Third-generation Fluoroquinolones Research Articles

β-lactamase and Plasmid-mediated Quinolone Resistance Determinants Among Proteus spp. Isolates at a Tertiary-care Hospital in Kolkata, India

Background: Emerging antibiotic resistance (ABR) in Proteus spp., especially to third-generation cephalosporins (3GCc), carbapenems, and fluoroquinolones, challenges the treatment outcome and infection prevention. Limited studies pose a knowledge gap between them and ABR. Methods: We investigated the in vitro efficacy of therapeutic options and prevalence of β-lac-tamase and plasmid-mediated quinolone resistance (PMQR) traits in 3GC- and/or fluoroquino-lone-nonsusceptible Proteus (P.) spp. (n=27) in Kolkata, India, during 2021–2022. P. mirabilis was commonly isolated (>80%) from superficial and urine samples. The majority of the isolates (48-78%) remained susceptible to piperacillin-tazobactam, meropenem, amikacin, cefoperazone-sulbactam, and cefepime. Results: All isolates showed >0.2 multiple-antibiotic resistance index, with >65% being multi-drug and >30% being extensively drug-resistant. blaTEM (n=9), blaNDM (n=9), and qnrA (n=6) were commonly noted with the co-production of β-lactamases and PMQR in ten (37%) isolates. More than 50% of the isolates were devoid of the tested acquired genes. Conclusion: The study concludes that superbugs dominate, with limited occurrence of plasmid-borne markers in this geographic location.

Multidrug-resistant Escherichia coli causing canine pyometra and urinary tract infections are genetically related but distinct from those causing prostatic abscesses

Despite extensive characterisation of uropathogenic Escherichia coli (UPEC) causing urinary tract infections (UTIs), the genetic background of non-urinary extraintestinal pathogenic E. coli (ExPEC) in companion animals remains inadequately understood. In this study, we characterised virulence traits of 104 E. coli isolated from canine pyometra (n = 61) and prostatic abscesses (PAs) (n = 38), and bloodstream infections (BSIs) in dogs (n = 2), and cats (n = 3). A stronger association with UPEC of pyometra strains in comparison to PA strains was revealed. Notably, 44 isolates exhibited resistance to third-generation cephalosporins and/or fluoroquinolones, 15 were extended-spectrum ß-lactamase-producers. Twelve multidrug-resistant (MDR) strains, isolated from pyometra (n = 4), PAs (n = 5), and BSIs (n = 3), along with 7 previously characterised UPEC strains from dogs and cats, were sequenced. Genomic characteristics revealed that MDR E. coli associated with UTIs, pyometra, and BSIs belonged to international high-risk E. coli clones, including sequence type (ST) 38, ST131, ST617, ST648, and ST1193. However, PA strains belonged to distinct lineages, including ST12, ST44, ST457, ST744, and ST13037. The coreSNPs, cgMLST, and pan-genome illustrated intra-clonal variations within the same ST from different sources. The high-risk ST131 and ST1193 (phylogroup B2) contained high numbers of ExPEC virulence genes on pathogenicity islands, predominating in pyometra and UTI. Hybrid MDR/virulence IncF multi-replicon plasmids, containing aerobactin genes, were commonly found in non-B2 phylogroups from all sources. These findings offer genomic insights into non-urinary ExPEC, highlighting its potential for invasive infections in pets beyond UTIs, particularly with regards to high-risk global clones.

Toward an optimization of empirical antibiotic therapy in acute graft pyelonephritis: A retrospective multicenter study

ObjectiveAcute graft pyelonephritis (AGPN) is the most frequent infectious complication in kidney transplant recipients (KTR). The treatment of acute community-acquired (CA) pyelonephritis is based on third-generation cephalosporins (3GC) and fluoroquinolones. Cefepime or a piperacillin-tazobactam combination are more often used in healthcare-associated (HCA) infections. However, these recommendations do not consider the resistance observed in KTRs. The objective of our study was to define the most appropriate empirical antibiotherapy for AGPN in KTRs according to the CA and HCA settings. To answer this question, we assessed the prevalence of resistance to different antibiotics usually recommended for urinary tract infections (UTIs) in the general population. MethodsObservational, retrospective, multicenter study covering all episodes of AGPN occurring in hospitalized KTRs in 2019. ResultsA total of 210 patients were included in 7 centers and 244 episodes of AGPN were analyzed (158 CA-AGPN and 86 HCA-AGPN). The prevalence of 3GC and fluoroquinolone resistance was 23 % (n = 36) and 30 % (n = 50) in CA infections (n = 158), and 47 % (n = 40) and 31 % (n = 27) in HCA infections (n = 86), respectively. Cefepime resistance rate was 19 % (n = 30) in CA-AGPN and 29 % (n = 25) in HCA-AGPN. Piperacillin-tazobactam combination had resistance rates > 15 % in both CA and HCA infections. The only antimicrobials with resistance rates < 10 % were aminoglycosides and carbapenems. ConclusionNone of the antibiotics recommended in empirical treatment in UTIs has shown a resistance rate of less than 10% with regard to AGPN. Therefore, none of them should be used as monotherapy. A combination therapy including amikacin could be an appropriate strategy in this setting.

Antibiotic Resistance Profile of Salmonella sp. Isolates from Commercial Laying Hen Farms in Central-Western Brazil.

Microbial resistance to antibiotics poses a significant threat to both human and animal health, necessitating international efforts to mitigate this issue. This study aimed to assess the resistance profiles of Salmonella sp. isolates and identify the presence of intl1, sul1, and blaTEM resistance genes within antigenically characterized isolates, including Agona, Livingstone, Cerro, Schwarzengrund, Salmonella enterica subsp. enterica serotype O:4.5, Anatum, Enteritidis, Johannesburg, Corvallis, and Senftenberg. These isolates underwent susceptibility testing against 14 antibiotics. The highest resistance percentages were noted for sulfamethoxazole (91%), sulfonamides (51%), and ceftiofur (28.9%), while no resistance was observed for ciprofloxacin. Salmonella Johannesburg and Salmonella Corvallis showed resistance to one antibiotic, whereas other serovars were resistant to at least two. Salmonella Schwarzengrund exhibited resistance to 13 antibiotics. The intl1 gene was detected in six out of the ten serovars, and the sul1 gene in three, always co-occurring with intl1. The blaTEM gene was not identified. Our findings highlight the risk posed by the detected multiple resistances and genes to animal, human, and environmental health. The multidrug resistance, especially to third-generation cephalosporins and fluoroquinolones, highlights the need for stringent monitoring of Salmonella in laying hens. The potential of the environment, humans, eggs, and their products to act as vectors for antibiotic resistance represents a significant concern for One Health.

Quantum dot-based fluorescence-linked immunosorbent assay for the rapid detection of lomefloxacin in animal-derived foods

Lomefloxacin (LMF), a third-generation fluoroquinolone antibacterial agent, is often used to treat bacterial and mycoplasma infections. However, due to its prolonged half-life and slow metabolism, it is prone to residues in animal-derived foods, posing a potential food safety risk. Therefore, it is particularly urgent and important to establish a method for detecting lomefloxacin. In this study, direct and indirect competitive fluorescence-linked immunosorbent assay (dc-FLISA and ic-FLISA) based on quantum dots (QDs) was established for the detection of LMF. As for dc-FLISA, the half-maximal inhibitory concentration (IC50) and limit of detection (LOD) were 0.84 ng/mL, 0.04 ng/mL, respectively, the detection ranges from 0.08 to 9.11 ng/mL. The IC50 and LOD of ic-FLISA were 0.43 ng/mL and 0.03 ng/mL, respectively, meanwhile the detection ranges from 0.05 to 3.49 ng/mL. The recoveries of dc-FLISA and ic-FLISA in animal-derived foods (milk, fish, chicken, and honey), ranged from 95.8% to 105.2% and from 96.3% to 103.4%, respectively, with the coefficients of variation less than 8%. These results suggest that the dc-FLISA and ic-FLISA methods, which are based on QD labelling, are highly sensitive and cost-effective, and can be effectively used to detect LMF in animal-derived foods.

Molecular characterization of extended-spectrum beta-lactamases and carbapenemases producing Enterobacteriaceae isolated from North Eastern region of India

Objectives: This study is aimed to investigate the prevalence of genes encoding extended-spectrum β-lactamases (ESBLs) and carbapenemases production among Enterobacteriaceae isolated from North East India. Materials and Methods: A total of 210 non-duplicate multi-drug resistant Enterobacteriaceae (MDRE) strains were included in this investigation. The isolates were resistant to third-generation cephalosporins, aminoglycosides, and fluoroquinolones. First, the strains were subjected to phenotypic assays to determine ESBLs and carbapenemases production; then, multiplex polymerase chain reaction (mPCR) assays were done to detect ESBLs and carbapenemases genes. In addition, efflux pump activity was determined by phenylalanine-arginine b-naphthylamide assay. Statistical Analysis: The frequency of ESBLs and carbapenemase genes among MDRE strains was shown as percentages. The data analysis was done using Microsoft Excel computer software. Results: Among 210 MDRE clinical isolates, ESBLs production was observed in 72.86% (153) isolates. During mPCR assay, gene encoding ESBLs were detected in 55.24% (116) MDRE strains beta-lactamase Temoniera (blaTEM) (26.67%, 56), beta-lactamase Cefotaxime-Munich (blaCTX-M) (19.52%, 41), and beta-lactamase sulfhydryl reagent variable (blaSHV) (9.05%, 19)]. In addition, 55 (26.2%) and 53 (25.26%) strains were found to be meropenem and imipenem resistant, respectively. Carbapenemase nordmann-poirel (Carba-NP) test for carbapenemases activity was found to be positive in 18.58% (39) MDRE strains. The genes encoding carbapenemases production was observed in 18.58% (39) MDRE [beta-lactamase New Delhi metallo-β-lactamases-1(blaNDM-1) (8.10%, 17), beta-lactamase oxacillinase-48 (blaOXA-48) (2.86%, 6), beta-lactamase Verona imipenemase (blaVIM) (1.43%, 3), and blaOXA-48 and blaVIM (6.19%, 13)]. Efflux pump activity was observed in 5 (2.3%) of Carbapenem-resistant Enterobacteriaceae isolates. Conclusions: For the first time in this region, we have detected the presence of blaOXA-48 and blaVIM in a single MDRE isolate as high as 6.1%. Therefore, clinicians need to detect the ESBLs and carbapenemases producing Enterobacteriaceae on priority in hospital settings for therapeutic options as well as stringent infection control strategies to be adopted as precautions.

Genome sequencing of Porostereum spadiceum to study the degradation of levofloxacin

Despite various plans to rationalize antibiotic use, antibiotic resistance in environmental bacteria is increasing due to the accumulation of antibiotic residues in the environment. This study aimed to test the ability of basidiomycete fungal strains to biotransform the antibiotic levofloxacin, a widely-used third-generation broad-spectrum fluoroquinolone, and to propose enzyme targets potentially involved in this biotransformation. The biotransformation process was performed using fungal strains. Levofloxacin biotransformation reached 100% after 9 days of culture with Porostereum spadiceum BS34. Using genomics and proteomics analyses coupled with activity tests, we showed that P. spadiceum produces several heme-peroxidases together with H2O2-producing enzymes that could be involved in the antibiotic biotransformation process. Using UV and high-resolution mass spectrometry, we were able to detect five levofloxacin degradation products. Their putative identity based on their MS2 fragmentation patterns led to the conclusion that the piperazine moiety was the main target of oxidative modification of levofloxacin by P. spadiceum, leading to a decrease in antibiotic activity.

Retrospective Cohort Study on Delftia acidovorans Infections in Patients: A Rare and Significant Infection.

In recent years, Delftia acidovorans has gained attention for its rare occurrence in patient infections. The literature consists mostly of case reports, necessitating further research to comprehensively understand risk factors, clinical characteristics, and management strategies. We conducted a retrospective cohort study involving patients diagnosed with Delftia acidovorans infection at a tertiary teaching hospital between January 2014 and December 2022. The data included demographic details, comorbidities, bacterial cultures, antibiotic susceptibility, and treatment outcomes. There were 26 patients diagnosed with Delftia acidovorans infection who were predominantly older with multiple comorbidities. Approximately 76.9% of Delftia acidovorans infection patients had polymicrobial infections. Twenty-one patients had received antibiotics within three months before they developed the Delftia acidovorans infection, and these antibiotics were primarily third-generation cephalosporins, glycopeptides and fluoroquinolones. Antibiotic susceptibility testing showed resistance to aminoglycosides and susceptibility to imipenem, meropenem, ceftazidime, and piperacillin/tazobactam. Treatment outcome showed a mortality rate of 11.5%, mainly in patients with malignancy and advanced age. Delftia acidovorans infections predominantly affect older patients with multiple comorbidities. In terms of antibiotic therapy, carbapenems, cephalosporins, and piperacillin/tazobactam with antipseudomonal activity could all be considered.

Antibiotic susceptibility patterns of pathogens isolated from hospitalized patients with advanced HIV disease (AHD) in Bihar, India.

To describe the prevalence of common bacterial pathogens and antibiotic susceptibility patterns amongst advanced HIV disease (AHD) patients admitted between May 2019 and March 2021 to a Médecins Sans Frontières (MSF)-supported AHD inpatient unit in Bihar, India. A retrospective analysis of routinely collected demographic, clinical and microbiological data. Antibacterial susceptibility testing was done by an accredited referral laboratory using the modified Kirby-Bauer disc diffusion method. A total of 238 isolates from 577 patients were identified through culture testing. Patient median (IQR) age was 38 (31-45) years, and 75% were male. Predominant sample types included blood (600; 38%), urine (266; 17%) and sputum (178; 11%). Of the isolated bacteria, Escherichia coli (80; 13.9%) was the most prevalent, followed by Klebsiella pneumonia (54; 9.4%), Pseudomonas aeruginosa (22; 3.8%), Klebsiella oxytoca (10; 1.7%), Proteus mirabilis (9; 1.6%), and Acinetobacter baumannii (7; 1.2%). The resistance pattern showed that most bacterial isolates were highly resistant to commonly prescribed antibiotics such as third-generation cephalosporins, fluoroquinolones and co-trimoxazole. Most pathogens were moderately resistant to antibiotics from the WHO Watch group, such as meropenem and piperacillin/tazobactam. In contrast, isolates were more susceptible to aminoglycosides, such as amikacin, gentamicin and nitrofurantoin. In Bihar, inpatients with AHD displayed a concerning array of antibiotic-resistant infections. This study provides a starting point from which further work on antimicrobial resistance in this vulnerable cohort of patients can be conducted.

Antimicrobial use and combination of resistance phenotypes in bacteraemic Escherichia coli in primary care: a study based on Japanese national data in 2018.

Antimicrobial use (AMU) in primary care is a contributing factor to the emergence of antimicrobial-resistant bacteria. We assessed the potential effects of AMU on the prevalence of a combination of resistance phenotypes in bacteraemic Escherichia coli in outpatient care settings between primary care facilities ('clinics') and hospitals. Population-weighted total AMU calculated from the national database was expressed as DDDs per 1000 inhabitants per day (DID). National data for all routine microbiological test results were exported from the databases of a major commercial clinical laboratory, including 16 484 clinics, and the Japan Nosocomial Infections Surveillance, including 1947 hospitals. AMU and the prevalence of combinations of resistance phenotypes in bacteraemic E. coli isolates were compared between clinics and hospitals. The five most common bacteria isolated from patients with bacteraemia were the same in clinics, outpatient settings and inpatient settings in hospitals, with E. coli as the most frequent. Oral third-generation cephalosporins and fluoroquinolones were the top two AMU outpatient drugs, except for macrolides, and resulted in at least three times higher AMU in clinics than in hospitals. The percentage of E. coli isolates resistant to both drugs in clinics (18.7%) was 5.6% higher than that in hospitals (13.1%) (P < 10-8). Significant AMU, specifically of oral third-generation cephalosporins and fluoroquinolones, in clinics is associated with a higher prevalence of E. coli isolates resistant to both drugs. This study provides a basis for national interventions to reduce inappropriate AMU in primary care settings.

Two-Dose Ceftiofur Treatment Increases Cephamycinase Gene Quantities and Fecal Microbiome Diversity in Dairy Cows Diagnosed with Metritis.

Antimicrobial resistance is a significant concern worldwide; meanwhile, the impact of 3rd generation cephalosporin (3GC) antibiotics on the microbial communities of cattle and resistance within these communities is largely unknown. The objectives of this study were to determine the effects of two-dose ceftiofur crystalline-free acid (2-CCFA) treatment on the fecal microbiota and on the quantities of second-and third-generation cephalosporin, fluoroquinolone, and macrolide resistance genes in Holstein-Friesian dairy cows in the southwestern United States. Across three dairy farms, 124 matched pairs of cows were enrolled in a longitudinal study. Following the product label regimen, CCFA was administered on days 0 and 3 to cows diagnosed with postpartum metritis. Healthy cows were pair-matched based on lactation number and calving date. Fecal samples were collected on days 0, 6, and 16 and pooled in groups of 4 (n = 192) by farm, day, and treatment group for community DNA extraction. The characterization of community DNA included real-time PCR (qPCR) to quantify the following antibiotic resistance genes: blaCMY-2, blaCTX-M, mphA, qnrB19, and the highly conserved 16S rRNA back-calculated to gene copies per gram of feces. Additionally, 16S rRNA amplicon sequencing and metagenomics analyses were used to determine differences in bacterial community composition by treatment, day, and farm. Overall, blaCMY-2 gene copies per gram of feces increased significantly (p ≤ 0.05) in the treated group compared to the untreated group on day 6 and remained elevated on day 16. However, blaCTX-M, mphA, and qnrB19 gene quantities did not differ significantly (p ≥ 0.05) between treatment groups, days, or farms, suggesting a cephamycinase-specific enhancement in cows on these farms. Perhaps unexpectedly, 16S rRNA amplicon metagenomic analyses showed that the fecal bacterial communities from treated animals on day 6 had significantly greater (p ≤ 0.05) alpha and beta diversity than the untreated group. Two-dose ceftiofur treatment in dairy cows with metritis elevates cephamycinase gene quantities among all fecal bacteria while paradoxically increasing microbial diversity.

Prevalence and Shifts in Antibiotic Use in an Italian Hospital: A Comparison of 2016 and 2022 Data

Abstract Background Antibiotics are among the most commonly prescribed drugs, but inappropriate prescription rates (molecule, duration or dosage) remain high, leading to the selection of multidrug-resistant microorganisms. This study aims to describe the most commonly used antibiotics in our hospital and compare them to 2016 data. Methods Conducted in November 2022 at the Azienda Ospedaliera Universitaria delle Marche of Ancona (Italy), the study followed the protocol proposed by the European Center for Disease Prevention and Control (ECDC). Patients admitted to wards before 8 a.m. and not discharged at the time of the survey were included. Data from 2022 were compared to the 2016 study. Results In 2022, 41.7% (N = 284) of the 681 patients were taking at least one antibiotic, with 400 antibiotic therapies administered, of which 90.5% were given parenterally. Among the patients on antimicrobial therapy, 40% were being treated for a community infection, 27% for a hospital acquired infection and 19% for surgical prophylaxis. Among all the antimicrobial prescriptions used, the most used class of antibiotics in 2022 was penicillin / beta lactamase inhibitor (21.6%, N = 86), followed by third-generation cephalosporins (11.8%, N = 47), carbapenems (11.6%, N = 46), glycopeptides (8.8%, N = 35), first-generation cephalosporins (8.8%, N = 35) and fluoroquinolones (7.0%, N = 28). Data from 2016 registered a 21.2% prevalence of penicillin / beta lactamase inhibitor, 15.7% of fluoroquinolones, 14.7% of third-generation cephalosporins, 10.5% first-generation cephalosporins, 7.6% of carbapenems and 4.1% of glycopeptides. Conclusions The prevalence of antibiotics used in our hospital has changed after six years. This shift may be due to new patterns of bacterial resistance and new antimicrobial drugs (e.g. cefiderocol). Key messages • Our study found a shift in prevalence of antibiotic use in our hospital after six years. • Penicillin/beta lactamase inhibitors are still the most commonly used antibiotics in our hospital.

Frequency of isolation and phenotypic antimicrobial resistance of fecal Salmonella enterica recovered from dairy cattle in Canada

Salmonellosis is one of the leading causes of gastrointestinal infections in humans. In Canada, it is estimated that approximately 87,500 cases of salmonellosis occur every year in humans, resulting in 17 deaths. In the United States, it is estimated that 26,500 hospitalizations and 420 deaths occur every year. In dairy cattle, infections caused by nontyphoidal Salmonella enterica can cause mild to severe disease, including enteritis, pneumonia, and septicemia. Our study objectives were to determine the proportion of fecal samples positive for Salmonella in dairy cattle in Canada and determine the resistance pattern of these isolates. We used data collected through the Canadian Dairy Network for Antimicrobial Stewardship and Resistance (CaDNetASR). Pooled fecal samples from preweaning calves, postweaning heifers, lactating cows, and manure storage were cultured for Salmonella, and the isolates were identified using matrix-assisted laser desorption/ionization-time of flight mass spectrometry. Antimicrobial susceptibilities were determined using the minimum inhibitory concentration test, and resistance interpretation was made according to the Clinical and Laboratory Standards Institute. A 2-level, multivariable logistic regression model was built to determine the probability of recovering Salmonella from a sample, accounting for province, year, and sample source. The proportion of farms with at least one positive sample were 12% (17/140), 19% (28/144), and 17% (24/144) for the sampling years 2019, 2020, and 2021, respectively. Out of the 113 Salmonella isolates, 23 different serovars were identified. The occurrence of Salmonella appeared to be clustered by farms and provinces. The most common serovars identified were Infantis (14%) and Typhimurium (14%). Overall, 21% (24/113) of the Salmonella isolates were resistant to at least one antimicrobial. Resistance to tetracycline was commonly observed (17%); however, very limited resistance to category I antimicrobials (categorization according to Health Canada that includes third-generation cephalosporins, fluoroquinolones, polymyxins, and carbapenems) was observed, with one isolate resistant to amoxicillin and clavulanic acid. The proportion of Salmonella isolates resistant to 2 and 3 antimicrobial classes was 3.5% and 8.8%, respectively. Our study provided valuable information on the proportion of fecal samples positive for Salmonella, the serovars identified, and the associated resistance patterns across CaDNetASR herds, at regional and national levels.

Surveillance of Antimicrobial Prescriptions in Community Pharmacies Located in Tokyo, Japan.

An antimicrobial resistance (AMR) Action Plan was launched in 2016 to prevent the spread of antimicrobial-resistant bacteria in Japan. Additional support for the appropriate use of pediatric antimicrobial agents was initiated in 2018 to promote the appropriate use of antimicrobial agents in the community. To evaluate the effectiveness of the AMR Action Plan in the community, we investigated antimicrobial prescriptions in community pharmacies. Data on prescriptions for antimicrobial agents dispensed in 42 community pharmacies located in the Tama district, Tokyo, Japan, were collected between April 2013 and December 2019. In this study, we employed the DPY, which was calculated as defined daily doses (DDDs)/1000 prescriptions/year. The DPY is the number of antimicrobial agents used (potency) per 1000 antimicrobial prescriptions dispensed in pharmacies per year. The number of prescriptions for third-generation cephalosporins, fluoroquinolones, and macrolides decreased after the initiation of the AMR Action Plan; the DPYs of these antimicrobial agents decreased significantly by 31.4%, increased by 15.8%, and decreased by 23.6%, respectively (p < 0.05). The number of antimicrobial prescriptions for pediatric patients has been decreasing since 2018. Declines in the DPYs of third-generation cephalosporins, fluoroquinolones, and macrolides were higher in pediatric pharmacies than in other pharmacies. Our data suggest that the AMR Action Plan and additional support for the appropriate use of antimicrobial agents in children influenced the number of antimicrobial prescriptions in community pharmacies in Japan.

Intramammary and systemic use of antimicrobials and their association with resistance in generic Escherichia coli recovered from fecal samples from Canadian dairy herds: A cross-sectional study.

Antimicrobial resistance (AMR) in animals, including dairy cattle, is a significant concern for animal and public health worldwide. In this study, we used data collected through the Canadian Dairy Network for Antimicrobial Stewardship and Resistance (CaDNetASR) to: (1) describe the proportions of AMR in fecal E. coli, and (2) investigate the relationship between antimicrobial use (AMU) (intramammary and systemic routes, while accounting for confounding by other variables) and AMR/multidrug resistance (MDR - resistance to ≥ 3 antimicrobial classes) in fecal E. coli from Canadian dairy farms. We hypothesized that an increase of the AMU was associated with an increase in AMR in E. coli isolates. A total of 140 dairy farms across five provinces in Canada were included in the study. Fecal samples from pre-weaned calves, post-weaned heifers, lactating cows, and farm manure storage were cultured, and E. coli isolates were identified using MALDI-TOF MS. The minimum inhibitory concentrations (MIC) to 14 antimicrobials were evaluated using a microbroth dilution methodology. AMU was quantified in Defined Course Dose (DCD - the dose for a standardized complete treatment course on a standard size animal) and converted to a rate indicator - DCD/100 animal-years. Of 1134 fecal samples collected, the proportion of samples positive for E. coli in 2019 and 2020 was 97.1% (544/560) and 94.4% (542/574), respectively. Overall, 24.5% (266/1086) of the E. coli isolates were resistant to at least one antimicrobial. Resistance towards tetracycline was commonly observed (20.7%), whereas resistance to third-generation cephalosporins, fluoroquinolones, and carbapenems was found in 2.2%, 1.4%, and 0.1% of E. coli isolates, respectively. E. coli isolates resistant to two or ≥3 antimicrobial classes (MDR) was 2.7% and 15%, respectively. Two multilevel models were built to explore risk factors associated with AMR with AMU being the main exposure. Systemic AMU was associated with increased E. coli resistance. For an increase in systemic AMU equivalent to its IQR, the odds of resistance to any antimicrobial in the model increased by 18%. Fecal samples from calves had higher odds of being resistant to any antimicrobial when compared to other production ages and farm manure storage. The samples collected in 2020 were less likely to be resistant when compared to samples collected in 2019. Compared to previous studies in dairy cattle in North America, AMR in E. coli was lower.

Novel drug-drug salts of enoxacin with enhanced antibacterial activity: Insights from solubility and lipid-water partition coefficient

Enoxacin (ENX), a third-generation fluoroquinolone, demonstrates broad-spectrum antibacterial activities and is widely applied for the treatment of various bacterial infections. However, it is challenging to improve its antibacterial activity and drug resistance effects based on solubility changes owing to ENX being categorized as a class II drug in the Biopharmaceutics Classification System (BCS). In this experiment, three novel salts formed between ENX and non-steroidal anti-inflammatory drugs (NSAIDs) involving diclofenac (ENX-DFA), flufenamic acid (ENX-FFA) and niflumic acid (ENX-NFA) were firstly synthesized and then characterized. X-ray diffraction, thermodynamic analysis and infrared spectroscopy confirmed the salt formation. Interestingly, all the new salts demonstrated superior antibacterial activities against Escherichia coli (E. coli), Shigella flexneri (Sh. flexneri), Staphylococcus aureus (S. aureus) and Staphylococcus albicans (S. albus) compared with ENX. Further investigation of the pharmaceutical properties of the three salts revealed that they possessed lower aqueous solubility and intrinsic dissolution compared with ENX but exhibited better solubility than the three NSAIDs. Moreover, our results demonstrated that fluctuations in the solubility of ENX salts were pH-dependent. Thus, the solubility changes of ENX salts were assessed using pH-window diagrams. The order of lipid-water partition coefficient (P) was consistent with antibacterial performance (ENX-FFA > ENX-DFA > ENX-NFA > ENX) and was 2.04, 1.95, and 1.69 times greater than that of ENX, indicating that the higher LogP values of salts with strong cell membrane penetration ability improved the efficacy of the drug to inhibit bacterial growth. In summary, this study provides new insights to elucidate antibacterial effects from solubility and LogP values.

1364-P: Cinicoradiological and Microbial Spectrum of Skull Base Osteomyelitis and Its relation to Diabetes Mellitus

Skull base osteomyelitis (SBO) is a rare life-threatening disease, which is on the increase specifically the incidence of fungal skull base osteomyelitis. Objectives: To describe the demographic, and clinicoradiological profile, and to assess the outcome of skull base osteomyelitis. Methodology: A prospective study from a tertiary care centre, in Kerala from 1st February 2018 to 31st August 2019 with a minimum follow-up of 6 months. All patients diagnosed with skull base osteomyelitis were included. The demographic profile and relevant investigations, radiological correlations and treatment outcomes were analysed. Results and Discussions: 30 patients (23 males and 7 females) were studied. Incidence was found to be high in the age group 51-60 years. The mean (SD) of Age (Years) was 62.02 (14.21), ranging from 1.5-78 years. The most common presentation was a nocturnal earache (86.7%).13.3% of patients presented with headache alone, these cases were diagnosed to be central skull base osteomyelitis and had a significant association with clival erosion. All the patients were having diabetes mellitus except 1.5 yrs old who had congenital cyclic neutropenia. We could see an association between uncontrolled blood glucose and the severity of the disease (P value &amp;lt;0.001). 63.3% of the participants had Cranial Nerve Palsy at the presentation. The culture yielded Pseudomonas followed by staphylococcus aureus, MRSA &amp; Aspergillus. The ESR and CRP levels were reliable for the detection, progression and resolution of disease status in SBO. All patients were treated with third-generation cephalosporins and fluoroquinolones for a minimum of 6 weeks and of which, 12 patients with fungal SBO were given antifungals also. Conclusions: Skull base osteomyelitis is an entity that requires a lifelong commitment. A high index of suspicion, early diagnosis, and prompt and aggressive management are critical for a positive outcome. Uncontrolled diabetes mellitus was the risk factor recognised. Disclosure S.Radhakrishnan: None. D.C: None. V.Dahiya: None. C.R: None.

Decline in Antimicrobial Consumption and Stagnation in Reducing Disease Burden due to Antimicrobial Resistance in Japan.

Antimicrobial resistance (AMR) is a major global health threat. While antimicrobial consumption (AMC) in Japan substantially decreased after implementation of the AMR National Action Plan, the disease burden due to AMR seems to be unchanged. The main objective of this study is to examine the relationship between AMC and the disease burden due to AMR in Japan. We estimated the annual population-standardized AMC from 2015 to 2021 using defined daily doses (DDDs) per 1000 inhabitants per day (DIDs) and the disease burden due to bloodstream infections caused by nine major antimicrobial-resistant bacteria (AMR-BSIs) from 2015 to 2021 using disability-adjusted life years (DALYs). We then examined the correlation between AMC and DALYs using Spearman's rank correlation coefficient and cross-correlation function. Spearman's [Formula: see text] > 0.7 was considered to indicate a strong correlation. The sales amounts of third-generation cephalosporins, fluoroquinolones, and macrolides were 3.82 DIDs, 2.71 DIDs, and 4.59 DIDs, respectively, in 2015, but 2.11, 1.48, and 2.72 in 2021. This corresponded to reductions of 44.8%, 45.4%, and 40.7% during the study period. DALYs due to AMR-BSIs were 164.7 per 100,000 population in 2015 but 195.2 per 100,000 in 2021. Spearman's rank correlation coefficients between AMC and DALYs were-0.37 (total antibiotics),-0.50 (oral antibiotics),-0.43 (third-generation cephalosporins),-0.5 (fluoroquin,olones) and-0.5 (macrolides). No obvious cross-correlations were found. Our results reveal that changes in AMC are not associated with DALYs caused by AMR-BSIs. AMR countermeasures besides efforts to reduce inappropriate AMC might be necessary to mitigate the disease burden due to AMR.

Molecular ecology of highest priority critically important antibiotic resistant Escherichia coli from mammals housed at an urban zoo.

Zoos are environments where species of highly valued animals are kept largely separated from others and the wider world. We report the molecular ecology of critically important antibiotic resistant (ABR) Escherichia coli carried by 28 mammalian species housed in a zoo located in an urban residential district. Over 3 months we collected 167 faecal samples from captive mammals and processed for E. coli resistant to third-generation cephalosporins (3GC-R) and fluoroquinolones (FQ-R). Isolates were sequenced using Illumina. We identified high rates of faecal sample-level positivity, with 50%, 57% and 36% of mammalian species excreting 3GC-R, FQ-R or dual 3GC-R/FQ-R E. coli, respectively. Isolates represented multiple ST and ABR mechanisms; CTX-M-15 and CMY-2 dominated for 3GC-R, and target-site mutation caused 75% of FQ-R. We identified multiple examples of ABR E. coli transmission between mammalian species in separate enclosures, and a variant of the epidemic plasmid pCT within the zoo. There was no evidence for ABR E. coli leaving the zoo, based on comparative analysis with E. coli from humans, cattle and dogs isolated from the 50 × 50 km region in which the zoo is located. Amoxicillin/clavulanate was the most widely used antibiotic in the zoo, and we identified four widely disseminated amoxicillin/clavulanate resistance mechanisms, including a previously unreported inhibitor-resistant TEM, and the carbapenemase OXA-181. We conclude that the zoo studied here is a 'melting pot' for the selection and circulation of 3GC-R and FQ-R E. coli, but these circulating E. coli appear captive within the zoo.

The manganese(II) and cobalt(II) complexes of enrofloxacin showed comparable antibacterial activity: Synthesis, crystal structure and antibacterial activity

Enrofloxacin (EFX) is a third-generation fluoroquinolone drug especially used for animals world wide, which shows broad-spectrum and significant antibacterial activities. In this study, EFX was selected as the ligand to synthesize two transition metal complexes, EFX-Mn and EFX-Co, in which the bio-active metal ions, manganese(II) and cobalt(II), was set to be the active metal center. Their crystal structures were reported and characterized by X-ray single crystal diffraction analysis. Both the crystal structures of EFX-Mn and EFX-Co belong to the same monoclinic crystal system with P21/c space group. Viewed from the crystal structure of EFX-Mn or EFX-Co, the central Mn(II)/Co(II) adapted a six-coordinated octahedral configuration, respectively by two EFX ligands and two H2O co-ligands. The characteristic UV-Vis absorption peaks of both complexes were examined in tris-saline buffer solution in a time-dependent mode in 24 h, which suggested that the coordination status of EFX-Mn and EFX-Co in the solid state still maintained under near-physiological condition. In vitro antibacterial activity tests demonstrated that EFX-Mn and EFX-Co showed similar and significant growth inhibitory effects towards five typical pathogenic bacteria, compared with EFX itself. While for two gram-negative bacterial strains, E. coli and S. typhi, EFX-Mn and EFX-Co showed higher bactericidal effects than EFX, the bactericidal concentration of which was only a half as low as that of EFX.