Vancomycin acts synergistically with gentamicin against penicillin-resistant pneumococci by increasing the intracellular penetration of gentamicin

From the "One-Molecule, One-Target, One-Disease" Concept towards Looking for Multi-Target Therapeutics for Treating Non-Polio Enterovirus (NPEV) Infections

Non-polio enteroviruses (NPEVs), namely coxsackieviruses (CV), echoviruses (E), enteroviruses (EV), and rhinoviruses (RV), are responsible for a wide variety of illnesses. Some infections can progress to life-threatening conditions in children or immunocompromised patients. To date, no treatments have been approved. Several molecules have been evaluated through clinical trials without success. To overcome these failures, the multi-target directed ligand (MTDL) strategy could be applied to tackle enterovirus infections. This work analyzes registered clinical trials involving antiviral drugs to highlight the best candidates and develops filters to apply to a selection for MTDL synthesis. We explicitly stated the methods used to answer the question: which solution can fight NPEVs effectively? We note the originality and relevance of this proposal in relation to the state of the art in the enterovirus-inhibitors field. Several combinations are possible to broaden the antiviral spectrum and potency. We discuss data related to the virus and data related to each LEAD compound identified so far. Overall, this study proposes a perspective on different strategies to overcome issues identified in clinical trials and evaluate the "MTDL" potential to improve the efficacy of drugs, broaden the antiviral targets, possibly reduce the adverse effects, drug design costs and limit the selection of drug-resistant virus variants.

High Incidence of Acute Kidney Injury Following Antibiotic-Loaded Spacer Insertion for Periprosthetic Joint Infection: An Updated Review of the Literature

BACKGROUND

The use of antibiotic-impregnated cement during 2-stage revision arthroplasty for periprosthetic joint infection poses a risk of renal complications following spacer insertion. This systematic review aimed to investigate the rate of acute kidney injury (AKI) following antibiotic-loaded spacer insertion and to identify risk factors associated with this complication.

METHODS

A systematic review was performed using PubMed, Cochrane Central, and Scopus databases. All clinical studies that documented renal complications following antibiotic-loaded spacer insertion for periprosthetic knee (total knee arthroplasty [TKA]) or hip (total hip arthroplasty [THA]) infection were included. Articles that combined THA and TKA outcomes were also included and labeled "THA + TKA." Descriptive statistics were analyzed when data were available.

RESULTS

There were 24 studies (9 THA, 7 TKA, 8 THA + TKA) included. The mean incidences of spacer-related AKI across THA, TKA, and THA + TKA cohorts were 4.2 (range, 0 to 10%), 14 (range, 0 to 19%), and 27% (range, 0 to 35%), respectively. The most common patient-related risk factors for AKI were underlying chronic kidney disease or high baseline creatinine, low preoperative hemoglobin, and blood transfusion requirement. Spacer-related risk factors included high antibiotic dosage (>3.6 g/cement batch) and antibiotic type. While most recovered without complication, select patients required hemodialysis for acute management (2 THA, 18 THA + TKA) and/or developed chronic kidney disease (8 TKA, 8 THA).

CONCLUSION

The rate of AKI following spacer insertion was high and likely under-reported in the literature. Surgeons should be cognizant of this devastating complication and should closely monitor at-risk patients for AKI following antibiotic-loaded spacer insertion.

Impact of Antibiotic Prophylaxis on Surgical Site Infections in Cardiac Surgery

(1) Background: Cephalosporins (CA) are the first-line antibiotic prophylaxis recommended to prevent surgical site infection (SSI) after cardiac surgery. The combination of vancomycin/gentamicin (VGA) might represent a good alternative, but few studies have evaluated its efficacy in SSI prevention. (2) Methods: A single-centre retrospective study was conducted over a 13-year period in all consecutive adult patients undergoing elective cardiac surgery. Patients were stratified according to the type of antibiotic prophylaxis. CA served as the first-line prophylaxis, and VGA was used as the second-line prophylaxis. The primary endpoint was SSI occurrence at 90 days, which was defined as the need for reoperation due to SSI. (3) Results: In total, 14,960 adult patients treated consecutively from 2006 to 2019 were included in this study, of whom 1774 (12%) received VGA and 540 (3.7%) developed SSI. VGA patients had higher severity with increased 90-day mortality. Nevertheless, the frequency of SSI was similar between CA and VGA patients. However, the microbiological aetiologies were different, with more Gram-negative bacteria noted in the VGA group. (4) Conclusions: VGA seems to be as effective as CA in preventing SSI.

Antibiotics Treatment Modulates Microglia-Synapses Interaction

‘Dysbiosis’ of the adult gut microbiota, in response to challenges such as infection, altered diet, stress, and antibiotics treatment has been recently linked to pathological alteration of brain function and behavior. Moreover, gut microbiota composition constantly controls microglia maturation, as revealed by morphological observations and gene expression analysis. However, it is unclear whether microglia functional properties and crosstalk with neurons, known to shape and modulate synaptic development and function, are influenced by the gut microbiota. Here, we investigated how antibiotic-mediated alteration of the gut microbiota influences microglial and neuronal functions in adult mice hippocampus. Hippocampal microglia from adult mice treated with oral antibiotics exhibited increased microglia density, altered basal patrolling activity, and impaired process rearrangement in response to damage. Patch clamp recordings at CA3-CA1 synapses revealed that antibiotics treatment alters neuronal functions, reducing spontaneous postsynaptic glutamatergic currents and decreasing synaptic connectivity, without reducing dendritic spines density. Antibiotics treatment was unable to modulate synaptic function in CX3CR1-deficient mice, pointing to an involvement of microglia–neuron crosstalk through the CX3CL1/CX3CR1 axis in the effect of dysbiosis on neuronal functions. Together, our findings show that antibiotic alteration of gut microbiota impairs synaptic efficacy, suggesting that CX3CL1/CX3CR1 signaling supporting microglia is a major player in in the gut–brain axis, and in particular in the gut microbiota-to-neuron communication pathway.

Antimicrobial Peptides and their Multiple Effects at Sub-Inhibitory Concentrations

The frequent occurrence of multidrug-resistant strains to conventional antimicrobials has led to a clear decline in antibiotic therapies. Therefore, new molecules with different mechanisms of action are extremely necessary. Due to their unique properties, antimicrobial peptides (AMPs) represent a valid alternative to conventional antibiotics and many of them have been characterized for their activity and cytotoxicity. However, the effects that these peptides cause at concentrations below the minimum growth inhibitory concentration (MIC) have yet to be fully analyzed along with the underlying molecular mechanism. In this mini-review, the ability of AMPs to synergize with different antibiotic classes or different natural compounds is examined. Furthermore, data on microbial resistance induction are reported to highlight the importance of antibiotic resistance in the fight against infections. Finally, the effects that sub-MIC levels of AMPs can have on the bacterial pathogenicity are summarized while showing how signaling pathways can be valid therapeutic targets for the treatment of infectious diseases. All these aspects support the high potential of AMPs as lead compounds for the development of new drugs with antibacterial and immunomodulatory activities.

Ventriculoperitoneal shunt infection rates using a standard surgical technique, including topical and intraventricular vancomycin: the Children's Hospital Oakland experience

OBJECTIVE

Ventriculoperitoneal (VP) shunt infections are common complications after shunt operations. Despite the use of intravenous antibiotics, the incidence of infections remains high. Though antibiotic-impregnated catheters (AICs) are commonly used, another method of infection prophylaxis is the use of intraventricular (IVT) antibiotics. The authors describe their single-institution experience with a standard shunt protocol utilizing prophylactic IVT and topical vancomycin administration and report the incidence of pediatric shunt infections.

METHODS

Three hundred two patients undergoing VP shunt procedures with IVT and topical vancomycin between 2006 and 2016 were included. Patients were excluded if their age at surgery was greater than 18 years. Shunt operations were performed at a single institution following a standard shunt protocol implementing IVT and topical vancomycin. No AICs were used. Clinical data were retrospectively collected from the electronic health records.

RESULTS

Over the 11-year study period, 593 VP shunt operations were performed with IVT and topical vancomycin, and a total of 19 infections occurred (incidence 3.2% per procedure). The majority of infections (n = 10, 52.6%) were caused by Staphylococcus epidermidis. The median time to shunt infection was 3.7 weeks. On multivariate analysis, the presence of a CSF leak (OR 31.5 [95% CI 8.8-112.6]) and age less than 6 months (OR 3.6 [95% CI 1.2-10.7]) were statistically significantly associated with the development of a shunt infection. A post hoc analysis comparing infection rates after procedures that adhered to the shunt protocol and those that did not administer IVT and topical vancomycin, plus historical controls, revealed a difference in infection rates (3.2% vs 6.9%, p = 0.03).

CONCLUSIONS

The use of a standardized shunt operation technique that includes IVT and topical vancomycin is associated with a total shunt infection incidence of 3.2% per procedure, which compares favorably with the reported rates of shunt infection in the literature. The majority of infections occurred within 2 months of surgery and the most common causative organism was S. epidermidis. Young age (< 6 months) at the time of surgery and the presence of a postoperative CSF leak were statistically significantly associated with postoperative shunt infection on multivariate analysis. The results are hypothesis generating, and the authors propose that IVT and topical administration of vancomycin as part of a standardized shunt operation protocol may be an appropriate option for preventing pediatric shunt infections.

Design, synthesis, and discovery of novel oxindoles bearing 3-heterocycles as species-specific and combinatorial agents in eradicating Staphylococcus species

A series of new functionalized 3-indolylindolin-2-ones, 3-(1-methylpyrrol-2-yl)indolin-2-ones, and 3-(thiophen-2-yl)indolin-2-ones were synthesized by using novel indium (III)-catalysed reaction of various 3-diazoindolin-2-ones with indoles, 1-methylpyrrole, or thiophene via one-pot procedure. The newly synthesized compounds were characterized and screened for their in vitro antibacterial activity against various Staphylococcus species, including methicillin-resistant Staphylococcus aureus. results revealed that five compounds KS15, KS16, KS17, KS19, and KS20 exhibited potent and specific antibacterial activity against Staphylococcus species albeit inactive against Gram-negative bacteria. Especially, compounds exhibited superior antibacterial potency against Staphylococcus epidermidis compared to the reference drug streptomycin. The most potential compound KS16 also increased the susceptibility of Staphylococcus aureus to ciprofloxacin, gentamicin, kanamycin, and streptomycin. Among them, KS16 was found to be a synergistic compound with gentamicin and kanamycin. Furthermore, the cellular level of autolysin protein was increased from the KS16-treated Staphylococcus aureus cells. Finally, in vitro CCK-8 assays showed that KS16 exhibited no cytotoxicity at the minimum inhibitory concentrations used for killing Staphylococcus species. From all our results, novel oxindole compounds directly have lethal action or boost existing antibiotic power with the reduction of doses and toxicity in the treatment of multidrug-resistant Staphylococcus species.

[Local antibiotic therapy]

The treatment of superficial wound infections with local antibiotics is considered to be problematic as it is accompanied by an increased risk of resistance development and ineffectiveness in deeper regions. On the contrary, the local application of antibiotics is useful in arthroplasty and necessary if implants are utilized. The reason for this is the prevention of a rapid biofilm formation on foreign implants and a resulting infection may remain undiscovered until it becomes chronic. Apart from exogenous material, necrotic tissue (e. g. bone sequestra) provides suitable retreat areas for pathogens in the body. Because of the characteristics of bone and joint infections and an exceptional infection recurrence rate, a combined approach is required. Systemic antibiotic prophylaxis is able to reduce the number of pathogens acquired by perioperative contamination or hematogenic spread from another focus of infection; however, systemically applied antibiotics often fail to form an effective colonization barrier around the implant because their ability to penetrate the bone is relatively low. On the other hand, the high concentration of locally released antibiotics leads to an effective protection of the implant from bacteria in situ. Thus, for the treatment of implant-associated infections, systemic and local application of anti-infective agents is a reliable adjuvant measure that improves the therapeutic success. Polymethylmethacrylate (PMMA) bone cement is the most commonly used local drug carrier. Based on clinical and microbiological results, microbiologists and infectious disease experts together with the surgeon and pharmacist determine which anti-infective agents are indicated for systemic and local, PMMA cement-related application. Because there is no evident concept for the local application, unlike the recommendation for systemic use of anti-infective agents, this review article describes which aspects should be taken into account.

Purified citritin in combination with vancomycin inhibits VRE in vitro and in vivo

Gram-positive pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecium (VRE) have been frequently associated with bacterial resistance mechanisms. These mechanisms, in turn, restrict a range of therapeutic opportunities for the treatment of infections caused by these micro-organisms. Faced with this problem, the present study aims to isolate and characterize molecules with antimicrobial activity derived from the fungus Penicillium citrinum isolated from Cerrado soil. Furthermore, we also tested possible antibacterial potential alone and in combination with commercial antimicrobial agents. In this context, citrinin was isolated and characterized by nuclear magnetic resonance and electrospray ionization. Functional analyses showed MIC of 128 µg ml^-1 against S. aureus ATCC 25923, E. faecalis ATCC 29212 and a clinical isolate of vancomycin-resistant E. faecium (VRE01). However, for a clinical strain of methicillin-resistant S. aureus (MRSA01), the MIC was 256 µg ml^-1. In order to avoid such high concentrations and reduce the collateral effects, additive effects were evidenced by combining citrinin with cefoxitin against MRSA01 (FIC index=0.5) and also citrinin with vancomycin toward VRE01 (FIC index=0.5). In vivo studies with BALB/c-tipe mice (MRSA assay) demonstrated a clinical ineffectiveness of cefoxitin associated with citrinin (9.8 mg kg^-1 of cefoxitin +0.2 mg kg^-1 of citrinin), with this combination being inefficient to increase animal survival. However, the combination used in the treatment of VRE (23.5 mg kg^-1 of citrinin +1.5 mg kg^-1 of vancomycin) sepsis model was extremely promising, leading to an animal survival rate of 80 percent. In summary, our data show, for the first time, the possible successful use of citrinin associated with vancomycin for pathogenic bacteria control.

7,10-Epoxyoctadeca-7,9-dienoic Acid: A Small Molecule Adjuvant That Potentiates β-Lactam Antibiotics Against Multidrug-Resistant Staphylococcus aureus

The emergence of methicillin-resistant Staphylococcus aureus (MRSA) infections with multi-drug resistance needs effective and alternative control strategies. In this study we investigated the adjuvant effect of a novel furan fatty acid, 7,10-epoxyoctadeca-7,9-dienoic acid (7,10-EODA) against multidrug-resistant S. aureus (MDRSA) strain 01ST001 by disc diffusion, checker board and time kill assays. Further the membrane targeting action of 7,10-EODA was investigated by spectroscopic and confocal microscopic studies. 7,10-EODA exerted synergistic activity along with β-lactam antibiotics against all clinical MRSA strains, with a mean fractional inhibitory concentration index below 0.5. In time-kill kinetic study, combination of 7,10-EODA with oxacillin, ampicillin, and penicillin resulted in 3.8-4.2 log₁₀ reduction in the viable counts of MDRSA 01ST001. Further, 7,10-EODA dose dependently altered the membrane integrity (p < 0.001) and increased the binding of fluorescent analog of penicillin, Bocillin-FL to the MDRSA cells. The membrane action of 7,10-EODA further facilitated the uptake of several other antibiotics in MDRSA. The results of the present study suggested that 7,10-EODA could be a novel antibiotic adjuvant, especially useful in repurposing β-lactam antibiotics against multidrug-resistant MRSA.

Combinations of β-lactam or aminoglycoside antibiotics with plectasin are synergistic against methicillin-sensitive and methicillin-resistant Staphylococcus aureus

Bacterial infections remain the leading killer worldwide which is worsened by the continuous emergence of antibiotic resistance. In particular, methicillin-sensitive (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) are prevalent and the latter can be difficult to treat. The traditional strategy of novel therapeutic drug development inevitably leads to emergence of resistant strains, rendering the new drugs ineffective. Therefore, rejuvenating the therapeutic potentials of existing antibiotics offers an attractive novel strategy. Plectasin, a defensin antimicrobial peptide, potentiates the activities of other antibiotics such as β-lactams, aminoglycosides and glycopeptides against MSSA and MRSA. We performed in vitro and in vivo investigations to test against genetically diverse clinical isolates of MSSA (n = 101) and MRSA (n = 115). Minimum inhibitory concentrations (MIC) were determined by the broth microdilution method. The effects of combining plectasin with β-lactams, aminoglycosides and glycopeptides were examined using the chequerboard method and time kill curves. A murine neutropenic thigh model and a murine peritoneal infection model were used to test the effect of combination in vivo. Determined by factional inhibitory concentration index (FICI), plectasin in combination with aminoglycosides (gentamicin, neomycin or amikacin) displayed synergistic effects in 76-78% of MSSA and MRSA. A similar synergistic response was observed when plectasin was combined with β-lactams (penicillin, amoxicillin or flucloxacillin) in 87-89% of MSSA and MRSA. Interestingly, no such interaction was observed when plectasin was paired with vancomycin. Time kill analysis also demonstrated significant synergistic activities when plectasin was combined with amoxicillin, gentamicin or neomycin. In the murine models, plectasin at doses as low as 8 mg/kg augmented the activities of amoxicillin and gentamicin in successful treatment of MSSA and MRSA infections. We demonstrated that plectasin strongly rejuvenates the therapeutic potencies of existing antibiotics in vitro and in vivo. This is a novel strategy that can have major clinical implications in our fight against bacterial infections.

Efficacy of novel antibacterial compounds targeting histidine kinase YycG protein

Treating staphylococcal biofilm-associated infections is challenging. Based on the findings that compound 2 targeting the HK domain of Staphylococcus epidermidis YycG has bactericidal and antibiofilm activities against staphylococci, six newly synthesized derivatives were evaluated for their antibacterial activities. The six derivatives of compound 2 inhibited autophosphorylation of recombinant YycG′ and the IC₅₀ values ranged from 24.2 to 71.2 μM. The derivatives displayed bactericidal activity against planktonic S. epidermidis or Staphylococcus aureus strains in the MIC range of 1.5–3.1 μM. All the derivatives had antibiofilm activities against the 6- and 24-h biofilms of S. epidermidis. Compared to the prototype compound 2, they had less cytotoxicity for Vero cells and less hemolytic activity for human erythrocytes. The derivatives showed antibacterial activities against clinical methicillin-resistant staphylococcal isolates. The structural modification of YycG inhibitors will assist the discovery of novel agents to eliminate biofilm infections and multidrug-resistant staphylococcal infections.

An in vitro study on the effects of nisin on the antibacterial activities of 18 antibiotics against Enterococcus faecalis

Enterococcus faecalis rank among the leading causes of nosocomial infections worldwide and possesses both intrinsic and acquired resistance to a variety of antibiotics. Development of new antibiotics is limited, and pathogens continually generate new antibiotic resistance. Many researchers aim to identify strategies to effectively kill this drug-resistant pathogen. Here, we evaluated the effect of the antimicrobial peptide nisin on the antibacterial activities of 18 antibiotics against E. faecalis. The MIC and MBC results showed that the antibacterial activities of 18 antibiotics against E. faecalis OG1RF, ATCC 29212, and strain E were significantly improved in the presence of 200 U/ml nisin. Statistically significant differences were observed between the results with and without 200 U/ml nisin at the same concentrations of penicillin or chloramphenicol (p<0.05). The checkerboard assay showed that the combination of nisin and penicillin or chloramphenicol had a synergetic effect against the three tested E. faecalis strains. The transmission electron microscope images showed that E. faecalis was not obviously destroyed by penicillin or chloramphenicol alone but was severely disrupted by either antibiotic in combination with nisin. Furthermore, assessing biofilms by a confocal laser scanning microscope showed that penicillin, ciprofloxacin, and chloramphenicol all showed stronger antibiofilm actions in combination with nisin than when these antibiotics were administered alone. Therefore, nisin can significantly improve the antibacterial and antibiofilm activities of many antibiotics, and certain antibiotics in combination with nisin have considerable potential for use as inhibitors of this drug-resistant pathogen.

Sensitization of Staphylococcus aureus to methicillin and other antibiotics in vitro and in vivo in the presence of HAMLET

HAMLET (human alpha-lactalbumin made lethal to tumor cells) is a protein-lipid complex from human milk with both tumoricidal and bactericidal activities. HAMLET exerts a rather specific bactericidal activity against some respiratory pathogens, with highest activity against Streptococcus pneumoniae, but lacks activity against most other bacterial pathogens, including Staphylococci. Still, ion transport associated with death in S. pneumoniae is also detected to a lower degree in insensitive organisms. In this study we demonstrate that HAMLET acts as an antimicrobial adjuvant that can increase the activity of a broad spectrum of antibiotics (methicillin, vancomycin, gentamicin and erythromycin) against multi-drug resistant Staphylococcus aureus, to a degree where they become sensitive to those same antibiotics, both in antimicrobial assays against planktonic and biofilm bacteria and in an in vivo model of nasopharyngeal colonization. We show that HAMLET exerts these effects specifically by dissipating the proton gradient and inducing a sodium-dependent calcium influx that partially depolarizes the plasma membrane, the same mechanism induced during pneumococcal death. These effects results in an increased cell associated binding and/or uptake of penicillin, gentamicin and vancomycin, especially in resistant stains. Finally, HAMLET inhibits the increased resistance of methicillin seen under antibiotic pressure and the bacteria do not become resistant to the adjuvant, which is a major advantageous feature of the molecule. These results highlight HAMLET as a novel antimicrobial adjuvant with the potential to increase the clinical usefulness of antibiotics against drug resistant strains of S. aureus.

The human milk protein-lipid complex HAMLET sensitizes bacterial pathogens to traditional antimicrobial agents

The fight against antibiotic resistance is one of the most significant challenges to public health of our time. The inevitable development of resistance following the introduction of novel antibiotics has led to an urgent need for the development of new antibacterial drugs with new mechanisms of action that are not susceptible to existing resistance mechanisms. One such compound is HAMLET, a natural complex from human milk that kills Streptococcus pneumoniae (the pneumococcus) using a mechanism different from common antibiotics and is immune to resistance-development. In this study we show that sublethal concentrations of HAMLET potentiate the effect of common antibiotics (penicillins, macrolides, and aminoglycosides) against pneumococci. Using MIC assays and short-time killing assays we dramatically reduced the concentrations of antibiotics needed to kill pneumococci, especially for antibiotic-resistant strains that in the presence of HAMLET fell into the clinically sensitive range. Using a biofilm model in vitro and nasopharyngeal colonization in vivo, a combination of HAMLET and antibiotics completely eradicated both biofilms and colonization in mice of both antibiotic-sensitive and resistant strains, something each agent alone was unable to do. HAMLET-potentiation of antibiotics was partially due to increased accessibility of antibiotics to the bacteria, but relied more on calcium import and kinase activation, the same activation pathway HAMLET uses when killing pneumococci by itself. Finally, the sensitizing effect was not confined to species sensitive to HAMLET. The HAMLET-resistant respiratory species Acinetobacter baumanii and Moraxella catarrhalis were all sensitized to various classes of antibiotics in the presence of HAMLET, activating the same mechanism as in pneumococci. Combined these results suggest the presence of a conserved HAMLET-activated pathway that circumvents antibiotic resistance in bacteria. The ability to activate this pathway may extend the lifetime of the current treatment arsenal.

An in vitro synergetic evaluation of the use of nisin and sodium fluoride or chlorhexidine against Streptococcus mutans

The objective of this study is to investigate the synergetic action between nisin and sodium fluoride or chlorhexidine against Streptococcus mutans, a primary cariogenic pathogen. In the antibacterial assay, a synergetic effect on S. mutans was found between nisin and sodium fluoride, but there was no interaction between nisin and chlorhexidine by the checkerboard, the fractional inhibitory concentration (FIC) and the fractional bactericidal concentration (FBC) tests. S. mutans survival rates showed a significant decline after treatment with a combination of nisin and sodium fluoride in a time-kill study. Scanning electron microscopy showed that the damage to S. mutans with the combined nisin and sodium fluoride treatment was the most severe among all of the different single and combined antimicrobial treatments. Furthermore, in the antibiofilm test, nisin in combination with sodium fluoride produced a stronger bactericidal effect on a S. mutans biofilm for 4 h and 16 h compared with sodium fluoride alone by confocal laser scanning microscopy. Nisin in combination with sodium fluoride exerted a high bactericidal effect on S. mutans and thereby has the potential to be used as an effective drug combination to prevent dental caries.

Treatment of Drug-resistant Pneumococcal Meningitis

The approach to therapy in patients with pneumococcal meningitis has changed considerably over the past 20 years. Given the emergence of pneumococcal strains that are intermediately susceptible or highly resistant to penicillin, penicillin is not recommended as empiric therapy for presumed pneumococcal meningitis; the combination of vancomycin and a third-generation cephalosporin (either cefotaxime or ceftriaxone) should be used, pending isolation of the organism and in vitro susceptibility testing. For patients with pneumococcal meningitis caused by highly penicillin- or cephalosporin-resistant strains, the addition of rifampin can be considered if the organism is susceptible in vitro, the expected clinical or bacteriologic response is delayed, or the pneumococcal isolate has a cefotaxime or ceftriaxone minimal inhibitory concentration greater than 4 μg/mL. Meropenem is not a good option for monotherapy of highly penicillin- or cephalosporin-resistant strains, but use of a fluoroquinolone with in vitro activity against Streptococcus pneumoniae (specifically moxifloxacin) is an option in patients failing standard therapy; if used, however, it should be combined with a third-generation cephalosporin or vancomycin. Newer glycopeptides, daptomycin, and linezolid require further study to determine their efficacy in patients with pneumococcal meningitis.

Strategies and new developments in the management of bacterial meningitis

The principles of antimicrobial therapy for acute bacterial meningitis include use of agents that penetrate well into cerebrospinal fluid and attain appropriate cerebrospinal fluid concentrations, are active in purulent cerebrospinal fluid, and are bactericidal against the infecting pathogen. Recommendations for treatment of bacterial meningitis have undergone significant evolution in recent years, given the emergence of pneumococcal strains that are resistant to penicillin. Clinical experience with use of newer agents is limited to case reports, but these agents may be necessary to consider in patients who are failing standard therapy.

Synergy with rifampin and kanamycin enhances potency, kill kinetics, and selectivity of de novo-designed antimicrobial peptides

By choosing membranes as targets of action, antibacterial peptides offer the promise of providing antibiotics to which bacteria would not become resistant. However, there is a need to increase their potency against bacteria along with achieving a reduction in toxicity to host cells. Here, we report that three de novo-designed antibacterial peptides (DeltaFm, DeltaFmscr, and Ud) with poor to moderate antibacterial potencies and kill kinetics improved significantly in all of these aspects when synergized with rifampin and kanamycin against Escherichia coli. (DeltaFm and DeltaFmscr [a scrambled-sequence version of DeltaFm] are isomeric, monomeric decapeptides containing the nonproteinogenic amino acid alpha,beta-didehydrophenylalanine [DeltaF] in their sequences. Ud is a lysine-branched dimeric peptide containing the helicogenic amino acid alpha-aminoisobutyric acid [Aib].) In synergy with rifampin, the MIC of DeltaFmscr showed a 34-fold decrease (67.9 microg/ml alone, compared to 2 microg/ml in combination). A 20-fold improvement in the minimum bactericidal concentration of Ud was observed when the peptide was used in combination with rifampin (369.9 microg/ml alone, compared to 18.5 microg/ml in combination). Synergy with kanamycin resulted in an enhancement in kill kinetics for DeltaFmscr (no killing until 60 min for DeltaFmscr alone, versus 50% and 90% killing within 20 min and 60 min, respectively, in combination with kanamycin). Combination of the dendrimeric peptide DeltaFq (a K-K2 dendrimer for which the sequence of DeltaFm constitutes each of the four branches) (MIC, 21.3 microg/ml) with kanamycin (MIC, 2.1 microg/ml) not only lowered the MIC of each by 4-fold but also improved the therapeutic potential of this highly hemolytic (37% hemolysis alone, compared to 4% hemolysis in combination) and cytotoxic (70% toxicity at 10x MIC alone, versus 30% toxicity in combination) peptide. Thus, synergy between peptide and nonpeptide antibiotics has the potential to enhance the potency and target selectivity of antibacterial peptides, providing regimens which are more potent, faster acting, and safer for clinical use.

Synthesis and combinational antibacterial study of 5''-modified neomycin

A library of 5″-modified neomycin derivatives were synthesized for an antibacterial structure-activity optimization strategy. Two leads exhibited prominent activity against both methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). Antibacterial activities were measured when combined with other clinically used antibiotics. Significant synergistic activities were observed which may lead to the development of novel therapeutic practices in the battle against infectious bacteria.

[Presumptive bacterial meningitis in adults: initial antimicrobial therapy]

CSF sterilization should be obtained very rapidly to reduce both mortality and morbidity due to bacterial meningitis. Thus, antibiotic treatment should be adapted to the suspected bacterium and administered as early as possible at high dosage with - if necessary - a loading dose and continuous perfusion. The rates of abnormal susceptibility to penicillin of Streptococcus pneumoniae, Neisseria meningitis and Haemophilus influenzae are 37%, 30% and 12% respectively. Thus, ceftriaxone or cefotaxim must be used as empirical treatment. Listeria monocytogenes remains fully susceptible to aminopenicillin, so, the combination aminopenicillin and aminoglycoside is the first-line treatment. Antibiotic resistance, allergy or contra-indications, are in fact rare but in these cases, antibiotic combinations are often needed. The latter are more or less complex and clinically validated; they include molecules such as vancomycine, fosfomycin, fluoroquinolone or linezolid.

[Antibiotic management of presumptive bacterial meningitis in adults (rational, methods, course, and follow-up)]

The annual incidence of community acquired meningitis ranges between 0.6 and four per 100,000 adults in industrialized countries. The most common causative bacteria are Streptococcus pneumoniae, Neisseria meningitidis, Listeria monocytogenes. The emergence of resistance to antibiotics, especially for S. pneumoniae, could explain the clinical failure of third generation cephalosporins used to treat adults with S. pneumoniae meningitis. The present therapeutic suggestions are more based on the extrapolation of an experimental model than on relevant clinical trials.

Mechanisms of drug combinations: interaction and network perspectives

Understanding the molecular mechanisms underlying synergistic, potentiative and antagonistic effects of drug combinations could facilitate the discovery of novel efficacious combinations and multi-targeted agents. In this article, we describe an extensive investigation of the published literature on drug combinations for which the combination effect has been evaluated by rigorous analysis methods and for which relevant molecular interaction profiles of the drugs involved are available. Analysis of the 117 drug combinations identified reveals general and specific modes of action, and highlights the potential value of molecular interaction profiles in the discovery of novel multicomponent therapies.

Antimicrobial activity of a chimeric enzybiotic towards Staphylococcus aureus

Phage lytic enzymes (enzybiotics) have gained attention as prospective tools to eradicate Gram-positive pathogens resistant to antibiotics. Attempts to purify the P16 endolysin of Staphylococcus aureus phage P68 were unsuccessful owing to the poor solubility of the protein. To overcome this limitation, we constructed a chimeric endolysin (P16-17) comprised of the inferred N-terminal d-alanyl-glycyl endopeptidase domain and the C-terminal cell wall targeting domain of the S. aureus phage P16 endolysin and the P17 minor coat protein, respectively. The domain swapping approach and the applied purification procedure resulted in soluble P16-17 protein, which exhibited antimicrobial activity towards S. aureus. In addition, P16-17 augmented the antimicrobial efficacy of the antibiotic gentamicin. This synergistic effect could be useful to reduce the effective dose of aminoglycoside antibiotics.

BMAP-28 improves the efficacy of vancomycin in rat models of gram-positive cocci ureteral stent infection

An experimental study was performed to evaluate the efficacy of BMAP-28 alone and in combination with vancomycin in animal models ureteral stent infection due to Enterococcus faecalis and Staphylococcus aureus. Study included a control group without bacterial challenge to evaluate the sterility of surgical procedure, a challenged control group that did not receive any antibiotic prophylaxis and for each bacterial strain three challenged groups that received (a) 10 mg/kg vancomycin intraperitoneally, immediately after stent implantation, (b) BMAP-28-coated ureteral stents where 0.2-cm(2) sterile ureteral stents were incubated in 1mg/l BMAP-28 solution for 30 min immediately before implantation and (c) intraperitoneal vancomycin plus BMAP-28-coated ureteral stent at the above concentrations. Experiments were performed in duplicate. Ureteral stents were explanted at day 5 following implantation and biofilm bacteria enumerated. Our data showed that rats that received intraperitoneal vancomycin showed the lowest bacterial numbers. BMAP-28 combined with vancomycin showed efficacies higher than that of each single compound. These results highlight the potential usefulness of this combination in preventing ureteral stent-associated in gram-positive infections.

Preincubation of pneumococci with beta-lactams alone or combined with levofloxacin prevents quinolone-induced resistance without increasing intracellular levels of levofloxacin

Preincubation of pneumococci with sub-MIC concentrations of ceftriaxone (1/16x MIC), cefotaxime (1/8x MIC), and meropenem (1/4x MIC) alone or combined with levofloxacin (1/8x MIC) over 6 h prevents the emergence of levofloxacin-resistant mutants after 96 h of incubation but does not affect the intracellular accumulation of levofloxacin in two penicillin-resistant pneumococcal strains, suggesting a link between the mechanism of action of beta-lactams and the emergence of quinolone-induced resistance in pneumococci.

Synergistic killing of Streptococcus pneumoniae with the bacteriophage lytic enzyme Cpl-1 and penicillin or gentamicin depends on the level of penicillin resistance

A combination of Cpl-1, a bacteriophage lytic enzyme, and penicillin, gentamicin, levofloxacin, or azithromycin was tested against Streptococcus pneumoniae strains with various susceptibilities to penicillin. Activities of Cpl-1 and gentamicin were increasingly synergistic with a decreasing penicillin MIC, while Cpl-1 and penicillin showed synergy against an extremely penicillin-resistant strain.

New therapies for pneumococcal meningitis

The treatment of pneumococcal meningitis remains a major challenge, as reflected by the continued high morbidity and case fatality of the disease. The worldwide increase of penicillin-resistant pneumococci and more recently cephalosporin- and vancomycin-tolerant pneumococci has jeopardised the efficacy of standard treatments based on extended spectrum cephalosporins alone or in combination with vancomycin. This review provides a summary of newly developed antibiotics tested in the rabbit meningitis model. In particular, newer beta-lactam monotherapies (cefepime, meropenem, ertapenem), recently developed quinolones (garenoxacin, gemifloxacin, gatifloxacin, moxifloxacin) and a lipopeptide antibiotic (daptomycin) are discussed. A special emphasis is placed on the potential role of combination treatments with some of the new compounds, which are of interest based on the background of increasing resistance problems due to their often synergistic activity in the rabbit model of pneumococcal meningitis.