Antibiotic-resistant Bacterial Pathogens Research Articles

Marching towards Making Evolution-Proof Antibiotics

Antibiotic resistance in bacterial pathogens has increased to alarming levels and warrants immediate attention Traditional antibiotics kill the bacteria by targeting the bacterial structures and mechanisms that are essential for their survival putting great selection pressure to develop resistance Anti virulence drugs are new class of therapeutic targets being investigated to tackle this crisis As anti virulence drugs disarm the pathogen rather than killing it may pose less selection pressure on bacteria to develop resistance

Quinolone Resistance Reversion by Targeting the SOS Response.

ABSTRACTSuppression of the SOS response has been postulated as a therapeutic strategy for potentiating antimicrobial agents. We aimed to evaluate the impact of its suppression on reversing resistance using a model of isogenic strains of Escherichia coli representing multiple levels of quinolone resistance. E. coli mutants exhibiting a spectrum of SOS activity were constructed from isogenic strains carrying quinolone resistance mechanisms with susceptible and resistant phenotypes. Changes in susceptibility were evaluated by static (MICs) and dynamic (killing curves or flow cytometry) methodologies. A peritoneal sepsis murine model was used to evaluate in vivo impact. Suppression of the SOS response was capable of resensitizing mutant strains with genes encoding three or four different resistance mechanisms (up to 15-fold reductions in MICs). Killing curve assays showed a clear disadvantage for survival (Δlog10 CFU per milliliter [CFU/ml] of 8 log units after 24 h), and the in vivo efficacy of ciprofloxacin was significantly enhanced (Δlog10 CFU/g of 1.76 log units) in resistant strains with a suppressed SOS response. This effect was evident even after short periods (60 min) of exposure. Suppression of the SOS response reverses antimicrobial resistance across a range of E. coli phenotypes from reduced susceptibility to highly resistant, playing a significant role in increasing the in vivo efficacy.

Inhibición de enterobacterias portadoras de carbapenemasas con secreciones peptídicas de anfibios nativos ecuatorianos.

La resistencia bacteriana representa un problema para la salud pública, especialmente la producida por enzimas llamadas betalactamasas, que bloquean a un grupo importante de antibióticos, los betalactámicos, utilizados ampliamente para el tratamiento de infecciones en seres humanos. Las enterobacterias productoras de betalactamasas de espectro extendido (BLEEs) son las más preocupantes, pues son un grupo importante dentro de la etiología de las infecciones tanto severas como no severas.
 Los carbapenemes son antibióticos betalactámicos para el tratamiento de infecciones causadas por enterobacterias BLEE, que están resultando ineficientes por el aparecimiento de cepas resistentes a estos antibióticos. Ante la escasez de otras opciones terapéuticas, el presente estudio tuvo como objetivo caracterizar molecularmente carbapenemasas en enterobacterias y analizar su posible inhibición con secreciones peptídicas de un bufónido nativo ecuatoriano. Se caracterizaron 57 enterobacterias resistentes a carbapenemes de pacientes hospitalizados. Esta población fue caracterizada molecularmente, encontrándose los genes blaKPC, blaGES, blaVIM y blaIMP. Los genes con mayor prevalencia fueron blaKPC y blaGES, seguidos por blaVIM y blaIMP. Todos los aislados fueron inhibidos por el péptido. La concentración inhibitoria mínima fue 250 μg/ml para Klebsiella pneumoniae, Serratia marcescens, Enterobacter aerogenes y E. cloacae, 125 μg/ml para Morganella morganii, 62.5 μg/ml para Klebsiella oxytoca y Serratia rubidaea y 31.3 μg/ml para Escherichia coli. La presencia de genes para betalactamasas en elementos móviles facilita su propagación.
 Por esta razón la importancia de analizar nuevos compuestos antimicrobianos.

In vitro evaluation of selected medicinal plants for antimicrobial activities against antibiotic resistant clinical bacterial and fungal pathogens

In vitro evaluation of selected medicinal plants for antimicrobial activities against antibiotic resistant clinical bacterial and fungal pathogens

Microbial approaches for targeting antibiotic-resistant bacteria.

SummaryAntibiotic resistant bacterial infections are a global public health challenge that has been increasing in severity and scope for the last few decades. Without creative solutions to this problem, treatment of injuries and infections will become progressively more challenging. A better understanding of the human microbiome has led to a new appreciation for the role commensal microbes play in protecting us from pathogens, especially in the gut. Antibiotics lead to disruption of the gut microbial ecosystem, enabling colonization by antibiotic resistant bacterial pathogens. Many different lines of research have identified specific bacterial taxa and mechanisms that play a role in colonization resistance, and these lines of research may one day lead to microbial therapeutics targeting antibiotic resistant bacteria. Here, we discuss a few of these strategies and the challenges they will need to overcome in order to become an effective therapeutic.

Phage therapy: an alternative or adjunct to antibiotics?

Phage therapy is currently discussed as an alternative or adjunct to antibiotics whose activity is increasingly compromised by the emergence of antibiotic-resistant bacterial pathogens. The idea to use lytic bacterial viruses as antimicrobial agents is nearly a century old and is common practice in Eastern Europe. However, safety concerns and lack of controlled clinical trials proving the efficacy of phage therapy have hampered its wider medical use in the West. The present review analyzes safety aspects and compares successful with unsuccessful phage therapy clinical trials to identify potential factors determining success and failure of this approach.

Genomic Analysis of Factors Associated with Low Prevalence of Antibiotic Resistance in Extraintestinal Pathogenic Escherichia coli Sequence Type 95 Strains.

Extraintestinal pathogenic Escherichia coli (ExPEC) strains belonging to multilocus sequence type 95 (ST95) are globally distributed and a common cause of infections in humans and domestic fowl. ST95 isolates generally show a lower prevalence of acquired antimicrobial resistance than other pandemic ExPEC lineages. We took a genomic approach to identify factors that may underlie reduced resistance. We fully assembled genomes for four ST95 isolates representing the four major fimH-based lineages within ST95 and also analyzed draft-level genomes from another 82 ST95 isolates, largely from the western United States. The fully assembled genomes of antibiotic-resistant isolates carried resistance genes exclusively on large (>90-kb) IncFIB/IncFII plasmids. These replicons were common in the draft genomes as well, particularly in antibiotic-resistant isolates, but we also observed multiple instances of a smaller (8.3-kb) ampicillin resistance plasmid that had been previously identified in Salmonella enterica. Among ST95 isolates, pansusceptibility to antibiotics was significantly associated with the fimH6 lineage and the presence of homologs of the previously identified 114-kb IncFIB/IncFII plasmid pUTI89, both of which were also associated with reduced carriage of other plasmids. Potential mechanistic explanations for lineage- and plasmid-specific effects on the prevalence of antibiotic resistance within the ST95 group are discussed. IMPORTANCE Antibiotic resistance in bacterial pathogens is a major public health concern. This work was motivated by the observation that only a small proportion of ST95 isolates, a major pandemic lineage of extraintestinal pathogenic E.coli, have acquired antibiotic resistance, in contrast to many other pandemic lineages. Understanding bacterial genetic factors that may prevent acquisition of resistance could contribute to the development of new biological, medical, or public health strategies to reduce antibiotic-resistant infections.

Synergistic Action of Silver Nanoparticles Synthesized from Silver Resistant Estuarine Pseudomonas aeruginosa Strain SN5 with Antibiotics against Antibiotic Resistant Bacterial Human Pathogens

This study focuses on the extracellular synthesis of silver nanoparticles (AgNPs), carried out using the culture supernatant of silver resistant Pseudomonas aeruginosa strain SN5 isolated from Mandovi estuarine mangrove water sample. AgNPs were characterized using X-Ray diffraction (XRD) analysis which showed high intensity peaks at 28° and 32.5°, characteristic of silver oxide (Ag2O) and confirmed its crystalline nature by referring Joint Committee on Powder Diffraction Standards (JCPDS), File No. 00–076-1393. Transmission electron microscopy (TEM) analysis revealed the nano sized AgNPS particles in the range of 35 nm – 60 nm. AgNPs showed antibacterial activity against both standard cultures of Gram positive and Gram negative bacterial human pathogens. Moreover, the AgNPs also showed antibacterial activity against ampicillin resistant Staphylococccus aureus strain VN3 and ciprofloxacin resistant Vibrio cholera strain VN1 isolated from Mandovi estuary, Goa India, polluted with human feces, domestic and hotel waste. These AgNPs exhibited better antibacterial activity as compared to AgNPs synthesized from plant extract of Honey suckle mistletoe and star anise. Interestringly, synergistic activity was observed when synthesized AgNPs were used in combination with antibiotics ampicillin and ciprofloxacin against ampicillin resistant Staphylococccus aureus strain VN3 and ciprofloxacin resistant Vibrio cholera strain VN1. Thus these AgNPs can be employed in cosmetics and wound dressings as a nanoweapon to control human bacterial pathogens.

Digest: Beating pathogens at their own game.

Absract In recent years, the evolution of antibiotic-resistant bacterial pathogens has prompted searches for new ways to control them. While many studies have focused on discovering new antimicrobials, fewer have looked at the ecological interactions that control pathogenic bacteria. Pathogenic bacteria are embedded in multi-species microbial communities where they interact with other bacterial species and their own parasitic enemies, bacteriophages (viruses that infect bacteria; also called phages). Interactions with these other microbes may hinder, benefit, or have no effect on the pathogen. In particular, species that interact antagonistically with the pathogen could be used to control its spread. Competing bacterial species, for example, may reduce the pathogen's growth by impeding access to space and nutrients, or by producing antimicrobial metabolites or other toxins that specifically target and harm the pathogen. Similarly, bacterial pathogens could be infected and killed by phages (Wang et al. 2017). This article is protected by copyright. All rights reserved

Evolution of antibiotic resistance is linked to any genetic mechanism affecting bacterial duration of carriage

Understanding how changes in antibiotic consumption affect the prevalence of antibiotic resistance in bacterial pathogens is important for public health. In a number of bacterial species, including Streptococcus pneumoniae, the prevalence of resistance has remained relatively stable despite prolonged selection pressure from antibiotics. The evolutionary processes allowing the robust coexistence of antibiotic sensitive and resistant strains are not fully understood. While allelic diversity can be maintained at a locus by direct balancing selection, there is no evidence for such selection acting in the case of resistance. In this work, we propose a mechanism for maintaining coexistence at the resistance locus: linkage to a second locus that is under balancing selection and that modulates the fitness effect of resistance. We show that duration of carriage plays such a role, with long duration of carriage increasing the fitness advantage gained from resistance. We therefore predict that resistance will be more common in strains with a long duration of carriage and that mechanisms maintaining diversity in duration of carriage will also maintain diversity in antibiotic resistance. We test these predictions in S. pneumoniae and find that the duration of carriage of a serotype is indeed positively correlated with the prevalence of resistance in that serotype. These findings suggest heterogeneity in duration of carriage is a partial explanation for the coexistence of sensitive and resistant strains and that factors determining bacterial duration of carriage will also affect the prevalence of resistance.

RelA Mutant Enterococcus faecium with Multiantibiotic Tolerance Arising in an Immunocompromised Host.

ABSTRACTSerious bacterial infections in immunocompromised patients require highly effective antibacterial therapy for cure, and thus, this setting may reveal novel mechanisms by which bacteria circumvent antibiotics in the absence of immune pressure. Here, an infant with leukemia developed vancomycin-resistant Enterococcus faecium (VRE) bacteremia that persisted for 26 days despite appropriate antibiotic therapy. Sequencing of 22 consecutive VRE isolates identified the emergence of a single missense mutation (L152F) in relA, which constitutively activated the stringent response, resulting in elevated baseline levels of the alarmone guanosine tetraphosphate (ppGpp). Although the mutant remained susceptible to both linezolid and daptomycin in clinical MIC testing and during planktonic growth, it demonstrated tolerance to high doses of both antibiotics when growing in a biofilm. This biofilm-specific gain in resistance was reflected in the broad shift in transcript levels caused by the mutation. Only an experimental biofilm-targeting ClpP-activating antibiotic was able to kill the mutant strain in an established biofilm. The relA mutation was associated with a fitness trade-off, forming smaller and less-well-populated biofilms on biological surfaces. We conclude that clinically relevant relA mutations can emerge during prolonged VRE infection, causing baseline activation of the stringent response, subsequent antibiotic tolerance, and delayed eradication in an immunocompromised state.

How Can We Effectively Combat Antibiotic Resistant Bacterial Pathogens?

How Can We Effectively Combat Antibiotic Resistant Bacterial Pathogens?

The Whys and Wherefores of Antibiotic Resistance.

The development and rapid dissemination of antibiotic-resistant bacterial pathogens has tarnished the dream of a world without infectious diseases. However, our understanding of these processes, paired with sequence information from terrestrial bacterial populations, indicates that there is no shortage of novel natural products that could be developed into new medicines. Regardless, their therapeutic success in the clinic will depend on the introduction of mandatory controls and use restrictions.

Prevalence and antibiotic resistance of bacterial pathogens isolated from childhood diarrhea in Beijing, China (2010-2014).

BackgroundDiarrhea is one of the main causes of morbidity and mortality among children less than 5 years of age worldwide, and its causes vary by region. This study aimed to determine the etiologic spectrum, prevalent characteristics and antimicrobial resistance patterns of common enteropathogenic bacteria from diarrheagenic children in Beijing, the capital of China.MethodsStool samples were collected from 2524 outpatients who were aged 0–5 years in Beijing, China during 2010–2014. Microbiological methods, real-time PCR and antimicrobial susceptibility test were used to identify the bacterial causes and antimicrobial resistance patterns in the isolates.ResultsOf the 2524 patients screened, we identified the causes of 269 cases (10.7 %) as follows: diarrheagenic Escherichia coli (4.6 %), Salmonella (4.3 %), Shigella (1.4 %) and Vibrio parahaemolyticus (0.4 %). Atypical EPEC, Salmonella enteritidis, Shigella sonnei and serotype O3:K6 were the most common serogroups or serotypes of the four etiological bacteria. The prevalence of pathogens was correlated with age, season and clinical symptoms. The highest proportion of all causative bacteria was found in children aged 3–5 years and in summer. The clinical symptoms associated with specific bacterial infection, such as fever; abdominal pain; vomiting; and watery, mucus, and bloody stool, were observed frequently in diarrheal patients. Salmonella showed moderate rates of resistance (40–60 %) to ampicillin, nalidixic acid, streptomycin and sulfisoxazole. Resistance to at least three antimicrobials was found in 50 % of isolates. Of the top three serotypes in Salmonella, high-level antimicrobial resistance to single and multiple antibiotics was more common among Salmonella typhimurium and Salmonella 1, 4, [5], 12:i:- than among S. enteritidis. More than 90 % of Shigella isolates showed more alarming resistance to most antibiotics, with a widened spectrum compared to Salmonella.ConclusionConstant antibiotic surveillance is warranted because the bacteria were highly resistant to various antimicrobials. Our study contributes to the strengthening of the existing surveillance system and provides aid for effective prevention and control strategies for childhood diarrhea.Electronic supplementary materialThe online version of this article (doi:10.1186/s13099-016-0116-2) contains supplementary material, which is available to authorized users.

Bacterial genomics: Microbial GWAS coming of age.

A linear-mixed modelling genome-wide association approach for detecting genes and genetic variants underlying antibiotic resistance in bacterial pathogens heralds a new era for microbial genome-wide association studies.

Innate Lymphocyte/Ly6Chi Monocyte Crosstalk Promotes Klebsiella Pneumoniae Clearance

Increasing antibiotic resistance among bacterial pathogens has rendered some infections untreatable with available antibiotics. Klebsiella pneumoniae, abacterial pathogen that has acquired high-level antibiotic resistance, is a common cause of pulmonary infections. Optimal clearance of K.pneumoniae from the host lung requires TNF and IL-17A. Herein, we demonstrate that inflammatory monocytes are rapidly recruited to the lungs of K.pneumoniae-infected mice and produce TNF, which markedly increases the frequency of IL-17-producing innate lymphoid cells. While pulmonary clearance of K.pneumoniae is preserved in neutrophil-depleted mice, monocyte depletion or TNF deficiency impairs IL-17A-dependent resolution of pneumonia. Monocyte-mediated bacterial uptake and killing is enhanced by ILC production of IL-17A, indicating that innate lymphocytes engage in a positive-feedback loop with monocytes that promotes clearance of pneumonia. Innate immune defense against a highly antibiotic-resistant bacterial pathogen depends on crosstalk between inflammatory monocytes and innate lymphocytes that is mediated by TNF and IL-17A.

Counteracting selection for antibiotic-resistant bacteria.

The occurrence of antibiotic-resistant bacterial pathogens is on the rise because antibiotics exert selection pressure that kills only the antibiotic-sensitive pathogens. Sanitation and cleansing of hospital surfaces and the skin of medical personnel do not counteract this selective pressure, but rather indiscriminately reduce total pathogens on treated surfaces. Here, we discuss two recently introduced genetic strategies, based on temperate bacteriophages as DNA-delivery vehicles, that aim to sensitize bacteria to antibiotics and selectively kill the antibiotic-resistant ones. Outlooks for rendering one such approach more efficient and applicable are proposed. We believe that using an end product designed according to the provided principles on hospital surfaces and in hand-sanitizers will facilitate substitution of antibiotic-resistant pathogens with sensitive ones.

Isolation and characterization of lytic phages TSE1-3 against Enterobacter cloacae

AbstractThe emergence of antibiotic resistant bacterial pathogens is becoming a major challenge for patient care. The utilization of alternative therapies for infectious diseases other than antibiotics is an urgent need of today medical practice. The utilization of lytic bacteriophages and their gene products as therapeutic agents against antibiotic resistant bacteria is one of the convincing alternative approaches. Here we present the isolation and characterization of three lytic bacteriophages TSE1-3 against

Antimicrobial susceptibility and emerging resistance determinants (blaCTX-M, rmtB, fosA3) in clinical isolates from urinary tract infections in the Bolivian Chaco.

Bolivia is among the lowest-resourced South American countries, with very few data available on antibiotic resistance in bacterial pathogens. The phenotypic and molecular characterization of bacterial isolates responsible for urinary tract infections (UTIs) in the Bolivian Chaco are reported here. All clinical isolates from UTIs collected in the Hospital Basico Villa Montes between June 2010 and January 2014 were analyzed (N=213). Characterization included susceptibility testing, extended-spectrum beta-lactamase (ESBL) detection, identification of relevant resistance determinants (e.g., CTX-M-type ESBLs, 16S rRNA methyltransferases, glutathione S-transferases), and genotyping of CTX-M producers. Very high resistance rates were observed. Overall, the lowest susceptibility was observed for trimethoprim-sulphamethoxazole, tetracycline, nalidixic acid, amoxicillin-clavulanic acid, ciprofloxacin, and gentamicin. Of E. coli and K. pneumoniae, 11.6% were ESBL producers. Resistance to nitrofurantoin, amikacin, and fosfomycin remained low, and susceptibility to carbapenems was fully preserved. CTX-M-15 was the dominant CTX-M variant. Four E. coli ST131 (two being H30-Rx) were identified. Of note, isolates harbouring rmtB and fosA3 were detected. Bolivia is not an exception to the very high resistance burden affecting many South American countries. Optimization of alternative approaches to monitor local antibiotic resistance trends in resource-limited settings is strongly encouraged to support the implementation of effective empiric treatment guidelines.

Joint Transcriptional Control of Virulence and Resistance to Antibiotic and Environmental Stress in Acinetobacter baumannii.

ABSTRACTThe increasing emergence of antibiotic-resistant bacterial pathogens represents a serious risk to human health and the entire health care system. Many currently circulating strains of Acinetobacter baumannii exhibit resistance to multiple antibiotics. A key limitation in combating A. baumannii is that our understanding of the molecular mechanisms underlying the pathogenesis of A. baumannii is lacking. To identify potential virulence determinants of a contemporary multidrug-resistant isolate of A. baumannii, we used transposon insertion sequencing (TnSeq) of strain AB5075. A collection of 250,000 A. baumannii transposon mutants was analyzed for growth within Galleria mellonella larvae, an insect-based infection model. The screen identified 300 genes that were specifically required for survival and/or growth of A. baumannii inside G. mellonella larvae. These genes encompass both known, established virulence factors and several novel genes. Among these were more than 30 transcription factors required for growth in G. mellonella. A subset of the transcription factors was also found to be required for resistance to antibiotics and environmental stress. This work thus establishes a novel connection between virulence and resistance to both antibiotics and environmental stress in A. baumannii.