In VitroActivity of Plazomicin against Gram-Negative and Gram-Positive Isolates Collected from U.S. Hospitals and Comparative Activities of Aminoglycosides against Carbapenem-ResistantEnterobacteriaceaeand Isolates Carrying Carbapenemase Genes

ABSTRACTPlazomicin and comparator agents were tested by using the CLSI reference broth microdilution method against 4,825 clinical isolates collected during 2014 and 2015 in 70 U.S. hospitals as part of the ALERT (Antimicrobial Longitudinal Evaluation and Resistance Trends) program. Plazomicin (MIC50/MIC90, 0.5/2 μg/ml) inhibited 99.2% of 4,362Enterobacteriaceaeat ≤4 μg/ml. Amikacin, gentamicin, and tobramycin inhibited 98.9%, 90.3%, and 90.3% of these isolates, respectively, by applying CLSI breakpoints. The activities of plazomicin were similar amongEnterobacteriaceaespecies, with MIC50values ranging from 0.25 to 1 μg/ml, with the exception ofProteus mirabilisand indole-positiveProteeaethat displayed MIC50values of 2 μg/ml. For 97 carbapenem-resistantEnterobacteriaceae(CRE), which included 87 isolates carryingblaKPC, plazomicin inhibited all but 1 isolate at ≤2 μg/ml (99.0% and 98.9%, respectively). Amikacin and gentamicin inhibited 64.9% and 56.7% of the CRE isolates at the respective CLSI breakpoints. Plazomicin inhibited 96.5 and 95.5% of the gentamicin-resistant isolates, 96.9 and 96.5% of the tobramycin-resistant isolates, and 64.3 and 90.0% of the amikacin-resistant isolates according to CLSI and EUCAST breakpoints, respectively. The activities of plazomicin againstPseudomonas aeruginosa(MIC50/MIC90, 4/16 μg/ml) andAcinetobacterspecies (MIC50/MIC90, 2/16 μg/ml) isolates were similar. Plazomicin was active against coagulase-negative staphylococci (MIC50/MIC90, 0.12/0.5 μg/ml) andStaphylococcus aureus(MIC50/MIC90, 0.5/0.5 μg/ml) but had limited activity againstEnterococcusspp. (MIC50/MIC90, 16/64 μg/ml) andStreptococcus pneumoniae(MIC50/MIC90, 32/64 μg/ml). Plazomicin activity against theEnterobacteriaceaetested, including CRE and isolates carryingblaKPCfrom U.S. hospitals, supports the development plan for plazomicin to treat serious infections caused by resistantEnterobacteriaceaein patients with limited treatment options.

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Antimicrobial Activity of Exebacase (Lysin CF-301) against the Most Common Causes of Infective Endocarditis

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01078-19 ◽

2019 ◽

Vol 63 (10) ◽

Cited By ~ 7

Author(s):

Aubrey Watson ◽

Jun Taek Oh ◽

Karen Sauve ◽

Patricia A. Bradford ◽

Cara Cassino ◽

...

Keyword(s):

Antimicrobial Activity ◽

Cell Wall ◽

Infective Endocarditis ◽

Broth Microdilution ◽

Coagulase Negative Staphylococci ◽

Content Type ◽

Microdilution Method ◽

Cell Wall Hydrolase ◽

Broth Microdilution Method ◽

Common Causes

ABSTRACT Exebacase, a recombinantly produced lysin (cell wall hydrolase), and comparator antibiotics were tested by the broth microdilution method against strain sets of Staphylococcus and Streptococcus spp., which are the most common causes of infective endocarditis in humans. Exebacase was active against all Staphylococcus spp. tested, including S. aureus and coagulase-negative staphylococci (MIC50/90, 0.5/1 μg/ml). Activity against Streptococcus spp. was variable, with S. pyogenes, S. agalactiae, and S. dysgalactiae (MIC50/90, 1/2 μg/ml) among the most susceptible.

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Antibiotic Resistance among Clinical Ureaplasma Isolates Recovered from Neonates in England and Wales between 2007 and 2013

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00889-15 ◽

2015 ◽

Vol 60 (1) ◽

pp. 52-56 ◽

Cited By ~ 29

Author(s):

Michael L. Beeton ◽

Victoria J. Chalker ◽

Lucy C. Jones ◽

Nicola C. Maxwell ◽

O. Brad Spiller

Keyword(s):

Antibiotic Resistance ◽

Molecular Mechanisms ◽

Treatment Options ◽

Tetracycline Resistance ◽

Health Clinic ◽

Broth Microdilution ◽

England And Wales ◽

Content Type ◽

Microdilution Method ◽

Broth Microdilution Method

ABSTRACTUreaplasmaspp. are associated with numerous clinical sequelae with treatment options being limited due to patient and pathogen factors. This report examines the prevalence and mechanisms of antibiotic resistance among clinical strains isolated from 95 neonates, 32 women attending a sexual health clinic, and 3 patients under investigation for immunological disorders, between 2007 and 2013 in England and Wales. MICs were determined by using broth microdilution assays, and a subset of isolates were compared using the broth microdilution method and the Mycoplasma IST2 assay. The underlying molecular mechanisms for resistance were determined for all resistant isolates. Three isolates carried thetet(M) tetracycline resistance gene (2.3%; confidence interval [CI], 0.49 to 6.86%); two isolates were ciprofloxacin resistant (1.5%; CI, 0.07 to 5.79%) but sensitive to levofloxacin and moxifloxacin, while no resistance was seen to any macrolides tested. The MIC values for chloramphenicol were universally low (2 μg/ml), while inherently high-level MIC values for gentamicin were seen (44 to 66 μg/ml). The Mycoplasma IST2 assay identified a number of false positives for ciprofloxacin resistance, as the method does not conform to international testing guidelines. While antibiotic resistance amongUreaplasmaisolates remains low, continued surveillance is essential to monitor trends and threats from importation of resistant clones.

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Baseline Activity of Telavancin against Gram-Positive Clinical Isolates Responsible for Documented Infections in U.S. Hospitals (2011-2012) as Determined by the Revised Susceptibility Testing Method

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.04052-14 ◽

2014 ◽

Vol 59 (1) ◽

pp. 702-706 ◽

Cited By ~ 18

Author(s):

Rodrigo E. Mendes ◽

David J. Farrell ◽

Helio S. Sader ◽

Robert K. Flamm ◽

Ronald N. Jones

Keyword(s):

Staphylococcus Aureus ◽

Susceptibility Testing ◽

The United States ◽

Broth Microdilution ◽

Content Type ◽

Testing Method ◽

Microdilution Method ◽

Baseline Activity ◽

Broth Microdilution Method ◽

Vancomycin Resistant

ABSTRACTTelavancin had MIC50and MIC90values of 0.03 and 0.06 μg/ml (100.0% susceptible), respectively, against methicillin-resistant and -susceptibleStaphylococcus aureus. Telavancin was active against vancomycin-susceptibleEnterococcus faecalis(MIC50/90, 0.12/0.12 μg/ml; 100% susceptible) andEnterococcus faecium(MIC50/90, 0.03/0.06 μg/ml), while higher MIC values were obtained against vancomycin-resistantE. faecium(MIC50/90, 1/2 μg/ml) andE. faecalis(MIC50/90, >2/>2 μg/ml). Streptococci showed telavancin modal MIC results of ≤0.015 μg/ml, except againstStreptococcus agalactiae(i.e., 0.03 μg/ml). This study reestablishes the telavancin spectrum of activity against isolates recovered from the United States (2011-2012) using the revised broth microdilution method.

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In Vitro Activity of WCK 5222 (Cefepime-Zidebactam) against Worldwide Collected Gram-Negative Bacilli Not Susceptible to Carbapenems

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01432-20 ◽

2020 ◽

Vol 64 (12) ◽

Cited By ~ 1

Author(s):

James A. Karlowsky ◽

Meredith A. Hackel ◽

Samuel K. Bouchillon ◽

Daniel F. Sahm

Keyword(s):

Antimicrobial Agents ◽

Multidrug Resistant ◽

Limiting Factor ◽

Gram Negative ◽

Content Type ◽

Microdilution Method ◽

Carbapenem Resistant ◽

Broth Microdilution Method ◽

Universal Stability

ABSTRACT WCK 5222 (cefepime-zidebactam, 2 g + 1g, every 8 h [q8h]) is in clinical development for the treatment of infections caused by carbapenem-resistant and multidrug-resistant (MDR) Gram-negative bacilli. We determined the in vitro susceptibility of 1,385 clinical isolates of non-carbapenem-susceptible Enterobacterales, MDR Pseudomonas aeruginosa (also non-carbapenem susceptible), Stenotrophomonas maltophilia, and Burkholderia spp. collected worldwide (49 countries) from 2014 to 2016 to cefepime-zidebactam (1:1 ratio), ceftazidime-avibactam, imipenem-relebactam, ceftolozane-tazobactam, and colistin using the CLSI broth microdilution method. Cefepime-zidebactam inhibited 98.5% of non-carbapenem-susceptible Enterobacterales (n = 1,018) at ≤8 μg/ml (provisional cefepime-zidebactam-susceptible MIC breakpoint). Against the subset of metallo-β-lactamase (MBL)-positive Enterobacterales (n = 214), cefepime-zidebactam inhibited 94.9% of isolates at ≤8 μg/ml. Further, it inhibited 99.6% of MDR P. aeruginosa (n = 262) isolates at ≤32 μg/ml (proposed cefepime-zidebactam-susceptible pharmacokinetic/pharmacodynamic MIC breakpoint), including all MBL-positive isolates (n = 94). Moreover, cefepime-zidebactam was active against the majority of isolates of Enterobacterales (≥95%) and P. aeruginosa (99%) that were not susceptible to ceftazidime-avibactam, ceftolozane-tazobactam, imipenem-relebactam, and colistin. Most isolates (99%) of S. maltophilia (n = 101; MIC50, 8 μg/ml; MIC90, 32 μg/ml) and Burkholderia spp. (n = 4; MIC range, 16 to 32 μg/ml) were also inhibited by cefepime-zidebactam at ≤32 μg/ml. The activity of cefepime-zidebactam against carbapenem-resistant Gram-negative bacteria is ascribed to its β-lactam enhancer mechanism of action (i.e., zidebactam binding to penicillin binding protein 2 [PBP2] and its universal stability to both serine β-lactamases and MBLs). The results from this study support the continued development of cefepime-zidebactam as a potential therapy for infections caused by Enterobacterales, P. aeruginosa, and other nonfermentative Gram-negative bacilli where resistance to marketed antimicrobial agents is a limiting factor.

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In vitro anti-microbial activity of extracts from the callus cultures of some Nigella species

Biologia ◽

10.2478/s11756-006-0052-6 ◽

2006 ◽

Vol 61 (3) ◽

Cited By ~ 7

Author(s):

Premysl Landa ◽

Petr Marsik ◽

Tomas Vanek ◽

Vojtech Rada ◽

Ladislav Kokoska

Keyword(s):

Staphylococcus Aureus ◽

Microbial Activity ◽

Staphylococcus Epidermidis ◽

Callus Cultures ◽

Broth Microdilution ◽

Bacterial Strains ◽

Gram Negative ◽

Microdilution Method ◽

Broth Microdilution Method

AbstractCrude methanol extracts from callus cultures of Nigella arvensis, N. damascena, N. hispanica, N. integrifolia, and N. sativa were investigated for their anti-microbial activity. Growth inhibition was determined in Gram-positive and Gram-negative bacterial strains as well as in yeast by using a broth-microdilution method. The results showed that the extracts of all calli tested exhibited significant anti-microbial activity, especially against Bacillus cereus, Staphylococcus aureus and Staphylococcus epidermidis. Compared with other Nigella species, a callus culture of N. hispanica was the most effective against the microorganisms used in this study.

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In Vitro Activity of Eravacycline against Gram-Negative Bacilli Isolated in Clinical Laboratories Worldwide from 2013 to 2017

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01699-19 ◽

2019 ◽

Vol 64 (3) ◽

Cited By ~ 3

Author(s):

Ian Morrissey ◽

Melanie Olesky ◽

Stephen Hawser ◽

Sibylle H. Lob ◽

James A. Karlowsky ◽

...

Keyword(s):

Antimicrobial Agents ◽

Multidrug Resistant ◽

Clinical Isolates ◽

Gram Negative ◽

Content Type ◽

Microdilution Method ◽

Clinical Laboratories ◽

Serious Infections ◽

Broth Microdilution Method

ABSTRACT Eravacycline is a novel, fully synthetic fluorocycline antibiotic developed for the treatment of serious infections, including those caused by multidrug-resistant (MDR) pathogens. Here, we evaluated the in vitro activities of eravacycline and comparator antimicrobial agents against a global collection of frequently encountered clinical isolates of Gram-negative bacilli. The CLSI broth microdilution method was used to determine MIC data for isolates of Enterobacterales (n = 13,983), Acinetobacter baumannii (n = 2,097), Pseudomonas aeruginosa (n = 1,647), and Stenotrophomonas maltophilia (n = 1,210) isolated primarily from respiratory, intra-abdominal, and urinary specimens by clinical laboratories in 36 countries from 2013 to 2017. Susceptibilities were interpreted using both CLSI and EUCAST breakpoints. Multidrug-resistant (MDR) isolates were defined by resistance to agents from ≥3 different antimicrobial classes. The MIC90s ranged from 0.25 to 1 μg/ml for Enterobacteriaceae and were 1 μg/ml for A. baumannii and 2 μg/ml for S. maltophilia, Proteus mirabilis, and Serratia marcescens. Eravacycline’s potency was up to 4-fold greater than that of tigecycline against genera/species of Enterobacterales, A. baumannii, and S. maltophilia. The MIC90s for five of six individual genera/species of Enterobacterales and A. baumannii were within 2-fold of the MIC90s for their respective subsets of MDR isolates, while the MDR subpopulation of Klebsiella spp. demonstrated 4-fold higher MIC90s. Eravacycline demonstrated potent in vitro activity against the majority of clinical isolates of Gram-negative bacilli, including MDR isolates, collected over a 5-year period. This study further underscores the potential benefit of eravacycline in the treatment of infections caused by MDR Gram-negative pathogens.

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Antimicrobial Activity of Ceftaroline-Avibactam Tested against Clinical Isolates Collected from U.S. Medical Centers in 2010-2011

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02436-12 ◽

2013 ◽

Vol 57 (4) ◽

pp. 1982-1988 ◽

Cited By ~ 32

Author(s):

Helio S. Sader ◽

Robert K. Flamm ◽

Ronald N. Jones

Keyword(s):

Staphylococcus Aureus ◽

Antimicrobial Activity ◽

Streptococcus Pneumoniae ◽

Enterobacter Cloacae ◽

Broth Microdilution ◽

Methicillin Resistant ◽

Content Type ◽

Microdilution Method ◽

Medical Centers ◽

Broth Microdilution Method

ABSTRACTCeftaroline-avibactam and comparator agents were tested by the broth microdilution method against 20,089 isolates consecutively collected in 2010 and 2011 from 75 U.S. medical centers. Ceftaroline-avibactam was active againstEnterobacteriaceae(4,908 strains; MIC90, 0.25 μg/ml; highest MIC, 4 μg/ml), including meropenem-nonsusceptibleKlebsiellaspp. and ceftazidime-nonsusceptibleEnterobacter cloacaestrains (MIC90, 1 μg/ml for both). Ceftaroline-avibactam was also active against ceftriaxone-nonsusceptibleStreptococcus pneumoniae(MIC90, 0.25 μg/ml) and methicillin-resistantStaphylococcus aureus(MIC90, 1 μg/ml).

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In VitroAntistaphylococcal Effects ofEmbelia schimperiExtracts and Their Component Embelin with Oxacillin and Tetracycline

Evidence-based Complementary and Alternative Medicine ◽

10.1155/2015/175983 ◽

2015 ◽

Vol 2015 ◽

pp. 1-7 ◽

Cited By ~ 4

Author(s):

Johana Rondevaldova ◽

Olga Leuner ◽

Alemtshay Teka ◽

Ermias Lulekal ◽

Jaroslav Havlik ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Medicinal Plants ◽

Bacterial Infections ◽

Inhibitory Concentration ◽

Developed Countries ◽

Positive Interactions ◽

Fractional Inhibitory Concentration ◽

Broth Microdilution ◽

Microdilution Method ◽

Broth Microdilution Method

Bacterial infections are in less-developed countries traditionally treated by remedies prepared from medicinal plants.Embelia schimperi(Vatke) is a plant used as a taenicide or disinfectant in Ethiopia, very often taken mixed with another plant species. In the present study, we examined two extracts prepared from seeds and twigs with leaves ofE. schimperiand its main present secondary metabolite embelin for their antibacterial combinatory effect with oxacillin and tetracycline against sensitive and resistantStaphylococcus aureusstrains. Minimum inhibitory concentrations were determined through the broth microdilution method, whereas the combinatory effect was evaluated through fractional inhibitory concentration sum (ΣFIC) indices. Results show many positive interactions and synergy occurring in embelin and oxacillin combinations against 4 out of 9 strains (ΣFIC 0.203–0.477) and for embelin and tetracycline combination against 3 out of 9 strains (ΣFIC 0.400–0.496). Moreover, the resistance to oxacillin has been overcome in 2 strains and to tetracycline in 3 strains. According to our knowledge, this is the first study showing antimicrobial combinatory effect ofE. schimperias well as of embelin. These findings can be used for the further research targeted on the development of new antistaphylococcal agents.

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Antifungal Susceptibility Testing of Malassezia spp. with an Optimized Colorimetric Broth Microdilution Method

Journal of Clinical Microbiology ◽

10.1128/jcm.00338-17 ◽

2017 ◽

Vol 55 (6) ◽

pp. 1883-1893 ◽

Cited By ~ 22

Author(s):

Cheryl Leong ◽

Antonino Buttafuoco ◽

Martin Glatz ◽

Philipp P. Bosshard

Keyword(s):

Susceptibility Testing ◽

Skin Diseases ◽

Antifungal Susceptibility ◽

Drug Susceptibility ◽

Drug Susceptibility Testing ◽

Broth Microdilution ◽

Content Type ◽

Microdilution Method ◽

Broth Microdilution Method ◽

Colorimetric Indicator

ABSTRACTMalasseziais a genus of lipid-dependent yeasts. It is associated with common skin diseases such as pityriasis versicolor and atopic dermatitis and can cause systemic infections in immunocompromised individuals. Owing to the slow growth and lipid requirements of these fastidious yeasts, convenient and reliable antifungal drug susceptibility testing assays forMalasseziaspp. are not widely available. Therefore, we optimized a broth microdilution assay for the testing ofMalasseziathat is based on the CLSI and EUCAST assays forCandidaand other yeasts. The addition of ingredients such as lipids and esculin provided a broth medium formulation that enabled the growth of allMalasseziaspp. and could be read, with the colorimetric indicator resazurin, by visual and fluorescence readings. We tested the susceptibility of 52 strains of 13Malasseziaspecies to 11 commonly used antifungals. MIC values determined by visual readings were in good agreement with MIC values determined by fluorescence readings. The lowest MICs were found for the azoles itraconazole, posaconazole, and voriconazole, with MIC90values of 0.03 to 1.0 μg/ml, 0.06 to 0.5 μg/ml, and 0.03 to 2.0 μg/ml, respectively. AllMalasseziaspp. were resistant to echinocandins and griseofulvin. SomeMalasseziaspp. also showed high MIC values for ketoconazole, which is the most widely recommended topical antifungal to treatMalasseziaskin infections. In summary, our assay enables the fast and reliable susceptibility testing ofMalasseziaspp. with a large panel of different antifungals.

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Antibacterial Triterpenoids from the Bark of Sonneratia alba (Lythraceae)

Natural Product Communications ◽

10.1177/1934578x1501000215 ◽

2015 ◽

Vol 10 (2) ◽

pp. 1934578X1501000

Author(s):

Harizon ◽

Betry Pujiastuti ◽

Dikdik Kurnia ◽

Dadan Sumiarsa ◽

Yoshihito Shiono ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Antibacterial Activity ◽

Mass Spectrometric ◽

Broth Microdilution ◽

Mass Spectrometric Data ◽

Spectrometric Data ◽

Gram Positive Bacteria ◽

Microdilution Method ◽

Sonneratia Alba ◽

Broth Microdilution Method

The new lupane-type triterpenoid, 3β-hydroxy-lup-9(11), 12-diene, 28-oic acid (1), along with two known lupane-type triterpenoids, lupeol (2) and lupan-3p-ol (3), were isolated from the bark of Sonnetaria alba. The structure of the new compound was elucidated on the basis of spectroscopic and mass spectrometric data analysis. Using the broth microdilution method, all compounds exhibited antibacterial activity against the Gram-positive bacteria Staphylococcus aureus ATCC 6538 and Streptococcus mutans ATCC 25175, with minimum inhibitory concentrations ranging from 15-33 to 35-55 ng/mL, respectively.

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