Combating antibiotic resistance in a one health context: a plethora of frontiers

One of the most significant medical advancements of the 20th century was the discovery of antibiotics, which continue to play a vital tool in the treatment and prevention of diseases in humans and animals. However, the imprudent use of antibiotics in all fields of One-Health and concerns about antibiotic resistance among bacterial pathogens have raised interest in antibiotic use restrictions on a global scale. Despite the failure of conventional antimicrobial agents, only about 15 new antibiotics have been introduced clinically since year 2000 to date. Moreover, there has been reports of resistance to some of these new antibiotics. This has necessitated a need to search for alternative strategies to combat antimicrobial resistant pathogens. Thus, this review compiles and evaluates the approaches-natural compounds, phage treatment, and nanomaterials-that are being used and/or suggested as the potential substitutes for conventional antibiotics.

Recent developments of topoisomerase inhibitors: Clinical trials, emerging indications, novel molecules and global sales

The nucleic acid topoisomerases (TOP) are an evolutionary conserved mechanism to solve topological problems within DNA and RNA that have been historically well-established as a chemotherapeutic target. During investigation of trends within clinical trials, we have identified a very high number of clinical trials involving TOP inhibitors, prompting us to further evaluate the current status of this class of therapeutic agents. In total, we have identified 233 unique molecules with TOP-inhibiting activity. In this review, we provide an overview of the clinical drug development highlighting advances in current clinical uses and discussing novel drugs and indications under development. A wide range of bacterial infections, along with solid and hematologic neoplasms, represent the bulk of clinically approved indications. Negative ADR profile and drug resistance among the antibacterial TOP inhibitors and anthracycline-mediated cardiotoxicity in the antineoplastic TOP inhibitors are major points of concern, subject to continuous research efforts. Ongoing development continues to focus on bacterial infections and cancer; however, there is a degree of diversification in terms of novel drug classes and previously uncovered indications, such as glioblastoma multiforme or Clostridium difficile infections. Preclinical studies show potential in viral, protozoal, parasitic and fungal infections as well and suggest the emergence of a novel target, TOP IIIβ. We predict further growth and diversification of the field thanks to the large number of experimental TOP inhibitors emerging.

Mechanism of staphylococcal resistance to clinically relevant antibiotics

Staphylococcus aureus, a notorious pathogen with versatile virulence, poses a significant challenge to current antibiotic treatments due to its ability to develop resistance mechanisms against a variety of clinically relevant antibiotics. In this comprehensive review, we carefully dissect the resistance mechanisms employed by S. aureus against various antibiotics commonly used in clinical settings. The article navigates through intricate molecular pathways, elucidating the mechanisms by which S. aureus evades the therapeutic efficacy of antibiotics, such as β-lactams, vancomycin, daptomycin, linezolid, etc. Each antibiotic is scrutinised for its mechanism of action, impact on bacterial physiology, and the corresponding resistance strategies adopted by S. aureus. By synthesising the knowledge surrounding these resistance mechanisms, this review aims to serve as a comprehensive resource that provides a foundation for the development of innovative therapeutic strategies and alternative treatments for S. aureus infections. Understanding the evolving landscape of antibiotic resistance is imperative for devising effective countermeasures in the battle against this formidable pathogen.

Effect of single parenteral administration of marbofloxacin on bacterial load and selection of resistant Enterobacteriaceae in the fecal microbiota of healthy pigs

BACKGROUND

Antimicrobial resistance (AMR) is a global concern impacting both humans, animals and their environment. The use of oral antimicrobials in livestock, particularly in pigs, has been identified as a driver in the selection of AMR bacteria. The aim of the present study was to evaluate the effects of a single intramuscular (IM) dose of marbofloxacin (8 mg/kg) on Enterobacteriaceae and E. coli populations, as well as on fluoroquinolone resistance within the fecal microbiota of pigs. Twenty healthy pigs, 60-days old, were divided into two groups: a treated group (n = 13) and a control group (n = 7) and were monitored over a 28-day experimental period. Fecal samples were collected from all animals for the isolation of E. coli and Salmonella strains. The minimum inhibitory concentration (MIC) of marbofloxacin for the isolates recovered on MacConkey agar supplemented with 1 or 4 µg/mL of marbofloxacin and for some generic E. coli isolates (recovered from MacConkey agar not supplemented with marbofloxacin) was determined using the broth microdilution method. Genomic DNA was extracted from the confirmed bacterial strains and sequenced using the Sanger method to identify mutations in the quinolone resistance determining regions (QRDRs) of the gyrA and parC genes.

RESULTS

The single IM administration of marbofloxacin resulted in a significant decrease in Enterobacteriaceae and E. coli fecal populations from days 1 to 3 post- treatment. No Salmonella isolates were detected in either group, and no marbofloxacin-resistant E. coli isolates were identified. The MIC of the selected generic E. coli strains (n = 100) showed an increase to up to 0.5 µg/mL between days 1 and 3 post-treatment but remained below the clinical breakpoint of marbofloxacin resistance (4 µg/mL). Sequencing of these isolates revealed no mutations in gyrA and parC genes.

CONCLUSIONS

The present study showed that this dosing regimen of marbofloxacin significantly decreases the fecal shedding of Enterobacteriaceae and E. coli populations in pigs, while limiting the selection of marbofloxacin-resistant E. coli isolates. These findings warrant validation in sick pigs to support the selective use of this antibiotic solely in cases of clinical disease, thereby minimizing the reliance on conventional (metaphylactic) group treatments in pigs.

Dairy farm waste: A potential reservoir of diverse antibiotic resistance and virulence genes in aminoglycoside- and beta-lactam-resistant Escherichia coli in Gansu Province, China

Aminoglycosides (AGs) and beta-lactams are the most commonly used antimicrobials in animal settings, particularly on dairy farms. Dairy farm waste is an important reservoir of antibiotic resistance genes (ARGs) and virulence genes (VGs) in environmental Escherichia coli, which is an important indicator of environmental contamination and foodborne pathogen that potentially threaten human and animal health. In the present study, we aimed to characterize the ARGs and VGs in AG- and beta-lactam-resistant E. coli from dairy farm waste in Gansu Province, China. The dairy farm waste consisted of fecal (n = 265) and sewage (n = 54) samples processed using standard microbiological techniques and the Clinical & Laboratory Standards Institute guidelines. The total DNA of AG- and beta-lactam-resistant E. coli was extracted, and whole-genome sequencing (WGS) was performed using the Illumina NovaSeq platform and analyzed using various bioinformatics tools. In this study, among 84.3% (269/319) of the E. coli strains, 23.8% (64/269) were identified as AG- and beta-lactam-resistant E. coli. WGS analysis revealed a large pool of ARGs belonging to multiple classes such as AGs, beta-lactams, aminocoumarins, fluoroquinolones, macrolides, phenicol, tetracyclines, phosphonic acid, disinfecting and antiseptic agents, elfamycin, rifamycin, and multidrug resistance genes. Furthermore, virulome analysis of 64 E. coli strains revealed clinically important virulence factors associated with adherence, biofilm, invasion, auto-transportation, siderophores, secretion systems, toxins, anti-phagocytosis, quorum sensing, regulation, metabolism, and motility. We identified dairy farm feces and sewage waste as important reservoirs of antimicrobial resistance and virulence determinants in E. coli in Gansu, China, which can threaten human and animal health through ecological exposure and contamination of food and water. We recommend continuous large-scale surveillance in dairy farm settings to formulate protective guidelines for public health safety.

Characterization of infectious bacterial keratitis in Östergötland County, Sweden: a 10-year retrospective study

BACKGROUND

The aim of this study was to characterize bacterial species, aetiology and antibiotic susceptibility connected to bacterial keratitis infections in Östergötland, Sweden.

METHODS

Retrospective cross-sectional study based on electronic health records for the period 2010-2019. Records of patients diagnosed with infectious keratitis were screened for microbiology confirmed infectious bacterial keratitis. Bacterial species and their susceptibility to antibiotics were determined from microbiology test results.

RESULTS

One-hundred and ninety patients with lab culture-confirmed infectious bacterial keratitis were included in the analysis. The most frequently found bacterial species were coagulase-negative staphylococci (39%), Staphylococcus aureus (17%) and Cutibacterium acnes (10%). Pseudomonas spp. was the most frequently found Gram-negative bacterial species (7%). Contact lens wear and severely ill/blind eye were the top two aetiologies associated with bacterial keratitis, 22% of the patients with bacterial keratitis were also diagnosed with glaucoma. Most isolates, 157 out of 173, were susceptible to fluoroquinolones, and 145 out of 155 isolates were susceptible to chloramphenicol.

CONCLUSION

Our results revealed a positive rate of bacterial keratitis of 59% for the samples sent to the laboratory. There was a high susceptibility of the bacterial species to the recommended antibiotics. Our results indicate that it is likely that patients are receiving the correct treatment. Future studies are necessary to monitor changes in antibiotic susceptibility.

Is topical antibiotic use necessary to prevent surgical site infection following oculoplastic surgery?

PURPOSE

To assess whether oculoplastic surgeries can be performed without any topical and systemic antibiotics, in a "100% antibiotic free" fashion.

METHOD

We conducted a multicenter retrospective study between November 2017 and December 2022. Patients who underwent an oculoplastic procedure were screened. Patients who received preoperative or postoperative systemic antibiotics were excluded. Intraoperative IV antibiotics were allowed. Patients were divided into two groups: those who were treated with local antibiotics ointments (LATB group) and those who were treated without local antibiotics ointments (LATB free group) postoperatively. The primary outcome was the incidence of surgical site infections (SSI). The relationship between the use of local antibiotics and the occurrence of SSI was assessed using Fisher's exact test. The alpha risk was set to 5% and two-tailed tests were used.

RESULTS

Among the 947 procedures included, 617 were included in the LATB group and 330 in the LATB free group. 853 and 80 procedures were classified Altemeier class 1 (clean) and class 2 (clean-contaminated) surgeries, respectively. Overall, 310 (32.73%) procedures were performed without any systemic nor topical antibiotics (100% antibiotic free fashion). SSI occured in four (4/617; 0.65%) and five (5/330; 1.52%) procedures in the LATB and LATB free group respectively, without any statistical difference between the groups (p = 0.290). A subgroup analysis was carried out by excluding the procedures performed under prophylactic intraoperative intravenous antibiotics and did not reveal any statistical difference between the two groups (p = 0.144). All SSI patients were treated with systemic antibiotics with favorable outcomes. Postoperative wound dehiscence was the only risk factor associated with postoperative SSI (p = 0.002).

CONCLUSION

This study suggests that performing a "100% antibiotic free" oculoplastic surgery without systemic and topical antibiotics is reasonable in Altemeier class 1 and class 2 procedures.

Relationship Between Fluoroquinolone Resistance and Mutations in the Quinolone Resistance-Determining Region in Corynebacterium macginleyi

Purpose

The purpose of this study was to investigate the bacterial composition in the conjunctiva and to determine the relationship between fluoroquinolone resistance and mutations in the quinolone resistance-determining region (QRDR) in Corynebacterium macginleyi (C. macginleyi).

Methods

Bacteria isolated from conjunctival swabs of patients awaiting ophthalmic surgery or patients with presumed keratoconjunctivitis were included in this study. For C. macginleyi isolates from 49 samples, the minimum inhibitory concentrations (MICs) of second- to fourth-generation fluoroquinolones were determined by broth microdilution. Additionally, we determined the sequence of the QRDR in the gyrA gene of C. macginleyi-positive isolates by direct sequencing and investigated the relationship between the QRDR mutation and the MICs of fluoroquinolones for C. macginleyi.

Results

Among 423 eyes of 296 preoperative patients who underwent conjunctival culture testing, 105 eyes of 89 patients were culture-positive, and among 148 eyes of 147 patients with keratoconjunctivitis, 55 eyes of 54 patients were culture-positive. C. macginleyi accounted for the largest proportion of cultured organisms (34.8%). C. macginleyi-positive isolates were found in 45 eyes of 37 preoperative patients and in 4 eyes of 4 patients with keratoconjunctivitis. Direct sequencing revealed that 91.8% of C. macginleyi-positive isolates had amino acid mutations in the QRDR and 95.5% of mutations were found at Ser-87 and Asp-91. Isolates harboring double mutations at Ser-87 and Asp-91 were resistant to second- to fourth-generation fluoroquinolones. One isolate with double mutations at Ser-87 and Ala-88 but no mutation in Asp-91 showed intermediate susceptibility to moxifloxacin, a fourth-generation fluoroquinolone.

Conclusions

C. macginleyi isolated from conjunctiva harboring QRDR amino acid mutations were resistant to second- to fourth-generation fluoroquinolones.

Mutations in the efflux regulator gene oqxR provide a simple genetic switch for antimicrobial resistance in Klebsiella pneumoniae

Klebsiella pneumoniae is a pathogen of major concern in the global rise of antimicrobial resistance and has been implicated as a reservoir for the transfer of resistance genes between species. The upregulation of efflux pumps is a particularly concerning mechanism of resistance acquisition as, in many instances, a single point mutation can simultaneously provide resistance to a range of antimicrobials and biocides. The current study investigated mutations in oqxR, which encodes a negative regulator of the RND-family efflux pump genes, oqxAB, natively found in the chromosome of K. pneumoniae. Resistant mutants in four K. pneumoniae strains (KP6870155, NTUH-K2044, SGH10, and ATCC43816) were selected from single exposures to 30 µg/mL chloramphenicol and 12 mutants were selected for whole genome sequencing to identify mutations associated with resistance. Resistant mutants generated by single exposures to chloramphenicol, tetracycline, or ciprofloxacin at ≥4 X MIC were replica plated onto all three antibiotics to observe simultaneous cross-resistance to all compounds, indicative of a multidrug resistance phenotype. A variety of novel mutations, including single point mutations, deletions, and insertions, were found to disrupt oqxR leading to significant and simultaneous increases in resistance to chloramphenicol, tetracycline, and ciprofloxacin. The oqxAB-oqxR locus has been mobilized and dispersed on plasmids in many Enterobacteriaceae species and the diversity of these loci was examined to evaluate the evolutionary pressures acting on these genes. Comparison of the promoter regions of oqxR in plasmid-borne copies of the oqxR-oqxAB operon indicated that some constructs may produce truncated versions of the oqxR transcript, which may impact on oqxAB regulation and expression. In some instances, co-carriage of chromosomal and plasmid encoded oqxAB-oqxR was found in K. pneumoniae, implying that there is selective pressure to maintain and expand the efflux pump. Given that OqxR is a repressor of oqxAB, any mutation affecting its expression or function can lead to multidrug resistance. This is in contrast to antibiotic target site mutations that must occur in limited sequence space to be effective and not impact the fitness of the cell. Therefore, oqxR may act as a simple genetic switch to facilitate resistance via OqxAB mediated efflux.

Interplay between Amino Acid Substitution in GyrA and QnrB19: Elevating Fluoroquinolone Resistance in Salmonella Typhimurium

Globally, there have been increasing reports of antimicrobial resistance in nontyphoidal Salmonella (NTS), which can develop into severe and potentially life-threatening diarrhea. This study focuses on the synergistic effects of DNA gyrase mutations and plasmid-mediated quinolone resistance (PMQR) genes, specifically qnrB19, on fluoroquinolone (FQ) resistance in Salmonella Typhimurium. By utilizing recombinant mutants, GyrAS83F and GyrAD87N, and QnrB19's, we discovered a significant increase in fluoroquinolones resistance when QnrB19 is present. Specifically, ciprofloxacin and moxifloxacin's inhibitory concentrations rose 10- and 8-fold, respectively. QnrB19 was found to enhance the resistance capacity of mutant DNA gyrases, leading to high-level FQ resistance. Additionally, we observed that the ratio of QnrB19 to DNA gyrase played a critical role in determining whether QnrB19 could protect DNA gyrase against FQ inhibition. Our findings underscore the critical need to understand these resistance mechanisms, as their coexistence enables bacteria to withstand therapeutic FQ levels, posing a significant challenge to treatment efficacy.

Role of therapeutic drug monitoring in the treatment of multi-drug resistant tuberculosis

Tuberculosis (TB) is a leading cause of mortality worldwide, and resistance to anti-tuberculosis drugs is a challenge to effective treatment. Multi-drug resistant TB (MDR-TB) can be difficult to treat, requiring long durations of therapy and the use of second line drugs, increasing a patient's risk for toxicities and treatment failure. Given the challenges treating MDR-TB, clinicians can improve the likelihood of successful outcomes by utilizing therapeutic drug monitoring (TDM). TDM is a clinical technique that utilizes measured drug concentrations from the patient to adjust therapy, increasing likelihood of therapeutic drug concentrations while minimizing the risk of toxic drug concentrations. This review paper provides an overview of the TDM process, pharmacokinetic parameters for MDR-TB drugs, and recommendations for dose adjustments following TDM.

Navigating fluoroquinolone resistance in Gram-negative bacteria: a comprehensive evaluation

Since the introduction of quinolone and fluoroquinolone antibiotics to treat bacterial infections in the 1960s, there has been a pronounced increase in the number of bacterial species that have developed resistance to fluoroquinolone treatment. In 2017, the World Health Organization established a priority list of the most critical Gram-negative resistant pathogens. These included Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli. In the last three decades, investigations into the mechanisms of fluoroquinolone resistance have revealed that mutations in the target enzymes of fluoroquinolones, DNA gyrase or topoisomerase IV, are the most prevalent mechanism conferring high levels of resistance. Alterations to porins and efflux pumps that facilitate fluoroquinolone permeation and extrusion across the bacterial cell membrane also contribute to the development of resistance. However, there is a growing observation of novel mutants with newer generations of fluoroquinolones, highlighting the need for novel treatments. Currently, steady progress has been made in the development of novel antimicrobial agents that target DNA gyrase or topoisomerase IV through different avenues than current fluoroquinolones to prevent target-mediated resistance. Therefore, an updated review of the current understanding of fluoroquinolone resistance within the literature is imperative to aid in future investigations.

Wide distribution of plasmid mediated quinolone resistance gene, qnrS, among Salmonella spp. isolated from canal water in Thailand

AIMS

This research focused on assessing the prevalence of plasmid-mediated quinolone resistance (PMQR) determinants and antimicrobial susceptibility in Salmonella strains isolated from Thai canal water.

METHODS AND RESULTS

From 2016 to 2020, 333 water samples were collected from six canals across Bangkok, Thailand. Salmonella spp. was isolated, PMQR genes were detected through polymerase chain reactions, and the antimicrobial susceptibility was examined using the disk diffusion method. The results indicated a 92.2% prevalence of Salmonella spp. in canal water, being serogroups B and C the most frequently detected. Overall, 35.3% of isolates harbored PMQR genes, being qnrS the most prevalent gene (97.2%, n = 137/141). Other PMQR genes, including qnrB, qnrD, oqxAB, and aac(6')-Ib-cr, were detected. Notably, six isolates harbored multiple PMQR genes. Furthermore, 9.3% and 3.8% of the overall isolates were resistant to nalidixic acid (NAL) and ciprofloxacin (CIP), respectively. PMQR-positive isolates showed higher rates of non-susceptibility to both NAL (48.2%, n = 68/141) and CIP (92.2%, n = 130/141) compared to PMQR-negative isolates (NAL: 8.9%, n = 23/258; CIP: 11.2%, n = 30/258).

CONCLUSIONS

The high prevalence of Salmonella spp., significant PMQR-positive, and reduced susceptibility isolates in canal water is of public health concern in Bangkok.

Decoding antimicrobial resistance: unraveling molecular mechanisms and targeted strategies

Antimicrobial resistance poses a significant global health threat, necessitating innovative approaches for combatting it. This review explores various mechanisms of antimicrobial resistance observed in various strains of bacteria. We examine various strategies, including antimicrobial peptides (AMPs), novel antimicrobial materials, drug delivery systems, vaccines, antibody therapies, and non-traditional antibiotic treatments. Through a comprehensive literature review, the efficacy and challenges of these strategies are evaluated. Findings reveal the potential of AMPs in combating resistance due to their unique mechanisms and lower propensity for resistance development. Additionally, novel drug delivery systems, such as nanoparticles, show promise in enhancing antibiotic efficacy and overcoming resistance mechanisms. Vaccines and antibody therapies offer preventive measures, although challenges exist in their development. Non-traditional antibiotic treatments, including CRISPR-Cas systems, present alternative approaches to combat resistance. Overall, this review underscores the importance of multifaceted strategies and coordinated global efforts to address antimicrobial resistance effectively.

Antibiotic Coordination Frameworks against Antibiotic Resistance: How to Involve Students through Experimental Practices in the Search for Solutions to Public Health Problems

For decades, multiple varieties of antibiotics have been successfully used for therapeutic purposes. Nevertheless, antibiotic resistance is currently one of the major threats to global health. This work presents an innovative laboratory practice carried out in an inorganic medicinal chemistry course within the Degrees of Pharmacy and Biochemistry for undergraduate students. This experiment includes three classes of 2 h each. The first class consisted of the mechanochemical synthesis of an antibiotic coordination framework (ACF) using a known antibiotic (nalidixic acid) and zinc as the ligand. The prepared Zn-nalidixic acid ACF (Zn-ACF) was obtained in up to 82% yield with high purity. On the second day, the synthesized Zn-ACF was characterized by Fourier-transform infrared spectroscopy (FTIR) and powder X-ray diffraction (PXRD). Finally, during the last class, the antimicrobial activity was tested against Escherichia coli by the well diffusion method. The students verified the higher antimicrobial activity of Zn-ACF compared to nalidixic acid, proving that small changes in the chemical structure can result in great biological differences. In the end, the students presented their results in a poster format, encouraging the development of their soft skills and scientific results communication and dissemination. In the future, it is expected that such a laboratory experiment at the interface between medicinal chemistry, microbiology, analytical techniques, public health, and pharmacology will lead to the development and implementation of some service-learning practices and will serve as a model to look at for other courses and institutions.

Occurrence and molecular characteristics of antimicrobial resistance, virulence factors, and extended-spectrum β-lactamase (ESBL) producing Salmonella enterica and Escherichia coli isolated from the retail produce commodities in Bangkok, Thailand

The incidence of antimicrobial resistance (AMR) in the environment is often overlooked and leads to serious health threats under the One Health paradigm. Infection with extended-spectrum β-lactamase (ESBL) producing bacteria in humans and animals has been widely examined, with the mode of transmission routes such as food, water, and contact with a contaminated environment. The purpose of this study was to determine the occurrence and molecular characteristics of resistant Salmonella enterica (S. enterica) (n = 59) and Escherichia coli (E. coli) (n = 392) isolated from produce commodities collected from fresh markets and supermarkets in Bangkok, Thailand. In this study, the S. enterica isolates exhibited the highest prevalence of resistance to tetracycline (11.9%) and streptomycin (8.5%), while the E. coli isolates were predominantly resistant to tetracycline (22.5%), ampicillin (21.4%), and sulfamethoxazole (11.5%). Among isolates of S. enterica (6.8%) and E. coli (15.3%) were determined as multidrug resistant (MDR). The prevalence of ESBL-producing isolates was 5.1% and 1.0% in S. enterica and E. coli, respectively. A minority of S. enterica isolates, where a single isolate exclusively carried blaCTX-M-55 (n = 1), and another isolate harbored both blaCTX-M-55 and blaTEM-1 (n = 1); similarly, a minority of E. coli isolates contained blaCTX-M-55 (n = 2) and blaCTX-M-15 (n = 1). QnrS (11.9%) and blaTEM (20.2%) were the most common resistant genes found in S. enterica and E. coli, respectively. Nine isolates resistant to ciprofloxacin contained point mutations in gyrA and parC. In addition, the odds of resistance to tetracycline among isolates of S. enterica were positively associated with the co-occurrence of ampicillin resistance and the presence of tetB (P = 0.001), while the E. coli isolates were positively associated with ampicillin resistance, streptomycin resistance, and the presence of tetA (P < 0.0001) in this study. In summary, these findings demonstrate that fresh vegetables and fruits, such as cucumbers and tomatoes, can serve as an important source of foodborne AMR S. enterica and E. coli in the greater Bangkok area, especially given the popularity of these fresh commodities in Thai cuisine.

Oral Antibiotics Alone versus Oral Antibiotics Combined with Mechanical Bowel Preparation for Elective Colorectal Surgery: A Propensity Score-Matching Re-Analysis of the iCral 2 and 3 Prospective Cohorts

The evidence regarding the role of oral antibiotics alone (oA) or combined with mechanical bowel preparation (MoABP) for elective colorectal surgery remains controversial. A prospective database of 8359 colorectal resections gathered over a 32-month period from 78 Italian surgical units (the iCral 2 and 3 studies), reporting patient-, disease-, and procedure-related variables together with 60-day adverse events, was re-analyzed to identify a subgroup of 1013 cases (12.1%) that received either oA or MoABP. This dataset was analyzed using a 1:1 propensity score-matching model including 20 covariates. Two well-balanced groups of 243 patients each were obtained: group A (oA) and group B (MoABP). The primary endpoints were anastomotic leakage (AL) and surgical site infection (SSI) rates. Group A vs. group B showed a significantly higher AL risk [14 (5.8%) vs. 6 (2.5%) events; OR: 3.77; 95%CI: 1.22-11.67; p = 0.021], while no significant difference was recorded between the two groups regarding SSIs. These results strongly support the use of MoABP for elective colorectal resections.

Targeting Iron - Respiratory Reciprocity Promotes Bacterial Death

Discovering new bacterial signaling pathways offers unique antibiotic strategies. Here, through an unbiased resistance screen of 3,884 gene knockout strains, we uncovered a previously unknown non-lytic bactericidal mechanism that sequentially couples three transporters and downstream transcription to lethally suppress respiration of the highly virulent P. aeruginosa strain PA14 - one of three species on the WHO's 'Priority 1: Critical' list. By targeting outer membrane YaiW, cationic lacritin peptide 'N-104' translocates into the periplasm where it ligates outer loops 4 and 2 of the inner membrane transporters FeoB and PotH, respectively, to suppress both ferrous iron and polyamine uptake. This broadly shuts down transcription of many biofilm-associated genes, including ferrous iron-dependent TauD and ExbB1. The mechanism is innate to the surface of the eye and is enhanced by synergistic coupling with thrombin peptide GKY20. This is the first example of an inhibitor of multiple bacterial transporters.

Antimicrobial peptides: An alternative to traditional antibiotics

As antibiotic-resistant bacteria and genes continue to emerge, the identification of effective alternatives to traditional antibiotics has become a pressing issue. Antimicrobial peptides are favored for their safety, low residue, and low resistance properties, and their unique antimicrobial mechanisms show significant potential in combating antibiotic resistance. However, the high production cost and weak activity of antimicrobial peptides limit their application. Moreover, traditional laboratory methods for identifying and designing new antimicrobial peptides are time-consuming and labor-intensive, hindering their development. Currently, novel technologies, such as artificial intelligence (AI) are being employed to develop and design new antimicrobial peptide resources, offering new opportunities for the advancement of antimicrobial peptides. This article summarizes the basic characteristics and antimicrobial mechanisms of antimicrobial peptides, as well as their advantages and limitations, and explores the application of AI in antimicrobial peptides prediction amd design. This highlights the crucial role of AI in enhancing the efficiency of antimicrobial peptide research and provides a reference for antimicrobial drug development.

N4-Substituted Piperazinyl Norfloxacin Derivatives with Broad-Spectrum Activity and Multiple Mechanisms on Gyrase, Topoisomerase IV, and Bacterial Cell Wall Synthesis

Fluoroquinolones are an important class of antibiotics with broad-spectrum antibacterial and antitubercular activity. Here, we describe the design and synthesis of a series of 38 N4-substituted piperazinyl norfloxacin derivatives. Their activity and mechanism of action were characterized using in silico, in vitro, and in vivo approaches. Several compounds displayed interesting activities against both Gram-negative and Gram-positive bacteria, and few displayed antimycobacterial activity, whereby some were as potent as norfloxacin and ciprofloxacin. Molecular docking experiments suggested that the new derivatives inhibit both DNA gyrase and DNA topoisomerase IV in a similar manner as norfloxacin. Selecting the most promising candidates for experimental mode of action analysis, we confirmed DNA gyrase and topoisomerase IV as targets of all tested compounds using enzymatic in vitro assays. Phenotypic analysis of both Escherichia coli and Bacillus subtilis confirmed a typical gyrase inhibition phenotype for all of the tested compounds. Assessment of possible additional targets revealed three compounds with unique effects on the B. subtilis cell wall synthesis machinery, suggesting that they may have an additional target in this pathway. Comparison with known cell wall synthesis inhibitors showed that the new compounds elicit a distinct and, so far, unique phenotype, suggesting that they act differently from known cell wall synthesis inhibitors. Interestingly, our phenotypic analysis revealed that both norfloxacin and ciprofloxacin displayed additional cellular effects as well, which may be indicative of the so far unknown additional mechanisms of fluoroquinolones.

Rational design, synthesis, molecular modeling, biological activity, and mechanism of action of polypharmacological norfloxacin hydroxamic acid derivatives

Fluoroquinolones are broad-spectrum antibiotics that target gyrase and topoisomerase IV, involved in DNA compaction and segregation. We synthesized 28 novel norfloxacin hydroxamic acid derivatives with additional metal-chelating and hydrophobic pharmacophores, designed to enable interactions with additional drug targets. Several compounds showed equal or better activity than norfloxacin against Gram-positive, Gram-negative, and mycobacteria, with MICs as low as 0.18 μM. The most interesting derivatives were selected for in silico, in vitro, and in vivo mode of action studies. Molecular docking, enzyme inhibition, and bacterial cytological profiling confirmed inhibition of gyrase and topoisomerase IV for all except two tested derivatives (10f and 11f). Further phenotypic analysis revealed polypharmacological effects on peptidoglycan synthesis for four derivatives (16a, 17a, 17b, 20b). Interestingly, compounds 17a, 17b, and 20b, showed never seen before effects on cell wall synthetic enzymes, including MreB, MurG, and PonA, suggesting a novel mechanism of action, possibly impairing the lipid II cycle.

The Impact of Substitutions at Positions 1 and 8 of Fluoroquinolones on the Activity Against Mutant DNA Gyrases of Salmonella Typhimurium

Although many drug-resistant nontyphoidal Salmonella (NTS) infections are reported globally, their treatment is challenging owing to the ineffectiveness of the currently available antimicrobial drugs against resistant bacteria. It is therefore essential to discover novel antimicrobial drugs for the management of these infections. In this study, we report high inhibitory activities of the novel fluoroquinolones (FQs; WQ-3810 and WQ-3334) with substitutions at positions R-1 by 6-amino-3,5-difluoropyridine-2-yl and R-8 by methyl group or bromine, respectively, against wild-type and mutant DNA gyrases of Salmonella Typhimurium. The inhibitory activities of these FQs were assessed against seven amino acid substitutions in DNA gyrases conferring FQ resistance to S. Typhimurium, including high-level resistant mutants, Ser83Ile and Ser83Phe-Asp87Asn by in vitro DNA supercoiling assay. Drug concentrations of WQ compounds with 6-amino-3,5-difluoropyridine-2-yl that suppressed DNA supercoiling by 50% (IC50) were found to be ∼150-fold lower than ciprofloxacin against DNA gyrase with double amino acid substitutions. Our findings highlight the importance of the chemical structure of an FQ drug on its antimicrobial activity. Particularly, the presence of 6-amino-3,5-difluoropyridine-2-yl at R-1 and either methyl group or bromine at R-8 of WQ-3810 and WQ-3334, respectively, was associated with improved antimicrobial activity. Therefore, WQ-3810 and WQ-3334 are promising candidates for use in the treatment of patients infected by FQ-resistant Salmonella spp.

Exploring Alternative Treatment Choices for Multidrug-Resistant Clinical Strains of Helicobacter pylori in Mongolia

Helicobacter pylori is a pathogen related to severe diseases such as gastric cancer; because of rising antimicrobial-resistant strains, failure to eradicate H. pylori with antibiotics has increased worldwide. Multidrug-resistant H. pylori and gastric cancer is common in Mongolia; therefore, we aimed to explore alternative antimicrobial treatments and the genomes of resistant strains in this country. A total of 361 H. pylori strains isolated from patients in Mongolia were considered. Minimal inhibitory concentrations for two fluoroquinolones (ciprofloxacin and moxifloxacin), rifabutin, and furazolidone were determined via two-fold agar dilution. Genomic mutations in antibiotic-resistant strains were identified by next-generation sequencing using the Illumina Miseq platform and compared with genes from a reference H. pylori strain (26695). The resistance rate of H. pylori strains to quinolones was high (44% to ciprofloxacin and 42% to moxifloxacin), and resistance to rifabutin was low (0.5%); none were resistant to furazolidone. Most quinolone-resistant strains possessed gyrA gene mutations causing amino acid changes (e.g., N87K, A88P, and D91G/Y/N). While one rifabutin-resistant strain had amino acid-substituting mutations in rpoB (D530N and R701C), the other had three novel rpoB mutations; both rifabutin-resistant strains were sensitive to furazolidone. Overall, our findings suggest that rifabutin and/or furazolidone may be an alternative, effective H. pylori treatment in patients who have failed to respond to other treatment regimens.

Occurrence and temporal distribution of extended-spectrum β-lactamase-producing Escherichia coli in clams from the Central Adriatic, Italy

The spread of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli is a major public health issue. Bivalves are filter-feeder animals capable of bioaccumulating the microorganisms present in water. This physiological characteristic makes them both good indicators of environmental contamination and possible carriers of pathogenic bacteria, including those resistant to antimicrobials. The aim of this study was to investigate the occurrence of ESBL-producing E. coli in clams (n = 308) collected from harvesting areas of the Central Adriatic Sea between 2018 and 2019. ESBL- /class C β-lactamase (AmpC)- producing E. coli and Escherichia spp. were isolated by streaking over the surface of MacConkey agar plates supplemented with cefotaxime enriched broths of the initial shellfish suspension. E. coli and Escherichia spp. resistant to cefotaxime were screened for ESBL production by using the double disk synergy test. Susceptibility to different antimicrobials and confirmation of ESBL-production were determined by the minimum inhibitory concentration (MIC) test. Isolates were further characterized by whole genome sequencing (WGS) and bioinformatic analysis of genomes with different tools. Overall, ESBL-producing E. coli were isolated from 3% of the samples. Of 13 ESBL- and ESBL-/AmpC-producing Escherichia spp. (n = 11 E. coli, n = 1 E. marmotae, n = 1 E. ruysiae) isolates, 13 were resistant to ampicillin and cefotaxime, 9 to sulfamethoxazole, 6 to tetracycline and nalidixic acid, 4 to trimethoprim, and 3 to ceftazidime, cefoxitin, ciprofloxacin, and chloramphenicol. Moreover, the majority (8/11) of the ESBL-producing E. coli isolates were multidrug-resistant. WGS showed that the isolates predominantly carried the blaCTX-M-15 gene (3/11) and blaCTX-M-14 and blaCTX-M-1 (2/11 each). The AmpC β-lactamase CMY-2 was found in two isolates. Phylogroup A was the most prevalent (5/11), followed by phylogroups D (4/11), F (1/11), and B2 (1/11). Ten different sequence types (STs) were identified. Occurrence at sampling sites ranged between 0 and 27%. To identify associations between the occurrence of ESBL-producing E. coli and E. coli levels, samples were divided into two groups, with E. coli at >230 MPN/100 g and E. coli at ≤230 MPN/100 g. ESBL-producing E. coli isolates were significantly more commonly recovered in samples with higher E. coli levels (14%) than in those with lower levels of E. coli (2%). Moreover, the majority (3/4) of the potentially pathogenic strains were isolated in samples with higher E. coli levels. These findings provided evidence for the bacterial indicator of fecal contamination, E. coli, as an index organism for ESBL-producing E. coli isolates in bivalves.

Protective effects of royal jelly and Echinacea against moxifloxacin-induced renal and hepatic injury in rats

Antibiotic use, especially fluoroquinolones, has been linked to extensive renal and hepatic injury thus inflicts a considerable health problem. Fifty rats were allocated into five groups (n = 10). Group 1 represented the normal-control group. Group 2 received moxifloxacin only (MOX; 8 mg/kg/day, i.p.) for seven days and represented the MOX-control group. Groups 3, 4, and 5 received MOX for seven days accompanied by royal jelly (RJ; 100 mg/kg/day, p.o.), Echinacea (ECH; 40 mg/kg/day, p.o.), and a combination of both at the aforementioned doses respectively for 30 days. All groups were investigated for renal and hepatic function tests. Renal tissue content of kidney injury molecule-1 (KIM-1) along with renal and hepatic tissue contents of reduced glutathione (GSH) and malondialdehyde (MDA) were assessed for all groups. Histopathological examination was performed followed by immunohistochemical staining for caspase-3 in renal and hepatic tissues. MOX administration resulted in significant renal and hepatic damage. RJ and ECH significantly improved the serum parameters of renal and hepatic functions along with increasing GSH and decreasing MDA in renal and hepatic tissues. Renal contents of KIM-1 were also reduced. Moreover, RJ, ECH, and their combination amended MOX-induced histopathological changes and significantly reduced caspase-3 immunohistochemical staining in both renal and hepatic tissues. The current study is the first to elucidate the effect of RJ, ECH, and their combination against MOX-induced renal and hepatic injury in rats. The study suggests that these protective effects are mainly via the reduction of oxidative stress induced by MOX administration.

Inoculum-Based Dosing: A Novel Concept for Combining Time with Concentration-Dependent Antibiotics to Optimize Clinical and Microbiological Outcomes in Severe Gram Negative Sepsis

Certain classes of antibiotics show "concentration dependent" antimicrobial activity; higher concentrations result in increased bacterial killing rates, in contrast to "time dependent antibiotics", which show antimicrobial activity that depends on the time that antibiotic concentrations remain above the MIC. Aminoglycosides and fluoroquinolones are still widely used concentration-dependent antibiotics. These antibiotics are not hydrolyzed by beta-lactamases and are less sensitive to the inoculum effect, which can be defined as an increased MIC for the antibiotic in the presence of a relatively higher bacterial load (inoculum). In addition, they possess a relatively long Post-Antibiotic Effect (PAE), which can be defined as the absence of bacterial growth when antibiotic concentrations fall below the MIC. These characteristics make them interesting complementary antibiotics in the management of Multi-Drug Resistant (MDR) bacteria and/or (neutropenic) patients with severe sepsis. Global surveillance studies have shown that up to 90% of MDR Gram-negative bacteria still remain susceptible to aminoglycosides, depending on the susceptibility breakpoint (e.g., CLSI or EUCAST) being applied. This percentage is notably lower for fluoroquinolones but depends on the region, type of organism, and mechanism of resistance involved. Daily (high-dose) dosing of aminoglycosides for less than one week has been associated with significantly less nephro/oto toxicity and improved target attainment. Furthermore, higher-than-conventional dosing of fluoroquinolones has been linked to improved clinical outcomes. Beta-lactam antibiotics are the recommended backbone of therapy for severe sepsis. Since these antibiotics are time-dependent, the addition of a second concentration-dependent antibiotic could serve to quickly lower the bacterial inoculum, create PAE, and reduce Penicillin-Binding Protein (PBP) expression. Inadequate antibiotic levels at the site of infection, especially in the presence of high inoculum infections, have been shown to be important risk factors for inadequate resistance suppression and therapeutic failure. Therefore, in the early phase of severe sepsis, effort should be made to optimize the dose and quickly lower the inoculum. In this article, the authors propose a novel concept of "Inoculum Based Dosing" in which the decision for antibiotic dosing regimens and/or combination therapy is not only based on the PK parameters of the patient, but also on the presumed inoculum size. Once the inoculum has been lowered, indirectly reflected by clinical improvement, treatment simplification should be considered to further treat the infection.

Fluoroquinolone-Based Organic Salts (GUMBOS) with Antibacterial Potential

Antimicrobial resistance is a silent pandemic considered a public health concern worldwide. Strategic therapies are needed to replace antibacterials that are now ineffective. One approach entails the use of well-known antibacterials along with adjuvants that possess non-antibiotic properties but can extend the lifespan and enhance the effectiveness of the treatment, while also improving the suppression of resistance. In this regard, a group of uniform materials based on organic salts (GUMBOS) presents an alternative to this problem allowing the combination of antibacterials with adjuvants. Fluoroquinolones are a family of antibacterials used to treat respiratory and urinary tract infections with broad-spectrum activity. Ciprofloxacin and moxifloxacin-based GUMBOS were synthesized via anion exchange reactions with lithium and sodium salts. Structural characterization, thermal stability and octanol/water partition ratios were evaluated. The antibacterial profiles of most GUMBOS were comparable to their cationic counterparts when tested against Gram-positive S. aureus and Gram-negative E. coli, except for deoxycholate anion, which demonstrated the least effective antibacterial activity. Additionally, some GUMBOS were less cytotoxic to L929 fibroblast cells and non-hemolytic to red blood cells. Therefore, these agents exhibit promise as an alternative approach to combining drugs for treating infections caused by resistant bacteria.

A Fluorescence-Based, T5 Exonuclease-Amplified DNA Cleavage Assay for Discovering Bacterial DNA Gyrase Poisons

Fluoroquinolones (FQs) are potent antibiotics of clinical significance, known for their unique mechanism of action as gyrase poisons, which stabilize gyrase-DNA cleavage complexes and convert gyrase into a DNA-damaging machinery. Unfortunately, FQ resistance has emerged, and these antibiotics can cause severe side effects. Therefore, discovering novel gyrase poisons with different chemical scaffolds is essential. The challenge lies in efficiently identifying them from compound libraries containing thousands or millions of drug-like compounds, as high-throughput screening (HTS) assays are currently unavailable. Here we report a novel fluorescence-based, T5 exonuclease-amplified DNA cleavage assay for gyrase poison discovery. This assay capitalizes on recent findings showing that multiple gyrase molecules can simultaneously bind to a plasmid DNA molecule, forming multiple gyrase-DNA cleavage complexes on the same plasmid. These gyrase-DNA cleavage complexes, stabilized by a gyrase poison, can be captured using sarkosyl. Proteinase K digestion results in producing small DNA fragments. T5 exonuclease, selectively digesting linear and nicked DNA, can fully digest the fragmented linear DNA molecules and, thus, "amplify" the decrease in fluorescence signal of the DNA cleavage products after SYBR Green staining. This fluorescence-based, T5 exonuclease-amplified DNA cleavage HTS assay is validated using a 50-compound library, making it suitable for screening large compound libraries.

Molecular Characterization and Mutational Analysis of Clarithromycin- and Levofloxacin-Resistance Genes in Helicobacter pylori from Gastric Biopsies in Southern Croatia

Point mutations in the 23S rRNA, gyrA, and gyrB genes can confer resistance to clarithromycin (CAM) and levofloxacin (LVX) by altering target sites or protein structure, thereby reducing the efficacy of standard antibiotics in the treatment of Helicobacter pylori infections. Considering the confirmed primary CAM and LVX resistance in H. pylori infected patients from southern Croatia, we performed a molecular genetic analysis of three target genes (23S rRNA, gyrA, and gyrB) by PCR and sequencing, together with computational molecular docking analysis. In the CAM-resistant isolates, the mutation sites in the 23S rRNA gene were A2142C, A2142G, and A2143G. In addition, the mutations D91G and D91N in GyrA and N481E and R484K in GyrB were associated with resistance to LVX. Molecular docking analyses revealed that mutant H. pylori strains with resistance-related mutations exhibited a lower susceptibility to CAM and LVX compared with wild-type strains due to significant differences in non-covalent interactions (e.g., hydrogen bonds, ionic interactions) leading to destabilized antibiotic-protein binding, ultimately resulting in antibiotic resistance. Dual resistance to CAM and LVX was found, indicating the successful evolution of H. pylori resistance to unrelated antimicrobials and thus an increased risk to human health.

Corneal foreign bodies: are antiseptics and antibiotics equally effective?

PURPOSE

To compare the effect of antiseptics and antibiotics on the occurrence of Infectious Keratitis (IK) secondary to Corneal Foreign Body (CFB) removal.

METHODS

Multicenter retrospective study conducted between June 2020 and June 2022 in patients referred for CFBs and treated with Picloxydine (Group 1) or Tobramycin (Group 2) for 7 days. A follow-up visit was scheduled on Day 3 (D3) and a phone call on D30. The primary outcome measure was the occurrence of IK.

RESULTS

307 patients (300 men) with a mean age of 42.8 (14.8) years were included. The mean (SD) time to consultation was 43.1 (45.6) hours. Picloxydine and Tobramycin were given to 155 and 152 patients. Half of patients (n = 154, 50.2%) were building workers and 209 (68.1%) did not wear eye protections. CFBs were mainly metallic (n = 292, 95.1%). Upon referral, rust was found in 220 patients (72.1%). A burr was used in 119 (38.9%) patients. IK occurred in 15 (4.9%) patients, 8 (5.3%) in Group 1 and 7 (4.5%) in Group 2 (p = 0.797). IK was successfully treated in all cases. Persistent rust was found in 113 patients (36.9%) on D3 without difference between burr or needle use (p = 0.278). On D3, corneal healing was delayed in 154 patients (47.2%), mainly in burr-treated patients (p = 0.003). The mean (SD) work stoppage duration was 0.32 (0.98) days.

CONCLUSION

IK rate was 4.9%. The efficacy of antibiotics and antiseptics was similar on CFB removal. Using a burr was associated with a longer healing time. CFBs had a limited social impact.

United we stand, divided we fall: in-depth proteomic evaluation of the synergistic effect of Mo-CBP3-PepI and Ciprofloxacin against Staphylococcus aureus biofilms

Staphylococcus aureus forms biofilms, a structure that protects bacterial cells, conferring more resistance to difficult treatment. Synthetic peptides surge as an alternative to overcome the biofilm of multidrug-resistant pathogens. Mo-CBP3-PepI, when combined with Ciprofloxacin, reduced preformed S. aureus biofilm by 50% at low concentrations (0.2 and 6.2 μg. mL-1, respectively). The goal of this study was to evaluate the proteomic profile of biofilms after treatment with the Mo-CBP3-PepI combined with ciprofloxacin. Here, proteomic analysis confirmed with more depth previously described mechanisms and revealed changes in the accumulation of proteins related to DNA and protein metabolism, cell wall biosynthesis, redox metabolism, quorum sensing, and biofilm formation. Some proteins related to DNA and protein metabolism were reduced, while other proteins, like redox system proteins, disappeared in Ciprofloxacin+Mo-CBP3-PepI treatment. Our results indicated a synergistic effect of these two molecules with several mechanisms against S. aureus biofilm and opened new doors for combined treatments with other drugs.

Updated Review on Clinically-Relevant Properties of Delafloxacin

The extensive use of fluoroquinolones has been consequently accompanied by the emergence of bacterial resistance, which triggers the necessity to discover new compounds. Delafloxacin is a brand-new anionic non-zwitterionic fluoroquinolone with some structural particularities that give it attractive proprieties: high activity under acidic conditions, greater in vitro activity against Gram-positive bacteria-even those showing resistance to currently-used fluoroquinolones-and nearly equivalent affinity for both type-II topoisomerases (i.e., DNA gyrase and topoisomerase IV). During phases II and III clinical trials, delafloxacin showed non-inferiority compared to standard-of-care therapy in the treatment of acute bacterial skin and skin structure infections and community-acquired bacterial pneumonia, which resulted in its approval in 2017 by the Food and Drug Administration for indications. Thanks to its overall good tolerance, its broad-spectrum in vitro activity, and its ease of use, it could represent a promising molecule for the treatment of bacterial infections.

Prevalence and mechanisms of ciprofloxacin resistance in Escherichia coli isolated from hospitalized patients, healthy carriers, and wastewaters in Iran

BACKGROUND

This study was aimed to evaluate the prevalence and molecular characteristics of ciprofloxacin resistance among 346 Escherichia coli isolates collected from clinical specimens (n = 82), healthy children (n = 176), municipal wastewater (n = 34), hospital wastewater (n = 33), poultry slaughterhouse wastewater (n = 12) and livestock (n = 9) slaughterhouse wastewater in Iran.

METHODS

Ciprofloxacin minimum inhibitory concentration (MIC) was determined by agar dilution assay. Phylogroups and plasmid-mediated quinolone resistance (PMQR) genes were identified using PCR. Mutations in gyrA, gyrB, parC, and parE genes and amino acid alterations were screened through sequencing assay. The effect of efflux pump inhibitor (PAβN) on ciprofloxacin MICs in ciprofloxacin-resistant isolates was investigated using the microdilution method.

RESULTS

In total, 28.03% of E. coli isolates were phenotypically resistant to ciprofloxacin. Based on sources of isolation, 64.63%, 51.51%, 33.33%, 14.70%, 10.22% and 8.33% of isolates from clinical specimens, hospital wastewater, livestock wastewater, municipal wastewater, healthy children and poultry wastewater were ciprofloxacin-resistant, respectively. Eighty-one point eighty-one percent (Ser-83 → Leu + Asp-87 → Asn; 78.78% and Ser-83 → Leu only; 3.03% (of ciprofloxacin-resistant E. coli isolates showed missense mutation in GyrA subunit of DNA gyrase, while no amino-acid substitution was noted in the GyrB subunit. DNA sequence analyses of the ParC and ParE subunits of topoisomerase IV exhibited amino-acid changes in 30.30% (Ser-80 → Ile + Glu-84 → Val; 18.18%, Ser-80 → Ile only; 9.10% and Glu-84 → Val only; 3.03%0 (and 15.38% (Ser-458 → Ala) of ciprofloxacin-resistant E. coli isolates, respectively. The PMQR genes, aac(6')-Ib-cr, qnrS, qnrB, oqxA, oqxB, and qepA were detected in 43.29%, 74.22%, 9.27%, 14.43%, 30.92% and 1.03% of ciprofloxacin-resistant isolates, respectively. No isolate was found to be positive for qnrA and qnrD genes. In isolates harboring the OqxA/B efflux pump, the MIC of ciprofloxacin was reduced twofold in the presence of PAβN, as an efflux pump inhibitor. The phylogroups B2 (48.45%) and A (20.65%) were the most predominant groups identified in ciprofloxacin-resistant isolates.

CONCLUSIONS

This study proved the high incidence of ciprofloxacin-resistant E. coli isolates in both clinical and non-clinical settings in Iran. Chromosomal gene mutations and PMQR genes were identified in ciprofloxacin resistance among E. coli population.

Using Targeted Nano-Antibiotics to Improve Antibiotic Efficacy against Staphylococcus aureus Infections

The poor bioavailability of antibiotics at infection sites is one of the leading causes of treatment failure and increased bacterial resistance. Therefore, developing novel, non-conventional antibiotic delivery strategies to deal with bacterial pathogens is essential. Here, we investigated the encapsulation of two fluoroquinolones, ciprofloxacin and levofloxacin, into polymer-based nano-carriers (nano-antibiotics), with the goal of increasing their local bioavailability at bacterial infection sites. The formulations were optimized to achieve maximal drug loading. The surfaces of nano-antibiotics were modified with anti-staphylococcal antibodies as ligand molecules to target S. aureus pathogens. The interaction of nano-antibiotics with the bacterial cells was investigated via fluorescent confocal microscopy. Conventional tests (MIC and MBC) were used to examine the antibacterial properties of nano-antibiotic formulations. Simultaneously, a bioluminescence assay model was employed, revealing the rapid and efficient assessment of the antibacterial potency of colloidal systems. In comparison to the free-form antibiotic, the targeted nano-antibiotic exhibited enhanced antimicrobial activity against both the planktonic and biofilm forms of S. aureus. Furthermore, our data suggested that the efficacy of a targeted nano-antibiotic treatment can be influenced by its antibiotic release profile.

Fluoroquinolone resistance does not facilitate phage Φ13 integration or excision in Staphylococcus aureus

Prophages of the ΦSa3int family are commonly found in human-associated strains of Staphylococcus aureus where they encode factors for evading the human innate immune system. In contrast, they are usually absent in livestock-associated methicillin-resistant S. aureus (LA-MRSA) strains where the phage attachment site is mutated compared to the human strains. However, ΦSa3int phages have been found in a subset of LA-MRSA strains belonging to clonal complex 398 (CC398), including a lineage that is widespread in pig farms in Northern Jutland, Denmark. This lineage contains amino acid changes in the DNA topoisomerase IV and the DNA gyrase encoded by grlA and gyrA, respectively, which have been associated with fluoroquinolone (FQ) resistance. As both of these enzymes are involved in DNA supercoiling, we speculated that the mutations might impact recombination between the ΦSa3int phage and the bacterial chromosome. To examine this, we introduced the FQ resistance mutations into S. aureus 8325-4attB_LA that carry the mutated CC398-like bacterial attachment site for ΦSa3int phages. When monitoring phage integration and release of Φ13, a well-described representative of the ΦSa3int phage family, we did not observe any significant differences between the FQ-resistant mutant and the wild-type strain. Thus our results suggest that mutations in grlA and gyrA do not contribute to the presence of the ΦSa3int phages in LA-MRSA CC398.

Effects of Temperature on Plasma Protein Binding Ratios (PPBRs) of Enrofloxacin and Ciprofloxacin in Yellow Catfish (Pelteobagrus fulvidraco), Grass Carp (Ctenopharyngodon idella), and Largemouth Bass (Micropterus salmoides)

The objective of this study was to investigate the PPBRs of EF and CF in the plasma of yellow catfish, grass carp, and largemouth bass at different temperatures with different concentrations. A fast and simple ultrafiltration method was used to determine the PPBRs of EF and CF. Results showed that PPBRs of EF decreased from 37.71% to 9.66%, from 46.10% to 13.52%, and from 43.90% to 4.36% in the plasma of yellow catfish with the increase of concentration from 15 to 25 °C. The same trends of PPBRs of EF were presented in the plasma of grass carp and largemouth bass. In comparison to the data at the same concentration of EF at disparate temperatures, the PPBRs of EF at a concentration of 1 µg/mL increased from 37.71% to 46.10% and then decreased to 43.90% in the plasma of yellow catfish with elevated temperature from 15 to 25 °C. There is no obvious regularity with the rise of temperature, and the same phenomenon also were found in other concentrations and species. Meanwhile, the PPBRs of CF also decreased in the three species with the rise in concentration. Under the consistent concentration, the temperature-dependent regularities were not found in the PPBRs of CF. Overall, the increased concentration reduced the PPBRs of EF and CF in the plasma of three fish species, and the alteration in temperature only has a certain effect on the PPBRs of EF and CF.

L-leucine increases the sensitivity of drug-resistant Salmonella to sarafloxacin by stimulating central carbon metabolism and increasing intracellular reactive oxygen species level

Introduction

The overuse of antibiotics has made public health and safety face a serious cisis. It is urgent to develop new clinical treatment methods to combat drug resistant bacteria to alleviate the health crisis. The efficiency of antibiotics is closely related to the metabolic state of bacteria. However, studies on fluoroquinolone resistant Salmonella are relatively rare.

Methods

CICC21484 were passaged in medium with and without sarafloxacin and obtain sarafloxacin- susceptible Salmonella Typhimurium (SAR-S) and sarafloxacin resistant Salmonella Typhimurium (SAR-R), respectively. Non-targeted metabolomics was used to analyze the metabolic difference between SAR-S and SAR-R. Then we verified that exogenous L-leucine promoted the killing effect of sarafloxacin in vitro, and measured the intracellular ATP, NADH and reactive oxygen species levels of bacteria. Gene expression was determined using Real Time quantitative PCR.

Results

We confirmed that exogenous L-leucine increased the killing effect of sarafloxacin on SAR-R and other clinically resistant Salmonella serotypes. Exogenous L-leucine stimulated the metabolic state of bacteria, especially the TCA cycle, which increased the working efficiency of the electron transfer chain and increased the intracellular NADH, ATP concentration, and reactive oxygen species level. Our results suggest that when the metabolism of drug-resistant bacteria is reprogrammed, the bactericidal effect of antibiotics improves.

Discussion

This study further enhances research in the anti-drug resistance field at the metabolic level and provides theoretical support for solving the current problem of sarafloxacin drug resistance, a unique fluoroquinolone drug for animals and indicating the potential of L-leucine as a new antibiotic adjuvant.

Molecular mechanisms of antibiotic resistance revisited

Antibiotic resistance is a global health emergency, with resistance detected to all antibiotics currently in clinical use and only a few novel drugs in the pipeline. Understanding the molecular mechanisms that bacteria use to resist the action of antimicrobials is critical to recognize global patterns of resistance and to improve the use of current drugs, as well as for the design of new drugs less susceptible to resistance development and novel strategies to combat resistance. In this Review, we explore recent advances in understanding how resistance genes contribute to the biology of the host, new structural details of relevant molecular events underpinning resistance, the identification of new resistance gene families and the interactions between different resistance mechanisms. Finally, we discuss how we can use this information to develop the next generation of antimicrobial therapies.

Human Salmonellosis: A Continuous Global Threat in the Farm-to-Fork Food Safety Continuum

Salmonella is one of the most common zoonotic foodborne pathogens and a worldwide public health threat. Salmonella enterica is the most pathogenic among Salmonella species, comprising over 2500 serovars. It causes typhoid fever and gastroenteritis, and the serovars responsible for the later disease are known as non-typhoidal Salmonella (NTS). Salmonella transmission to humans happens along the farm-to-fork continuum via contaminated animal- and plant-derived foods, including poultry, eggs, fish, pork, beef, vegetables, fruits, nuts, and flour. Several virulence factors have been recognized to play a vital role in attaching, invading, and evading the host defense system. These factors include capsule, adhesion proteins, flagella, plasmids, and type III secretion systems that are encoded on the Salmonella pathogenicity islands. The increased global prevalence of NTS serovars in recent years indicates that the control approaches centered on alleviating the food animals' contamination along the food chain have been unsuccessful. Moreover, the emergence of antibiotic-resistant Salmonella variants suggests a potential food safety crisis. This review summarizes the current state of the knowledge on the nomenclature, microbiological features, virulence factors, and the mechanism of antimicrobial resistance of Salmonella. Furthermore, it provides insights into the pathogenesis and epidemiology of Salmonella infections. The recent outbreaks of salmonellosis reported in different clinical settings and geographical regions, including Africa, the Middle East and North Africa, Latin America, Europe, and the USA in the farm-to-fork continuum, are also highlighted.

Plasma and tissue kinetics of enrofloxacin and its metabolite, ciprofloxacin, in yellow catfish (Pelteobagrus fulvidraco) after a single oral administration at different temperatures

The objective of this study was to examine the pharmacokinetic (PK) properties of enrofloxacin (EF) and its metabolite, ciprofloxacin (CF), in yellow catfish (Pelteobagrus fulvidraco) after a single oral dose of EF at 20 mg/kg at 20, 25, and 30 °C. Samples were collected at pre-designed time points and determined by high-performance liquid chromatography with a fluorescent detector. Results showed that most concentrations of EF and CF in plasma and tissues at the same time point at different temperatures were statistically significant. With the increase in temperature, the terminal half-life (T_1/2λz) of EF and CF was first reduced from 20 to 25 °C but elevated from 25 to 30 °C in plasma, muscle + skin, gill, liver, and kidney, respectively. The area under the plasma concentration-time curves (AUC_last) of EF were all decreased in plasma, muscle + skin, and gill except for that of EF in the liver and kidney. However, the AUC_last and the apparent metabolic rate of CF were exhibited first elevated and then decreased trend. The apparent volume of distribution (Vz_F) of EF was first reduced from 20 to 25 °C but increased at 30 °C. The apparent total body clearance (CL_F) of EF was increased from 0.15 to 0.32 L/h·kg with the temperature elevation. These indicated that increased temperature markedly affected the PKs of EF and CF in yellow catfish. Through in-depth analysis, the EF dosage of 20 mg/kg is appropriate to use in yellow catfish at 20 and 25 °C but 30 °C.

Genomic insights into antibiotic resistance and mobilome of lactic acid bacteria and bifidobacteria

Lactic acid bacteria (LAB) and Bifidobacterium sp. (bifidobacteria) can carry antimicrobial resistance genes (ARGs), yet data on resistance mechanisms in these bacteria are limited. The aim of our study was to identify the underlying genetic mechanisms of phenotypic resistance in 103 LAB and bifidobacteria using whole-genome sequencing. Sequencing data not only confirmed the presence of 36 acquired ARGs in genomes of 18 strains, but also revealed wide dissemination of intrinsic ARGs. The presence of acquired ARGs on known and novel mobile genetic elements raises the possibility of their horizontal spread. In addition, our data suggest that mutations may be a common mechanism of resistance. Several novel candidate resistance mechanisms were uncovered, providing a basis for further in vitro studies. Overall, 1,314 minimum inhibitory concentrations matched with genotypes in 92.4% of the cases; however, prediction of phenotype based on genotypic data was only partially efficient, especially with respect to aminoglycosides and chloramphenicol. Our study sheds light on resistance mechanisms and their transferability potential in LAB and bifidobacteria, which will be useful for risk assessment analysis.

Antimicrobial Resistance Molecular Mechanisms of Helicobacter pylori in Jordanian Children: A Cross-Sectional Observational Study

Background: H. pylori antimicrobial resistance causes increasing treatment failure rates among H. pylori gastritis in children. This study investigates the molecular mechanisms of H. pylori antimicrobial resistance among Jordanian children. Methods: Demographic, clinical, and laboratory data were recorded for children referred to Prince Hamzah Hospital. Clarithromycin, Metronidazole, and Levofloxacin susceptibility were tested via E-test. Clarithromycin-related mutations were investigated using Real-Time (RT)-PCR and Levofloxacin resistance was analyzed with DNA sequencing of the gyrA gene. Results: 116 children were recruited, including 55.2% females and 55.2% in the age range of 10.1 to 14 years. A total of 82.7% were naïve to eradication therapy. H. pylori positivity was 93.9%, 89.6%, 61.7%, and 84.3% according to Rapid Urease Test, histology, culture, and RT-PCR, respectively. Resistance rates were 25.9% for Clarithromycin, 50% for Metronidazole, and 6.9% for Levofloxacin via E-test. A2142G or A2143G or a combination of both mutations concerning Clarithromycin resistance were documented in 26.1% of samples, while mutations in gyrA gen-related to Levofloxacin resistance were reported in 5.3% of samples. Antibiotic resistance was significantly affected by abdominal pain, anemia, hematemesis, and histological findings (p < 0.05). Conclusion: H. pylori resistance was documented for Metronidazole and Clarithromycin. RT-PCR for H. pylori identification and microbial resistance determination are valuable alternatives for cultures in determining antimicrobial susceptibility.

Antibiotics and Bacterial Resistance-A Short Story of an Endless Arms Race

Despite the undisputed development of medicine, antibiotics still serve as first-choice drugs for patients with infectious disorders. The widespread use of antibiotics results from a wide spectrum of their actions encompassing mechanisms responsible for: the inhibition of bacterial cell wall biosynthesis, the disruption of cell membrane integrity, the suppression of nucleic acids and/or proteins synthesis, as well as disturbances of metabolic processes. However, the widespread availability of antibiotics, accompanied by their overprescription, acts as a double-edged sword, since the overuse and/or misuse of antibiotics leads to a growing number of multidrug-resistant microbes. This, in turn, has recently emerged as a global public health challenge facing both clinicians and their patients. In addition to intrinsic resistance, bacteria can acquire resistance to particular antimicrobial agents through the transfer of genetic material conferring resistance. Amongst the most common bacterial resistance strategies are: drug target site changes, increased cell wall permeability to antibiotics, antibiotic inactivation, and efflux pumps. A better understanding of the interplay between the mechanisms of antibiotic actions and bacterial defense strategies against particular antimicrobial agents is crucial for developing new drugs or drug combinations. Herein, we provide a brief overview of the current nanomedicine-based strategies that aim to improve the efficacy of antibiotics.

Phenotypic and genotypic survey of antibiotic resistance in Salmonella enterica isolates from dairy farms in Uruguay

Salmonella enterica is an important zoonotic pathogen that is frequently identified in dairy farming systems. An increase in antibiotic resistance has led to inadequate results of treatments, with impacts on animal and human health. Here, the phenotypic and genotypic susceptibility patterns of Salmonella isolates from dairy cattle and dairy farm environments were evaluated and compared. A collection of 75 S. enterica isolates were evaluated, and their phenotypic susceptibility was determined. For genotypic characterization, the whole genomes of the isolates were sequenced, and geno-serotypes, sequence types (STs) and core-genome-sequence types were determined using the EnteroBase pipeline. To characterize antibiotic resistance genes and gene mutations, tools from the Center for Genomic Epidemiology were used. Salmonella Dublin (SDu), S. Typhimurium (STy), S. Anatum (SAn), S. Newport (SNe), S. Agona (Sag), S. Montevideo (SMo) and IIIb 61:i:z53 were included in the collection. A single sequence type was detected per serovar. Phenotypic non-susceptibility to streptomycin and tetracycline was very frequent in the collection, and high non-susceptibility to ciprofloxacin was also observed. Multidrug resistance (MDR) was observed in 42 isolates (56.0%), with SAn and STy presenting higher MDR than the other serovars, showing non-susceptibility to up to 6 groups of antibiotics. Genomic analysis revealed the presence of 21 genes associated with antimicrobial resistance (AMR) in Salmonella isolates. More than 60% of the isolates carried some gene associated with resistance to aminoglycosides and tetracyclines. Only one gene associated with beta-lactam resistance was found, in seven isolates. Two different mutations were identified, parC_T57S and acrB_R717Q, which confer resistance to quinolones and azithromycin, respectively. The accuracy of predicting antimicrobial resistance phenotypes based on AMR genotypes was 83.7%. The genomic approach does not replace the phenotypic assay but offers valuable information for the survey of circulating antimicrobial resistance. This work represents one of the first studies evaluating phenotypic and genotypic AMR in Salmonella from dairy cattle in South America.

Fluoroquinolone-resistance mechanisms and molecular epidemiology of ciprofloxacin-resistant Klebsiella pneumoniae isolates in Iran

Klebsiella pneumoniae is an important cause of nosocomial infections and displays increasing resistance to fluoroquinolones (FQ). This study surveyed the mechanisms of FQ resistance and molecular typing of K. pneumoniae isolates from intensive care units patients in Tehran, Iran. A total of 48 ciprofloxacin (CIP) resistant K. pneumoniae isolates from urine samples were included in this study. Broth microdilution assays revealed high-level CIP resistance (MIC > 32 μg/mL) in 31.25% of the isolates. Plasmid-mediated quinolone resistance genes were detected in 41 (85.4%) isolates. Among which, qnrS (41.67%) was the most prevalent followed by qnrD (35.42%), qnrB (27.1%), qnrA (25%), qepA (22.9%), aac(6')-Ib-cr (20.83%), and qnrC (6.25%). Target site mutations (gyrA and parC) were assessed using PCR and sequencing on all isolates. A single mutation in gyrA (S83I) was found in 13 (27.1%) isolates and two isolates harbored six simultaneous mutations. Fourteen isolates (29.2%) had mutations in parC and S129A and A141V mutations were the most prevalent. Real time PCR showed an increase in the expression level of acrB and oqxB efflux genes in 68.75 and 29.16% isolates, respectively. Enterobacterial repetitive intergenic consensus (ERIC)-PCR revealed 14 genotypes and 11 of them were classified by multilocus sequence typing (MLST) into 11 different sequence types belonging to seven clonal complexes and two singletons, most of them have not been reported in Iran yet. We are concerned about the spread of these clones throughout our country. Most FQ resistance mechanisms were detected among our isolates. However, target site mutation had the greatest effect on CIP resistance among our isolates.

Overview of Side-Effects of Antibacterial Fluoroquinolones: New Drugs versus Old Drugs, a Step Forward in the Safety Profile?

Antibacterial fluoroquinolones (FQs) are frequently used in treating infections. However, the value of FQs is debatable due to their association with severe adverse effects (AEs). The Food and Drug Administration (FDA) issued safety warnings concerning their side-effects in 2008, followed by the European Medicine Agency (EMA) and regulatory authorities from other countries. Severe AEs associated with some FQs have been reported, leading to their withdrawal from the market. New systemic FQs have been recently approved. The FDA and EMA approved delafloxacin. Additionally, lascufloxacin, levonadifloxacin, nemonoxacin, sitafloxacin, and zabofloxacin were approved in their origin countries. The relevant AEs of FQs and their mechanisms of occurrence have been approached. New systemic FQs present potent antibacterial activity against many resistant bacteria (including resistance to FQs). Generally, in clinical studies, the new FQs were well-tolerated with mild or moderate AEs. All the new FQs approved in the origin countries require more clinical studies to meet FDA or EMA requirements. Post-marketing surveillance will confirm or infirm the known safety profile of these new antibacterial drugs. The main AEs of the FQs class were addressed, highlighting the existing data for the recently approved ones. In addition, the general management of AEs when they occur and the rational use and caution of modern FQs were outlined.

Quinolone Antibiotics: Resistance and Therapy

The clinical application of quinolone antibiotics is particularly extensive. In addition to their high efficiency in infectious diseases, the treatment process brings multiple hidden dangers or side effects. In this regard, drug resistance becomes a major challenge and is almost unavoidable in the clinical application of quinolones. Both genetic and phenotypic variations contribute to bacterial survival resistance under antibiotic therapy. This review is focusing on the drug discovery history, compound structure, and bactericidal mechanism of quinolone antibiotics. Recent studies bring a more in-depth insight into the research progress of quinolone antibiotics in the causes of death, drug resistance formation, and closely related SOS response after disease treatment at this stage. Combined with the latest clinical studies, we summarize the clinical application of quinolone antibiotics and further lay a theoretical foundation for the mechanism study of resistant or sensitive bacteria in response to quinolone treatment.

Development of diagnostic tests for pathogen identification and detection of antimicrobial resistance on WHO global priority pathogens using modular real-time nucleic acid amplification test

BACKGROUND

Concerns regarding antimicrobial resistance (AMR) have resulted in the World Health Organization (WHO) designating so-called global priority pathogens (GPPs). However, little discussion has focused on the diagnosis of GPPs. To enable the simultaneous identification of pathogens and AMR, we developed a modular real-time nucleic acid amplification test (MRT-NAAT).

METHODS

Sequence-specific primers for each modular unit for MRT-NAAT pathogen identification and AMR sets were designed. The composition of the reaction mixture and the real-time PCR program were unified irrespective of primer type so to give MRT-NAAT modularity. Standard strains and clinical isolates were used to evaluate the performance of MRT-NAAT by real-time PCR and melting curve analysis. Probit analysis for the MRT-NAAT pathogen identification set was used to assess the limit of detection (LoD).

RESULTS

The MRT-NAAT pathogen identification set was made up of 15 modular units 109-199 bp in product size and with a T_ms of 75.5-87.5 °C. The LoD was < 15.548 fg/μL, and nine modular units successfully detected the target pathogens. The MRT-NAAT AMR set included 24 modular units 65-785 bp in product size with a T_ms of 75.5-87.5 °C; it showed high performance for detecting GPP target genes and variants.

CONCLUSIONS

MRT-NAAT enables pathogen identification and AMR gene detection and is time-effective. By unifying the reaction settings of each modular unit, the modularity where combinations of primers can be used according to need could be achieved. This would greatly help in reflecting the researcher's need and the AMR status of a certain region while successfully detecting pathogens and AMR genes.

Antibacterial activity of metal-phenanthroline complexes against multidrug-resistant Irish clinical isolates: a whole genome sequencing approach

Antimicrobial resistance (AMR) is one of the serious global health challenges of our time. There is now an urgent need to develop novel therapeutic agents that can overcome AMR, preferably through alternative mechanistic pathways from conventional treatments. The antibacterial activity of metal complexes (metal = Cu(II), Mn(II), and Ag(I)) incorporating 1,10-phenanthroline (phen) and various dianionic dicarboxylate ligands, along with their simple metal salt and dicarboxylic acid precursors, against common AMR pathogens were investigated. Overall, the highest level of antibacterial activity was evident in compounds that incorporate the phen ligand compared to the activities of their simple salt and dicarboxylic acid precursors. The chelates incorporating both phen and the dianion of 3,6,9-trioxaundecanedioic acid (tdda) were the most effective, and the activity varied depending on the metal centre. Whole-genome sequencing (WGS) was carried out on the reference Pseudomonas aeruginosa strain, PAO1. This strain was exposed to sub-lethal doses of lead metal-tdda-phen complexes to form mutants with induced resistance properties with the aim of elucidating their mechanism of action. Various mutations were detected in the mutant P. aeruginosa genome, causing amino acid changes to proteins involved in cellular respiration, the polyamine biosynthetic pathway, and virulence mechanisms. This study provides insights into acquired resistance mechanisms of pathogenic organisms exposed to Cu(II), Mn(II), and Ag(I) complexes incorporating phen with tdda and warrants further development of these potential complexes as alternative clinical therapeutic drugs to treat AMR infections.

Comprehensive profiling of serotypes, antimicrobial resistance and virulence of Salmonella isolates from food animals in China, 2015-2021

Introduction

Salmonella is a ubiquitous foodborne pathogen and mainly transmitted to human farm-to-fork chain through contaminated foods of animal origin.

Methods

In this study, we investigated the serotypes, antimicrobial resistance and virulence of Salmonella from China.

Results

A total of 617 Salmonella isolates were collected from 4 major food animal species across 23 provi nces in China from 2015-2021. Highest Salmonella prevalence were observed in Guangdong (44.4%) and Sandong (23.7%). Chickens (43.0%) was shown to be the major source of Salmonella contamination, followed by pigs (34.5%) and ducks (18.5%). The number of Salmonella increased significantly from 5.51% to 27.23% during 2015-2020. S. Derby (17.3%), S. Enteritidis (13.1%) and S. Typhimurium (11.4%) were the most common serotypes among 41 serotypes identifiedin this study. Antibiotic susceptibility testing showing that the majority of the Salmonella isolates were resistant to neomycin (99.7%), tetracycline (98.1%), ampicillin (97.4%), sulfadiazine/trimethoprim (97.1%), nalidixic acid (89.1%), doxycycline (83.1%), ceftria xone (70.3%), spectinomycin (67.7%), florfenicol (60.0%), cefotaxime (52.0%) and lomefloxacin (59.8%). The rates of resistance to multiple antibiotics in S. Derby and S.Typhimurium were higher than that in S. Enteritidis. However, the rate of resistance to fosfomycin were observed from higher to lower by S. Derby, S. Enteritidis, and S. Typhimurium. Biofilm formation ability analysis found that 88.49%of the Salmonella were able to produce biofilms, of which 236 Salmonella isolates were strong biofilm producer. Among the 26 types of antibiotics resistance genes (ARGs) were identified in this study, 4 ARGs (tetB,sul2,aadA2, and aph(3')-IIa) were highly prevalent. In addition, 5 β-lactam resistance genes (bla _TEM, bla _SHV, bla _CMY-2, bla _CTX-M, and bla _OXA) and 7 quinolone resistance genes (oqxA, oqxB, qnrB, qnrC, qnrD, qnrS, and qeqA) were detected among these isolates. 12 out of 17 virulence genes selected in this study were commonly presented in the chromosomes of tested isolate, with a detection rate of over 80%, including misL, spiA, stn, pagC, iroN, fim, msgA, sopB, prgH, sitC, ttrC, spaN.

Discussion

This study provided a systematical updating on surveillance on prevalence of Salmonella from food animals in China, shedding the light on continued vigilance for Salmonella in food animals.