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The Journal of Antimicrobial... Jun 2024Riemerella anatipestifer encodes an iron acquisition system, but whether it encodes the iron efflux pump and its role in antibiotic resistance are largely unknown.
BACKGROUND
Riemerella anatipestifer encodes an iron acquisition system, but whether it encodes the iron efflux pump and its role in antibiotic resistance are largely unknown.
OBJECTIVES
To screen and identify an iron efflux gene in R. anatipestifer and determine whether and how the iron efflux gene is involved in antibiotic resistance.
METHODS
In this study, gene knockout, streptonigrin susceptibility assay and inductively coupled plasma mass spectrometry were used to screen for the iron efflux gene ietA. The MIC measurements, scanning electron microscopy and reactive oxygen species (ROS) detection were used to verify the role of IetA in aztreonam resistance and its mechanism. Mortality and colonization assay were used to investigate the role of IetA in virulence.
RESULTS
The deletion mutant ΔietA showed heightened susceptibility to streptonigrin, and prominent intracellular iron accumulation was observed in ΔfurΔietA under excess iron conditions. Additionally, ΔietA exhibited increased sensitivity to H2O2-produced oxidative stress. Under aerobic conditions with abundant iron, ΔietA displayed increased susceptibility to the β-lactam antibiotic aztreonam due to heightened ROS production. However, the killing efficacy of aztreonam was diminished in both WT and ΔietA under anaerobic or iron restriction conditions. Further experiments demonstrated that the efficiency of aztreonam against ΔietA was dependent on respiratory complexes Ⅰ and Ⅱ. Finally, in a duckling model, ΔietA had reduced virulence compared with the WT.
CONCLUSION
Iron efflux is critical to alleviate oxidative stress damage and β-lactam aztreonam killing in R. anatipestifer, which is linked by cellular respiration.
Topics: Oxidative Stress; Iron; Animals; Microbial Sensitivity Tests; Anti-Bacterial Agents; Riemerella; Aztreonam; Flavobacteriaceae Infections; Virulence; beta-Lactam Resistance; Ducks; Reactive Oxygen Species; Membrane Transport Proteins; Streptonigrin; Gene Knockout Techniques; Poultry Diseases; Bacterial Proteins
PubMed: 38629469
DOI: 10.1093/jac/dkae114 -
BioRxiv : the Preprint Server For... Apr 2024Nonribosomal peptide synthetases (NRPSs) are responsible for the production of important biologically active peptides. The large, multidomain NRPSs operate through an...
Nonribosomal peptide synthetases (NRPSs) are responsible for the production of important biologically active peptides. The large, multidomain NRPSs operate through an assembly line strategy in which the growing peptide is tethered to carrier domains that deliver the intermediates to neighboring catalytic domains. While most NRPS domains catalyze standard chemistry of amino acid activation, peptide bond formation and product release, some canonical NRPS catalytic domains promote unexpected chemistry. The paradigm monobactam antibiotic sulfazecin is produced through the activity of a terminal thioesterase domain that catalyzes an unusual β-lactam forming reaction in which the nitrogen of the C-terminal -sulfo-2,3-diaminopropionate residue attacks its thioester tether to release the β-lactam product. We have determined the structure of the thioesterase domain as both a free-standing domain and a didomain complex with the upstream peptidyl-carrier domain. The structure illustrates a constrained active site that orients the substrate properly for β-lactam formation. In this regard, the structure is similar to the β-lactone forming thioesterase domain responsible for the production of obafluorin. Analysis of the structure identifies features that are responsible for this four-membered ring closure and enable bioinformatic analysis to identify additional, uncharacterized β-lactam-forming biosynthetic gene clusters by genome mining.
PubMed: 38617275
DOI: 10.1101/2024.04.06.588331 -
Molecules (Basel, Switzerland) Mar 2024Methicillin-resistant (MRSA) has evolved into a dangerous pathogen resistant to beta-lactam antibiotics (BLAs) and has become a worrisome superbug. In this study, a...
Methicillin-resistant (MRSA) has evolved into a dangerous pathogen resistant to beta-lactam antibiotics (BLAs) and has become a worrisome superbug. In this study, a strategy in which shikimic acid (SA), which has anti-inflammatory and antibacterial activity, is combined with BLAs to restart BLA activity was proposed for MRSA treatment. The synergistic effects of oxacillin combined with SA against oxacillin resistance in vitro and in vivo were investigated. The excellent synergistic effect of the oxacillin and SA combination was confirmed by performing the checkerboard assay, time-killing assay, live/dead bacterial cell viability assay, and assessing protein leakage. SEM showed that the cells in the control group had a regular, smooth, and intact surface. In contrast, oxacillin and SA or the combination treatment group exhibited different degrees of surface collapse. q-PCR indicated that the combination treatment group significantly inhibited the expression of the A gene. In vivo, we showed that the combination treatment increased the survival rate and decreased the bacterial load in mice. These results suggest that the combination of oxacillin with SA is considered an effective treatment option for MRSA, and the combination of SA with oxacillin in the treatment of MRSA is a novel strategy.
Topics: Animals; Mice; Methicillin-Resistant Staphylococcus aureus; Shikimic Acid; Monobactams; beta Lactam Antibiotics; Oxacillin
PubMed: 38611807
DOI: 10.3390/molecules29071528 -
Antimicrobial Agents and Chemotherapy May 2024harboring Verona Integron-encoded metallo-β-lactamase enzymes (VIM-CRPA) have been associated with infection outbreaks in several parts of the world. In the US,...
harboring Verona Integron-encoded metallo-β-lactamase enzymes (VIM-CRPA) have been associated with infection outbreaks in several parts of the world. In the US, however, VIM-CRPA remain rare. Starting in December 2018, we identified a cluster of cases in our institution. Herein, we present our epidemiological investigation and strategies to control/manage these challenging infections. This study was conducted in a large academic healthcare system in Miami, FL, between December 2018 and January 2022. Patients were prospectively identified via rapid molecular diagnostics when cultures revealed carbapenem-resistant . Alerts were received in real time by the antimicrobial stewardship program and infection prevention teams. Upon alert recognition, a series of interventions were performed as a coordinated effort. A retrospective chart review was conducted to collect patient demographics, antimicrobial therapy, and clinical outcomes. Thirty-nine VIM-CRPA isolates led to infection in 21 patients. The majority were male (76.2%); the median age was 52 years. The majority were mechanically ventilated ( = 15/21; 71.4%); 47.6% ( = 10/21) received renal replacement therapy at the time of index culture. Respiratory ( = 20/39; 51.3%) or bloodstream ( = 13/39; 33.3%) were the most common sources. Most infections ( = 23/37; 62.2%) were treated with an aztreonam-avibactam regimen. Six patients (28.6%) expired within 30 days of index VIM-CRPA infection. Fourteen isolates were selected for whole genome sequencing. Most of them belonged to ST111 (12/14), and they all carried bla chromosomally. This report describes the clinical experience treating serious VIM-CRPA infections with either aztreonam-ceftazidime/avibactam or cefiderocol in combination with other agents. The importance of implementing infection prevention strategies to curb VIM-CRPA outbreaks is also demonstrated.
Topics: Adult; Female; Humans; Male; Middle Aged; Anti-Bacterial Agents; Antimicrobial Stewardship; Azabicyclo Compounds; Aztreonam; beta-Lactamases; Carbapenems; Ceftazidime; Drug Combinations; Drug Resistance, Multiple, Bacterial; Integrons; Microbial Sensitivity Tests; Pseudomonas aeruginosa; Pseudomonas Infections; Retrospective Studies
PubMed: 38602418
DOI: 10.1128/aac.01474-23 -
IScience Apr 2024[This corrects the article DOI: 10.1016/j.isci.2024.109202.].
[This corrects the article DOI: 10.1016/j.isci.2024.109202.].
PubMed: 38600972
DOI: 10.1016/j.isci.2024.109572 -
Scientific Reports Apr 2024Bacterial resistance surveillance is one of the main outputs of microbiological laboratories and its results are important part of antimicrobial stewardship (AMS). In...
Bacterial resistance surveillance is one of the main outputs of microbiological laboratories and its results are important part of antimicrobial stewardship (AMS). In this study, the susceptibility of specific bacteria to selected antimicrobial agents was tested. The susceptibility of 90 unique isolates of pathogens of critical priority obtained from clinically valid samples of ICU patients in 2017-2021 was tested. 50% of these fulfilled difficult-to-treat resistance (DTR) criteria and 50% were susceptible to all antibiotics included in the definition. 10 Enterobacterales strains met DTR criteria, and 2 (20%) were resistant to colistin (COL), 2 (20%) to cefiderocol (FCR), 7 (70%) to imipenem/cilastatin/relebactam (I/R), 3 (30%) to ceftazidime/avibactam (CAT) and 5 (50%) to fosfomycin (FOS). For Enterobacterales we also tested aztreonam/avibactam (AZA) for which there are no breakpoints yet. The highest MIC of AZA observed was 1 mg/l, MIC range in the susceptible cohort was 0.032-0.064 mg/l and in the DTR cohort (incl. class B beta-lactamase producers) it was 0.064-1 mg/l. Two (13.3%) isolates of Pseudomonas aeruginosa (15 DTR strains) were resistant to COL, 1 (6.7%) to FCR, 13 (86.7%) to I/R, 5 (33.3%) to CAT, and 5 (33.3%) to ceftolozane/tazobactam. All isolates of Acinetobacter baumannii with DTR were susceptible to COL and FCR, and at the same time resistant to I/R and ampicillin/sulbactam. New antimicrobial agents are not 100% effective against DTR. Therefore, it is necessary to perform susceptibility testing of these antibiotics, use the data for surveillance (including local surveillance) and conform to AMS standards.
Topics: Humans; Anti-Bacterial Agents; Retrospective Studies; Cephalosporins; Aztreonam; Cefiderocol; Gram-Negative Bacteria; Colistin; Microbial Sensitivity Tests; Pseudomonas aeruginosa; Azabicyclo Compounds
PubMed: 38594467
DOI: 10.1038/s41598-024-59036-0 -
BMC Infectious Diseases Apr 2024A major worldwide health issue is the rising frequency of resistance of bacteria.Drug combinations are a winning strategy in fighting resistant bacteria and might help...
BACKGROUND
A major worldwide health issue is the rising frequency of resistance of bacteria.Drug combinations are a winning strategy in fighting resistant bacteria and might help in protecting the existing drugs.Monolaurin is natural compound extracted from coconut oil and has a promising antimicrobial activity against Staphylococcus.aureus. This study aims to examine the efficacy of monolaurin both individually and in combination with β-lactam antibiotics against Staphylococcus aureus isolates.
METHODS
Agar dilution method was used for determination of minimum inhibitory concentration (MIC) of monolaurin against S.aureus isolates. Scanning electron microscope (SEM) was used to detect morphological changes in S.aureus after treatment with monolaurin. Conventional and Real-time Polymerase chain reaction (RT-PCR) were performed to detect of beta-lactamase (blaZ) gene and its expressional levels after monolaurin treatment. Combination therapy of monolaurin and antibiotics was assessed through fractional inhibitory concentration and time-kill method.
RESULTS
The antibacterial activity of monolaurin was assessed on 115 S.aureus isolates, the MIC of monolaurin were 250 to 2000 µg/ml. SEM showed cell elongation and swelling in the outer membrane of S.aureus in the prescence of 1xMIC of monolaurin. blaZ gene was found in 73.9% of S.aureus isolates. RT-PCR shows a significant decrease in of blaZ gene expression at 250 and 500 µg/ml of monolaurin. Synergistic effects were detected through FIC method and time killing curve. Combination therapy established a significant reduction on the MIC value. The collective findings from the antibiotic combinations with monolaurin indicated synergism rates ranging from 83.3% to 100%.In time-kill studies, combination of monolaurin and β-lactam antibiotics produced a synergistic effect.
CONCLUSION
This study showed that monolaurin may be a natural antibacterial agent against S. aureus, and may be an outstanding modulator of β-lactam drugs. The concurrent application of monolaurin and β-lactam antibiotics, exhibiting synergistic effects against S. aureus in vitro, holds promise as potential candidates for the development of combination therapies that target particularly, patients with bacterial infections that are nearly incurable.
Topics: Humans; Staphylococcus aureus; beta Lactam Antibiotics; Glycerol; Drug Synergism; Anti-Bacterial Agents; Monobactams; Staphylococcal Infections; Microbial Sensitivity Tests; Methicillin-Resistant Staphylococcus aureus; Laurates; Monoglycerides
PubMed: 38584271
DOI: 10.1186/s12879-024-09261-9 -
International Journal of Antimicrobial... Jun 2024Carbapenem-resistant Klebsiella pneumoniae (CRKP) poses immense threats to the health of infected patients worldwide, especially children. This study reports the...
Carbapenem-resistant Klebsiella pneumoniae (CRKP) poses immense threats to the health of infected patients worldwide, especially children. This study reports the infection caused by CRKP in a paediatric intensive care unit (PICU) child and its drug-resistant mutation during the treatment. Twelve Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae strains were isolated from the child. Broth microdilution method, plasmid transformation assay, and whole genome sequencing (WGS) were performed to investigate the antimicrobial susceptibility, resistance mechanisms, and genetic structural features of CRKPs. The results showed that 12 strains were highly resistant to most available antimicrobial agents. Among them, K. pneumoniae FD11 and K. pneumoniae FD12 were resistant to ceftazidime-avibactam (CZA, MIC >64 mg/L) and restored the carbapenem susceptibility (Imipenem, MIC =0.25 mg/L; Meropenem, MIC =2 mg/L). The patient improved after treatment with CZA in combination with aztreonam. Plasmid transformation assay demonstrated that the bla-positive transformant increased MICs of CZA by at least 33-fold and 8-fold compared with the recipient Escherichia coli DH5α and bla-positive transformants. WGS analysis revealed that all strains belonged to the ST11-KL64 type and showed highly homologous (3-26 single nucleotide polymorphisms [SNPs]). A single base mutation (G532T) of bla resulted in a tyrosine to aspartic acid substitution at Ambler amino acid position 179 (D179Y), which conferred CZA resistance in K. pneumoniae. This is the first report of a drug-resistant mutation evolving into bla during the treatment of bla-positive CRKP in paediatric-infected patients. It advises clinicians that routine sequential antimicrobial susceptibility testing and KPC genotyping are critical during CZA therapy in children infected with CRKP.
Topics: Humans; Klebsiella pneumoniae; Azabicyclo Compounds; Drug Combinations; Ceftazidime; Klebsiella Infections; Microbial Sensitivity Tests; beta-Lactamases; Anti-Bacterial Agents; Bacterial Proteins; Whole Genome Sequencing; Drug Resistance, Multiple, Bacterial; Child; Plasmids; Carbapenem-Resistant Enterobacteriaceae; Male; Aztreonam
PubMed: 38570018
DOI: 10.1016/j.ijantimicag.2024.107163 -
The Journal of Antimicrobial... Jun 2024To evaluate the performance of an in-house developed disk diffusion method for aztreonam in combination with avibactam against Enterobacteriales.
OBJECTIVES
To evaluate the performance of an in-house developed disk diffusion method for aztreonam in combination with avibactam against Enterobacteriales.
METHODS
The in vitro antibacterial activity of aztreonam with avibactam against 204 carbapenemase-producing Enterobacteriales was determined by a disk diffusion method, with a broth microdilution method as a reference.
RESULTS
The optimal S/R breakpoints for disk diffusion tests of 30/20 and 10/4 µg disks, calculated by the dBETs software using the model-based approaches, were ≥22/≤21 and ≥12/≤11 mm, respectively. On the basis of the estimated breakpoints, the CAs for disk diffusion tests of 30/20 and 10/4 µg aztreonam/avibactam disks were both 98.0%, with 0.5% major error and 37.5% very major error.
CONCLUSIONS
The home-made disk diffusion method is an economical and practical method for clinical microbiology laboratories to determine the antibacterial susceptibility of aztreonam with avibactam against Enterobacteriales.
Topics: Aztreonam; Azabicyclo Compounds; Anti-Bacterial Agents; Enterobacteriaceae; Disk Diffusion Antimicrobial Tests; Microbial Sensitivity Tests; Humans
PubMed: 38564262
DOI: 10.1093/jac/dkae097 -
International Journal of Antimicrobial... Jun 2024Hypermutable Pseudomonas aeruginosa strains are highly prevalent in chronic lung infections of patients with cystic fibrosis (CF). Acute exacerbations of these...
Synergistic effects of inhaled aztreonam plus tobramycin on hypermutable cystic fibrosis Pseudomonas aeruginosa isolates in a dynamic biofilm model evaluated by mechanism-based modelling and whole genome sequencing.
OBJECTIVE
Hypermutable Pseudomonas aeruginosa strains are highly prevalent in chronic lung infections of patients with cystic fibrosis (CF). Acute exacerbations of these infections have limited treatment options. This study aimed to investigate inhaled aztreonam and tobramycin against clinical hypermutable P. aeruginosa strains using the CDC dynamic in vitro biofilm reactor (CBR), mechanism-based mathematical modelling (MBM) and genomic studies.
METHODS
Two CF multidrug-resistant strains were investigated in a 168 h CBR (n = 2 biological replicates). Regimens were inhaled aztreonam (75 mg 8-hourly) and tobramycin (300 mg 12-hourly) in monotherapies and combination. The simulated pharmacokinetic profiles of aztreonam and tobramycin (t = 3 h) were based on published lung fluid concentrations in patients with CF. Total viable and resistant counts were determined for planktonic and biofilm bacteria. MBM of total and resistant bacterial counts and whole genome sequencing were completed.
RESULTS
Both isolates showed reproducible bacterial regrowth and resistance amplification for the monotherapies by 168 h. The combination performed synergistically, with minimal resistant subpopulations compared to the respective monotherapies at 168 h. Mechanistic synergy appropriately described the antibacterial effects of the combination regimen in the MBM. Genomic analysis of colonies recovered from monotherapy regimens indicated noncanonical resistance mechanisms were likely responsible for treatment failure.
CONCLUSION
The combination of aztreonam and tobramycin was required to suppress the regrowth and resistance of planktonic and biofilm bacteria in all biological replicates of both hypermutable multidrug-resistant P. aeruginosa CF isolates. The developed MBM could be utilised for future investigations of this promising inhaled combination.
Topics: Tobramycin; Aztreonam; Pseudomonas aeruginosa; Biofilms; Cystic Fibrosis; Humans; Anti-Bacterial Agents; Administration, Inhalation; Pseudomonas Infections; Whole Genome Sequencing; Drug Synergism; Microbial Sensitivity Tests; Drug Resistance, Multiple, Bacterial; Models, Theoretical; Drug Therapy, Combination
PubMed: 38561094
DOI: 10.1016/j.ijantimicag.2024.107161