Microscopic Analysis of Bacterial Inoculum Effect Using Micropatterned Biochip

Antimicrobial resistance has become a major problem in public health and clinical environments. Against this background, antibiotic susceptibility testing (AST) has become necessary to cure diseases in an appropriate and timely manner as it indicates the necessary concentration of antibiotics. Recently, microfluidic based rapid AST methods using microscopic analysis have been shown to reduce the time needed for the determination of the proper antibiotics. However, owing to the inoculum effect, the accurate measurement of the minimal inhibitory concentration (MIC) is difficult. We tested four standard bacteria: Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Enterococcus faecalis, against five different antibiotics: piperacillin, cefotaxime, amikacin, levofloxacin, and ampicillin. The results showed that overall, the microfluidic system has a similar inoculum effect compared to the conventional AST method. However, due to the different testing conditions and determination protocols of the growth of the microfluidic based rapid AST, a few results are not identical to the conventional methods using optical density. This result suggests that microfluidic based rapid AST methods require further research on the inoculum effect for practical use in hospitals and can then be used for effective antibiotic prescriptions.

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An automated and portable antimicrobial susceptibility testing system for urinary tract infections

Lab on a Chip ◽

10.1039/d0lc01315c ◽

2021 ◽

Vol 21 (4) ◽

pp. 755-763

Author(s):

Kuo-Wei Hsu ◽

Wen-Bin Lee ◽

Huey-Ling You ◽

Mel S. Lee ◽

Gwo-Bin Lee

Keyword(s):

Urinary Tract ◽

Minimum Inhibitory Concentration ◽

Urinary Tract Infections ◽

Antimicrobial Susceptibility ◽

Susceptibility Testing ◽

Inhibitory Concentration ◽

Microfluidic System ◽

Antimicrobial Susceptibility Testing ◽

Testing System ◽

Tract Infections

A portable, integrated microfluidic system capable of automatically conducting antimicrobial susceptibility testing (AST) and minimum inhibitory concentration (MIC) measurements using urine samples were developed.

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The pharmacodynamic inoculum effect from the perspective of bacterial population modeling

10.1101/550368 ◽

2019 ◽

Cited By ~ 1

Author(s):

Desiree Y. Baeder ◽

Roland R. Regoes

Keyword(s):

Competitive Ability ◽

Bacterial Population ◽

Antimicrobial Effect ◽

Inoculum Size ◽

Resistant Bacteria ◽

Bacterial Inoculum ◽

Efficacy Measure ◽

Inoculum Effect

AbstractThe quantitative determination of the effect of antimicrobials is essential for their clinical application, for our microbiological understanding of pharma-codynamics, and for predictive mathematical modeling. It is well-established that the effect of antimicrobials depends on the bacterial inoculum size used in assays — a phenomenon called inoculum effect. The commonly used phar-macodynamic (PD) function that captures the antimicrobial effect, however, is derived from assays conducted with one bacterial inoculum size only. Here, we used the mathematical multi-hit model, which describes antimicrobial action mechanistically, to quantify the effect of the inoculum on the PD parameters. Based on our quantitative analysis, we propose an extended PD function that incorporates the inoculum effect. The extended PD function could mimic the long-term population dynamics for reversibly binding antimicro-bials, but failed when antimicrobials were also assumed to be degraded. We further show that, in simulation with competing antimicrobial-sensitive and -resistant bacteria, neglecting the inoculum effect leads to an overestimation of the competitive ability of the resistant strain. Our work emphasizes that the PD function — and in general any efficacy measure, such as the MIC — should include information about the inoculum size on which it is based, and ideally account for the inoculum effect.

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MICy: a Novel Flow Cytometric Method for Rapid Determination of Minimal Inhibitory Concentration

Microbiology Spectrum ◽

10.1128/spectrum.00901-21 ◽

2021 ◽

Author(s):

András Kállai ◽

Márta Kelemen ◽

Noémi Molnár ◽

Adrienn Tropotei ◽

Balázs Hauser ◽

...

Keyword(s):

Clinical Decision Making ◽

Susceptibility Testing ◽

Inhibitory Concentration ◽

Rapid Determination ◽

Clinical Decision ◽

Flow Cytometric Method ◽

Microdilution Method ◽

Flow Cytometric ◽

Rapid Flow

MICy is a new, simple and rapid flow cytometry based antibiotic susceptibility testing (AST) method that produces susceptibility profile a workday earlier than the microdilution method or other classical phenotypic AST methods. Shortening the length of AST can accelerate clinical decision-making as targeted antibiotic treatment improves clinical outcomes and reduces mortality, duration of artificial ventilation, and length of stay in intensive care unit.

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Time-Kill Kinetics of Rezafungin (CD101) in Vagina-Simulative Medium for Fluconazole-Susceptible and Fluconazole-ResistantCandida albicansand Non-albicans CandidaSpecies

Infectious Diseases in Obstetrics and Gynecology ◽

10.1155/2018/7040498 ◽

2018 ◽

Vol 2018 ◽

pp. 1-10 ◽

Cited By ~ 7

Author(s):

Jeffrey B. Locke ◽

Amanda L. Almaguer ◽

Joanna L. Donatelli ◽

Ken F. Bartizal

Keyword(s):

Antifungal Activity ◽

Fungicidal Activity ◽

Susceptibility Testing ◽

Inhibitory Concentration ◽

The Novel ◽

Testing Conditions ◽

Fluconazole Resistant ◽

Time Kill ◽

Kinetics Of

Background.While echinocandins demonstrate excellent efficacy againstCandidaspecies in disseminated infections and demonstrate potent minimal inhibitory concentration (MIC) values under standard susceptibility testing conditions, investigation under conditions relevant to the vaginal environment was needed. We assessed the antifungal activity and time-kill kinetics of the novel echinocandin rezafungin (formerly CD101) under such conditions, againstCandidaspecies relevant to vulvovaginal candidiasis (VVC).Methods. Susceptibility testing of fluconazole-susceptible and fluconazole-resistantC. albicans,C. glabrata,C. tropicalis,C. parapsilosis, andC. kruseiwas performed in RPMI at pH 7.0 and in vagina-simulative medium (VSM) at pH 4.2 for topical rezafungin, terconazole, fluconazole, and amphotericin B. Time-kill kinetics were evaluated for rezafungin and terconazole at 2, 8, 32, and 128 μg/ml over 72 hours.Results.Rezafungin MIC values were the same or 2-fold higher in VSM/pH 4.2 versus RPMI/pH 7.0. SomeC. albicansterconazole MIC values were lower, but most were significantly higher in VSM than in RPMI. Rezafungin was fungicidal against 11/14 strains and near-fungicidal against the others. Terconazole (128 μg/ml) was fungicidal againstC. kruseiand near-fungicidal against susceptibleC. parapsilosisbut fungistatic versus all other strains evaluated.Conclusion.Rezafungin retained anti-Candidaactivity and fungicidal activity under in vitro conditions relevant to VVC.

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Milk and milk products. Determination of the minimal inhibitory concentration (MIC) of antibiotics applicable to bifidobacteria and non-enterococcal lactic acid bacteria (LAB)

10.3403/30170399 ◽

2010 ◽

Keyword(s):

Lactic Acid ◽

Lactic Acid Bacteria ◽

Minimal Inhibitory Concentration ◽

Inhibitory Concentration ◽

Milk Products

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Changes of some sewage sludge parameters prepared with an ultrasonic field

Water Science & Technology ◽

10.2166/wst.1997.0399 ◽

1997 ◽

Vol 36 (11) ◽

pp. 101-106 ◽

Cited By ~ 15

Author(s):

January Bien ◽

Lidia Wolny

Keyword(s):

Sewage Sludge ◽

Microscopic Analysis ◽

Chemical Compounds ◽

Ultrasonic Field ◽

Water Removal ◽

Vacuum Filter ◽

Additional Criterion ◽

New Methods ◽

Sludge Conditioning

Studies of sewage sludge conditioning by ultrasonic field concentrate on determination of the increase of water removal effect, which depends on kind of sludge and chemical compounds used in the dewatering process. An attempt was made to find new methods of sludge preparation before dewatering. Tests presented here focused on digested and difficult dewatered sludge. The sludge was dewatered on a vacuum filter after conditioning with polyelectrolytes and the ultrasonic field. The microscopic analysis was an additional criterion to evaluate changes in the sludge structure after preparation. The polyelectrolyte dose of 3 mg/g d.m. sonicated within 15 sec. resulted in the 50% decrease of sludge volume. Results presented confirmed our previous experiences, concerning the relation between conglomerates of sludge and the effect of dewatering.

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Evaluation of methods for detection of β-lactamase production in MSSA

Journal of Antimicrobial Chemotherapy ◽

10.1093/jac/dkab032 ◽

2021 ◽

Author(s):

Robert Skov ◽

David R Lonsway ◽

Jesper Larsen ◽

Anders Rhod Larsen ◽

Jurgita Samulioniené ◽

...

Keyword(s):

Susceptibility Testing ◽

Confirmatory Test ◽

Disc Diffusion ◽

Broth Microdilution ◽

Confirmatory Tests ◽

Correct Determination ◽

Primary Test ◽

Zone Edge ◽

Evaluation Of Methods

Abstract Objectives Correct determination of penicillin susceptibility is pivotal for using penicillin in the treatment of Staphylococcus aureus infections. This study examines the performance of MIC determination, disc diffusion and a range of confirmatory tests for detection of penicillin susceptibility in S. aureus. Methods A total of 286 consecutive penicillin-susceptible S. aureus blood culture isolates as well as a challenge set of 62 MSSA isolates were investigated for the presence of the blaZ gene by PCR and subjected to penicillin-susceptibility testing using broth microdilution MIC determination, disc diffusion including reading of the zone edge, two nitrocefin tests and the cloverleaf test. Results Using PCR-based detection of blaZ as the gold standard, both broth microdilution MIC testing and disc diffusion testing resulted in a relatively low accuracy (82%–93%) with a sensitivity ranging from 49%–93%. Among the confirmatory tests, the cloverleaf test performed with 100% accuracy, while zone edge interpretation and nitrocefin-based tests increased the sensitivity of β-lactamase detection to 96%–98% and 82%–96% when using MIC determination or disc diffusion as primary test, respectively. Conclusions This investigation showed that reliable and accurate detection of β-lactamase production in S. aureus can be obtained by MIC determination or penicillin disc diffusion followed by interpretation of the zone edge as a confirmatory test for apparently penicillin-susceptible isolates. The more cumbersome cloverleaf test can also be used. Nitrocefin-based tests should not be used as the only test for confirmation of a presumptive β-lactamase-negative isolate.

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