Comparative Evaluation of Broth Microdilution with Polystyrene and Glass-Coated Plates, Agar Dilution, E-Test, Vitek, and Disk Diffusion for Susceptibility Testing of Colistin and Polymyxin B on Carbapenem-Resistant Clinical Isolates of Acinetobacter baumannii

2018 ◽  
Vol 24 (8) ◽  
pp. 1082-1088 ◽  
Author(s):  
Lipika Singhal ◽  
Megha Sharma ◽  
Salony Verma ◽  
Ramanpreet Kaur ◽  
Xavier Basil Britto ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Comparative Evaluation ◽  
Susceptibility Testing ◽  
Polymyxin B ◽  
Clinical Isolates ◽  
Disk Diffusion ◽  
Broth Microdilution ◽  
Carbapenem Resistant ◽  
Agar Dilution

scholarly journals Comparative Evaluation of the VITEK 2, Disk Diffusion, Etest, Broth Microdilution, and Agar Dilution Susceptibility Testing Methods for Colistin in Clinical Isolates, Including Heteroresistant Enterobacter cloacae and Acinetobacter baumannii Strains

2007 ◽  
Vol 51 (10) ◽  
pp. 3726-3730 ◽  
Author(s):  
Jerome R. Lo-Ten-Foe ◽  
Anne Marie G. A. de Smet ◽  
Bram M. W. Diederen ◽  
Jan A. J. W. Kluytmans ◽  
Peter H. J. van Keulen
Keyword(s):  
Acinetobacter Baumannii ◽  
Susceptibility Testing ◽  
Enterobacter Cloacae ◽  
Clinical Isolates ◽  
Disk Diffusion ◽  
Broth Microdilution ◽  
Diffusion Test ◽  
Disk Diffusion Test ◽  
Agar Dilution ◽  
Vitek 2

ABSTRACT Increasing antibiotic resistance in gram-negative bacteria has recently renewed interest in colistin as a therapeutic option. The increasing use of colistin necessitates the availability of rapid and reliable methods for colistin susceptibility testing. We compared seven methods of colistin susceptibility testing (disk diffusion, agar dilution on Mueller-Hinton [MH] and Isosensitest agar, Etest on MH and Isosensitest agar, broth microdilution, and VITEK 2) on 102 clinical isolates collected from patient materials during a selective digestive decontamination or selective oral decontamination trial in an intensive-care unit. Disk diffusion is an unreliable method to measure susceptibility to colistin. High error rates and low levels of reproducibility were observed in the disk diffusion test. The colistin Etest, agar dilution, and the VITEK 2 showed a high level of agreement with the broth microdilution reference method. Heteroresistance for colistin was observed in six Enterobacter cloacae isolates and in one Acinetobacter baumannii isolate. This is the first report of heteroresistance to colistin in E. cloacae isolates. Resistance to colistin in these isolates seemed to be induced upon exposure to colistin rather than being caused by stable mutations. Heteroresistant isolates could be detected in the broth microdilution, agar dilution, Etest, or disk diffusion test. The VITEK 2 displayed low sensitivity in the detection of heteroresistant subpopulations of E. cloacae. The VITEK 2 colistin susceptibility test can therefore be considered to be a reliable tool to determine susceptibility to colistin in isolates of genera that are known not to exhibit resistant subpopulations. In isolates of genera known to (occasionally) exhibit heteroresistance, an alternative susceptibility testing method capable of detecting heteroresistance should be used.

scholarly journals Pseudo-Outbreak of Imipenem-Resistant Acinetobacter baumannii Resulting from False Susceptibility Testing by a Rapid Automated System

2000 ◽  
Vol 38 (9) ◽  
pp. 3505-3507 ◽  
Author(s):  
Athanassios Tsakris ◽  
Anastassia Pantazi ◽  
Spyros Pournaras ◽  
Antonios Maniatis ◽  
Aleka Polyzou ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
General Hospital ◽  
Susceptibility Testing ◽  
Homogeneous Group ◽  
Susceptibility Test ◽  
Automated System ◽  
Disk Diffusion ◽  
Broth Microdilution ◽  
High Prevalence ◽  
Agar Dilution

Introduction of the Vitek GNS-506 susceptibility testing cards in the Hippokration General Hospital, Thessaloniki, Greece, resulted in an apparently high prevalence of imipenem-resistant Acinetobacter baumannii. When 35 of these isolates were further tested by disk diffusion, broth microdilution, and agar dilution assays, 32 were imipenem sensitive by all tests and three were sensitive or intermediate, depending on the method. The pseudoresistant acinetobacters did not form a genetically homogeneous group. It is suggested that the detection of imipenem-resistant A. baumannii isolates by this system should be confirmed by an additional susceptibility test.

scholarly journals Comparison of Minocycline Susceptibility Testing Methods for Carbapenem-Resistant Acinetobacter baumannii

2016 ◽  
Vol 54 (12) ◽  
pp. 2937-2941 ◽  
Author(s):  
Peng Wang ◽  
Sarah L. Bowler ◽  
Serena F. Kantz ◽  
Roberta T. Mettus ◽  
Yan Guo ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Susceptibility Testing ◽  
Error Rates ◽  
Disk Diffusion ◽  
Diffusion Method ◽  
Broth Microdilution ◽  
Testing Methods ◽  
Content Type ◽  
Minor Error ◽  
Carbapenem Resistant

Treatment options for infections due to carbapenem-resistantAcinetobacter baumanniiare extremely limited. Minocycline is a semisynthetic tetracycline derivative with activity against this pathogen. This study compared susceptibility testing methods that are used in clinical microbiology laboratories (Etest, disk diffusion, and Sensititre broth microdilution methods) for testing of minocycline, tigecycline, and doxycycline against 107 carbapenem-resistantA. baumanniiclinical isolates. Susceptibility rates determined with the standard broth microdilution method using cation-adjusted Mueller-Hinton (MH) broth were 77.6% for minocycline and 29% for doxycycline, and 92.5% of isolates had tigecycline MICs of ≤2 μg/ml. Using MH agar from BD and Oxoid, susceptibility rates determined with the Etest method were 67.3% and 52.3% for minocycline, 21.5% and 18.7% for doxycycline, and 71% and 29.9% for tigecycline, respectively. With the disk diffusion method using MH agar from BD and Oxoid, susceptibility rates were 82.2% and 72.9% for minocycline and 34.6% and 34.6% for doxycycline, respectively, and rates of MICs of ≤2 μg/ml were 46.7% and 23.4% for tigecycline. In comparison with the standard broth microdilution results, very major rates were low (∼2.8%) for all three drugs across the methods, but major error rates were higher (∼5.6%), especially with the Etest method. For minocycline, minor error rates ranged from 14% to 37.4%. For tigecycline, minor error rates ranged from 6.5% to 69.2%. The majority of minor errors were due to susceptible results being reported as intermediate. For minocycline susceptibility testing of carbapenem-resistantA. baumanniistrains, very major errors are rare, but major and minor errors overcalling strains as intermediate or resistant occur frequently with susceptibility testing methods that are feasible in clinical laboratories.

scholarly journals Comparative evaluation of susceptibility testing methods for colistin and polymyxin B among clinical isolates of carbapenem- resistant Klebsiella pneumoniae and Acinetobacter baumannii

2018 ◽  
Vol 12 (06) ◽  
pp. 504-507 ◽  
Author(s):  
Yamuna Devi Bakthavatchalam ◽  
Abirami Shankar ◽  
Bhuvaneswari Thukaram ◽  
Dhanabhagyam Naveena Krishnan ◽  
Balaji Veeraraghavan
Keyword(s):  
Comparative Evaluation ◽  
Susceptibility Testing ◽  
Reference Method ◽  
Polymyxin B ◽  
Disc Diffusion ◽  
Broth Microdilution ◽  
Testing Methods ◽  
Carbapenem Resistant ◽  
Clinical Laboratories ◽  
Vitek 2

Susceptibility testing (ST) of colistin and polymyxin B is challenging. Disc diffusion testing is not reliable for polymyxin ST, because of poor diffusion. Currently, for polymyxin ST, the EUCAST-CLSI joint commission recommending broth microdilution (BMD) as the reference method.  In this study, reliability of E-test and Vitek 2 was compared with BMD, using the susceptible breakpoint of ≤ 2μg/ml for both colistin and polymyxin B.  Overall, essential agreement (EA) for colistin between E-test, Vitek2 and BMD were 37% and 74% respectively. EA for polymyxin B between E-test and BMD were 65%. Very major error (VME) for colistin and polymyxin B with E-test were 42% and 55% respectively. An unacceptable VME of 11% was seen for colistin with Vitek2. Major errors (MEs) were rather limited with both E-test and Vitek2. E-test and Vitek2 may lead to inappropriate decision-making for colistin/polymyxin B therapy. Thus, clinical laboratories should consider BMD for polymyxin ST.

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.

scholarly journals Comparative Evaluation of Disk Diffusion with Microdilution Assay in Susceptibility Testing of Caspofungin against Aspergillus and Fusarium Isolates

2002 ◽  
Vol 46 (9) ◽  
pp. 3084-3087 ◽  
Author(s):  
Sevtap Arikan ◽  
Victor Paetznick ◽  
John H. Rex
Keyword(s):  
Drug Concentration ◽  
Concentration Gradient ◽  
Comparative Evaluation ◽  
Susceptibility Testing ◽  
Disk Diffusion ◽  
Broth Microdilution

ABSTRACT We compared the disk diffusion and broth microdilution methods for susceptibility testing of caspofungin against Aspergillus (n = 78) and Fusarium (n = 22) isolates. Microdilution testing followed the NCCLS M-38P guidelines but was performed in antibiotic medium 3 supplemented to 2% glucose (AM3). Disk diffusion assays were performed on AM3 agar plates with a 2-μg caspofungin disk. By both methods, caspofungin showed favorable activity against Aspergillus isolates and no activity against Fusarium isolates. In the disk-based format, intrazonal growth that was not influenced by the drug concentration gradient was consistently observed for all of the Aspergillus isolates tested.

scholarly journals Variation in erythromycin and clindamycin susceptibilities of Streptococcus pneumoniae by four test methods.

1997 ◽  
Vol 41 (1) ◽  
pp. 129-134 ◽  
Author(s):  
E L Fasola ◽  
S Bajaksouzian ◽  
P C Appelbaum ◽  
M R Jacobs
Keyword(s):  
Streptococcus Pneumoniae ◽  
Susceptibility Testing ◽  
Ambient Air ◽  
Test Methods ◽  
Disk Diffusion ◽  
Broth Microdilution ◽  
Microdilution Method ◽  
Broth Microdilution Method ◽  
Agar Dilution ◽  
Resistant Strains

Susceptibilities of 124 strains of Streptococcus pneumoniae to erythromycin and clindamycin were determined by the National Committee for the Clinical Laboratory Standards (NCCLS) broth microdilution method, with incubation for 20 to 24 h in ambient air and with modifications of this method by incubation for up to 48 h in air and CO2. Strains were also tested by agar dilution, E-test, and disk diffusion; good correlation was obtained with these methods, with clear separation into bimodal populations of susceptible and resistant stains. The broth microdilution method, however, using incubation in air for 24 h (NCCLS method), misclassified 4 of 92 erythromycin-resistant strains (1 as susceptible and 3 as intermediate) and 25 of 58 clindamycin-resistant strains (all as susceptible). With the exception of one strain with clindamycin, susceptible and resistant strains were correctly classified by the microdilution method with incubation in CO2 for 24 h or in ambient air for 48 h. Disk diffusion, agar dilution, and E-test methods with incubation in 5% CO2 are therefore reliable methods for susceptibility testing of pneumococci against these agents. However, the NCCLS microdilution method, which specifies incubation for 20 to 24 h in ambient air, produced significant very major errors (43%) clindamycin. Modification of the microdilution method by incubation in 5% CO2 or by extension of incubation time in ambient air to 48 h corrected these errors. Disk diffusion, however, was shown to be a simple, convenient, and reliable method for susceptibility testing of pneumococci to erythromycin and clindamycin and is suggested as the method of choice for these agents.

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