Performance of Rapid Polymyxin™ NP and Rapid Polymyxin™ Acinetobacter for the detection of polymyxin resistance in carbapenem-resistant Acinetobacter baumannii and Enterobacterales

Abstract Background The global spread of carbapenem-resistant Enterobacterales (CRE) and Acinetobacter baumannii (CRAB) has prompted the reintroduction of colistin as a last-resort treatment. Although the recommended method for colistin susceptibility testing is broth microdilution (BMD), methods that are more rapid and easy to use are needed. Objectives To evaluate the performance of two commercial kits for colistin susceptibility testing: Rapid Polymyxin™ NP (RP-NP) for CRE and Rapid Polymyxin™ Acinetobacter (RP-AB) for CRAB. Methods A total of 76 CRE and 87 CRAB isolates were collected from hospitalized patients in Europe and Israel. The isolates were subcultured twice on 5% sheep blood in tryptic soy agar. We tested colistin susceptibility using the RP-NP and RP-AB kits and compared the results with those from BMD. Results Of the CRE isolates, 25% (19/76) were resistant to colistin using BMD. Categorical agreement between RP-NP and BMD was 93.4% (71/76), major errors 1.8% (1/57) and very major errors 21.1% (4/19). Sensitivity was 78.9% and specificity was 98.2%. Of the CRAB isolates, 58.6% (51/87) were resistant to colistin by BMD. Categorical agreement between RP-AB and BMD was 59.8% (52/87), major errors 13.9% (5/36) and very major errors 58.8% (30/51). Sensitivity of RP-AB was 41.2% and specificity was 86.1%. Conclusions In many of the tested isolates, weak or inconclusive colour changes in the test wells caused difficulty in interpretation, resulting in an unacceptable rate of very major errors.

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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

Microbial Drug Resistance ◽

10.1089/mdr.2017.0251 ◽

2018 ◽

Vol 24 (8) ◽

pp. 1082-1088 ◽

Cited By ~ 12

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

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Tigecycline susceptibility of multidrug-resistant Acinetobacter baumannii from intensive care units in the western Balkans

Acta Microbiologica et Immunologica Hungarica ◽

10.1556/030.2020.01079 ◽

2020 ◽

Vol 67 (3) ◽

pp. 176-181

Author(s):

Ina Gajic ◽

Lazar Ranin ◽

Dusan Kekic ◽

Natasa Opavski ◽

Aleksandra Smitran ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Susceptibility Testing ◽

Multidrug Resistant ◽

Inappropriate Therapy ◽

Antibiotic Susceptibility Testing ◽

Broth Microdilution ◽

Western Balkans ◽

Colistin Resistance ◽

European Committee ◽

Carbapenem Resistant

AbstractTigecycline can be effective to treat infections of carbapenem-resistant Acinetobacter baumannii (CRAB) however, no interpretive criteria have been approved so far. The objectives of this study were to evaluate the proportion of CRAB isolates and to compare gradient test with a broth microdilution (BMD) method for tigecycline susceptibility testing of A. baumannii.This study included 349 multidrug-resistant (MDR) Acinetobacter spp. collected from Serbia, Montenegro, Bosnia and Herzegovina in 2016 and 2017. Antibiotic susceptibility testing was performed by disk diffusion, VITEK2, gradient, ComASP Colistin. Tigecycline susceptibilities were interpreted according to breakpoints of European Committee on Antimicrobial Susceptibility Testing (EUCAST) and Food and Drug Administration (FDA).Majority of the tested isolates were CRAB (92.8%). Tigecycline MIC50/MIC90 values were 4/8 μg/mL by BMD and 0.5/4 μg/mL by gradient test. Essential agreement for BMD and gradient test amounted to 65.1%. With EUCAST breakpoints, categorical agreement (CA) was achieved in 38% isolates. Major discordance (MD-false susceptibility/resistance) and minor discordance (mD-false categorization involving intermediate results) were observed in 10% and 57% A. baumannii, respectively. With FDA breakpoints, CA, MD and mD were observed in 44%, 16% and 47% isolates, respectively. Colistin resistance was 2.1%.The study highlights a high proportion of CRAB and several discordances between BMD and gradient test which may lead to inappropriate therapy.

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

Journal of Clinical Microbiology ◽

10.1128/jcm.01810-16 ◽

2016 ◽

Vol 54 (12) ◽

pp. 2937-2941 ◽

Cited By ~ 10

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.

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Evaluation of the MICRONAUT MIC-Strip Colistin assay for colistin susceptibility testing of carbapenem-resistant Acinetobacter baumannii and Enterobacterales

Diagnostic Microbiology and Infectious Disease ◽

10.1016/j.diagmicrobio.2021.115391 ◽

2021 ◽

pp. 115391

Author(s):

Hadas Kon ◽

Maayan Amar Ben Dalak ◽

David Schwartz ◽

Yehuda Carmeli ◽

Jonathan Lellouche

Keyword(s):

Acinetobacter Baumannii ◽

Susceptibility Testing ◽

Carbapenem Resistant

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

Journal of Laboratory Physicians ◽

10.1055/s-0041-1731137 ◽

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.

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Antimicrobial resistance profiles and oxacillinase genes in carbapenem-resistant Acinetobacter baumannii isolated from hospitalized patients in Santa Catarina, Brazil

Revista da Sociedade Brasileira de Medicina Tropical ◽

10.1590/0037-8682-0233-2015 ◽

2015 ◽

Vol 48 (6) ◽

pp. 699-705 ◽

Cited By ~ 5

Author(s):

Giselle Dall Cortivo ◽

Andréia Gutberlet ◽

Jéssica Augustini Ferreira ◽

Leslie Ecker Ferreira ◽

Roseneide Campos Deglmann ◽

...

Keyword(s):

Antimicrobial Resistance ◽

Acinetobacter Baumannii ◽

Hospitalized Patients ◽

Santa Catarina ◽

Carbapenem Resistant

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Characterization of carbapenem-resistant Acinetobacter baumannii strains isolated from hospitalized patients in Palestine

Antimicrobial Resistance and Infection Control ◽

10.1186/2047-2994-4-s1-p136 ◽

2015 ◽

Vol 4 (Suppl 1) ◽

pp. P136

Author(s):

R Handal ◽

L Qunibi ◽

I Sahouri ◽

M Juhari ◽

H Marzouqa ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Hospitalized Patients ◽

Carbapenem Resistant

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Clinical Validation of SensiTest Colistin, a Broth Microdilution-Based Method To Evaluate Colistin MICs

Journal of Clinical Microbiology ◽

10.1128/jcm.01523-17 ◽

2018 ◽

Vol 56 (4) ◽

Cited By ~ 16

Author(s):

Edoardo Carretto ◽

Flavia Brovarone ◽

Giuseppe Russello ◽

Paola Nardini ◽

Maisra M. El-Bouseary ◽

...

Keyword(s):

Room Temperature ◽

Susceptibility Testing ◽

Reference Method ◽

Multidrug Resistant ◽

Clinical Validation ◽

Gram Negative Bacteria ◽

Broth Microdilution ◽

Bacterial Strains ◽

Global Spread ◽

Severe Infections

ABSTRACT The global spread of multidrug-resistant Gram-negative bacteria has led to the return of colistin for treating severe infections. Recently, different plasmid-mediated genes conferring resistance to this drug were described and reported worldwide. International committees (EUCAST/CLSI) reevaluated inconsistencies surrounding colistin antimicrobial susceptibility testing (AST), concluding that broth microdilution (BMD) should serve as the reference method for AST. The development of an accurate, reproducible commercial test based on BMD is therefore highly desirable. SensiTest Colistin (STC), a BMD-based compact 4-test panel containing the lyophilized antibiotic in 7 2-fold dilutions (0.25 to 16 μg/ml) was here compared with the EUCAST-CLSI standard reference method (BMD) and, for some isolates, with the automated Phoenix 100 system (PHX). A total of 353 bacterial strains were evaluated by two different laboratories; 137 isolates were resistant to colistin (19 were intrinsically resistant, 83 harbored the mcr-1 gene). Essential agreement (EA) between STC and BMD was obtained for 339 out of the 353 strains tested (96.0%). Overall categorical agreement was obtained for 349 out of the 353 strains analyzed (98.9%). Two major errors (MEs; 0.93%) and two very major errors (VMEs; 1.46%) were documented. STC appeared to be a simple but highly reliable test with good reproducibility even with panels stored at room temperature or at 35°C. Moreover, STC showed a good performance with strains carrying the mcr-1 gene, with a 98.8% EA. As the secondary endpoint of our study, VMEs for PHX were documented for 6 isolates (10%).

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