Combination Antimicrobial Treatment Versus Monotherapy: The Contribution of Meta-analyses

In-vitro evaluation of different antimicrobial combinations with and without colistin against carbapenem-resistant Acinetobacter baumannii clinical isolates

BACKGROUND

Carbapenem-resistant Acinetobacter baumannii (CRAB) infections are one of the most common causes of nosocomial infections and have high mortality rates due to difficulties in treatment. In this study, the in vitro synergistic interactions of the colistin (CT)-meropenem (MEM) combination and patient clinical outcomes were compared in CRAB-infected patients that receive CT-MEM antimicrobial combination therapy. In addition, in vitro synergistic interactions of MEM-ertapenem (ETP), MEM-fosfomycin (FF) and CT-FF antimicrobial combinations were investigated. Finally, the epsilometer (E) test and checkerboard test results were compared and the compatibility of these two tests was evaluated.

METHODS

Twenty-one patients were included in the study. Bacterial identification was performed with MALDI-TOF, and antimicrobial susceptibility was assessed with an automated system. Synergy studies were performed using the E test and checkerboard method.

RESULTS

For the checkerboard method, the synergy rates for CT-MEM, MEM-FF, MEM-ETP and CT-FF were 100%, 52.3%, 23.8% and 28.5%, respectively. In the E test synergy tests, synergistic effects were detected for two isolates each in the CT-MEM and CT-FF combinations. Microbial eradication was achieved in nine (52.9%) of the 17 patients that received CT-MEM combination therapy. The agreement between the E test and the checkerboard test was 6.5%.

CONCLUSIONS

A synergistic effect was found with the checkerboard method for the CT-MEM combination in all isolates in our study, and approximately 70% of the patients benefited from treatment with this combination. In addition, more than half of the isolates showed a synergistic effect for the MEM-FF combination. Combinations of CT-MEM and MEM-FF may be options for the treatment of CRAB infections. However, a comprehensive understanding of the potential of the microorganism to develop resistant mutants under applied exposures, as well as factors that directly affect antimicrobial activity, such as pharmacokinetics/pharmacodynamics, is essential for providing treatment advice. We found a low rate of agreement between the E test method and the checkerboard test method in our study, in contrast to the literature. Comprehensive studies that compare clinical results with methods are needed to determine the ideal synergy test and interpretation method.

A mechanistic assessment of the nature of pharmacodynamic drug-drug interaction in vivo and in vitro

Combination pharmacotherapy is becoming increasingly necessary because most diseases are pathophysiologically controlled at the subcellular level by target proteins in a combinatorial manner. We demonstrate the application of the stimulus-response mechanistic model in characterising the drug and physiological properties of pharmacodynamic drug-drug interactions (PDDI) using previously published in vitro and in vivo drug combination experiments. The in vitro experiment tested the effect of a combination of SCH66336 and 4-HPR on the survival of in squamous cell carcinoma cell lines, while the in vivo experiment tested the effect of a combination of cetuximab and cisplatin on tumour growth inhibition in female xenograft mice. The model adequately described both experiments, quantified both system and drug properties and predicted the nature of the PDDI mechanism. Strong baseline signals of 7.35 and 610 units existed in the in vitro and in vivo experiments respectively. An overall synergistic relationship (interaction index = 1.03E-8) was detected in the in vitro experiment. In the in vivo model, the overall interaction index was 70,139.45 implying an antagonistic interaction between the cisplatin and the cetuximab signals.

The activity and mechanism of vidofludimus as a potent enzyme inhibitor against NDM-1-positive E. coli

New Delhi metallo-β-lactamase-1 (NDM-1) is the most important and prevalent enzyme among all metallo-β-lactamases. NDM-1 can hydrolyze almost all-available β-lactam antibiotics including carbapenems, resulting in multidrug resistance, which poses an increasing clinical threat. However, there is no NDM-1 inhibitor approved for clinical treatment. Therefore, identifying a novel and potential enzyme inhibitor against NDM-1-mediated infections is an urgent need. In this study, vidofludimus was identified as a potential NDM-1 inhibitor by structure-based virtual screening and an enzyme activity inhibition assay. Vidofludimus significantly inhibited NDM-1 hydrolysis activity with a significant dose-dependent effect. When the vidofludimus concentration was 10 μg/ml, the inhibition rate and 50% inhibitory concentration were 93.3% and 13.8 ± 0.5 μM, respectively. In vitro, vidofludimus effectively restored the antibacterial activity of meropenem against NDM-1-positive Escherichia coli (E. coli), and the minimum inhibitory concentration of meropenem was decreased from 64 μg/ml to 4 μg/ml, a 16-fold reduction. The combination of vidofludimus and meropenem showed a significant synergistic effect with a fractional inhibitory concentration index of 0.125 and almost all the NDM-1-positive E. coli were killed within 12 h. Furthermore, the synergistic therapeutic effect of vidofludimus and meropenem in vivo was evaluated in mice infected with NDM-1 positive E. coli. Compared with the control treatment, vidofludimus combined with meropenem significantly improved the survival rate of mice infected with NDM-1-positive E. coli (P < 0.05), decreased the white blood cell count, the bacterial burden and inflammatory response induced by NDM-1-positive E. coli (P < 0.05), and alleviated histopathological damage in infected mice. It was demonstrated by molecular dynamic simulation, site-directed mutagenesis and biomolecular interaction that vidofludimus could interact directly with the key amino acids (Met67, His120, His122 and His250) and Zn²⁺ in the active site of NDM-1, thereby competitively inhibiting the hydrolysis activity of NDM-1 on meropenem. In summary, vidofludimus holds promise as anNDM-1 inhibitor, and the combination of vidofludimus and meropenem has potential as a therapeutic strategy for NDM-1-mediated infections.

Cellular Nanosponges for Biological Neutralization

Biological neutralization represents a general strategy that deploys therapeutic agents to bind with harmful molecules or infectious pathogens, block their bioactivity, and thus prevent them from causing the diseases. Here, a comprehensive review of using cell-membrane-coated nanoparticles, namely "cellular nanosponges," as host decoys for a wide range of biological neutralization applications is provided. Compared to traditional neutralization strategies, the cellular nanosponges stand out by mimicking susceptible host cells rather than accommodating the structures of the causative agents for the design of therapeutics. As all pathological agents must interact with host cells for bioactivity, nanosponges bypass the diversity of these agents and create function-driven and broad-spectrum neutralization solutions. The review focuses on the recent progress of using this new nanomedicine platform for neutralization against five primary pathological agents, including bacterial toxins, chemical toxicants, inflammatory cytokines, pathological antibodies, and viruses. Existing studies have established cellular nanosponges as versatile tools for biological neutralization. A thorough review of the cellular nanosponge technology is expected to inspire more refined cellular nanosponge designs and unique neutralization applications to address unsolved medical problems.

Synergistic Inhibitory Effect of Polymyxin B in Combination with Ceftazidime against Robust Biofilm Formed by Acinetobacter baumannii with Genetic Deficiency in AbaI/AbaR Quorum Sensing

Carbapenem resistance of Acinetobacter baumannii poses challenges to public health. Biofilm contributes to the persistence of A. baumannii cells. This study was designed to investigate the genetic relationships among carbapenem resistance, polymyxin resistance, multidrug resistance, biofilm formation, and surface-associated motility and evaluate the antibiofilm effect of polymyxin in combination with other antibiotics. A total of 103 clinical A. baumannii strains were used to determine antibiotic susceptibility, biofilm formation capacity, and motility. Enterobacterial repetitive intergenic consensus (ERIC)-PCR fingerprinting was used to determine the genetic variation among strains. The distribution of 17 genes related to the resistance-nodulation-cell division (RND)-type efflux, autoinducer-receptor (AbaI/AbaR) quorum sensing, oxacillinases (OXA)-23, and insertion sequence of ISAba1 element was investigated. The representative strains were chosen to evaluate the gene transcription and the antibiofilm activity by polymyxin B (PB) in combination with merapenem, levofloxacin, and ceftazidime, respectively. ERIC-PCR-dependent fingerprints were found to be associated with carbapenem resistance and multidrug resistance. The presence of bla_OXA-23 was found to correlate with genes involved in ISAba1 insertion, AbaI/AbaR quorum sensing, and AdeABC efflux. Carbapenem resistance was observed to be negatively correlated with biofilm formation and positively correlated with motility. PB in combination with ceftazidime displayed a synergistic antibiofilm effect against robust biofilm formed by an A. baumannii strain with deficiency in AbaI/AbaR quorum sensing. Our results not only clarify the genetic correlation among carbapenem resistance, biofilm formation, and pathogenicity in a certain level but also provide a theoretical basis for clinical applications of polymyxin-based combination of antibiotics in antibiofilm therapy. IMPORTANCE Deeper explorations of molecular correlation among antibiotic resistance, biofilm formation, and pathogenicity could provide novel insights that would facilitate the development of therapeutics and prevention against A. baumannii biofilm-related infections. The major finding that polymyxin B in combination with ceftazidime displayed a synergistic antibiofilm effect against robust biofilm formed by an A. baumannii strain with genetic deficiency in AbaI/AbaR quorum sensing further provides a theoretical basis for clinical applications of antibiotics in combination with quorum quenching in antibiofilm therapy.

Duration of intravenous antibiotic treatment for acute exacerbations of cystic fibrosis: A systematic review: Duration of treatment for acute exacerbations of cystic fibrosis

BACKGROUND

Acute exacerbations of Cystic Fibrosis (AECF) are associated with significant morbidity. Recommendations are to treat for 2-3 weeks despite limited data. Spirometry is a measure of clinical response yet appears to plateau at 7-10 days. While durations <9 days have been associated with poorer outcomes, a duration of 10 days may be as effective as 14 days, potentially conferring advantages in terms of cost and adverse events. A 2019 Cochrane review by Abbott et al. did not identify any randomised controlled trials (RCT) comparing durations of treatment. Utilising data from non-randomised studies (NRS), we report a systematic review of intravenous antibiotic treatment, exploring changes in FEV₁ (Forced Expiratory Volume in 1 second), CRP (C-reactive protein) and peripheral WBC (white blood cell) count in studies with different treatment durations.

STUDY DESIGN AND METHODS

Systematic review of published literature following a search of MEDLINE, Embase, CINAHL and the Cochrane Clinical Trials register. Guidelines from the Preferred Reporting items for Systematic reviews and Meta-Analysis (PRISMA) and reporting Meta-analysis of Observational studies (MOOSE) statement were followed.

RESULTS

No randomised controlled trials were identified that specifically examined duration of treatment during AECF. This study included all relevant RCTs and also NRS, grouping according to study characteristics, such as length of treatment, location, year, and also characteristics of the patient population. 52 studies, comprising 79 subgroups, and 1,597 patients, were identified. Mean change (95%CI) in ppFEV₁ was 10.13 (9.21-11.05). There was no significant difference in change in ppFEV₁ for studies treating for 10-12 days; 8.85 (7.47-10.23), vs 13-15 days; 10.68 (9.53-11.82). Similar changes in CRP and WBC were seen irrespective of treatment duration.

CONCLUSION

This systematic review provides evidence that shorter durations of treatment may be associated with similar changes in FEV₁, CRP and WBC compared with longer durations.

Bacterial vaginosis: controversial issues

The purpose of the review. Consideration of the most controversial issues regarding the possibility of sexual transmission of BV-associated microorganisms (bacterias) in women and men. Basic provisions. Bacterial vaginosis (BV) is a common disease associated with an increased risk of contracting sexually transmitted infections (including human papillomavirus and human immunodeficiency virus) in women and their male sexual partners. BV is characterized by polymicrobial transformations caused by Gardnerella vaginalis, which is the main etiological microorganism of this disease. G. vaginalis has a proven ability to form microbial biofilms on the mucosal surface. As a rule, from 10 to 12 different G. vaginalis genotypes can simultaneously reside in one biofilm, which provides it with a longer lifespan and viability. It has been shown that microorganisms in the biofilm acquire properties that reduce sensitivity to standard etiotropic therapy even at high doses of antibiotics. It was found that the cause of BV is a polymicrobial gardnerella biofilm, all components of which are transferred as a whole (for example, with the help of key cells), including during sexual contact. In this regard, the article discusses the possibility of using a new term biofilm gardnerellosis, which more accurately reflects the essence of this problem. Microbial biofilms organized by G. vaginalis are found in a significant number of women with BV and their sexual partners.

Targeting the C-Terminal Domain Small Phosphatase 1

The human C-terminal domain small phosphatase 1 (CTDSP1/SCP1) is a protein phosphatase with a conserved catalytic site of DXDXT/V. CTDSP1’s major activity has been identified as dephosphorylation of the 5th Ser residue of the tandem heptad repeat of the RNA polymerase II C-terminal domain (RNAP II CTD). It is also implicated in various pivotal biological activities, such as acting as a driving factor in repressor element 1 (RE-1)-silencing transcription factor (REST) complex, which silences the neuronal genes in non-neuronal cells, G1/S phase transition, and osteoblast differentiation. Recent findings have denoted that negative regulation of CTDSP1 results in suppression of cancer invasion in neuroglioma cells. Several researchers have focused on the development of regulating materials of CTDSP1, due to the significant roles it has in various biological activities. In this review, we focused on this emerging target and explored the biological significance, challenges, and opportunities in targeting CTDSP1 from a drug designing perspective.

The "Old" and the "New" Antibiotics for MDR Gram-Negative Pathogens: For Whom, When, and How

The recent expansion of multidrug resistant and pan-drug-resistant pathogens poses significant challenges in the treatment of healthcare associated infections. An important advancement, is a handful of recently launched new antibiotics targeting some of the current most problematic Gram-negative pathogens, namely carbapenem-producing Enterobacteriaceae (CRE) and carbapenem-resistant P. aeruginosa (CRPA). Less options are available against carbapenem-resistant Acinetobacter baumannii (CRAB) and strains producing metallo-beta lactamases (MBL). Ceftazidime-avibactam signaled a turning point in the treatment of KPC and partly OXA- type carbapenemases, whereas meropenem-vaborbactam was added as a potent combination against KPC-producers. Ceftolozane-tazobactam could be seen as an ideal beta-lactam backbone for the treatment of CRPA. Plazomicin, an aminoglycoside with better pharmacokinetics and less toxicity compared to other class members, will cover important proportions of multi-drug resistant pathogens. Eravacycline holds promise in the treatment of infections by CRAB, with a broad spectrum of activity similar to tigecycline, and improved pharmacokinetics. Novel drugs and combinations are not to be considered "panacea" for the ongoing crisis in the therapy of XDR Gram-negative bacteria and colistin will continue to be considered as a fundamental companion drug for the treatment of carbapenem-resistant Enterobacteriaceae (particularly in areas where MBL predominate), for the treatment of CRPA (in many cases being the only in vitro active drug) as well as CRAB. Aminoglycosides are still important companion antibiotics. Finally, fosfomycin as part of combination treatment for CRE infections and P. aeruginosa, deserves a greater attention. Optimal conditions for monotherapy and the "when and how" of combination treatments integrating the novel agents will be discussed.

Nanoparticle-based local antimicrobial drug delivery

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

High-throughput identification and rational design of synergistic small-molecule pairs for combating and bypassing antibiotic resistance

Antibiotic-resistant infections kill approximately 23,000 people and cost $20,000,000,000 each year in the United States alone despite the widespread use of small-molecule antimicrobial combination therapy. Antibiotic combinations typically have an additive effect: the efficacy of the combination matches the sum of the efficacies of each antibiotic when used alone. Small molecules can also act synergistically when the efficacy of the combination is greater than the additive efficacy. However, synergistic combinations are rare and have been historically difficult to identify. High-throughput identification of synergistic pairs is limited by the scale of potential combinations: a modest collection of 1,000 small molecules involves 1 million pairwise combinations. Here, we describe a high-throughput method for rapid identification of synergistic small-molecule pairs, the overlap2 method (O2M). O2M extracts patterns from chemical-genetic datasets, which are created when a collection of mutants is grown in the presence of hundreds of different small molecules, producing a precise set of phenotypes induced by each small molecule across the mutant set. The identification of mutants that show the same phenotype when treated with known synergistic molecules allows us to pinpoint additional molecule combinations that also act synergistically. As a proof of concept, we focus on combinations with the antibiotics trimethoprim and sulfamethizole, which had been standard treatment against urinary tract infections until widespread resistance decreased efficacy. Using O2M, we screened a library of 2,000 small molecules and identified several that synergize with the antibiotic trimethoprim and/or sulfamethizole. The most potent of these synergistic interactions is with the antiviral drug azidothymidine (AZT). We then demonstrate that understanding the molecular mechanism underlying small-molecule synergistic interactions allows the rational design of additional combinations that bypass drug resistance. Trimethoprim and sulfamethizole are both folate biosynthesis inhibitors. We find that this activity disrupts nucleotide homeostasis, which blocks DNA replication in the presence of AZT. Building on these data, we show that other small molecules that disrupt nucleotide homeostasis through other mechanisms (hydroxyurea and floxuridine) also act synergistically with AZT. These novel combinations inhibit the growth and virulence of trimethoprim-resistant clinical Escherichia coli and Klebsiella pneumoniae isolates, suggesting that they may be able to be rapidly advanced into clinical use. In sum, we present a generalizable method to screen for novel synergistic combinations, to identify particular mechanisms resulting in synergy, and to use the mechanistic knowledge to rationally design new combinations that bypass drug resistance.

Polymyxin B in combination with doripenem against heteroresistant Acinetobacter baumannii: pharmacodynamics of new dosing strategies

OBJECTIVES

Polymyxin B is being increasingly utilized as a last resort against resistant Gram-negative bacteria. We examined the pharmacodynamics of novel dosing strategies for polymyxin B combinations to maximize efficacy and minimize the emergence of resistance and drug exposure against Acinetobacter baumannii.

METHODS

The pharmacodynamics of polymyxin B together with doripenem were evaluated in time-kill experiments over 48 h against 10⁸ cfu/mL of two polymyxin-heteroresistant A. baumannii isolates (ATCC 19606 and N16870). Pharmacokinetic/pharmacodynamic relationships were mathematically modelled using S-ADAPT. A hollow-fibre infection model (HFIM) was also used to simulate clinically relevant polymyxin B dosing strategies (traditional, augmented 'front-loaded' and 'burst' regimens), together with doripenem, against an initial inoculum of 10⁹ cfu/mL of ATCC 19606.

RESULTS

In static time-kill studies, polymyxin B concentrations >4 mg/L in combination with doripenem 25 mg/L resulted in rapid bactericidal activity against both strains with undetectable bacterial counts by 24 h. The mathematical model described the rapid, concentration-dependent killing as subpopulation and mechanistic synergy. In the HFIM, the traditional polymyxin B combination regimen was synergistic, with a >7.5 log₁₀ reduction by 48 h. The polymyxin B 'front-loaded' combination resulted in more rapid and extensive initial killing (>8 log₁₀) within 24 h, which was sustained over 10 days. With only 25% of the cumulative drug exposure, the polymyxin B 'burst' combination demonstrated antibacterial activity similar to traditional and 'front-loaded' combination strategies. The polymyxin B 'front-loaded' and 'burst' combination regimens suppressed the emergence of resistance.

CONCLUSIONS

Early aggressive dosing regimens for polymyxin combinations demonstrate promise for treatment of heteroresistant A. baumannii infections.

Empiric combination therapy for gram-negative bacteremia

BACKGROUND

Empirical combination antibiotic regimens consisting of a β-lactam and an aminoglycoside are frequently employed in the pediatric population. Data to demonstrate the comparative benefit of empirical β-lactam combination therapy relative to monotherapy for culture-proven Gram-negative bacteremia are lacking in the pediatric population.

METHODS

We conducted a retrospective cohort study of children treated for Gram-negative bacteremia at The Johns Hopkins Hospital from 2004 through 2012. We compared the estimated odds of 10-day mortality and the relative duration of bacteremia for children receiving empirical combination therapy versus empirical monotherapy using 1:1 nearest-neighbor propensity-score matching without replacement, before performing regression analysis.

RESULTS

We identified 226 matched pairs of patients well balanced on baseline covariates. Ten-day mortality was similar between the groups (odds ratio, 0.84; 95% confidence interval [CI], 0.28 to 1.71). Use of empirical combination therapy was not associated with a decrease in the duration of bacteremia (-0.51 days; 95% CI, -2.22 to 1.48 days). There was no survival benefit when evaluating 10-day mortality for the severely ill (pediatric risk of mortality III score ≥15) or profoundly neutropenic patients (absolute neutrophil count ≤100 cells/mL) receiving combination therapy. However, a survival benefit was observed when empirical combination therapy was prescribed for children growing multidrug-resistant Gram-negative organisms from the bloodstream (odds ratio, 0.70; 95% CI, 0.51 to 0.84).

CONCLUSIONS

Although there appears to be no advantage to the routine addition of an aminoglycoside to a β-lactam as empirical therapy for children who have Gram-negative bacteremia, children who have risk factors for MDRGN organisms appear to benefit from this practice.

Beta lactam antibiotic monotherapy versus beta lactam-aminoglycoside antibiotic combination therapy for sepsis

BACKGROUND

Optimal antibiotic treatment for sepsis is imperative. Combining a beta lactam antibiotic with an aminoglycoside antibiotic may provide certain advantages over beta lactam monotherapy.

OBJECTIVES

Our objectives were to compare beta lactam monotherapy versus beta lactam-aminoglycoside combination therapy in patients with sepsis and to estimate the rate of adverse effects with each treatment regimen, including the development of bacterial resistance to antibiotics.

SEARCH METHODS

In this updated review, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2013, Issue 11); MEDLINE (1966 to 4 November 2013); EMBASE (1980 to November 2013); LILACS (1982 to November 2013); and conference proceedings of the Interscience Conference of Antimicrobial Agents and Chemotherapy (1995 to 2013). We scanned citations of all identified studies and contacted all corresponding authors. In our previous review, we searched the databases to July 2004.

SELECTION CRITERIA

We included randomized and quasi-randomized trials comparing any beta lactam monotherapy versus any combination of a beta lactam with an aminoglycoside for sepsis.

DATA COLLECTION AND ANALYSIS

The primary outcome was all-cause mortality. Secondary outcomes included treatment failure, superinfections and adverse events. Two review authors independently collected data. We pooled risk ratios (RRs) with 95% confidence intervals (CIs) using the fixed-effect model. We extracted outcomes by intention-to-treat analysis whenever possible.

MAIN RESULTS

We included 69 trials that randomly assigned 7863 participants. Twenty-two trials compared the same beta lactam in both study arms, while the remaining trials compared different beta lactams using a broader-spectrum beta lactam in the monotherapy arm. In trials comparing the same beta lactam, we observed no difference between study groups with regard to all-cause mortality (RR 0.97, 95% CI 0.73 to 1.30) and clinical failure (RR 1.11, 95% CI 0.95 to 1.29). In studies comparing different beta lactams, we observed a trend for benefit with monotherapy for all-cause mortality (RR 0.85, 95% CI 0.71 to 1.01) and a significant advantage for clinical failure (RR 0.75, 95% CI 0.67 to 0.84). No significant disparities emerged from subgroup and sensitivity analyses, including assessment of participants with Gram-negative infection. The subgroup of Pseudomonas aeruginosa infections was underpowered to examine effects. Results for mortality were classified as low quality of evidence mainly as the result of imprecision. Results for failure were classified as very low quality of evidence because of indirectness of the outcome and possible detection bias in non-blinded trials. We detected no differences in the rate of development of resistance. Nephrotoxicity was significantly less frequent with monotherapy (RR 0.30, 95% CI 0.23 to 0.39). We found no heterogeneity for all these comparisons.We included a small subset of studies addressing participants with Gram-positive infection, mainly endocarditis. We identified no difference between monotherapy and combination therapy in these studies.

AUTHORS' CONCLUSIONS

The addition of an aminoglycoside to beta lactams for sepsis should be discouraged. All-cause mortality rates are unchanged. Combination treatment carries a significant risk of nephrotoxicity.

Escherichia coli resistance to nonbiocidal antibiofilm polysaccharides is rare and mediated by multiple mutations leading to surface physicochemical modifications

Antivirulence strategies targeting bacterial behavior, such as adhesion and biofilm formation, are expected to exert low selective pressure and have been proposed as alternatives to biocidal antibiotic treatments to avoid the rapid occurrence of bacterial resistance. Here, we tested this hypothesis using group 2 capsule polysaccharide (G2cps), a polysaccharidic molecule previously shown to impair bacterium-surface interactions, and we investigated the nature of bacterial resistance to a nonbiocidal antibiofilm strategy. We screened an Escherichia coli mutant library for an increased ability to form biofilm in the presence of G2cps, and we identified several mutants displaying partial but not total resistance to this antibiofilm polysaccharide. Our genetic analysis showed that partial resistance to G2cps results from multiple unrelated mutations leading to modifications in surface physicochemical properties that counteract the changes in ionic charge and Lewis base properties induced by G2cps. Moreover, some of the identified mutants harboring improved biofilm formation in the presence of G2cps were also partially resistant to other antibiofilm molecules. This study therefore shows that alterations of bacterial surface properties mediate only partial resistance to G2cps. It also experimentally validates the potential value of nonbiocidal antibiofilm strategies, since full resistance to antibiofilm compounds is rare and potentially unlikely to arise in clinical settings.

Liquiritigenin prevents Staphylococcus aureus-mediated lung cell injury via inhibiting the production of α-hemolysin

Staphylococcus aureus is a significant Gram-positive bacterium that is associated with a broad spectrum of diseases ranging from minor skin infections to lethal pneumonia, endocarditis, and toxinoses. α-Hemolysin is one of the most important exotoxins that contribute to the pathogenesis of S. aureus infections. Liquiritigenin is one of the most significant active components in licorice. In this study, hemolysis, western blot, and real-time reverse transcription-PCR assays were performed to investigate the impact of liquiritigenin on the production of S. aureus α-hemolysin. The results showed that low concentrations of liquiritigenin remarkably decreased S. aureus α-hemolysin production in a dose-dependent manner. Using live/dead cell staining and lactate dehydrogenase assays, we found that liquiritigenin could protect human lung cells (A549) from α-hemolysin-mediated injury. The data indicated that this compound could potentially be useful in developing drugs aiming at staphylococcal α-hemolysin.

Combination therapy for treatment of infections with gram-negative bacteria

Combination antibiotic therapy for invasive infections with Gram-negative bacteria is employed in many health care facilities, especially for certain subgroups of patients, including those with neutropenia, those with infections caused by Pseudomonas aeruginosa, those with ventilator-associated pneumonia, and the severely ill. An argument can be made for empiric combination therapy, as we are witnessing a rise in infections caused by multidrug-resistant Gram-negative organisms. The wisdom of continued combination therapy after an organism is isolated and antimicrobial susceptibility data are known, however, is more controversial. The available evidence suggests that the greatest benefit of combination antibiotic therapy stems from the increased likelihood of choosing an effective agent during empiric therapy, rather than exploitation of in vitro synergy or the prevention of resistance during definitive treatment. In this review, we summarize the available data comparing monotherapy versus combination antimicrobial therapy for the treatment of infections with Gram-negative bacteria.

Antibiotic heterogeneity optimizes antimicrobial prescription and enables resistant pathogen control in the intensive care unit

BACKGROUND

Multi-drug-resistant organisms (MDRO) complicate care increasingly on the general ward and in the emergency department, operating room, and intensive care unit (ICU). Whereas barrier precautions are important in limiting transmission of MDRO between patients, few tactics have been defined that reduce the genesis of MDRO.

METHOD

Review of pertinent English-language literature.

RESULTS

Antibiotic heterogeneity practices, as part of an overall antimicrobial drug stewardship program, offer one readily deployable means to reduce selection pressure for MDRO development in the ICU. The data underpinning this approach and data derived from its use indicate that, especially in surgical ICUs, heterogeneity of antibiotic prescribing can preserve or restore microbial ecology, reduce the prevalence of MDRO and the incidence of infections caused thereby, and facilitate the implementation and effectiveness of other antibiotic-sparing tactics, such as de-escalation.

CONCLUSION

Heterogeneity of antibiotic prescribing is effective in preventing the dissemination of MDRO pathogens.

Capsaicin protects mice from community-associated methicillin-resistant Staphylococcus aureus pneumonia

Background

α-toxin is one of the major virulence factors secreted by most Staphylococcus aureus strains, which played a central role in the pathogenesis of S. aureus pneumonia. The aim of this study was to investigate the impact of capsaicin on the production of α-toxin by community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strain USA 300 and to further assess its performance in the treatment of CA-MRSA pneumonia in a mouse model.

Methodology/Principal Findings

The in vitro effects of capsaicin on α-toxin production by S. aureus USA 300 were determined using hemolysis, western blot, and real-time RT-PCR assays. The influence of capsaicin on the α-toxin-mediated injury of human alveolar epithelial cells was determined using viability and cytotoxicity assays. Mice were infected intranasally with S. aureus USA300; the in vivo protective effects of capsaicin against S. aureus pneumonia were assessed by monitoring the mortality, histopathological changes and cytokine levels. Low concentrations of capsaicin substantially decreased the production of α-toxin by S. aureus USA 300 without affecting the bacterial viability. The addition of capsaicin prevented α-toxin-mediated human alveolar cell (A549) injury in co-culture with S. aureus. Furthermore, the in vivo experiments indicated that capsaicin protected mice from CA-MRSA pneumonia caused by strain USA 300.

Conclusions/Significance

Capsaicin inhibits the production of α-toxin by CA-MRSA strain USA 300 in vitro and protects mice from CA-MRSA pneumonia in vivo. However, the results need further confirmation with other CA-MRSA lineages. This study supports the views of anti-virulence as a new antibacterial approach for chemotherapy.

Pseudomonas aeruginosa bacteremia upon hospital admission: risk factors for mortality and influence of inadequate empirical antimicrobial therapy

Pseudomonas aeruginosa is an uncommon cause of bacteremia upon hospital admission (UHA) and the chosen empirical antimicrobial therapy may not cover it appropriately. In a multicenter prospective study conducted in Israel, we evaluated risk factors for in-hospital mortality in patients with P. aeruginosa bacteremia UHA and determined the influence of delay in adequate empirical antimicrobial therapy on patients' outcome. Seventy-six adult patients with P. aeruginosa bacteremia within 72 h of hospital admission were included. Demographic, clinical, and treatment data were collected. Microbiological adequacy of empirical therapy was determined. Severe sepsis or septic shock at admission (OR, 21.9; P < 0.001), respiratory or unknown sources of bacteremia (OR, 11.5; P = 0.003), recent hospitalization (OR, 6.2; P = 0.032), and poor functional status (OR, 5.8; P = 0.029) were identified as independent predictors of mortality. Inadequate empirical antimicrobial therapy was marginally associated with increased mortality only among patients who presented with severe sepsis or septic shock (P = 0.051).

Impact of multidrug-resistant Pseudomonas aeruginosa infection on patient outcomes

Rates of antibiotic resistance in Pseudomonas aeruginosa are increasing worldwide. The multidrug-resistant (MDR) phenotype in P. aeruginosa could be mediated by several mechanisms including multidrug efflux systems, enzyme production, outer membrane protein (porin) loss and target mutations. Currently, no international consensus on the definition of multidrug resistance exists, making direct comparison of the literature difficult. Inappropriate empirical therapy has been associated with increased mortality in P. aeruginosa infections; delays in starting appropriate therapy may contribute to increased length of hospital stay and persistence of infection. In addition, worse clinical outcomes may be associated with MDR infections owing to limited effective antimicrobial options. This article aims to summarize the contemporary literature on patient outcomes following infections caused by drug-resistant P. aeruginosa. The impact of antimicrobial therapy on patient outcomes, mortality and morbidity; and the economic impact of MDR P. aeruginosa infections will be examined.

[Febrile neutropenia in adult patients with solid tumours: a review of literature toward a rational and optimal management]

Chemotherapy-induced febrile neutropenia represents a frequent emergency and evidence based management of this event remains an exigency for each patient. Appropriate use of antibiotics is mandatory, growth factors have to be proposed according to validated guidelines and benefits and risks of antiobioprophylaxy must be discussed. This review propose to summarize available data on these important questions, with a special focus on this management of febrile neutropenia in daily practice.

Management of antibiotic resistance in the intensive care unit setting

Over the past few decades, an alarming increase of infections caused by antibiotic-resistant pathogens, including methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus species, carbapenem-resistant Pseudomonas aeruginosa, extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella spp., and multidrug-resistant Acinetobacter spp., has been observed, particularly in intensive care units. For clinicians, the rising resistance rate observed in nosocomial pathogens, when coupled with the lack of effective antimicrobials, represents the real challenge in the therapeutic management of critically ill patients. The contribution of clinicians in minimizing the increasing trend of resistance is represented by reduction of the patients' exposure to antibiotics, which reduces the resistance-selecting pressure, and by avoiding unnecessary antibiotic treatments. Recent issues on strategies to minimize resistance development and to appropriately manage critically ill patients with infections caused by multidrug-resistant organisms in the intensive care unit setting are discussed in this article.

Anti-virulence strategies to combat bacteria-mediated disease

Antibiotic resistance is one of the greatest challenges of the twenty-first century. However, the increasing understanding of bacterial pathogenesis and intercellular communication has revealed many potential strategies to develop novel drugs to treat bacteria-mediated disease. Interference with bacterial virulence and/or cell-to-cell signalling pathways is an especially compelling approach, as it is thought to apply less selective pressure for the development of bacterial resistance than traditional strategies, which are aimed at killing bacteria or preventing their growth. Here, we discuss the mechanisms of bacterial virulence and present promising anti-virulence strategies and compounds for the future treatment of bacterial infections.