MDR Strains Research Articles

P13 Association of biofilm production with multidrug resistance in clinical isolates of Pseudomonas aeruginosa

Abstract Background Pseudomonas aeruginosa is among the most important cause of life threatening hospital acquired infections. It is considered as top listed public health threat worldwide due to its ability to produce toxins, virulence factors, biofilms and resist multiple antibiotics. Biofilm formation is a pathogenic mechanism harboured by this pathogen which further elevates its resistance to antibiotics and host defence system. Objectives To detect the phenotypic and genotypic biofilm forming potential and its association with multi drug resistance in P. aeruginosa clinical isolates. Methods In the present study, isolation of P. aeruginosa was performed by conventional and molecular method using polymerase chain reaction (PCR) from (n=200) clinical samples. Kirby Bauer method was performed for detection of MDR isolates. The biofilm forming ability of P. aeruginosa isolates was detected by microtitre plate assay (MPA) while the genes associated with biofilm formation (pelA and pslA) were detected by PCR. Results The results of study revealed that P. aeruginosa was detected in 26% (52/200) isolates with highest frequency 38.63% in burn wound samples followed by 22.22% in sputum samples and 20.58% in surgical wound samples. Highest resistant was found to ceftriaxone (94%) followed by meropenem (92%), imipenem (90%) and cefotaxime (90%) while (n=20) isolates were detected as MDR. Biofilm formation of variable degree was detected in 49 (94%) isolates. Additionally it was recorded that all the MDR isolates exhibits biofilm formation including 55% as moderately, 40% as strongly and 5% as weakly adherent. Among the MDR P. aeruginosa, the biofilm-associated gene pelA was detected in 95% while pslA was found in 90% isolates. Conclusions It was concluded that biofilm forming P. aeruginosa are more resistant to tested antibiotics and strongly linked with presence of pelA and pslA genes. This presence of MDR strains along with biofilm formation is depicting a lethal combination of bacterial armory that poses a serious threat for public health.

P10 Phage-encoded lysins as promising antibacterials against uropathogenic Escherichia coli

Abstract Background Urinary tract infections (UTIs) represent a major public health issue. Uropathogenic Escherichia coli (UPEC) is a pathogen implicated in the vast majority of UTIs. Although treatable, the rampant and indiscriminate use of antibiotics has led to an alarming emergence of MDR strains. This can lead to complications, treatment failure, and increased rates of mortality and morbidity. Given the prevalence of these strains, we are exploring phage encoded-lysins as potential alternatives to antibiotics. Objectives Our study involved the development of an in silico strategy for the discovery and characterization of prophage-derived lysin sequences targeting the E. coli cell wall and evaluating the antibacterial activity of the recombinant lysins using in vitro assays. Methods Novel lysin sequences were searched by BLAST homology and by screening E. coli prophages in the database (using PHASTER). They were computationally characterized and their domain architecture was examined. Based on the desired physicochemical properties of the 16 lysins, 7 were selected for cloning, expression, and purification as recombinant proteins for the in vitro antibacterial activity. Results In silico analysis showed lysozyme-like domain in 9 out of 16 lysins and the predicted structure was either modular or globular. Cationic and hydrophobic residues at the C-terminal end and cationic residues in the catalytic domains indicate intrinsic bactericidal activity. Lysins (7) were cloned in pET28 vector and purified as His-tagged recombinant proteins by Ni-NTA chromatography. Using spot assay, 3 out of 7 lysins (9–12 μg) showed lysis of E. coli cells (BL21 DE3). The most promising was lysin sequence 5, which showed lysis of E. coli cells, both at stationary as well as mid-log phase cells. Turbidity reduction assay showed a 74.94% drop in OD600 in lysin (15 μM) treated cells after 3 h of incubation, at 37°C. Log killing assay showed 4 log10 reduction in the treated cells. Lysozyme assay demonstrates higher than / comparable lysozyme activity of lysin sequence 5 with the positive control. Conclusions Sixteen novel prophage-encoded lysin sequences have been identified to create a lysin bank (to screen against E. coli), and 7 of them have been purified. Screening shows three lysins having intrinsic bactericidal activity and hence did not require the addition of an Outer Membrane Permeabilizer (OMP). Lysin sequence 5 has exhibited the highest activity against E. coli cells. Enzyme stability and kinetics studies and screening of clinical isolates of E. coli from UTI patients is underway. Investigating this bank of lysins is aimed at the identification and development of a lead ‘enzybiotic’ with desired PK/PD characteristics against UTI-causing E. coli.

Role of MexAB-OprM efflux pump in the emergence of multidrug-resistant clinical isolates of Pseudomonas aeruginosa in Mazandaran province of Iran.

Multidrug-resistant clinical isolates can cause many therapeutic problems. The MexAB-OprM efflux pump plays a significant role in expelling toxins and drugs from the bacterial cells resulting in multidrug-resistant Pseudomonas aeruginosa isolates. This study aimed to investigate the effect of the MexAB-OprM efflux pump in the emergence of multidrug-resistant clinical isolates of P. aeruginosa. For the present study, 100 clinical isolates of P. aeruginosa were collected from different wards of teaching hospitals (2018-2019). After confirmation and detection of bacteria by standard methods, the antibiotic resistance pattern of the isolates was determined by the disk agar diffusion method. Also, the minimum inhibitory concentration (MIC) of ciprofloxacin was measured in the presence and absence of phenylalanine arginine beta-naphthylamide by the broth microdilution method. Then, the real-time PCR was used to investigate the expression level of the mexB gene compared to the standard PAO1 strain. Forty-one/100 isolates exhibited multidrug-resistant phenotype (MDR), while piperacillin-tazobactam and levofloxacin were the most and least effective antibiotics tested, respectively. Also, 54/100 isolates showed no increased expression of mexB gene compared to the standard PAO1 strain. However, among the 41 MDR isolates, 12 (29.26%) showed a more than three-fold increase in the expression level of the mexB gene. In this study, a significant relationship was observed between the resistance to tested antibiotics in MDR strains and the increased expression of the mexB gene. We found that increasing the expression of the mexB gene can cause the emergence of multidrug-resistant strains by increasing the minimum inhibitory concentration of the antibiotics. Then, we need to evaluate the resistance mechanisms separately in different area of a country to improve the antibiotic stewardship.

Clinicomicrobiological Profile of Podiatric Infections: A Prospective, Cross-sectional Study

Introduction. Podiatric infections are common in patients with and without diabetes. Biofilm detection would aid in determining the severity of foot infections and preventive strategies to manage them. Objective. The authors studied the clinicomicrobiological profile of podiatric infections. Materials and Methods. Organisms from podiatric specimens were identified and the antibiotic susceptibility of the organisms determined using standard microbiological methods. Organisms were screened for biofilm production using the microtiter plate method. Staphylococcus aureus isolates were screened for ica, cna, and hlg genes by multiplex PCR. Results. A total of 117 patients were included in the study, and specimens from 71 patients were culture positive (60.6%). Gram-negative bacteria were predominant (n = 88 [73.3%]). S aureus (n = 32 [26.7%]) was the most common isolate. The rate of biofilm production was 54.2%. Pseudomonas aeruginosa was the most prevalent biofilm producer (82.8%). The study revealed a statistically significant association of biofilm formation with MDR, MRSA, and prior antibiotic therapy with multiple (≥4) antibiotics. Conclusion. Isolation of MRSA or MDR strain from diabetic foot infections could alert the clinician to the possibility of treatment failure with a single drug regimen owing to associated biofilm production. Detection of biofilm producers and subsequent early debridement and/or cleaning of wounds might prevent chronic infection.

Evaluation of antibacterial efficacy and phytochemical analysis of Echinacea purpurea towards MDR strains with clinical origins

Evaluation of antibacterial efficacy and phytochemical analysis of Echinacea purpurea towards MDR strains with clinical origins

A computational study of Di-substituted 1,2,3-triazole derivatives as potential drug candidates against Mycobacterium tuberculosis: 3D-QSAR, molecular docking, molecular dynamics, and ADMETox

Multidrug-resistant TB (MDR TB) strains have become a severe issue, motivating researchers to find new TB drugs effective against these MDR strains.

Histone deacetylase (HDAC) inhibitors- based drugs are effective to control Mycobacterium tuberculosis infection and promote the sensibility for rifampicin in MDR strain.

Tuberculosis (TB) is a major public health problem, which has been aggravated by the alarming growth of drug-resistant tuberculosis. Therefore, the development of a safer and more effective treatment is needed. The aim of this work was repositioning and evaluate histone deacetylases (HDAC) inhibitors- based drugs with potential antimycobacterial activity. Using an in silico pharmacological repositioning strategy, three molecules that bind to the catalytic site of histone deacetylase were selected. Pneumocytes type II and macrophages were infected with Mycobacterium tuberculosis and treated with pre-selected HDAC inhibitors (HDACi). Subsequently, the ability of each of these molecules to directly promote the elimination of M. tuberculosis was evaluated by colony-forming unit (CFU)/mL. We assessed the expression of antimicrobial peptides and respiratory burst using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Aminoacetanilide (ACE), N-Boc-1,2-phenylenediamine (N-BOC), 1,3-Diphenylurea (DFU), reduce bacillary loads in macrophages and increase the production of β-defensin-2, LL-37, superoxide dismutase (SOD) 3 and inducible nitric oxide synthase (iNOS). While only the use of ACE in type II pneumocytes decreases the bacterial load through increasing LL-37 expression. Furthermore, the use of ACE and rifampicin inhibited the survival of intracellular multi-drug resistance M. tuberculosis. Our data support the usefulness of in silico approaches for drug repositioning to provide a potential adjunctive therapy for TB.

Enterococos resistentes isolados de leite cru de ovelha e queijos da região Sul do Brasil

ABSTRACT: Enterococci have been used as sentinel organisms for monitoring antimicrobial resistance in food, humans, and other animals. In this sense, the present study evaluated the antimicrobial susceptibility profile and the presence of genes associated with resistance to erythromycin (msrC and ermB) and tetracycline [tet(M) and/or tet(L)] in enterococci isolated from raw sheep’s milk and cheeses (colonial, feta-, and pecorino-type) from South region of Brazil. A total of 156 enterococci were isolated from milk (n=80) and cheese (n=76) samples, identified by MALDI-TOF. Enterococcus faecalis (50.6%; n=79) was the most frequent species isolated from both samples. According to in vitro susceptibility tests, enterococci strains were not susceptible to the most commonly antimicrobial agents used in human and veterinary medicine. The frequency of MDR strains in enterococci isolated from milk (53.7%) was higher than those from cheese (24.2%). The tet(M) gene was the most commonly detected among tetracycline not-susceptible strains. The present study provided the first evidence of antimicrobial not-susceptible enterococci in raw sheep’s milk and cheeses in South Brazil. Drug-resistant strains, particularly those that are MDR, constitute a One Health issue.

Impact the Antibiotic Resistance for Staphylococcus aureus in Hospitalized Cancer Patients in Erbil Governate, Iraq

Background: Infection is a continuous problem in cancer patient especially in developing countries. Multidrug-resistant Staphylococcus aureus is among the most frequent complication in immunocompromised cancer patients and poses the greatest risk to immunocompromised cancer patients.
 Objectives: Our study aimed to carry out a study on isolated Staphylococcus aureus from various clinical samples among cancer patients in Erbil city and analyze its epidemiology and antibiotics susceptibility pattern tests and multi-drug resistance.
 Materials and Methods: A total of 865 from 2016 until 2020 were isolated Staphylococcus aureus from 6 clinical samples (Urine, Sputum, Wound swab, Nasal swab, Bloodand, Stool) from patient attending Nanakaly Hospital and from both males and females. Only 100 cases had been identified as isolates of S. aureus which was identified by using macroscopical, microscopical, biochemical tests and Vitek 2 compact system. Also antibiotic susceptibility test were performed by Vitek 2 compact on 19 antibiotics.
 Results: Only 100 S. aureus isolates were isolated from 865 samples distributed according to their source of isolation in the cancer patient, urinary tract infection is the most our specimen followed by wound infection, respiratory tract infection, blood infection and gastrointestinal infection. Breast cancer is the most common in our study followed by Colon cancer and Multiple myeloma, with the percentage of females infected with S. aureus more than the males, with females being 74/865(8.5%) and males being 28/865(3.2%), after 2016 infections by S. aureus was increased in young and middle-aged people being 52/100(52%) in total, from 2016-2020 S. aureus infected patients with breast cancer was 47/100(47%), colon was 27/100(27%) and multiple myeloma was 26/100(26%). Although (Aztreoman, Ertapenem, Ticarcillin-clavulanic acid) can be considered effective for MDR strains for empirical antibiotic therapy in cancer patients. S. aureus isolates had resistance to more than six antibiotics.
 Conclusions: The study findings showed a significant distribution of MDR S. aureus which may increase the burden of healthcare-associated infections in cancer patients. Moreover, mechanisms of resistance should also be investigated for better characterization of the multi-drug resistance of S. aureus isolates.

Determination of the antagonistic efficacy of silver nanoparticles against two major strains of Mycobacterium tuberculosis

Tuberculosis (TB) is considered one of the most prominent diseases across the globe. This present study aims to inspect the impact of silver nanoparticles (AgNP) against Mycobacterium tuberculosis, which is the causative vector of TB. The efficacy of the AgNP was conducted based on the minimum inhibitory concentration (MIC) of the AgNPs through microplate Alamar blue assay. The preparation of the AgNPs involved chemical synthesis. The state and the size of the AgNPs were determined and confirmed by using ultraviolet-visible (UV-Vis) absorption spectroscopy, X-ray diffraction (XRD) spectroscopy, and Transmission electron microscopy (TEM). This study evaluated two strains: Mycobacterium tuberculosis H37Rv and Mycobacterium bovis. In addition, another multiple drug-resistant Mycobacterium tuberculosis strain was also considered in this study, along with the clinically obtained isolates from Mycobacterium tuberculosis H37Rv and Mycobacterium tuberculosis bovis. The synthesized nanoparticles were found to be tetrahedral in shape with an average particle size of 45±3 nanometre (nm). The obtained results indicated that the proliferation of all the strains (two reference strains and one MDR strain) was resisted by the action of the synthesized AgNPs. The MIC of the MDR strain was noted within the range of 2-12 µg/ml, whereas the MIC for the Mycobacterium tuberculosis H37Rv and Mycobacterium bovis was noted in the range of 2-14 and 3-30 µg/ml, respectively. Accordingly, this study proposed a novel approach to combat tuberculosis, which is considered a global threat to humankind, indicating the present study's novelty.

Prevalence and Antibiogram Profile of Carbapenem-resistant Escherichia coli and Klebsiella pneumoniae among Patients with Urinary Tract Infection in Abakaliki, Nigeria

Background and Objectives: Carbapenem antibiotic are drug of last-resort from the treatment of bacterial infection, as a result of the prevalence and rapidly evolving enzymes from Carbapenem resistant bacteria such Escherichia coli and Klebsiella pneumoniae make urinary tract infection difficult, and in some cases impossible to treat in health care settings. With limited progress of new antibacterial drugs, the best approach is monitoring the prevalence and antibiogram profile of carbapenem-resistant Escherichia coli and Klebsiella pneumoniae among patients with UTI in Abakaliki, Nigeria.
 Methodology: A non-repetitive, clean catch mid-stream urine was collected from five hundred (500) diagnosed UTI inpatient and outpatient. The samples were evaluated using routine microbiological protocol for isolation and identification of Escherichia coli and Klebsiella pneumoniae. Phenotypic screening of Carbapenem-resistant strains was performed using Modified Hodge Testing. Antibiogram studies of carbapenem-resistant Escherichia coli and Klebsiella pneumoniae was performed using the Kirby–Bauer disk diffusion method and the results were interpreted using the Clinical Laboratory Standard Institute (CLSI) zone diameter breakpoints. Multiple antibiotic resistance index (MARI) was determined for MDR strain.
 Result: The prevalence of Escherichia coli and Klebsiella pneumoniae isolate accounted for 148(29.6 %) consisting of 95(54.3 %) and 53(16.3 %) from in-patients and out-patients. Escherichia coli accounted overall isolation rate of 112(22.4 %) comprising of high proportion among in-patient 82(46.9 %) over out-patient 30(9.2 %). The proportion of K. pneumoniae accounted for 36(7.2 %) with 13(7.4 %) and 23(7.1 %) recorded among in-patients and out-patients. Association between presence of Escherichia coli and Klebsiella pneumoniae isolates in clinical samples was statistically significant with patient’s population with p value <0.05. Carbapenem-resistant Escherichia coli and Klebsiella pneumoniae accounted for 37(7.4 %) comprising of 24(13.7) and 13(4.0 %) among in-patients and out-patients respectively while carbapenem-susceptible Escherichia coli and Klebsiella pneumoniae accounted for overall detection rate of 111(22.2 %) consisting of 71(40.6 %) and 40(12.3 %) among in-patients and out-patients respectively. The isolates resistance rate to cephalosporins were relatively high i.e., Cefotaxime, Cefoxtin Ceftazidime, Ceftriaxone resistance was observed at 60-100% while amoxicillin/clavulanate, azetronam, tetracycline nitrofurantoin and Ticarcillin-clavulanic acid recorded 100 % with MDR index ranged from 0.5-0.8, but were 100 % and 85.0 % sensitive to ciprofloxacin and ofloxacin.
 Conclusion: These results strongly hypothesize that MDR bacteria, including Carbapenem-resistant isolate, have become common residents in various hospital environments, however with substantial evidence in this study, ciprofloxacin and ofloxacin as drugs of choice could be used for treatment of UTI. Therefore, its importance that good antibiogram evaluation of other drug classes beside fluoroquinoles reported in this study need to be establishes as baseline for empirical diagnosis, epidemiological surveillance, drug prescriptions and infection management.

Modification of Antibiotic Activity by Fixed Oil of the Artocarpus heterophyllus Almond against Standard and Multidrug-Resistant Bacteria Strains.

Artocarpus heterophyllus (jackfruit) is an evergreen tree distributed in tropical regions and is among the most studied species of the genus Artocarpus. The jackfruit almond has been highlighted in relation to phytochemical studies, biological properties, and application in the development of food products. This study aimed to analyze jackfruit fixed oil regarding chemical components, antibacterial property alone, and in association with antibiotics against standard and MDR bacteria strains. In the analysis of the oil by gas chromatography coupled to a flame ionization detector (GC-FID), a high content of saturated fatty acids (78.51%) was identified in relation to unsaturated fatty acids (17.07%). The main fatty acids identified were lauric acid (43.01%), myristic acid (11.10%), palmitic acid (6.95%), and oleic acid (15.32%). In the antibacterial analysis, broth microdilution assays were used. The oil presented minimum inhibitory concentration (MIC) ≥ 1024 μg/mL in antibacterial analysis for standard and MDR bacterial strains. The oil showed synergistic effects in the association with gentamicin, ofloxacin, and penicillin against MDR strains, with significant reductions in the MIC of antibiotics. The results suggest that the fixed oil of A. heterophyllus has fatty acids with the potential to synergistically modify antibiotic activity.

148. Imipenem-Relebactam activity and genotypic characteristics of Carbapenem-resistant Enterobacterales and Pseudomonas aeruginosa Isolates from Latin American Infections - Study for Monitoring Antimicrobial Resistance Trends (SMART) 2017 – 2020

Abstract Background Imipenem/relebactam (IMI/REL) is a combination of Imipenem with Relebactam, an inhibitor of class A and C β-lactamases and has been approved in the US and EU, but not in Latin America. This report evaluates the in vitro activity of IMI/REL and comparators against Latin America (LATAM) Enterobacterales and P. aeruginosa (PSA) and the frequency of carbapenemase encoding genes (CEG) among gram-negative bacilli (GNB) isolated through the SMART Program (2017-2020). Methods 21606 nonconsecutive GNB isolates were collected in 10 LATAM countries. MICs for amikacin (AK), ceftazidime-avibactam (C-A), ceftolozane/tazobactam (C/T) and IMI/REL were determined by broth microdilution and interpreted by CLSI; a subset of Enterobacterales and P. aeruginosa carbapenem resistant was selected for characterization of carbapenemase encoding genes by PCR followed by DNA sequencing. Results Escherichia coli (N=9872; EC) tested susceptible to > 96% of all antibiotics analyzed; for P. aeruginosa (N=4528), C/T and C-A had the best susceptibility rates (85.7 and 86.6% respectively); for Enterobacter cloacae (N=1091; ECL) and Klebsiella pneumoniae (N=6115; KPN), we note that only IMI/REL and C-A were ≥ 95%. Profile of 2845 carbapenem resistant isolates was analysed and the main isolated agent in most countries was KPN, corresponding to 55% (1470), except in Mexico, Panama and Venezuela where PSA was the main carbapenemase producer. The blakpc-2, 3 were found in KPN 76.7, 79.2, 53.3, 52.1 and 85.3% in Argentina, Brazil, Colombia, Ecuador and Puerto Rico, respectively; Guatemala, Mexico, Venezuela presented blaNDM-1 in 74.3, 44.1 and 51.4%. Among ECL blakpc-2 (35.7%-Brazil, 48.2%-Colombia) and blaNDM-1(45.7%-Mexico) were most frequent, blaVIM-24 (16.6%) and blaIMP-18 (38.8%) were observed in Venezuela and Puerto Rico and in the latter, we observed first time reported blakpc-45 in 27.7 %. PSA expressed blakpc-2 (33.33%- Colombia), Chile and Venezuela blaVIM-2 (44.3%, 58.8%); blaspm-1 occurred only in Brazil (6.9%). Most common carbapenemase-producing bacteria in LATAM (n=2845) Antimicrobial susceptibility of Enterobacterales and P. aeruginosa (full data analysis=21606) Most Frequent CEG detected among carbapenemase producing isolates in Latin American countries (Genotypical sample analyzed n=2845) Conclusion The frequency of CEG is a threat in LATAM, mostly in Enterobacterales, whereas PSA as expected, has a lower frequency, but still a concern. In LATAM, IMI/REL has shown relevant activity against CEG producers, showing it is an option for treatment infections caused by MDR strains. Disclosures Gustavo Mizuno, PharmD, MSD Brazil: Employee Thales Polis, MD, MSD Brazil: Employee Jacqueline Ferrari, MD, MSD Brazil: Employee Jacqueline Pavia, MD, MSD COLOMBIA: EMPLOYEE Elisa Beirão, MD, MSD BRAZIL: Grant/Research Support Ana C. Gales, MD, MSD BRAZIL: Grant/Research Support Felipe Tuon, MD, MSD BRAZIL: Grant/Research Support Alexandre Alcantara, PharmD, MSD BRAZIL: EMPLOYEE Paula M. Batista, PharmD, MSD BRAZIL: EMPLOYEE.

1681. Activity of the Novel Engineered Antimicrobial Peptide PLG0206 Against Staphylococci and Enterococci

Abstract Background PLG0206 is an investigational, engineered cationic antimicrobial peptide designed to overcome the shortcomings of other natural AMPs, such as toxicity and limited activity. PLG0206 has recently been shown to be well tolerated and safe when administered i.v. in a Phase 1 study. The initial proposed indication for this peptide is the treatment of periprosthetic joint infections via irrigation due to a broad spectrum of activity and anti-biofilm properties. This study evaluated the activity of PLG0206 and comparator antimicrobials against staphylococci and enterococci, causes of periprosthetic joint infections, from the IHMA repository of isolates collected from various world-wide locations in 2019. Methods Isolates tested included Enterococcus faecalis (77), E. faecium (75), methicillin-resistant Staphylococcus aureus (MRSA, 180), methicillin-susceptible S. aureus (MSSA, 121) and 152 coagulase-negative staphylococci (CoNS) comprised of S. epidermidis (113), S. haemolyticus (31), S. hominis (4), S. lugdunensis (1), S. saprophyticus (2) and S. simulans (1). Minimum inhibitory concentrations (MICs) were determined by CLSI broth microdilution in cation-adjusted Mueller Hinton broth (CA-MHB), except for PLG0206 which was tested in RPMI medium due to plate-reading difficulties with CA-MHB. The susceptibility of comparators was determined using the 2022 CLSI breakpoints. MDR was defined as resistance to ≥ 3 antibacterial classes. Results When tested in RPMI, 18 E. faecalis, 29 E. faecium, 9 S. aureus and 7 CoNS were unable to grow. Summary MIC and susceptibility data for PLG0206 and comparators just including those isolates able to grow in RPMI are shown in the Table. Identical MIC50 and MIC90 values were obtained for PLG0206 when tested against MDR E. faecium (38), MDR CoNS (63) and MDR MRSA (67). Insufficient numbers of MDR MSSA (7) and MDR E. faecalis (4) were tested to accurately evaluate. Conclusion PLG0206 was the most potent antimicrobial overall (based on MIC50 and MIC90) against enterococci and CoNS and compared well with the comparators against MRSA and MSSA. These data support the evaluation of this novel antimicrobial peptide as a treatment option for periprosthetic joint infections, including those caused by MDR strains. Disclosures David Huang, MD, PhD, Peptilogics: Employee Jonathan Steckbeck, PhD, Peptilogics: I am CEO of Peptilogics.

1693. Meropenem-Xeruborbactam: In Vitro Potency against Gram-Negative Bacteria in Comparison with Marketed and Investigational Beta-lactam (BL)/Beta-lactamase Inhibitor (BLI) Combinations

Abstract Background Several BLI combinations have entered into clinical testing or been approved for use but there are few comparative studies of their in vitro activity. Xeruborbactam (XER, formerly QPX7728) is a cyclic boronate BLI with potent inhibitory activity against serine and metallo-beta-lactamases (MBL). It is in clinical development in combination with meropenem (MEM). The objective of this study was to compare in vitro potency of MEM-XER to that of other investigational and approved BL/BLI combinations in head-to-head testing against recent isolates of carbapenem-resistant Enterobacterales (CRE) and Acinetobacter baumannii (CRAB) as well as Pseudomonas aeruginosa (PA). Methods The test panel of recent worldwide isolates consisted of 507 CRE including 168 MBL producers (157 NDM, 11 VIM, 1 IMP), 506 CRAB, and 506 PA that were representative of current isolates and included 65 MDR (resistant to ≥ 3 antimicrobial classes) strains. MEM-XER was tested with XER at a fixed 8 mg/L conc. and other BL/BLI combinations at their recommended BLI concentrations. MIC testing was conducted blinded to drug identity using CLSI reference methods and controlled using approved quality control bacterial strains and ranges. Results The MIC50 and MIC90 for MEM-XER vs CRE ranged from ≤ 0.03 mg/L to 0.06 mg/L and 0.06 mg/L to 1 mg/L, respectively. MEM-XER and cefepime-taniborbactam (FEP-TANI) were the only BL/BLIs with activity against MBL-producers; based on MIC90, MEM-XER (MIC90 of 1 mg/L) was 16-fold more potent than FEP-TANI (MIC90 of 16 mg/L). MEM-XER and sulbactam-durlobactam (SUL-DUR) were the only agents with high potency against CRAB, with MIC50/MIC90 of 0.5/4 mg/L and 1/2 mg/L. For the representative panel of PA, the potency of MEM-XER, FEP-TAN, ceftolozane-tazobactam (TOL-TAZ), imipenem-relebactam (IMP-REL), and CAZ-AVI was similar with MIC90s ranging between 2-8 mg/L; for the MDR panel, MIC90‘s were > 8 mg/L for all combinations, with MER-XER, IMP-REL, TOL-TAZ, and CAZ-AVI having MIC50’s of 2-4 mg/L. Conclusion Compared to the marketed or investigational BL/BLIs, MEM-XERU had the broadest coverage of carbapenem-resistant gram-negative bacteria, with the most differentiating property being activity against multiple strains of MBL-producing CRE and CRAB. Disclosures Mariana Castanheira, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support Jill Lindley, BS, AbbVie: Grant/Research Support.

1680. Activity of the Novel Engineered Antimicrobial Peptide PLG0206 Against Enterobacterales isolates

Abstract Background PLG0206 is an investigational, engineered cationic antimicrobial peptide designed to overcome the shortcomings of other natural AMPs, such as toxicity and limited activity. PLG0206 has recently been shown to be well tolerated and safe in a phase 1 study. This study evaluated the activity of PLG0206 and comparator antimicrobials against Enterobacterales isolates from the IHMA repository collected from various world-wide locations in 2019. Methods Isolates tested included Citrobacter spp. (151), Enterobacter cloacae (152), Escherichia coli (300), Klebsiella pneumoniae (300), Morganella morganii (43), Proteus spp. (152), Providencia spp. (61) and Serratia marcescens (45). Minimum inhibitory concentrations (MICs) were determined by CLSI broth microdilution in cation-adjusted Mueller Hinton broth (CA-MHB), except for PLG0206 which was tested in RPMI medium due to plate-reading difficulties with CA-MHB. The susceptibility of comparators was determined using the 2022 CLSI breakpoints. MDR was defined as resistance to ≥ 3 antibacterial classes. Results Summary MIC and susceptibility data against Citrobacter spp., E. coli, E. cloacae, and K. pneumoniae are shown in the Table. PLG0206 retained activity against MDR isolates of Citrobacter spp. (26), E. coli (92), E. cloacae (45), and K. pneumoniae (132) with MIC50/90 values of 1/2, 1/2, 1/16 and 8/16 μg/mL, respectively. PLG0206 was essentially inactive against the Morganellaceae and Yersiniaceae isolates tested with MIC50 and MIC90 values of > 32 μg/mL (data not shown). Conclusion PLG0206 was active against isolates from the family Enterobacteriaceae, including MDR strains. The spectrum of activity of PLG0206 ranged from being most active against Citrobacter spp. and least active against K. pneumoniae. These data suggest that the novel antimicrobial peptide PLG0206 could be a potential treatment option against infections caused by Enterobacteriaceae isolates. Disclosures David Huang, MD, PhD, Peptilogics: Employee Jonathan Steckbeck, PhD, Peptilogics: I am CEO of Peptilogics.

Development of Novel Isatin-Tethered Quinolines as Anti-Tubercular Agents against Multi and Extensively Drug-Resistant Mycobacterium tuberculosis.

We describe the design and synthesis of two isatin-tethered quinolines series (Q6a-h and Q8a-h), in connection with our research interest in developing novel isatin-bearing anti-tubercular candidates. In a previous study, a series of small molecules bearing a quinoline-3-carbohydrazone moiety was developed as anti-tubercular agents, and compound IV disclosed the highest potency with MIC value equal to 6.24 µg/mL. In the current work, we adopted the bioisosteric replacement approach to replace the 3,4,5-trimethoxy-benzylidene moiety in the lead compound IV with the isatin motif, a privileged scaffold in the TB drug discovery, to furnish the first series of target molecules Q6a-h. Thereafter, the isatin motif was N-substituted with either a methyl or benzyl group to furnish the second series Q8a-h. All of the designed quinoilne-isatin conjugates Q6a-h and Q8a-h were synthesized and then biologically assessed for anti-tubercular actions towards drug-susceptible, MDR, and XDR strains. Superiorly, the N-benzyl-bearing compound Q8b possessed the best activities against the examined M. tuberculosis strains with MICs equal 0.06, 0.24, and 1.95 µg/mL, respectively.

In Vitro Antimycobacterial Activity of Human Lactoferrin-Derived Peptide, D-hLF 1-11, against Susceptible and Drug-Resistant Mycobacterium tuberculosis and Its Synergistic Effect with Rifampicin.

Tuberculosis is a highly contagious disease caused by the Mycobacterium tuberculosis complex (MTBC). Although TB is treatable, multidrug-resistant, extensively drug-resistant, and totally drug-resistant forms of M. tuberculosis have become a new life-threatening concern. New anti-TB drugs that are capable of curing these drug-resistant strains are urgently needed. The purpose of this study is to determine the antimycobacterial activity of D-enantiomer human lactoferricin 1-11 (D-hLF 1-11) against mycobacteria in vitro using a 3-(4,5-dimethylthiazol-2-yl)-2,5-dephenyltetrazolium bromide colorimetric assay, resazurin microplate assay, and microscopic observation drug susceptibility assay. Three previously described antimicrobial peptides, protegrin-1, AK 15-6, and melittin, with potent anti-TB activity, were included in this study. The findings suggest that D-hLF 1-11 can inhibit the growth of M. tuberculosis with a minimum inhibitory concentration of 100-200 µg/mL in susceptible, isoniazid (INH)-monoresistant, rifampicin (RF)-monoresistant, and MDR strains. The peptide can also inhibit some nontuberculous mycobacteria and other MTBC in similar concentrations. The antibiofilm activity of D-hLF 1-11 against the biofilm-forming M. abscessus was determined by crystal violet staining, and no significant difference is observed between the treated and untreated biofilm control. The checkerboard assay was subsequently carried out with M. tuberculosis H37Rv and the results indicate that D-hLF 1-11 displays an additive effect when combined with INH and a synergistic effect when combined with RF, with fractional inhibitory concentration indices of 0.730 and 0.312, respectively. The red blood cell hemolytic assay was initially applied for the toxicity determination of D-hLF 1-11, and negligible hemolysis (<1%) was observed, despite a concentration of up to 4 mg/mL being evaluated. Overall, D-hLF 1-11 has potential as a novel antimycobacterial agent for the future treatment of drug-sensitive and drug-resistant M. tuberculosis infections.

Effectiveness Evaluation of a UV-C-Photoinactivator against Selected ESKAPE-E Pathogens.

Healthcare-associated infections (HAI) worldwide includes infections by ESKAPE-E pathogens. Environmental surfaces and fomites are important components in HAI transmission dynamics, and shoe soles are vectors of HAI. Ultraviolet (UV) disinfection is an effective method to inactivate pathogenic microorganisms. In this study, we investigated whether the SANITECH UV-C shoe sole decontaminator equipment that provides germicidal UV-C radiation could effectively reduce this risk of different pathogens. Six standard strains and four clinical MDR strains in liquid and solid medium were exposed to a UV-C System at specific concentrations at other times. Bacterial inactivation (growth and cultivability) was investigated using colony counts and resazurin as metabolic indicators. SEM was performed to assess the membrane damage. Statistically significant reduction in cell viability for all ATCCs strains occurred after 10 s of exposure to the UV-C system, except for S. enterica, which only occurred at 20 s. The cell viability of P. aeruginosa (90.9%), E. faecalis and A. baumannii (85.3%), S. enterica (82.9%), E. coli (79.2%) and S. aureus (71.9%) was reduced considerably at 20 s. In colony count, after 12 s of UV-C exposure, all ATCC strains showed a 100% reduction in CFU counts, except for A. baumannii, which reduced by 97.7%. A substantial reduction of colonies above 3 log10 was observed at 12 and 20 s in all bacterial strains tested, except for A. baumannii ATCC 19606 (12 s). The exposure of ATCCs bacterial strains to the UV-C system for only 2 s was able to reduce 100% in the colony forming units (CFU) count in all ATCCs strains, S. aureus, P. aeruginosa, E. coli, A. baumannii, E. faecalis, except the S. enterica strain which had a statistically significant reduction of 99.7%. In ATCC strains, there was a substantial decrease in colonies after 4 s (sec) of exposure to the UV-C system, with a reduction ranging from 3.78-4.15 log10 CFU/mL. This reduction was observed in MDR/ESKAPE-E strains within 10 s, showing that UV-C could eliminate above 3.84 log10 CFU/mL. SEM showed a reduction of pili-like appendages after UV-C treatment in all strains except for E. coli (ATCC 25922). The Sanitech UV-C shoe sole decontaminator equipment from Astech Serv. and Fabrication Ltd. (Petrópolis, Brazil), effectively killed in vitro a series of ATCCs and MDR/ESKAPE-E bacteria of sanitary interest, commonly found in the hospital environment.

Antibacterial effect, efflux pump inhibitory (NorA, TetK and MepA) of Staphylococcus aureus and in silico prediction of α, β and δ-damascone compounds

ObjectiveThe present study aimed to evaluate the antibacterial effect and inhibitory capacity against NorA, TetK and MepA efflux pump of Staphylococcus aureus multiresistant by in vitro and in silico approach of α, β and δ-damascone compounds. ResultsThe compounds α, β and δ-damascone showed a clinically relevant effect against S. aureus ATCC 6538 standard strain. A modulating effect was also observed in association with antibiotics against MDR strains. Regarding the inhibition of the efflux pump, the compounds showed a modulating effect with antibiotics, against SA-1199, SA-1199B, SA IS-58 and K2068. Only δ-damascone demonstrated an efflux pump inhibitory effect. Regarding ADME properties, α, β and δ-damascone showed similar physicochemical properties with good pharmacokinetic characteristics, such as lipophilicity, oral bioavailability and low toxicity. In addition, they exhibited the binding energy and Ligand Efficiency (LE) −81.17 (5.4), −77.48(-5.4) and −64.55 (-5.1), which shows good interactions with the critical residues of the MepA receptor. ConclusionsFrom the results it is concluded that the compounds α, β and δ-damascone do not have antibacterial activity, but show a modulating effect in association with antibiotics, as well as not showing direct activity on the efflux pump, but they do have a modulating effect with antibiotics and with EtBr (α and β-damascone).