scholarly journals In Vitro Activities of Daptomycin against 2,789 Clinical Isolates from 11 North American Medical Centers

2001 ◽  
Vol 45 (6) ◽  
pp. 1919-1922 ◽  
Author(s):  
Arthur L. Barry ◽  
Peter C. Fuchs ◽  
Steven D. Brown
Keyword(s):  
Clinical Isolates ◽  
In Vitro Activity ◽  
Broth Microdilution ◽  
In Vitro Susceptibility ◽  
Medical Centers ◽  
Mueller Hinton ◽  
Calcium Cations ◽  
Important Exception ◽  
Mueller Hinton Broth

ABSTRACT The in vitro activity of daptomycin is affected by the concentration of calcium cations in the test medium. Mueller-Hinton broth is currently adjusted to contain 10 to 12.5 mg of magnesium per liter and 20 to 25 mg of calcium per liter, but for testing of daptomycin, greater concentrations of calcium (50 mg/liter) are recommended to better resemble the normal concentration of ionized calcium in human serum. Two levels of calcium were used for broth microdilution tests of 2,789 recent clinical isolates of gram-positive bacterial pathogens. MICs of daptomycin were two- to fourfold lower when the broth contained additional calcium. For most species, however, the percentages of strains that were inhibited by 2.0 μg of daptomycin per ml were essentially identical with the two broth media. Enterococci were the important exception; i.e., 92% were inhibited when tested in calcium-supplemented broth but only 35% were inhibited by 2.0 μg/ml without the additional calcium. This type of information should be considered when selecting criteria for defining in vitro susceptibility to daptomycin.

scholarly journals In Vitro Activity of the Siderophore Cephalosporin, Cefiderocol, against a Recent Collection of Clinically Relevant Gram-Negative Bacilli from North America and Europe, Including Carbapenem-Nonsusceptible Isolates (SIDERO-WT-2014 Study)

2017 ◽  
Vol 61 (9) ◽  
Author(s):  
Meredith A. Hackel ◽  
Masakatsu Tsuji ◽  
Yoshinori Yamano ◽  
Roger Echols ◽  
James A. Karlowsky ◽  
...  
Keyword(s):  
North America ◽  
North American ◽  
Clinical Isolates ◽  
In Vitro Activity ◽  
Gram Negative ◽  
Content Type ◽  
Mueller Hinton ◽  
Recent Collection ◽  
Mueller Hinton Broth

ABSTRACT Cefiderocol (formerly S-649266) is an investigational siderophore cephalosporin. Iron-depleted cation-adjusted Mueller-Hinton broth (ID-CAMHB) was prepared according to the Clinical and Laboratory Standards Institute (CLSI) protocol and used to perform broth microdilution testing of cefiderocol against a 2014-2015 collection of clinical isolates of Gram-negative bacilli from North America (n = 4,239) and Europe (n = 4,966). The concentrations of cefiderocol inhibiting 90% of isolates tested (MIC90s) were 0.5 μg/ml (North America; n = 3,007) and 1 μg/ml (Europe; n = 3,080) for all isolates of Enterobacteriaceae; 1 μg/ml (North America; n = 30) and 4 μg/ml (Europe; n = 139) for meropenem-nonsusceptible (MIC ≥ 2 μg/ml) isolates of Enterobacteriaceae; 0.5 μg/ml for both North American (n = 765) and European (n = 765) isolates of Pseudomonas aeruginosa; 0.5 μg/ml (North America; n = 151) and 1 μg/ml (Europe; n = 202) for meropenem-nonsusceptible (MIC ≥ 4 μg/ml) isolates of P. aeruginosa; 1 μg/ml for both North American (n = 309) and European (n = 839) isolates of all Acinetobacter baumannii strains as well as for both North American (n = 173) and European (n = 595) isolates of meropenem-nonsusceptible A. baumannii; and 0.5μg/ml (North America; n = 152) and 0.25 μg/ml (Europe; n = 276) for isolates of Stenotrophomonas maltophilia. MICs of cefiderocol were ≤4 μg/ml for 99.9% (6,078/6,087) of all Enterobacteriaceae, 97.0% (164/169) of meropenem-nonsusceptible Enterobacteriaceae, 99.9% (1,529/1,530) of all P. aeruginosa isolates, 100% (353/353) of meropenem-nonsusceptible P. aeruginosa isolates, 97.6% (1,120/1,148) of all A. baumannii isolates, 96.9% (744/768) of meropenem-nonsusceptible A. baumannii isolates, 100% of isolates of S. maltophilia (428/428) and 93.8% of isolates of Burkholderia cepecia (11/12). We conclude that cefiderocol demonstrated potent in vitro activity against a recent collection of clinical isolates of commonly encountered Gram-negative bacilli, including carbapenem-nonsusceptible isolates.

scholarly journals 1593. Antimicrobial Activity of Ceftazidime-Avibactam and Comparator Agents Against OXA-48 β-lactamase–Producing Enterobacterales Collected in International Medical Centers, Including the United States, in 2017–2018

2020 ◽  
Vol 7 (Supplement_1) ◽  
pp. S793-S793
Author(s):  
Lynn-Yao Lin ◽  
Dmitri Debabov ◽  
William Chang
Keyword(s):  
Antimicrobial Agents ◽  
The United States ◽  
Resistance Mechanisms ◽  
Clinical Isolates ◽  
Surveillance Program ◽  
Multiple Resistance ◽  
In Vitro Susceptibility ◽  
Medical Centers ◽  
Custom Made

Abstract Background OXA-48 is a carbapenemase with low-level hydrolytic activity toward cephalosporins. This study evaluated in vitro activities of ceftazidime-avibactam (CAZ-AVI), meropenem (MEM), meropenem-vaborbactam (MVB), ceftolozane-tazobactam (C/T), and other antimicrobial agents against 113 OXA-48-producing Enterobacterales with multiple resistance mechanisms collected in a 2017–2018 global surveillance program. Methods Nonduplicate clinical isolates of 113 Enterobacterales were collected from medical centers in 25 countries in 2017–2018. In vitro susceptibility tests were performed by broth microdilution with a custom-made panel consisting of CAZ-AVI, ceftazidime (CAZ), MEM, MVB, C/T, colistin (COL), gentamicin (GEN), levofloxacin (LEV), and amikacin (AMK). Whole genome sequencing or quantitative PCR data were used to analyze resistance mechanisms, such as OXA-48, extended-spectrum β-lactamase (ESBL), original-spectrum β-lactamase (OSBL), and AmpC β-lactamase. Clinical and Laboratory Standards Institute breakpoints were applied for susceptibility interpretations. Results Of 113 OXA-48–producing clinical isolates, 20 carried OXA-48 alone. The remaining 93 isolates carried additional β-lactamases, including 63 with ESBL (CTX-M-15) + OSBL (SHV, TEM), 15 with AmpC (DHA, AAC, CMY) + ESBL (CTX-M-15), and 15 with OSBL (SHV, TEM). 99.1% (all but 1) of all isolates tested were susceptible to CAZ-AVI, whereas 71.7%, 17.7%, and 14.2% were susceptible to MVB, MEM, and C/T, respectively. Among isolates harboring multiple resistance mechanisms (OXA-48 + ESBL + OSBL; n=63), 98.4%, 69.8%, 11.1%, and 7.9% were susceptible to CAZ-AVI, MVB, MEM, and C/T, respectively. Among isolates carrying OXA-48 + AmpC + ESBL + OSBL (n=15), 100%, 66.7%, 13.3%, and 13.3% were susceptible to CAZ-AVI, MVB, MEM, and C/T, respectively (Table). Aminoglycosides (AMK and GEN) and other β-lactams (eg, CAZ) were 20%–90% active against these isolates. COL was the second most effective comparator, inhibiting 83.2% of these isolates. Table Conclusion CAZ-AVI was the most effective agent in this study compared with other antibiotics, including β-lactams, β-lactam–β-lactamase inhibitor combinations, aminoglycosides, and COL, against OXA-48-producing Enterobacterales carrying multiple β-lactamases. Disclosures Lynn-Yao Lin, MS, AbbVie (Employee) Dmitri Debabov, PhD, AbbVie (Employee) William Chang, BS, AbbVie (Employee)

In vitro susceptibility of Mycobacterium abscessus complex and feasibility of standardizing treatment regimens

2020 ◽  
Author(s):  
Ka Lip Chew ◽  
Sophie Octavia ◽  
Joelle Go ◽  
Sally Ng ◽  
Yit Er Tang ◽  
...  
Keyword(s):  
Retrospective Review ◽  
Susceptibility Testing ◽  
Mycobacterium Abscessus ◽  
In Vitro Activity ◽  
Broth Microdilution ◽  
In Vitro Susceptibility ◽  
Treatment Regimens ◽  
Mycobacterium Abscessus Complex ◽  
Additional Testing

Abstract Objectives To determine the in vitro susceptibility of members of the Mycobacterium abscessus complex to routinely tested antibiotics and to an extended antibiotic panel. Methods Non-duplicate isolates for which susceptibility testing results were available were included in this study. Retrospective laboratory records were reviewed, including tigecycline susceptibility results, and testing was performed with additional drugs, including vancomycin, dalbavancin, telavancin, oritavancin, rifabutin, delafloxacin, eravacycline, clofazimine and bedaquiline using broth microdilution (Sensititre, Thermo Fisher). Results A total of 218 M. abscessus complex isolates were included for retrospective review, of which 151 were respiratory isolates. Of these 218 isolates, 211 were available for additional testing with the extended antibiotic panel. Of these, 146 were respiratory isolates. One isolate had a vancomycin MIC of 2 mg/L and MICs of all other isolates were >8 mg/L. All isolates had MICs of >8 mg/L for oritavancin, dalbavancin and telavancin. One isolate had a delafloxacin MIC of 4 mg/L and MICs of all other isolates were >8 mg/L. The MIC50/MIC90s of rifabutin, tigecycline, eravacycline, clofazimine and bedaquiline were 16/32, 0.5/1, 0.12/0.25, 0.12/0.25 and 0.06/0.12 mg/L, respectively. Conclusions In vitro activity was demonstrated for clofazimine, bedaquiline and eravacycline, indicating potential for inclusion as standardized therapy for M. abscessus complex infections.

scholarly journals In Vitro Activity of Meropenem-Vaborbactam against Clinical Isolates of KPC-Positive Enterobacteriaceae

2017 ◽  
Vol 62 (1) ◽  
Author(s):  
Meredith A. Hackel ◽  
Olga Lomovskaya ◽  
Michael N. Dudley ◽  
James A. Karlowsky ◽  
Daniel F. Sahm
Keyword(s):  
Clinical Isolates ◽  
In Vitro Activity ◽  
Broth Microdilution ◽  
Content Type ◽  
Class A ◽  
Microdilution Method ◽  
Fixed Concentration ◽  
Broth Microdilution Method ◽  
The U.S

ABSTRACT Vaborbactam (formerly RPX7009) is a novel inhibitor of serine β-lactamases, including Ambler class A carbapenemases, such as KPCs. The current study evaluated the in vitro activity of the combination agent meropenem-vaborbactam against a global collection of 991 isolates of KPC-positive Enterobacteriaceae collected in 2014 and 2015 using the Clinical and Laboratory Standards Institute (CLSI) standard broth microdilution method. The MIC90 of meropenem (when tested with a fixed concentration of 8 μg/ml of vaborbactam) for isolates of KPC-positive Enterobacteriaceae was 1 μg/ml, and MIC values ranged from ≤0.03 to >32 μg/ml; 99.0% (981/991) of isolates had meropenem-vaborbactam MICs of ≤4 μg/ml, the U.S. FDA-approved MIC breakpoint for susceptibility to meropenem-vaborbactam (Vabomere). Vaborbactam lowered the meropenem MIC50 from 32 to 0.06 μg/ml and the MIC90 from >32 to 1 μg/ml. There were no differences in the activity of meropenem-vaborbactam when the isolates were stratified by KPC variant type. We conclude that meropenem-vaborbactam demonstrates potent in vitro activity against a worldwide collection of clinical isolates of KPC-positive Enterobacteriaceae collected in 2014 and 2015.

scholarly journals In Vitro Susceptibility of Ureaplasma urealyticum and Mycoplasma hominis Isolates in Argentina

1995 ◽  
Vol 3 (6) ◽  
pp. 236-240
Author(s):  
Jorgelina Smayevsky ◽  
Silvia Relloso ◽  
Mariela Pundik ◽  
Alejandra Lanza ◽  
Gabriela Weltman ◽  
...  
Keyword(s):  
Ureaplasma Urealyticum ◽  
Mycoplasma Hominis ◽  
Clinical Isolates ◽  
Broth Microdilution ◽  
In Vitro Susceptibility ◽  
Surveillance Studies ◽  
Agar Dilution ◽  
High Mics

Objective: Our goal was to determine the in vitro susceptibility of Ureaplasma urealyticum and Mycoplasma hominis isolates to several antibiotics in Argentina.Methods: Ninety-four strains of U. urealyticum and 18 strains of M. hominis isolated from cervical and urethral specimens were studied. Broth microdilution and agar dilution tests for minocycline, tetracycline, erythromycin, ciprofloxacin, and ofloxacin were performed.Results: Both methods proved to be reliable and reproducible for U. urealyticum and M. hominis, with no major differences in results. The U. urealyticurn strains were inhibited by erythromycin at MICs ranging from ≤0.5 to >8 μ/ml. Ofloxacin showed the highest activity against this latter organism. No differences between tetracycline and minocycline MICs were observed with U. urealyticum. Two M. hominis strains displaying high MICs both to tetracycline and to minocycline were detected.Conclusions: The emerging resistance of mycoplasmas to certain antibiotics emphasizes the need to undertake further surveillance studies on the clinical isolates of such organisms.

scholarly journals Two-Site Evaluation of the Colistin Broth Disk Elution Test To Determine Colistin In Vitro Activity against Gram-Negative Bacilli

2018 ◽  
Vol 57 (2) ◽  
Author(s):  
Patricia J. Simner ◽  
Yehudit Bergman ◽  
Marisol Trejo ◽  
Ava A. Roberts ◽  
Remy Marayan ◽  
...  
Keyword(s):  
Growth Control ◽  
Practical Method ◽  
Clinical Isolates ◽  
Gram Negative ◽  
Content Type ◽  
Mueller Hinton ◽  
Site Evaluation ◽  
Broth Macrodilution ◽  
Mueller Hinton Broth

ABSTRACT Limited methods for colistin MIC determination are available to clinical microbiology laboratories. The purpose of this study was to evaluate the accuracy of the colistin broth disk elution (CBDE) test compared to that of broth microdilution (BMD) for identifying colistin MICs. CBDE was compared to colistin BMD using a collection of Gram-negative bacilli tested at two U.S. microbiology laboratories. The isolates tested included 121 retrospective clinical isolates, 45 prospective clinical isolates, and 6 mcr-1-positive Escherichia coli isolates. CBDE was performed with four 10-ml cation-adjusted Mueller-Hinton broth tubes per isolate, to which 0, 1, 2, and 4 colistin 10-µg disks were added, generating final concentrations in the tubes of 0 (growth control), 1, 2, and 4 µg/ml, respectively. MICs were evaluated visually and interpreted using Clinical and Laboratory Standards Institute breakpoints. Site 2 also compared CBDE to the reference broth macrodilution (BMAD) method (n = 110 isolates). Overall, CBDE yielded a categorical agreement (CA) and essential agreement (EA) of 98% and 99%, respectively, compared to the results of colistin BMD. Very major errors occurred for mcr-1-producing strains, with MICs fluctuating from 2 to 4 µg/ml on repeat testing. The results for all other isolates were in CA with those of BMD. CBDE versus BMAD had an EA of 100% and a CA of 100%. Compared to currently used techniques, CBDE is an easy and practical method to perform colistin MIC testing. Some mcr-1-producing isolates yielded MICs of 2 µg/ml by CBDE and 4 µg/ml by BMD. As such, the results for isolates with colistin MICs of 2 µg/ml by CBDE should be confirmed by the reference BMD method, and isolates with MICs of ≥2 µg/ml should be evaluated for the presence of mcr genes.

Comparative in Vitro Activity of Antiseptics and Disinfectants Versus Clinical Isolates ofCandida Species

1999 ◽  
Vol 20 (10) ◽  
pp. 676-684 ◽  
Author(s):  
Jan Silverman ◽  
Jose A. Vazquez ◽  
Jack D. Sobel ◽  
Marcus J. Zervos
Keyword(s):  
Tertiary Hospital ◽  
Culture Collection ◽  
Vitro Activity ◽  
Clinical Isolates ◽  
In Vitro Activity ◽  
In Vitro Susceptibility ◽  
Inhibition Of Growth ◽  
Collection Strain ◽  
Broth Macrodilution

AbstractObjective:To evaluate the in vitro activity of antiseptics and detergents againstCandida.Design:One strain each ofCandida albicans, Candida tropicalis, Candida lusitaniae, Candida parapsilosis, Candida kefyr, Candida glabrata,and an American Type Culture Collection strain ofEscherichia coli(control) were studied. Clinical isolates were obtained from patients in a bone marrow unit of a large tertiary hospital. Antiseptic and disinfectant agents studied were used in the hospital where isolates were identified for cleaning of inanimate surfaces or hand washing. In vitro susceptibility was determined using a broth macrodilution method with exposure times to antiseptic or disinfectant agent of 15 seconds to 4 minutes and concentrations of agents that ranged from undiluted to 1:10,000 dilution.Setting:A 900-bed teaching hospital.Results:Of disinfectants tested, Vestal and Sparquat inhibited growth of all species at dilutions of ≤1:100 at all contact times for all species. Clorox showed inhibition of growth at 1:100 dilution after 30 seconds of contact time for all isolates. Of antiseptics studied, Hibiclens inhibited growth of all species exceptC tropicalisat dilutions of ≤1:100 at all contact times and for Ctropicalisafter 60 seconds. Clinidine inhibited growth of all species at dilutions of ≤1:100 at all contact times for all species with the exception ofC glabrataandC tropicalis,which grew at the undiluted concentration. Ultradex failed to demonstrate killing of any species for any dilutions tested.Conclusions:The results of this study show varying degrees of in vitro inhibition of growth by a variety of antiseptics and disinfectants against clinical isolates ofCandidaspecies from hospitalized patients.

scholarly journals 607. Scope and Predictive Genetic/Phenotypic Signatures of “Bicarbonate [NaHCO3]-Responsivity” and β-Lactam Sensitization among Methicillin-Resistant Staphylococcus aureus (MRSA)

2019 ◽  
Vol 6 (Supplement_2) ◽  
pp. S284-S284
Author(s):  
Selvi Ceren. Ersoy ◽  
Brianne Zapata-Davila ◽  
Mariam Otmishi ◽  
Vanessa Milan ◽  
Liang Li ◽  
...  
Keyword(s):  
Methicillin Resistant Staphylococcus Aureus ◽  
Clonal Complex ◽  
Broth Microdilution ◽  
Standard Medium ◽  
Mueller Hinton ◽  
Solid Foundation ◽  
Mrsa Strains ◽  
Mueller Hinton Broth

Abstract Background Selected MRSA strains become susceptible to β-lactams (e.g., oxacillin [OX]; cefazolin [CFZ]) in vitro when tested in a standard medium (cation-adjusted Mueller–Hinton Broth; CA-MHB) supplemented with NaHCO3 (“NaHCO3-responsivity”). In vivo activity of β-lactams was demonstrated for MRSA strains with this phenotype in a rabbit endocarditis model (Ersoy et al Antimicrob Agents Chemother 2019). The current study was designed to: (i) determine the prevalence of the NaHCO3-responsive phenotype in a large collection of clinical MRSA isolates; and (ii) identify genetic and phenotypic predictors of this phenotype. Methods. 58 recent MRSA bloodstream isolates representing contemporary clonal complex (CC) genotypes were screened for the NaHCO3-responsive phenotype by broth microdilution MICs in CA-MHB, with or without NaHCO3 supplementation (25–44 mM). Methods 58 recent MRSA bloodstream isolates representing contemporary clonal complex (CC) genotypes were screened for the NaHCO3-responsive phenotype by broth microdilution MICs in CA-MHB, with or without NaHCO3 supplementation (25–44 mM). Results 43/58 (74.1%) and 21/58 (36.2%) were rendered susceptible to CFZ and OX, respectively, in the presence of NaHCO3; 20 of the 21 OX-susceptible strains were also susceptible to CFZ in the presence of NaHCO3. High baseline β-lactam MICs (i.e., MICs in CA-MHB alone ≥64 µg/mL) was not predictive of NaHCO3 responsivity. The CC8 genotype was correlated with NaHCO3 responsivity for OX, but not CFZ (P < 0.05). Conclusion The NaHCO3-responsive phenotype is relatively common for both OX and especially CFZ among clinical MRSA isolates. Identification of specific genetic factors linked to this phenotype remains ongoing. Confirmation in relevant animal models that this phenotype is predictive of β-lactam efficacy in vivo could provide a solid foundation for a paradigm shift in antimicrobial susceptibility testing of MRSA. Disclosures All authors: No reported disclosures.

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