Evolving problems with resistant pathogens

Efficacy of antimicrobial peptide P113 oral health care products on the reduction of oral bacteria number and dental plaque formation in a randomized clinical assessment

Background/purpose

Dental plaque is the main cause leading to the dental caries and periodontal diseases. The main purpose of this study was to test the efficacy of oral spray containing the antimicrobial peptide P-113 on the reduction of oral bacteria number and dental plaque formation in a randomized clinical assessment.

Materials and methods

This study was divided into two parts. In Part A, we investigated the user experiences with the P-113 containing oral spray. In part B, 14 subjects in the experimental group used the P-113-containing oral spray, while 14 subjects in the control group used a placebo without the P-113 in a 4-week clinical trial. Participants were asked to use the P-113-containing oral spray or placebo 3 times per day and 5 times per use. Moreover, 3 check-ups and 2 washouts were carried out to evaluate the DMFT score, dental plaque weight, dental plaque index, and gingival index.

Results

In part A, up to 91.8% of the subjects in the experimental group were satisfied with the use of the P-113-containing oral spray. In part B, based on our PacBio SMRT sequencing platform and DADA2 analysis, the numbers of Streptococcus and Porphyromonas in the experimental group were lower than those in the control group. In addition, decreased dental plaque weight, dental plaque index, and gingival index were all observed in the experimental group.

Conclusion

The P-113-containing oral spray has the potential to reduce the dental caries and periodontal disease-related bacteria and to control the dental plaque formation.

Restoring susceptibility to β-lactam antibiotics in methicillin-resistant Staphylococcus aureus

Infections by Staphylococcus aureus have been treated historically with β-lactam antibiotics. However, these antibiotics have become obsolete in methicillin-resistant S. aureus by acquisition of the bla and mec operons. The presence of the β-lactam antibiotic is detected by the sensor domains of BlaR and/or MecR, and the information is transmitted to the cytoplasm, resulting in derepression of the antibiotic-resistance genes. We hypothesized that inhibition of the sensor domain would shut down this response system, and β-lactam susceptibility would be restored. An in silico search of 11 million compounds led to a benzimidazole-based hit and, ultimately, to the boronate 4. The X-ray structure of 4 is covalently engaged with the active-site serine of BlaR. Compound 4 potentiates by 16- to 4,096-fold the activities of oxacillin and of meropenem against methicillin-resistant S. aureus strains. The combination of 4 with oxacillin or meropenem shows efficacy in infected mice, validating the strategy.

Characteristics and therapeutic applications of antimicrobial peptides

The demand for novel antimicrobial compounds is rapidly growing due to the phenomenon of antibiotic resistance in bacteria. In response, numerous alternative approaches are being taken including use of polymers, metals, combinatorial approaches, and antimicrobial peptides (AMPs). AMPs are a naturally occurring part of the immune system of all higher organisms and display remarkable broad-spectrum activity and high selectivity for bacterial cells over host cells. However, despite good activity and safety profiles, AMPs have struggled to find success in the clinic. In this review, we outline the fundamental properties of AMPs that make them effective antimicrobials and extend this into three main approaches being used to help AMPs become viable clinical options. These three approaches are the incorporation of non-natural amino acids into the AMP sequence to impart better pharmacological properties, the incorporation of AMPs in hydrogels, and the chemical modification of surfaces with AMPs for device applications. These approaches are being developed to enhance the biocompatibility, stability, and/or bioavailability of AMPs as clinical options.

Green synthesis, characterization, antimicrobial and cytotoxic effect of silver nanoparticles using arabinoxylan isolated from Kalmegh

A green synthesis of silver nanoparticles was synthesized by AgNO₃ with arabinoxylan, isolated from green stem of Andrographis paniculata (Kalmegh). The synthesized Ag NPs-arabinoxylan conjugates were characterized by UV-vis spectroscopy, FE-SEM, TEM, XRD, TGA, EDX, and Zeta potential experiments. The Ag NPs formation was established by the surface plasmon resonance band ~410.25 nm. SEM image showed mostly spherical morphology of Ag NPs. The fcc crystalline nature was identified by XRD, SAED and the size were 24.5 and 25 nm from TEM and XRD analysis respectively. The prepared Ag NPs showed dose-dependent antimicrobial activity against Streptococcus pneumonia, Candida albicans and E. coli. The nanoparciles damage 4% hemolysis to human RBCs at 12.5 μg/mL. MTT assay of Ag NPs showed that half of the cell killed at 10 μg/mL and wound healing assay observed effective inhibition cell proliferation.

Nine-Residue Peptide Self-Assembles in the Presence of Silver to Produce a Self-Healing, Cytocompatible, Antimicrobial Hydrogel

Silver compounds have been used extensively for wound healing because of their antimicrobial properties, but high concentrations of silver are toxic to mammalian cells. We designed a peptide that binds silver and releases only small amounts of this ion over time, therefore overcoming the problem of silver toxicity. Silver binding was achieved through incorporation of an unnatural amino acid, 3'-pyridyl alanine (3'-PyA), into the peptide sequence. Upon the addition of silver ions, the peptide adopts a beta-sheet secondary structure and self-assembles into a strong hydrogel as characterized by rheology, circular dichroism, and transmission electron microscopy. We show that the resulting hydrogel kills Escherichia coli and Staphylococcus aureus but is not toxic to fibroblasts and could be used for wound healing. The amount of Ag(I) released by hydrogels into the solution is less than 4% and this low amount of Ag(I) does not change in the pH range 6-8. These studies provide an initial indication for use of the designed hydrogel as injectable, antimicrobial wound dressing.

Phylogenetic Analysis and Antibiotics Resistance of Listeria Monocytogenes Contaminating Chicken Meat in Surabaya, Indonesia

The objective of this study was to identify the phylogenetic analysis and antibiotic resistance of Listeria monocytogenes contaminating chicken meat in Surabaya. 60 chicken meat samples were collected from supermarkets, mobile vendors, and traditional markets in Surabaya. A selective medium is used for isolation and identification of Listeria monocytogenes by chopping 25 grams of the chicken meat and to put it into the sterilized Erlenmeyer flasks. Some methods were used for the identification procedures, such as biochemical and morphological tests, antibiotic resistance test, PCR, and sequencing; also a phylogenetic analysis was conducted by a neighbor-joining analysis using Genetix Mac ver 8.0 with hlyA genes of Listeria monocytogenes recorded in GenBank, such as Lineage I (KC808543), Lineage II (AY229462, AY229346, AY229499, and AY229404), Lineage III (KJ504139, HQ686043, KJ504116, and DQ988349), and Lineage IV (EU840690, EF030606). The result shows that the prevalence of L. monocytogenes in Surabaya contaminating the chicken meat samples from the supermarkets was 10% (2/20), from the mobile vendors was 0/20 (0%), and from the traditional markets was 5% (1/20). It was seen from the band at 456 bp fragment. Furthermore, three isolates found in Surabaya were included in the new lineages which were resistant to old-generation antibiotics such as sulfamethonazole-trimetophrim (SXT) and amoxyllin sulbactam (MAS), but they were still sensitive to new-generation antibiotics such as cefotaxime (CTX) and meropenem (MEM).

Age-related variations in the in vitro bactericidal activity of human sera against Pseudomonas aeruginosa

The human serum is a vital component of the innate immunity of the host that acts as the first line of defence against invading pathogens. A key player in serum-mediated innate immune defence is a system of more than 35 proteins, collectively named as the complement system. After exposure of the pathogen, these proteins are activated in a cascade manner, ultimately forming a membrane attack complex (MAC) on the surface of the pathogen that directly lyses the bacterial cell. Formation of the MAC can be demonstrated in vitro by using serum bactericidal assay (SBA) that works in the absence of cellular components of blood after incubating the serum along with bacteria. Here, we describe the age-related differences in the bactericidal activity of human serum against Pseudomonas aeruginosa, an opportunistic human pathogen causing an array of hospital and community-acquired infections.

We demonstrate that adult sera were highly effective in the in vitro killing of Pseudomonas aeruginosa as compared to children and the elderly (p < 0.0001). Sera from children were seriously compromised in the killing P. aeruginosa, whereas elderly sera showed a reduced level of killing. Data revealed a positive correlation between age and serum-killing with higher coefficient of determination values of 0.34, 0.27, and 0.58 and p values of < 0.0001, < 0.001, and < 0.0001, respectively, after 60, 90, and 120 minutes of incubation. Hence, our study highlights the age-related difference in the bactericidal activity of human sera. We conclude that sera of children are totally compromised, whereas elderly sera are only partially compromised, in the killing of P. aeruginosa.

Antibiotic Residues in Chicken Meat: Global Prevalence, Threats, and Decontamination Strategies: A Review

Poultry production is among the most rapidly growing industries around the globe, and poultry is one of the major sources of meat. Poultry farmers use disease preventive and growth promoter antibiotics for faster growth of chickens in the shortest possible time to increase the rate of feed assimilation and to lower the incidence of mortality caused by a pathogen attack. Antibiotics may result in dysfunctionality of beneficial gut microbiota and increase resistance among microbial pathogens in poultry. Residues of these antibiotics in poultry meat have been determined in many of the studies globally and are considered one of the possible causes of antibacterial resistance in human pathogens. The presence of residues of antibiotics in poultry meat and meat products beyond maximum permissible limits is a matter of serious concern. Heat treatments can reduce the risk of some sulfonamides, tetracyclines, and fluoroquinolones but do not guarantee the complete elimination or degradation of these antibiotic residues present in broiler meat. Some of the developed countries, including Sweden, Norway, Denmark, and the European Union have already prohibited the application of antibiotics for preventive, as well as growth-promoting purposes. Training farmers to monitor withdrawal periods, banning the use of antibiotics as growth promoters, and adopting the veterinary feed directive of the U.S. Food and Drug Administration are important parameters to mitigate the emergence of antibiotic resistance in bacteria related to poultry production.

Antibiofilm peptides against oral biofilms

The oral cavity is a major entry point for bacteria and other microorganisms. Oral biofilms are formed by mixed communities of microorganisms embedded in an exopolysaccharide matrix. Biofilms forming on dental hard or soft tissue are the major cause of caries and endodontic and periodontal disease. Human oral biofilms exhibit high resistance to antimicrobial agents. Antibiofilm peptides constitute a diverse class of host-defense molecules that act to combat invasion and infection with biofilms. Different in vitro and in vivo biofilm models with quantitative analysis have been established to provide predictable platforms for the evaluation of the antibiofilm effect of oral antibiofilm peptides. These peptides have engendered considerable interest in the past decades as potential alternatives to traditional disinfecting agents due to their ability to target bacterial biofilms specifically, leading to the prevention of biofilm formation and destruction of pre-existing biofilms by Gram-positive and -negative bacterial pathogens and fungi. At the same time, challenges associated with the application of these antibiofilm peptides in dental practice also exist. The production of effective, nontoxic, and stable antibiofilm peptides is desired in both academic and industrial fields. This review focuses on the antibiofilm properties of current synthetic peptides and their application in different areas of dentistry.

Antibacterial properties and toxicity from metallic nanomaterials

The era of antibiotic resistance is a cause of increasing concern as bacteria continue to develop adaptive countermeasures against current antibiotics at an alarming rate. In recent years, studies have reported nanoparticles as a promising alternative to antibacterial reagents because of their exhibited antibacterial activity in several biomedical applications, including drug and gene delivery, tissue engineering, and imaging. Moreover, nanomaterial research has led to reports of a possible relationship between the morphological characteristics of a nanomaterial and the magnitude of its delivered toxicity. However, conventional synthesis of nanoparticles requires harsh chemicals and costly energy consumption. Additionally, the exact relationship between toxicity and morphology of nanomaterials has not been well established. Here, we review the recent advancements in synthesis techniques for silver, gold, copper, titanium, zinc oxide, and magnesium oxide nanomaterials and composites, with a focus on the toxicity exhibited by nanomaterials of multidimensions. This article highlights the benefits of selecting each material or metal-based composite for certain applications while also addressing possible setbacks and the toxic effects of the nanomaterials on the environment.

Green synthesis of silver nanoparticles using seed extract of Alpinia katsumadai, and their antioxidant, cytotoxicity, and antibacterial activities

A rapid green approach for synthesizing of silver nanoparticles using Alpinia katsumadai seed extract is described and their antioxidant, antibacterial and cytotoxicity activities evaluated.

Antibacterial activity and mechanism of Ag/ZnO nanocomposite against anaerobic oral pathogen Streptococcus mutans

Dental caries is a widespread disease mainly caused by the anaerobic oral pathogen Streptococcus mutans (S. mutans). Ag/ZnO nanocomposite is an efficient antibacterial agent because of its high antibacterial activity and low cytotoxicity. In this study, rod-like Ag/ZnO nanocomposite was synthesized through a deposition-precipitation method and characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The activity of Ag/ZnO nanocomposite against S. mutans was evaluated by determining the minimal inhibitory concentration, minimum bactericidal concentration and growth inhibition curve. The results showed that Ag/ZnO nanocomposite displayed higher activity against S. mutans compared with pure ZnO nanorods. Moreover, the antibacterial mechanism was investigated by determining the bacterial membrane potential, release of K⁺, intracellular reactive oxygen generation and lipid peroxidation. Disruption of membrane function and oxidation of biomacromolecules played important role in the antibacterial action of Ag/ZnO nanocomposite. This work proposes a potentially effective dental antibacterial agent against the dental caries-causing S. mutans.

Evaluation of therapeutic potentials of plant extracts against poultry bacteria threatening public health

BACKGROUND

Plant extracts were evaluated on poultry bacteria known to be threatening public health. This is to develop better bio-therapeutic agents from plant origin.

METHODS

Bacteria were isolated from water, feed, crop, gizzard and faeces of layer chicken. Isolates of interest (Escherichia coli, Salmonella enteritidis, Pseudomonas aeruginosa and Klebsiella oxytoca) were subjected to antibiotic susceptibility test. Resistant strains were further evaluated against different plant extracts in comparison to Meropenem (control) using agar diffusion method.

RESULTS

E. coli had the highest occurrence (53 %), followed by P. aeruginosa (25 %) and then S. enteritidis (13 %) while the least was K. oxytoca (9 %). Virtually all the isolates exhibited multi-antibiotic resistance (MAR) with gross resistance to Amoxicillin, Erythromycin and Cefuroxine. P. aeruginosa (75 %), S. enteritidis (75 %) and E. coli (63 %), had the highest MAR. Out of the 11 (100 %) plant extracts evaluated, 7 (64 %) were outstanding and showed varied levels of antibacterial activity. Specifically, methanol extract of Mangifera indica Julie cultivar leaf (MJLM) had the highest antibacterial activity, followed by Euadenia trifoliata stem bark (TB03) and Euadenia eminens leaf (TB05). P. aeruginosa was highly susceptible (81.81 %) to the extracts, followed by S. enteritidis (63.64 %) and then E. coli (27.27 %).

CONCLUSIONS

MJLM and other extracts have proven to be promising extracts in which to search for bioactive components that can be developed into therapeutic drugs. This may help in the management of antibiotic resistant bacterial isolates from poultry chicken threatening public health.

Resistance suppression by high-intensity, short-duration aminoglycoside exposure against hypermutable and non-hypermutable Pseudomonas aeruginosa

OBJECTIVES

Hypermutable bacteria are causing a drastic problem via their enhanced ability to become resistant. Our objectives were to compare bacterial killing and resistance emergence between differently shaped tobramycin concentration-time profiles at a given fAUC/MIC, and determine the tobramycin exposure durations that prevent resistance.

METHODS

Static concentration time-kill studies over 24 h used Pseudomonas aeruginosa WT strains (ATCC 27853 and PAO1) and hypermutable PAOΔmutS. fAUC/MIC values of 36, 72 and 168 were assessed at initial inocula of 10⁶ and 10⁴ cfu/mL (all strains) and 10^1.2 cfu/mL (PAOΔmutS only) in duplicate. Tobramycin was added at 0 h and removed at 1, 4, 10 or 24 h. Proportions of resistant bacteria and MICs were determined at 24 h. Mechanism-based modelling was conducted.

RESULTS

For all strains, high tobramycin concentrations over 1 and 4 h resulted in more rapid and extensive initial killing compared with 10 and 24 h exposures at a given fAUC/MIC. No resistance emerged for 1 and 4 h durations of exposure, although extensive regrowth of susceptible bacteria occurred. The 24 h duration of exposure revealed less regrowth, but tobramycin-resistant populations had completely replaced susceptible bacteria by 24 h for the 10⁶ cfu/mL inoculum. The hypermutable PAOΔmutS showed the highest numbers of resistant bacteria. Total and resistant bacterial counts were described well by novel mechanism-based modelling.

CONCLUSIONS

Extensive resistance emerged for 10 and 24 h durations of exposure, but not for shorter durations. The tobramycin concentration-time profile shape is vital for resistance prevention and should aid the introduction of optimized combination regimens.

Antibiotics and Antibiotic Resistance in Agroecosystems: State of the Science

We propose a simple causal model depicting relationships involved in dissemination of antibiotics and antibiotic resistance in agroecosystems and potential effects on human health, functioning of natural ecosystems, and agricultural productivity. Available evidence for each causal link is briefly summarized, and key knowledge gaps are highlighted. A lack of quantitative estimates of human exposure to environmental bacteria, in general, and antibiotic-resistant bacteria, specifically, is a significant data gap hindering the assessment of effects on human health. The contribution of horizontal gene transfer to resistance in the environment and conditions that might foster the horizontal transfer of antibiotic resistance genes into human pathogens also need further research. Existing research has focused heavily on human health effects, with relatively little known about the effects of antibiotics and antibiotic resistance on natural and agricultural ecosystems. The proposed causal model is used to elucidate gaps in knowledge that must be addressed by the research community and may provide a useful starting point for the design and analysis of future research efforts.

Efficacy of a novel antimicrobial peptide against periodontal pathogens in both planktonic and polymicrobial biofilm states

Streptococcus gordonii, Fusobacterium nucleatum and Porphyromonas gingivalis represent the early, middle and late colonizers of the bacterial accretion in dental plaque biofilms. These sessile communities constitute a protected mode of growth that promotes survival in a hostile environment. This study describes a novel and unrecognized role for a synthetic cationic antimicrobial peptide, Nal-P-113, which inhibits and kills periodontal bacteria in planktonic state, inhibits the formation of biofilms and eradicates polymicrobial biofilms. Nal-P-113 is also stable in saliva, serum and saline solution. At a concentration less than 320 μg/mL which is harmless to normal oral cells, Nal-P-113 can kill bacteria in planktonic state. At a concentration of antimicrobial peptide Nal-P-113 (1280 μg/mL) which only causes slight damages to normal oral cells is needed to kill bacteria in biofilm state. It is worth mentioning that this concentration of Nal-P-113 is harmless to rat oral mucosa compared to chlorhexidine. The mechanism of Nal-P-113 inhibiting and killing periodontal bacteria might rely on the abilities to permeabilize and/or to form pores within the cytoplasmic membranes, thus causes the death of bacteria. Here, we provided a novel and stable antimicrobial peptide with very low mammalian cytotoxicity, which can inhibit and kill periodontal bacteria in both planktonic and polymicrobial biofilm states.

STATEMENT OF SIGNIFICANCE

Nal-P-113 is a potent antimicrobial peptide with strong antimicrobial ability, improved deficiency compared with other antibacterial peptides, and remains stable in phosphate buffered saline, saliva, brain-heart infusion medium and bovine calf serum. Nal-P-113 exhibits a broad spectrum of bacteriocidal activity with excellent eradicating capability on oral pathogens and the respective biofilms. In this study, we used propidium iodide staining, scanning electron microscopy and transmission electron microscopy to confirm that Nal-P-113 can perforate plasmalemma thereby resulting in the death of oral pathogens and disintegrate the respective biofilms. Nal-P-113 also showed effective anti-plaque biofilms and cytotoxicity in the rat periodontitis model. No adverse effects can be observed on the gingivomucosa tissue. In short, the antimicrobial peptide Nal-P-113 presented to be an effective yet have low mammalian cytotoxicity agent with potential application in the clinic. This study provides a proof of concept in applying antimicrobial peptides in the clinical perspective.

Value of American Thoracic Society guidelines in predicting infection or colonization with multidrug-resistant organisms in critically ill patients

Background

The incidence rate of infection by multidrug-resistant organisms (MDROs) can affect the accuracy of etiological diagnosis when using American Thoracic Society (ATS) guidelines. We determined the accuracy of the ATS guidelines in predicting infection or colonization by MDROs over 18 months at a single ICU in eastern China.

Methods

This prospective observational study examined consecutive patients who were admitted to an intensive care unit (ICU) in Nanjing, China. MDROs were defined as bacteria that were resistant to at least three antimicrobial classes, such as methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), Pseudomonas aeruginosa, Acinetobacter baumannii. Screening for MDROs was performed at ICU admission and discharge. Risk factors for infection or colonization with MDROs were recorded, and the accuracy of the ATS guidelines in predicting infection or colonization with MDROs was documented.

Results

There were 610 patients, 225 (37%) of whom were colonized or infected with MDROs at ICU admission, and this increased to 311 (51%) at discharge. At admission, the sensitivity (70.0%), specificity (31.6%), positive predictive value (38.2%), and negative predictive value (63.5%), all based on ATS guidelines for infection or colonization with MDROs were low. The negative predictive value was greater in patients from departments with MDRO infection rates of 31–40% than in patients from departments with MDRO infection rates of 30% or less and from departments with MDRO infection rates more than 40%.

Conclusion

ATS criteria were not reliable in predicting infection or colonization with MDROs in our ICU. The negative predictive value was greater in patients from departments with intermediate rates of MDRO infection than in patients from departments with low or high rates of MDRO infection.

Trial Registration

ClinicalTrials.gov NCT01667991

Fitness and proteome changes accompanying the development of erythromycin resistance in a population of Escherichia coli grown in continuous culture

We studied the impact of a sublethal concentration of erythromycin on the fitness and proteome of a continuously cultivated population of Escherichia coli. The development of resistance to erythromycin in the population was followed over time by the gradient plate method and minimum inhibitory concentration (MIC) measurements. We measured the growth rate, standardized efficiency of synthesis of radiolabeled proteins, and translation accuracy of the system. The proteome changes were followed over time in two parallel experiments that differed in the presence or absence of erythromycin. A comparison of the proteomes at each time point (43, 68, and 103 h) revealed a group of unique proteins differing in expression. From all 35 proteins differing throughout the cultivation, only three were common to more than one time point. In the final population, a significant proportion of upregulated proteins was localized to the outer or inner cytoplasmic membranes or to the periplasmic space. In a population growing for more than 100 generations in the presence of antibiotic, erythromycin-resistant bacterial clones with improved fitness in comparison to early resistant culture predominated. This phenomenon was accompanied by distinct changes in protein expression during a stepwise, population-based development of erythromycin resistance.

Tigecycline in febrile neutropenic patients with haematological malignancies: a retrospective case documentation in four university hospitals

OBJECTIVES

Tigecycline (TGC) is a first-in-class glycylcycline with an expanded spectrum of activity. Although TGC has not been prospectively studied in febrile neutropenia (FN), we observed that occasionally critically ill neutropenic patients unresponsive to other antibiotics were treated with TGC in our departments. The aim of our study was to analyse effectiveness and toxicity of TGC in FN.

METHODS

Data of infectious episodes treated with TGC were retrospectively collected. Baseline data of patients, haematological malignancy, infection and adverse events were documented. Success was defined as defervescence (≥7 days) in the absence of any sign of persistent infection.

RESULTS

Data of 35 patients with haematological malignancies and FN were evaluated. Median duration of neutropenia was 25 days (range 6-69 days). The type of infection was pneumonia in 24 patients, four microbiologically documented infections, three clinically documented infections and four with fever of unknown origin. The TGC was administered after a median of two (range 1-5) prior antibiotic regimens. Treatment was successful in 15 (43 %) patients. In patients with prolonged neutropenia (≥28 days), response was significantly lower (13 vs. 79 %; p =0.001). Eight (23 %) patients died during the fever episode. Grade 3-4 toxicity occurred in five (14 %) patients.

CONCLUSION

Our results showed promising response rates to TGC and very low toxicity rates compared to the generally low response rate of third-line antibiotic therapies, indicating that TGC may be a successful alternative for salvage treatment of febrile neutropenia, but further study is needed.

Duration of colonization by extended-spectrum β-lactamase-producing Enterobacteriaceae after hospital discharge

BACKGROUND

The duration of gastrointestinal colonization with extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) may play a major role in the spread of these organisms. We evaluated the time to, and factors associated with, ESBL-E clearance after hospital discharge.

METHODS

We retrospectively reviewed prospective surveillance results obtained over 14 years in a 1,000-bed hospital. The surveillance collected demographic, hospital stay, microbiologic, and outcome data. An automatic alert system identified readmitted patients with prior ESBL-E carriage. ESBL-E clearance was defined as a negative rectal screening sample at readmission with no new positive clinical sample during the stay. Variables associated with ESBL-E clearance were identified using a Cox model.

RESULTS

We included 1,884 patients with 2,734 admissions. Four hundred forty-eight patients with readmission screening formed the basis for the study. Of 448 patients with 1 to 16 readmissions, 180 (40%) were persistent carriers. The median time to ESBL-E clearance was 6.6 months. Variables independently associated with clearance was having the first positive culture in a screening sample only (adjusted hazard ratio, 1.31; 95% confidence interval, 1.02-1.69; P = .04) and period 2005-2010 (hazard ratio, 1.88; 95% confidence interval, 1.33-2.67; P < .01).

CONCLUSION

We found a long duration of ESBL-E carriage after hospital discharge. An automatic alert system was useful for identifying, screening, and isolating previous ESBL-E carriers.

Liver abscesses in adult patients with and without diabetes mellitus: an analysis of the clinical characteristics, features of the causative pathogens, outcomes and predictors of fatality: a report based on a large population, retrospective study in China

In China, there are four types of liver abscesses (LAs) that meet the clinical criteria. Pyogenic liver abscesses (PLAs) and amoebic liver abscesses (ALAs) are two of the most common types of abscesses, followed by fungal liver abscesses (FLAs) and hydatid secondary liver abscesses (HsLAs). Diabetes mellitus (DM) is associated with the development of PLAs. However, there is a lack of population-based studies that have evaluated the underlying relationship between LAs (mainly PLAs and FLAs) and DM. We conducted a retrospective study based on a large population to identify the potential differences and factors that affect the mortality of PLA patients in DM and non-DM groups. Our results revealed that the prevalence of DM is 44.3% (158/357) in PLA patients and 35.3% (18/51) in FLA patients. Compared with the non-DM patients, statistically significant differences were found in DM patients according to symptomatology, clinical manifestations, laboratory findings, microbiological characteristics, antimicrobial resistance, clinical treatments and outcomes in relation to mortality. In addition, the status of antibiotic resistance to E. coli and K. pneumoniae, which were isolated from the patient samples, is severe in the area in which the study was conducted. Regarding the treatment of PLAs, our study indicated that broad-spectrum antimicrobial therapy and drug combinations should be recommended and initiated before the pathogens are cultured and identified. In the clinic, therapies that combine percutaneous drainage with antibiotics and surgery with antibiotics are the two most useful strategies for treating an LA. These two combined treatments resulted in satisfactory cure rates. In the DM and non-DM groups, the cure rates for percutaneous drainage with antibiotics were 90.3% and 92.0%, respectively, and the cure rates for surgery with antibiotics were 93.9% and 95.2%, respectively.

Synthesis and characterization of agar-based silver nanoparticles and nanocomposite film with antibacterial applications

This study describes the synthesis and characterization of silver nanoparticles and nanocomposite material using agar extracted from the red alga Gracilaria dura. Characterization of silver nanoparticles was carried out based on UV-Vis spectroscopy (421 nm), transmission electron microscopy, EDX, SAED and XRD analysis. The thermal stability of agar/silver nanocomposite film determined by TGA and DSC analysis showed distinct patterns when compared with their raw material (agar and AgNO(3)). The TEM findings revealed that the silver nanoparticles synthesized were spherical in shape, 6 nm in size with uniform dispersal. The synthesized nanoparticles had the great bactericidal activity with reduction of 99.9% of bacteria over the control value. The time required for synthesis of silver nanoparticles was found to be temperature dependent and higher the temperature less the time for nanoparticles formation. DSC and XRD showed approximately the same crystalline index (CI(DSC) 0.73).

Ion mobility spectrometry for microbial volatile organic compounds: a new identification tool for human pathogenic bacteria

Presently, 2 to 4 days elapse between sampling at infection suspicion and result of microbial diagnostics. This delay for the identification of pathogens causes quite often a late and/or inappropriate initiation of therapy for patients suffering from infections. Bad outcome and high hospitalization costs are the consequences of these currently existing limited pathogen identification possibilities. For this reason, we aimed to apply the innovative method multi-capillary column–ion mobility spectrometry (MCC-IMS) for a fast identification of human pathogenic bacteria by determination of their characteristic volatile metabolomes. We determined volatile organic compound (VOC) patterns in headspace of 15 human pathogenic bacteria, which were grown for 24 h on Columbia blood agar plates. Besides MCC-IMS determination, we also used thermal desorption–gas chromatography–mass spectrometry measurements to confirm and evaluate obtained MCC-IMS data and if possible to assign volatile compounds to unknown MCC-IMS signals. Up to 21 specific signals have been determined by MCC-IMS for Proteus mirabilis possessing the most VOCs of all investigated strains. Of particular importance is the result that all investigated strains showed different VOC patterns by MCC-IMS using positive and negative ion mode for every single strain. Thus, the discrimination of investigated bacteria is possible by detection of their volatile organic compounds in the chosen experimental setup with the fast and cost-effective method MCC-IMS. In a hospital routine, this method could enable the identification of pathogens already after 24 h with the consequence that a specific therapy could be initiated significantly earlier.

[Risk factors of nosocomial pneumonia caused by methicillin-resistant Staphylococcus aureus]

BACKGROUND AND OBJECTIVE

To include a specific antibiotic in the empiric therapy, it is necessary to predict when a nosocomial pneumonia (NP) is caused by methicillin-resistant Staphylococcus aureus (MRSA). We have developed a model for the prediction of the probability of a NP being caused by MRSA, when the carrier status and the microbiological diagnosis are unknown.

PATIENTS AND METHODS

A retrospective case-control study (1999-2005) was designed. A univariate and multivariate logistic regression was performed to identify the risk factors for suffering a NP due to MRSA. Demographic factors, related to hospitalization, immunosuppression or neutropenia, to medication and severity were included.

RESULTS

Three hundred and sixty three patients (121 cases and 242 controls) were studied. The final model of multivariate logistic regression included an age>14 years (OR 7.4, CI 95% 1.5-37.4, P<.015), NP appearance>6 days after admittance (OR 4.1, CI 95% 2.4-7,1, P<.001), NP development excluding summers (OR 2.5, CI 95% 1.2-5.2, P<.015), respiratory diseases (OR 4.9, CI 95% 1.5-15.8, P<.007) and multilobar involvement (OR 4, CI 95% 2.3-7.2, P<.001).The probability of developing a pneumonia due to MRSA was studied for each of the possible combinations and subsequently classified in minor and major criteria.

CONCLUSIONS

MRSA coverage should be included in the empirical treatment of NP when: a) an adult patient (>14 years old) presents, at least, 2 major criteria or 1 major criterion together with 2 minor criteria, and b) a patient <14 years-old has 2 major criteria as well as 2 minor criteria.

Variations and determinants of antibiotic consumption in Hungarian adult intensive care units

PURPOSE

The aim of this work was to study the use of systemic antibacterials and its possible determinants in Hungarian intensive care units (ICUs).

METHODS

Hospital pharmacy. departments provided package level dispensing data for their corresponding ICU (2006). Data were converted into defined daily doses (DDDs) and expressed as DDD per 100 patient-days and DDD per 100 admissions. Antibiotics were ranked by volume of DDDs, and the agents responsible for 90% of total use (DU90%) were noted. To explore differences and relationships between antibiotic use and antibiotic policy elements/ICU characteristics, the analysis of variances or the Pearson correlation analysis was performed.

RESULTS

Valid data were obtained for 44 ICUs. Antibiotic use varied widely (from 27.9 to 167.8 DDD per 100 patient-days and from 104.7 to 1784.6 DDD per 100 admissions). In total, 11-34 different antibacterials per ICUs were used, of which, 5-15 were in the DU90% segment. The proportional use of parenteral agents ranged from 46.2 to 98.3%. The mean of overall antibiotic use was highest for penicillins with beta-lactamase inhibitors, followed by quinolones and third-generation cephalosporins. Of the studied factors, only the ICU category (i.e., level of care) showed significant association with total antibacterial use.

CONCLUSIONS

The striking differences in total antibiotic use and the extensive use of the oral agents in some ICUs may indicate room for improvement. As none of the antibiotic policy elements were accompanied by lower antibiotic use in the pooled analysis, it suggests that--beside the ICU category--other unrevealed factors determine antibiotic use.

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).

The activity of thyme essential oil against Acinetobacter spp

The aim of this work was to investigate the antimicrobial properties of thyme essential oil against clinical multiresistant strains of Acinetobacter spp. The antibacterial activity of oil was tested against standard and clinical bacterial strains of Acinetobacter genus. The agar diffusion method was used to check the inhibition of microbial growth at various concentrations of the oil from Thymus vulgaris. Susceptibility testing to antibiotics and chemotherapeutics was prepared using the disc-diffusion method. Identification of bacterial strains was carried out with the Vitek system and confirmed by PCR for Acinetobacter baumanii gyrB gene. The results of experiments showed that the oil from T. vulgaris exhibited an extremely strong activity against all of the clinical strains of Acinetobacter. Thyme oil demonstrated a very good efficacy against multiresistant strains of tested bacteria. Essential oils seems to be an excellent alternative for synthetic preparations and that is reason for an extensive assessment of their antimicrobial activity.

Opportunities for antibiotic reduction in mechanically ventilated children

OBJECTIVE

To identify opportunities to safely reduce antibiotic use in critically ill children with moderately severe respiratory failure.

DESIGN

Prospective observational.

SETTING

Four pediatric intensive care units at three American tertiary care children's hospitals.

PATIENTS

Children aged 2 months to 18 yrs who were mechanically ventilated, had an abnormal chest radiograph, and for whom the attending physicians had initiated antibiotics for presumed bacterial pneumonia.

INTERVENTION

Nonbronchoscopic bronchoalveolar lavage.

METHODS AND MAIN RESULTS

Eligible children were subjected to nonbronchoscopic bronchoalveolar lavage within 12 hrs of initiating antibiotics. The concentration of bacteria in the lavage fluid was determined by quantitative assay, and the diagnosis of pneumonia was confirmed if >10 (4)pathogenic bacteria/mL were cultivated. Twenty-one subjects were enrolled, in whom 20 nonbronchoscopic bronchoalveolar lavage procedures were completed. Six of 20 subjects had nonbronchoscopic bronchoalveolar lavage results confirmatory of bacterial pneumonia, three additional subjects had bacteria isolated at concentrations below levels conventionally used to diagnose bacterial pneumonia, and the remaining 11 demonstrated no growth. Clinical parameters reflective of severity of disease and laboratory parameters reflective of systemic and local inflammation were tested for their association with a positive nonbronchoscopic bronchoalveolar lavage, but none was demonstrated.

CONCLUSIONS

Eleven of 20 mechanically ventilated children treated with antibiotics for presumed infectious pneumonia had undetectable concentrations of bacteria in their lower respiratory tract, and three others had organisms present at low concentrations, suggesting that opportunities exist to reduce antibiotic exposure in this population.

Blockade of gC1qR/p33, a receptor for C1q, inhibits adherence of Staphylococcus aureus to the microvascular endothelium

Endovascular infections with Staphylococcus aureus (S. aureus) are associated with high mortality. gC1qR/p33 (gC1qR), a receptor for the complement component C1q expressed on endothelial cells, interacts with protein A of S. aureus and gC1qR blockade reduces S. aureus colonization during infective endocarditis. The aim of this study was to analyze in vivo whether this observation is due to a decreased interaction of S. aureus with the microvascular endothelium. A dorsal skinfold chamber was prepared in Syrian golden hamsters, which were treated with the monoclonal antibody (MAb) 74.5.2 directed against gC1qR or vehicle. The interaction of fluorescein isothiocyanate (FITC)-labeled staphylococci and leukocytes with the endothelium was analyzed under physiological conditions as well as after TNF-α-induced inflammation using intravital fluorescence microscopy. Administration of MAb 74.5.2 significantly reduced adherence of S. aureus to the endothelium in untreated and TNF-α-exposed tissue. In addition, we could demonstrate in vitro that S. aureus adherence to human endothelial cells was inhibited by MAb 74.5.2. Blockade of gC1qR did not affect leukocyte-endothelial cell interaction. In conclusion, our findings indicate that immunological inhibition of gC1qR may be therapeutically used to decrease the interaction of S. aureus with the microvascular endothelium.

On being the right size: the impact of population size and stochastic effects on the evolution of drug resistance in hospitals and the community

The evolution of drug resistant bacteria is a severe public health problem, both in hospitals and in the community. Currently, some countries aim at concentrating highly specialized services in large hospitals in order to improve patient outcomes. Emergent resistant strains often originate in health care facilities, but it is unknown to what extent hospital size affects resistance evolution and the resulting spillover of hospital-associated pathogens to the community. We used two published datasets from the US and Ireland to investigate the effects of hospital size and controlled for several confounders such as antimicrobial usage, sampling frequency, mortality, disinfection and length of stay. The proportion of patients acquiring both sensitive and resistant infections in a hospital strongly correlated with hospital size. Moreover, we observe the same pattern for both the percentage of resistant infections and the increase of hospital-acquired infections over time. One interpretation of this pattern is that chance effects in small hospitals impede the spread of drug-resistance. To investigate to what extent the size distribution of hospitals can directly affect the prevalence of antibiotic resistance, we use a stochastic epidemiological model describing the spread of drug resistance in a hospital setting as well as the interaction between one or several hospitals and the community. We show that the level of drug resistance typically increases with population size: In small hospitals chance effects cause large fluctuations in pathogen population size or even extinctions, both of which impede the acquisition and spread of drug resistance. Finally, we show that indirect transmission via environmental reservoirs can reduce the effect of hospital size because the slow turnover in the environment can prevent extinction of resistant strains. This implies that reducing environmental transmission is especially important in small hospitals, because such a reduction not only reduces overall transmission but might also facilitate the extinction of resistant strains. Overall, our study shows that the distribution of hospital sizes is a crucial factor for the spread of drug resistance.

The increasing spread of bacteria, which are resistant to antibiotics, is a serious threat to clinical care. Currently, several countries aim at concentrating highly specialized services in large hospitals in order to improve patient outcomes. However, empirical studies have shown that resistance levels correlate with hospital size. To illustrate this correlation, we analyze two published datasets from the US and Ireland and controlled for antimicrobial usage, disinfection and length of stay. The proportion of patients acquiring both sensitive and resistant infections in hospitals strongly correlated with hospital size. Moreover, we observe the same pattern for both the percentage of resistant infections and the temporal increase of hospital-acquired infections. To investigate to what extent hospital size can directly affect the prevalence of antibiotic resistance, we use mathematical models describing the epidemic spread of resistance in hospitals and the community. We find that small hospitals typically lead to considerably lower resistance levels than large hospitals. However, this beneficial effect of small hospital size may be reduced if bacteria are transmitted indirectly via the environment. Therefore, reducing environmental transmission might be particularly important in small hospitals. Overall, our findings suggest that the short-term benefits of larger hospitals may come at the price of increasing resistance in the long term.

Risk of acquiring multidrug-resistant Gram-negative bacilli from prior room occupants in the intensive care unit

The objective of this prospective cohort study was to determine whether admission to an intensive care unit (ICU) room previously occupied by a patient with multidrug-resistant (MDR) Gram-negative bacilli (GNB) increases the risk of acquiring these bacteria by subsequent patients. All patients hospitalized for >48 h were eligible. Patients with MDR GNB at ICU admission were excluded. The MDR GNB were defined as MDR Pseudomonas aeruginosa, Acinetobacter baumannii and extended spectrum β-lactamase (ESBL) -producing GNB. All patients were hospitalized in single rooms. Cleaning of ICU rooms between two patients was performed using quaternary ammonium disinfectant. Risk factors for MDR P. aeruginosa, A. baumannii and ESBL-producing GNB were determined using univariate and multivariate analysis. Five hundred and eleven consecutive patients were included; ICU-acquired MDR P. aeruginosa was diagnosed in 82 (16%) patients, A. baumannii in 57 (11%) patients, and ESBL-producing GNB in 50 (9%) patients. Independent risk factors for ICU-acquired MDR P. aeruginosa were prior occupant with MDR P. aeruginosa (OR 2.3, 95% CI 1.2-4.3, p 0.012), surgery (OR 1.9, 95% CI 1.1-3.6, p 0.024), and prior piperacillin/tazobactam use (OR 1.2, 95% CI 1.1-1.3, p 0.040). Independent risk factors for ICU-acquired A. baumannii were prior occupant with A. baumannii (OR 4.2, 95% CI 2-8.8, p <0.001), and mechanical ventilation (OR 9.3, 95% CI 1.1-83, p 0.045). Independent risk factors for ICU-acquired ESBL-producing GNB were tracheostomy (OR 2.6, 95% CI 1.1-6.5, p 0.049), and sedation (OR 6.6, 95% CI 1.1-40, p 0.041). We conclude that admission to an ICU room previously occupied by a patient with MDR P. aeruginosa or A. baumannii is an independent risk factor for acquisition of these bacteria by subsequent room occupants. This relationship was not identified for ESBL-producing GNB.

Moenomycin family antibiotics: chemical synthesis, biosynthesis, and biological activity

The review (with 214 references cited) is devoted to moenomycins, the only known group of antibiotics that directly inhibit bacterial peptidoglycan glycosytransferases. Naturally occurring moenomycins and chemical and biological approaches to their derivatives are described. The biological properties of moenomycins and plausible mechanisms of bacterial resistance to them are also covered here, portraying a complete picture of the chemistry and biology of these fascinating natural products

Bacteremia in Staphylococcus aureus pneumonia: outcomes and epidemiology

PURPOSE

Staphylococcus aureus represents a major cause of pneumonia in critically ill patients. Although bacteremia may complicate S aureus pneumonia, the epidemiology of and outcomes associated with bacteremia in this syndrome are poorly described.

MATERIALS AND METHODS

We retrospectively identified (January 2005-December 2007) all patients admitted to the hospital with S aureus pneumonia necessitating mechanical ventilation. All subjects underwent lower airway and concurrent blood cultures. The prevalence of bacteremia served as a primary end point. We assessed the impact of bacteremia on mortality and length of stay via either logistic regression or a Cox proportional hazard model, respectively. In both models, we controlled for multiple covariates (eg, demographics, severity of illness, comorbidities, and appropriateness of initial antibiotics). We subsequently developed a prediction rule to identify subjects likely to have concurrent bacteremia based on variables assessed at the time of presentation.

RESULTS

The cohort included 59 patients (mean ± SD age, 58.0 ± 17.4 years; 55.9% male, 59.3% methicillin resistant, 39.0% crude mortality). Bacteremia complicated nearly 20% of cases. The mortality rate in those with bacteremia was 39.1% vs 8.3% in persons without bacteremia (P = .007). Three variables were independently associated with mortality in S aureus pneumonia: age, need for vasopressors, and concurrent bacteremia. Bacteremia independently conferred a 6-fold increase in the risk for death (adjusted odds ratio, 5.96; 95% confidence interval [CI], 1.08-33.10). Bacteremia also correlated with a longer length of stay. The adjusted hazard ratio for remaining hospitalized if bacteremic was 2.65 (95% CI, 1.14-6.18). For the clinical prediction rule for concurrent bacteremia, we assigned points as follows: 2 points if the patient had received prior antibiotic therapy and 1 point each for acute lung injury and for the need for vasopressors. As the total score increased, the prevalence of bacteremia increased (P < .001). As a screening test for bacteremia in S aureus pneumonia, the scoring system had good predictive value. The area under the receiver operating curve measured 0.83 (95% CI, 0.72-0.94).

CONCLUSIONS

Bacteremia often arises in S aureus pneumonia and is associated with both increased morbidity and mortality. Several simple clinical factors to determine clinical features identify patients with S aureus pneumonia likely to have simultaneous bacteremia.

Effects of antibacterial mineral leachates on the cellular ultrastructure, morphology, and membrane integrity of Escherichia coli and methicillin-resistant Staphylococcus aureus

Background

We have previously identified two mineral mixtures, CB07 and BY07, and their respective aqueous leachates that exhibit in vitro antibacterial activity against a broad spectrum of pathogens. The present study assesses cellular ultrastructure and membrane integrity of methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli after exposure to CB07 and BY07 aqueous leachates.

Methods

We used scanning and transmission electron microscopy to evaluate E. coli and MRSA ultrastructure and morphology following exposure to antibacterial leachates. Additionally, we employed Baclight LIVE/DEAD staining and flow cytometry to investigate the cellular membrane as a possible target for antibacterial activity.

Results

Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) imaging of E. coli and MRSA revealed intact cells following exposure to antibacterial mineral leachates. TEM images of MRSA showed disruption of the cytoplasmic contents, distorted cell shape, irregular membranes, and distorted septa of dividing cells. TEM images of E. coli exposed to leachates exhibited different patterns of cytoplasmic condensation with respect to the controls and no apparent change in cell envelope structure. Although bactericidal activity of the leachates occurs more rapidly in E. coli than in MRSA, LIVE/DEAD staining demonstrated that the membrane of E. coli remains intact, while the MRSA membrane is permeabilized following exposure to the leachates.

Conclusions

These data suggest that the leachate antibacterial mechanism of action differs for Gram-positive and Gram-negative organisms. Upon antibacterial mineral leachate exposure, structural integrity is retained, however, compromised membrane integrity accounts for bactericidal activity in Gram-positive, but not in Gram-negative cells.

Eradication of Pathogenic Bacteria by Remote Delivery of Nitric Oxide via Light-Triggering of Nitrosyl-Containing Materials

Although nitric oxide (NO) delivery systems have been fabricated with sol-gel-based materials, remote control of such systems with light has not been achieved. In this work, a fiber optic-based NO delivery system is described in which the photoactive metal-nitrosyl, [Mn(PaPy(3))(NO)]ClO(4) (1), has been employed in a sol-gel material. The material (1*FO) contains the manganese-nitrosyl which releases NO upon illumination with visible light. The NO-releasing capacity of 1*FO has been measured with an NO-sensitive electrode and the spatial diffusion of NO in solution has been visualized using the Griess reaction. The utility of 1*FO has been demonstrated in effective reduction of bacterial loads of Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus (MRSA). The results suggest that a device that releases NO via illumination by optical fiber may have clinical applications in combating infections with both Gram-positive, Gram-negative and to some degree antibiotic resistant bacteria.

Discovery and optimization of antibacterial AccC inhibitors

The biotin carboxylase (AccC) is part of the multi-component bacterial acetyl coenzyme-A carboxylase (ACCase) and is essential for pathogen survival. We describe herein the affinity optimization of an initial hit to give 2-(2-chlorobenzylamino)-1-(cyclohexylmethyl)-1H-benzo[d]imidazole-5-carboxamide (1), which was identified using our proprietary Automated Ligand Identification System (ALIS).(1) The X-ray co-crystal structure of 1 was solved and revealed several key interactions and opportunities for further optimization in the ATP site of AccC. Structure Based Drug Design (SBDD) and parallel synthetic approaches resulted in a novel series of AccC inhibitors, exemplified by (R)-2-(2-chlorobenzylamino)-1-(2,3-dihydro-1H-inden-1-yl)-1H-imidazo[4,5-b]pyridine-5-carboxamide (40). This compound is a potent and selective inhibitor of bacterial AccC with an IC(50) of 20 nM and a MIC of 0.8 microg/mL against a sensitized strain of Escherichia coli (HS294 E. coli).

Novel broad-spectrum bis-(imidazolinylindole) derivatives with potent antibacterial activities against antibiotic-resistant strains

Given the limited number of structural classes of clinically available antimicrobial drugs, the discovery of antibacterials with novel chemical scaffolds is an important strategy in the development of effective therapeutics for both naturally occurring and engineered resistant strains of pathogenic bacteria. In this study, several diarylamidine derivatives were evaluated for their ability to protect macrophages from cell death following infection with Bacillus anthracis, a gram-positive spore-forming bacterium. Four bis-(imidazolinylindole) compounds were identified with potent antibacterial activity as measured by the protection of macrophages and by the inhibition of bacterial growth in vitro. These compounds were effective against a broad range of gram-positive and gram-negative bacterial species, including several antibiotic-resistant strains. Minor structural variations among the four compounds correlated with differences in their effects on bacterial macromolecular synthesis and mechanisms of resistance. In vivo studies revealed protection by two of the compounds of mice lethally infected with B. anthracis, Staphylococcus aureus, or Yersinia pestis. Taken together, these results indicate that the bis-(imidazolinylindole) compounds represent a new chemotype for the development of therapeutics for both gram-positive and gram-negative bacterial species as well as against antibiotic-resistant infections.