Gold nanoparticles-doped MXene heterostructure for ultrasensitive electrochemical detection of fumonisin B1 and ampicillin.

Early transition metal carbides (MXene) hybridized by precious metals open a door for innovative electrochemical biosensing device design. Herein, we present a facile one-pot synthesis of gold nanoparticles (AuNPs)-doped two-dimensional (2D) titanium carbide MXene nanoflakes (Ti3C2Tx/Au). Ti3C2Tx MXene exhibits high electrical conductivity and yields synergistic signal amplification in conjunction with AuNPs leading to excellent electrochemical performance. Thus Ti3C2Tx/Au hybrid nanostructure can be used as an electrode platform for the electrochemical analysis of various targets. We used screen-printed electrodes modified with the Ti3C2Tx/Au electrode and functionalized with different biorecognition elements to detect and quantify an antibiotic, ampicillin (AMP), and a mycotoxin, fumonisin B1 (FB1). The ultralow limits of detection of 2.284 pM and 1.617 pg.mL-1, which we achieved respectively for AMP and FB1 are far lower than their corresponding maximum residue limits of 2.8 nM in milk and 2 to 4 mg kg-1 in corn products for human consumption set by the United States Food and Drug Administration. Additionally, the linear range of detection and quantification of AMP and FB1 were, respectively, 10 pM to 500 nM and 10 pg mL-1 to 1 µg mL-1. The unique structure and excellent electrochemical performance of Ti3C2Tx/Au nanocomposite suggest that it is highly suitable for anchoring biorecognition entities such as antibodies and oligonucleotides for monitoring various deleterious contaminants in agri-food products.

Blue light-mediated gene expression as a promising strategy to reduce antibiotic resistance in Escherichia coli.

The discovery of antibiotics has noticeably promoted the development of human civilization; however, antibiotic resistance in bacteria caused by abusing and overusing greatly challenges human health and food safety. Considering the worsening situation, it is an urgent demand to develop emerging nontraditional technologies or methods to address this issue. With the expanding of synthetic biology, optogenetics exhibits a tempting prospect for precisely regulating gene expression in many fields. Consequently, it is attractive to employ optogenetics to reduce the risk of antibiotic resistance. Here, a blue light-controllable gene expression system was established in Escherichia coli based on a photosensitive DNA-binding protein (EL222). Further, this strategy was successfully applied to repress the expression of ß-lactamase gene (bla) using blue light illumination, resulting a dramatic reduction of ampicillin resistance in engineered E. coli. Moreover, blue light was utilized to induce the expression of the mechanosensitive channel of large conductance (MscL), triumphantly leading to the increase of streptomycin susceptibility in engineered E. coli. Finally, the increased susceptibility of ampicillin and streptomycin was simultaneously induced by blue light in the same E. coli cell, revealing the excellent potential of this strategy in controlling multidrug-resistant (MDR) bacteria. As a proof of concept, our work demonstrates that light can be used as an alternative tool to prolong the use period of common antibiotics without developing new antibiotics. And this novel strategy based on optogenetics shows a promising foreground to combat antibiotic resistance in the future.

Dual-channel fluorescent sensors based on chitosan-coated Mn-doped ZnS micromaterials to detect ampicillin.

The global threat of antibiotic resistance has increased the importance of the detection of antibiotics. Conventional methods to detect antibiotics are time-consuming and require expensive specialized equipment. Here, we present a simple and rapid biosensor for detecting ampicillin, a commonly used antibiotic. Our method is based on the fluorescent properties of chitosan-coated Mn-doped ZnS micromaterials combined with the ß-lactamase enzyme. The biosensors exhibited the highest sensitivity in a linear working range of 13.1-72.2 pM with a limit of detection of 8.24 pM in deionized water. In addition, due to the biological specificity of ß-lactamase, the proposed sensors have demonstrated high selectivity over penicillin, tetracycline, and glucose through the enhancing and quenching effects at wavelengths of 510 nm and 614 nm, respectively. These proposed sensors also showed promising results when tested in various matrices, including tap water, bottled water, and milk. Our work reports for the first time the cost-effective (Mn:ZnS)Chitosan micromaterial was used for ampicillin detection. The results will facilitate the monitoring of antibiotics in clinical and environmental contexts.

Genomic context as well as sequence of both psr and penicillin-binding protein 5 contributes to ß-lactam resistance in Enterococcus faecium.

Penicillin-binding protein 5 (PBP5) of Enterococcus faecium (Efm) is vital for ampicillin resistance (AMP-R). We previously designated three forms of PBP5, namely, PBP5-S in Efm clade B strains [ampicillin susceptible (AMP-S)], PBP5-S/R (AMP-S or R), and PBP5-R (AMP-R) in clade A strains. Here, pbp5 deletion resulted in a marked reduction in AMP minimum inhibitory concentrations (MICs) to 0.01-0.09 µg/mL for clade B and 0.12-0.19 µg/mL for clade A strains; in situ complementation restored parental AMP MICs. Using D344SRF (lacking ftsW/psr/pbp5), constructs with ftsWA/psrA (from a clade A1 strain) cloned upstream of pbp5-S and pbp5-S/R alleles resulted in modest increases in MICs to 3-8 µg/mL, while high MICs (>64 µg/mL) were seen using pbp5 from A1 strains. Next, using ftsW ± psr from clade B and clade A/B and B/A hybrid constructs, the presence of psrB, even alone or in trans, resulted in much lower AMP MICs (3-8 µg/mL) than when psrA was present (MICs >64 µg/mL). qRT PCR showed relatively greater pbp5 expression (P = 0.007) with pbp5 cloned downstream of clade A1 ftsW/psr (MIC >128 µg/mL) vs when cloned downstream of clade B ftsW/psr (MIC 4-16 µg/mL), consistent with results in western blots. In conclusion, we report the effect of clade A vs B psr on AMP MICs as well as the impact of pbp5 alleles from different clades. While previously, Psr was not thought to contribute to AMP MICs in Efm, our results showed that the presence of psrB resulted in a major decrease in Efm AMP MICs. IMPORTANCE: The findings of this study shed light on ampicillin resistance in Enterococcus faecium clade A strains. They underscore the significance of alterations in the amino acid sequence of penicillin-binding protein 5 (PBP5) and the pivotal role of the psr region in PBP5 expression and ampicillin resistance. Notably, the presence of a full-length psrB leads to reduced PBP5 expression and lower minimum inhibitory concentrations (MICs) of ampicillin compared to the presence of a shorter psrA, regardless of the pbp5 allele involved. Additionally, clade B E. faecium strains exhibit lower AMP MICs when both psr alleles from clades A and B are present, although it is important to consider other distinctions between clade A and B strains that may contribute to this effect. It is intriguing to note that the divergence between clade A and clade B E. faecium and the subsequent evolution of heightened AMP MICs in hospital-associated strains appear to coincide with changes in Pbp5 and psr. These changes in psr may have resulted in an inactive Psr, facilitating increased PBP5 expression and greater ampicillin resistance. These results raise the possibility that a mimicker of PsrB, if one could be designed, might be able to lower MICs of ampicillin-resistant E. faecium, thus potentially resorting ampicillin to our therapeutic armamentarium for this species.

Rapid evolutionary change in trait correlations of single proteins.

Many organismal traits are genetically determined and covary in evolving populations. The resulting trait correlations can either help or hinder evolvability - the ability to bring forth new and adaptive phenotypes. The evolution of evolvability requires that trait correlations themselves must be able to evolve, but we know little about this ability. To learn more about it, we here study two evolvable systems, a yellow fluorescent protein and the antibiotic resistance protein VIM-2 metallo beta-lactamase. We consider two traits in the fluorescent protein, namely the ability to emit yellow and green light, and three traits in our enzyme, namely the resistance against ampicillin, cefotaxime, and meropenem. We show that correlations between these traits can evolve rapidly through both mutation and selection on short evolutionary time scales. In addition, we show that these correlations are driven by a protein's ability to fold, because single mutations that alter foldability can dramatically change trait correlations. Since foldability is important for most proteins and their traits, mutations affecting protein folding may alter trait correlations mediated by many other proteins. Thus, mutations that affect protein foldability may also help shape the correlations of complex traits that are affected by hundreds of proteins.

Occurrence, antimicrobial susceptibility, and resistance genes of Staphylococcus aureus in milk and milk products in the Arsi highlands of Ethiopia.

BACKGROUND: In Ethiopia, milk production and handling practices often lack proper hygiene measures, leading to the potential contamination of milk and milk products with Staphylococcus aureus (S. aureus), including methicillin-resistant strains, posing significant public health concerns. This study aimed to investigate the occurrence, antimicrobial susceptibility profiles and presence of resistance genes in S. aureus strains isolated from milk and milk products. METHODS: A cross-sectional study was conducted in the Arsi highlands, Oromia, Ethiopia from March 2022 to February 2023. A total of 503 milk and milk product samples were collected, comprising 259 raw milk, 219 cottage cheese, and 25 traditional yogurt samples. S. aureus isolation and coagulase-positive staphylococci enumeration were performed using Baird-Parker agar supplemented with tellurite and egg yolk. S. aureus was further characterized based on colony morphology, Gram stain, mannitol fermentation, catalase test, and coagulase test. Phenotypic antimicrobial resistance was assessed using the Kirby-Bauer disc diffusion method, while the polymerase chain reaction (PCR) was employed for confirming the presence of S. aureus and detecting antimicrobial resistance genes. RESULTS: S. aureus was detected in 24.9% of the milk and milk products, with the highest occurrence in raw milk (40.9%), followed by yogurt (20%), and cottage cheese (6.4%). The geometric mean for coagulase-positive staphylococci counts in raw milk, yogurt, and cottage cheese was 4.6, 3.8, and 3.2 log10 CFU/mL, respectively. Antimicrobial resistance analysis revealed high levels of resistance to ampicillin (89.7%) and penicillin G (87.2%), with 71.8% of the isolates demonstrating multidrug resistance. Of the 16 S. aureus isolates analyzed using PCR, all were found to carry the nuc gene, with the mecA and blaZ genes detected in 50% of these isolates each. CONCLUSION: This study revealed the widespread distribution of S. aureus in milk and milk products in the Arsi highlands of Ethiopia. The isolates displayed high resistance to ampicillin and penicillin, with a concerning level of multidrug resistance. The detection of the mecA and blaZ genes in selected isolates is of particular concern, highlighting a potential public health hazard and posing a challenge to effective antimicrobial treatment. These findings highlight the urgent need to enhance hygiene standards in milk and milk product handling and promote the rational use of antimicrobial drugs. Provision of adequate training for all individuals involved in the dairy sector can help minimize contamination. These measures are crucial in addressing the threats posed by S. aureus, including methicillin-resistant strains, and ensuring the safety of milk and its products for consumers.

Structural and biochemical analysis of penicillin-binding protein 2 from Campylobacter jejuni.

Penicillin-binding protein 2 (PBP2) plays a key role in the formation of peptidoglycans in bacterial cell walls by crosslinking glycan chains through transpeptidase activity. PBP2 is also found in Campylobacter jejuni, a pathogenic bacterium that causes food-borne enteritis in humans. To elucidate the essential structural features of C. jejuni PBP2 (cjPBP2) that mediate its biological function, we determined the crystal structure of cjPBP2 and assessed its protein stability under various conditions. cjPBP2 adopts an elongated two-domain structure, consisting of a transpeptidase domain and a pedestal domain, and contains typical active site residues necessary for transpeptidase activity, as observed in other PBP2 proteins. Moreover, cjPBP2 responds to ß-lactam antibiotics, including ampicillin, cefaclor, and cefmetazole, suggesting that ß-lactam antibiotics inactivate cjPBP2. In contrast to typical PBP2 proteins, cjPBP2 is a rare example of a Zn2+-binding PBP2 protein, as the terminal structure of its transpeptidase domain accommodates a Zn2+ ion via three cysteine residues and one histidine residue. Zn2+ binding helps improve the protein stability of cjPBP2, providing opportunities to develop new C. jejuni-specific antibacterial drugs that counteract the Zn2+-binding ability of cjPBP2.

Crucifer Lesion-Associated Xanthomonas Strains Show Multi-Resistance to Heavy Metals and Antibiotics.

Copper resistance in phytopathogens is a major challenge to crop production globally and is known to be driven by excessive use of copper-based pesticides. However, recent studies have shown co-selection of multiple heavy metal and antibiotic resistance genes in bacteria exposed to heavy metal and xenobiotics, which may impact the epidemiology of plant, animal, and human diseases. In this study, multi-resistance to heavy metals and antibiotics were evaluated in local Xanthomonas campestris pv. campestris (Xcc) and co-isolated Xanthomonas melonis (Xmel) strains from infected crucifer plants in Trinidad. Resistance to cobalt, cadmium, zinc, copper, and arsenic (V) was observed in both Xanthomonas species up to 25 mM. Heavy metal resistance (HMR) genes were found on a small plasmid-derived locus with ~ 90% similarity to a Stenotrophomonas spp. chromosomal locus and a X. perforans pLH3.1 plasmid. The co-occurrence of mobile elements in these regions implies their organization on a composite transposon-like structure. HMR genes in Xcc strains showed the lowest similarity to references, and the cus and ars operons appear to be unique among Xanthomonads. Overall, the similarity of HMR genes to Stenotrophomonas sp. chromosomal genomes suggest their origin in this genus or a related organism and subsequent spread through lateral gene transfer events. Further resistome characterization revealed the presence of small multidrug resistance (SMR), multidrug resistance (MDR) efflux pumps, and bla (Xcc) genes for broad biocide resistance in both species. Concurrently, resistance to antibiotics (streptomycin, kanamycin, tetracycline, chloramphenicol, and ampicillin) up to 1000 µg/mL was confirmed.

Distribution of bacteria and antimicrobial resistance in retail Nile tilapia (Oreochromis spp.) as potential sources of foodborne illness.

This study aimed to investigate AMR profiles of Aeromonas hydrophila, Salmonella spp., and Vibrio cholerae isolated from Nile tilapia (Oreochromis spp.) (n = 276) purchased from fresh markets and supermarkets in Bangkok, Thailand. A sample of tilapia was divided into three parts: fish intestine (n = 276), fish meat (n = 276), and liver and kidney (n = 276). The occurrence of A. hydrophila, Salmonella, and V. cholerae was 3.1%, 7.4%, and 8.5%, respectively. A high prevalence of these pathogenic bacteria was observed in fresh market tilapia compared to those from supermarkets (p < 0.05). The predominant Salmonella serovars were Paratyphi B (6.4%), followed by Escanaba (5.7%), and Saintpaul (5.7%). All isolates tested positive for the virulence genes of A. hydrophila (aero and hly), Salmonella (invA), and V. cholerae (hlyA). A. hydrophila (65.4%), Salmonella (31.2%), and V. cholerae (2.9%) showed multidrug resistant isolates. All A. hydrophila isolates (n = 26) exhibited resistant to ampicillin (100.0%) and florfenicol (100.0%), and often carried sul1 (53.8%) and tetA (50.0%). Salmonella isolates were primarily resistant to ampicillin (36.9%), with a high incidence of blaTEM (26.2%) and qnrS (25.5%). For V. cholerae isolates, resistance was observed against ampicillin (48.6%), and they commonly carried qnrS (24.3%) and tetA (22.9%). To identify mutations in the quinolone resistance determining regions (QRDRs), a single C248A point mutation of C248A (Ser-83-Tyr) in the gyrA region was identified in six out of seven isolates of Salmonella isolates. This study highlighted the presence of antimicrobial-resistant pathogenic bacteria in Nile tilapia at a selling point. It is important to rigorously implement strategies for AMR control and prevention.

Exploring ex vivo biofilm dynamics: consequences of low ampicillin concentrations on the human oral microbiome.

Prolonged exposure to antibiotics at low concentration can promote processes associated with bacterial biofilm formation, virulence and antibiotic resistance. This can be of high relevance in microbial communities like the oral microbiome, where commensals and pathogens share a common habitat and where the total abundance of antibiotic resistance genes surpasses the abundance in the gut. Here, we used an ex vivo model of human oral biofilms to investigate the impact of ampicillin on biofilm viability. The ecological impact on the microbiome and resistome was investigated using shotgun metagenomics. The results showed that low concentrations promoted significant shifts in microbial taxonomic profile and could enhance biofilm viability by up to 1 to 2-log. For the resistome, low concentrations had no significant impact on antibiotic resistance gene (ARG) diversity, while ARG abundance decreased by up to 84%. A positive correlation was observed between reduced microbial diversity and reduced ARG abundance. The WHO priority pathogens Streptococcus pneumoniae and Staphylococcus aureus were identified in some of the samples, but their abundance was not significantly altered by ampicillin. Most of the antibiotic resistance genes that increased in abundance in the ampicillin group were associated with streptococci, including Streptococcus mitis, a well-known potential donor of ARGs to S. pneumoniae. Overall, the results highlight the potential of using the model to further our understanding of ecological and evolutionary forces driving antimicrobial resistance in oral microbiomes.

Antimicrobial Resistance Patterns in Patients with Vaginal Discharge: A 2019-2022 Analysis at the National Health Laboratory in Eritrea.

Background: Antimicrobial resistance poses a significant global threat to the treatment of bacterial infections, particularly in low- and middle-income regions such as Africa. This study is aimed at analyzing antimicrobial resistance patterns in vaginal swab samples from patients at the National Health Laboratory from 2019 to 2022. Methods: This retrospective study examined patient records from vaginal swab analyses performed at the National Health Laboratory between January 1, 2019, and December 31, 2022. Ethical approval was obtained from the Ministry of Health Research Ethical Approval and Clearance Committee on 15/02/2023. Results: Of the 622 samples, 83% underwent microbial isolation and identification. Citrobacter spp. exhibited high resistance (>43%) to antibiotics such as cephalexin, ceftazidime, nalidixic acid, ampicillin, gentamicin, and tetracycline. E. coli showed resistance rates of more than 50% to ampicillin, trimethoprim-sulfamethoxazole, and tetracycline. Klebsiella spp. and Proteus spp. exhibited resistance rates that exceeded 47% to specific antibiotics. Gram-positive bacteria have resistance rates of more than 49% with ampicillin, trimethoprim-sulfamethoxazole, tetracycline, oxacillin, vancomycin, and penicillin G. In particular, S. aureus demonstrated no resistance to rifampicin or clindamycin, while Streptococcus spp. showed 100% resistance to rifampicin and vancomycin. Several species, including Proteus species, Streptococcus spp., S. aureus, and Klebsiella spp. exhibited multidrug resistance. Conclusion: Most gram-negative bacteria displayed higher resistance of >45% to ampicillin, trimethoprim-sulfamethoxazole, and tetracycline. Among gram-positive bacteria, a higher resistance rate with ampicillin, trimethoprim-sulfamethoxazole, tetracycline, oxacillin, vancomycin, and penicillin G was recorded. S. aureus showed no resistance to rifampicin and clindamycin, and Strep. spp. indicated 100% resistance to rifampicin and vancomycin. This study highlights critical gaps and areas for further exploration. Expanding the spectrum of antibiotics tested and investigating underlying multidrug resistance mechanisms would provide a more comprehensive understanding of resistance patterns.

Synthesis of a tetralone derivative of ampicillin to control ampicillin-resistant Staphylococcusaureus.

Due to the rapid emergence of antibiotic resistant new bacterial strains and new infections, there is an urgent need for novel or newly modified and efficient alternatives of treatment. However, conventional antibiotics are still used in therapeutic settings but their efficacy is uncertain due to the rapid evolution of drug resistance. In the present study, we have synthesized a new derivative of conventional antibiotic ampicillin using SN2-type substitution reaction. NMR and mass analysis of the newly synthesized derivative of ampicillin confirmed it as ampicillin-bromo-methoxy-tetralone (ABMT). Importantly, ABMT is revealed to have efficient activity against Staphylococcus aureus (S. aureus) with a MIC value of 32 µg ml-1 while ampicillin was not effective, even at 64 µg ml-1 of concentration. Electron microscopy results confirmed the membrane-specific killing of S. aureus at 1 h of treatment. Additionally, molecular docking analysis revealed a strong binding affinity of ABMT with ß-lactamase via the formation of a closed compact bridge. Our findings, avail a new derivative of ampicillin that could be a potential alternative to fight ampicillin-resistant bacteria possibly by neutralizing the ß-lactamase action.

Protective effects of antibiotic resistant bacteria on susceptibles in biofilm: Influential factors, mechanism, and modeling.

In environmental biofilms, antibiotic-resistant bacteria facilitate the persistence of susceptible counterparts under antibiotic stresses, contributing to increased community-level resistance. However, there is a lack of quantitative understanding of this protective effect and its influential factors, hindering accurate risk assessment of biofilm resistance in diverse environment. This study isolated an opportunistic Escherichia coli pathogen from soil, and engineered it with plasmids conferring antibiotic resistance. Protective effects of the ampicillin resistant strain (AmpR) on their susceptible counterparts (AmpS) were observed in ampicillin-stress colony biofilms. The concentration of ampicillin delineated protective effects into 3 zones: continuous protection (<1 MIC of AmpS), initial AmpS/R dependent (1-8 MIC of AmpS), and ineffective (>8 MIC of AmpS). Intriguingly, Zone 2 exhibited a surprising "less is more" phenomenon tuned by the initial AmpS/R ratio, where biofilm with an initially lower AmpR (1:50 vs 50:1) harbored 30-90 % more AmpR after 24 h growth under antibiotic stress. Compared to AmpS, AmpR displayed superiority in adhesion, antibiotic degradation, motility, and quorum sensing, allowing them to preferentially colonize biofilm edge and areas with higher ampicillin. An agent-based model incorporating protective effects successfully simulated tempo-spatial dynamics of AmpR and AmpS influenced by antibiotic stress and initial AmpS/R. This study provides a holistic view on the pervasive but poorly understood protective effects in biofilm, enabling development of better risk assessment and precisely targeted control strategies of biofilm resistance in diverse environment.

[New awareness for zoonoses using the example of rat bite fever : Case report and literature review]. / Neue Achtsamkeit für Zoonosen am Beispiel Rattenbissfieber : Fallbericht und Literaturübersicht.

BACKGROUND: Rat bite fever is a rare but potentially fatal bacterial zoonosis. The symptoms can be unspecific, but severe sepsis can be associated with involvement of different organs. CASE REPORT: A 27-year-old homeless man presented with fever, suspected meningitis, acute renal failure, unclear skin lesions as well as joint problems and muscular pain. Bite wounds were not detected. Meningitis could be excluded after lumbar puncture, and there was no evidence of endocarditis as the cause of the skin lesions. After 72 h, growth of Streptobacillus moniliformis in blood cultures was detected. Clinical symptoms were compatible with the diagnosis of rat bite fever. Calculated antibiosis with ampicillin sulbactam and doxycycline led to regression of the symptoms. CONCLUSION: Rat bite fever poses a diagnostic challenge due unspecific symptoms, diverse differential diagnostic options, and challenging microbiological detection. Patient history is of the utmost importance. Due to the rarity of the disease, this case report is intended to raise awareness.

Listeria monocytogenes: the silent assassin.

Listeriosis is a foodborne infection in humans caused by Listeria monocytogenes. Consumption of contaminated food can lead to severe infection in vulnerable patients, that can be fatal. Clinical manifestations include sepsis and meningitis, and in pregnancy-associated infection, miscarriage and stillbirth. Diagnosis is confirmed by culture and identification of the pathogen from blood, cerebrospinal fluid, vaginal swab, placenta or amniotic fluid. Treatment regimens recommend amoxicillin, ampicillin or an aminoglycoside. Virulence factors mediate bacterial adhesion and invasion of gut epithelial cells. Other factors mediate biofilm formation and tolerance to low temperatures and high salt concentrations facilitating persistence and survival in the environment.

Prevalence and antimicrobial resistance of Enterobacteriaceae in the north of Kazakhstan.

Background: An increasing number of drugs are used each year in the treatment of small pets (cats and dogs), including medicines (cephalosporins and fluoroquinolones) used in human therapy. Aim: The purpose of this study was to isolate and explore the antibiotic resistance of opportunistic Enterobacteriaceae (Escherichia coli, Klebsiella, Proteus, Ci trobacter, Enterobacter) from cats and dogs, and to isolate resistance genes in the microorganisms. Methods: In 2021, 808 samples of biological material from small domestic animals were collected in veterinary clinics in Kostanay. From these, 210 microorganisms were isolated and identified. Results: A large majority of the strains sampled belonged to E. coli-149 (70.9%), Enterobacter-11 (5.2%), Klebsiella-28 (13.3%), Proteus-12 (5.7%) and 10 Citrobacter isolates (4.8%). In all isolates identified, antibiotic resistance/sensitivity was determined by disc-diffusion method to ampicillin, cefoxitin, gentamicin, levomycetin, tetracycline, ciprofloxacin, norfloxacin, ofloxacin, cefoperazone, cefpodoxime, streptomycin, kanamycin, doxycycline, gemifloxacin, nalidixic acid, furazolidone, furadonine, amoxicillin, and enrofloxacin. Conclusion: The study has demonstrated that the greatest number of Enterobacteriaceae were sensitive to the action of meropenem, which belongs to the group of beta-lactam antibiotics; resistance was demonstrated against tetracycline, doxycycline, ampicillin, amoxicillin, ofloxacin, and cefpodoxime. The most common genes encoding antimicrobial resistance were as follows: BlaTEM and OXA in 41 and 28 isolates, respectively, encoding resistance to beta-lactams; StrA and StrB in 45 and 48 isolates encoding aminoglycosides; and tetA and tetB in 43 and 28 isolates encoding tetracyclines. Obtained data demonstrate that uncontrolled and frequent use of beta-lactam and tetracycline antibacterials, in cats and dogs, results in the spread of genotypic resistance among micro-organisms of the family Enterobacteriaceae.

Antibacterial efficacy, mode of action, and safety of a novel nano-antibiotic against antibiotic-resistant Escherichia coli strains.

Globally rising antibiotic-resistant (AR) and multi-drug resistant (MDR) bacterial infections are of public health concern due to treatment failure with current antibiotics. Enterobacteria, particularly Escherichia coli, cause infections of surgical wound, bloodstream, and urinary tract, including pneumonia and sepsis. Herein, we tested in vitro antibacterial efficacy, mode of action (MoA), and safety of novel amino-functionalized silver nanoparticles (NH2-AgNP) against the AR bacteria. Two AR E. coli strains (i.e., ampicillin- and kanamycin-resistant E. coli), including a susceptible strain of E. coli DH5α, were tested for susceptibility to NH2-AgNP using Kirby-Bauer disk diffusion and standard growth assays. Dynamic light scattering (DLS) was used to determine cell debris and relative conductance was used as a measure of cell leakage, and results were confirmed with transmission electron microscopy (TEM). Multiple oxidative stress assays were used for in vitro safety evaluation of NH2-AgNP in human lung epithelial cells. Results showed that ampicillin and kanamycin did not inhibit growth in either AR bacterial strain with doses up to 160 µg/mL tested. NH2-AgNP exhibited broad-spectrum bactericidal activity, inhibiting the growth of all three bacterial strains at doses ≥1 µg/mL. DLS and TEM revealed cell debris formation and cell leakage upon NH2-AgNP treatment, suggesting two possible MoAs: electrostatic interactions followed by cell wall damage. Safety evaluation revealed NH2-AgNP as noncytotoxic and antioxidative to human lung epithelial cells. Taken together, these results suggest that NH2-AgNP may serve as an effective and safer bactericidal therapy against AR bacterial infections compared to common antibiotics.

Generalizability of machine learning in predicting antimicrobial resistance in E. coli: a multi-country case study in Africa.

BACKGROUND: Antimicrobial resistance (AMR) remains a significant global health threat particularly impacting low- and middle-income countries (LMICs). These regions often grapple with limited healthcare resources and access to advanced diagnostic tools. Consequently, there is a pressing need for innovative approaches that can enhance AMR surveillance and management. Machine learning (ML) though underutilized in these settings, presents a promising avenue. This study leverages ML models trained on whole-genome sequencing data from England, where such data is more readily available, to predict AMR in E. coli, targeting key antibiotics such as ciprofloxacin, ampicillin, and cefotaxime. A crucial part of our work involved the validation of these models using an independent dataset from Africa, specifically from Uganda, Nigeria, and Tanzania, to ascertain their applicability and effectiveness in LMICs. RESULTS: Model performance varied across antibiotics. The Support Vector Machine excelled in predicting ciprofloxacin resistance (87% accuracy, F1 Score: 0.57), Light Gradient Boosting Machine for cefotaxime (92% accuracy, F1 Score: 0.42), and Gradient Boosting for ampicillin (58% accuracy, F1 Score: 0.66). In validation with data from Africa, Logistic Regression showed high accuracy for ampicillin (94%, F1 Score: 0.97), while Random Forest and Light Gradient Boosting Machine were effective for ciprofloxacin (50% accuracy, F1 Score: 0.56) and cefotaxime (45% accuracy, F1 Score:0.54), respectively. Key mutations associated with AMR were identified for these antibiotics. CONCLUSION: As the threat of AMR continues to rise, the successful application of these models, particularly on genomic datasets from LMICs, signals a promising avenue for improving AMR prediction to support large AMR surveillance programs. This work thus not only expands our current understanding of the genetic underpinnings of AMR but also provides a robust methodological framework that can guide future research and applications in the fight against AMR.

Cell surface ß-lactamase recruitment: A facile selection to identify protein-protein interactions.

Protein-protein interactions (PPIs) are central to many cellular processes, and the identification of novel PPIs is a critical step in the discovery of protein therapeutics. Simple methods to identify naturally existing or laboratory evolved PPIs are therefore valuable research tools. We have developed a facile selection that links PPI-dependent ß-lactamase recruitment on the surface of Escherichia coli with resistance to ampicillin. Bacteria displaying a protein that forms a complex with a specific protein-ß-lactamase fusion are protected from ampicillin-dependent cell death. In contrast, bacteria that do not recruit ß-lactamase to the cell surface are killed by ampicillin. Given its simplicity and tunability, we anticipate this selection will be a valuable addition to the palette of methods for illuminating and interrogating PPIs.

Mesoporous silica nanospheres-mediated insecticide and antibiotics co-delivery system for synergizing insecticidal toxicity and reducing environmental risk of insecticide.

Mesoporous silica nanoparticles (MSNs) are efficient carriers of drugs, and are promising in developing novel pesticide formulations. The cotton aphids Aphis gossypii Glover is a world devastating insect pest. It has evolved high level resistance to various insecticides thus resulted in the application of higher doses of insecticides, which raised environmental risk. In this study, the MSNs based pesticide/antibiotic delivery system was constructed for co-delivery of ampicillin (Amp) and imidacloprid (IMI). The IMI@Amp@MSNs complexes have improved toxicity against cotton aphids, and reduced acute toxicity to zebrafish. From the 16S rDNA sequencing results, Amp@MSNs, prepared by loading ampicillin to the mesoporous of MSNs, greatly disturbed the gut community of cotton aphids. Then, the relative expression of at least 25 cytochrome P450 genes of A. gossypii was significantly suppressed, including CYP6CY19 and CYP6CY22, which were found to be associated with imidacloprid resistance by RNAi. The bioassay results indicated that the synergy ratio of ampicillin to imidacloprid was 1.6, while Amp@MSNs improved the toxicity of imidacloprid by 2.4-fold. In addition, IMI@Amp@MSNs significantly improved the penetration of imidacloprid, and contributed to the amount of imidacloprid delivered to A. gossypii increased 1.4-fold. Thus, through inhibiting the relative expression of cytochrome P450 genes and improving penetration of imidacloprid, the toxicity of IMI@Amp@MSNs was 6.0-fold higher than that of imidacloprid. The greenhouse experiments further demonstrated the enhanced insecticidal activity of IMI@Amp@MSNs to A. gossypii. Meanwhile, the LC50 of IMI@Amp@MSNs to zebrafish was 3.9-fold higher than that of IMI, and the EC50 for malformation was 2.8-fold higher than IMI, respectively, which indicated that the IMI@Amp@MSNs complexes significantly reduced the environmental risk of imidacloprid. These findings encouraged the development of pesticide/antibiotic co-delivery nanoparticles, which would benefit pesticide reduction and environmental safety.