Resistant Bacteria Research Articles

Treated and untreated cows housed side by side in tie-stalls and their respective risk of harboring E. coli resistant to antimicrobials

Parenteral antimicrobial treatment results in the excretion of antimicrobial-resistant bacteria. Dairy cows are commonly housed side by side in tie-stalls and often receive antimicrobial treatment. However, studies investigating treated cows as source of colonization of neighboring cows with resistant bacteria are scarce. Antimicrobial resistance (AMR) in cows (treated and untreated) in tie-stalls was investigated to assess their respective risks of carrying resistant bacteria. Furthermore, we analyzed associations of farm management with AMR. Case-control study: For isolation of indicator Escherichia (E.) coli, rectal swab samples were taken. Cows were sampled depending on treatment history and proximity to one another (cow A: recently treated parenterally; cow B: untreated, next to cow A; cow C: untreated, at considerable distance from all treated cows). Antimicrobial susceptibility was tested by microdilution. Associations of AMR with exposure to cow A, treatments, and management were analyzed using generalized mixed-effects logistic models. Susceptibility data on 571 isolates from 131 dairy farms were obtained. Almost no difference in proportions of resistant E. coli was observed between cows B and C (B: 53.4%; C: 57.2%; P = 0.52). Untreated cows had lower odds of carrying resistant E. coli than treated cows (B: OR 0.44, P<0.001; C: OR 0.54, P = 0.007). Non-pansusceptibility of isolates was associated with antimicrobial treatment (1 treatment: OR 2.11, P = 0.001; ≥2: OR 1.76, P = 0.043). Using manure on forage crops was associated with higher odds of pansusceptibility (OR 2.01, P = 0.004). For daily practice, with regard to the risk of AMR transmission, results of this study do not provide evidence for the need to separate treated cows from others during treatment in tie-stalls.

Characterizing Escherichia coli carrying plasmid-mediated AmpC β-lactamases to optimize detection in a diagnostic laboratory setting

ABSTRACT Plasmid-mediated AmpC β-lactamases are a cause of acquired cephalosporin resistance in Gram-negative bacteria. However, consensus regarding the optimal detection method is yet to be achieved and varies depending on local epidemiology and laboratory capacity. We determined the acquired genotypic resistance mechanisms of 250 Escherichia coli isolates with a positive AmpC screen, defined as cefoxitin MIC ≥ 8 mg/L and a positive AmpC double- disc diffusion test, using in-house designed high-resolution melt PCR, detecting plasmid-acquired genes from the CIT and DHA families. A proportion of these isolates ( n = 170, 68%) underwent further genotypic characterization using whole- genome sequencing (WGS). Of 250 isolates with a positive screening test, 72 (28.8%) were determined to carry an acquired AmpC gene. There was 100% concordance between PCR and WGS in the identification of acquired AmpC genes. The phenotypic criteria were then assessed to determine their utility in predicting acquired AmpC gene carriage. Criteria 1 (cefoxitin MIC > 8 mg/L plus ceftriaxone MIC > 1 mg/L and/or ceftazidime MIC > 1 mg/L) yielded a sensitivity of 93.1% and a specificity of 47.8%. Criteria 2 (cefoxitin MIC > 16 mg/L plus ceftriaxone MIC > 4 mg/L) had a sensitivity of 33.3% and a specificity of 98.9%. DHA genes, whose expression may be induced following antibiotic exposure, were present in 19% of isolates testing susceptible to ceftriaxone (MIC ≤ 1 mg/L) and were significantly more likely than CIT genes to be detected in susceptible isolates ( P < 0.0001). These findings highlight the importance of using genotypic methods to detect acquired AmpC resistance in E. coli isolates that meet phenotypic screening criteria. IMPORTANCE Detection of transmissible AmpC resistance remains a challenging problem for diagnostic laboratories, especially in Escherichia coli where the expression of its intrinsic AmpC gene can result in phenotypic resistance patterns indistinguishable from plasmid-mediated resistance. In conjunction with whole- genome sequencing (WGS), we describe the development and performance of a novel melt-curve PCR to identify the two most prevalent plasmid-mediated AmpC gene families: CIT and DHA. We then describe phenotypic testing algorithms that incorporate this PCR and can differentiate these from non-acquired resistance in E. coli . It is important to distinguish these, not only to spare patients from unnecessarily being treated with infection control precautions, but also to identify plasmid-mediated genes, especially of the DHA family, that have been associated with inducible drug resistance to third- generation cephalosporins.

Structure-guided drug repurposing identifies aristospan as a potential inhibitor of β-lactamase: insights from virtual screening and molecular dynamics simulations

The rise of β-Lactamase mediated antibiotic resistance is a major concern for public health; hence, there is an urgent need to find new treatment approaches. Structure-guided drug repurposing offers a promising approach to swiftly deliver essential therapeutics in the fight against escalating antibiotic resistance. Here, a structure-guided virtual screening approach was used involving drug profiling, molecular docking, and molecular dynamics (MD) simulation to identify existing drugs against β-Lactamase-associated drug resistance. We exploited a large panel of FDA-approved drugs to an extensive in silico analysis to ascertain their ability to inhibit β-Lactamase. First, molecular docking investigations were performed to assess the binding affinities and interactions of screened molecules with the active site of β-Lactamase enzymes. Out of all the screened candidates, Aristospan was identified to possess promising characteristics, which include appropriate drug profiles, high binding specificity, and efficiency towards the binding pocket of β-Lactamase. Further analysis showed that Aristospan possesses several desirable biological characteristics and tends to bind to the β-Lactamase binding site. To explore the interactions further, the best docking pose of Aristospan was selected for MD simulations to assess the thermodynamic stability of the drug-enzyme complex and its conformational changes over 500 ns. The MD simulations in independent replica runs demonstrated that the β-Lactamase-Aristospan complex was stable in the 500 ns trajectory. These enlightening results suggest that Aristospan may harbor the potential for further evolution into a possible β-Lactamase inhibitor, with potential applications in overcoming antibiotic resistance in both Gram-positive and Gram-negative bacteria.

Profiling the bacterial microbiome diversity and assessing the potential to detect antimicrobial resistance bacteria in wastewater in Kimberley, South Africa

Wastewater treatment plants (WWTPs) are hotspots for pathogens, and can facilitate horizontal gene transfer, potentially releasing harmful genetic material and antimicrobial resistance genes into the environment. Little information exists on the composition and behavior of microbes in WWTPs, especially in developing countries. This study used environmental DNA (eDNA) techniques to examine the microbiome load of wastewater from WWTPs. The DNA was isolated from wastewater samples collected from the treatment trains of three WWTPs in Kimberley, South Africa, and the microbial diversity and composition was compared through 16 S rRNA gene sequencing. The microbes detected were of the Kingdom Bacteria, and of these, 48.27% were successfully identified to genus level. The majority of reads from the combined bacterial data fall within the class Gammaproteobacteria, which is known to adversely impact ecological and human health. Arcobacteraceae constituted 19% of the bacterial reads, which is expected as this family is widespread in aquatic environments. Interestingly, the most abundant bacterial group was Bacteroides, which contain a variety of antibiotic-resistant members. Overall, various antibiotic-resistant taxa were detected in the wastewater, indicating a concerning level of antibiotic resistance within the bacterial community. Therefore, eDNA analysis can be a valuable tool in monitoring and assessing the bacterial microbiome in wastewater, thus providing important information for the optimization and improvement of wastewater treatment systems and mitigate public health risks.

Faecal carriage of extended-spectrum beta-lactamase and carbapenemase-producing enterobacterales among HIV patients at Jimma Medical Center, Southwest Ethiopia.

Enterobacterales infections in immunocompromised individuals are associated with considerable morbidity, mortality, and health care costs. This study aimed to assess the faecal carriage of extended-spectrum β-lactamase (ESBL) and carbapenemase-producing Enterobacterales (CPE) among HIV-infected patients at Jimma Medical Center. A total of 344 stool samples were collected and inoculated on Mac-Conkey and Eosin-Methylene Blue agar and incubated at 35-37°C aerobically. ESBL and carbapenemase production were detected using D68C ESBL/AmpC and D73C CARBA plus (Mast Group, UK). A total of 376 Enterobacterales were isolated. The prevalence of ESBL-PE and CPE carriage rate was 13.3% (50/376) and 4.3% (16/376) respectively. The highest proportion of ESBL producing isolates were found in K. pneumoniae 29.0% (9/31) followed by E. coli 13.4% (39/292). Similarly, K. pneumoniae 12.9% (4/31) was the most common carbapenem-resistant isolate followed by E. coli 3.8% (11/292). Multi-drug resistance was observed in 66.5% (250/376) of the isolates. Prior cephalosporin use (AOR = 7.9; 2.31-27.29), CD4 count (≤ 350 cells/µL) (AOR = 3.8; 1.12-12.9), and comorbidities (AOR = 2.3; 1.24-4.32) were significantly associated with ESBL production. Additionally, cephalosporin use (AOR = 6.34; 1.27-31.66) was significantly associated with the presence of CRE. This study revealed a high prevalence of ESBL-PE and CPE among HIV patients, with K. pneumoniae and E. coli being the dominant isolates. MDR was common, with key risk factors being prior cephalosporin use, low CD4 counts, and comorbidities. These findings emphasize the need for enhanced infection prevention and control, regular screening, and improved antibiotic stewardship to curb the spread of resistant bacteria in immunocompromised individuals.

Cefiderocol in Combating Carbapenem-Resistant Acinetobacter baumannii: Action and Resistance

Acinetobacter baumannii (A. baumannii) has emerged as a prominent multidrug-resistant (MDR) pathogen, significantly complicating treatment strategies due to its formidable resistance mechanisms, particularly against carbapenems. Reduced membrane permeability, active antibiotic efflux, and enzymatic hydrolysis via different β-lactamases are the main resistance mechanisms displayed by A. baumannii, and they are all effective against successful treatment approaches. This means that alternate treatment approaches, such as combination therapy that incorporates beta-lactams, β-lactamase inhibitors, and novel antibiotics like cefiderocol, must be investigated immediately. Cefiderocol, a new catechol-substituted siderophore cephalosporin, improves antibacterial activity by allowing for better bacterial membrane penetration. Due to its unique structure, cefiderocol can more efficiently target and destroy resistant bacteria by using iron transport systems. Through its inhibition of peptidoglycan formation through binding to penicillin-binding proteins (PBPs), cefiderocol avoids conventional resistance pathways and induces bacterial cell lysis. The possibility of resistance development due to β-lactamase synthesis and mutations in PBPs, however, emphasizes the need for continued investigation into cefiderocol’s efficacy in combination treatment regimes. Cefiderocol’s siderophore mimic mechanism is especially important in iron-limited conditions because it can use ferric-siderophore transporters to enter cells. Additionally, its passive diffusion through bacterial porins increases its intracellular concentrations, making it a good option for treating carbapenem-resistant A. baumannii, especially in cases of severe infections and ventilator-associated diseases (IVACs). Cefiderocol may reduce MDR infection morbidity and mortality when combined with customized antimicrobial treatments, but further investigation is needed to improve patient outcomes and address A. baumannii resistance issues.

Cefiderocol Versus Best Available Therapy in the Treatment of Critically Ill Patients with Severe Infections Due to Resistant Gram-Negative Bacteria: A Systematic Review and Meta-Analysis

Background: This study aims to assess the effectiveness and safety of cefiderocol in treating severe infections caused by multidrug-resistant Gram-negative bacteria (MDR-GNB) in critically ill patients, particularly those in intensive care units (ICUs). Methods: A meta-analysis of studies, including randomized clinical trials and observational studies in adult patients, was performed. Studies with at least 50% of critically ill patients were included. Studies with small sample size or without comparison groups were excluded. Sources included PubMed, Scopus, or Google Scholar, up to 14 August 2024. Risk of bias was assessed according to the Cochrane tool. The main outcome examined was 30-day mortality, while secondary outcomes assessed included clinical cure rates and adverse effects. Results were expressed with odds ratios. No funding was received for this study. It was registered in the International Prospective Register of Systematic Reviews (PROSPERO) with reference CRD42024563041. Results: eight studies, with 1339 patients were included in the meta-analysis. Cefiderocol treatment was associated with a lower 30-day mortality rate than other available therapies (pooled OR 0.47; 95% CI: 0.23–0.97, p = 0.04), particularly in cases of carbapenem-resistant A. baumannii infections (pooled OR 0.29; 95% CI: 0.14–0.60, p < 0.001). Although there was a non-significant trend toward higher clinical cure rates in the cefiderocol group (OR 1.59; 95% CI: 0.96–2.62, p = 0.07), the drug demonstrated at least non-inferiority when compared to other treatment options. Study limitations included moderate heterogeneity between studies, and a high risk of bias in non-RCT studies. (Five cohort studies were included). Another limitation is that five of the eight studies compared cefiderocol versus colistine, an antibiotic with known toxicity. Conclusions: The findings suggest that cefiderocol is a promising therapeutic option for managing severe MDR-GNB infections in critically ill patients, offering a potential global benefit on mortality and at least non-inferiority in the cure rate when compared with other therapies.

Addition to “Removal of Antibiotic Resistant Bacteria and Genes by UV-Assisted Electrochemical Oxidation on Degenerative TiO2 Nanotube Arrays”

Addition to “Removal of Antibiotic Resistant Bacteria and Genes by UV-Assisted Electrochemical Oxidation on Degenerative TiO₂ Nanotube Arrays”

A scientific research training programme for teaching biomedical students to identify the horizontal transfer of antibiotic resistance genes.

Worldwide prevalence of multi-antibiotic resistant bacteria is rapidly increasing, and the education of undergraduates and graduates about antibiotic resistance and its associated horizontal gene transfer is critical in the general effort to confront the spread of antibiotic resistance. In this study, a deeper understanding of antibiotic resistance and horizontal gene transfer was achieved by biomedical undergraduate students through a scientific research programme. The enthusiasm of students to participate in the training programme was very high, and results revealed that each student could identify the antibiotic resistance integrative and conjugative element from the Stenotrophomonas maltophilia MER1 genome. Each student could also draw the phylogenetic relationship of the antibiotic resistance integrative and conjugative element. In addition, students proved the horizontal transfer of antibiotic resistance genes from S. maltophilia MER1 to Escherichia coli strain 25DN through conjugation and PCR assays. Each group of students was able to obtain the expected results, indicating that the outcome of the scientific research programme was highly reproducible. This programme improved the theoretical knowledge about antibiotic resistance and horizontal gene transfer and the research skills of biomedical sciences students. Through this programme, students learned that antibiotic resistance genes can be horizontally transferred among different bacteria, laying a solid foundation for students to value the importance of the appropriate use of antibiotics in their future work and life.

Versatile silicate-modified hydrochar based on Scutellaria baicalensis-residue for efficiently removing heavy metal-antibiotic co-contamination and relevant bio-contaminants from wastewater

In this study, we utilized typical Chinese medicine herbal residues (CMHRs)－Scutellaria baicalensis (Scutellaria baicalensis Georgi) residue (SR), as the raw material and employed Na2SiO3 and Fe2(SO4)3 as modifying agents to fabricate a novel and multifunctional hydrochar (FeSi-SRHC), which was designed for comprehensive removal of typical contaminants such as Cu2+, Zn2+, tetracycline (TC), and ciprofloxacin (CIP), along with relevant bio-contaminants (resistant bacteria (RBs) and resistance genes (RGs)) present in wastewater. Based on the analysis of adsorption kinetics and Freundlich isotherm, it was found that FeSi-SRHC exhibited physical monolayer adsorption for Cu2+/Zn2+ while mainly chemical multilayer adsorption for TC/CIP in single-contamination system. Furthermore, Langmuir isotherm demonstrated excellent adsorption capacity of FeSi-SRHC towards Cu2+/Zn2+/TC/CIP with maximum capacities of 255.75, 265.26, 425.53, and 404.86 mg/g, respectively. In the co-contamination system, the presence of Cu2+, Zn2+, TC, and CIP exhibited varying degrees of inhibitory or promotive effects on the mutual adsorption by FeSi-SRHC. This divergence stemmed from differences in complexation intensities and concentration ratios among diverse co-existing contaminants. Based on XPS and Density Functional Theory (DFT) analyses, the adsorption process for Cu2+, Zn2+, TC, and CIP by FeSi-SRHC primarily involves pore fill, complexation reactions, ion exchange, hydrogen bonding, π-π stacking interactions, and electrostatic interactions. Bio-contaminant removal experiments revealed that the release of baicalin and wogonoside from FeSi-SRHC disrupts the structure of RBs cells and compromises the integrity of resistance plasmids. The practical application experiment showed that FeSi-SRHC displayed favorable performance for removing heavy metals, antibiotics, and bio-contaminants in actual wastewater. This study presented a “Treating waste with waste” strategy, which provided a method with low carbon, eco-friendly, and inexpensive for CMHRs resources and turning waste into treasure while proposing a idea to address the challenges associated with treating heavy metal, antibiotic, and bio-contaminant contamination in wastewater.

Antimicrobial Peptide Delivery Systems as Promising Tools Against Resistant Bacterial Infections

The extensive use of antibiotics during recent years has led to antimicrobial resistance development, a significant threat to global public health. It is estimated that around 1.27 million people died worldwide in 2019 due to infectious diseases caused by antibiotic-resistant microorganisms, according to the WHO. It is estimated that 700,000 people die each year worldwide, which is expected to rise to 10 million by 2050. Therefore, new and efficient antimicrobials against resistant pathogenic bacteria are urgently needed. Antimicrobial peptides (AMPs) present a broad spectrum of antibacterial effects and are considered potential tools for developing novel therapies to combat resistant infections. However, their clinical application is currently limited due to instability, low selectivity, toxicity, and limited bioavailability, resulting in a narrow therapeutic window. Here we describe an overview of the clinical application of AMPs against resistant bacterial infections through nanoformulation. It evaluates metal, polymeric, and lipid AMP delivery systems as promising for the treatment of resistant bacterial infections, offering a potential solution to the aforementioned limitations.

Efflux-mediated Multidrug Resistance in Critical Gram-negative Bacteria and Natural Efflux Pump Inhibitors.

Multidrug Resistance mechanisms in microorganisms confer the slackness of the existing drugs, leading to added difficulty in treating infections. As a consequence, efficient novel drugs and innovative therapies to treat MDR infections are necessarily required. One of the primary contributors to the emergence of multidrug resistance in gram-negative bacteria has been identified as the efflux pumps. These transporter efflux pumps reduce the intracellular concentration of antibiotics and aid bacterial survival in suboptimal low antibiotic concentration environments that may cause treatment failure. The reversal of this resistance via inhibition of the efflux mechanism is a promising method for increasing the effectiveness of antibiotics against multidrug-resistant pathogens. Such EPI, in combination with antibiotics, can make it easier to reintroduce traditional antibiotics into clinical practice. This review mostly examines efflux-mediated multidrug resistance in critical gram-negative bacterial pathogens and EPI of plant origin that have been reported over previous decades.

Effect of novel phage cocktail on Salmonella recovered from broiler sources and its anti-biofilm effect on food contact surface model

The contamination of Salmonella in poultry products remains an important food safety and economic issue as the products have been recalled or rejected. Traditional antibiotic-based therapy in the animal production chain can cause antibiotic resistance (ABR) in bacteria, leading to severe illness and failure to treat diseases. Some strains of Salmonella produce genotoxin and extracellular polymeric substances called “biofilm” that support the survival of this bacterium. From this study, phages were applied to control cytolethal distending toxin B (CdtB)-producing, antibiotic-resistant, and biofilm-producing Salmonella isolated from the broiler sources. Out of 116 isolates, only 11 isolates (9.5%) representing six serovars were characterized. Of these, seven isolates were characterized as multidrug-resistant (MDR), three were resistant to one antibiotic, and only one isolate was susceptible to all antibiotics tested. For biofilm formation ability, 18.2% of the isolates were identified as strong biofilm producers, while 63.6% and 18.2% were moderate and weak, respectively. Up to 12 Salmonella phages from our collection were chosen to test their ability on given Salmonella. All the phages showed a strong lytic ability up to 90.9%. Three phages with the highest lysis potential (100% lytic ability) were further selected for a phage cocktail preparation, including WPX5, WPX8, and WPX9. Overall, the phage cocktail completely reduced representative Salmonella counts by three log units in vitro at a multiplicity of infection (MOI) of 104 and 105 at 6 h of treatment. The phage cocktail was tested to reduce Salmonella on different food contact surfaces. At MOI at 103, the highest reduction of Salmonella attachment was observed in stainless steel surfaces, indicated by a 67% reduction, followed by polyvinyl chloride (PVC) and ceramic by 64% and 58%, respectively. These results suggest that a developed phage cocktail could be a potential biocontrol to control toxin-producing, biofilm-producing, and MDR Salmonella in the poultry industry.

Degradation of extracellular antibiotic resistance genes using peracetic acid (PAA) and performic acid (PFA)

Antibiotic resistant bacteria (ARB) associated infections are identified as a major threat to human health in the 21st century. Wastewater contains antibiotic resistance determinants and they are discharged to aquatic environments with treated or untreated effluents. These antibiotic resistance determinants can be taken up by environmental bacteria via horizontal gene transfer (HGT) and they can become antibiotic resistant. Among antibiotic resistance determinants, extracellular DNA containing antibiotic resistance genes can be up taken by environmental bacteria via natural transformation. Therefore, we evaluated the suitability of low-cost disinfectants peracetic acid (PAA) and performic acid (PFA) on inactivating total and functional extracellular ARGs in ultrapure water and secondary wastewater effluent matrices using pUC19 as a model ARG. Performance of PAA and PFA in inactivating extracellular ARGs was compared with the performance of free chlorine disinfection. RT-qPCR results showed that inactivation of ampR gene in pUC19 plasmid suspended in ultrapure water and wastewater secondary effluent by free chlorine was higher compared to PAA and PFA. However, the reduction of functional pUC19 by PAA and PFA were comparable to free chlorine. Transformation frequency of pUC19 treated by PAA and PFA achieved the maximum possible reduction within a shorter time compared to free chlorine treatment, highlighting the possibility of having disinfection chambers with smaller footprints in wastewater treatment plants. These results suggest the suitability of PAA and PFA for inactivation of ARGs in aquatic samples as alternative disinfectants to free chlorine.

Surveillance of Antimicrobial Resistance Bacteria in a Healthcare Facility at an Industrial Site in Saudi Arabia.

This study aimed to perform surveillance and identify antimicrobial resistance (AMR) in the most common pathogenic bacteria in a healthcare facility in Rabigh City, Saudi Arabia. A total of 1,933 samples were processed from patients during the study period from January 2022 to June 2022. Identification and antimicrobial susceptibility of the cultured isolates were performed using the MicroScan system. Out of the 1,933 tested samples, 11.1% (n = 214) were positive for bacterial growth. A relatively higher percentage of isolates was recovered from patients older than 50 years (55.9%). Gram-negative bacteria (67.3%) were significantly more prevalent than Gram-positive bacteria (32.7%). The Gram-negative pathogenic bacteria comprised mainly Escherichia coli and Klebsiella pneumoniae, followed by Pseudomonas aeruginosa. Staphylococ-cus epidermidis and coagulase-negative staphylococci were found at relatively high abundance in Gram-positive bacteria. Increased resistance to carbapenem antibiotics was observed in K. pneumoniae. In Gram-positive bac¬teria, > 50% of the isolates of S. epidermidis were resistant to 13 tested antimicrobial agents. This study provided an overview of the distribution of pathogenic bacteria and antimicrobial susceptibility of the prevalent Gram-negative and Gram-positive pathogenic bacteria in a major healthcare facility in Saudi Arabia. It highlights the importance of continuously monitoring AMR bacteria in healthcare settings to ensure the effective use of antibiotics for treatment.

New Insights into the Antibacterial Activity of Hydroxytyrosol Extracted from Olive Leaves: Molecular Docking Simulations of its Antibacterial Mechanisms.

This study investigated the biological activities of a hydroxytyrosol-rich extract from Olea europaea leaves, particularly its ability to eradicate severe pathogenic bacteria producing Extended-Spectrum Beta-Lactamases (ESBLs). The latter bacteria are emerging microorganisms that pose significant challenges due to their resistance to a broad range of potent therapeutic drugs. The extract was prepared through an accessible acid hydrolysis method. In vitro and In silico analyses through MIC, MBC analysis and molecular docking were conducted to evaluate the antibacterial properties. The extract showed remarkable antioxidant activity and significant antibacterial potential against reference species and ESBL bacteria. MIC and MBC calculations confirmed the extract's capacity to kill bacteria rather than just inhibit their growth. Further in silico analyzes demonstrated the high binding affinity of HT to the active sites of the gyrase B subunit and the peptidoglycan DD-transpeptidase domain from proteins located in the cytoplasm and the cell wall of the bacteria, respectively. Results confirmed the structure-activity relationship and the ability of HT to disrupt essential bacterial functions. This study validates the debated antimicrobial potential of HT and highlights its importance as a potential therapeutic agent against resistant bacteria, which is a critical area of research given the global challenge of antibiotic resistance.

Carbapenem resistance in gram-negative pathogens in an Iranian hospital: high prevalence of OXA-type carbapenemase genes.

The widespread dissemination of carbapenem-resistant Gram-negative bacteria poses a significant threat to global public health. This study aimed to investigate the prevalence of carbapenem resistance in Gram-negative bacteria isolated from patients at the Children's Medical Center Hospital, Tehran, Iran, to understand the molecular mechanisms underlying this resistance. During the period spanning from June 2019 to June 2020, 777 Gram-negative bacterial strains were isolated. Antibiotic susceptibility testing was performed according to Clinical and Laboratory Standards Institute. Polymerase chain reaction was used to detect carbapenem resistance genes including bla OXA23, bla OXA24, bla OXA48, bla OXA51, bla OXA58, bla OXA143, bla KPC, bla IMP, bla VIM, and bla NDM. Among the total bacterial isolates, 141 (18.1%) exhibited carbapenem resistance. Escherichia coli was the most prevalent (57.4%), followed by Klebsiella pneumoniae (11.3%) and Acinetobacter baumannii (10.6%). Other notable contributors included Enterobacter spp. (5.7%), Salmonella spp. (3.5%), and Stenotrophomonas maltophilia (2.8%). Citrobacter spp., Proteus mirabilis, and Pseudomonas aeruginosa contributed to the distributions of two, one, and three isolates, respectively. Notably, bla OXA48 showed the highest prevalence (33%), followed by bla OXA143 and bla OXA58 (27% and 24%, respectively). In addition, bla OXA24 was present in 11% of the total isolates, bla OXA23 in 10%, and bla NDM in 10%, whereas bla KPC, bla VIM, and bla IMP were not detected. Our study highlights the prevalence of carbapenemase-producing Gram-negative isolates among pediatric patients. Notable resistance patterns, especially in K. pneumoniae and E. coli, underline the urgent need for proactive interventions, including appropriate antibiotic prescription practices and strengthening of antibiotic stewardship programs.

Guanethidine Enhances the Antibacterial Activity of Rifampicin Against Multidrug-Resistant Bacteria

The escalating global threat of antibiotic resistance necessitates innovative strategies, such as the combination of antibiotics with adjuvants. Monotherapy with rifampicin is more likely to induce resistance in pathogens compared to other antibiotics. Herein, we found that the antihypertensive drug guanethidine enhanced the activity of rifampicin against certain clinically resistant Gram-negative bacteria, resulting in a reduction of up to 128-fold in the minimum inhibitory concentration. In infected animal models, this combination has achieved treatment benefits, including increased survival and decreased bacterial burden. The antimicrobial mechanism of guanethidine in synergy with rifampicin involves the disruption of the outer membrane of Gram-negative bacteria, leading to dissipation of the proton motive force. This results in an increase in reactive oxygen species and a reduction in ATP synthesis, severely disturbing energy metabolism and ultimately increasing bacterial mortality. In summary, guanethidine has the potential to become a novel adjuvant for rifampicin, offering a new option for the treatment of clinical Gram-negative bacterial infections.

Use of stable isotope combined with intact cell lipidomic by routine MALDI mass spectrometry analysis for rapid drug susceptibility assay in mycobacteria.

Rapid, accurate, and easy-to-perform diagnostic assays are required to address the current need for the diagnosis of resistant pathogens. That is particularly the case for mycobacteria, such as the human pathogen Mycobacterium tuberculosis, which requires up to 2weeks for the determination of the drug susceptibility profile using the conventional broth microdilution method. To address this challenge, we investigated the incorporation of deuterium, the stable isotope of hydrogen, into lipids as a read out of the drug susceptibility profile. Deuterium is incorporated into newly synthesized proteins or lipids in place of hydrogen as bacterial cells grow, increasing the mass of the macromolecules, which can then be observed via matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). As proof-of-concept, we used the non-pathogenic Mycobacterium smegmatis mc2155 strain, which is susceptible to the aminoglycoside antibiotic kanamycin, and M.smegmatis mc2155 containing the empty vector pVV16, which is kanamycin-resistant. Bacteria were incubated in a culture medium containing 50% of deuterium oxide (D2O) and either 1 or 2 times the minimal inhibitory concentration (MIC50) of kanamycin. Lipids were then analyzed using the MBT lipid Xtract matrix combined with routine MALDI mass spectrometry in the positive ion mode to evaluate the changes in the lipid profile. Using this approach, we were able to distinguish susceptible from resistant bacteria in less than 5h, a process that would take 72 h using the conventional broth microdilution method. We therefore propose a solution for the rapid determination of drug susceptibility profiles using a phenotypic assay combining D2O stable isotope labelling and lipid analysis by routine MALDI mass spectrometry.

Detection of Efflux pump MexX and MexY genes in Multidrug Resistant Pseudomonas aeruginosa

High antibiotic resistance among Pseudomonas aeruginosa could be viewed as the primary cause of nosocomial infections. In this study, 60 isolates of Pseudomonas aeruginosa were isolated from urine, sputum, burn, ear and wounds swab. The major goal was to determine the relationship between MexX and MexY and the resistance of MDR P. aeruginosa to many drugs. Prevalence of multidrug resistant (MDR) Pseudomonas aeruginosa was 22 isolates (36.66%) and 38 isolates (63.34%) were found to be non-MDR isolates. Moreover, molecular detection of MexX and MexY genes was done for MDR isolates.MexY gene was found in all MDR isolates and MexX gene was detected in 20 (90.9%) MDR isolates. Susceptibility test showed highly significant differences p≤0.01. Highest resistance was found against piperacillin/sulbactam (45%), followed by ceftazidime/avibactam with 33.33%, and by ceftolozane/tazobactam and levofloxacin which shared same percentage at 31.67%. Almost 23.33% were less resistant to both doripenem and colistin, and 25% to tobramycin. All these findings confirmed a positive correlation between the presence of MexX and MexY genes and an increase in the resistance for all antibiotics used in this study the results of which were highly significant at p≤0.01 for all antibiotics. The study found that some antibiotics that had not been studied previously, also had a relationship with the presence of these genes and the resistance of bacteria to antibiotics such as penicillin, unlike it was previously believed that they do not have relation with the efflux pump mechanism in P. aeruginosa and that this bacterium use other mechanisms to resist them.