The emergence and evolution of antimicrobial resistance: Impact on a global scale

Antimicrobial stewardship markers and healthcare-associated pneumonia threshold criteria in UK hospitals: analysis of the MicroGuideTm application

Background

To address antimicrobial resistance, antimicrobial stewardship (AMS) principles must be implemented and adhered to. Clinical decision aids such as the MicroGuideTM app are an important part of these efforts. We sought to evaluate the consistency of core AMS information and the diversity of classification thresholds for healthcare-associated pneumonia (HAP) in the MicroGuide app.

Methods

Guidelines in the MicroGuide app were extracted and analysed for content related to AMS and HAP. Guidelines were characterized according to HAP naming classification; community-acquired pneumonia (CAP) classifications were analysed to serve as a comparator group.

Results

In total, 115 trusts (119 hospitals) were included. Nearly all hospitals had developed MicroGuide sections on AMS (n = 112/119, 94%) and sepsis management (n = 117/119, 98%). Other AMS sections were outpatient parenteral antimicrobial therapy (47%), antifungal stewardship (70%), critical care (23%) and IV to oral switch therapy (83%). Only 9% of hospitals included guidance on the maximum six key AMS sections identified. HAP definitions varied widely across hospitals with some classifying by time to onset and some classifying by severity or complexity. The largest proportion of HAP guidelines based classification on severity/complexity (n = 69/119, 58%). By contrast, definitions in CAP guidelines were uniform.

Conclusions

The high heterogeneity in HAP classification identified suggests inconsistency of practice in identifying thresholds for HAP in the UK. This complicates HAP management and AMS practices. To address HAP in alignment with AMS principles, a comprehensive strategy that prioritizes uniform clinical definitions and thresholds should be developed.

A review of current antibiotic resistance and promising antibiotics with novel modes of action to combat antibiotic resistance

The emergence and transmission of antibiotic resistance is a global public health crisis with significant burden on healthcare systems, resulting in high mortality and economic costs. In 2019, almost five million deaths were associated with drug-resistant infections, and if left unchecked, the global economy could lose $100 trillion by 2050. To effectively combat this crisis, it is essential for all countries to understand the current situation of antibiotic resistance. In this review, we examine the current driving factors leading to the crisis, impact of critical superbugs in three regions, and identify novel mechanisms of antibiotic resistance. It is crucial to monitor the phenotypic characteristics of drug-resistant pathogens and describe the mechanisms involved in preventing the emergence of cross-resistance to novel antimicrobials. Additionally, maintaining an active pipeline of new antibiotics is essential for fighting against diverse antibiotic-resistant pathogens. Developing antibacterial agents with novel mechanisms of action is a promising way to combat increasing antibiotic-resistant pathogens.

Exploring the Potential of Bee-Derived Antioxidants for Maintaining Oral Hygiene and Dental Health: A Comprehensive Review

Honey bee products comprise various compounds, including honey, propolis, royal jelly, bee pollen, bee wax and bee venom, which have long been recognized for their pharmacological and health-promoting benefits. Scientists have discovered that periodontal disorders stem from dental biofilm, an inflammatory response to bacterial overgrowth produced by dysbiosis in the oral microbiome. The bee products have been investigated for their role in prevention of oral diseases, which are attributed to a myriad of biologically active compounds including flavonoids (pinocembrin, catechin, caffeic acid phenethyl ester (CAPE) and galangin), phenolic acids (hydroxybenzoic acid, hydroxycinnamic acid, p-coumaric, ellagic, caffeic and ferulic acids) and terpenoids. This review aims to update the current understanding of role of selected bee products, namely, honey, propolis and royal jelly, in preventing oral diseases as well as their potential biological activities and mechanism of action in relation to oral health have been discussed. Furthermore, the safety of incorporation of bee products is also critically discussed. To summarize, bee products could potentially serve as a therapy option for people suffering from a variety of oral disorders.

A Novel Generation of Tailored Antimicrobial Drugs Based on Recombinant Multidomain Proteins

Antibiotic resistance has exponentially increased during the last years. It is necessary to develop new antimicrobial drugs to prevent and treat infectious diseases caused by multidrug- or extensively-drug resistant (MDR/XDR)-bacteria. Host Defense Peptides (HDPs) have a versatile role, acting as antimicrobial peptides and regulators of several innate immunity functions. The results shown by previous studies using synthetic HDPs are only the tip of the iceberg, since the synergistic potential of HDPs and their production as recombinant proteins are fields practically unexplored. The present study aims to move a step forward through the development of a new generation of tailored antimicrobials, using a rational design of recombinant multidomain proteins based on HDPs. This strategy is based on a two-phase process, starting with the construction of the first generation molecules using single HDPs and further selecting those HDPs with higher bactericidal efficiencies to be combined in the second generation of broad-spectrum antimicrobials. As a proof of concept, we have designed three new antimicrobials, named D5L37βD3, D5L37D5L37 and D5LAL37βD3. After an in-depth exploration, we found D5L37D5L37 to be the most promising one, since it was equally effective against four relevant pathogens in healthcare-associated infections, such as methicillin-susceptible (MSSA) and methicillin-resistant (MRSA) Staphylococcus aureus, methicillin-resistant Staphylococcus epidermidis (MRSE) and MDR Pseudomonas aeruginosa, being MRSA, MRSE and P. aeruginosa MDR strains. The low MIC values and versatile activity against planktonic and biofilm forms reinforce the use of this platform to isolate and produce unlimited HDP combinations as new antimicrobial drugs by effective means.

Colistin- and amikacin-loaded lipid-based drug delivery systems for resistant gram-negative lung and wound bacterial infections

Antimicrobial resistance (AMR) is a global health issue, which needs to be tackled without further delay. The World Health Organization(WHO) has classified three gram-negative bacteria, Pseudomonas aeruginosa, Klebsiella pneumonia and Acinetobacter baumannii, as the principal responsible for AMR, mainly causing difficult to treat nosocomial lung and wound infections. In this regard, the need for colistin and amikacin, the re-emerged antibiotics of choice for resistant gram-negative infections, will be examined as well as their associated toxicity. Thus, current but ineffective clinical strategies designed to prevent toxicity related to colistin and amikacin will be reported, highlighting the importance of lipid-based drug delivery systems (LBDDSs), such as liposomes, solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs), as efficient delivery strategies for reducing antibiotic toxicity. This review reveals that colistin- and amikacin-NLCs are promising carriers with greater potential than liposomes and SLNs to safely tackle AMR, especially for lung and wound infections.

TriNet: A tri-fusion neural network for the prediction of anticancer and antimicrobial peptides

The accurate identification of anticancer peptides (ACPs) and antimicrobial peptides (AMPs) remains a computational challenge. We propose a tri-fusion neural network termed TriNet for the accurate prediction of both ACPs and AMPs. The framework first defines three kinds of features to capture the peptide information contained in serial fingerprints, sequence evolutions, and physicochemical properties, which are then fed into three parallel modules: a convolutional neural network module enhanced by channel attention, a bidirectional long short-term memory module, and an encoder module for training and final classification. To achieve a better training effect, TriNet is trained via a training approach using iterative interactions between the samples in the training and validation datasets. TriNet is tested on multiple challenging ACP and AMP datasets and exhibits significant improvements over various state-of-the-art methods. The web server and source code of TriNet are respectively available at http://liulab.top/TriNet/server and https://github.com/wanyunzh/TriNet.

Sustained increases in antibiotic prescriptions per primary care consultation for upper respiratory tract infections in England during the COVID-19 pandemic

Background

The responsible use of existing antimicrobials is essential in reducing the threat posed by antimicrobial resistance (AMR). With the introduction of restrictions during the COVID-19 pandemic, a substantial reduction in face-to-face appointments in general practice was observed. To understand if this shift in healthcare provision has impacted on prescribing practices, we investigated antibiotic prescribing for upper respiratory tract infections (URTI) consultations.

Methods

We conducted an interrupted time-series analysis using patient-level primary care data to assess the impact of the COVID-19 pandemic on consultations and antibiotic prescribing for URTI in England.

Results

We estimated an increase of 105.7 antibiotic items per 1000 URTI consultations (95% CI: 65.6-145.8; P < 0.001) after national lockdown measures in March 2020, with increases mostly sustained to May 2022.

Conclusions

Overuse of antibiotics is known to be a driver of resistance and it is essential that efforts to reduce inappropriate prescribing continue subsequent to the COVID-19 pandemic. Further work should examine drivers of increased antibiotic prescribing for URTI to inform the development of targeted antibiotic stewardship interventions.

Systems Biology: New Insight into Antibiotic Resistance

Over the past few decades, antimicrobial resistance (AMR) has emerged as an important threat to public health, resulting from the global propagation of multidrug-resistant strains of various bacterial species. Knowledge of the intrinsic factors leading to this resistance is necessary to overcome these new strains. This has contributed to the increased use of omics technologies and their extrapolation to the system level. Understanding the mechanisms involved in antimicrobial resistance acquired by microorganisms at the system level is essential to obtain answers and explore options to combat this resistance. Therefore, the use of robust whole-genome sequencing approaches and other omics techniques such as transcriptomics, proteomics, and metabolomics provide fundamental insights into the physiology of antimicrobial resistance. To improve the efficiency of data obtained through omics approaches, and thus gain a predictive understanding of bacterial responses to antibiotics, the integration of mathematical models with genome-scale metabolic models (GEMs) is essential. In this context, here we outline recent efforts that have demonstrated that the use of omics technology and systems biology, as quantitative and robust hypothesis-generating frameworks, can improve the understanding of antibiotic resistance, and it is hoped that this emerging field can provide support for these new efforts.

Clinical Implications of Helicobacter pylori Antibiotic Resistance in Italy: A Review of the Literature

Helicobacter pylori (H. pylori) resistance to antibiotics has increased worldwide in recent decades, especially to clarithromycin. As a result, the World Health Organization (WHO) identified clarithromycin-resistant H. pylori as a "high priority" pathogen in 2017. As international guidelines recommend empirical therapy as first-line treatment, it is crucial to know local resistance rates and history of antibiotic use to determine the most appropriate first-line antibiotic treatment. Italy is one of the European countries with the highest prevalence of H. pylori infection and the highest percentage of antibiotic-resistant H. pylori. The aim of this review is to summarize all data on H. pylori antibiotic resistance in Italy in order to quantify the current rate and determine the most effective therapeutic approach. The study confirms an elevated level of resistance to clarithromycin, metronidazole, and levofloxacin in Italy. In addition, our results show a satisfactory eradication rate for a bismuth-based regimen when used as first- or second-line treatment. Naive patients are also successfully treated with clarithromycin-based quadruple therapies. Considering the good results of bismuth-based therapy as recovery therapy, this argues for the potential use of clarithromycin quadruple therapy as a first-line treatment.

The implications of Ortho-, Meta- and Para- Directors on the In-Vitro Photodynamic Antimicrobial Chemotherapy Activity of Cationic Pyridyl-dihydrothiazole Phthalocyanines

Cationic Zn phthalocyanine complexes derived by alkylation reaction of tetra-(pyridinyloxy) phthalocyanines at the ortho, meta, and para positions to form Zn (II) Tetrakis 3-(4-(2-pyridin-1-ium-1-yl) butyl)-2-mercapto-4,5-dihydrothiazol-3-ium phthalocyanine (2), Zn (II) Tetrakis 3-(4-(3-pyridin-1-ium-1-yl) butyl)-2-mercapto-4,5-dihydrothiazol-3-ium phthalocyanine (4) and Zn (II) Tetrakis 3-(4-(4-pyridin-1-ium-1-yl) butyl)-2-mercapto-4,5-dihydrothiazol-3-ium phthalocyanine (6). The photophysicochemical behaviours of the Pc complexes are assessed. The meta and para-substituted complexes demonstrate high singlet oxygen quantum yields. The cationic Pcs demonstrate good planktonic antibacterial activity towards Staphylococcus aureus and Escherichia coli with the highest log reduction values of 9.29 and 8.55, respectively. The cationic complexes also demonstrate a significant decrease in the viability of in vitro biofilms after photo-antimicrobial chemotherapy at 100 µM for both Staphylococcus aureus and Escherichia coli biofilms.

Occurrence and genetic characteristics of multidrug-resistant Escherichia coli isolates co-harboring antimicrobial resistance genes and metal tolerance genes in aquatic ecosystems

Multidrug-resistant (MDR) Escherichia coli isolates (n = 50) were recovered from aquatic ecosystems, which presented high counts of E. coli and metal values within the recommended range. These isolates showed different multidrug resistance profiles, highlighting the resistance to extended-spectrum cephalosporins, polymyxins, and fluoroquinolones. Several antimicrobial resistance genes (ARGs) were found, spotlighting the presence of at least one β-lactamase-encoding gene in each E. coli isolate. Substitutions in the quinolone resistance-determining regions and the two-component systems involving PhoP/PhoQ and PmrA/PmrB were also found. The metal tolerance gene rcnA (nickel and cobalt efflux pump) was the most prevalent. In this regard, 94% of E. coli isolates presented the co-occurrence of at least one ARG and metal tolerance gene. Furthermore, virulence genes and genetic diversity were found among MDR E. coli isolates. The emergence of potentially pathogenic isolates exhibiting multidrug resistance and metal tolerance emerged as a global health problem at the human-animal-environment interface.

Air Ambulance: Antimicrobial Power of Bacterial Volatiles

We are currently facing an antimicrobial resistance crisis, which means that a lot of bacterial pathogens have developed resistance to common antibiotics. Hence, novel and innovative solutions are urgently needed to combat resistant human pathogens. A new source of antimicrobial compounds could be bacterial volatiles. Volatiles are ubiquitous produced, chemically divers and playing essential roles in intra- and interspecies interactions like communication and antimicrobial defense. In the last years, an increasing number of studies showed bioactivities of bacterial volatiles, including antibacterial, antifungal and anti-oomycete activities, indicating bacterial volatiles as an exciting source for novel antimicrobial compounds. In this review we introduce the chemical diversity of bacterial volatiles, their antimicrobial activities and methods for testing this activity. Concluding, we discuss the possibility of using antimicrobial volatiles to antagonize the antimicrobial resistance crisis.

Antimicrobial peptides, conventional antibiotics, and their synergistic utility for the treatment of drug-resistant infections

Antimicrobial peptides (AMPs), also known as host defense peptides (HDPs), are important effector immune defense molecules in multicellular organisms. AMPs exert their antimicrobial activities through several mechanisms; thus far, induction of drug resistance through AMPs has been regarded as unlikely. Therefore, they have great potential as new generation antimicrobial agents. To date, more than 30 AMP-related drugs are in the clinical trial phase. In recent years, studies show that some AMPs and conventional antibiotics have synergistic effects. The combined use of AMPs and antibiotics can kill drug-resistant pathogens, prevent drug resistance, and significantly improve the therapeutic effects of antibiotics. In this review, we discuss the progress in synergistic studies on AMPs and conventional antibiotics. An overview of the current understanding of the functional scope of AMPs, ongoing clinical trials, and challenges in the development processes are also presented.

Antimicrobial stewardship for surgical antibiotic prophylaxis and surgical site infections: a systematic review

Background Surgical site infections account for 14-17% of all healthcare-associated infections. Antimicrobial stewardship (AMS) are complementary strategies developed to optimize the use of antimicrobials. Aim to evaluate the effectiveness of AMS in promoting adherence to surgical antibiotic prophylaxis protocols in hospitalized patients, reducing surgical site infection rate and cost-benefit ratio. Method This systematic review of randomized clinical trials, non-randomized clinical trials and before and after studies was performed using Pubmed, Cochrane, Web of Science, Scopus, Embase, Google Scholar and ClinicalTrials.gov, in addition to reference lists of included studies. The risk of bias of studies was measured by the ROBINS-I checklist and the quality of the evidence synthesis by GRADE. Results Fourteen before and after design studies were included. In 85.7% of the studies, AMS was effective in increasing adherence to surgical antibiotic prophylaxis protocols and in 28.5%, there was reduction in surgical site infection rate. Three studies evaluated cost-benefit ratio and found a favorable impact. Eight (57%) studies were at risk of moderate bias and six had severe bias. The evaluation of the synthesis of evidence showed quality ranging from low to very low. Conclusion AMS, such as audit, feedback, education, implementation of a protocol, and a computer-assisted decision support methodology, appear to be effective in promoting adherence to surgical antibiotic prophylaxis protocols, reducing surgical site infection rate with a positive economic impact. However, more studies, particularly randomized clinical trials, are needed to improve the level of evidence of available information on AMS in order to favor decision-making.

Insights into the epidemiology of community-associated methicillin-resistant Staphylococcus aureus in special populations and at the community-healthcare interface

The current epidemic proportions of infections caused by Staphylococcus aureus strains and especially by methicillin-resistant S. aureus (MRSA) are one of today's many threats to global public health, particularly in underdeveloped countries where significant gaps on the subject exist. The rapid spread and diversification of pandemic clones that exhibit remarkably increasing virulence and antimicrobial resistance pose a risk to the effective prevention and treatment of a wide range of infections. Undoubtedly, the remarkable versatility involving the pathogenesis and resistance of these bacteria is perpetuated through geographic and temporal factors inherent to clonal evolution and is reflected in the dramatic epidemiological changes of MRSA which, after decades prevailing in healthcare settings, have emerged in the community. Denominated community-associated [CA]-MRSA, these strains are particularly prevalent in some population groups, facilitating the spread of successful clones that are potentially capable of triggering severe community-acquired infections. Therefore, a broad approach to local epidemiological aspects in less studied regions, but nonetheless at latent risk of endemic spread that may reach global proportions, is necessary. In Brazil, despite limited molecular epidemiology data, CA-MRSA strains predominantly characterized as SCCmec IV, often classified as CC30-ST30, CC5-ST5 and CC8-ST8, seem to be spreading across different population groups in different regions of the country. Another important fact addressed in this review is the identification of the ST398-MRSA-IV/V clone and methicillin-susceptible S. aureus (MSSA) in healthy individuals from the community. Although susceptible to methicillin, the ST398 clone is associated with severe infections in humans and animals, denominated livestock-associated MRSA. It is therefore important to encourage assertive actions by all government sectors and by society, with a reassessment of current public health measures in light of the new perspectives arising from the scientific and epidemiological data on MRSA.

Antimicrobial peptidomes of Bothrops atrox and Bothrops jararacussu snake venoms

The worrisome emergence of pathogens resistant to conventional drugs has stimulated the search for new classes of antimicrobial and antiparasitic agents from natural sources. Antimicrobial peptides (AMPs), acting through mechanisms that do not rely on the interaction with a specific receptor, provide new possibilities for the development of drugs against resistant organisms. This study sought to purify and proteomically characterize the antimicrobial and antiparasitic peptidomes of B. atrox and B. jararacussu snake venoms against Gram-positive (Staphylococcus aureus, Methicillin-resistant Staphylococcus aureus-MRSA), Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae) bacteria, and the protozoan parasites Leishmania amazonensis and Plasmodium falciparum (clone W2, resistant to chloroquine). To this end, B. atrox and B. jararacussu venom peptides were purified by combination of 3 kDa cut-off Amicon^® ultracentrifugal filters and reverse-phase high-performance liquid chromatography, and then identified by electrospray-ionization Ion-Trap/Time-of-Flight mass spectrometry. Fourteen distinct peptides, with masses ranging from 443.17 to 1383.73 Da and primary structure between 3 and 13 amino acid residues, were sequenced. Among them, 13 contained unique sequences, including 4 novel bradykinin-potentiating-like peptides (BPPs), and a snake venom metalloproteinase tripeptide inhibitor (SVMPi). Although commonly found in Viperidae venoms, except for Bax-12, the BPPs and SVMPi here reported had not been described in B. atrox and B. jararacussu venoms. Among the novel peptides, some exhibited bactericidal activity towards P. aeruginosa and S. aureus, had low hemolytic effect, and were devoid of antiparasitic activity. The identified novel antimicrobial peptides may be relevant in the development of new drugs for the management of multidrug-resistant Gram-negative and Gram-positive bacteria.

Identification of bioactive peptides released from in vitro gastrointestinal digestion of yam proteins (Dioscorea cayennensis)

Bioactive peptides have been broadly studied for their contribution to human health. This study aimed to identify bioactive peptides generated by in vitro gastrointestinal digestion of yam proteins. Yam protein concentrate (YPC) was submitted to simulated digestion. Gastric phase hydrolysate (GPH) and total gastrointestinal phase hydrolysate (GIPH) had their peptides identified by nanoLC-ESI-MS/MS. Peptide sequences were subjected to a database-driven (BIOPEP) bioactivity search. In vitro tests included: Antioxidant activity, DNA damage protection, ACE-inhibitory activity and antibacterial activity against the bacteria Escherichia coli, Salmonella sp. and Lysteria monocytogenes. Simulated digestion generated small peptides (mostly MW < 3500 Da), several of them with potential bioactive sequences predicted in silico. In both GPH and GIPH biological activities were detected, although GIPH displayed stronger DNA damage protection and antibacterial activity against Escherichia coli. The digestion of yam proteins releases promising biologically active peptides which can contribute to the prevention of bacterial infection and chronic degenerative diseases, with beneficial effects to human health.

Antibiotic and Metal Resistance in Escherichia coli Isolated from Pig Slaughterhouses in the United Kingdom

Antimicrobial resistance is currently an important concern, but there are few data on the co-presence of metal and antibiotic resistance in potentially pathogenic Escherichia coli entering the food chain from pork, which may threaten human health. We have examined the phenotypic and genotypic resistances to 18 antibiotics and 3 metals (mercury, silver, and copper) of E. coli from pig slaughterhouses in the United Kingdom. The results showed resistances to oxytetracycline, streptomycin, sulphonamide, ampicillin, chloramphenicol, trimethoprim–sulfamethoxazole, ceftiofur, amoxicillin–clavulanic acid, aztreonam, and nitrofurantoin. The top three resistances were oxytetracycline (64%), streptomycin (28%), and sulphonamide (16%). Two strains were resistant to six kinds of antibiotics. Three carried the bla_TEM gene. Fifteen strains (18.75%) were resistant to 25 µg/mL mercury and five (6.25%) of these to 50 µg/mL; merA and merC genes were detected in 14 strains. Thirty-five strains (43.75%) showed resistance to silver, with 19 possessing silA, silB, and silE genes. Fifty-five strains (68.75%) were resistant to 8 mM copper or above. Seven contained the pcoE gene. Some strains were multi-resistant to antibiotics, silver, and copper. The results in this study, based on strains isolated between 2007 and 2010, will aid understanding about the effects of strategies to reduce resistance and mechanisms of antimicrobial resistance (AMR).

Cysteine-rich antimicrobial peptides from plants: The future of antimicrobial therapy

There has been a spurt in the spread of microbial resistance to antibiotics due to indiscriminate use of antimicrobial agents in human medicine, agriculture, and animal husbandry. It has been realized that conventional antibiotic therapy would be less effective in the coming decades and more emphasis should be given for the development of novel antiinfective therapies. Cysteine rich peptides (CRPs) are broad-spectrum antimicrobial agents that modulate the innate immune system of different life forms such as bacteria, protozoans, fungi, plants, insects, and animals. These are also expressed in several plant tissues in response to invasion by pathogens, and play a crucial role in the regulation of plant growth and development. The present work explores the importance of CRPs as potent antimicrobial agents, which can supplement and/or replace the conventional antibiotics. Different plant parts of diverse plant species showed the presence of antimicrobial peptides (AMPs), which had significant structural and functional diversity. The plant-derived AMPs exhibited potent activity toward a range of plant and animal pathogens, protozoans, insects, and even against cancer cells. The cysteine-rich AMPs have opened new avenues for the use of plants as biofactories for the production of antimicrobials and can be considered as promising antimicrobial drugs in biotherapeutics.

Topoisomerase Inhibitors Addressing Fluoroquinolone Resistance in Gram-Negative Bacteria

Since their discovery over 5 decades ago, quinolone antibiotics have found enormous success as broad spectrum agents that exert their activity through dual inhibition of bacterial DNA gyrase and topoisomerase IV. Increasing rates of resistance, driven largely by target-based mutations in the GyrA/ParC quinolone resistance determining region, have eroded the utility and threaten the future use of this vital class of antibiotics. Herein we describe the discovery and optimization of a series of 4-(aminomethyl)quinolin-2(1H)-ones, exemplified by 34, that inhibit bacterial DNA gyrase and topoisomerase IV and display potent activity against ciprofloxacin-resistant Gram-negative pathogens. X-ray crystallography reveals that 34 occupies the classical quinolone binding site in the topoisomerase IV-DNA cleavage complex but does not form significant contacts with residues in the quinolone resistance determining region.

β-lactam resistance in bacteria associated with subclinical mastitis in goats in Thika Subcounty, Kenya

AIM

This study determined the resistance pattern to β-lactam antibiotics of bacteria isolated from goats with subclinical mastitis in Thika subcounty, Kenya. We also administered a questionnaire to assess the risk factors associated with the occurrence of resistance to commonly used antibiotics.

MATERIALS AND METHODS

We collected milk samples from 110 lactating dairy goats in Thika subcounty to screen for subclinical mastitis using the California mastitis test. Bacterial isolation and identification were performed according to colony morphology, the hemolytic pattern on sheep blood agar, lactose fermentation on MacConkey plates, Gram staining, and standard biochemical tests. The antibiotic susceptibility of the isolates was determined by the agar disk diffusion method using penicillin G, cephalexin, cefoxitin, and cefotaxime antibiotic disks. The double-disk synergy test using amoxicillin-clavulanic acid was employed as a confirmatory test for extended-spectrum β-lactamase (ESBL) production. Fisher's exact test was used to determine the risk factors associated with the occurrence of antibiotic resistance (p≤0.05 was considered significant).

RESULTS

Of the 110 dairy goats sampled, 72.7% (80) were positive for subclinical mastitis. Isolation and identification of the bacteria from the positive samples yielded 149 bacteria isolates, including Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter spp., Yersinia spp., coagulase-negative staphylococci, and Escherichia coli. A high percentage (76.5%, 114/149) of the bacterial isolates was resistant to at least one of the tested antibiotics. At least 56/106 isolates (52.8%) showing cross-resistance to the β-lactam antibiotics were resistant to all four of the tested antibiotics, while only one isolate was resistant to three antibiotics (penicillin G, cephalexin, and cefoxitin). The double-disk synergy test confirmed that none of the isolates possessed ESBLs. Pre- and post-milking practices (p=0.0336) were found to be significantly associated with the occurrence of antibiotic resistance.

CONCLUSION

A large proportion of the goats in our study cohort were infected with β-lactam-resistant bacteria associated with subclinical mastitis. Because the identified bacteria are of zoonotic importance, further studies should be undertaken to determine the transmission dynamics between humans and livestock and to identify novel intervention strategies.

Effect of drug dose and timing of treatment on the emergence of drug resistance in vivo in a malaria model

BACKGROUND AND OBJECTIVES

There is a significant interest in identifying clinically effective drug treatment regimens that minimize the de novo evolution of antimicrobial resistance in pathogen populations. However, in vivo studies that vary treatment regimens and directly measure drug resistance evolution are rare. Here, we experimentally investigate the role of drug dose and treatment timing on resistance evolution in an animal model.

METHODOLOGY

In a series of experiments, we measured the emergence of atovaquone-resistant mutants of Plasmodium chabaudi in laboratory mice, as a function of dose or timing of treatment (day post-infection) with the antimalarial drug atovaquone.

RESULTS

The likelihood of high-level resistance emergence increased with atovaquone dose. When varying the timing of treatment, treating either very early or late in infection reduced the risk of resistance. When we varied starting inoculum, resistance was more likely at intermediate inoculum sizes, which correlated with the largest population sizes at time of treatment.

CONCLUSIONS AND IMPLICATIONS

(i) Higher doses do not always minimize resistance emergence and can promote the emergence of high-level resistance. (ii) Altering treatment timing affects the risk of resistance emergence, likely due to the size of the population at the time of treatment, although we did not test the effect of immunity whose influence may have been important in the case of late treatment. (iii) Finding the 'right' dose and 'right' time to maximize clinical gains and limit resistance emergence can vary depending on biological context and was non-trivial even in our simplified experiments.

LAY SUMMARY

In a mouse model of malaria, higher drug doses led to increases in drug resistance. The timing of drug treatment also impacted resistance emergence, likely due to the size of the population at the time of treatment.

Association between the rate of third generation cephalosporin-resistant Escherichia coli and Klebsiella pneumoniae and antibiotic consumption based on 143 Chinese tertiary hospitals data in 2014

This study sought to discuss the correlation between the third-generation cephalosporins (3GC)-resistant Escherichia coli and Klebsiella pneumoniae and antibiotic consumption intensity from 143 Chinese tertiary hospitals in 2014. With a retrospective design, the correlation between antibiotic consumption and 3GC-resistant E. coli and K. pneumoniae were performed. 3GC-resistant E. coli was significantly correlated with the consumption of all antibiotics (r = 0.252, p < 0.01), β-Lactams antibiotics (r = 0.313, p < 0.01), β-Lactams excluding combinations with β-lactamase inhibitors (r = 0.365, p < 0.01), cephalosporin (r = 0.398, p < 0.01), cephalosporins excluding combinations with β-lactamase inhibitors (r = 0.374, p < 0.01), 3GC (r = 0.321, p < 0.01), and 3GC excluding combinations with β-lactamase inhibitors (r = 0.343, p < 0.01). 3GC-resistant K. pneumoniae was significantly correlated with the consumption of all antibiotics (r = 0.200, p < 0.05), β-Lactams antibiotics (r = 0.232, p < 0.01), cephalosporin (r = 0.215, p < 0.05), 3GC (r = 0.383, p < 0.01), 3GC excluding combinations with β-lactamase inhibitors (r = 0.245, p < 0.01), and β-lactam-β-lactamase inhibitor combinations (r = 0.218, p < 0.05). There was a significant relationship between the antibiotic consumption and the rates of 3GC-resistant E. coli and K. pneumoniae. Clinicians should grasp the indication of antibiotics use to reduce the production of drug-resistant bacteria.

Combating Antibiotic Resistance through the Synergistic Effects of Mesoporous Silica-Based Hierarchical Nanocomposites

The enormous influence of bacterial resistance to antibiotics has led researchers toward the development of various advanced antibacterial modalities. In this vein, nanotechnology-based devices have garnered interest owing to their excellent morphological as well as physicochemical features, resulting in augmented therapeutic efficacy. Herein, to overcome the multidrug resistance (MDR) in bacteria, we demonstrate the fabrication of a versatile design based on the copper-doped mesoporous silica nanoparticles (Cu-MSNs). Indeed, the impregnated Cu species in the siliceous frameworks of MSNs establish pH-responsive coordination interactions with the guest molecules, tetracycline (TET), which not only enhance their loading efficiency but also assist in their release in the acidic environment precisely. Subsequently, the ultrasmall silver nanoparticles-stabilized polyethyleneimine (PEI-SNP) layer is coated over Cu-MSNs. The released silver ions from the surface-deposited SNPs are capable of sensitizing the resistant strains through establishing the interactions with the biomembranes, and facilitate the generation of toxic free radicals, damaging the bacterial components. In addition to SNPs, Cu species impregnated in MSN frameworks synergistically act through the production of free radicals by participating in the Fenton-like reaction. Various physical characterization techniques for confirming the synthesis and successful surface modification of functional nanomaterials, as well as different antibacterial tests performed against MDR bacterial strains, are highly commendable. Remarkably, this versatile formulation has shown no significant toxic effects on normal mammalian fibroblast cells accounting for its high biocompatibility. Together, these biocompatible MSN-based trio-hybrids with synergistic efficacy and pH-responsive delivery of antibiotics potentially allow for efficient combat against MDR in bacteria.

Photodynamically Active Electrospun Fibers for Antibiotic-Free Infection Control

Antimicrobial biomaterials are critical to aid in the regeneration of oral soft tissue and prevent or treat localized bacterial infections. With the rising trend in antibiotic resistance, there is a pressing clinical need for new antimicrobial chemistries and biomaterial design approaches enabling on-demand activation of antibiotic-free antimicrobial functionality following an infection that are environment-friendly, flexible and commercially viable. This study explores the feasibility of integrating a bioresorbable electrospun polymer scaffold with localized antimicrobial photodynamic therapy (aPDT) capability. To enable aPDT, we encapsulated a photosensitizer (PS) in polyester fibers in the PS inert state, so that the antibacterial function would be activated on-demand via a visible light source. Fibrous scaffolds were successfully electrospun from FDA-approved polyesters, either poly(ε-caprolactone (PCL) or poly[(rac-lactide)-co-glycolide] (PLGA), with encapsulated PS (either methylene blue (MB) or erythrosin B (ER)). These were prepared and characterized with regards to their loading efficiency (UV-vis spectroscopy), microarchitecture (SEM, porometry, and BET (Brunauer-Emmett-Teller) analysis), tensile properties, hydrolytic behavior (contact angle, dye release capability, degradability), and aPDT effect. The electrospun fibers achieved an ∼100 wt % loading efficiency of PS, which significantly increased their tensile modulus and reduced their average fiber diameter and pore size with respect to PS-free controls. In vitro, PS release varied between a burst release profile to limited release within 100 h, depending on the selected scaffold formulation, while PLGA scaffolds displayed significant macroscopic shrinkage and fiber merging, following incubation in phosphate buffered saline solution. Exposure of PS-encapsulated PCL fibers to visible light successfully led to at least a 1 log reduction in Escherichia coli viability after 60 min of light exposure, whereas PS-free electrospun controls did not inactive microbes. This study successfully demonstrates the significant potential of PS-encapsulated electrospun fibers as photodynamically active biomaterial for antibiotic-free infection control.

High admission prevalence of fluoroquinolone resistance in third-generation cephalosporin-resistant Enterobacteriaceae in German university hospitals

Objectives

Fluoroquinolone resistance (FQR) in third-generation cephalosporin-resistant Enterobacteriaceae (3GCRE) presents serious limitations to antibiotic therapy. The aim of this study was to investigate whether the FQR proportion among 3GCRE differs between community-acquired (CA) and hospital-acquired (HA) isolates.

Methods

In a prospective observational study covering 2014 and 2015, we monitored the occurrence of 3GCRE in adult hospitalized patients in six German university hospitals. 3GCRE clinical isolates were subdivided into CA and HA. Multivariable analysis identified factors associated with in vitro non-susceptibility to ciprofloxacin.

Results

The dataset included 5721 3GCRE isolates of which 52.9% were HA and 52.7% exhibited FQR. Interestingly, the FQR proportion was higher in CA 3GCRE than in HA 3GCRE (overall, 60.1% versus 46.2%, respectively, P < 0.001). Multivariable analysis adjusting for age confirmed community acquisition as a risk factor for FQR [adjusted rate ratio (aRR) 1.33, 95% CI 1.17-1.53]. Escherichia coli and Klebsiella spp. were associated with a much higher FQR proportion than other Enterobacteriaceae species (aRR 8.14, 95% CI 6.86-9.65 and aRR 7.62 with 95% CI 6.74-8.61, respectively).

Conclusions

The high FQR proportion observed among CA 3GCRE, particularly in E. coli and Klebsiella spp., indicates that selection pressure in the outpatient setting needs to be addressed with antibiotic stewardship and other interventions in order to limit further spread of MDR.

Antibiotic resistance: a hospital-based multicenter study in Tabuk city, Kingdom of Saudi Arabia

Background: During the 21st century, antimicrobial resistance (AMR) has emerged as one of the greatest public health challenges worldwide. In the coming 20 years, health care systems may be unable to treat bacterial diseases efficiently due to this phenomenon.

Objective: To determine the level of knowledge regarding AMR among patients attending two hospitals in Tabuk city in northeast Kingdom of Saudi Arabia (KSA).

Materials and Methods: This cross-sectional study was conducted at King Salman Armed Forces Hospital and King Khalid Armed Forces Hospital in Tabuk city. The study participants were selected from different outpatient departments using a simple random sampling technique. Data collection was performed using a self-reported questionnaire. All of the questions were closed-ended to facilitate study participation and were translated into Arabic. The data were entered into SPSS version 22 for Windows, cleaned and managed before analysis.

Results: Our results showed that 26.85% of the respondents had knowledge regarding antibiotic resistance. Knowledge regarding the use of antibiotics for treating bacterial infection was good among participants (60%), but responses related to viral infection indicated confusion (23.06%), and misconceptions were observed. Several factors were significantly associated with knowledge regarding AMR among participants: 1) the use of antibiotics in the last year (OR: 2.102, CI: 0.654–6.754); 2) the discontinued use of antibiotics when feeling better (OR: 8.285, CI: 3.918–17.523); 3) giving antibiotics to friends or family members to treat the same illness ([False]: OR: 108.96, CI: 29.98–395.93) and 4) asking doctors to prescribe antibiotics that had been previously administered for the same symptoms (OR: 9.314, CI: 3.684–23.550).

Conclusion: Our results revealed a very high unawareness of AMR and its contributing factors among the study participants. Thus, health education and awareness are highly and urgently recommended to address AMR in the Tabuk area.

Antimicrobial coatings prepared from Dhvar-5-click-grafted chitosan powders

Antimicrobial peptides (AMP) are powerful components of the innate immune system, as they display wide activity spectrum and low tendency to induce pathogen resistance. Hence, the development of AMP-based coatings is a very promising strategy to prevent biomaterials-associated infections. This work aims to investigate if Dhvar-5-chitosan conjugates, previously synthesized by us via azide-alkyne "click" reaction, can be applied as antimicrobial coatings. Ultrathin coatings were prepared by spin coater after dissolving Dhvar-5-chitosan conjugate powder in aqueous acetic acid. Peptide orientation and exposure from the surface was confirmed by ellipsometry and contact angle measurements. Bactericidal activity was evaluated against Staphylococcus epidermidis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, the most prevalent pathogens in implant-associated infections. Results showed that Dhvar-5-chitosan coatings displayed bactericidal effect. Moreover, since Dhvar-5 has head-to-tail amphipathicity, it was clear that the bactericidal potency was dependent on which domain of the peptide (cationic or hydrophobic) was exposed. In this context, Dhvar-5 immobilized through its C-terminus (exposing its hydrophobic end) presented higher antimicrobial activity against Gram-positive bacteria and reduced adhesion of Gram-negative bacteria. This orientation-dependent antimicrobial activity was further corroborated by the anti-biofilm assay, as covalent immobilization of Dhvar-5 through its C-terminus provided anti-biofilm properties to the chitosan thin film. Immobilization of Dhvar-5 showed no cytotoxic effect against HFF-1 cells, as both metabolic activity and cell morphology were similar to control. In conclusion, Dhvar-5-chitosan coatings are promising antimicrobial surfaces without cytotoxic effects against human cells. STATEMENT OF SIGNIFICANCE: AMP-tethering onto ground biomaterial is still a poorly explored strategy in research. In this work, AMP-tethered ground chitosan is used to produce highly antibacterial ultrathin films. Powdered AMP-tethered chitosan appears as an alternative solution for antimicrobial devices production, as it is suitable for large scale production, being easier to handle for fabrication of different coatings and materials with antimicrobial properties and without inducing toxicity.

In Vitro Evaluation of Antimicrobial Activity and Cytotoxicity of Different Nanobiotics Targeting Multidrug Resistant and Biofilm Forming Staphylococci

Antibiotic-resistant and biofilm-forming bacteria have surprisingly increased over recent years. On the contrary, the rate of development of new antibiotics to treat these emerging superbugs is very slow. Therefore, the aim of this study was to prepare novel nanobiotic formulations to improve the antimicrobial activity of three antibiotics (linezolid, doxycycline, and clindamycin) against Staphylococci. Antibiotics were formulated as nanoemulsions and evaluated for their antimicrobial activities and cytotoxicities. Cytotoxicity of the conventional antibiotics and nanobiotics was analyzed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay on rat hepatocytes. Half-maximal inhibitory concentration (IC₅₀) was estimated from an experimentally derived dose-response curve for each concentration using GraphPad Prism software. Upon quantitative assessment of Staphylococcus biofilm formation, eighty-four isolates (66.14 %) were biofilm forming. Linezolid and doxycycline nanobiotics exhibited promising antibacterial activities. On the contrary, clindamycin nanobiotic exhibited poor antibacterial activity. Minimum biofilm inhibitory concentrations showed that 73.68 %, 45.6%, and 5.2% of isolates were sensitive to linezolid, doxycycline, and clindamycin nanobiotics, respectively. Results of this study revealed that antibiotics loaded in nanosystems had a higher antimicrobial activity and lower cytotoxicities as compared to those of conventional free antibiotics, indicating their potential therapeutic values.

Identification of small molecule compounds active against Staphylococcus aureus and Proteus mirabilis

Staphylococcus aureus is a human pathogen rapidly becoming a serious health problem due to ease of acquiring antibiotic resistance. To help identify potential new drug candidates effective against the pathogen, a small focused library was screened for inhibition of bacterial growth against several pathogens, including S. aureus. At least one of the compounds, Compound 10, was capable of blocking bacterial growth of S. aureus in a test tube with IC₅₀ = 140 ± 30 μM. Another inhibitor, Compound 7, was bacteriostatic against S. aureus with IC₅₀ ranging from 33 to 150 μM against 3 different strains. However, only Compound 7 was bactericidal against P. mirabilis as examined by electron microscopy. Human cell line toxicity studies suggested that both compounds had small effect on cell growth at 100 μM concentration as examined by MTT assay. Analysis of compounds' structures showed lack of similarity to any known antibiotics and bacteriostatics, potentially offering the inhibitors as an alternative to existing solutions in controlling bacterial infections for selected pathogens.

Antidepressant fluoxetine induces multiple antibiotics resistance in Escherichia coli via ROS-mediated mutagenesis

BACKGROUND

Antibiotic resistance poses a great threat to global public health. Overuse of antibiotics is generally considered as the major factor contributing to it. However, little is known about whether non-antibiotic drugs could play potential roles in the emergence of antibiotic resistance.

OBJECTIVE

We aimed to investigate whether antidepressant fluoxetine induces multiple antibiotic resistances and reveal underlying mechanisms.

METHODOLOGY

Escherichia coli K12 was exposed to different concentrations of fluoxetine (0, 0.5, 5, 50 and 100 mg/L) and the resistant strains were isolated by plating on antibiotic containing plates. Resistant strains were randomly selected to determine the increase of minimum inhibition concentration (MIC) of multiple antibiotics. Genome-wide DNA sequencing was performed on cells cultured in lysogeny broth (LB) without any fluoxetine or antibiotics exposure. RNA sequencing and proteomic profiling of isolated mutants grown in LB with 100 mg/L fluoxetine were analyzed to reveal the underlying mechanisms.

RESULTS

Exposure of Escherichia coli to fluoxetine at 5-100 mg/L after repeated subculture in LB for 30 days promoted its mutation frequency resulting in increased resistance against the antibiotics chloramphenicol, amoxicillin and tetracycline. This increase was up to 5.0 × 10⁷ fold in a dose-time pattern. Isolated mutants with resistance to one of these antibiotics also exhibited multiple resistances against fluoroquinolone, aminoglycoside, β-lactams, tetracycline and chloramphenicol. According to global transcriptional and proteomic analyses, the AcrAB-TolC pump together with the YadG/YadH transporter, a Tsx channel and the MdtEF-TolC pump have been triggered to export the antibiotics to the exterior of the cell. Whole-genome DNA analysis of the mutants further revealed that ROS-mediated mutagenesis (e.g., deletion, insertion, and substitution) of DNA-binding transcriptional regulators (e.g., marR, rob, sdiA, cytR and crp) to up-regulate the expression of efflux pumps, may further enhance the antibiotic efflux.

CONCLUSIONS

Our findings for the first time demonstrated that the exposure to antidepressant fluoxetine induces multiple antibiotic resistance in E. coli via the ROS-mediated mutagenesis.

Breast Pocket Irrigation with Antibiotic Solution at Implant Insertion: A Systematic Review and Meta-Analysis

BACKGROUND

Antibiotic irrigation is routinely used during implant insertion in augmentation mammoplasty procedures. However, the evidence for whether this reduces the incidence of infection or capsular contracture is unclear.

METHODS AND MATERIALS

Five databases were used to search for all randomized control trials, retrospective cohort and prospective cohort studies containing original data related to the primary outcomes being investigated in this study. The primary outcomes were the effects of antibiotic breast pocket irrigation on clinical infection and capsular contracture. The literature search was designed to combine three concepts: implant or tissue expander-based breast surgery, antibiotic irrigation and clinical infection or capsular contracture. Studies found were screened using specific eligibility criteria. Risk ratios (RR) and 95% confidence interval (CI) were calculated using pooled acquired data from all included studies.

RESULTS

The search identified 1256 citations. Three independent screeners identified seven studies that met the inclusion criteria with a pooled population of 4725. This included one prospective and six retrospective studies. A meta-analysis of pooled study data showed significant reductions in clinical infection (RR 0.52, 95% CI 0.33-0.81) and capsular contracture (RR 0.36, 95% CI 0.16-0.83) as a result of antibiotic irrigation.

CONCLUSION

The meta-analyses support the use of antibiotic irrigation of the breast pocket. However, the results of this study are limited by the large proportion of retrospective studies, the small number of studies included, the lack of randomized controlled trials and the heterogeneity of the antibiotic and control regimes used.

LEVEL OF EVIDENCE III

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Molecular characterization of a novel ovodefensin gene in chickens

Host defense peptides (HDPs) represent a large group of diverse small peptides that play important roles in host defense and disease resistance. In vertebrates, one of the main types of HDPs belong to defensins, which are less than 100 amino acid residues and characterized by a highly conserved motif of cysteine residues. Recently, a subfamily of defensins, namely ovodefensins (OvoDs), has been identified in birds and reptiles. However, both their family members and evolutionary relationships remain unclear. In the present study, we cloned and characterized a novel gene namely OvoDBβ in chickens. Our results showed that the full length of chicken OvoDBβ mRNA contains 344 bp nucleotides and encodes a 61-amino acid protein. We further revealed that the mRNA of OvoDBβ is abundant in the oviduct of laying hens but absent in many other tissues. Additionally, sequences comparison and analyses suggested that OvoDBβ is orthologous to the gene previously known as zebra finch OvoDB1, albeit it might exhibit specific structures. Furthermore, both OvoDBα and OvoDBβ were existent in the genome of each bird, implying that two types of OvoDBs sharing same cysteine motif have already emerged before the species divergence. More importantly, recombinant OvoDBβ mature peptide exerted antibacterial activity against Escherischia coli (CICC23657 strain) in vitro. These results collectively indicated that the putative sequence, namely chicken OvoDBβ, is a function gene with potential antimicrobial property. Discovery and function characterization of novel HDP genes may help us develop novel antimicrobial agents in the future.

Antimicrobial activity of Bulbothrix setschwanensis (Zahlbr.) Hale lichen by cell wall disruption of Staphylococcus aureus and Cryptococcus neoformans

In the present study, antimicrobial activity of a common Himalayan lichen viz. Bulbothrix setschwanensis (Zahlbr.) Hale extract in three common solvents (acetone, chloroform and methanol) was evaluated against six bacterial and seven fungal clinical strains. The acetone extract showed promising antimicrobial activity against S. aureus (1.56 mg/mL) and C. neoformans (6.25 mg/mL). Further, GC-MS analysis revealed 2,3-bis(2-methylpentanoyloxy)propyl 2-methylpentanoate and Ethyl 2-[(2R,3R,4aR,8aS)-3-hydroxy-2,3,4,4a,6,7,8,8a-octahydropyrano [3,2-b]pyran-2-yl]acetate as the predominant compounds. The combination of acetone extract with antibacterial drugs [kanamycin (KAN), rifampicin (RIF)] and antifungal drugs [amphotericin B (Amp B) and fluconazole (FLC)] showed lysis of S. aureus and C. neoformans at non-inhibitory concentration (FICI values were 0.31 for KAN, 0.18 for RIF, 0.37 for Amp B and 0.30 for FLC, respectively). Notably, the acetone extract confirmed cell wall damage of both S. aureus and C. neoformans cells and was clearly visualized under scanning electron microscopy (SEM), flow cytometry and confocal microscopy. Besides this, the three extracts also have less significant cytotoxic activity at MIC concentrations against mammalian cells (HEK-293 and HeLa). This study for the first time suggests that the chemical compounds present in the acetone extract of B. setschwanensis could be used against S. aureus and C. neoformans infections.

Antimicrobial natural product research: A review from a South African perspective for the years 2009-2016

ETHNOPHARMACOLOGICAL RELEVANCE

This review provides information on the antimicrobial research which has taken place on South African natural products for the last eight years (2009-2016). This important field is the backbone of all studies involving the use of medicinal plants against infectious diseases and hence can form the mainstay for future studies.

MATERIALS AND METHODS

All publications within the years 2009-2016 were considered. Exclusion criteria were studies not involving South African medicinal natural products and those publications where full articles could not be accessed. An overview of the most common experimental methods used and new advances in terms of antimicrobial investigations are provided. Disease categories selected for further investigation were skin and wounds, respiratory, gastrointestinal, sexually transmitted and ophthalmic infections amongst others. Alternate natural products and combinations studies were also included.

RESULTS

The minimum inhibitory concentration (MIC) was the most commonly used experimental method to determine antimicrobial activity. Staphylococcus aureus was the most commonly tested skin pathogen and Klebsiella pneumoniae was the most common pathogen implicated in respiratory disorders. Only 20% of gastrointestinal studies included commonly implicated pathogens such as Shigella flexneri and Campylobacter species.

CONCLUSION

Multidisciplinary studies have emerged as a strong support for antimicrobial investigations and show the importance of including toxicity when studying antimicrobial efficacy. Alternate approaches (for example biofilms and quorum sensing) at examining antimicrobial effects are encouraged. Studies on resistant strains require more insight and future recommendations should look at consistent dosing and investigations on compound interactions amongst others.

The study on interactions between levofloxacin and model proteins by using multi-spectroscopic and molecular docking methods

The interactions of levofloxacin (LEV) with lysozyme (LYZ), trypsin and bovine hemoglobin (BHb) were investigated, respectively, by using multi-spectral techniques and molecular docking in vitro. Fluorescence studies showed that LEV quenched LYZ/trypsin fluorescence in a combined quenching ways and BHb fluorescence in a static quenching with binding constants of .14, .51 and .20 × 10⁵ L mol^-1 at 298 K, respectively. The thermodynamic parameters demonstrated that hydrophobic forces, hydrogen bonds, and van der Waals forces played the major role in the binding process. The binding distances between LEV and the inner tryptophan residues of LYZ, trypsin, and BHb were calculated to be 4.04, 3.38, and 4.52 nm, respectively. Furthermore, the results of circular dichroism spectra (CD), UV-vis, and three-dimensional fluorescence spectra indicated that the secondary structures of LYZ, trypsin, and BHb were partially changed by LEV with the α-helix percentage of LYZ-LEV system increased while that of BHb-LEV system was decreased, the β-sheet percentage of trypsin-LEV system increased from 41.3 to 42.9%. UV-vis spectral results showed that the binding interactions could cause conformational and some micro-environmental changes of LYZ, trypsin, and BHb. The results of molecular docking revealed that in LYZ and trypsin systems, LEV bound to the active sites residues GLU 35 and ASP 52 of LYZ and trypsin at the active site SER 195, and in BHb system, LEV was located in the central cavity, which was consistent with the results of synchronous fluorescence experiment. Besides, LEV made the activity of LYZ decrease while the activity of trypsin increased.

GigA and GigB are Master Regulators of Antibiotic Resistance, Stress Responses, and Virulence in Acinetobacter baumannii

A critical component of bacterial pathogenesis is the ability of an invading organism to sense and adapt to the harsh environment imposed by the host's immune system. This is especially important for opportunistic pathogens, such as Acinetobacter baumannii, a nutritionally versatile environmental organism that has recently gained attention as a life-threatening human pathogen. The emergence of A. baumannii is closely linked to antibiotic resistance, and many contemporary isolates are multidrug resistant (MDR). Unlike many other MDR pathogens, the molecular mechanisms underlying A. baumannii pathogenesis remain largely unknown. We report here the characterization of two recently identified virulence determinants, GigA and GigB, which comprise a signal transduction pathway required for surviving environmental stresses, causing infection and antibiotic resistance. Through transcriptome analysis, we show that GigA and GigB coordinately regulate the expression of many genes and are required for generating an appropriate transcriptional response during antibiotic exposure. Genetic and biochemical data demonstrate a direct link between GigA and GigB and the nitrogen phosphotransferase system (PTS^Ntr), establishing a novel connection between a novel stress response module and a well-conserved metabolic-sensing pathway. Based on the results presented here, we propose that GigA and GigB are master regulators of a global stress response in A. baumannii, and coupling this pathway with the PTS^Ntr allows A. baumannii to integrate cellular metabolic status with external environmental cues.IMPORTANCE Opportunistic pathogens, including Acinetobacter baumannii, encounter many harsh environments during the infection cycle, including antibiotic exposure and the hostile environment within a host. While the development of antibiotic resistance in A. baumannii has been well studied, how this organism senses and responds to environmental cues remain largely unknown. Herein, we investigate two previously identified virulence determinants, GigA and GigB, and report that they are required for in vitro stress resistance, likely comprising upstream elements of a global stress response pathway. Additional experiments identify a connection between GigA/GigB and a widely conserved metabolic-sensing pathway, the nitrogen phosphotransferase system. We propose that coordination of these two pathways allows A. baumannii to respond appropriately to changing environmental conditions, including those encountered during infection.

Development and transmission of antimicrobial resistance among Gram-negative bacteria in animals and their public health impact

Gram-negative bacteria are known to cause severe infections in both humans and animals. Antimicrobial resistance (AMR) in Gram-negative bacteria is a major challenge in the treatment of clinical infections globally due to the propensity of these organisms to rapidly develop resistance against antimicrobials in use. In addition, Gram-negative bacteria possess highly efficient mechanisms through which the AMR can be disseminated between pathogenic and commensal bacteria of the same or different species. These unique traits of Gram-negative bacteria have resulted in evolution of Gram-negative bacterial strains demonstrating resistance to multiple classes of antimicrobials. The evergrowing resistance issue has not only resulted in limitation of treatment options but also led to increased treatment costs and mortality rates in humans and animals. With few or no new antimicrobials in production to combat severe life-threatening infections, AMR has been described as the one of the most severe, long-term threats to human health. Aside from overuse and misuse of antimicrobials in humans, another factor that has exacerbated the emergence of AMR in Gram-negative bacteria is the veterinary use of antimicrobials that belong to the same classes considered to be critically important for treating serious life-threatening infections in humans. Despite the fact that development of AMR dates back to before the introduction of antimicrobials, the recent surge in the resistance towards all available critically important antimicrobials has emerged as a major public health issue. This review thus focuses on discussing the development, transmission and public health impact of AMR in Gram-negative bacteria in animals.