Minimum Inhibitory Concentration Range Research Articles

First-line antibiotic susceptibility pattern of toxigenic Corynebacterium diphtheriae in Indonesia

BackgroundDiphtheria has been reported as an outbreak in some regions in Indonesia, most especially in East Java Province. Resistance to penicillin, erythromycin, and other antibiotics, single or multiple, has been reported in several studies. This study aims to evaluate the first-line antibiotic susceptibility pattern of toxigenic Corynebacterium diphtheriae isolates.MethodsThis descriptive observational study was performed from August to November 2018. C. diphtheriae isolates were collected from diphtheria patients and carriers in East Java from 2012 to 2017 and kept at the Balai Besar Laboratorium Kesehatan Daerah Surabaya or the Public Health Laboratory of Surabaya. Sample selection was done by random cluster sampling. The sensitivity test by E-test®of the five antibiotics (penicillin, oxacillin, erythromycin, azithromycin, and clarithromycin) was done to determine the minimum inhibitory concentration (MIC). The Clinical and Laboratory Standards Institute M45A (2015) Corynebacterium spp. for penicillin and erythromycin was used as standard.ResultsFrom 114 targeted isolates, 108 were viable and toxigenic. The E-test was performed on the viable isolates. The majority of the hosts were male (58.3%), with median (range) age of 6.5 (1–14) years. Half of the samples were from the 1 to 5-year-old age group. The isolates were acquired much more from patients (78.7%) than carriers (21.3%) and from pharyngeal swab (74.1%). Most of these isolates were from Madura Island (47.2%) and the northern and eastern parts of the province (horseshoe area). Mitis isolates were the major variant (76.9%). The susceptibility pattern of C. diphtheriae to erythromycin was better than that to penicillin. The E-test result for penicillin was 68.52% susceptible, 31.48% intermediate, and 0% resistant (MIC range, < 0.016 to 2 μg/L) and for erythromycin (MIC range, < 0.016 to > 256 μg/L) was 85.2% susceptible, 12% intermediate, and 2.8% resistant The MIC range for oxacillin was 1 to 96 μg/L, while for both azithromycin and clarithromycin were < 0.016 to > 256 μg/L.ConclusionThe susceptibility rate of C. diphtheriae to erythromycin is higher than that to penicillin. The regular update of antibiotic selection to the national guidelines is recommended. The MIC reference standard to azithromycin and clarithromycin is also needed.

In vitro Antibacterial Activity of Isopropoxy Benzene Guanidine Against Multidrug-Resistant Enterococci.

BackgroundBacterial infections cause a serious public health crisis due to the emergence of resistance towards multiple conventional antibacterial drugs. In particular, multidrug-resistant (MDR) Enterococcus faecium which belongs to “ESKAPE” organisms is causing significant problems worldwide. Hence, there is an urgent need to find alternative therapies. Recently, substituted benzene guanidine compounds have been used as lead structures to discover new promising drugs in both synthetic and medicinal chemistry.PurposeHere we investigated the antimicrobial activity of a new substituted benzene guanidine analog, isopropoxy benzene guanidine, against Enterococci.Material and methodsThe isopropoxy benzene guanidine was synthesized by Guangzhou Insighter Biotechnology Co., Ltd and tested on both reference bacterial strain and 32 clinical MDR Enterococci strains. The in vitro antibacterial activity was evaluated by microdilution method and kill kinetic assays. The potential antibacterial mechanism was measured by fluorescence spectrometry using fluorescent membrane potential probe 3, 3-diethyloxacarbocyanine iodide (DiOC2 (3)).ResultsIsopropoxy benzene guanidine exhibited potent bactericidal activity against both reference strain and MDR Enterococci isolates. The minimum inhibitory concentration (MIC) range for isopropoxy benzene guanidine was 1–4 μg/mL. Minimum bactericidal concentration (MBC) was about 2-8-fold of its MIC values. Time-kill studies showed that isopropoxy benzene guanidine provided superior bactericidal effect against reference and MDR strains within 12 hrs at 2×MIC. Furthermore, isopropoxy benzene guanidine could cause a large reduction in the magnitude of the generated membrane potential compared to that of the untreated cells.ConclusionThe present study highlights the potent bactericidal activity of isopropoxy benzene guanidine on Enterococci by disrupting the cell membrane potential. These findings demonstrate that isopropoxy benzene guanidine may be a good chemical lead for further medicinal chemistry and pharmaceutical development and could be used as a therapeutic agent for infectious diseases caused by MDR Enterococci.

Determination of Fusidic Acid Susceptibility of Multidrug-resistant Gonococcal Isolates from China

Abstract The currently recommended gonococcal therapies are rapidly losing efficacy and; therefore, novel options for treatment are urgently required to ensure future treatment remains available. Here we investigated the susceptibility of 379 contemporary clinical Neisseria gonorrhoeae isolates from China for susceptibility to fusidic acid. These isolates include numerous multidrug-resistant strains with resistance or reduced susceptibility against ceftriaxone and/or azithromycin, antimicrobials that are currently recommended as a first-line dual therapy. Although official susceptibility breakpoints have not been established, all gonococcal isolates appeared to be susceptible to fusidic acid, with the majority of isolates displaying a minimal inhibitory concentration (MIC) of 0.25 or 0.5 mg/L. Overall, the MIC90 was 0.5 mg/L, with a MIC range of 0.08–2 mg/L. Importantly, no correlation between fusidic acid susceptibility and susceptibility to ceftriaxone or azithromycin was observed. Further analysis of gonococcal survival curves indicated that fusidic acid was only mildly bactericidal at the highest tested concentrations (4× MIC). In conclusion, fusidic acid displayed consistent antimicrobial activity against N. gonorrhoeae and, given the absence of cross-resistance with ceftriaxone and azithromycin, might be interesting for further evaluation of single or dual antimicrobial therapies in combination with ceftriaxone or azithromycin.

Preliminary studies on the antifungal activities of ethanol and hot water extracts of local spices against fluconazole-resistant &lt;i&gt;Candida albicans&lt;/i&gt; isolates recovered from clinical samples

This study evaluated the antifungal effect of local spices namely Capsicum annum var. shombo, Capsicum annuum var. atarugu, Capsicum annuum var. Nsukka yellow pepper, Zingiber officinale and Allium sativum against fluconazole-resistant Candida albicans isolates. Hot water and ethanol were used as solvents for extraction. The seed and pericarp extracts from Capsicum annuum alone showed no inhibitory effect against the test organisms. Notwithstanding, whole Capsicum annuum fruit extracts showed variable levels of inhibition against the tested isolates. The minimum inhibitory concentration (MIC) results of hot water extract showed that Capsicum annuum var. atarugu had the lowest MIC of 6.25 mg/ml while Capsicum annuum var. yellow pepper showed the highest MIC of 100 mg/ml. Zingiber officinale showed MIC range of 3.125 mg/ml to 50 mg/ml and Allium sativum an MIC range of 12.5 mg/ml to 50 mg/ml for both hot water extract and ethanol extracts. The least MIC was obtained with Zingiber officinale ethanol extract with an MIC of 3.125 mg/ml. Our finding shows that these spices may be potential sources of antifungal agents. Keywords: Capsicum annum , Zingiber officinale , Allium sativum , Antifungal activity, Nsukka

Molecular mechanism of azithromycin resistance among typhoidal Salmonella strains in Bangladesh identified through passive pediatric surveillance.

BackgroundWith the rise in fluoroquinolone-resistant Salmonella Typhi and the recent emergence of ceftriaxone resistance, azithromycin is one of the last oral drugs available against typhoid for which resistance is uncommon. Its increasing use, specifically in light of the ongoing outbreak of extensively drug-resistant (XDR) Salmonella Typhi (resistant to chloramphenicol, ampicillin, cotrimoxazole, streptomycin, fluoroquinolones and third-generation cephalosporins) in Pakistan, places selective pressure for the emergence and spread of azithromycin-resistant isolates. However, little is known about azithromycin resistance in Salmonella, and no molecular data are available on its mechanism.Methods and findingsWe conducted typhoid surveillance in the two largest pediatric hospitals of Bangladesh from 2009–2016. All typhoidal Salmonella strains were screened for azithromycin resistance using disc diffusion and resistance was confirmed using E-tests. In total, we identified 1,082 Salmonella Typhi and Paratyphi A strains; among these, 13 strains (12 Typhi, 1 Paratyphi A) were azithromycin-resistant (MIC range: 32–64 μg/ml) with the first case observed in 2013. We sequenced the resistant strains, but no molecular basis of macrolide resistance was identified by the currently available antimicrobial resistance prediction tools. A whole genome SNP tree, made using RAxML, showed that the 12 Typhi resistant strains clustered together within the 4.3.1.1 sub-clade (H58 lineage 1). We found a non-synonymous single-point mutation exclusively in these 12 strains in the gene encoding AcrB, an efflux pump that removes small molecules from bacterial cells. The mutation changed the conserved amino acid arginine (R) at position 717 to a glutamine (Q). To test the role of R717Q present in azithromycin-resistant strains, we cloned acrB from azithromycin-resistant and sensitive strains, expressed them in E. coli, Typhi and Paratyphi A strains and tested their azithromycin susceptibility. Expression of AcrB-R717Q in E. coli and Typhi strains increased the minimum inhibitory concentration (MIC) for azithromycin by 11- and 3-fold respectively. The azithromycin-resistant Paratyphi A strain also contained a mutation at R717 (R717L), whose introduction in E. coli and Paratyphi A strains increased MIC by 7- and 3-fold respectively, confirming the role of R717 mutations in conferring azithromycin resistance.ConclusionsThis report confirms 12 azithromycin-resistant Salmonella Typhi strains and one Paratyphi A strain. The molecular basis of this resistance is one mutation in the AcrB protein at position 717. This is the first report demonstrating the impact of this non-synonymous mutation in conferring macrolide resistance in a clinical setting. With increasing azithromycin use, strains with R717 mutations may spread and be acquired by XDR strains. An azithromycin-resistant XDR strain would shift enteric fever treatment from outpatient departments, where patients are currently treated with oral azithromycin, to inpatient departments to be treated with injectable antibiotics like carbapenems, thereby further burdening already struggling health systems in endemic regions. Moreover, with the dearth of novel antimicrobials in the horizon, we risk losing our primary defense against widespread mortality from typhoid. In addition to rolling out the WHO prequalified typhoid conjugate vaccine in endemic areas to decrease the risk of pan-resistant Salmonella Typhi strains, it is also imperative to implement antimicrobial stewardship and water sanitation and hygiene intervention to decrease the overall burden of enteric fever.

739. Prediction of Cefiderocol Pharmacokinetics and Probability of Target Attainment in Pediatric Subjects for Proposing Dose Regimens

BackgroundCefiderocol is a siderophore cephalosporin discovered by Shionogi & Co., Ltd., which exhibits potent efficacy against Gram-negative carbapenem-resistant bacteria. Pediatric clinical studies are planned. Cefiderocol is mainly renally eliminated. A 2-g infusion of cefiderocol over 3 hours, every 8 hours (q8h) is the recommended dose regimen in adults. In this study, dose regimens for pediatric subjects (birth to <18 years old) are proposed based on predictions of pharmacokinetics (PK) in pediatrics using data from adults to provide adequate exposure.MethodsThe PK model developed based on data in adults was modified for predicting PK in pediatrics. Total clearance and volume of distribution at steady state in pediatrics were scaled using allometric relationships developed for parenteral β-lactam antibiotics. The maturation factor of renal function was also incorporated into the model to predict PK in neonates and infants whose glomeruli are immature. The dose was selected to provide area under the concentration curve (AUC) comparable to adults. Monte-Carlo simulations were performed to calculate probability of target attainment (PTA) for 75% of fraction of time during which the free plasma concentrations exceed the minimum inhibitory concentration (MIC) over the dosing interval (fT>MIC) for age groups at the proposed doses against an MIC range from 0.25 to 16 µg/mL.ResultsThe dose regimens for pediatrics were proposed based on age and body weight as shown in the table below. The dose of 60 mg/kg (maximum 2 g) q8h was selected as a standard dose. The dose for pediatrics aged <3 months was adjusted based on age. AUC predicted in pediatrics from birth to <18 years old for the proposed dose was comparable to that observed in adults. The proposed dose provided >90% PTA for 75% fT>MIC against MICs up to 4 µg/mL.ConclusionThe proposed dose regimens provide comparable (to adults) exposure in pediatric patients for target carbapenem-nonsusceptible pathogens, 98% of which are susceptible to cefiderocol at a MIC of ≤4 µg/mL. Disclosures All authors: No reported disclosures.

644. Comparative Evaluation of ETEST® ERV bioMérieux with the CLSI Broth Microdilution Method for Eravacycline MIC Determination

BackgroundEravacycline (XERAVA™) is a novel, FDA and EMA-approved fully-synthetic fluorocycline antibiotic developed by Tetraphase Pharmaceuticals Inc. for the treatment of complicated intra-abdominal infections (cIAI) including those caused by multidrug-resistant (MDR) pathogens that have been highlighted as urgent public health threats by the US CDC and the WHO.The new ETEST ERV strip (MIC range 0.002 – 32 µg/mL) has been developed by bioMérieux and calibrated vs. the broth microdilution reference method (BMD) as described by the Clinical and Laboratory Standards Institute (CLSI) to determine the minimal inhibitory concentration (MIC) of eravacycline against Enterobacterales and Enterococci. The aim of the study was to compare ETEST ERV to the CLSI BMD method on a panel of 166 strains comprising 131 Enterobacterales and 35 Enterococci.MethodsQuality control was performed with the CLSI QC strains E.coli ATCC 25922 and E.faecalis ATCC 29212. The ETEST ERV strip was applied on a Mueller–Hinton agar plate previously seeded with a 0.5 McF bacterial suspension. After incubation for 16–20H at 35°C, the reading was performed using the bacteriostatic mode i.e.,80% of growth. The FDA-approved breakpoints were applied (S≤0.5µg/mL for Enterobacterales and S ≤0.064 µg/mL for Enterococci).ResultsThe MIC essential agreement was 99.4% at ±1 dilution for the whole panel and the category agreement was 96.4% with 4.8% Major Errors (1 E. coli, 2 K. pneumoniae, 1 K.aerogenes, 1 C. koseri, 1 E. faecalis), all at ±1 dilution around the single breakpoint. No Very Major Error (VME) was observed.ConclusionIn this study, the new ETEST ERV strip has been found to be substantially equivalent to the CLI reference method. MIC end-points appear easier to read in comparison to the reference method. With a 15-dilution MIC range and simplicity of use, ETEST ERV could represent a valuable tool for MIC determination and an alternative to the BMD reference method. ETEST ERV will undergo clinical studies to seek IVD FDA clearance and CE marking. For Research Use Only. The performance characteristics of this product have not yet been established.Disclosures All authors: No reported disclosures.

710. In Vitro Activity and Performance of Available Susceptibility Testing Methods for Eravacycline Against Carbapenem-Resistant Enterobacteriaceae (CRE)

BackgroundEravacycline (ERV) is a recently-approved, fully synthetic fluorocycline agent that demonstrates broad in vitro activity against multidrug-resistant pathogens. We sought to compare the activity of ERV with minocycline (MIN) and tigecycline (TGC) against diverse CRE clinical isolates, and to evaluate the performance of commercially-available susceptibility testing methods.MethodsERV, MIN, and TGC minimum inhibitory concentrations (MICs) were determined in triplicate by broth microdilution against previously characterized CRE isolates. ERV susceptibility was also measured by disk diffusion (20 µg disk; Mast Group) and MIC test strips (MTS; Liofilchem) according to manufacturer instructions.Results148 CRE were tested, including 92 K. pneumoniae, 32 Enterobacter spp, 11 E. coli, 5 C. freundii, 4 K. oxytoca, and 4 S. marcescens. 72% of isolates harbored blaKPC, which encoded KPC-2 (n = 33), KPC-3 (n = 48), and other KPC variants (n = 22). 77% and 19% of isolates were resistant to meropenem and ceftazidime–avibactam, respectively. By BMD, the ERV, MIN, and TGC MIC range, MIC50 and MIC90 for shown in the Table. ERV MICs were ≥2-fold lower than MIN and TGC against 99% and 43% of isolates, respectively. ERV MICs did not vary by species or KPC-subtype. ERV MICs determined by BMD and MTS were well-correlated showing 89% essential agreement (MIC within one 2-fold dilution; Figure). The rate of categorical agreement (CA) was 73%. By comparison, the CA rate between BMD and disk diffusion was 78%. By both MTS and disk diffusion methods, susceptibility results clustered on either side of the susceptibility breakpoint. 50% of disk diffusion zones clustered between 14 and 16 millimeters (mm), which is 1 mm on either side of the susceptibility breakpoint (≥15 mm).ConclusionThis study confirms the in vitro activity of ERV against CRE clinical isolates, which is comparable to TGC. ERV MTS demonstrated high rates of EA, but lower rates of CA. Clinicians should be aware of the nuances of ERV susceptibility testing and recognize that the modal distribution of ERV MICs against CRE lies on either side of the susceptibility breakpoint. Disclosures All authors: No reported disclosures.

522. In Vitro Antimicrobial Activity of Ceftazidime/Avibactam Compared with Ceftolozane/Tazobactam Against Real-world Clinical Isolates of Pseudomonas aeruginosa at a Large Academic Tertiary Care Hospital

BackgroundCeftazidime/avibactam (CZA) and ceftolozane-tazobactam (CT) are new additions to the antibiotic armamentarium with activity against gram-negative pathogens, most notably drug-resistant Pseudomonas aeruginosa (PSA). The purpose of this study was to compare the in vitro activity of CZA and CT against a large real-world sample of clinical isolates of PSA displaying different phenotypes of resistance to conventional β-lactams at an institution where both CZA and CT are routinely tested on all isolates.MethodsAll cultures from patient infections with PSA from May 2018 to February 2019 at Michigan Medicine were included. Minimum inhibitory concentrations (MICs) for all β-lactams were determined using TREK broth microdilution panels and isolates were considered susceptible to CZA if the MIC was ≤8 mg/L and CT if the MIC was ≤4 mg/L.ResultsA total of 2,972 isolates of PSA from clinical specimens were included. Table 1 compares CZA and CT susceptibility, MIC50, MIC90, and MIC range for all isolates including those displaying resistance to various β-lactams. Among all isolates of PSA, CZA (96.2% susceptible) was slightly more active than CT (94.2%) and both agents were ~10% more active than the closest comparator (ceftazidime, 86.6%). In vitro activity of cefepime, piperacillin/tazobactam, and meropenem were 84.8%, 78%, and 80.3%, respectively. The activity of both CZA and CT dropped significantly among isolates with pan-β-lactam resistance (i.e., resistance to all conventional anti-pseudomonal β lactams, PBR) but CZA remained more active than CT (59.4% vs. 41.5%, P < 0.001). Of isolates displaying resistance to CT, 84 (48.6%) were susceptible to CZA. However, of those with resistance to CZA, only 24 (21.2%) were susceptible to CT (Table 2).ConclusionCZA was the most active β-lactam against PSA isolates at Michigan Medicine. Among PSA with PBR, CZA demonstrated superior activity compared with CT. Additionally, a significant number of isolates with resistance to CT were susceptible to CZA. Our findings are unique compared with other published reports where CT has consistently demonstrated greater activity than CZA against resistant P. aeruginosa and suggest routine testing of both CT and CZA should occur. Disclosures All authors: No reported disclosures.

564. A Five-Year Evolutionary Study of the Minimum Inhibitory Concentrations of Methicillin-resistant Staphylococcus aureus to Mupirocin, Chlorhexidine, and Octenidine in a Singaporean Tertiary Institution

BackgroundMethicillin-resistant Staphylococcus aureus (MRSA) is a common cause of healthcare-associated infection. Eradication of MRSA carriage reduces clinical infection and prevents transmission. In Singapore General Hospital, a series of hospital-wide measures were instituted over three years (Figure 1) to reduce mupirocin (MUP) resistance, and to decrease the bioburden of MRSA colonization amongst inpatients using octenidine (OCT)-based products.MethodsA prevalence study was conducted at three time points (TPs) on consecutive MRSA screening isolates to evaluate for their minimum inhibitory concentrations (MICs) to CHG, OCT and MUP using broth microdilution sensitive plates and the presence of the ileS-2 gene, in 2013 (pre-intervention TP, TP1; n = 160), 2016 (early post-intervention TP, TP2; n = 99) and 2017 (late post-intervention TP, TP3; n = 76). Statistical analyses were performed using the Chi-square test with reference from TP1.ResultsA significant improvement in MUP susceptibility by MIC (256 µg/mL) and ileS-2 testing reduced from 25.0% (TP1) to 12.1% (TP2; P = 0.014) to 5.3% (TP3; P = 0.001) and 30.0% (TP1) to 18.2% (TP2; P = 0.036) to 9.2% (TP3; P = 0.001), respectively. OCT MIC range remained stable at 0.5 to 1 across all three TPs. The number of isolates with reduced CHG susceptibility (MIC ≥4 mg/L) increased over the three TPs from 23.1% to 27.2% (P = 0.45) to 42.1% (P = 0.003), despite decreasing CHG prescription.ConclusionA restrictive MUP usage policy can improve MUP susceptibility amongst MRSA isolates over time. Widespread OCT use did not appear to result in a rise of OCT MIC over the intervention period. Although the clinical significance of reduced susceptibility to CHG remains uncertain, this worrying trend in our institution deserves further studies to better understand mechanisms of CHG resistance. Disclosures All authors: No reported disclosures.

Eucalyptus citriodora leaf extract-mediated biosynthesis of silver nanoparticles: broad antimicrobial spectrum and mechanisms of action against hospital-acquired pathogens.

Pathogen resistance to conventional antibiotics has become a serious clinical and public health problem, making the development of an alternative mean a very urgent issue. Recently, biosynthesis of silver nanoparticles (AgNPs) was successfully accomplished in the presence of Eucalyptus citriodora leaf extract as a reducing agent. In this study, the antimicrobial mechanisms of AgNPs against important hospital-acquired pathogens, including Gram-positive, Gram-negative bacteria, and fungi were further assessed. The results indicated that AgNPs could enhance a broad antimicrobial spectrum against drug-resistant organisms, with a range of minimum inhibitory concentration from 0.02 to 0.36μg/mL. Time-kill assay showed that AgNPs produced bactericidal effects on the microorganisms. AgNPs could significantly reduce biofilm production in pathogens without affecting growth of the pathogens (p<0.05). AgNPs inhibited cell viability and biofilm formation in a dose-dependent manner. Cell membrane damage in microorganisms resulting from effects of AgNPs was observed. A significant increase in per cent uptake of crystal violet was observed in all isolates treated with AgNPs when compared with the control (p<0.05). Upon treatment with AgNPs, the surface charge of the reference strains and clinical isolates of pathogens moved towards neutral. The alteration of surface potential after exposure to AgNPs could contribute to membrane disruption and cell viability. Scanning electron microscopy further confirmed morphological cell changes and disrupted the cell membrane. Increasing resistance to AgNPs was not induced by stepwise isolation of the bacteria after 45 passages on Luria-Bertani agar supplemented with AgNPs. Furthermore, AgNPs was not toxic to red blood cells.

Extracellular biosynthesis of cobalt ferrite nanoparticles by Monascus purpureus and their antioxidant, anticancer and antimicrobial activities: Yield enhancement by gamma irradiation.

Cobalt ferrite nanoparticles were successfully synthesized using the fungus Monascus purpureus ATCC16436 as a potentially low-cost, eco-friendly and easy to produce method. Fourier transform infrared spectroscopy confirmed the functional groups present in the prepared samples. X-ray diffraction pattern of the synthesized nanoparticles revealed a single-phase crystalline structure. Transmission electron microscope studies showed the spherical shape with a mean particle size of 6.50 nm. Vibrating sample magnetometer analyses revealed that the synthesized nanoparticles have a superparamagnetic behavior. In addition, the antioxidant, anticancer and antimicrobial activities of the synthesized nanoparticles were evaluated. The synthesized nanoparticles exhibited antioxidant potential as compared by ascorbic acid with 50% inhibitory concentration of 100.25 μg mL-1. Based on the MTT assay, the synthesized nanoparticles significantly inhibited the proliferation of two different human cancer cell lines (breast and liver) and normal human melanocytes. The recorded 50% inhibitory concentrations of the respective cell lines were 45.21, 61.86 and 200.15 μg mL-1. The synthesized nanoparticles showed potent antibacterial and antifungal activities against all the tested plant and human microbial pathogens with minimal inhibitory concentration range 250-500 μg mL-1. Moreover, the feasibility of production enhancement of the synthesized nanoparticles using the fungal culture as affected by gamma irradiation was also adopted. Gamma irradiation at 1000 Gy dramatically intensified the yield of nanoparticles to 24.87 g L-1. Accordingly, these findings suggest a new and alternate approach with the excellent biotechnological potentiality for the nanoparticles production that will open up the way for the industrial manufacture of nanomaterials.

In Vitro Activity Of Ceftaroline And Comparators Against Staphylococcus aureus Isolates: Results From 6 Years Of The ATLAS Program (2012 To 2017).

BackgroundCeftaroline is effective against methicillin-resistant Staphylococcus aureus (MRSA), but the resistance patterns still need to be defined. This study aimed to investigate the susceptibility of S. aureus to ceftaroline and comparator antimicrobial agents in patients hospitalized due to infection and to observe the patterns among different regions and over the years.MethodsThe Antimicrobial Testing Leadership And Surveillance (ATLAS) program includes medical centers located in five geographical regions (Europe, Asia-Pacific, South America, Africa-West Asia, and the United States). The isolates were collected from different specimens from patients hospitalized between 2012 and 2017 due to documented complicated skin and soft tissue infection, complicated intra-abdominal infection, complicated urinary tract infection, lower respiratory tract infection, and bloodstream infection.ResultsDuring the study period, 61,045 isolates were tested, including 35,837 MRSA isolates (58.7%) and 25,208 methicillin-sensitive S. aureus (MSSA) isolates (41.3%). For MRSA, the minimal inhibitory concentration (MIC)50, MIC90, and MIC range of ceftaroline were 0.5, 2, and 0.015–64 μg/mL. The proportion of susceptible MRSA strains was 89.3%. The proportion of resistant MRSA strains was 0.7%. The susceptibility of all S. aureus, MRSA, and MSSA strains to ceftaroline remained relatively constant from 2012 to 2017. The susceptibility to ceftaroline of S. aureus, MRSA, and MSSA strains from the United States, Europe, South America, and Africa/West Asia was high, while the susceptibility of the strains from Asia-Pacific was lower, especially for MRSA.ConclusionThis study reveals the patterns of ceftaroline susceptibility of MRSA and MSSA around the world and over 6 years.

Epidemiology and Antifungal Susceptibility of Infections Caused by Trichosporon Species: An Emerging Non-Candida and Non-Cryptococcus Yeast Worldwide

AbstractIntroduction: Over the past four decades, there has been an increase in the number of fatal opportunistic invasive trichosporonosis cases especially in immunocompromised hosts. Objective: The objective of the study is to evaluate the epidemiological, clinical details and antifungal susceptibility pattern of the patients with Trichosporon infections. Materials and Methods: Twenty-four clinical isolates of Trichosporon species isolated from blood, samples, pleural fluid and nail were included in this study, over a period of 12 years (2005–2016) in a tertiary hospital in North India. The isolates were characterised phenotypically and few representative isolates were sequenced also. The minimum inhibitory concentration (MIC) was determined as per Clinical and Laboratory Standards Institute, 2012. Results:Trichosporon spp. from blood culture (57.78%), nail (37.5%) and pleural fluid (4.17%). On phenotypic tests, 79.16% of the isolates were Trichosporon asahii, followed by Trichosporon dermatis (8.33%), Trichosporon japonicum (4.17%), Trichosporon ovoides (4.17%) and Trichosporon mucoides (4.17%). The MIC range of Trichosporon species from invasive infections were fluconazole (0.06–256 μg/ml), amphotericin B (0.125–16 μg/ml), voriconazole (0.0616–8 μg/ml), posaconazole (0.0616–32 μg/ml) and caspofungin (8–32 μg/ml). The isolates from superficial infection were resistant to fluconazole (0.06–256 μg/ml) and itraconazole (0.125–32 μg/ml), all were susceptible to ketoconazole and while only two were resistant to voriconazole (0.25–4 μg/ml). Conclusion:T. asahii was the most common isolate. Disseminated trichosporonosis is being increasingly reported worldwide including India and represents a challenge for both diagnosis and species identification. Prognosis is limited, and antifungal regimens containing triazoles appear to be the best therapeutic approach. In addition, accurate identification, removal of central venous lines and voriconazole-based treatment along with control of underlying conditions were associated with favourable outcomes.

Evaluation of Antimicrobial Activities of Fractions of Plant Parts of Pterocarpus santalinoides

Aims: The study aims to investigate the antimicrobial activities of the leaves, seeds, bark, and root of Pterocarpus santalinoides plant.&#x0D; Study Design: Agar well diffusion and Agar well dilution methods were used to test the preliminary antimicrobial and minimum inhibitory/bactericidal/fungicidal concentrations respectively of Pterocarpus santalinoides plants.&#x0D; Place and Duration of Study: Department of Pharmaceutical Microbiology and Biotechnology, Faculty of Pharmaceutical Sciences, Nnamdi Azikiwe University, Agulu Campus, Nigeria, between February – October, 2017.&#x0D; Methodology: Primary extraction and fractionation of the plant parts were undertaken with methanol, butanol, ethyl acetate, and n-hexane. Agar diffusion method for the primary antimicrobial screening on Muller-Hinton agar (bacteria) and Sabouraud dextrose agar (fungi) were used to assess the antimicrobial activities of the sixteen (16) samples on some microbial isolates namely Salmonella typhi, Escherichia coli, Candida albicans, Aspergillus niger, Microsporon canis, and Trichophyton rubrum. The minimum Inhibitory concentration (MIC), minimum bactericidal/fungicidal concentration (MBC/MFC) and percentage inhibition diameter growth (PIDG) of the samples that yielded positive activity were also evaluated.&#x0D; Results: Twelve (12) samples exhibited inhibitory activity on at least one or more of the test isolates. The MIC range observed for the extracts and fractions that yielded positive activity was 12.5 – 100 mg/ml. The n-hexane fraction of the plant root indicated the best value of 12.5 mg/ml against M. canis. The best MBC/MFC value of 25 mg/ml was observed with the ethyl acetate fraction of the bark (against E. coli and M. canis) and the n-hexane fraction of the root (against M. canis). The result showed S. typhi to be the most sensitive organism to the metabolites of P. santalinoides. Extended-spectrum activity was observed with the ethyl acetate fraction of the bark against three (3) of the test isolates namely S. typhi, E. coli and M. canis. The determination of PIDG values for the test organisms against the plants’ extracts/fractions showed that crude methanol extract (28.57%) and ethyl-acetate fraction (0.14%) of the leaves, butanol fraction (0.14%) of the root (all against S. typhi) were the most potent test samples.&#x0D; Conclusion: The results indicated that the plant parts may have potential medicinal values and confirmed its use in traditional medicine.

303 Comparison of Antifungal Activities of Efinaconazole and Conventional Antifungal Agents against Dermatophytes and Yeasts

As growing the number of aging population and immunocompromised patients, there has been an increase in patients with skin fungal infections. Trichophyton rubrum, Trichophyton mentagrophytes and Candida albicans are known as the key pathogen of superficial dermatomycosis. Although itraconazole, terbinafine, amorolfine, and ciclopirox have been used for the treatment of these infections, they have limitation due to the drug side effects and lack of efficacy. In 2014, the Food and Drug Administration approved efinaconazole as a novel antifungals particular in onychomycosis. However, there has not been studied about the efficacy of efinazonazole for specific strains yet. So, we analyzed the antifungal activities of efinaconazole against T. rubrum, T. mentagrophytes, and C.albicans and compared with the antifungal activities of itraconazole, terbinafine, amorolfine, and ciclopirox in vitro. 63 strains of T. rubrum, 59 strains of T. mentagrophytes and 50 strains of C. albicans were isolated from patient with onychomycosis and tinea pedis. The antifungal activities of efinaconazole, itraconazole, terbinafine, amorolfine and ciclopirox were compared using minimal inhibitory concentration (MIC). The MIC range of efinaconazole was 0.001-0.125 μg / mL for T. rubrum, 0.0005-0.125 μg / mL for T. mentagrophytes and 0.0002-0.002 μg / mL for C. albicans. It was the lowest MIC among the antifungal agents used in this study. For most evaluated antifungal agents, a significant number of resistant strains were observed. The MICs of efinaconazole showed relatively small standard deviations. These results suggest that efinaconazole resistant strains did not appear. In summary, efinaconazole can be considered as a new alternative antifungal agent that goes beyond the limits of traditional antifungal agents.

A new acridone with antifungal properties against Candida spp. and dermatophytes, and antibiofilm activity against C. albicans.

The increase in the number of fungal infections worldwide, coupled with the limitations of current antifungal chemotherapy, demand the development of safe and effective new antifungals. Here, we presented the synthesis of a novel acridone (M14) and its antifungal properties against Candida and dermatophytes species. A series of 17 acridones was designed, synthesized and tested for its antifungal activity. The minimum inhibitory concentration (MIC) was determined by the broth microdilution method. Only the acridone M14 showed growth-inhibitory activity against reference strains and clinical isolates of Candida and dermatophytes, with MIC range of 7·81-31·25µgml-1 . Moreover, M14 exhibited fungicidal activity and prevented biofilm formation by C. albicans as well as reduced the viability of preformed biofilms, even at sub-MICs. The confocal laser scanning microscopy analysis revealed that C. albicans hyphal growth was completely inhibited in the presence of M14. Similarly, there was a severe inhibition on hyphal growth of Trichophyton rubrum. We also found that M14 has relatively low toxicity to human fibroblasts. The new acridone M14 has antifungal properties against Candida spp. and dermatophytes, and antibiofilm activity against C. albicans. In addition, M14 is relatively selective to fungal cells compared to human normal cells. Because of its in vitro antifungal activity, anti-Candida biofilm effect and moderate cytotoxicity towards normal human cell, M14 may serve as a valuable lead compound to develop a new antifungal agent.

In Vitro Interaction of Geldanamycin with Triazoles and Echinocandins Against Common and Emerging Candida Species.

The aim of this study was to determine the in vitro interactions of geldanamycin (Hsp90-inhibitor) with triazoles and echinocandins against common and emerging Candida species. Twenty clinically important Candida strains comprising C. auris, C. albicans, C. parapsilosis, and C. glabrata (each five strains) were included. In vitro interactions of geldanamycin with fluconazole, itraconazole, caspofungin and anidulafungin were determined using a checkerboard method. The results were interpreted as synergistic, indifferent and antagonistic based on the fractional inhibitory concentration index (FICI). In vitro combination of fluconazole with geldanamycin resulted in synergistic effect against C. albicans (100%), C. glabrata (80%) and C. parapsilosis (80%) (FICI range 0.009-0.5), while indifferent interactions were obtained against C. auris (FICI range 1.5-2). The overall minimum inhibitory concentration (MIC) range of fluconazole against C. albicans, C. glabrata and C. parapsilosis reduced from 16-256 to 0.25-64mg/L when combined with geldanamycin. Regarding the synergistic effect of geldanamycin with itraconazole against all strains of C. albicans, C. glabrata and C. parapsilosis (FICI range 0.009-0.375), the MIC range of this antifungal was reduced from 0.125-32mg/L when tested alone, to 0.03-1mg/L. Combinations of geldanamycin with fluconazole and itraconazole against C. auris, as well as combination of geldanamycin with caspofungin and anidulafungin against all studied Candida species, resulted in indifferent effects. No antagonism was observed. Simultaneous targeting of Hsp90 and lanosterol 14-α demethylase seems an effective approach against C. albicans, C. glabrata and C. parapsilosis. However, this combination is ineffective against the emerging pathogen C. auris.

Antimicrobial susceptibility profiles and species distribution of medically relevant Nocardia species: Results from a large tertiary laboratory in Australia.

There are limited surveillance studies on the epidemiology and resistance rates ofNocardia spp. in Australia, particularly in the jurisdiction of New South Wales. This study aimed to investigate the species distribution and antimicrobial susceptibility of a large number of contemporary (2011-2016) clinical Nocardia spp. referred to a large tertiary hospital in Sydney, Australia. A total of 270Nocardia spp. isolates identified to species level by dual-target gene sequencing were investigated. Antimicrobial susceptibility testing was performed using a Sensititre™ RAPMYCOI panel, with the minimum inhibitory concentration (MIC) range and geometric mean MIC obtained for each species and drug combination. Antimicrobial susceptibility profiles and species distribution were analysed. The respiratory system is the most affected site in nocardiosis. In this study, Nocardia nova complex was the most frequently isolated Nocardia spp. (n = 80; 29.6%), followed by Nocardia cyriacigeorgica (n = 61; 22.6%), Nocardia brasiliensis (n = 52; 19.3%) and Nocardia farcinica (n = 38; 14.1%). Of the tested isolates, 9.3% and 59.3% displayed resistance to trimethoprim/sulfamethoxazole (SXT) and imipenem, respectively. Nocardia farcinica accounted for the highest number of SXT-resistant isolates. High imipenem resistance in N. cyriacigeorgica is atypical to its drug pattern but has been reported elsewhere. All tested isolates remained susceptible to linezolid, with only 0.7% exhibiting resistance to amikacin. Linezolid and amikacin remain good empirical options for treatment of nocardiosis. Routine antimicrobial susceptibility testing ofNocardia is advisable with the detection of sulfonamide resistance and atypical antibiograms in this study.

Detection of carbapenemase-producing Enterobacterales and the BD Phoenix CPO Detect panel

ABSTRACTIntroduction: Treatment options for infections with carbapenem-resistant Enterobacterales are strongly limited. New antimicrobials are not effective against all types of carbapenemases. Therefore, rapid and reliable antimicrobial susceptibility testing and identification of the resistance mechanism are important.Areas covered: We assess several methods to determine carbapenemase production of Enterobacterales in culture and discuss the value of the novel automated BD Phoenix CPO Detect (BDPCPO) panel for the detection and classification of carbapenemases.Expert opinion: The meropenem minimum inhibitory concentration (MIC) range used in the BDPCPO panel includes the EUCAST screening breakpoint for the detection of carbapenemase producers. The phenotypic, inhibitor-based assay for detection of carbapenemase activity in the BDPCPO panel displays high sensitivity for carbapenemase detection while its specificity is modest. Therefore, confirmation testing of positive results is warranted. Nevertheless, implementing the BDPCPO panel has the potential to reduce time-to-result for detection and classification of carbapenemase producers.