Multidrug-resistant Clinical Isolates Research Articles

JIB-04, an inhibitor of Jumonji histone demethylase as a potent antitubercular agent against Mycobacterium tuberculosis.

The increasing drug resistance of Mycobacterium tuberculosis (Mtb), coupled with the limited availability of effective anti-tuberculosis medications, poses significant challenges for the management and treatment of tuberculosis (TB). Globally, non-tuberculous mycobacteria (NTM) infections are increasing, with Mycobacterium avium complex and Mycobacterium abscessus (Mab) being the most common in labs and having few treatment options. There's an urgent need for innovative therapies against Mtb and NTM that are effective and have minimal side effects. The study evaluated the in vitro efficacy of JIB-04, a Jumonji histone demethylase inhibitor, against Mtb, Mab, and multidrug-resistant (MDR) clinical isolates using the minimum inhibitory concentration (MIC) assay. We also determined the minimum bactericidal concentrations (MBCs) of JIB-04 against the H37Rv and H37Ra strains. A time-kill assay was performed to assess the comparative efficacy of JIB-04 and rifampicin against H37Ra. Additionally, the study investigated the impact of JIB-04 on biofilm formation and the persistence of H37Ra over extended periods. Our findings demonstrated a substantial inhibitory effect of JIB-04 on the growth of Mab, Mtb, and MDR clinical isolates. JIB-04 showed bactericidal effects at twice the MIC, outperforming rifampicin in reducing viable cell counts over 8 days. It showed moderate cytotoxicity to mammalian cells but effectively inhibited biofilm formation. In our anoxia model, JIB-04 induced a significant, concentration-dependent reduction in bacterial load. JIB-04 is a promising candidate for the treatment of MDR tuberculosis.

A peptide targeting outer membrane protein A of Acinetobacter baumannii exhibits antibacterial activity by reducing bacterial pathogenicity.

The World Health Organization has classified multidrug-resistant (MDR) Acinetobacter baumannii as a significant threat to human health, necessitating the urgent discovery of new antibacterial drugs to combat bacterial resistance. Outer membrane protein A of A. baumannii (AbOmpA) is an outer membrane-anchored β-barrel-shaped pore protein that plays a critical role in bacterial adhesion, invasion, and biofilm formation. Therefore, AbOmpA is considered a key virulence factor of A. baumannii. Herein, we screened three phage display peptide libraries targeting AbOmpA and identified several peptides. Among them, P92 (amino acid sequence: QMGFMTSPKHSV) exhibited the highest binding affinity with AbOmpA, with a KD value of 7.84 nM. In vitro studies demonstrated that although P92 did not directly inhibit bacterial growth, it significantly reduced the invasion and adhesion capabilities of multiple clinical isolates of MDR A. baumannii and concentration-dependently inhibited biofilm formation by acting on OmpA. Furthermore, the polymerase chain reaction results confirmed a significant positive correlation between the antibacterial effect of P92 and OmpA expression levels. Encouragingly, P92 also displayed remarkable therapeutic efficacy against A. baumannii infection in various models, including an in vitro cell infection model, a mouse skin infection model, and a mouse sepsis model. These results highlight P92 as a novel and highly effective antimicrobial molecule specifically targeting the virulence factor AbOmpA.

Linear and Polyvalent Peptides with Potent Antimicrobial Activity Against Sensitive and Multidrug-Resistant E. c oli Clinical Isolates.

Peptides containing the sequences 20RRWQWR25 and 20RRWQWRMKKLG30 derived from Bovine lactoferricin (LfcinB) were synthesized and their antibacterial effect against reference strains and sensitive and resistant clinical isolates of E. coli was evaluated. Tetra-branched multiple antigen peptide (MAP) ((RRWQWR)2-K-Ahx-C)2 exhibited significant antibacterial activity against sensitive, resistant, and multidrug-resistant clinical isolates of E. coli. Peptide 3: RRWQWR-Nal-KKLG; MIC=16 μM, 26[F]: (RRWQWRFKKLG)2-K-Ahx; MIC=15 μM, 17: (RRWQWRFK)2-K-Ahx; MIC=9 μM, and LfcinB (20-25)2: (RRWQWR)2-K-Ahx; MIC=11 μM exhibited the highest antibacterial activity against E. coli strains, with bactericidal effect and haemolytic effect at MIC less than 5 % and a therapeutic index >1. A synergistic effect of peptides 26[F] and 17 with ciprofloxacin (CIP) or ceftriaxone (CEF) was observed. Prolonged treatment of E. coli ATCC 25922 with sublethal concentrations of CIP induced resistance in this strain, whereas some peptides did not induce resistance. These peptides can be considered to be promising candidates for treating infections caused by resistant strains of E. coli.

Characterization of bla NDM in two Escherichia coli ST1193 clinical isolates in the Gulf region.

Escherichia coli ST1193 is an emerging high-risk clone associated with the production of plasmid-mediated CTX-type extended-spectrum β-lactamases. However, this clone has seldom been found to contain plasmids carrying carbapenemase genes. We report two epidemiologically unlinked multidrug-resistant (MDR) clinical isolates of E. coli ST1193 with plasmids harbouring NDM-type carbapenemase genes from the Gulf region. The isolates were identified by MALDI-TOF MS and antibiotic susceptibility testing was performed using the VITEK 2/Phoenix system. A conjugation experiment was performed to assess the transferability of the resistance plasmids. Genomic DNA of both isolates was subject to Illumina sequencing; one isolate was also sequenced using Oxford Nanopore technology. Bioinformatics analyses were performed to detect antimicrobial resistance genes, and to annotate the genetic context of the NDM genes. Both isolates were resistant to carbapenems using phenotypic tests. Conjugation experiment confirmed that NDM-5-encoding plasmids of both strains could be transferred to the recipient cells. The completed NDM-5-encoding plasmid of E. coli isolate FQ71 was highly similar to several plasmids from ST410 isolates in the NCBI database. Genomic analysis revealed the presence of transposase genes and transposons in the flanking regions of the NDM genes in the plasmids. Since carbapenems constitute first-line agents for the treatment of serious infections caused by ESBL producers, E. coli ST1193 isolates co-producing ESBL and NDM-type carbapenemases represent a serious challenge for antimicrobial stewardship and infection control programmes.

Antimicrobial activity of α/β hybrid peptides incorporating tBu-β3,3Ac6c against methicillin-resistant Staphylococcus aureus.

The incorporation of β-amino acids into peptides is a promising approach to develop proteolytically stable therapeutic agents. Short α/β hybrid peptidescontaining tBu-β3,3Ac6cː H2N-Lys-tBu-β3,3Ac6c-PEA, P1; H2N-Orn-tBu-β3,3Ac6c-PEA, P2; H2N-Arg-tBu-β3,3Ac6c-PEA, P3; LA-Lys-tBu-β3,3Ac6c-PEA, P4; LA-Orn-tBu-β3,3Ac6c-PEA, P5; LA-Arg-tBu-β3,3Ac6c-PEA, P6; LAu-Lys-tBu-β3,3Ac6c-PEA, P7; LAu-Orn-tBu-β3,3Ac6c-PEA, P8; and LAu-Arg-tBu-β3,3Ac6c-PEA, P9 were prepared. The antimicrobial efficacies of all the peptides were evaluated against ESKAPE pathogens, along with a small panel of multi-drug resistant (MDR) clinical isolates of S. aureus. Among all the peptides, P4, P6, and P7 showed significant efficacies against P. aeruginosa, S. aureus, and MRSA with an MIC value ranging from 6.25 to 12.5 μM. Further, in vitro, anti-staphylococcal assessment with their antimicrobial synergy of the peptides P4, P6, and P7 was carried out against MRSA, due to its better efficacy. The peptides P6 and P7 exhibited MRSA biofilm inhibition of 70% and 77%, respectively, at 4×MIC concentration. At its MIC concentration, about 19% hemolysis was observed for P4, P6, and P7.

Conformational Flexibility and Net Charge are Key Determinants for the Antimicrobial Activity of Peptide Uy234 Against Multidrug-resistant Bacteria

BackgroundThe antimicrobial activity of two peptides, Uy234 derived from the venom of the scorpion Urodacus yaschenkoi and a consensus peptide QnCs-Buap, was evaluated. We tested different pathogenic bacteria: Acinetobacter baumannii, Klebsiella pneumoniae, Salmonella enterica, Bacillus subtilis, Enterococcus spp. and Staphylococcus aureus, including one methicillin resistant (MRSA) and two multidrug resistant (MDR) clinical isolates. In contrast to the QnCs-Buap peptide, Uy234 showed relevant growth inhibitory activity on A. baumannii and B. subtilis, and mostly on S. aureus strains.ObjectiveThe present research focused on elucidating the mechanism for this antibacterial activity.MethodologyWe carried out an in-depth analysis of the composition, structure, flexibility, and physicochemical properties of both peptides.ResultsWe found a crucial role of the C-terminal amide and composition in favoring the formation of a dense H-bond network in the Uy234 peptide. This H-bonding network slightly stiffens the peptide and keeps it in a preordered conformation in the aqueous phase.ConclusionsWe hypothesize that, given that Uy234 is a very short peptide (18 aa), it could have a destabilizing effect and favor micellization phenomena instead forming pores. In contrast, the QnCs-Buap peptide (13 aa), having only the positive charge at the N-terminal end and being significantly more hydrophobic and rigid, is not capable of overcoming the energy barrier to disturb the membrane. We propose that Uy234 peptide can be a scaffold to develop new derivatives with high potential against infections caused by diverse multidrug-resistant bacteria.Graphical

Bactericidal and Synergistic Effects of Lippia origanoides Essential Oil and Its Main Constituents against Multidrug-Resistant Strains of Acinetobacter baumannii.

Bacterial resistance in Acinetobacter baumannii is a significant public health challenge, as these bacteria can evade multiple antibiotics, leading to difficult-to-treat infections with high mortality rates. As part of the search for alternatives, essential oils from medicinal plants have shown promising antibacterial potential due to their diverse chemical constituents. This study evaluated the antibacterial, antibiofilm, and synergistic activities of the essential oil of Lippia origanoides (EOLo) and its main constituents against multidrug-resistant clinical isolates of A. baumannii. Additionally, the antibacterial and antibiofilm potential of a nanoemulsion containing carvacrol (NE-CAR) was assessed. EOLo was extracted through hydrodistillation, and its components were identified via gas chromatography coupled with mass spectrometry. The A. baumannii isolates (n = 9) were identified and tested for antimicrobial susceptibility using standard disk diffusion methods. Antibacterial activity was determined by broth microdilution, while antibiofilm activity was measured using colorimetric methods with crystal violet and scanning electron microscopy. Synergism tests with antibiotics (meropenem, ciprofloxacin, gentamicin, and ampicillin+sulbactam) were performed using the checkerboard method. The primary constituents of EOLo included carvacrol (48.44%), p-cymene (14.58%), and thymol (10.16%). EOLo, carvacrol, and thymol demonstrated significant antibacterial activity, with carvacrol showing the strongest effect. They were also effective in reducing biofilm formation, as was NE-CAR. The combinations with antibiotics revealed significant synergistic effects, lowering the minimum inhibitory concentration of the tested antibiotics. Therefore, this study confirms the notable antibacterial activity of the essential oil of L. origanoides and its constituents, especially carvacrol, suggesting its potential as a therapeutic alternative for A. baumannii infections.

Synergistic invitro antimicrobial activity of polyherbal combination of Morinda lucida fruit and Pterocarpus santalinoides seed against multi-drug resistant clinical bacterial isolates

Background: Synergistic drug combination has been shown to be a way of bypassing drug resistance and reducing the amounts of antimicrobials consumed. As infections caused by multi-drug resistant organisms (MDROs) continue to pose global threat, it is important to search for new antimicrobial combinations of plant origin that are safe and readily available. The objective of this study is to evaluate the synergistic antimicrobial activity of extracts of Morinda lucida fruit and Pterocarpus santalinoides seed against multi-drug resistant (MDR) bacterial isolates Methodology: Morinda lucida and P. santalinoides fruits were plucked and washed clean, and the fruits of P. santalinoides were deseeded to remove the seeds. They were cut into smaller pieces and dried under shade before being milled into smooth powder and extracted with methanol. The clinical bacterial isolates used were MDR Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus. The phytochemical constituents of the extracts were determined using the standard method. The invitro antimicrobial assay of the extracts was done at a concentration of 50 to 400 mg/ml using the agar well diffusion technique. The minimum inhibitory concentration (MIC) and fractional inhibitory concentration (FIC) of each extract were determined using the Checker-board micro-titration method, and the FIC result obtained for each isolate was used to calculate the fractional inhibitory concentration index (FICI) of the combined extracts. The time kill assay was performed to confirm the synergistic and bactericidal activities from the MIC values obtained. Results: The phytochemical analysis revealed that the extracts of both herbal plants contained alkaloids, phenol, tannin, saponin, glycosides, and terpenoids. The antimicrobial assay results showed that the polyherbal combination of the extracts was active against all the MDR bacterial isolates tested with varying zones of inhibition. The mean inhibition zone diameters of individual M. lucida and P. santalinoides ranged from 18.0±0.9mm to 26.0±1.4mm and 17.0±0.1mm to 24.0±0.2mm respectively, while the MIC ranged from 6.25mg/ml to 12.5mg/ml for M. lucida and 12.5 mg/ml for P. santalinoides. The mean inhibition zone diameter of the polyherbal combination of the two plant extracts ranged from 25.00±00mm to 34.0±0.4mm, which compared favorably with that of levofloxacin control (28.0±0.0mm to 32.00±0.0mm), while their MIC ranged from 0.39mg/ml to 1.56mg/ml. The FIC of M. lucida extract ranged from 0.06mg/ml to 0.25mg/ml while that of P. santalinoides ranged from 0.03mg/ml to 0.13mg/ml. The FICI of combined extracts ranged from 0.09mg/ml to 0.38 mg/ml for all the MDR isolates, which is less than 0.5mg/ml, indicating synergism against all the isolates. The time of kill assay confirmed the synergistic and bactericidal activities with a 3log10 CFU/ml decrease in the number of viable cells within 6 hours of incubation.Conclusion: Our findings showed synergistic antibacterial actions of extracts of M. lucida fruit and P. santalinoides seed against MDR clinical bacterial isolates, comparable to levofloxacin. Combination of these herbal plants may serve as alternative sources of antimicrobial agents for the treatment of infections caused by MDR bacterial pathogens.

Heterologous Production of Bacteriocin EMM1 from Pseudomonas Protegens and its Antimicrobial Activity against Multidrug-resistant Clinical Isolates

Heterologous Production of Bacteriocin EMM1 from Pseudomonas Protegens and its Antimicrobial Activity against Multidrug-resistant Clinical Isolates

3,5-disubstituted pyridines with potent activity against drug-resistant Mycobacterium tuberculosis clinical isolates.

Aim: We designed and synthesized a series of compounds with a 3,5-disubstituted pyridine moiety and evaluated them against Mycobacterium tuberculosis (Mtb) and drug-resistant Mtb clinical isolates.Methodology: A library of 3,5-disubstituted pyridine was synthesized. The compounds were screened for activity against M. tuberculosis H37Rv. The optimal substitutions needed for the activity were identified through structure-activity relationship (SAR) studies.Results: From the screening studies, compounds 24 and 26 were identified as potent members of this series with Minimum Inhibitory Concentration (MIC) of 1.56μg/ml against M. tuberculosis H37Rv. These compounds did not show any inhibition against a panel of ESKAPE pathogens at >50μg/ml indicating their selective killing of M. tuberculosis H37Rv. Importantly, compound 24 showed a selectivity index of 54.64 against CHO-K1 and 78.26 against VERO cell lines, while compound 26 showed a selectivity index of 108.5 against CHO-K1 and 63.2 against VERO cell lines, respectively. Compound 24 formed a stable complex with the target protein DprE1 with predicted binding energy -8.73kcal/mol and inhibited multidrug-resistant clinical isolate of M. tuberculosis at 6.25μg/ml.Conclusion: This study identified the 3,5-disubstituted pyridine derivative 24 with potent antituberculosis activity and can be taken forward to generate new preclinical candidate.

The Diverse Activities and Mechanisms of the Acylphloroglucinol Antibiotic Rhodomyrtone: Antibacterial Activity and Beyond.

Background/Objectives: The rose myrtle Rhodomyrtus tomentosa is a medicinal plant used in traditional Asian medicine. The active compound in R. tomentosa leaf extracts is rhodomyrtone, a chiral acylphloroglucinol. Rhodomyrtone exhibits an impressive breadth of activities, including antibacterial, antiviral, antiplasmodial, immunomodulatory, and anticancer properties. Its antibacterial properties have been extensively studied. Methods: We performed a comprehensive literature review on rhodomyrtone and summarized the current knowledge about this promising acylphloroglucinol antibiotic and its diverse functions in this review. Results: Rhodomyrtone shows nano to micromolar activities against a broad range of Gram-positive pathogens, including multidrug-resistant clinical isolates, and possesses a unique mechanism of action. It increases membrane fluidity and creates hyperfluid domains that attract membrane proteins prior to forming large membrane vesicles, effectively acting as a membrane protein trap. This mechanism affects a multitude of cellular processes, including cell division and cell wall synthesis. Additionally, rhodomyrtone reduces the expression of inflammatory cytokines, such as TNF-α, IL-17A, IL1β, and IL8. Generally showing low toxicity against mammalian cells, rhodomyrtone does inhibit the proliferation of cancer cell lines, such as epidermal carcinoma cells. The primary mechanism behind this activity appears to be the downregulation of adhesion kinases and growth factors. Furthermore, rhodomyrtone has shown antioxidant activity and displays cognitive effects, such as decreasing depressive symptoms in mice. Conclusions: Rhodomyrtone shows great promise as therapeutic agent, mostly for antibacterial but also for diverse other applications. Yet, bottlenecks such as resistance development and a better understanding of mammalian cell toxictiy demand careful assessment.

Identification of novel antistaphylococcal hit compounds.

Staphylococcus aureus is one of the most common nosocomial biofilm-forming pathogens worldwide that has developed resistance mechanisms against majority of the antibiotics. Therefore, the search of novel antistaphylococcal agents with unexploited mechanisms of action, especially with antibiofilm activity, is of great interest. Seryl-tRNA synthetase is recognized as a promising drug target for the development of antibacterials. We have carried out molecular docking of compounds with antistaphycoccal activity, which were earlier found by us using phenotypic screening, into synthetic site of S. aureus SerRS and found seven hit compounds with low inhibitory activity. Further, we have performed search of S. aureus SerRS inhibitors among compounds which were previously tested by us for inhibitory activity toward S. aureus ThrRS, that belong to the same class of aminoacyl-tRNA synthetases. Among them six hits were identified. We have selected four compounds for antibacterial study and found that the most active compound 1-methyl-3-(1H-imidazol-1-methyl-2-yl)-5-nitro-1H-indazole has MIC values toward S. aureus multidrug-resistant clinical isolates ranging from 78.12 to 156.2 µg/ml. However, this compound precipitated during anti-biofilm study. Therefore, we used 3-[N'-(2-hydroxy-3-methoxybenzylidene)hydrazino]-6-methyl-4H-[1,2,4]triazin-5-one with better solubility (ClogS value = 2.9) among investigated compounds toward SerRS for anti-biofilm study. It was found that this compound has a significant inhibitory effect on the growth of planktonic and biofilm culture of S. aureus 25923 with MIC value of 32 µg ml-1. At the same time, this compound does not reveal antibacterial activity toward Esherichia coli ATCC 47076. Therefore, this compound can be proposed as effective antiseptic toward multidrug-resistant biofilm-forming S. aureus isolates.

PH-mediated potentiation of gallium nitrate against Pseudomonas aeruginosa.

The emergence of multidrug-resistant Pseudomonas aeruginosa isolates is a growing concern for public health, necessitating new therapeutic strategies. Gallium nitrate [Ga(NO3)3], a medication for cancer-related hypercalcemia, has attracted great attention due to its ability to inhibit P. aeruginosa growth and biofilm formation by disrupting iron metabolism. However, the antibacterial efficacy of Ga(NO3)3 is not always satisfactory. It is imperative to investigate the factors that affect the bactericidal effects of Ga(NO3)3 and to identify new ways to enhance its efficacy. This study focused on the impact of pH on P. aeruginosa resistance to Ga(NO3)3, along with the underlying mechanism. The results indicate that acidic conditions could increase the effectiveness of Ga(NO3)3 against P. aeruginosa by promoting the production of pyochelin and gallium uptake. Subsequently, using glutamic acid, a clinically compatible acidic amino acid, the pH was significantly lowered and enhanced the bactericidal and inhibitory efficacy of Ga(NO3)3 against biofilm formation by P. aeruginosa, including a reference strain PA14 and several multidrug-resistant clinical isolates. Furthermore, we used an abscess mouse model to evaluate this combination in vivo; the results show that the combination of glutamic acid and Ga(NO3)3 significantly improved P. aeruginosa clearance. Overall, the present study demonstrates that acidic conditions can increase the sensitivity of P. aeruginosa to Ga(NO3)3. Combining glutamic acid and Ga(NO3)3 is a potential strategy for the treatment of P. aeruginosa infections.

Polymyxin B adjuvants against polymyxin B- and carbapenem-resistant Gram-negative bacteria.

Aim: Polymyxin B (PMB) is one of the few therapeutic options for treating infections caused by carbapenem-resistant Gram-negative bacteria (CR-GNB). However, the emergence of PMB-resistant CR-GNB strains has prompted the exploration of antibiotic adjuvants as potential therapeutic avenues. Thus, this study evaluates the potential of 3,5-dinitrobenzoic acid derivatives (DNH01, DNH11, DNH13 and DNH20) and isoniazid-N-acylhydrazones (INZ1-7, INZ9 and INZ11) as adjuvants to enhance PMB efficacy against CR-GNB.Materials & methods: MIC, MBC and drug combination assays were conducted using multidrug-resistant clinical isolates of Enterobacterales and Acinetobacter baumannii. In addition, the effects of PMB and PMB+DNH derivatives were assessed through flow cytometry and scanning electron microscopy (SEM).Results: DNH01, DNH11 and DNH20, unlike the INH-acylhydrazones, significantly restored PMB activity (MIC≤2μg/ml) in 80% of the tested isolates. Flow cytometry and SEM assays confirmed that DNH derivatives rescued the activity of PMB, yielding results comparable to those expected for PMB alone but at 256-fold lower concentrations.Conclusion: These findings suggest DNH derivatives hold substantial promise as PMB adjuvants to combat PMB-resistant CR-GNB infections.

Prevalence of qacEΔ1, qacE, oqxA, oqxB, acrA, cepA and zitB genes among multidrug-resistant Klebsiella pneumoniae isolated in a cardiac hospital

Background. Infections caused by multidrug-resistant (MDR) Klebsiella pneumoniae are the leading cause of mortality worldwide. The widespread use of disinfectants and antiseptics has caused the emergence of K. pneumoniae with reduced sensitivity to them, which, in combination with MDR, can pose a significant epidemiological threat. The aim of the study was to assess the prevalence of efflux pump and transporter genes associated with biocide resistance and their association with antibiotic resistance among K. pneumoniae isolated in a cardiac surgical hospital. Materials and methods. K. pneumoniae isolates (n = 50) from the patients and medical equipment were tested by polymerase chain reaction for the presence of genes of 4 types of efflux pumps (qacEΔ1, qacE, oqxA, oqxB, acrA) and 2 transporters involved in the outflow of cations (cepA) and zinc ions (zitB). Spearman's rank correlation test was used to assess the strength of the association between the efflux pumps, beta-lactamase genes and mobile genetic elements. Results. The occurrence of K. pneumoniae containing qacEΔ1, qacE, oqxA, oqxB, acrA, cepA and zitB was high: 54, 62, 100, 84, 100, 72 и 96% respectively. K. pneumoniae with a combination of all the studied pumps was most often detected (32%), and these isolates were MDR in 100% of cases. The qacE, qacEΔ1 genes were closely associated with resistance to cephalosporins, carbapenems, fluoroquinolones, carbapenemase genes, and integrons. The results of the study showed that the genes of various efflux pumps associated with biocide resistance and their combinations were widely represented among the clinical isolates of MDR K. pneumoniae. Conclusion. The high prevalence of efflux pump genes associated with resistance to quaternary ammonium compounds, chlorhexidine and zinc salts and their significant association with antibiotic resistance in nosocomial K. pneumoniae underlines the importance of further studying the mechanisms of cross-resistance to biocides to improve methods of combating MDR nosocomial pathogens.

Minimum inhibitory and bactericidal/fungicidal concentration of commercially available products containing essential oils, zinc gluconate, or 4% chlorhexidine for Malassezia pachydermatis, Pseudomonas aeruginosa, and multi-drug resistant Staphylococcus pseudintermedius canine clinical isolates.

Skin infections are common complications in both humans and animals. Because of the increased incidence of multi-drug resistant (MDR) skin infections, essential oils have been suggested as potential alternatives to the classic antimicrobials. The goal of this study was to evaluate the minimum inhibitory and bactericidal/fungicidal concentrations (MIC and MBC/MFC) of commercially available products containing essential oils, zinc gluconate, or 4% chlorhexidine. Microbroth dilution technique was performed on clinical isolates of MDR Staphylococcus pseudintermedius (MDR-SP; n = 10), Pseudomonas aeruginosa (PA; n = 10), and Malassezia pachydermatis (MP; n = 10). For MDR-SP, essential oil-containing products showed median MICs of 1:240 and 1:320. The chlorhexidine shampoo had a MIC of 1:128,000 (0.312µg/mL), whereas zinc gluconate products had median MICs of 1:320 and 1:160. Three essential oil-containing shampoos (MBC 1:40), the zinc gluconate (MBC 1:40), and the chlorhexidine (MBC 1:64,000 [0.625µg/mL]) reached an MBC. For PA, essential oil-containing products showed median MICs of 1:30 and 1:80. The zinc-gluconate products had a median MIC of 1:160, whereas the chlorhexidine shampoo had a median MIC of 1:4,000 (10µg/mL). Only the zinc-gluconate products (MBC 1:80) and the chlorhexidine shampoo (MBC 1:2,000 [20µg/mL]) reached an MBC. For MP, essential oil-containing and zinc-gluconate products showed lower median MICs (1:4,800 and 7,200) for shampoos compared with other formulations (1:160 and 1:320), whereas the chlorhexidine shampoo had a median MIC of 1:80,000 (0.5µg/mL). These results suggest that natural topical compounds can be an effective alternative to treat skin infections in companion animals. Further in vivo studies are needed to clinically confirm this study's results.

Discovery and Biosynthesis of Persiathiacins: Unusual Polyglycosylated Thiopeptides Active Against Multidrug Resistant Tuberculosis.

Thiopeptides are ribosomally biosynthesized and post-translationally modified peptides (RiPPs) that potently inhibit the growth of Gram-positive bacteria by targeting multiple steps in protein biosynthesis. The poor pharmacological properties of thiopeptides, particularly their low aqueous solubility, has hindered their development into clinically useful antibiotics. Antimicrobial activity screens of a library of Actinomycetota extracts led to discovery of the novel polyglycosylated thiopeptides persiathiacins A and B from Actinokineospora sp. UTMC 2448. Persiathiacin A is active against methicillin-resistant Staphylococcus aureus and several Mycobacterium tuberculosis strains, including drug-resistant and multidrug-resistant clinical isolates, and does not significantly affect the growth of ovarian cancer cells at concentrations up to 400 μM. Polyglycosylated thiopeptides are extremely rare and nothing is known about their biosynthesis. Sequencing and analysis of the Actinokineospora sp. UTMC 2448 genome enabled identification of the putative persiathiacin biosynthetic gene cluster (BGC). A cytochrome P450 encoded by this gene cluster catalyzes the hydroxylation of nosiheptide in vitro and in vivo, consistent with the proposal that the cluster directs persiathiacin biosynthesis. Several genes in the cluster encode homologues of enzymes known to catalyze the assembly and attachment of deoxysugars during the biosynthesis of other classes of glycosylated natural products. One of these encodes a glycosyl transferase that was shown to catalyze attachment of a D-glucose residue to nosiheptide in vitro. The discovery of the persiathiacins and their BGC thus provides the basis for the development of biosynthetic engineering approaches to the creation of novel (poly)glycosylated thiopeptide derivatives with enhanced pharmacological properties.

Design, Synthesis, and Anticancer and Antibacterial Activities of Quinoline-5-Sulfonamides.

A series of new unique acetylene derivatives of 8-hydroxy- and 8-methoxyquinoline- 5-sulfonamide 3a-f and 6a-f were prepared by reactions of 8-hydroxy- and 8-methoxyquinoline- 5-sulfonyl chlorides with acetylene derivatives of amine. A series of new hybrid systems containing quinoline and 1,2,3-triazole systems 7a-h were obtained by reactions of acetylene derivatives of quinoline-5-sulfonamide 6a-d with organic azides. The structures of the obtained compounds were confirmed by 1H and 13C NMR spectroscopy and HR-MS spectrometry. The obtained quinoline derivatives 3a-f and 6a-f and 1,2,3-triazole derivatives 7a-h were tested for their anticancer and antimicrobial activity. Human amelanotic melanoma cells (C-32), human breast adenocarcinoma cells (MDA-MB-231), and human lung adenocarcinoma cells (A549) were selected as tested cancer lines, while cytotoxicity was investigated on normal human dermal fibroblasts (HFF-1). All the compounds were also tested against reference strains Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212 and representatives of multidrug-resistant clinical isolates of methicillin-resistant S. aureus (MRSA) and vancomycin-resistant E. faecalis. Only the acetylene derivatives of 8-hydroxyquinoline-5-sulfonamide 3a-f were shown to be biologically active, and 8-hydroxy-N-methyl-N-(prop-2-yn-1-yl)quinoline-5-sulfonamide (3c) showed the highest activity against all three cancer lines and MRSA isolates. Its efficacies were comparable to those of cisplatin/doxorubicin and oxacillin/ciprofloxacin. In the non-cancer HFF-1 line, the compound showed no toxicity up to an IC50 of 100 µM. In additional tests, compound 3c decreased the expression of H3, increased the transcriptional activity of cell cycle regulators (P53 and P21 proteins), and altered the expression of BCL-2 and BAX genes in all cancer lines. The unsubstituted phenolic group at position 8 of the quinoline is the key structural fragment necessary for biological activity.

Effect of L-arginine on cystic fibrosis Pseudomonas aeruginosa biofilms.

Cystic fibrosis (CF) airways are L-arginine deficient which may affect susceptibility to infection with certain pathogens. The potential impact of L-arginine supplementation on Pseudomonas aeruginosa, a common CF airway pathogen, is unclear. This study investigated the effects of L-arginine on P. aeruginosa biofilm cultures, using the laboratory strain PAO1 and multi-drug resistant CF clinical isolates. P. aeruginosa biofilms were grown in a chambered cover-glass slide model for 24 h, then exposed to either L-arginine alone or combined with tobramycin for an additional 24 h. Biofilms were visualized using confocal microscopy, and viable cells were measured via plating for colony-forming units. Increasing concentrations of L-arginine in bacterial culture medium reduced the biovolume of P. aeruginosa in a dose-dependent manner. Notably, L-arginine concentrations within the physiological range (50 mM and 100 mM) in combination with tobramycin promoted biofilm growth, while higher concentrations (600 mM and 1200 mM) inhibited growth. These findings demonstrate the potential of L-arginine as an adjuvant therapy to inhaled tobramycin in treating P. aeruginosa infections in people with CF.

Prevalence of Extended-Spectrum ß-Lactamases (ESBLs) and AmpC ß-Lactamases in Clinical Isolates of Multiple Drug-Resistant Escherichia coli

The current study aims to investigate the prevalence of extended-spectrum ß-lactamases (ESBLs) and AmpC β-lactamases in multiple-drug-resistant Escherichia coli (e.g., multidrug-resistant (MDR), extensively drug-resistant (XDR), and pan-drug-resistant (PDR)) collected from hospitalized patients in Baghdad. The results showed that the prevalence of ESBLs among E.coli isolates was high. From the total 113 E.coli isolates, 75 (66.37%) were ESBL-producing, while 38 (33.63%) were non-ESBL-producing. Out of 75 ESBL-positive isolates, 39 (52%) were obtained from females and 36 (48%) from males. Additionally, 43 (57.33%) isolates were collected from urine samples, and the highest production of ESBLs was obtained from the age group 41–60 years (29.33%). Moreover, out of 111 MDR E.coli, 64 (57.66%) exhibited a positive ESBL test, while 47 (42.34%) did not. Out of 24 XDR E.coli isolates, 11 (45.83%) demonstrated positive ESBLs, while 13 (54.17%) showed negative ESBLs. The antimicrobial susceptibility test results showed that positive ESBL E.coli isolates were more drug-resistant than negative ESBL isolates. The positive ESBLs of E.coli exhibited a higher resistance rate to the β-lactam antibiotics and showed a co-resistance to non-β-lactam antibiotics. Phenotypic detection of AmpC β-lactamase by the screening of cefoxitin-resistant isolates revealed that 43 (38.05%) isolates were considered positive for AmpC β-lactamase production. However, the PCR technique gives different results. In conclusion, the prevalence of ESBL and AmpC β-lactamase producing E. coli is rapidly increasing among clinical isolates of MDR, XDR, and possibly PDR E.coli.