Comparison of agar dilution, tube dilution, and broth microdilution susceptibility tests for determination of ramoplanin MICs.

1994 ◽  
Vol 32 (5) ◽  
pp. 1364-1365 ◽  
Author(s):  
M T Kenny ◽  
M A Brackman
Keyword(s):  
Broth Microdilution ◽  
Agar Dilution ◽  
Dilution Tube ◽  
Susceptibility Tests ◽  
Tube Dilution

scholarly journals Quality Control Limits for Dilution and Disk Diffusion Susceptibility Tests of Trovafloxacin against Eight Quality Control Strains

1998 ◽  
Vol 36 (2) ◽  
pp. 585-586
Author(s):  
Peter C. Fuchs ◽  
Arthur L. Barry ◽  
Steven D. Brown
Keyword(s):  
Quality Control ◽  
Disk Diffusion ◽  
Collaborative Effort ◽  
Broth Microdilution ◽  
Agar Dilution ◽  
Susceptibility Tests ◽  
And Control ◽  
Control Limits

A 10-laboratory collaborative effort was designed to generate data to propose quality control limits for susceptibility tests of trovafloxacin. Broth microdilution, agar dilution, and disk diffusion tests were evaluated with eight different control strains. All tests were reproducible, and control limits are proposed.

scholarly journals The accuracy of four commercial broth microdilution tests in the determination of the minimum inhibitory concentration of colistin

2020 ◽  
Vol 19 (1) ◽  
Author(s):  
Erlangga Yusuf ◽  
Mireille van Westreenen ◽  
Wil Goessens ◽  
Peter Croughs
Keyword(s):  
Minimum Inhibitory Concentration ◽  
Antimicrobial Susceptibility ◽  
Inhibitory Concentration ◽  
Clinical Isolates ◽  
Reference Standard ◽  
Broth Microdilution ◽  
Antimicrobial Susceptibility Tests ◽  
Susceptibility Tests ◽  
Composite Reference Standard

Abstract Colistin is considered as one of the last-resort antibiotics and reliable antimicrobial susceptibility testing is therefore crucial. The reference standard for AST according to EUCAST and CLSI is broth microdilution (BMD). However, BMD is labor intensive to perform. Commercial antimicrobial susceptibility tests derived from BMD method are available. We investigated the performance of four different commercial tests: Sensititre™, SensiTest™ Colistin, Micronaut MIC Strip Colistin and UMIC Colistin using 70 clinical isolates (half of them was deemed by VITEK2 as resistant), including isolates from cystic fibrosis patients and mcr-1 bearing isolates. We used two reference standards: BMD and composite MIC as determined by all four tests. Sensititre™ had essential agreement (EA, defined as minimum inhibitory concentration within ± 1 dilution) of 87% and 89% compared to BMD and composite reference standard, respectively. For SensiTest™, the EA’s were 93% and 90%. For UMIC, 87% and 90%, and for Micronaut, 83% and 84%. All four tests demonstrated categorical agreement (CA) above 90%. CA for SensiTest™ and Micronaut was both 96%, UMIC 94%, and Sensititre™ 93%. All tests were reproducible as tested in two quality control isolates. In conclusion, in clinical isolates from a large referral center, the four commercial tests for determination of colistin minimum inhibitory concentrations showed acceptable performance.

Extraction and Phytochemicals Determination of Traditional Medicinal Plants for Anti-microbial Susceptibility Test

2020 ◽  
Vol 2020 ◽  
Author(s):  
Firew Admasu
Keyword(s):  
Antimicrobial Activity ◽  
Medicinal Plants ◽  
Traditional Medicine ◽  
Crude Extract ◽  
Susceptibility Test ◽  
Plant Sample ◽  
Traditional Medicinal Plants ◽  
Traditional Health Care ◽  
Susceptibility Tests

Abstract: The study were conducted at Dilla University, College of Natural Sciences, Biological Sciences laboratories. Background: Ethiopia is a country with many ethnic groups, cultures and beliefs which in turn have contributed to the high diversity of traditional health care knowledge and practices of traditional medicine from local growth plants, animals and minerals for various physical and mental disorders of human and livestock population that passed from generation to generation for centuries. Medicinal plants contributors to pharmaceutical, agricultural and food industries in the world. The use of medicinal plants in the industrialized societies has been traced to extraction and development of several drugs used in order to heel some diseases having inhibiting effect against pathogenic microorganism. Objective: The main objective of this study was Extraction and Phytochemicals determination of traditional medicinal plants for anti microbial susceptibility test. Methodology: The extraction and identification of some phytochemicals crude compound which used for antimicrobial susceptibility test from plant sample such as Ocimum lamiifolium (OL), Croton maerosth (Cm) and Ruta chalepesis (RC) were conducted. Plant samples are collected, powdered using mortal and pistil and extracted using ethanol and some susceptibility tests were performed to identify some phytochemicals compound. Result: The main result of Antimicrobial activity test showed that the crude extract of OL has the highest zone of inhibition. The highest yield of crude extract (38.21%) was obtained from Croton maerosth (CM) which followed by Ruta chalepesis (RC) (32.43%). However, the lowest yield (28.37%) was obtained from Oscpmum lamifolium (OL). Conclusion: Traditional Medicine is used by many people to managing numerous conditions; it’s accessible and effective on antimicrobial activity. Therefore, it plays a significant role by reducing life-threatening ailments of people and other animals.

scholarly journals Detection of Colistin Resistance in Carbapenem Resistant Enterobacteriaceae by Reference Broth Microdilution and Comparative Evaluation of Three Other Methods

2021 ◽  
Author(s):  
Punyatoya Kar ◽  
Bijayini Behera ◽  
Srujana Mohanty ◽  
Jayanti Jena ◽  
Ashoka Mahapatra
Keyword(s):  
Susceptibility Testing ◽  
Good Alternative ◽  
Broth Microdilution ◽  
Major Error ◽  
Colistin Resistance ◽  
Carbapenem Resistant ◽  
Agar Dilution ◽  
Moderate Sensitivity ◽  
Phenotypic Methods ◽  
User Friendly

Abstract Objective Challenges in susceptibility testing of colistin along with increase in the prevalence of colistin-resistant carbapenemase-producing Enterobacteriaceae (CRE) pathogens needs addressal. Evaluation of user-friendly methods is necessary as an alternative to broth microdilution (BMD), the reference susceptibility testing method, for routine implementation in diagnostic clinical microbiology laboratories. Genotypic detection of the plasmid-mediated colistin resistance is also needed for infection control purposes. Materials and Methods Colistin susceptibility of 200 nonduplicate clinical CRE isolates from December 2017 to June 2019 was determined by BMD, agar dilution (AD), E test, and rapid polymyxin NP test and interpreted as per the European Committee on Antimicrobial Susceptibility Testing. The results of AD, E test, and NP test were compared with that of BMD, considering minimal inhibitory concentration (MIC) ≤ 2 µg/mL as susceptible and > 2 µg/mL as resistant. Presence of any plasmid-mediated colistin resistance (mcr-1 and 2) was evaluated in 27 colistin-resistant CRE isolates by polymerase chain reaction. Statistical Analysis Performance of different phenotypic methods was analyzed by comparing MIC results of AD and E test with that of reference BMD method. Agreement between BMD and the other two methods was expressed in terms of categorical agreement and essential agreement. Errors were expressed as very major error (VME: false-susceptible) and major error (ME: false-resistance) by AD/E test. VME and ME of 3% disagreement were considered unacceptable. Results Colistin resistance was found in 27 (13.5%) isolates by BMD method. The VME rates of both AD (11%) and E test (37%) could not meet the Clinical and Laboratory Standards Institute recommendation (< 3% VME rate is acceptable) as alternative tests to the reference BMD. Colistin NP test showed sensitivity and specificity of 85% and 98%, respectively. The percentage discordant result in NP test was highest in Enterobacter spp. (17%). None of the 27 colistin resistant isolates showed presence of mcr-1 and mcr-2 genes. Conclusion High VME rate in AD and E tests precludes their use as alternatives to BMD for colistin susceptibility testing. NP test with moderate sensitivity but excellent specificity can be a good alternative for testing colistin susceptibility in CRE isolates, except in Enterobacter spp. Absence of mcr-1 and mcr-2 gene necessitates the exploration of other mechanisms of colistin resistance.

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

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.

Murepavadin antimicrobial activity against and resistance development in cystic fibrosis Pseudomonas aeruginosa isolates

2020 ◽  
Author(s):  
María Díez-Aguilar ◽  
Marta Hernández-García ◽  
María-Isabel Morosini ◽  
Ad Fluit ◽  
Michael M Tunney ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Antimicrobial Activity ◽  
Spontaneous Mutation ◽  
Lung Surfactant ◽  
Vitro Activity ◽  
In Vitro Activity ◽  
Broth Microdilution ◽  
Agar Dilution

Abstract Background Murepavadin, a novel peptidomimetic antibiotic, is being developed as an inhalation therapy for treatment of Pseudomonas aeruginosa respiratory infection in people with cystic fibrosis (CF). It blocks the activity of the LptD protein in P. aeruginosa causing outer membrane alterations. Objectives To determine the in vitro activity of murepavadin against CF P. aeruginosa isolates and to investigate potential mechanisms of resistance. Methods MIC values were determined by both broth microdilution and agar dilution and results compared. The effect of artificial sputum and lung surfactant on in vitro activity was also measured. Spontaneous mutation frequency was estimated. Bactericidal activity was investigated using time–kill assays. Resistant mutants were studied by WGS. Results The murepavadin MIC50 was 0.125 versus 4 mg/L and the MIC90 was 2 versus 32 mg/L by broth microdilution and agar dilution, respectively. Essential agreement was &gt;90% when determining in vitro activity with artificial sputum or lung surfactant. It was bactericidal at a concentration of 32 mg/L against 95.4% of the strains within 1–5 h. Murepavadin MICs were 2–9 two-fold dilutions higher for the mutant derivatives (0.5 to &gt;16 mg/L) than for the parental strains. Second-step mutants were obtained for the PAO mutS reference strain with an 8×MIC increase. WGS showed mutations in genes involved in LPS biosynthesis (lpxL1, lpxL2, bamA2, lptD, lpxT and msbA). Conclusions Murepavadin characteristics, such as its specific activity against P. aeruginosa, its unique mechanism of action and its strong antimicrobial activity, encourage the further clinical evaluation of this drug.

scholarly journals Antimicrobial Susceptibility of Porphyromonas Gingivalis Strains Isolated From Periodontal Patients by Three Testing Protocols

2020 ◽  
Author(s):  
Lorena Isbej ◽  
Natacha Oyarzo ◽  
María José Contreras ◽  
Duniel Ortuño ◽  
Marusella Lam ◽  
...  
Keyword(s):  
Laboratory Test ◽  
Porphyromonas Gingivalis ◽  
Antimicrobial Susceptibility ◽  
Randomized Clinical Trials ◽  
Blood Agar ◽  
Agar Dilution ◽  
Susceptibility Tests ◽  
High Level ◽  
Testing Protocols

Abstract Background: The main goal of antimicrobials is to eliminate microorganisms that persists despite mechanical treatment. This is the case of Porphyromonas gingivalis (Pg), frequently isolated in patients with periodontitis. Global antibiotic studies evaluated in randomized clinical trials and in vitro studies have shown mixed results regarding effectiveness and susceptibility, even with different protocols where it is not clear if the laboratory test applied can affect the results. This information is relevant in order to obtain clinical outcomes and prevent antimicrobial resistance for their over-prescription or inadequate choice. The objective of this study was to describe the antimicrobial susceptibility in vitro of Pg to metronidazole, clindamycin, amoxicillin plus clavulanate, moxifloxacin and azithromycin in periodontal patients by three testing protocols.Methods: Microbiological samples were obtained in patients with a diagnosis of generalized moderate or severe periodontitis. They were incubated in anaerobic conditions for up to 7 days, and those morphologically compatible with Pg were isolated and identified by a mass spectrometer (MALDI-TOF MS). The three most frequently protocols for antimicrobials susceptibility tests (Blood agar- McFarland 0.5- Epsilometer test; Brucella blood agar- McFarland 1.0- Epsilometer test; Brucella blood agar- McFarland 0.5-Agar dilution) were applied to the same strain describing their profile and reporting any difference between the tests. The breakpoints considered the guidelines of CLSI and previous publications.Results: 50 patients (25 women, 25 men) with periodontitis between 34-69 years were selected. Finally, 25 Pg positives strains (50%) were recovered for the susceptibility analysis and all of them were highly sensitive to all antibiotics (range 96%-100%). Only one strain was resistant to azithromycin in one protocol, and no differences were found in the susceptibility results between the three tests.Conclusion: The Pg strains were highly susceptible to the five antibiotics evaluated in this population, showed a high level of susceptibility and significant agreement between the three tests applied, therefore the type of laboratory test used had not impacted on clinical interpretation. These findings are positives in terms of susceptibility and would provide several antibiotics treatment alternatives, and its prescription could be the best choice for the patient's specific context.

scholarly journals Coherent fluctuation nephelometry in clinical microbiology

2019 ◽  
Vol 9 (2) ◽  
pp. 385-392
Author(s):  
A. S. Gur’ev ◽  
O. Yu. Shalatova ◽  
E. V. Rusanova ◽  
I. V. Vasilenko ◽  
A. Yu. Volkov
Keyword(s):  
Antibiotic Susceptibility ◽  
Clinical Microbiology ◽  
Urine Analysis ◽  
Growth Curves ◽  
High Sensitivity ◽  
Pure Cultures ◽  
Susceptibility Tests ◽  
Express Methods ◽  
Coherent Fluctuation

In this article data concerning coherent fluctuation nephelometry (CFN) use in clinical microbiology is presented. CFN-analyzer allows to solve two important problems – fast urine screening for bacteriuria within 2-4 hours and antibiotic susceptibility testing within 3-6 hours. Altogether more than 650 urine samples were tested, and the effectivity of CFN-analyzer for preliminary selection of samples for further analysis was shown. Method allows to detect negative samples, reducing the number of urine analyses by 70-80%. Simultaneous analysis of growth curves and concentration of microorganisms shows high sensitivity and specificity (95.2% и 96.9%). Also more than 250 antibiotic susceptibility tests were performed using CFN-analyzer to show its effectiveness for determination of resistant properties of both pure cultures and urine microflora without isolation of bacteria. The agreement with traditional methods was from 84% to 88%. The use of CFN-analyzer with express methods of identification of microorganisms (chromogenic nutrient broths or mass-spectrometry) allows to make full urine analysis within 1-2 days. In the future CFN-analyzer gives an opportunity to screen different human biological liquids, and finds an application for other microbiological tasks, including standardization and speeding-up in sanitary bacteriology.

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