant (AMR) pathogens is a leading threat to public health. Maintaining the effectiveness of existing antimicrobial drugs or finding ways to reintroduce drugs to which resistance is widespread is an important part of efforts to address the AMR crisis. Predominantly, the safest and most effective class of antibiotics are the ß-lactams, which are no longer effective against methicillin-resistant Staphylococcus aureus (MRSA). Here, we report that the purine nucleosides guanosine and xanthosine have potent activity as adjuvants that can resensitize MRSA to oxacillin and other ß-lactam antibiotics. Mechanistically, exposure of MRSA to these nucleosides significantly reduced the levels of the cyclic dinucleotide c-di-AMP, which is required for ß-lactam resistance. Drugs derived from nucleotides are widely used in the treatment of cancer and viral infections highlighting the clinical potential of using purine nucleosides to restore or enhance the therapeutic effectiveness of ß-lactams against MRSA and potentially other AMR pathogens.

In vitro and computational studies of the ß-lactamase inhibition and ß-lactam potentiating properties of plant secondary metabolites.

ß-lactam resistance in bacteria is primarily mediated through the production of ß-lactamases. Among the several strategies explored to mitigate the issue of ß-lactam resistance, the use of plant secondary metabolites in combination with existing ß-lactams seem promising. The present study aims to identify possible ß-lactam potentiating plant secondary metabolites following in vitro and in silico approaches. Among 180 extracts from selected 30 medicinal plants, acetone extract of Ficus religiosa (FRAE) bark recorded the least IC50 value of 3.9 mg/ml. Under in vitro conditions, FRAE potentiated the activity of ampicillin, which was evidenced by the significant reduction in IC50 values of ampicillin against multidrug resistant bacteria. Metabolic profiling following HR-LCMS analysis revealed the presence of diverse metabolites viz. flavonoids, alkaloids, terpenoids, etc. in FRAE. Further, ensemble docking of the FRAE metabolites against four Class A ß-lactamase (SHV1, TEM1, KPC2 and CTX-M-27) showed quercetin, taxifolin, myricetin, luteolin, and miquelianin as potential inhibitors with the least average binding energy. In molecular dynamic simulation studies, myricetin formed the most stable complex with SHV1 and KPC-2 while miquelianin with TEM1 and CTX-M-27. Further, all five metabolites interacted with amino acid residue Glu166 in Ω loop of ß-lactamase, interfering with the deacylation step, thereby disrupting the enzyme activity. The pharmacokinetics and ADMET profile indicate their drug-likeness and non-toxic nature, making them ideal ß-lactam potentiators. This study highlights the ability of metabolites present in FRAE to act as ß-lactamase inhibitors.Communicated by Ramaswamy H. Sarma.

Low attainment to PK/PD-targets for ß-lactams in a multi-center study on the first 72 h of treatment in ICU patients.

Severe infections are life-threatening conditions commonly seen in the intensive care units (ICUs). Antibiotic treatment with adequate concentrations is of great importance during the first days when the bacterial load is the highest. Therapeutic drug monitoring (TDM) of ß-lactam antibiotics has been suggested to monitor target attainment and to improve the outcome. This prospective multi-center study in seven ICUs in Sweden investigated pharmacokinetic/pharmacodynamic-target (PK/PD-target) attainment for cefotaxime, piperacillin-tazobactam and meropenem, commonly used ß-lactams in Sweden. A mid-dose and trough antibiotic concentration blood sample were taken from patients with severe infection daily during the first 72 h of treatment. Antibiotic plasma concentrations were analysed by liquid chromatography-mass spectrometry (LC-MS). Antibiotic concentrations 100% time above MIC (minimal inhibitory concentration), (100% T > MIC) and four times above MIC 50% of the time (50% T > 4xMIC) were used as PK/PD-targets. We included 138 patients with the median age of 67 years and the median Simplified Acute Physiology Score 3 (SAPS3) of 59. Forty-five percent of the study-population failed to reach 100% T > MIC during the first day of treatment. The results were similar the following two days. There was a three-fold risk of not meeting the PK/PD target if the patient was treated with cefotaxime. For the cefotaxime treated patients 8 out of 55 (15%) had at least one end-dose concentrations below the level of detection during the study. Low age, low illness severity, low plasma creatinine, lower respiratory tract infection and cefotaxime treatment were risk factors for not reaching 100% T > MIC. In Swedish ICU-patients treated with ß-lactam antibiotics, a high proportion of patients did not reach the PK/PD target. TDM could identify patients that need individual higher dosing regimens already on the first day of treatment. Further studies on optimal empirical start dosing of ß-lactams, especially for cefotaxime, in the ICU are needed.Trial registration: The protocol was retrospectively registered 100216 (ACTRN12616000167460).

Postexposure Prophylaxis and Treatment of Bacillus anthracis Infections: A Systematic Review and Meta-analyses of Animal Models, 1947-2019.

BACKGROUND: Anthrax is endemic to many countries, including the United States. The causative agent, Bacillus anthracis, poses a global bioterrorism threat. Without effective antimicrobial postexposure prophylaxis (PEPAbx) and treatment, the mortality of systemic anthrax is high. To inform clinical guidelines for PEPAbx and treatment of B. anthracis infections in humans, we systematically evaluated animal anthrax treatment model studies. METHODS: We searched for survival outcome data in 9 scientific search engines for articles describing antimicrobial PEPAbx or treatment of anthrax in animals in any language through February 2019. We performed meta-analyses of efficacy of antimicrobial PEPAbx and treatment for each drug or drug combination using random-effects models. Pharmacokinetic/pharmacodynamic relationships were developed for 5 antimicrobials with available pharmacokinetic data. Monte Carlo simulations were used to predict unbound drug exposures in humans. RESULTS: We synthesized data from 34 peer-reviewed studies with 3262 animals. For PEPAbx and treatment of infection by susceptible B. anthracis, effective monotherapy can be accomplished with fluoroquinolones, tetracyclines, ß-lactams (including penicillin, amoxicillin-clavulanate, and imipenem-cilastatin), and lipopeptides or glycopeptides. For naturally occurring strains, unbound drug exposures in humans were predicted to adequately cover the minimal inhibitory concentrations (MICs; those required to inhibit the growth of 50% or 90% of organisms [MIC50 or MIC90]) for ciprofloxacin, levofloxacin, and doxycycline for both the PEPAbx and treatment targets. Dalbavancin covered its MIC50 for PEPAbx. CONCLUSIONS: These animal studies show many reviewed antimicrobials are good choices for PEPAbx or treatment of susceptible B. anthracis strains, and some are also promising options for combating resistant strains. Monte Carlo simulations suggest that oral ciprofloxacin, levofloxacin, and doxycycline are particularly robust choices for PEPAbx or treatment.

Identification of natural inhibitor against L1 ß-lactamase present in Stenotrophomonas maltophilia.

Antibiotic resistance is threatening the medical industry in treating microbial infections. Many organisms are acquiring antibiotic resistance because of the continuous use of the same drug. Gram-negative organisms are developing multi-drug resistance properties (MDR) due to chromosomal level changes that occurred as a part of evolution or some intrinsic factors already present in the organism. Stenotrophomonas maltophilia falls under the category of multidrug-resistant organism. WHO has also urged to evaluate the scenario and develop new strategies for making this organism susceptible to otherwise resistant antibiotics. Using novel compounds as drugs can ameliorate the issue to some extent. The ß-lactamase enzyme in the bacteria is responsible for inhibiting several drugs currently being used for treatment. This enzyme can be targeted to find an inhibitor that can inhibit the enzyme activity and make the organism susceptible to ß-lactam antibiotics. Plants produce several secondary metabolites for their survival in adverse environments. Several phytoconstituents have antimicrobial properties and have been used in traditional medicine for a long time. The computational technologies can be exploited to find the best compound from many compounds. Virtual screening, molecular docking, and dynamic simulation methods are followed to get the best inhibitor for L1 ß-lactamase. IMPPAT database is screened, and the top hit compounds are studied for ADMET properties. Finally, four compounds are selected to set for molecular dynamics simulation. After all the computational calculations, withanolide R is found to have a better binding and forms a stable complex with the protein. This compound can act as a potent natural inhibitor for L1 ß-lactamase.

Resistance to beta-lactams in Gram-negative bacilli: relevance and potential therapeutic alternatives.

The indiscriminate and massive antibiotic use in the clinical practice and in agriculture or cattle during the past few decades has produced a serious world health problem that entails high morbidity and mortality: the antibiotic multi-drug resistance. In 2017 and 2019, the World Health Organization published a list of urgent threats and priorities in the context of drug resistance, which only included Gram-negative bacteria and specially focused on carbapenem-resistant Acinetobacter baumannii and Pseudomonas aeruginosa, as well as carbapenem and third generation cephalosporin-resistant Enterobacteriaceae. This scenario emphasizes the need of developing and testing new antibiotics from different families, such as new beta-lactams, highlighting cefiderocol and its original mechanism of action; new beta-lactamase inhibitors, with vaborbactam or relebactam among others; new quinolones such as delafloxacin, and also omadacycline or eravacycline, as members of the tetracycline family. The present work reviews the importance and impact of Gram-negative bacterial infections and their resistance mechanisms, and analyzes the current therapeutic paradigm as well as the role of new antibiotics with a promising future in the era of multi and pan-drug resistance.

Targeted AntiBiotics for Chronic pulmonary diseases (TARGET ABC): can targeted antibiotic therapy improve the prognosis of Pseudomonas aeruginosa-infected patients with chronic pulmonary obstructive disease, non-cystic fibrosis bronchiectasis, and asthma? A multicenter, randomized, controlled, open-label trial.

BACKGROUND: Pseudomonas aeruginosa infection is seen in chronic pulmonary disease and is associated with exacerbations and poor long-term prognosis. However, evidence-based guidelines for the management and treatment of P. aeruginosa infection in chronic, non-cystic fibrosis (CF) pulmonary disease are lacking. The aim of this study is to investigate whether targeted antibiotic treatment against P. aeruginosa can reduce exacerbations and mortality in patients with chronic obstructive pulmonary disease (COPD), non-CF bronchiectasis, and asthma. METHODS: This study is an ongoing multicenter, randomized, controlled, open-label trial. A total of 150 patients with COPD, non-CF bronchiectasis or asthma, and P. aeruginosa-positive lower respiratory tract samples will be randomly assigned with a 1:1 ratio to either no antibiotic treatment or anti-pseudomonal antibiotic treatment with intravenous beta-lactam and oral ciprofloxacin for 14 days. The primary outcome, analyzed with two co-primary endpoints, is (i) time to prednisolone and/or antibiotic requiring exacerbation or death, in the primary or secondary health sector, within days 20-365 from study allocation and (ii) days alive and without exacerbation within days 20-365 from the study allocation. DISCUSSION: This trial will determine whether targeted antibiotics can benefit future patients with chronic, non-CF pulmonary disease and P. aeruginosa infection in terms of reduced morbidity and mortality, thus optimizing therapeutic approaches in this large group of chronic patients. TRIAL REGISTRATION: ClinicalTrials.gov NCT03262142 . Registered on August 25, 2017.

Strongly Bactericidal All-Oral ß-Lactam Combinations for the Treatment of Mycobacterium abscessus Lung Disease.

Bioactive forms of oral ß-lactams were screened in vitro against Mycobacterium abscessus with and without the bioactive form of the oral ß-lactamase inhibitor avibactam ARX1796. Sulopenem was equally active without avibactam, while tebipenem, cefuroxime, and amoxicillin required avibactam for optimal activity. Systematic pairwise combination of the four ß-lactams revealed strong bactericidal synergy for each of sulopenem, tebipenem, and cefuroxime combined with amoxicillin in the presence of avibactam. These all-oral ß-lactam combinations warrant clinical evaluation.

Optimal dose of lactoferrin reduces the resilience of in vitro Staphylococcus aureus colonies.

The rise in antibiotic resistance has stimulated research into adjuvants that can improve the efficacy of broad-spectrum antibiotics. Lactoferrin is a candidate adjuvant; it is a multifunctional iron-binding protein with antimicrobial properties. It is known to show dose-dependent antimicrobial activity against Staphylococcus aureus through iron sequestration and repression of ß-lactamase expression. However, S. aureus can extract iron from lactoferrin through siderophores for their growth, which confounds the resolution of lactoferrin's method of action. We measured the minimum inhibitory concentration (MIC) for a range of lactoferrin/ ß-lactam antibiotic dose combinations and observed that at low doses (< 0.39 µM), lactoferrin contributes to increased S. aureus growth, but at higher doses (> 6.25 µM), iron-depleted native lactoferrin reduced bacterial growth and reduced the MIC of the ß-lactam-antibiotic cefazolin. This differential behaviour points to a bacterial population response to the lactoferrin/ ß-lactam dose combination. Here, with the aid of a mathematical model, we show that lactoferrin stratifies the bacterial population, and the resulting population heterogeneity is at the basis of the dose dependent response seen. Further, lactoferrin disables a sub-population from ß-lactam-induced production of ß-lactamase, which when sufficiently large reduces the population's ability to recover after being treated by an antibiotic. Our analysis shows that an optimal dose of lactoferrin acts as a suitable adjuvant to eliminate S. aureus colonies using ß-lactams, but sub-inhibitory doses of lactoferrin reduces the efficacy of ß-lactams.

Application of pharmacokinetic/pharmacodynamic concepts to the development of treatment regimens for sporadic canine urinary tract infections: Challenges and paths forward.

Antimicrobial efficacy can be predicted based on infection site exposure to the antimicrobial agent relative to the in vitro susceptibility of the pathogen to that agent. When infections occur in soft tissues (e.g., muscle, blood, and ligaments), exposure at the infection site is generally assumed to reflect an equilibrium between the unbound concentrations in plasma and that in the interstitial fluids. In contrast, for sporadic urinary tract infections (UTIs) in dogs and uncomplicated UTIs in humans, the primary site of infection is the bladder wall. Infection develops when bacteria invade the host bladder urothelium (specifically, the umbrella cells that form the urine-contacting layer of the stratified uroepithelium) within which these bacteria can avoid exposure to host defenses and antimicrobial agents. Traditionally, pathogen susceptibility has been estimated using standardized in vitro tests that measure the minimal concentration that will inhibit pathogen growth (MIC). When using exposure-response relationships during drug development to explore dose optimization, these relationships can either be based upon an assessment of a correlation between clinical outcome, drug exposure at the infection site, and pathogen MIC, or upon benchmark exposure-response relationships (i.e., pharmacokinetic/pharmacodynamic indices) typically used for the various drug classes. When using the latter approach, it is essential that the unbound concentrations at the infection site be considered relative to the MIC within the biological matrix to which the pathogen will be exposed. For soft tissue infections, this typically is the unbound plasma concentrations versus MICs determined in standardized media such as cation-adjusted Mueller Hinton broth, which is how many indices were originally established. However, for UTIs, it is the unbound drug concentrations within the urine versus the MICs in the actual urine biophase that needs to be considered. The importance of these relationships and how they are influenced by drug resistance, resilience, and inoculum are discussed in this review using fluoroquinolones and beta-lactams as examples.