Current trends in colistin susceptibility testing methods in enteric Gram-negative bacilli and other non-fermentative pathogens

2021 ◽  
Vol Publish Ahead of Print ◽  
Author(s):  
Khadijeh Najafi ◽  
Leila Yousefi ◽  
Elham Zeinalzadeh ◽  
Hossein Samadi Kafil
Keyword(s):  
Susceptibility Testing ◽  
Testing Methods ◽  
Gram Negative ◽  
Current Trends

scholarly journals Performance of ceftazidime/avibactam susceptibility testing methods against clinically relevant Gram-negative organisms

2018 ◽  
Vol 74 (3) ◽  
pp. 633-638 ◽  
Author(s):  
E Wenzler ◽  
M Lee ◽  
T J Wu ◽  
K A Meyer ◽  
R K Shields ◽  
...  
Keyword(s):  
Susceptibility Testing ◽  
Drug Application ◽  
Error Rates ◽  
Testing Methods ◽  
Suitable Alternative ◽  
Gram Negative ◽  
Treatment Regimens ◽  
Carbapenem Resistant ◽  
Gram Negative Organisms ◽  
New Drug Application

Abstract Objectives To ensure the accuracy of susceptibility testing methods for ceftazidime/avibactam. Methods The performances of the Etest (bioMérieux), 30/20 μg disc (Hardy diagnostics) and 10/4 μg disc (Mast Group) were evaluated against the reference broth microdilution (BMD) method for 102 clinically relevant Gram-negative organisms: 69 ceftazidime- and meropenem-resistant Klebsiella pneumoniae and 33 MDR non-K. pneumoniae. Essential and categorical agreement along with major and very major error rates were determined according to CLSI guidelines. Results A total of 78% of isolates were susceptible to ceftazidime/avibactam. None of the three methods met the defined equivalency threshold against all 102 organisms. The Etest performed the best, with categorical agreement of 95% and major errors of 6.3%. Against the 69 ceftazidime- and meropenem-resistant K. pneumoniae, only the Etest and the 10/4 μg disc met the equivalency threshold. None of the three methods met equivalency for the 33 MDR isolates. There were no very major errors observed in any analysis. These results were pooled with those from a previous study of 74 carbapenem-resistant Enterobacteriaceae and data from the ceftazidime/avibactam new drug application to define optimal 30/20 μg disc thresholds using the error-rate bound model-based approaches of the diffusion breakpoint estimation testing software. This analysis identified a susceptibility threshold of ≤19 mm as optimal. Conclusions Our data indicate that the Etest is a suitable alternative to BMD for testing ceftazidime/avibactam against ceftazidime- and meropenem-resistant K. pneumoniae. The 30/20 μg discs overestimate resistance and may lead to the use of treatment regimens that are more toxic and less effective.

scholarly journals Susceptibility of Multiresistant Gram-Negative Bacteria to Fosfomycin and Performance of Different Susceptibility Testing Methods

2013 ◽  
Vol 58 (3) ◽  
pp. 1763-1767 ◽  
Author(s):  
L. V. Perdigão-Neto ◽  
M. S. Oliveira ◽  
C. F. Rizek ◽  
C. M. D. M. Carrilho ◽  
S. F. Costa ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Klebsiella Pneumoniae ◽  
Susceptibility Testing ◽  
Gram Negative Bacteria ◽  
Testing Methods ◽  
Gram Negative ◽  
Content Type ◽  
Agar Dilution ◽  
And Performance ◽  
Systemic Infections

ABSTRACTFosfomycin may be a treatment option for multiresistant Gram-negative bacteria. This study compared susceptibility methods using 94 multiresistant clinical isolates. With agar dilution (AD), susceptibilities were 81%, 7%, 96%, and 100% (CLSI) and 0%, 0%, 96%, and 30% (EUCAST), respectively, forAcinetobacter baumannii,Pseudomonas aeruginosa,Klebsiella pneumoniae, andEnterobacterspp. Categorical agreement between Etest and AD forEnterobacteriaceaeandA. baumanniiwas ≥80%. Disk diffusion was adequate only forEnterobacter. CLSI criteria for urine may be adequate for systemic infections.

scholarly journals Evaluation of Vitek®2 performance for colistin susceptibility testing for Gram-negative isolates

2020 ◽  
Vol 2 (4) ◽  
Author(s):  
Surbhi Khurana ◽  
Rajesh Malhotra ◽  
Purva Mathur
Keyword(s):  
Susceptibility Testing ◽  
Reference Method ◽  
Trauma Centre ◽  
Gram Negative Bacteria ◽  
Test Results ◽  
Major Error ◽  
Colistin Resistance ◽  
Testing Methods ◽  
Gram Negative ◽  
Unreliable Method

Abstract Background The emerging resistance to the last-resort antimicrobial colistin is being reported globally. Underestimation of the burden of colistin resistance and misinterpretation of colistin susceptibility test results, using suboptimal testing methods, may be causing unexplained treatment failures and even mortality among critically ill patients. Thus, this study was conducted at an apex trauma centre to assess the performance of Vitek®2 for colistin susceptibility testing. Methods A total of 910 clinical isolates of Gram-negative bacteria (GNB), including Enterobacterales, Acinetobacter baumannii and Pseudomonas aeruginosa, were tested and analysed for colistin resistance using Vitek®2. Broth microdilution (BMD) was taken as the reference method. The essential (EA) and categorical (CA) agreements and very major error (VME) and major error (ME) rates were calculated. An MIC correlation was taken to be positive with EA ≥ 90%, CA ≥ 90%, VME ≤ 1.5% and ME ≤ 3.0% rates. Spearman’s coefficient was calculated and P < 0.05 was considered statistically significant. Results A total of 64% of isolates were MDR. Overall, 196 (21.5%) and 110 (12%) of isolates were resistant to colistin by BMD and Vitek®2, respectively. The automated Vitek®2 method failed to detect the resistance in up to 48.5% of GNB tested. When comparing Vitek®2 colistin interpretive results with reference BMD for all 910 isolates, the CA was 88% (798/910) with 10% (95/910) VMEs and 1% (9/910) MEs. Conclusions The Vitek®2 method for colistin susceptibility testing, still in use in some settings; is a suboptimal and unreliable method.

scholarly journals Comparative evaluation of broth microdilution with E-test, Vitek 2, and disk diffusion for susceptibility testing of colistin on Gram-negative bacteria

2021 ◽  
Vol 73 ◽  
pp. 93-98
Author(s):  
Parul Gupta ◽  
Rajni Sharma ◽  
Aruna Vyas ◽  
Amit Tak
Keyword(s):  
Gold Standard ◽  
Susceptibility Testing ◽  
Multidrug Resistant ◽  
Disk Diffusion ◽  
Broth Microdilution ◽  
Testing Methods ◽  
Geometric Means ◽  
Gram Negative ◽  
Vitek 2 ◽  
Good Concordance

Objectives: With the increasing threat of multidrug-resistant organisms, colistin has become popular in clinical practice. A better understanding of antimicrobial susceptibility testing methods for colistin is needed for optimal patient management. The aim of the study was to determine the accuracy of E-test, Vitek 2 system for the detection of colistin minimum inhibitory concentrations (MIC) against broth microdilution (BMD). Material and Methods: A total of 100 isolates of Gram-negative bacilli were subjected to susceptibility testing for colistin using the following methods: BMD, E-test, Vitek 2, and disk diffusion. Using BMD as the gold standard, comparative analysis between different methods was carried out. Results: Comparison of MIC values of E-test (GM = 0.488 mg/ml) against BMD (GM = 0.611 mg/ml using unpaired t-test (t = 2.015, P = 0.045) showed that geometric means of MIC values of E-strip were significantly lower than BMD. Similarly, comparison of MIC values of Vitek 2 system (GM = 0.615 mg/ml) against BMD (GM = 0.611 mg/ml) using unpaired t-test (t = −0.050, P = 0.960) showed no statistical significant differences in geometric means of MIC values. Taking reference as BMD method – the EA for E-strip is 57%, CA is 97%, VME is 2%, and no ME. Similarly, for the Vitek method EA is 64%, CA is 98%, VME is 1%, and ME is 1%. Conclusion: Different susceptibility testing methods for colistin show great variation in their results and BMD is the best candidate as gold standard. The Vitek 2 method showed good concordance with BMD.

scholarly journals Detection of AmpC β Lactamases in Gram-negative Bacteria

2014 ◽  
Vol 6 (01) ◽  
pp. 001-006 ◽  
Author(s):  
Gunjan Gupta ◽  
Vibhor Tak ◽  
Purva Mathur
Keyword(s):  
Susceptibility Testing ◽  
Clinical Laboratory ◽  
Control Point ◽  
Point Of View ◽  
Gram Negative Bacteria ◽  
Disc Diffusion ◽  
Testing Methods ◽  
Gram Negative ◽  
Resistant Phenotype ◽  
Antibiotics Detection

ABSTRACT AmpC β-lactamases are clinically important cephalosporinases encoded on the chromosomes of many Enterobacteriaceae and a few other organisms, where they mediate resistance to cephalothin, cefazolin, cefoxitin, most penicillins, and β-lactamase inhibitor/β-lactam combinations. The increase in antibiotic resistance among Gram-negative bacteria is a notable example of how bacteria can procure, maintain and express new genetic information that can confer resistance to one or several antibiotics. Detection of organisms producing these enzymes can be difficult, because their presence does not always produce a resistant phenotype on conventional disc diffusion or automated susceptibility testing methods. These enzymes are often associated with potentially fatal laboratory reports of false susceptibility to β-lactams phenotypically. With the world-wide increase in the occurrence, types and rate of dissemination of these enzymes, their early detection is critical. AmpC β-lactamases show tremendous variation in geographic distribution. Thus, their accurate detection and characterization are important from epidemiological, clinical, laboratory, and infection control point of view. This document describes the methods for detection for AmpC β-lactamases, which can be adopted by routine diagnostic laboratories.

scholarly journals Comparison of susceptibility testing methods for determining the activity of colistin against Gram-negative bacilli of clinical origin

2019 ◽  
Vol 68 (1) ◽  
pp. 60-66
Author(s):  
Mehri Haeili ◽  
Mahsa Kafshdouz ◽  
Zeinab Pishnian ◽  
Mohammad Mehdi Feizabadi ◽  
Luis Martinez-Martinez
Keyword(s):  
Susceptibility Testing ◽  
Testing Methods ◽  
Gram Negative

scholarly journals Comparing Quantitative and Qualitative Methods for Detecting the In Vitro Activity of Colistin against Different Gram-Negative Bacilli

2021 ◽  
Vol 8 (5) ◽  
Author(s):  
Shams N ◽  
◽  
AlHiraky H ◽  
Moulana N ◽  
Riahi M ◽  
...  
Keyword(s):  
Bacterial Infections ◽  
Susceptibility Testing ◽  
High Sensitivity ◽  
Multidrug Resistant ◽  
Disk Diffusion ◽  
Broth Microdilution ◽  
Testing Methods ◽  
Gram Negative ◽  
Phenotypic Profile

The surge in the prevalence of Multidrug-Resistant (MDR) Gram-negative bacterial infections with limited treatment led to colistin reusing to treat MDR infections. This study aimed to determine economical, simple, and reliable colistin susceptibility testing methods as an alternative to the microdilution technique. We compared seven colistin susceptibility testing methods, including quantitative and qualitative, namely: Disk diffusion, E-test, ComASPTM SensiTest Colistin, Colistin broth disk elution, and colistin agar test CHROMagarTM COL-APSE, and BD Phoenix ID/AST automated identification and susceptibility testing system to the gold standard Broth Microdilution (BMD). Whole-genome sequencing was performed on all isolates to determine if the genetic resistant factors affect the phenotypic profile of the colistin resistance. Our results revealed that disk diffusion is still an ineffective method for measuring colistin susceptibility in Gram-negative Bacilli with the highest major error (31.75%), the lowest Kappa 0 (0%), and categorical agreement (68.25%) values. Phoenix, and CompASPTM SensiTest colistin methods have remained superior in reproducibility, sturdiness, and simplicity of use, similar to the currently recommended broth microdilution procedure; with high sensitivity of 95.56%, and 97.73%, specificity of 95.24, and 100%, and Kappa values of 0.89 and 0.95, respectively. This study revealed that Phoenix, and ComASPTM SensiTest colistin methods are recommended for routine microbiology laboratories with a large workload.

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