General principles of antibiotic resistance in bacteria

Evaluation of bacterial uptake, antibacterial efficacy against Escherichia coli, and cytotoxic effects of moxifloxacin-loaded solid lipid nanoparticles

Moxifloxacin (MOX) is an important antibiotic commonly used in the treatment of recurrent Escherichia coli (E. coli) infections. The aim of this study was to investigate its antibacterial efficiency when used with solid lipid nanoparticles (SNLs) and nanostructured lipid carriers (NLCs) as delivery vehicles. For this purpose we designed two SLNs (SLN1 and SLN2) and two NLCs (NLC1 and NLC2) of different characteristics (particle size, size distribution, zeta potential, and encapsulation efficiency) and loaded them with MOX to determine its release, antibacterial activity against E. coli, and their cytotoxicity to the RAW 264.7 monocyte/macrophage-like cell line in vitro. With bacterial uptake of 57.29 %, SLN1 turned out to be significantly more effective than MOX given as standard solution, whereas SLN2, NLC1, and NLC2 formulations with respective bacterial uptakes of 50.74 %, 39.26 %, and 32.79 %, showed similar activity to standard MOX. Cytotoxicity testing did not reveal significant toxicity of nanoparticles, whether MOX-free or MOX-loaded, against RAW 264.7 cells. Our findings may show the way for a development of effective lipid carriers that reduce side effects and increase antibacterial treatment efficacy in view of the growing antibiotic resistance.

Synergistic Effects of Some Methoxyflavones Extracted from Rhizome of Kaempferia parviflora Combined with Gentamicin against Carbapenem-Resistant Strains of Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii

The present study aimed to investigate the antibacterial activity of ethanolic Kaempferia parviflora extracts and the combined effects of the plant's specific compounds with gentamicin against clinical strains of carbapenem-resistant Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. The minimal inhibitory concentrations (MIC) of gentamicin and Kaempferia parviflora extracts against the tested bacterial strains were determined by using broth microdilution. The combined effects of Kaempferia parviflora extract and gentamicin were investigated by using a checkerboard assay and expressed as a fractional inhibitory concentration index (FICI). Crude ethanolic extract of Kaempferia parviflora showed the lowest median values of MIC towards the tested isolates (n = 10) of these tested bacteria at doses of 64 µg/mL, compared to those of other Kaempferia extracts. Among the isolated compounds, only three compounds, namely 3,5,7-trimethoxyflavone, 3,5,7,3'4'-pentamethoxyflavone, and 5,7,4'-trimethoxyflavone, were identified by NMR structural analysis. According to their FICIs, the synergistic effects of gentamicin combined with 3,5,7,3'4'-pentamethoxyflavone were approximately 90%, 90%, and 80% of tested carbapenem-resistant Klebsiella pneumoniae (CRKP), Pseudomonas aeruginosa (CRPA), and Acinetobacter baumannii (CRAB), respectively. The present study concluded that 3,5,7,3'4'-pentamethoxyflavone extracted from Kaempferia parviflora potentiated the antibacterial action of gentamicin to combat bacterial resistance against the tested bacteria.

Antimicrobial resistance in fish and poultry: Public health implications for animal source food production in Nigeria, Egypt, and South Africa

Antimicrobial resistance (AMR) is a significant threat to global public health. Specifically, excessive usage of antimicrobials in food animal production is one significant reason for AMR development in humans. Therefore, it is essential to identify the trends of AMR in fish and poultry and develop better surveillance strategies for the future. Despite this imperative need, such information is not well documented, especially in Africa. This study used a systematic review to assess AMR trend, spatial distribution, and incidence in fish and poultry research in Nigeria, Egypt, and South Africa. A literature assessment was conducted for published studies on AMR between 1989 and 2021 using the Scopus and Web of Science databases. One hundred and seventy-three relevant articles were obtained from the database search. Egypt was the leading exponent of antimicrobial resistance research (43.35%, 75 studies), followed by Nigeria (39.31%, 68 studies), then South Africa (17.34%, 30 studies). The majority of the antimicrobial resistance studies were on poultry in Egypt (81%, 61 studies), Nigeria (87%, 59 studies), and South Africa (80%, 24 studies). Studies on fish were 17% (13 studies), 9% (6 studies), and 10% (3 studies) in Egypt, Nigeria, and South Africa, respectively. Antimicrobial resistance patterns showed multiple drug resistance and variations in resistant genes. AMR research focused on sulfamethoxazole groups, chloramphenicol, trimethoprim, tetracycline, erythromycin, and ampicillin. Most studies employed the disk diffusion method for antimicrobial susceptibility tests. Among the four mechanisms of AMR, limiting drug uptake was the most reported in this study (both in fish and poultry). The findings reveal public and environmental health threats and suggest that it would be useful to promote and advance AMR research, particularly for countries on the global hotspot for antimicrobial use.

Molecular mechanisms of multidrug resistance in clinically relevant enteropathogenic bacteria (Review)

Multidrug resistant (MDR) enteropathogenic bacteria are a growing problem within the clinical environment due to their acquired tolerance to a wide range of antibiotics, thus causing severe illnesses and a tremendous economic impact in the healthcare sector. Due to its difficult treatment, knowledge and understanding of the molecular mechanisms that confer this resistance are needed. The aim of the present review is to describe the mechanisms of antibiotic resistance from a genomic perspective observed in bacteria, including naturally acquired resistance. The present review also discusses common pharmacological and alternative treatments used in cases of infection caused by MDR bacteria, thus covering necessary information for the development of novel antimicrobials and adjuvant molecules inhibiting bacterial proliferation.

Link Between Antibiotic Persistence and Antibiotic Resistance in Bacterial Pathogens

Both, antibiotic persistence and antibiotic resistance characterize phenotypes of survival in which a bacterial cell becomes insensitive to one (or even) more antibiotic(s). However, the molecular basis for these two antibiotic-tolerant phenotypes is fundamentally different. Whereas antibiotic resistance is genetically determined and hence represents a rather stable phenotype, antibiotic persistence marks a transient physiological state triggered by various stress-inducing conditions that switches back to the original antibiotic sensitive state once the environmental situation improves. The molecular basics of antibiotic resistance are in principle well understood. This is not the case for antibiotic persistence. Under all culture conditions, there is a stochastically formed, subpopulation of persister cells in bacterial populations, the size of which depends on the culture conditions. The proportion of persisters in a bacterial population increases under different stress conditions, including treatment with bactericidal antibiotics (BCAs). Various models have been proposed to explain the formation of persistence in bacteria. We recently hypothesized that all physiological culture conditions leading to persistence converge in the inability of the bacteria to re-initiate a new round of DNA replication caused by an insufficient level of the initiator complex ATP-DnaA and hence by the lack of formation of a functional orisome. Here, we extend this hypothesis by proposing that in this persistence state the bacteria become more susceptible to mutation-based antibiotic resistance provided they are equipped with error-prone DNA repair functions. This is - in our opinion - in particular the case when such bacterial populations are exposed to BCAs.

Heteroaryl-Ethylenes as New Effective Agents for High Priority Gram-Positive and Gram-Negative Bacterial Clinical Isolates

The World Health Organization has identified antimicrobial resistance as a public health emergency and developed a global priority pathogens list of antibiotic-resistant bacteria that can be summarized in the acronym ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacterales species), reminding us of their ability to escape the effect of antibacterial drugs. We previously tested new heteroaryl-ethylene compounds in order to define their spectrum of activity and antibacterial capability. Now, we focus our attention on PB4, a compound with promising MIC and MBC values in all conditions tested. In the present study, we evaluate the activity of PB4 on selected samples of ESKAPE isolates from nosocomial infections: 14 S. aureus, 6 E. faecalis, 7 E. faecium, 12 E. coli and 14 A. baumannii. Furthermore, an ATCC control strain was selected for all species tested. The MIC tests were performed according to the standard method. The PB4 MIC values were within very low ranges regardless of bacterial species and resistance profiles: from 0.12 to 2 mg/L for S. aureus, E. faecalis, E. faecium and A. baumannii. For E. coli, the MIC values obtained were slightly higher (4–64 mg/L) but still promising. The PB4 heteroaryl-ethylenic compound was able to counteract the bacterial growth of both high-priority Gram-positive and Gram-negative clinical strains. Our study contributes to the search for new molecules that can fight bacterial infections, in particular those caused by MDR bacteria in hospitals. In the future, it would be interesting to evaluate the activity of PB4 in animal models to test for its toxicity.

Discovery of a Novel Antimicrobial Peptide, Temporin-PKE, from the Skin Secretion of Pelophylax kl. esculentus, and Evaluation of Its Structure-Activity Relationships

Bacterial resistance against antibiotics has led to increasing numbers of treatment failures, and AMPs are widely accepted as becoming potential alternatives due to their advantages. Temporin-PKE is a novel peptide extracted from the skin secretion of Pelophylax kl. esculentus and it displays a strong activity against Gram-positive bacteria, with an extreme cytotoxicity. Incorporating positively charged residues and introducing D-amino acids were the two main strategies adopted for the modifications. The transformation of the chirality of Ile could reduce haemolytic activity, and an analogue with appropriate D-isoforms could maintain antimicrobial activity and stability. The substitution of hydrophobic residues could bring about more potent and broad-spectrum antimicrobial activities. The analogues with Lys were less harmful to the normal cells and their stabilities remained at similarly high levels compared to temporin-PKE. The optimal number of charges was three, and the replacement on the polar face was a better choice. Temporin-PKE-3K exerted dually efficient functions includingstrong antimicrobial and anticancer activity. This analogue showed a reduced possibility for inducing resistance in MRSA and Klebsiella pneumoniae, a rather strong antimicrobial activity in vivo, and it exhibited the highest therapeutic index such that temporin-PKE-3K has the potential to be developed as a clinical drug.

Genetic Determinants of Surface Accessibility in Staphylococcus aureus

Bacterial cell walls represent one of the most prominent targets of antibacterial agents. These agents include natural products (e.g., vancomycin) and proteins stemming from the innate immune system (e.g., peptidoglycan-recognition proteins and lysostaphin). Among bacterial pathogens that infect humans, Staphylococcus aureus (S. aureus) continues to impose a tremendous healthcare burden across the globe. S. aureus has evolved countermeasures that can directly restrict the accessibility of innate immune proteins, effectively protecting itself from threats that target key cell well components. We recently described a novel assay that directly reports on the accessibility of molecules to the peptidoglycan layer within the bacterial cell wall of S. aureus. The assay relies on site-specific chemical remodeling of the peptidoglycan with a biorthogonal handle. Here, we disclose the application of our assay to a screen of a nonredundant transposon mutant library for susceptibility of the peptidoglycan layer with the goal of identifying genes that contribute to the control of cell surface accessibility. We discovered several genes that resulted in higher accessibility levels to the peptidoglycan layer and showed that these genes modulate sensitivity to lysostaphin. These results indicate that this assay platform can be leveraged to gain further insight into the biology of bacterial cell surfaces.

Nitric Oxide Release and Antibacterial Efficacy Analyses of S-Nitroso-N-Acetyl-Penicillamine Conjugated to Titanium Dioxide Nanoparticles

Therapeutic agents can be linked to nanoparticles to fortify their selectivity and targeted delivery while impeding systemic toxicity and efficacy loss. Titanium dioxide nanoparticles (TiNPs) owe their rise in biomedical sciences to their versatile applicability, although the lack of inherent antibacterial properties limits its application and necessitates the addition of bactericidal agents along with TiNPs. Structural modifications can improve TiNP's antibacterial impact. The antibacterial efficacy of nitric oxide (NO) against a broad spectrum of bacterial strains is well established. For the first time, S-nitroso-N-acetylpenicillamine (SNAP), an NO donor molecule, was covalently immobilized on TiNPs to form the NO-releasing TiNP-SNAP nanoparticles. The TiNPs were silanized with 3-aminopropyl triethoxysilane, and N-acetyl-d-penicillamine was grafted to them via an amide bond. The nitrosation was carried out by t-butyl nitrite to conjugate the NO-rich SNAP moiety to the surface. The total NO immobilization was measured to be 127.55 ± 4.68 nmol mg^-1 using the gold standard chemiluminescence NO analyzer. The NO payload can be released from the TiNP-SNAP under physiological conditions for up to 20 h. The TiNP-SNAP exhibited a concentration-dependent antimicrobial efficiency. At 5 mg mL^-1, more than 99.99 and 99.70% reduction in viable Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria, respectively, were observed. No significant cytotoxicity was observed against 3T3 mouse fibroblast cells at all the test concentrations determined by the CCK-8 assay. TiNP-SNAP is a promising and versatile nanoparticle that can significantly impact the usage of TiNPs in a wide variety of applications, such as biomaterial coatings, tissue engineering scaffolds, or wound dressings.

Geographic and Socioeconomic Influence on Knowledge and Practices Related to Antimicrobial Resistance among Smallholder Pig Farmers in Uganda

To mitigate the development of antimicrobial resistance (AMR), antibiotic use (ABU) in the livestock sector needs to be reduced. In low- and middle-income countries, regulations have shown to be less successful in reducing ABU. Here, a bottom-up approach can complement legal frameworks, which requires an understanding of the drivers for ABU. In this study, we investigated the influence of geographic and socioeconomic settings on determinants for ABU among pig farmers in Uganda. The data were collected through a questionnaire in two districts, Lira and Mukono, and comparative statistical analyses were performed. Farmers in Lira had less access to animal health services, applied disease prevention measures less and used antibiotics more. In Mukono, it was more common to consult a veterinarian in response to disease, while in Lira it was more common to consult an animal health worker. There was no difference in how many farmers followed treatment instructions from a veterinarian, but it was more common in Lira to follow instructions from pharmacies. The findings support the need for locally tailored AMR-reducing interventions to complement regulations. To accomplish this tailoring, systematic collection of knowledge of farm structures, farm practices and access to animal health services and veterinary drugs is necessary.

Suppression of Grape White Rot Caused by Coniella vitis Using the Potential Biocontrol Agent Bacillus velezensis GSBZ09

Grape white rot caused by Coniella vitis is prevalent in almost all grapevines worldwide and results in a yield loss of 10–20% annually. Bacillus velezensis is a reputable plant growth-promoting bacterial. Strain GSBZ09 was isolated from grapevine cv. Red Globe (Vitis vinifera) and identified as B. velezensis according to morphological, physiological, biochemical characteristics and a multilocus gene sequence analysis (MLSA) based on six housekeeping genes (16S rRNA, gyrB, rpoD, atpD, rho and pgk). B. velezensis GSBZ09 was screened for antifungal activity against C. vitis under in vitro and in vivo conditions. GSBZ09 presented broad spectrum antifungal activity and produced many extracellular enzymes that remarkably inhibited the mycelial growth and spore germination of C. vitis. Furthermore, GSBZ09 had a high capacity for indole-3-acetic acid (IAA) production, siderophore production, and mineral phosphate solubilization. Pot experiments showed that the application of GSBZ09 significantly decreased the disease index of the grape white rot, directly promoted the growth of grapes, and upregulated defense-related enzymes. Overall, the features of B. velezensis GSBZ09 make it a potential strain for application as a biological control agent against C. vitis.

Long-term spatiotemporal variation of antimicrobial resistance genes within the Serratia marcescens population and transmission of S. marcescens revealed by public whole-genome datasets

The development of antimicrobial resistance (AMR) is accelerated by the selective pressure exerted by the widespread use of antimicrobial drugs, posing an increasing danger to public health. However, long-term spatiotemporal variation in AMR genes in microorganisms, particularly in bacterial pathogens in response to antibiotic consumption, is not fully understood. Here, we used the NCBI RefSeq database to collect 478 whole-genome sequences for Serratia marcescens ranging from 1961 up to 2019, to document global long-term AMR trends in S. marcescens populations. In total, 100 AMR gene subtypes (16 AMR gene types) were detected in the genomes of S. marcescens populations. We identified 3 core resistance genes in S. marcescens genomes, and a high diversity of AMR genes was observed in S. marcescens genomes after corresponding antibiotics were discovered and introduced into clinical practice, suggesting the adaptation of S. marcescens populations to challenges with therapeutic antibiotics. Our findings indicate spatiotemporal variation of AMR genes in S. marcescens populations in relation to antibiotic consumption and suggest the potential transmission of S. marcescens isolates harboring AMR genes among countries and between the environment and the clinic, representing a public health threat that necessitates international solidarity to overcome.

Antibiotic Discovery and Resistance: The Chase and the Race

The history of antimicrobial resistance (AMR) evolution and the diversity of the environmental resistome indicate that AMR is an ancient natural phenomenon. Acquired resistance is a public health concern influenced by the anthropogenic use of antibiotics, leading to the selection of resistant genes. Data show that AMR is spreading globally at different rates, outpacing all efforts to mitigate this crisis. The search for new antibiotic classes is one of the key strategies in the fight against AMR. Since the 1980s, newly marketed antibiotics were either modifications or improvements of known molecules. The World Health Organization (WHO) describes the current pipeline as bleak, and warns about the scarcity of new leads. A quantitative and qualitative analysis of the pre-clinical and clinical pipeline indicates that few antibiotics may reach the market in a few years, predominantly not those that fit the innovative requirements to tackle the challenging spread of AMR. Diversity and innovation are the mainstays to cope with the rapid evolution of AMR. The discovery and development of antibiotics must address resistance to old and novel antibiotics. Here, we review the history and challenges of antibiotics discovery and describe different innovative new leads mechanisms expected to replenish the pipeline, while maintaining a promising possibility to shift the chase and the race between the spread of AMR, preserving antibiotic effectiveness, and meeting innovative leads requirements.

In Vivo Potentiation of Antimicrobial Photodynamic Therapy in a Mouse Model of Fungal Infection by Addition of Potassium Iodide

Antimicrobial photodynamic inactivation (aPDI) involves the use of a nontoxic dye or photosensitizer excited with visible light to produce reactive oxygen species that can kill all classes of microorganisms. Antimicrobial photodynamic therapy (aPDT) can be used in vivo as an alternative therapeutic strategy to treat localized infections due to its ability to selectively kill microbes while preserving host mammalian cells. aPDI can be potentiated by the addition of the nontoxic inorganic salt potassium iodide (KI). KI is an approved drug for antifungal therapy. The mechanism of potentiation with iodide is likely to be singlet oxygen addition to iodide to form iodine radicals, hydrogen peroxide, and molecular iodine. A previous chapter in this volume described potentiation of aPDI in vitro by addition of KI, while in this chapter we address the ability of KI to potentiate aPDT in vivo using an animal model of localized fungal infection. We employed oral candidiasis in immunosuppressed mice caused by a bioluminescent strain of Candida albicans and monitored by bioluminescence imaging.

RISK FACTORS FOR SURGICAL WOUND INFECTION AFTER ELECTIVE LAPAROSCOPIC CHOLECYSTECTOMY

One of the ways to avoid infection after surgical procedures is through antibiotic prophylaxis. This occurs in cholecystectomies with certain risk factors for infection. However, some guidelines suggest the use of antibiotic prophylaxis for all cholecystectomies, although current evidence does not indicate any advantage of this practice in the absence of risk factors.

RISK FACTORS FOR SURGICAL WOUND INFECTION AFTER ELECTIVE LAPAROSCOPIC CHOLECYSTECTOMY

BACKGROUND:

One of the ways to avoid infection after surgical procedures is through antibiotic prophylaxis. This occurs in cholecystectomies with certain risk factors for infection. However, some guidelines suggest the use of antibiotic prophylaxis for all cholecystectomies, although current evidence does not indicate any advantage of this practice in the absence of risk factors.

AIMS:

This study aims to evaluate the incidence of wound infection after elective laparoscopic cholecystectomies and the use of antibiotic prophylaxis in these procedures.

METHODS:

This is a retrospective study of 439 patients with chronic cholecystitis and cholelithiasis, accounting for different risk factors for wound infection.

RESULTS:

There were seven cases of wound infection (1.59%). No antibiotic prophylaxis regimen significantly altered infection rates. There was a statistically significant correlation between wound infection and male patients (p=0.013). No other analyzed risk factor showed a statistical correlation with wound infection.

CONCLUSIONS:

The nonuse of antibiotic prophylaxis and other analyzed factors did not present a significant correlation for the increase in the occurrence of wound infection. Studies with a larger sample and a control group without antibiotic prophylaxis are necessary.

Plant-derived nanotherapeutic systems to counter the overgrowing threat of resistant microbes and biofilms

Since antiquity, the survival of human civilization has always been threatened by the microbial infections. An alarming surge in the resistant microbial strains against the conventional drugs is quite evident in the preceding years. Furthermore, failure of currently available regimens of antibiotics has been highlighted by the emerging threat of biofilms in the community and hospital settings. Biofilms are complex dynamic composites rich in extracellular polysaccharides and DNA, supporting plethora of symbiotic microbial life forms, that can grow on both living and non-living surfaces. These enforced structures are impervious to the drugs and lead to spread of recurrent and non-treatable infections. There is a strong realization among the scientists and healthcare providers to work out alternative strategies to combat the issue of drug resistance and biofilms. Plants are a traditional but rich source of effective antimicrobials with wider spectrum due to presence of multiple constituents in perfect synergy. Other than the biocompatibility and the safety profile, these phytochemicals have been repeatedly proven to overcome the non-responsiveness of resistant microbes and films via multiple pathways such as blocking the efflux pumps, better penetration across the cell membranes or biofilms, and anti-adhesive properties. However, the unfavorable physicochemical attributes and stability issues of these phytochemicals have hampered their commercialization. These issues of the phytochemicals can be solved by designing suitably constructed nanoscaled structures. Nanosized systems can not only improve the physicochemical features of the encapsulated payloads but can also enhance their pharmacokinetic and therapeutic profile. This review encompasses why and how various types of phytochemicals and their nanosized preparations counter the microbial resistance and the biofouling. We believe that phytochemical in tandem with nanotechnological innovations can be employed to defeat the microbial resistance and biofilms. This review will help in better understanding of the challenges associated with developing such platforms and their future prospects.

Paradox of complex diversity: Challenges in the diagnosis and management of bacterial keratitis

Bacterial keratitis continues to be one of the leading causes of corneal blindness in the developed as well as the developing world, despite swift progress since the dawn of the "anti-biotic era". Although, we are expeditiously developing our understanding about the different causative organisms and associated pathology leading to keratitis, extensive gaps in knowledge continue to dampen the efforts for early and accurate diagnosis, and management in these patients, resulting in poor clinical outcomes. The ability of the causative bacteria to subdue the therapeutic challenge stems from their large genome encoding complex regulatory networks, variety of unique virulence factors, and rapid secretion of tissue damaging proteases and toxins. In this review article, we have provided an overview of the established classical diagnostic techniques and therapeutics for keratitis caused by various bacteria. We have extensively reported our recent in-roads through novel tools for accurate diagnosis of mono- and poly-bacterial corneal infections. Furthermore, we outlined the recent progress by our group and others in understanding the sub-cellular genomic changes that lead to antibiotic resistance in these organisms. Finally, we discussed in detail, the novel therapies and drug delivery systems in development for the efficacious management of bacterial keratitis.

Responses of sediment resistome, virulence factors and potential pathogens to decades of antibiotics pollution in a shrimp aquafarm

Aquaculture ecosystem has become a hotspot of antibiotics resistance genes (ARGs) dissemination, owing to the abuse of prophylactic antibiotics. However, it is still unclear how and to what extent ARGs respond to the increasing antibiotic pollution, a trend as expected and as has occurred. Herein, a significant sediment antibiotic pollution gradient was detected along a drainage ditch after decades of shrimp aquaculture. The increasing antibiotic pollution evidently promoted the diversities and tailored the community structures of ARGs, mobile genetic elements (MGEs), virulence factors and pathogens. The profiles of ARGs and MGEs were directly altered by the concentrations of terramycin and sulphadimidine. By contrast, virulence factors were primarily affected by nutrient variables in sediment. The pathogens potentially hosted diverse virulence factors and ARGs. More than half of the detected ARGs subtypes non-linearly responded to increasing antibiotic pollution, as supported by significant tipping points. However, we screened seven antibiotic concentration discriminatory ARGs that could serve as independent variable for quantitatively diagnosing total antibiotic concentration. Co-occurrence analysis depicted that notorious aquaculture pathogens of Vibrio harveyi and V. parahaemolyticus potentially hosted ARGs that confer resistance to multiple antibiotics, while priority pathogens for humankind, e.g., Helicobacter pylori and Staphylococcus aureus, could have harbored redundant virulence factors. Collectively, the significant tipping points and antibiotic concentration-discriminatory ARGs may translate into warning index and diagnostic approach for diagnosing antibiotic pollution. Our findings provided novel insights into the interplay among ARGs, MGEs, pathogens, virulence factors and geochemical variables under the scenario of increasing antibiotic pollution.

The Case against Antibiotics and for Anti-Virulence Therapeutics

Although antibiotics have been indispensable in the advancement of modern medicine, there are downsides to their use. Growing resistance to broad-spectrum antibiotics is leading to an epidemic of infections untreatable by first-line therapies. Resistance is exacerbated by antibiotics used as growth factors in livestock, over-prescribing by doctors, and poor treatment adherence by patients. This generates populations of resistant bacteria that can then spread resistance genes horizontally to other bacterial species, including commensals. Furthermore, even when antibiotics are used appropriately, they harm commensal bacteria leading to increased secondary infection risk. Effective antibiotic treatment can induce bacterial survival tactics, such as toxin release and increasing resistance gene transfer. These problems highlight the need for new approaches to treating bacterial infection. Current solutions include combination therapies, narrow-spectrum therapeutics, and antibiotic stewardship programs. These mediate the issues but do not address their root cause. One emerging solution to these problems is anti-virulence treatment: preventing bacterial pathogenesis instead of using bactericidal agents. In this review, we discuss select examples of potential anti-virulence targets and strategies that could be developed into bacterial infection treatments: the bacterial type III secretion system, quorum sensing, and liposomes.

Tracing Antibiotic Resistance Genes along the Irrigation Water Chain to Chive: Does Tap or Surface Water Make a Difference?

Irrigation water is well known as potential source of pathogens in fresh produce. However, its role in transferring antibiotic resistance determinants is less well investigated. Therefore, we analyzed the contribution of surface and tap water to the resistome of overhead-irrigated chive plants. Field-grown chive was irrigated with either surface water (R-system) or tap water (D-system), from planting to harvest. Water along the two irrigation chains as well as the respective plants were repeatedly sampled and screened for 264 antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs), using high-capacity qPCR. Differentially abundant (DA) ARGs were determined by comparing the two systems. On R-chive, β-lactam ARGs, multidrug-resistance (MDR) determinants, and MGEs were most abundant, while D-chive featured DA ARGs from the vancomycin class. Diversity and number of DA ARGs was the highest on young chives, strongly diminished at harvest, and increased again at the end of shelf life. Most ARGs highly enriched on R- compared to D-chive were also enriched in R- compared to D-sprinkler water, indicating that water played a major role in ARG enrichment. Of note, blaKPC was detected at high levels in surface water and chive. We conclude that water quality significantly affects the resistome of the irrigated produce.

Antimicrobial stewardship program in pediatric medicine

The rising threats from antimicrobial resistance due to inappropriate utilization of antimicrobial agents in health care including the pediatric population has been a topic of concern at the global level for the last several decades. The antimicrobial stewardship program (ASP) is a multidisciplinary institutional initiative focusing primarily on the improvement of antimicrobial prescribing practices and limiting inappropriate use. ASPs play an important role in the implementation of healthcare strategies in pediatrics worldwide to reduce antimicrobial resistance. Many published reports demonstrate how adapted ASPs in pediatrics result in improvement of unnecessary antimicrobial utilization, decreasing drug resistance and treatment failure, minimization of adverse clinical outcomes, decreasing healthcare costs and hospital length of stay, and optimization of diagnostic strategies. However, some barriers in pediatric ASP still exist. This narrative review describes core elements of ASP, the impact of implemented ASPs on pediatric healthcare, and challenges of pediatric ASP as seen by the authors.

Pyranoanthocyanins Interfering with the Quorum Sensing of Pseudomonas aeruginosa and Staphylococcus aureus

Bacterial quorum sensing (QS) is a cell-cell communication system that regulates several bacterial mechanisms, including the production of virulence factors and biofilm formation. Thus, targeting microbial QS is seen as a plausible alternative strategy to antibiotics, with potentiality to combat multidrug-resistant pathogens. Many phytochemicals with QS interference activity are currently being explored. Herein, an extract and a compound of bioinspired origin were tested for their ability to inhibit biofilm formation and interfere with the expression of QS-related genes in Pseudomonas aeruginosa and Staphylococcus aureus. The extract, a carboxypyranoanthocyanins red wine extract (carboxypyrano-ant extract), and the pure compound, carboxypyranocyanidin-3-O-glucoside (carboxypyCy-3-glc), did not cause a visible effect on the biofilm formation of the P. aeruginosa biofilms; however, both significantly affected the formation of biofilms by the S. aureus strains, as attested by the crystal violet assay and fluorescence microscopy. Both the extract and the pure compound significantly interfered with the expression of several QS-related genes in the P. aeruginosa and S. aureus biofilms, as per reverse transcription-quantitative polymerase chain reaction (RT-qPCR) results. Indeed, it was possible to conclude that these molecules interfere with QS at distinct stages and in a strain-specific manner. An extract with anti-QS properties could be advantageous because it is easily obtained and could have broad, antimicrobial therapeutic applications if included in topical formulations.

Antibacterial potential of selected phytomolecules: An experimental study

Antibiotic resistance is a snowballing international threat. Some of the antibiotics have lost their effectiveness due to overuse and underuse. Thus, there is an urgent need to tackle this global challenge, either by inhibiting the resistance mechanisms or by the development of new chemical entities. Thus, in the current study, the antibacterial activity of selected phytomolecules was investigated against bacterial strains, alone and in combination, with standard drugs. The antibacterial potential of these phytomolecules was explored using in vitro assays (microtiter assay, bacterial growth kinetics, percentage retardation of growth, and antimicrobial synergy study) and in vivo studies (zebrafish infection model). In vitro and in vivo studies have shown promising antibacterial effects against, both, Gram-positive and Gram-negative bacteria. Moreover, a cell viability assay also indicated the cytoprotective effect of these phytomolecules in combination with standard antibiotics (SABX). Thus, these phytomolecules could be a promising broad-spectrum antibacterial agent in combination with standard antibiotics.

The Functional Significance of Hydrophobic Residue Distribution in Bacterial Beta-Barrel Transmembrane Proteins

β-barrel membrane proteins have several important biological functions, including transporting water and solutes across the membrane. They are active in the highly hydrophobic environment of the lipid membrane, as opposed to soluble proteins, which function in a more polar, aqueous environment. Globular soluble proteins typically have a hydrophobic core and a polar surface that interacts favorably with water. In the fuzzy oil drop (FOD) model, this distribution is represented by the 3D Gauss function (3DG). In contrast, membrane proteins expose hydrophobic residues on the surface, and, in the case of ion channels, the polar residues face inwards towards a central pore. The distribution of hydrophobic residues in membrane proteins can be characterized by means of 1–3DG, a complementary 3D Gauss function. Such an analysis was carried out on the transmembrane proteins of bacteria, which, despite the considerable similarities of their super-secondary structure (β-barrel), have highly differentiated properties in terms of stabilization based on hydrophobic interactions. The biological activity and substrate specificity of these proteins are determined by the distribution of the polar and nonpolar amino acids. The present analysis allowed us to compare the ways in which the different proteins interact with antibiotics and helped us understand their relative importance in the development of the resistance mechanism. We showed that beta barrel membrane proteins with a hydrophobic core interact less strongly with the molecules they transport.

Coming from the Wild: Multidrug Resistant Opportunistic Pathogens Presenting a Primary, Not Human-Linked, Environmental Habitat

The use and misuse of antibiotics have made antibiotic-resistant bacteria widespread nowadays, constituting one of the most relevant challenges for human health at present. Among these bacteria, opportunistic pathogens with an environmental, non-clinical, primary habitat stand as an increasing matter of concern at hospitals. These organisms usually present low susceptibility to antibiotics currently used for therapy. They are also proficient in acquiring increased resistance levels, a situation that limits the therapeutic options for treating the infections they cause. In this article, we analyse the most predominant opportunistic pathogens with an environmental origin, focusing on the mechanisms of antibiotic resistance they present. Further, we discuss the functions, beyond antibiotic resistance, that these determinants may have in the natural ecosystems that these bacteria usually colonize. Given the capacity of these organisms for colonizing different habitats, from clinical settings to natural environments, and for infecting different hosts, from plants to humans, deciphering their population structure, their mechanisms of resistance and the role that these mechanisms may play in natural ecosystems is of relevance for understanding the dissemination of antibiotic resistance under a One-Health point of view.

Antibiotic resistance: Time of synthesis in a post-genomic age

Antibiotic resistance has been highlighted by international organizations, including World Health Organization, World Bank and United Nations, as one of the most relevant global health problems. Classical approaches to study this problem have focused in infected humans, mainly at hospitals. Nevertheless, antibiotic resistance can expand through different ecosystems and geographical allocations, hence constituting a One-Health, Global-Health problem, requiring specific integrative analytic tools. Antibiotic resistance evolution and transmission are multilayer, hierarchically organized processes with several elements (from genes to the whole microbiome) involved. However, their study has been traditionally gene-centric, each element independently studied. The development of robust-economically affordable whole genome sequencing approaches, as well as other -omic techniques as transcriptomics and proteomics, is changing this panorama. These technologies allow the description of a system, either a cell or a microbiome as a whole, overcoming the problems associated with gene-centric approaches. We are currently at the time of combining the information derived from -omic studies to have a more holistic view of the evolution and spread of antibiotic resistance. This synthesis process requires the accurate integration of -omic information into computational models that serve to analyse the causes and the consequences of acquiring AR, fed by curated databases capable of identifying the elements involved in the acquisition of resistance. In this review, we analyse the capacities and drawbacks of the tools that are currently in use for the global analysis of AR, aiming to identify the more useful targets for effective corrective interventions.

The European Union Summary Report on Antimicrobial Resistance in zoonotic and indicator bacteria from humans, animals and food in 2018/2019

Data on antimicrobial resistance (AMR) in zoonotic and indicator bacteria from humans, animals and food are collected annually by the EU Member States (MSs), jointly analysed by the EFSA and the ECDC and reported in a yearly EU Summary Report. The annual monitoring of AMR in animals and food within the EU is targeted at selected animal species corresponding to the reporting year. The 2018 monitoring specifically focussed on poultry and their derived carcases/meat, while the monitoring performed in 2019 specifically focused on pigs and calves under 1 year of age, as well as their derived carcases/meat. Monitoring and reporting of AMR in 2018/2019 included data regarding Salmonella, Campylobacter and indicator Escherichia coli isolates, as well as data obtained from the specific monitoring of presumptive ESBL-/AmpC-/carbapenemase-producing E. coli isolates. Additionally, some MSs reported voluntary data on the occurrence of meticillin-resistant Staphylococcus aureus in animals and food, with some countries also providing data on antimicrobial susceptibility. This report provides an overview of the main findings of the 2018/2019 harmonised AMR monitoring in the main food-producing animal populations monitored, in related carcase/meat samples and in humans. Where available, data monitoring obtained from pigs, calves, broilers, laying hens and turkeys, as well as from carcase/meat samples and humans were combined and compared at the EU level, with particular emphasis on multidrug resistance, complete susceptibility and combined resistance patterns to critically important antimicrobials, as well as Salmonella and E. coli isolates possessing ESBL-/AmpC-/carbapenemase phenotypes. The outcome indicators for AMR in food-producing animals such as complete susceptibility to the harmonised panel of antimicrobials in E. coli and the prevalence of ESBL-/AmpC-producing E. coli have been also specifically analysed over the period 2015-2019.

Polyphenols against infectious diseases: Controlled release nano-formulations

The emergence of multi-drug resistant (MDR) pathogens has become a global threat and a cause of significant morbidity and mortality around the world. Natural products have been used as a promising approach to counter the infectious diseases associated with these pathogens. The application of natural products and their derivatives especially polyphenolic compounds as antibacterial agents is an active area of research, and prior studies have successfully treated a variety of bacterial infections using these polyphenolic compounds. However, delivery of polyphenolic compounds has been challenging due to their physicochemical properties and often poor aqueous solubility. In this regard, nanotechnology-based novel drug delivery systems offer many advantages, including improving bioavailability and the controlled release of polyphenolic compounds. This review summarizes the pharmacological mechanism and use of nano-formulations in developing controlled release delivery systems of naturally occurring polyphenols in infectious diseases.

Aminoacyl-tRNA Synthetases as Valuable Targets for Antimicrobial Drug Discovery

Aminoacyl-tRNA synthetases (aaRSs) catalyze the esterification of tRNA with a cognate amino acid and are essential enzymes in all three kingdoms of life. Due to their important role in the translation of the genetic code, aaRSs have been recognized as suitable targets for the development of small molecule anti-infectives. In this review, following a concise discussion of aaRS catalytic and proof-reading activities, the various inhibitory mechanisms of reported natural and synthetic aaRS inhibitors are discussed. Using the expanding repository of ligand-bound X-ray crystal structures, we classified these compounds based on their binding sites, focusing on their ability to compete with the association of one, or more of the canonical aaRS substrates. In parallel, we examined the determinants of species-selectivity and discuss potential resistance mechanisms of some of the inhibitor classes. Combined, this structural perspective highlights the opportunities for further exploration of the aaRS enzyme family as antimicrobial targets.

Treatment Processes for Microbial Resistance Mitigation: The Technological Contribution to Tackle the Problem of Antibiotic Resistance

Advances generated in medicine, science, and technology have contributed to a better quality of life in recent years; however, antimicrobial resistance has also benefited from these advances, creating various environmental and health problems. Several determinants may explain the problem of antimicrobial resistance, such as wastewater treatment plants that represent a powerful agent for the promotion of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARG), and are an important factor in mitigating the problem. This article focuses on reviewing current technologies for ARB and ARG removal treatments, which include disinfection, constructed wetlands, advanced oxidation processes (AOP), anaerobic, aerobic, or combined treatments, and nanomaterial-based treatments. Some of these technologies are highly intensive, such as AOP; however, other technologies require long treatment times or high doses of oxidizing agents. From this review, it can be concluded that treatment technologies must be significantly enhanced before the environmental and heath problems associated with antimicrobial resistance can be effectively solved. In either case, it is necessary to achieve total removal of bacteria and genes to avoid the possibility of regrowth given by the favorable environmental conditions at treatment plant facilities.

Emergence of Imipenem Resistance in a CpxA-H208P-Variant-Producing Proteus mirabilis Clinical Isolate

The Proteus mirabilis PmirS clinical isolate, which was susceptible to imipenem (0.5 μg/mL) and amikacin (1 μg/mL), was recovered from a bronchial aspirate of a patient who recently underwent lung transplantation. The P. mirabilis PmirR clinical isolate, which exhibited resistance to imipenem (16 μg/mL) and amikacin (24 μg/mL), was isolated 3 weeks later from the same patient and the same specimen type. Using short-read sequencing technology, these isolates appeared to be genetically identical except the cpxA gene of the PmirR isolate that was mutated leading to the His-208-Pro substitution. The structural alteration was localized in the histidine kinase, adenylate cyclase, methyl accepting protein, phosphatase (HAMP) domain, which is involved in the signal transduction between the sensor kinase and the regulator response of the CpxA/CpxR two-component system (TCS). No significant defect in the growth rate was found between the PmirS and PmirR isolates. This study suggests that alteration in CpxA might confer imipenem and amikacin resistance in P. mirabilis. This study brings new evidence that the TCS alteration could provide an adaptive capacity in a clinical context by conferring antibiotic resistance without fitness cost.

Long-lasting effects of antibiotics on bacterial communities of adult flies

Insect symbionts benefit their host and their study requires large spectrum antibiotic use like tetracycline to weaken or suppress symbiotic communities. While antibiotics have a negative impact on insect fitness, little is known about antibiotic effects on insect microbial communities and how long they last. We characterized the bacterial communities of adult cabbage root fly Delia radicum in a Wolbachia-free population and evaluated the effect of tetracycline treatment on these communities over several generations. Three D. radicum generations were used: the first- and second-generation flies either ingested tetracycline or not, while the third-generation flies were untreated but differed with their parents and/or grandparents that had or had not been treated. Fly bacterial communities were sequenced using a 16S rRNA gene. Tetracycline decreased fly bacterial diversity and induced modifications in both bacterial abundance and relative frequencies, still visible on untreated offspring whose parents and/or grandparents had been treated, therefore demonstrating long-lasting transgenerational effects on animal microbiomes after antibiotic treatment. Flies with an antibiotic history shared bacterial genera, potentially tetracycline resistant and heritable. Next, the transmission should be investigated by comparing several insect development stages and plant compartments to assess vertical and horizontal transmissions of D. radicum bacterial communities.

Antimicrobial resistance: more than 70 years of war between humans and bacteria

Development of antibiotic resistance in bacteria is one of the major issues in the present world and one of the greatest threats faced by mankind. Resistance is spread through both vertical gene transfer (parent to offspring) as well as by horizontal gene transfer like transformation, transduction and conjugation. The main mechanisms of resistance are limiting uptake of a drug, modification of a drug target, inactivation of a drug, and active efflux of a drug. The highest quantities of antibiotic concentrations are usually found in areas with strong anthropogenic pressures, for example medical source (e.g., hospitals) effluents, pharmaceutical industries, wastewater influents, soils treated with manure, animal husbandry and aquaculture (where antibiotics are generally used as in-feed preparations). Hence, the strong selective pressure applied by antimicrobial use has forced microorganisms to evolve for survival. The guts of animals and humans, wastewater treatment plants, hospital and community effluents, animal husbandry and aquaculture runoffs have been designated as "hotspots for AMR genes" because the high density of bacteria, phages, and plasmids in these settings allows significant genetic exchange and recombination. Evidence from the literature suggests that the knowledge of antibiotic resistance in the population is still scarce. Tackling antimicrobial resistance requires a wide range of strategies, for example, more research in antibiotic production, the need of educating patients and the general public, as well as developing alternatives to antibiotics (briefly discussed in the conclusions of this article).

Antibiotic Resistance: Moving From Individual Health Norms to Social Norms in One Health and Global Health

Antibiotic resistance is a problem for human health, and consequently, its study had been traditionally focused toward its impact for the success of treating human infections in individual patients (individual health). Nevertheless, antibiotic-resistant bacteria and antibiotic resistance genes are not confined only to the infected patients. It is now generally accepted that the problem goes beyond humans, hospitals, or long-term facility settings and that it should be considered simultaneously in human-connected animals, farms, food, water, and natural ecosystems. In this regard, the health of humans, animals, and local antibiotic-resistance-polluted environments should influence the health of the whole interconnected local ecosystem (One Health). In addition, antibiotic resistance is also a global problem; any resistant microorganism (and its antibiotic resistance genes) could be distributed worldwide. Consequently, antibiotic resistance is a pandemic that requires Global Health solutions. Social norms, imposing individual and group behavior that favor global human health and in accordance with the increasingly collective awareness of the lack of human alienation from nature, will positively influence these solutions. In this regard, the problem of antibiotic resistance should be understood within the framework of socioeconomic and ecological efforts to ensure the sustainability of human development and the associated human-natural ecosystem interactions.

Determination of the time-dependent association between ciprofloxacin consumption and ciprofloxacin resistance using a weighted cumulative exposure model compared with standard models

OBJECTIVES

To obtain comprehensive insight into the association of ciprofloxacin use at different times in the past with the current risk of detecting resistance.

METHODS

This retrospective nested case-control study of ciprofloxacin users used Dutch data from the PHARMO Database Network and one laboratory for the period 2003-14. Cases and controls were selected as patients with an antibiotic susceptibility test (AST) indicating ciprofloxacin resistance or susceptibility, respectively. We performed univariable and multivariable conditional logistic regression analyses, defining time-dependent exposure using standard definitions (current ciprofloxacin use, used 0-30, 31-90, 91-180 and 181-360 days ago) and a flexible weighted cumulative effect (WCE) model with four alternative time windows of past doses (0-30, 0-90, 0-180 and 0-360 days).

RESULTS

The study population consisted of 230 cases and 909 controls. Under the standard exposure definitions, the association of ciprofloxacin use with resistance decreased with time [current use: adjusted OR 6.8 (95% CI 3.6-12.4); used 181-360 days ago: 1.3 (0.8-1.9)]. Under the 90 day WCE model (best-fitting model), more recent doses were more strongly associated with resistance than past doses, as was longer or repeated treatment. The 180 day WCE model, which fitted the data equally well, suggested that doses taken 91-180 days ago were also significantly associated with resistance.

CONCLUSIONS

The estimates for the association between ciprofloxacin use at different times and resistance show that ciprofloxacin prescribers should consider ciprofloxacin use 0-180 days ago to ensure that patients receive suitable treatment. The OR of ciprofloxacin resistance could be reduced by eliminating repeated ciprofloxacin prescription within 180 days and by treating for no longer than necessary.

Current status of resistance to antibiotics in the Democratic Republic of the Congo: A review

A review of literature was conducted to assess the prevalence and mechanisms of antibiotic resistance to date, mainly to β-lactam antibiotics, cephalosporins, carbapenems, colistin, and tigecycline in the Democratic Republic of the Congo (DRC). English and French publications were listed and analysed using PubMed/Medline, Google Scholar, and African Journals database between 1 January 1990 and 31 December 2019. For the 30 published articles found: (1) bacterial resistance to antibiotics concerned both Gram-negative and Gram-positive bacteria; (2) multidrug resistance prevalence was the same in half of Streptococcus pneumoniae isolates; (3) a worrying prevalence of methicillin-resistant Staphylococcus aureus (MRSA) was noted, which is associated with co-resistance to several other antibiotics; and (4) resistance to third-generation cephalosporins was very high in Enterobacteriaceae, mainly because of bla_CTX-M-1 group and bla_SHV genes. Data on carbapenem and colistin resistance were not available in DRC until recently. Further work is required to set up a surveillance system for antibiotic resistance in DRC.

The Revaluation of Plant-Derived Terpenes to Fight Antibiotic-Resistant Infections

The discovery of antibiotics has revolutionized the medicine and treatment of microbial infections. However, the current scenario has highlighted the difficulties in marketing new antibiotics and an exponential increase in the appearance of resistant strains. On the other hand, research in the field of drug-discovery has revaluated the potential of natural products as a unique source for new biologically active molecules and scaffolds for the medicinal chemistry. In this review, we first contextualized the worldwide problem of antibiotic resistance and the importance that natural products of plant origin acquire as a source of new lead compounds. We then focused on terpenes and their potential development as antimicrobials, highlighting those studies that showed an activity against conventional antibiotic-resistant strains.

The Revaluation of Plant-Derived Terpenes to Fight Antibiotic-Resistant Infections

The discovery of antibiotics has revolutionized the medicine and treatment of microbial infections. However, the current scenario has highlighted the difficulties in marketing new antibiotics and an exponential increase in the appearance of resistant strains. On the other hand, research in the field of drug-discovery has revaluated the potential of natural products as a unique source for new biologically active molecules and scaffolds for the medicinal chemistry. In this review, we first contextualized the worldwide problem of antibiotic resistance and the importance that natural products of plant origin acquire as a source of new lead compounds. We then focused on terpenes and their potential development as antimicrobials, highlighting those studies that showed an activity against conventional antibiotic-resistant strains.

The Revaluation of Plant-Derived Terpenes to Fight Antibiotic-Resistant Infections

The discovery of antibiotics has revolutionized the medicine and treatment of microbial infections. However, the current scenario has highlighted the difficulties in marketing new antibiotics and an exponential increase in the appearance of resistant strains. On the other hand, research in the field of drug-discovery has revaluated the potential of natural products as a unique source for new biologically active molecules and scaffolds for the medicinal chemistry. In this review, we first contextualized the worldwide problem of antibiotic resistance and the importance that natural products of plant origin acquire as a source of new lead compounds. We then focused on terpenes and their potential development as antimicrobials, highlighting those studies that showed an activity against conventional antibiotic-resistant strains.

Discovery of indolyl-containing peptides as novel antibacterial agents targeting tryptophanyl-tRNA synthetase

Background: There is an urgent need for antibiotics with novel structures and unexploited targets to counteract bacterial resistance. Methodology & results: Novel tryptophanyl-tRNA synthetase inhibitors were discovered based on virtual screening, surface plasmon resonance binding, enzymatic activity assay and antibacterial activity evaluation. Of the 29 peptide derivatives tested for antibacterial activity, some inhibited the growth of both Staphylococcus aureus and Staphylococcus epidermidis. A13 and A15 exhibited antibacterial activity against methicillin-resistant S. aureus NRS384 at an 8 μg/ml minimum inhibitory concentration. A13 snugly docked into the active site, explaining its improved inhibitory activity. Conclusion: Our results provide us with new structural clues to develop more potent tryptophanyl-tRNA synthetase inhibitors and lay a solid foundation for future drug design efforts.

Instructive Advances in Chemical Microbiology Inspired by Nature's Diverse Inventory of Molecules

Natural product antibiotics have played an essential role in the treatment of bacterial infection in addition to serving as useful tools to explore the intricate biology of bacteria. Our current arsenal of antibiotics operate through the inhibition of well-defined bacterial targets critical for replication and growth. Pathogenic bacteria effectively utilize a diversity of mechanisms that lead to acquired resistance and/or innate tolerance toward antibiotic therapies, which can result in devastating consequences to human life. Several research groups have established innovative programs that work at the chemistry-biology interface to develop new molecules that aim to define and address concerns related to antibiotic resistance and tolerance. In this Review, we present recent progress by select research groups that highlight a diversity of integrated chemical biology and medicinal chemistry approaches aimed at the development and utilization of chemical tools that have led to promising new microbiological insights that may lead to significant clinical advances regarding the treatment of pathogenic bacteria.

Synthesis and Antibacterial Activity of Ionic Liquids and Organic Salts Based on Penicillin G and Amoxicillin hydrolysate Derivatives against Resistant Bacteria

The preparation and characterization of ionic liquids and organic salts (OSILs) that contain anionic penicillin G [secoPen] and amoxicillin [seco-Amx] hydrolysate derivatives and their in vitro antibacterial activity against sensitive and resistant Escherichia coli and Staphylococcus aureus strains is reported. Eleven hydrolyzed β-lactam-OSILs were obtained after precipitation in moderate-to-high yields via the neutralization of the basic ammonia buffer of antibiotics with different cation hydroxide salts. The obtained minimum inhibitory concentration (MIC) data of the prepared compounds showed a relative decrease of the inhibitory concentrations (RDIC) in the order of 100 in the case of [C₂OHMIM][seco-Pen] against sensitive S. aureus ATCC25923 and, most strikingly, higher than 1000 with [C₁₆Pyr][seco-Amx] against methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300. These outstanding in vitro results showcase that a straightforward transformation of standard antibiotics into hydrolyzed organic salts can dramatically change the pharmaceutical activity of a drug, including giving rise to potent formulations of antibiotics against deadly bacteria strains.

The European Union Summary Report on Antimicrobial Resistance in zoonotic and indicator bacteria from humans, animals and food in 2017/2018

Data on antimicrobial resistance (AMR) in zoonotic and indicator bacteria from humans, animals and food are collected annually by the EU Member States (MSs), jointly analysed by EFSA and ECDC and reported in a yearly EU Summary Report. The annual monitoring of AMR in animals and food within the EU is targeted at selected animal species corresponding to the reporting year. The 2017 monitoring specifically focussed on pigs and calves under 1 year of age, as well as their derived carcases/meat, while the monitoring performed in 2018 specifically focussed on poultry and their derived carcases/meat. Monitoring and reporting of AMR in 2017/2018 included data regarding Salmonella, Campylobacter and indicator Escherichia coli isolates, as well as data obtained from the specific monitoring of ESBL-/AmpC-/carbapenemase-producing E. coli isolates. Additionally, some MSs reported voluntary data on the occurrence of meticillin-resistant Staphylococcus aureus in animals and food, with some countries also providing data on antimicrobial susceptibility. This report provides, for the first time, an overview of the main findings of the 2017/2018 harmonised AMR monitoring in the main food-producing animal populations monitored, in related carcase/meat samples and in humans. Where available, data monitoring obtained from pigs, calves/cattle, broilers, laying hens and turkeys, as well as from carcase/meat samples and humans were combined and compared at the EU level, with particular emphasis on multiple drug resistance, complete susceptibility and combined resistance patterns to critically important antimicrobials, as well as Salmonella and E. coli isolates exhibiting presumptive ESBL-/AmpC-/carbapenemase-producing phenotypes. The outcome indicators for AMR in food-producing animals, such as complete susceptibility to the harmonised panel of antimicrobials in E. coli and the prevalence of ESBL-/AmpC-producing E. coli have been also specifically analysed over the period 2014-2018.

In vitro and in vivo efficacy study of cefepime, doripenem, tigecycline, and tetracycline against extended-spectrum beta-lactamases Escherichia coli in chickens

BACKGROUND AND AIM

At present, there are no data about the efficacy of some recent antibiotics on Escherichia coli in broiler chickens in the study area. This study was designed to evaluate the in vitro and in vivo efficacy of cefepime, doripenem, tigecycline, and tetracycline against multidrug-resistant-extended-spectrum beta-lactamases (MDR-ESBLs) producing E. coli in broiler chicks.

MATERIALS AND METHODS

A total of 34 MDR-ESBLs E. coli isolates were used in this study. In vitro evaluation of the antibacterial efficacy of cefepime, doripenem, tigecycline, and tetracycline were performed using disk diffusion and minimum inhibitory concentration (MIC) assays. In vivo evaluation of the efficacy of the antibiotics was perfumed using 180, 2-week-old chicks challenged with MDR-ESBL-producing E. coli strain O78. Chicks were divided into six groups (30 chicks each) according to the treatment regimen. Treatment was administered to chicks in Groups 3-6 intravenously, twice per day for 1 week using one antibiotic per group at concentration 10 times the determined MIC. Chicks in the positive control (Group 1) were challenged and received 0.2 ml of sterile Tryptone Soy Broth (TSB), while those in the negative control (Group 2) were not challenged and received 0.2 ml of sterile TSB. The severity of clinical signs, gross lesions, and mortality rate was scored and compared between groups.

RESULTS

All E. coli isolates were sensitive to doripenem and tigecycline, while 88% were sensitive to cefepime and only 23% were sensitive to tetracycline. In vivo antibiotic efficacy evaluation in challenged chicks revealed a significant reduction in the severity of clinical signs, gross lesions, and mortality (3%) in chicks treated with cefepime compared to non-treated chicks (55%). There was no significant effect on the severity of clinical signs, gross lesions, and mortality in chicks treated with doripenem, tigecycline, and tetracycline compared to non-treated chicks. The mortality rates of chicks treated with doripenem, tigecycline, and tetracycline were 57%, 50%, and 90%, respectively.

CONCLUSION

The results of this study indicate that most MDR-ESBLs producing E. coli isolates were sensitive to doripenem, tigecycline, and cefepime. However, in vivo study indicated that only cefepime was effective and resulted in a significant reduction in clinical signs, gross lesions, and mortality in infected chicks. Therefore, cefepime could be used to treat naturally infected chickens with MDR-ESBLs producing strains of E. coli.

Proportion of bacterial isolates, their antimicrobial susceptibility profile and factors associated with puerperal sepsis among post-partum/aborted women at a referral Hospital in Bahir Dar, Northwest Ethiopia

Background

Puerperal sepsis is any bacterial infection of the genital tract that occurs after childbirth. It is among the leading causes of maternal morbidity and mortality especially in low-income countries including Ethiopia. The aim of this study was to determine the proportion of bacterial isolates, their antimicrobial susceptibility profile and factors associated with puerperal sepsis among post-partum/aborted women at a Referral Hospital in Bahir Dar, Northwest Ethiopia.

Methods

A cross sectional study was conducted from January to May 2017 among 166 post-partum/aborted women admitted to Felege Hiwot Referral Hospital for medical services and suspected for puerperal sepsis.. Socio-demographic data and associated factors were collected using structured questionnaire. Bacteria were isolated and identified from blood samples on Trypton soya broth, blood, Chocolate and MacConkey agars following standard bacteriological procedures. The VITEK 2 identification and susceptibility testing system was used to determine the antimicrobial susceptibility profiles of bacterial isolates. Data were entered and analyzed using SPSS version 20. Factors associated with puerperal sepsis were considered statistically significant at P-value < 0.05.

Results

The overall proportion of bacterial isolates among post-partum/aborted women was 33.7% (56/166); of which 55.4% was caused by Gram-negative and 44.6% was by Gram-positive bacteria. The most frequently isolated bacteria were Escherichia coli (32.1%) from Gram-negatives and Staphylococcus aureus (33.9%) from Gram-positives. The proportion of other isolates was (7.2%) for Coagulase Negative Staphylococci (CoNS), (12.5%) for Klebsiella pneumoniae, (10.7%) for Acinetobacter baumanni and (3.6%) for Raoultella ornithinolytica. All isolates of Gram-positive and Gram-negative bacteria were resistant to tetracycline (100%). The gram negatives show resistance to Cefazolin (72.7%), Tetracycline (93.9%) and Ampicillin (100%). The overall prevalence of multidrug resistance (MDR) was 84%. Women having multiparous parity were more likely to develop puerperal sepsis than primiparous parity (AOR 4.045; 95% CI: 1.479-11.061; P < 0.05). Other socio-demographic and clinical factors had no significant association with puerperal sepsis.

Conclusion

About one third of post-partum/aborted women suspected for puerperal sepsis were infected with one or more bacterial isolates. Significant proportion of bacterial isolates showed mono and multi-drug resistance for the commonly prescribed antibiotics. Women with multiparous parity were more likely to develop puerperal sepsis than primiparous parity.

β-Lactamase Inhibitors To Restore the Efficacy of Antibiotics against Superbugs

Infections caused by resistant bacteria are nowadays too common, and some pathogens have even become resistant to multiple types of antibiotics, in which case few or even no treatments are available. In recent years, the most successful strategy in anti-infective drug discovery for the treatment of such problematic infections is the combination therapy "antibiotic + inhibitor of resistance". These inhibitors allow the repurposing of antibiotics that have already proven to be safe and effective for clinical use. Three main types of compounds have been developed to block the principal bacterial resistance mechanisms: (i) β-lactamase inhibitors; (ii) outer membrane permeabilizers; (iii) efflux pump inhibitors. This Perspective is focused on β-lactamase inhibitors that disable the most prevalent cause of antibiotic resistance in Gram-negative bacteria, i.e., the deactivation of the most widely used antibiotics, β-lactams (penicillins, cephalosporines, carbapenems, and monobactams), by the production of β-lactamases. An overview of the most recently identified β-lactamase inhibitors and of combination therapy is provided. The article also covers the mechanism of action of the different types of β-lactamase enzymes as a basis for inhibitor design and target inactivation.