[Cefiderocol: a first and novel class of siderophore cephalosporin for Carbapenem-resistant Gram-negative infection].

Antimicrobial resistance is currently recognized as an urgent concern against public health in worldwide. Carbapenem-resistant (CR) Gram-negative bacteria, such as Enterobacterales, Pseudomonas aeruginosa and Acinetobacter baumannii are listed as critical pathogens which are widely spread and can cause severe and often deadly infections in WHO guidance. Cefiderocol (Fetroja®), a novel and first siderophore cephalosporin, was approved for the infections caused by these problematic CR Gram-negative bacteria in Japan on November 30, 2023. Cefiderocol has unique mechanisms to be incorporated into bacterial cells using bacterial iron transportation system and to be highly stable against most ß-lactamases, which lead to promising antibacterial activity against these Gram-negative bacteria including CR strains in vitro. In CREDIBLE-CR Ph3 trial, cefiderocol showed the good efficacy and safety for patients with CR Gram-negative bacteria. In APEKS-cUTI and APEKS-NP trials, cefiderocol showed non-inferiority and suggested superiority to imipenem/cilastatin in complicated urinary tract infection (cUTI) patients, and non-inferiority to high dose of meropemen in pneumonia patients, respectively. Cefiderocol is expected to be an optimal treatment for CR Gram-negative infections with limited treatment options and would be an important drug to combat the threat of CR bacteria.

Prevalence of streptomycin and tetracycline resistance and increased transmissible third-generation cephalosporin resistance in Salmonella enterica isolates derived from food handlers in Japan from 2006 to 2021.

AIMS: The increasing prevalence of AmpC ß-lactamase (AmpC)- and extended-spectrum ß-lactamase (ESBL)- producing food pathogens is a serious public health concern. AmpC- and ESBL-producing Salmonella species pose a high risk of food contamination. This study aimed to investigate changes in the prevalence of Salmonella among food handlers in Japan from 2006 to 2021 using 100 randomly selected isolates from 2006, 2012, 2018, and 2021 with different serotypes and antimicrobial resistance patterns. METHODS AND RESULTS: The average Salmonella isolation rate was 0.070% (19 602/27 848 713). Serotyping revealed that the most common serotypes were Enteritidis in 2006, Infantis in 2012, Agoueve/Cubana in 2018, and Schwarzengrund in 2021. Antimicrobial susceptibility testing showed that Salmonella isolates exhibited the highest resistance to streptomycin (<40%), followed by tetracycline (<20%-40%). Moreover, 6% of the Salmonella isolates produced cephalosporinases with the blaCMY-2, blaCTX-M-14, and blaTEM genes. The annual incidence of cephalosporin resistance has increased. Plasmid conjugation assays revealed that cephalosporin-resistant Salmonella spp. transmitted their resistance to Escherichia coli. Additionally, plasmid genome analysis showed that the insertion sequence IS26 was encoded in the upstream and downstream regions of blaCTX-M-14 and qnrS1 in the IncHI1 plasmid, which could be transmitted to other bacteria. CONCLUSIONS: The tested Salmonella isolates showed high resistance to specific antibiotics, with differences in resistance depending on the serotype. Further increase and spread of transmissible cephalosporin-resistant strains should be noted.

Molecular characterization of clinically isolated Pseudomonas aeruginosa with varying resistance to ceftazidime-avibactam and ceftolozane-tazobactam collected as a part of the ATLAS global surveillance program from 2020 to 2021.

Ceftazidime-avibactam (CZA) and ceftolozane-tazobactam (C/T) are important agents for treating multidrug-resistant P. aeruginosa infections. In this study, we evaluated the molecular characteristics of 300 globally collected clinical P. aeruginosa isolates non-susceptible (NS) to CZA, C/T, or both agents. Isolates were CZA-NS and C/T-NS (n = 57), CZA-susceptible (S) and C/T-NS (n = 145), or CZA-NS and C/T-S (n = 98) selected from the Antimicrobial Testing Leadership and Surveillance (ATLAS) surveillance program from 2020 to 2021. Characterization was by whole-genome sequencing. Analysis was performed to identify ß-lactamase genes and mutations that impact efflux regulation, AmpC regulation, and target binding (PBP3). Of the 57 CZA-NS+C/T-NS isolates, 64.9% carried a metallo-ß-lactamase (MBL), and a cumulative 84.2% carried any non-intrinsic ß-lactamase [i.e., not Pseudomonas-derived cephalosporinase (PDC) or OXA-50-like]. Of the 145 CZA-S+C/T-NS isolates, 26.2% carried an extended-spectrum ß-lactamase (ESBL) and no carbapenemase, 17.9% carried a serine-carbapenemase, and 42.1% were negative for non-intrinsic ß-lactamases. Of 98 CZA-NS+C/T-S isolates, 34.7% carried mutations previously described as causing an upregulation of the MexAB-OprM efflux pump, while only 9.2% carried a non-intrinsic ß-lactamase, and no resistance mechanism was identified in 29.6% of these isolates. MBLs were present in most isolates NS to both agents. More than half of the CZA-S+C/T-NS isolates carried serine ß-lactamases. The most frequently identified resistance mechanism identified in CZA-NS+C/T-S isolates was a marker indicating the upregulation of MexAB-OprM. No mechanism was identified that is thought to support resistance to these agents in numerous isolates. This may be due in part to the fact that whole genome sequencing (WGS) cannot directly measure gene expression of chromosomal resistance mechanisms.

Synergistic antimicrobial combination of third-generation cephalosporins and polymyxin B against carbapenem-polymyxin-resistant Klebsiella pneumoniae: an in vitro and in vivo analysis.

Antibiotic combination therapy is a promising approach to address the urgent need for novel treatment options for infections caused by carbapenem-polymyxin-resistant Klebsiella pneumoniae (CPR-Kp). The present study aimed to investigate the synergistic potential of four cephalosporins in combination with polymyxin B (PMB). A checkerboard assay was performed to evaluate the synergistic effects of cephalexin (CLX), cefixime, cefotaxime (CTX), and cefmenoxime (CMX) in combination with PMB. Subsequently, experiments evaluating the use of CTX or CMX in combination with PMB (CTX-PMB or CMX-PMB, respectively), including growth curve and SynergyFinder analysis, antibiofilm activity assays, cell membrane integrity assays, and scanning electron microscopy, were performed. Safety assessments were also conducted, including hemolysis and toxicity evaluations, using Caenorhabditis elegans. Furthermore, an in vivo model in C. elegans was adopted to assess the treatment efficacy against CPR-Kp infections. CTX-PMB and CMX-PMB exhibited low fractional inhibitory concentration indexes ranging from 0.19 to 0.50 and from 0.25 to 1.5, respectively, and zero interaction potency scores of 37.484 and 15.076, respectively. The two combinations significantly reduced growth and biofilm formation in CPR-Kp. Neither CTX-PMB nor CMX-PMB compromised bacterial cell integrity. Safety assessments revealed a low hemolysis percentage and high survival rates in the C. elegans toxicity evaluations. The in vivo model revealed that the CTX-PMB and CMX-PMB treatments improved the survival rates of C. elegans. The synergistic effects of the CTX-PMB and CMX-PMB combinations, both in vitro and in vivo, indicate that these antibiotic pairings could represent effective therapeutic options for infections caused by CPR-Kp.

Characterization of acquired ß-lactamases in Pseudomonas aeruginosa and quantification of their contributions to resistance.

Pseudomonas aeruginosa is a highly problematic opportunistic pathogen that causes a range of different infections. Infections are commonly treated with ß-lactam antibiotics, including cephalosporins, monobactams, penicillins, and carbapenems, with carbapenems regarded as antibiotics of last resort. Isolates of P. aeruginosa can contain horizontally acquired bla genes encoding ß-lactamase enzymes, but the extent to which these contribute to ß-lactam resistance in this species has not been systematically quantified. The overall aim of this research was to address this knowledge gap by quantifying the frequency of ß-lactamase-encoding genes in P. aeruginosa and by determining the effects of ß-lactamases on susceptibility of P. aeruginosa to ß-lactams. Genome analysis showed that ß-lactamase-encoding genes are present in 3% of P. aeruginosa but are enriched in carbapenem-resistant isolates (35%). To determine the substrate antibiotics, 10 ß-lactamases were expressed from an integrative plasmid in the chromosome of P. aeruginosa reference strain PAO1. The ß-lactamases reduced susceptibility to a variety of clinically used antibiotics, including carbapenems (meropenem, imipenem), penicillins (ticarcillin, piperacillin), cephalosporins (ceftazidime, cefepime), and a monobactam (aztreonam). Different enzymes acted on different ß-lactams. ß-lactamases encoded by the genomes of P. aeruginosa clinical isolates had similar effects to the enzymes expressed in strain PAO1. Genome engineering was used to delete ß-lactamase-encoding genes from three carbapenem-resistant clinical isolates and increased susceptibility to substrate ß-lactams. Our findings demonstrate that acquired ß-lactamases play an important role in ß-lactam resistance in P. aeruginosa, identifying substrate antibiotics for a range of enzymes and quantifying their contributions to resistance.IMPORTANCEPseudomonas aeruginosa is an extremely problematic pathogen, with isolates that are resistant to the carbapenem class of ß-lactam antibiotics being in critical need of new therapies. Genes encoding ß-lactamase enzymes that degrade ß-lactam antibiotics can be present in P. aeruginosa, including carbapenem-resistant isolates. Here, we show that ß-lactamase genes are over-represented in carbapenem-resistant isolates, indicating their key role in resistance. We also show that different ß-lactamases alter susceptibility of P. aeruginosa to different ß-lactam antibiotics and quantify the effects of selected enzymes on ß-lactam susceptibility. This research significantly advances the understanding of the contributions of acquired ß-lactamases to antibiotic resistance, including carbapenem resistance, in P. aeruginosa and by implication in other species. It has potential to expedite development of methods that use whole genome sequencing of infecting bacteria to inform antibiotic treatment, allowing more effective use of antibiotics, and facilitate the development of new antibiotics.

Antibiotics stimulates the development of persistent cells in biofilms of Candida albicans bloodstream isolates.

Candida albicans invasive candidiasis is considered a global health problem. In such cases, biofilm formation on implanted devices represents a therapeutic challenge and the presence of metabolically inactive persistent cells (PCs) in these communities increases their tolerance to fungicidal drugs. This study investigated the influence of amoxicillin, AMX; cefepime, CEF; gentamicin, GEN; amikacin, AMK; vancomycin, VAN; and ciprofloxacin, CIP; on the production of PCs in biofilms of C. albicans bloodstream isolates. 48 h-mature biofilms (n = 6) grown in RPMI-1640 supplemented with antibiotics were treated with 100 µg ml-1 amphotericin B and then evaluated for PCs. Biofilms grown in the presence of antibiotics produced more PCs, up to 10×, when exposed to AMX and CIP; 5 × to CEF; and 6 × to GEN and VAN. The results indicate that antibiotics can modulate PC production in C. albicans biofilms. This scenario may have clinical repercussions in immunocompromised patients under broad-spectrum antibiotic therapy.

Biofilms are microbial communities tolerant to antifungals. Our research showed that antibiotics stimulate the formation of persistent cells within Candida albicans biofilms. These are dormant, metabolically silent cells that resist to therapy and can be related to metastatic and recalcitrant infections.

Genetic traits and transmission of antimicrobial resistance characteristics of cephalosporin resistant Escherichia coli in tropical aquatic environments.

This study investigates the genetic traits and transmission mechanisms of cephalosporin-resistant Escherichia coli in tropical aquatic environments in Singapore. From 2016 to 2020, monthly samples were collected from wastewater treatment plants, marine niches, community sewage, beaches, reservoirs, aquaculture farms, and hospitals, yielding 557 isolates that were analyzed for antimicrobial resistance genes (ARGs) and mobile genetic elements (MGEs) using genomic methods. Findings reveal significant genotypic similarities between environmental and hospital-derived strains, particularly the pandemic E. coli ST131. Environmental strains exhibited high levels of intrinsic resistance mechanisms, including mutations in porins and efflux pumps, with key ARGs such as CMY-2 and NDM-9 predominantly carried by MGEs, which facilitate horizontal gene transfer. Notably, pathogenic EPEC and EHEC strains were detected in community sewage and aquaculture farms, posing substantial public health risks. This underscores the critical role of these environments as reservoirs for multidrug-resistant pathogens and emphasizes the interconnectedness of human activities and environmental health.

Effects of adding antibiotics to an inactivated oil-adjuvant avian influenza vaccine on vaccine characteristics and chick health.

During poultry immunization, antibiotics are typically added to inactivated oil-adjuvant avian influenza (AI) vaccines. Here, we evaluated the effects of adding ceftiofur, a third-generation cephalosporin, to an AI vaccine on vaccine stability and structure and on chick growth, immune efficacy, blood concentrations, biochemical and immunological indices, and gut microbiota. The results demonstrated that neither aqueous ceftiofur sodium nor ceftiofur hydrochloride oil emulsion formed a stable mixture with the vaccine. Adding ceftiofur formulations, particularly ceftiofur hydrochloride, at >4% significantly destabilized the vaccine's water-in-oil structures. Adding ceftiofur also increased vaccine malabsorption at the injection site; specifically, adding ceftiofur hydrochloride reduced H5N8 and H7N9 antibody titers after the first immunization (P < 0.05) and H7N9 antibody titers after the second immunization (P < 0.01). Serum drug concentrations did not differ significantly between the groups with ceftiofur sodium and hydrochloride addition. Ceftiofur addition increased postvaccination chick weight loss; compared with the vaccine alone, ceftiofur sodium-vaccine mixture increased chick weight significantly (P < 0.05). Ceftiofur addition also increased stress indices and reduced antioxidant capacity significantly (P < 0.05 or P < 0.01). Vaccination-related immune stress reduced gut microbiota diversity in chicks; ceftiofur addition reversed this change. AI vaccine immunization significantly reduced the relative abundance of Lactobacillus and Muribaculaceae but significantly increased that of Bacteroides and Eubacterium coprostanoligenes group. Ceftiofur addition restored the gut microbiota structure; in particular, ceftiofur hydrochloride addition significantly increased the abundance of the harmful gut microbes Escherichia-Shigella and Enterococcus, whereas ceftiofur sodium addition significantly reduced it. The changes in gut microbiota led to alterations in metabolic pathways related to membrane transport, amino acids, and carbohydrates. In conclusion, adding ceftiofur to the AI vaccine had positive effects on chick growth and gut microbiota modulation; however, different antibiotic concentrations and formulations may disrupt vaccine structure, possibly affecting vaccine safety and immunization efficacy. Thus, the addition of antibiotics to oil-adjuvant vaccines is associated with a risk of immunization failure and should be applied to poultry with caution.

The relationship between resistance evolution and carbon metabolism in Staphylococcus xylosus under ceftiofur sodium stress.

Staphylococcus xylosus has emerged as a bovine mastitis pathogen with increasing drug resistance, resulting in substantial economic impacts. This study utilized iTRAQ analysis to investigate the mechanisms driving resistance evolution in S. xylosus under ceftiofur sodium stress. Findings revealed notable variations in the expression of 143 proteins, particularly glycolysis-related proteins (TpiA, Eno, GlpD, Ldh) and peptidoglycan (PG) hydrolase Atl. Following the induction of ceftiofur sodium resistance in S. xylosus, the emergence of resistant strains displaying characteristics of small colony variants (SCVs) was observed. The transcript levels of TpiA, Eno, GlpD and Ldh were up-regulated, TCA cycle proteins (ICDH, MDH) and Atl were down-regulated, lactate content was increased, and NADH concentration was decreased in SCV compared to the wild strain. That indicates a potential role of carbon metabolism, specifically PG hydrolysis, glycolysis, and the TCA cycle, in the development of resistance to ceftiofur sodium in S. xylosus.

Pharmacodynamics of taniborbactam in combination with cefepime studied in an in vitro model of infection.

OBJECTIVES: To define the in vitro pharmacodynamics of taniborbactam against Enterobacterales with CTXM-15, KPC, AmpC, and OXA-48 ß-lactamases. METHODS: An in vitro pharmacokinetic model was used to simulate serum concentrations associated with cefepime 2G by 1 h infusion 8 h. Taniborbactam was given in exposure ranging and fractionation simulations. Reduction in viable count at 24 h (Δ 24) was the primary end point and four strains were used: Escherichia coli expressing CTXM-15 or AmpC and Klebsiella pneumoniae expressing KPC or OXA-48 enzymes. RESULTS: Taniborbactam was administered as continuous infusions; ≥4 log kill was attained with taniborbactam concentrations of ≥0.01 mg/L against CTXM-15 E. coli, ≥0.5 mg/L against KPC- and OXA-48 K. pneumoniae, and ≥4 mg/L against AmpC E. coli. Analyses were conducted to determine the pharmacokinetic/dynamic driver for each strain. For E. coli (CTXM-15) and E. coli (AmpC), area under the concentration-time curve (AUC) was best related to change in viable count (R20.74 and 0.72, respectively). For K. pneumoniae (KPC) AUC and T > 0.25 mg/L were equally related to bacterial clearance (R20.72 for both), and for K. pneumoniae (OXA-48) T > 0.25 mg/L was the best predictor (R20.94). The taniborbactam AUC range to produce a 1-log10 reduction in viable count was 4.4-11.2 mg·h/L. Analysis of data from all strains indicated T > MIC divided by 4 was best related to change in viable count; however, curve fit was poor R2 < 0.49. CONCLUSIONS: Taniborbactam was effective in combination with cefepime in producing bacterial clearance for B lactam resistant Enterobacterales. The primary pharmacodynamic driver was AUC or time > threshold, both being closely related to antibacterial effect.

Preparation of ceftiofur-encapsulated hen-egg low-density lipoproteins and their antibacterial effects on intracellular Staphylococcus aureus.

Hen egg low-density lipoprotein (heLDL), as alternative of serum-derived LDL, was used as drug delivery system of ceftiofur (CEF). The CEF-loaded hen egg low-density lipoprotein (CEF-heLDL) with complete apolipoprotein structure and high drug loading rate was synthesized, possesses suitable particle size. CEF-heLDL undergoes cellular uptake and colocalizes with lysosomes in vitro. An intracellular infection model of the bovine endometrial epithelial cells and a coeliac-induced inflammation model of mice by Staphylococcus aureus (S. aureus) were established, and significantly lower intracellular S. aureus levels of CEF-heLDL group than CEF-free group (P < 0.001) was observed. The antibacterial efficacy was sustained for 24 h. Up to 400 mg/kg of CEF-heLDL, 20 times the clinical practice, were intraperitoneally administrated, and no significant toxicity signs on mice were observed. HeLDLs is an effective, safe, and cheap drug carrier, and could also be used for transmembrane delivering other antibiotics.

Neisseria gonorrhoeae isolates resistant to extended spectrum cephalosporins and macrolides isolated from symptomatic men in western Kenya.

BACKGROUND: We characterized the antimicrobial resistance (AMR) profiles of Neisseria gonorrhoeae (NG) isolated from symptomatic men at a sexually transmitted infection clinic in Kisumu, Kenya. METHODS: Two urethral swabs were obtained from symptomatic men between 2020 and 2022, one for Gram's stain and the other inoculated directly onto modified Thayer-Martin media containing 1% VCNT and 1% IsoVitaleX enrichment. Culture results were confirmed by colony morphology, Gram's stain and oxidase test. Duplicate isolates were shipped to Uniformed Services University for confirmation and characterization. Susceptibility to eight drugs was assessed by E-test. Agar dilution confirmed resistance to ceftriaxone, cefixime, and azithromycin. Susceptibility, intermediate resistance (IR), and resistance (R) were determined according to published criteria. RESULTS: Of 154 enrolled participants, 112 were culture-positive for NG. Agar dilution results in 110 (98.2%) showed the following: azithromycin-R (1.8%), and 4.5% R or IR to ceftriaxone or cefixime: ceftriaxone-R (0.9%), ceftriaxone-IR (2.7%), and cefixime-IR (2.7%). By E-test, most isolates were IR or R to tetracycline (97.2%), penicillin (90.9%), and ciprofloxacin (95.4%). CONCLUSIONS: We detected NG with resistance to azithromycin and ceftriaxone, indicating a growing threat to the current Kenyan dual syndromic treatment of urethritis with cephalosporin plus macrolides. Ongoing AMR surveillance is essential for effective drug choices.

Hetero-antagonism of avibactam and sulbactam with cefiderocol in carbapenem-resistant Acinetobacter spp.

Cefiderocol, a siderophore-cephalosporine conjugate antibiotic, shows promise as a therapeutic option for carbapenem-resistant (CR) Acinetobacter infections. While resistance has already been reported in A. baumannii, combination therapies with avibactam or sulbactam reduce MICs of cefiderocol, extending its efficacy. However, careful consideration is necessary when using these combinations. In our experiments, exposure of A. baumannii and A. lwoffii to cefiderocol and sulbactam or avibactam led to the selection of cefiderocol-resistant strains. Three of those were subjected to whole genome sequencing and transcriptomic analysis. The strains all possessed synonymous and non-synonymous substitutions and short deletions. The most significant mutations affected efflux pumps, transcriptional regulators, and iron homeostasis genes. Transcriptomics showed significant alterations in expression levels of outer membrane proteins, iron homeostasis, and ß-lactamases, suggesting adaptive responses to selective pressure. This study underscores the importance of carefully assessing drug synergies, as they may inadvertently foster the selection of resistant variants and complicate the management of CR Acinetobacter infections.IMPORTANCEThe emergence of carbapenem-resistant Acinetobacter strains as a serious global health threat underscores the urgent need for effective treatment options. Although few drugs show promise against CR Acinetobacter infections, resistance to both drugs has been reported. In this study, the molecular characterization of spontaneous cefiderocol-resistant variants, a CR A. baumannii strain with antagonism to sulbactam, and an A. lwoffii strain with antagonism to avibactam, provides valuable insights into the mechanisms of resistance to cefiderocol. Some mechanisms observed are associated with mutations affecting efflux pumps, regulators, and iron homeostasis genes. These findings highlight the importance of understanding resistance mechanisms to optimize treatment options. They also emphasize the importance of early evaluation of drug synergies to address the challenges of antimicrobial resistance in Acinetobacter infections.

ARGONAUT-III and -V: susceptibility of carbapenem-resistant Klebsiella pneumoniae and multidrug-resistant Pseudomonas aeruginosa to the bicyclic boronate ß-lactamase inhibitor taniborbactam combined with cefepime.

Taniborbactam, a bicyclic boronate ß-lactamase inhibitor with activity against Klebsiella pneumoniae carbapenemase (KPC), Verona integron-encoded metallo-ß-lactamase (VIM), New Delhi metallo-ß-lactamase (NDM), extended-spectrum beta-lactamases (ESBLs), OXA-48, and AmpC ß-lactamases, is under clinical development in combination with cefepime. Susceptibility of 200 previously characterized carbapenem-resistant K. pneumoniae and 197 multidrug-resistant (MDR) Pseudomonas aeruginosa to cefepime-taniborbactam and comparators was determined by broth microdilution. For K. pneumoniae (192 KPC; 7 OXA-48-related), MIC90 values of ß-lactam components for cefepime-taniborbactam, ceftazidime-avibactam, and meropenem-vaborbactam were 2, 2, and 1 mg/L, respectively. For cefepime-taniborbactam, 100% and 99.5% of isolates of K. pneumoniae were inhibited at ≤16 mg/L and ≤8 mg/L, respectively, while 98.0% and 95.5% of isolates were susceptible to ceftazidime-avibactam and meropenem-vaborbactam, respectively. For P. aeruginosa, MIC90 values of ß-lactam components of cefepime-taniborbactam, ceftazidime-avibactam, ceftolozane-tazobactam, and meropenem-vaborbactam were 16, >8, >8, and >4 mg/L, respectively. Of 89 carbapenem-susceptible isolates, 100% were susceptible to ceftolozane-tazobactam, ceftazidime-avibactam, and cefepime-taniborbactam at ≤8 mg/L. Of 73 carbapenem-intermediate/resistant P. aeruginosa isolates without carbapenemases, 87.7% were susceptible to ceftolozane-tazobactam, 79.5% to ceftazidime-avibactam, and 95.9% and 83.6% to cefepime-taniborbactam at ≤16 mg/L and ≤8 mg/L, respectively. Cefepime-taniborbactam at ≤16 mg/L and ≤8 mg/L, respectively, was active against 73.3% and 46.7% of 15 VIM- and 60.0% and 35.0% of 20 KPC-producing P. aeruginosa isolates. Of all 108 carbapenem-intermediate/resistant P. aeruginosa isolates, cefepime-taniborbactam was active against 86.1% and 69.4% at ≤16 mg/L and ≤8 mg/L, respectively, compared to 59.3% for ceftolozane-tazobactam and 63.0% for ceftazidime-avibactam. Cefepime-taniborbactam had in vitro activity comparable to ceftazidime-avibactam and greater than meropenem-vaborbactam against carbapenem-resistant K. pneumoniae and carbapenem-intermediate/resistant MDR P. aeruginosa.

Community use of oral antibiotics transiently reprofiles the intestinal microbiome in young Bangladeshi children.

Antibiotics may alter the gut microbiome, and this is one of the mechanisms by which antimicrobial resistance may be promoted. Suboptimal antimicrobial stewardship in Asia has been linked to antimicrobial resistance. We aim to examine the relationship between oral antibiotic use and composition and antimicrobial resistance in the gut microbiome in 1093 Bangladeshi infants. We leverage a trial of 8-month-old infants in rural Bangladesh: 61% of children were cumulatively exposed to antibiotics (most commonly cephalosporins and macrolides) over the 12-month study period, including 47% in the first 3 months of the study, usually for fever or respiratory infection. 16S rRNA amplicon sequencing in 11-month-old infants reveals that alpha diversity of the intestinal microbiome is reduced in children who received antibiotics within the previous 7 days; these samples also exhibit enrichment for Enterococcus and Escherichia/Shigella genera. No effect is seen in children who received antibiotics earlier. Using shotgun metagenomics, overall abundance of antimicrobial resistance genes declines over time. Enrichment for an Enterococcus-related antimicrobial resistance gene is observed in children receiving antibiotics within the previous 7 days, but not earlier. Presence of antimicrobial resistance genes is correlated to microbiome composition. In Bangladeshi children, community use of antibiotics transiently reprofiles the gut microbiome.

Resistance to cephalosporins and quinolones in Escherichia coli isolated from irrigation water from the Rímac river in east Lima, Peru. / Resistencia a cefalosporinas y quinolonas en Escherichia coli aisladas de agua de riego del río Rímac en Lima Este, Perú.

OBJECTIVES.: To evaluate the presence and sensitivity to antimicrobials of Escherichia coli strains isolated from 24 irrigation water samples from the Rimac river of East Lima, Peru. MATERIALS AND METHODS.: The E. coli strains were identified by PCR. Antibiotic susceptibility was processed by the disk diffusion method. Genes involved in extended spectrum beta-lactamases (BLEE), quinolones and virulence were determined by PCR. RESULTS.: All samples exceeded the acceptable limits established in the Environmental Quality Standards for vegetable irrigation. Of the 94 isolates, 72.3% showed resistance to at least one antibiotic, 24.5% were multidrug resistant (MDR) and 2.1% were extremely resistant. The highest percentages of resistance were observed for ampicillin-sulbactam (57.1%), nalidixic acid (50%), trimethoprim-sulfamethoxazole (35.5%) and ciprofloxacin (20.4%). Among the isolates, 3.2% had a BLEE phenotype related to the bla CTX-M-15 gene. qnrB (20.4%) was the most frequent transferable mechanism of resistance to quinolones, and 2.04% had qnrS. It was estimated that 5.3% were diarrheagenic E. coli and of these, 60% were enterotoxigenic E. coli, 20% were enteropathogenic E. coli and 20% were enteroaggregative E. coli. CONCLUSIONS.: The results show the existence of diarrheogenic pathotypes in the water used for irrigation of fresh produce and highlight the presence of BLEE- and MDR-producing E. coli, demonstrating the role played by irrigation water in the dissemination of resistance genes in Peru.Motivation for the study. Aquatic systems, including irrigation water, have been identified as reservoirs of antimicrobial resistance, with few studies in Peru on the presence of Escherichia coli and their levels of virulence and antimicrobial resistance. Main findings. Our results show the presence of E. coli above the established standard for vegetable irrigation water, some with very high levels of antimicrobial resistance. Implications. The presence of ESBL-producing strains of extended-spectrum beta-lactamases and multidrug-resistant E. coli in irrigation water could contribute to the dissemination of resistance genes in Peru, posing a significant threat to public health.

Commercially available tests for determining cefiderocol susceptibility display variable performance in the Achromobacter genus.

BACKGROUND: Cefiderocol is a siderophore-conjugated cephalosporin increasingly used in the management of Achromobacter infections. Testing for cefiderocol susceptibility is challenging with distinct recommendations depending on the pathogens. OBJECTIVES: We evaluated the performance of commercial tests for testing cefiderocol susceptibility in the Achromobacter genus and reviewed the literature. METHODS: Diffusion (disks, MIC gradient test strips [MTS], Liofilchem) and broth microdilution (BMD) methods (ComASP™, Liofilchem; UMIC®, Bruker) were compared with the BMD reference method according to the EUCAST guidelines on 143 Achromobacter strains from 14 species with MIC50/90 of ≤ 0.015/0.5 mg/L. A literature search was conducted regardless of method or species. RESULTS: None of the methods tested fulfilled an acceptable essential agreement (EA). MTS displayed the lowest EA (30.8%) after UMIC® (49%) and ComASP™ (76.9%). All methods achieved an acceptable bias, with MICs either underestimated using MTS (-1.3%) and ComASP™ (-14.2%) or overestimated with UMIC® (+ 9.1%). Inhibition zone diameters ranged from 6 to 38 mm (IZD50/90=33/30 mm). UMIC® and ComASP™ failed to categorize one or the two cefiderocol-resistant strains of this study as resistant unlike the diffusion-based methods. The literature review highlighted distinct performance of the available methods according to pathogens and testing conditions. CONCLUSIONS: The use of MTS is discouraged for Achromobacter spp. Disk diffusion can be used to screen for susceptible strains by setting a threshold diameter of 30 mm. UMIC® and ComASP™ should not be used as the sole method but have to be systematically associated with disk diffusion to detect the yet rarely described cefiderocol-resistant Achromobacter sp. strains.

Predicting early appropriate therapy for patients infected by carbapenem-resistant Gram-negative pathogens in intensive care units in Italy.

BACKGROUND: Antibiotic resistance among Gram-negative bacteria in intensive care units (ICUs) is linked with high morbidity and mortality in patients. In this study, we estimated the therapeutic coverage of various antibiotics, focusing on cefiderocol and comparators, administered empirically against an infection of unknown origin in the ICU. METHODS: In the ARTEMIS surveillance study, susceptibilities of 624 Italian Gram-negative isolates to amikacin, aztreonam-avibactam, cefiderocol, ceftazidime-avibactam, ceftolozane-tazobactam, colistin, imipenem-relebactam, meropenem, and meropenem-vaborbactam were tested by broth microdilution, and results were interpreted by European Committee on Antimicrobial Susceptibility Testing breakpoints. The susceptibility rates from the ARTEMIS study were extrapolated to Gram-negative isolates obtained from 5,774 patients in Italian ICUs in 2021. The sum of the predicted susceptibilities of individual pathogens represented the overall likelihood of in vitro activity of each antibiotic as early targeted therapy for ICU patients. RESULTS: A total of 624 Italian Gram-negative isolates included 206 Pseudomonas aeruginosa, 138 Acinetobacter baumannii, 187 Klebsiella pneumoniae, and 93 Escherichia coli. Against A. baumannii, K. pneumoniae, P. aeruginosa, and E. coli, the overall susceptibility rates for cefiderocol were 87.7%, 96.8%, 99%, and 100%, respectively; and for comparator agents, 8.7-96.4%, 25.7-100%, 73.3-100%, and 89.2-100%, respectively. Among the subset of meropenem-resistant isolates, susceptibility rates of A. baumannii, K. pneumoniae, and P. aeruginosa to cefiderocol were 86.4%, 96.2% and 100%, respectively. Corresponding susceptibility rates to comparator agents were 0-96.8%, 0-100%, and 6.4-100%, respectively. There were no meropenem-resistant isolates of E. coli. The extrapolation of data to isolates from Italian ICUs showed that the highest likelihood of therapeutic coverage, both overall and among meropenem-resistant isolates, was reported for colistin (96.8% and 72.2%, respectively) and cefiderocol (95.7% and 71.4%, respectively). All other antibiotics were associated with a likelihood below 73% overall and between 0% and 41.4% for meropenem-resistant isolates. CONCLUSIONS: Based on confirmed susceptibility rates and reported ICU prevalence of multiple Gram-negative species, cefiderocol showed a higher predicted therapeutic coverage and utility in ICUs compared with comparator beta-lactam-beta-lactamase inhibitor antibiotics. Cefiderocol may be a promising early treatment option for patients at high risk of carbapenem-resistant Gram-negative bacterial infections in the ICU.

Third-generation cephalosporin resistant Escherichia coli in dogs and cats in Germany in 2019-2021.

OBJECTIVES: Antimicrobial resistance (AMR) poses a worldwide challenge, threatening global health. The objective of this research was to determine the 3rd generation cephalosporin resistance (3GCR) proportion in Escherichia (E.) coli isolated from clinical samples of dogs and cats in Germany. METHODS: The study utilized result data from antimicrobial susceptibility testing (AST) of isolates obtained from diagnostic samples collected from dogs and cats send in for bacterial examination. Data includes AST results from 3,491 veterinary practices in Germany spanning the years 2019 to 2021, representing 33.1% of practices and clinics nationwide. Out of 175,171 clinical samples, a total of 25,491 E. coli strains (14,6%) were evaluated for their susceptibility to antimicrobials, in particular the 3rd generation cephalosporin cefovecin, but also aminoglycosides (gentamicin, GEN), fluoroquinolones (enrofloxacin, ENR), tetracyclines (doxycycline), phenicols (chloramphenicol), folate pathway inhibitors (sulfamethoxazole + trimethoprim), and nitrofurans (nitrofurantoin). RESULTS: The cefovecin resistance proportion was 11.6% in the study period. Geographical analysis showed local variations in 3GCR in E. coli of ±3%. Regarding all E. coli isolates investigated, resistance proportions were observed as follows: 12% for sulfamethoxazole-trimethoprim, 7% for enrofloxacin, 8% for chloramphenicol and 4% for gentamicin. Notably, 3GCR E. coli showed significantly higher resistance proportions, specifically 30% for sulfamethoxazole-trimethoprim, 28% for chloramphenicol, 18% for enrofloxacin and 14% for gentamicin. CONCLUSIONS: This study represents the first of its kind to utilize an extensive dataset encompassing dogs and cats across Germany. Companion animals have close contact to their owners and transmission of 3GCR between them is likely as well as acquisition from other environmental sources. Resistance proportions (6.7%) against the antibiotic ceftazidime as reported by the German AMR surveillance for human medicine were lower than in our veterinary data. Our study provides an overview of the current 3GCR resistance proportion in Germany and demonstrates the importance of integrated AMR monitoring.

Synergistic Activity of Cefiderocol in Combination with Avibactam, Sulbactam or Tazobactam against Carbapenem-Resistant Gram-Negative Bacteria.

We investigated the activity of cefiderocol/ß-lactamase inhibitor combinations against clinical strains with different susceptibility profiles to cefiderocol to explore the potentiality of antibiotic combinations as a strategy to contain the major public health problem of multidrug-resistant (MDR) pathogens. Specifically, we evaluated the synergistic activity of cefiderocol with avibactam, sulbactam, or tazobactam on three of the most "Critical Priority" group of MDR bacteria (carbapenem-resistant Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii). Clinical isolates were genomically characterized by Illumina iSeq 100. The synergy test was conducted with time-kill curve assays. Specifically, cefiderocol/avibactam, /sulbactam, or /tazobactam combinations were analyzed. Synergism was assigned if bacterial grow reduction reached 2 log10 CFU/mL. We reported the high antimicrobial activity of the cefiderocol/sulbactam combination against carbapenem-resistant Enterobacterales, P. aeruginosa, and A. baumannii; of the cefiderocol/avibactam combination against carbapenem-resistant Enterobacterales; and of the cefiderocol/tazobactam combination against carbapenem-resistant Enterobacterales and P. aeruginosa. Our results demonstrate that all ß-lactamase inhibitors (BLIs) tested are able to enhance cefiderocol antimicrobial activity, also against cefiderocol-resistant isolates. The cefiderocol/sulbactam combination emerges as the most promising combination, proving to highly enhance cefiderocol activity in all the analyzed carbapenem-resistant Gram-negative isolates, whereas the Cefiderocol/tazobactam combination resulted in being active only against carbapenem-resistant Enterobacterales and P. aeruginosa, and cefiderocol/avibactam was only active against carbapenem-resistant Enterobacterales.