Combating resistance in a challenging, changing environment

The antibacterial activity of syringopicroside, its metabolites and natural analogues from Syringae Folium

In the present study, the in vitro antibacterial activity of an effective fraction (ESF) from Syringae Folium (SF) on Methicillin-resistant Staphylococcus aureus (MRSA) was evaluated and then its in vivo activity was evaluated by using the MRSA-infected mouse peritonitis model. The ESF showed a significant in vitro and in vivo activity on decreasing the Minimum Inhibitory Concentrations (MICs) and increasing the survival rate of mouse from 42.8% to 100%. Six iridoid glucosides (IGs) of ESF were characterized by UPLC-TOF-MS method and also isolated by column chromatography. Most of them showed in vitro anti MRSA activity. Syringopicroside (Sy), the major compound of IGs, was found to increase the survival rate from 42.8% to 92.8% of the MRSA-infected mouse, which revealed Sy is also the main active components of ESF. In order to know why the effect of oral administration of SF is better than its injections in clinic and the metabolites of Sy, seven metabolites of Sy were isolated from rat urine and identified on the basis of NMR and MS spectra. Most of metabolites possessed stronger in vitro anti-MRSA activity than that of Sy, which furtherly proved the clinical result.

Novel Cationic Gemini Surfactants and Methods for Determination of Their Antimicrobial Activity – Review

Newly series of Gemini surfactants have emerged which are composed of two hydrophobic tails and two cationic head groups linked by spacer group. Today, these cationic Gemini surfactants are attracting attention of the researchers as these surfactants are more efficient in lowering surface tension as the conventional ones. Cationic Gemini surfactants have lower critical micelle concentrations (CMC) and higher surface tension reduction as compared to those of corresponding monoalkyl ammonium salts. They have wide industrial and household applications. They can be used as emulsifiers, dispersing and anti-foaming agents etc. Cationic Gemini surfactants show good antimicrobial activity against gram-positive and gram-negative bacteria. Antimicrobial activity has also been studied against fungi and yeast species. These cationic Gemini surfactants can be used as antibacterial, antifungal, antiviral agents. This review paper deals with synthesis, antimicrobial activity, methods for determining antimicrobial activity (MIC means minimum inhibitory concentration) and applications of cationic Gemini surfactants.

Studies of the in vitro antibacterial activities of several polyphenols against clinical isolates of methicillin-resistant Staphylococcus aureus

In this study, we report the antibacterial activities of six polyphenols (i.e., luteolin, quercetin, scutellarin, apigenin, chlorogenic acid, and resveratrol) against 29 clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA), and in vitro antibacterial activities of two-drug combinations. All of the MRSA strains evaluated were clinical isolates from patients with MRSA bacteremia. The antibacterial activities were determined by agar dilution method, and the two-drug antibacterial activities were determined by the checkerboard agar dilution method. It was found that luteolin, quercetin and resveratrol show obvious antibacterial activities against MRSA, and the results of two-drug antibacterial activity show either synergy or additivity, without evidences of antagonistic effects.

Update on carbohydrate-containing antibacterial agents

BACKGROUND

Since the first known use of antibiotics > 2,500 years ago, a research field with immense importance for the welfare of mankind has been developed. After a decrease in interest in this topic by the end of the 20th century the occurrence of (poly-)resistant strains of bacteria induced a revival of antibiotics research. Health systems have been seeking viable and reliable solutions to this dangerous and expansive threat.

OBJECTIVE

This review will focus on carbohydrate-containing antibiotics and will give an outline of recently published novel isolated, semisynthetic as well as synthetic structures, their mechanism of action, if known, and the strategies for the design of compounds with potential by improved antibacterial properties.

METHODS

The literature between 2000 and 2008 was screened with main focus on recent examples of novel structures and strategies for the lead finding of exclusively antibacterial agents.

RESULTS/CONCLUSION

With the explanation of the role of the carbohydrate moieties in the respective antibacterial agents together with better synthetic strategies in carbohydrate chemistry as well as improvements in assay development for high throughput screening methods, carbohydrate-containing antibiotics can be used for the finding of potential drug leads that contribute to the fight against infections and diseases caused by (resistant) bacterial pathogens.

Synergistic effects between aminoethyl-chitosans and beta-lactams against methicillin-resistant Staphylococcus aureus (MRSA)

Two kinds of aminoethyl-chitosans (AEC), AEC90 and AEC50, which had degrees of deacetylation of 90% and 50%, respectively, were prepared and their synergistic effects in combination with beta-lactams including ampicillin, penicillin, and oxacillin against two standard methicillin-resistant Staphylococcus aureus (MRSA) strains and twelve clinical isolated MRSA strains were investigated. When AECs and beta-lactams were combined, synergistic effects were observed with fractional inhibitory concentration (FIC) indices of 0.252-0.508, and the MICs of beta-lactams in the presence of AECs were dramatically reduced.

Stress-responsive systems set specific limits to the overproduction of membrane proteins in Bacillus subtilis

Essential membrane proteins are generally recognized as relevant potential drug targets due to their exposed localization in the cell envelope. Unfortunately, high-level production of membrane proteins for functional and structural analyses is often problematic. This is mainly due to their high overall hydrophobicity. To develop new concepts for membrane protein overproduction, we investigated whether the biogenesis of overproduced membrane proteins is affected by stress response-related proteolytic systems in the membrane. For this purpose, the well-established expression host Bacillus subtilis was used to overproduce eight essential membrane proteins from B. subtilis and Staphylococcus aureus. The results show that the sigma(W) regulon (responding to cell envelope perturbations) and the CssRS two-component regulatory system (responding to unfolded exported proteins) set critical limits to membrane protein production in large quantities. The identified sigW or cssRS mutant B. subtilis strains with significantly improved capacity for membrane protein production are interesting candidate expression hosts for fundamental research and biotechnological applications. Importantly, our results pinpoint the interdependent expression and function of membrane-associated proteases as key parameters in bacterial membrane protein production.

Screening of Chinese medicinal plants for inhibition against clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA)

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional herbs are a valuable source of novel antibacterials in combating pathogenic isolates of methicillin-resistant Staphylococcus aureus (MRSA), a global nosocomial problem.

AIM OF THE STUDY

To assess in vitro anti-MRSA activity of extracts from Chinese herbs. The minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) were determined in the setting of clinical MRSA isolates.

MATERIALS AND METHODS

A collection of 19 plant extracts were obtained and bioassay-guided phytochemical analysis performed. Antibacterial susceptibilities were screened for inhibitory zone and MICs/MBCs determined by serial dilution with a standardized microdilution broth methodology. 9 MRSA isolates and a standard control strain (ATCC 25923) were cultured and exposed to the plant extract and isolated compound. Vancomycin was used as a positive control agent.

RESULTS

All the presented 19 plants showed anti-MRSA activity with MIC of 1.25-3.07mg/ml. The most active antimicrobial plants were Dendrobenthamia capitata, Elsholtzia rugulosa, Elsholtzia blanda, Geranium strictipes and Polygonum multiflorum (MIC< or =1.43mg/ml), and betulinic acid isolated from the active ethyl acetate fraction of Dendrobenthamia capitata extract was determined with MIC/MBC values as 62.5/125.0mg/ml.

CONCLUSIONS

Dendrobenthamia capitata, Elsholtzia rugulosa, Elsholtzia blanda, Geranium strictipesPolygonum multiflorum and betulinic acid demonstrate promising anti-MRSA potential.

Antibiotic use in 26 departments of internal medicine in 6 general hospitals in Israel: variability and contributing factors

OBJECTIVES

Increased antibiotic consumption is associated with increased bacterial resistance worldwide. We aimed to analyse antibiotic consumption and potential contributory factors in internal medicine departments in Israel.

METHODS

Data (2003-04) from 26 departments in 6 hospitals were retrieved. Defined daily doses (DDD)/100 bed-days were calculated for total antibiotic use and by antibiotic class. Patterns identified were correlated with 15 patients' and departmental variables by univariate and multivariate analyses.

RESULTS

Total antibiotic consumption differed by a factor of 2.3 (115 DDD/100 bed-days to 49.1 DDD/100 bed-days) between the highest and lowest consuming departments. Antibiotic classes differed by a factor of 22.8 for macrolides, a factor of 20 for piperacillin/tazobactam, a factor of 17 for carbapenems, a factor of 13.3 for quinolones, a factor of 9 for vancomycin, a factor of 6.8 for amoxicillin/clavulanate, a factor of 6.6 for aminoglycosides, a factor of 5.3 for penicillins and a factor of 2.8 for cephalosporins. Even among departments within hospitals, there was a difference of up to 1.5-fold for total use and antibiotic class differences ranged between 2.5- and 7.2-fold for third- and fourth-generation cephalosporins, despite similar Charlson scores and other patient variables. In the multivariate analysis, hospital affiliation and rate of 1 day hospitalization were the only significant variables predicting total antibiotic use, contributing 43% and 7.3%, respectively, to the variance. By antibiotic class, controlling for hospital affiliation, patients with neutropenia, lower respiratory tract infections and assisted ventilation were the most common significant contributors, ranging from 3.5% for quinolones to 7.7% for piperacillin/tazobactam.

CONCLUSIONS

Patterns of antibiotic use vary widely among internal medicine departments in Israel, which cannot be explained by objective parameters related either to patients or wards. Ongoing monitoring and guideline formulation are needed to regulate antibiotic prescription.

Antibiotic combination as empirical therapy for extended spectrum Beta-lactamase

BACKGROUND

extended spectrum β-lactamase (ESBL) producing gram negative bacilli are becoming a growing problem worldwide with difficulties in designing a national formulary for empirical treatment of gram negative sepsis.

OBJECTIVES

In this study, we investigated the in vitro activity of Carbapenems, Pipracillin-Tazobactam, Ciprofloxacin alone or in combination with aminoglycosides against ESBL-producing strains isolated from clinical samples.

METHODS

Three hundred and one ESBL-producing Escherichia coli and K. pneumoniae strains isolated from clinical samples were investigated. Isolates were screened initially for ESBL production using an automated system. All ESBL isolates were further confirmed using the double-disk diffusion method.

RESULTS

The overall Piperacillin-Tazobactam susceptibility was 57.9 (64.4% E. coli and 43.6% Klebsiella pneumoniae). Only 29.6% of ESBLs (24.9% E. coli and 39.6% Klebsiella pneumoniae) were ciprofloxacin susceptible. 98.1% E. coli and 93.1% of Klebsiella pneumoniae were susceptible to Piperacillin-Tazobactam plus Amikacin combination. 73.7% E. coli and 61.4% of Klebsiella pneumoniae were susceptible to Piperacillin-Tazobactam plus Gentamicin combination. 96.7% E. coli and 91.1% of Klebsiella pneumoniae were susceptible to Ciprofloxacin plus Amikacin combination. 41.2% E. coli and 51.5% of Klebsiella pneumoniae were susceptible to Ciprofloxacin plus Gentamicin combination.

CONCLUSION

ESBLs have high resistance profile against Piperacillin/Tazobactam and Ciprofloxacin. The ESBLs from Oman have similar resistantce pattern as those reported from UK and USA. This resistance decreases when these drugs are combined with Amikacin. All ESBLs are susceptible to Carbapenems. However, carbepenam overuse can lead to emergence of carbapenems resistant gram negative bacilli and ESBLs. Combination of Amikacin plus Piperacillin/Tazobactam is a feasible empirical therapy for ESBLs.

Redesigning β-lactams to combat resistance: summary and conclusions

The relentless emergence and spread of antimicrobial resistance warrant an increased awareness of the problem and improved coordination and standardisation of surveillance systems, as well as resistance control strategies. Moreover, this underscores the urgent need for new antibiotics active against the emerging resistant pathogens. Ceftobiprole is a new beta-lactam molecule engineered for bactericidal activity against methicillin-resistant staphylococci that also exhibits an extended broad spectrum of activity covering the most clinically important Gram-positive (methicillin-susceptible staphylococci, penicillin-susceptible and -resistant pneumococci, other streptococci and ampicillin-susceptible enterococci) and Gram-negative (Enterobacteriaceae, Pseudomonas aeruginosa, Acinetobacter spp., Haemophilus spp. and Moraxella spp.) pathogens. Results from studies with experimental infections and from clinical trials support a role for ceftobiprole in treating complicated skin and skin structure infections caused by Gram-positive pathogens, including methicillin-resistant staphylococci, and suggest a potential role for this drug in treating other types of serious infection caused by Gram-positive and Gram-negative pathogens.