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 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 Detection and Reporting of Organisms Producing Extended-Spectrum β-Lactamases: Survey of Laboratories in Connecticut

1999 ◽  
Vol 37 (12) ◽  
pp. 4065-4070 ◽  
Author(s):  
Fred C. Tenover ◽  
M. Jasmine Mohammed ◽  
Timothy S. Gorton ◽  
Zygmunt F. Dembek
Keyword(s):  
Antimicrobial Agents ◽  
Susceptibility Testing ◽  
Clinical Laboratory ◽  
Test Organism ◽  
National Committee ◽  
Control Strain ◽  
Testing Methods ◽  
Gram Negative ◽  
Extended Spectrum ◽  
Esbl Producers

Extended-spectrum β-lactamases (ESBLs) are enzymes produced in some gram-negative bacilli that mediate resistance to extended-spectrum cephalosporins and aztreonam. They are most common inKlebsiella spp. and Escherichia coli but are present in a variety of Enterobacteriaceae. Resistance mediated by these enzymes can be difficult to detect depending on the antimicrobial agents tested. AmpC β-lactamases are related to the chromosomal enzymes of Enterobacter andCitrobacter spp. and also mediate resistance to extended-spectrum cephalosporins and aztreonam in addition to cephamycins, such as cefoxitin. Unlike ESBLs, however, AmpC β-lactamases are not inhibited by clavulanic acid or other similar compounds. To assess the abilities of various antimicrobial susceptibility testing methods to detect ESBLs, we sent three ESBL-producing organisms, one AmpC-producing organism, and a control strain that was susceptible to extended-spectrum cephalosporins to 38 laboratories in Connecticut for testing. Eight (21.0%) of 38 labs failed to detect extended-spectrum cephalosporin or aztreonam resistance in any of the ESBL- or AmpC-producing isolates. Errors were encountered with both automated and disk diffusion methods. Conversely, seven (18.4%) labs categorized at least some of the four resistant isolates as potential ESBL producers and reported the results with the extended-spectrum cephalosporins and aztreonam as resistant as suggested by current National Committee for Clinical Laboratory Standards (NCCLS) guidelines. The percentage of laboratories that failed to detect resistance in the ESBL or AmpC isolates ranged from 23.7 to 31.6% depending on the type of enzyme present in the test organism. This survey suggests that many laboratories have difficulty detecting resistance in ESBL and AmpC-producing organisms and may be unaware of the NCCLS guidelines on modifying susceptibility testing reports for ESBL-producing strains.

In-vitro Antioxidant and Antibacterial Activity of Methanolic Extract of Shorea robusta Gaertn. F. Resin

2016 ◽  
Vol 6 (4) ◽  
pp. 68
Author(s):  
Sushma Vashisht ◽  
Manish Pal Singh ◽  
Viney Chawla
Keyword(s):  
Antibacterial Activity ◽  
Methanolic Extract ◽  
Diffusion Method ◽  
Gram Negative Bacteria ◽  
Disc Diffusion ◽  
Gram Positive ◽  
Gram Negative ◽  
Shorea Robusta ◽  
Dose Dependent ◽  
Resin Extract

The methanolic extract of the resin of Shorea robusta was subjected to investigate its antioxidant and antibacterial properties its utility in free radical mediated diseases including diabetic, cardiovascular, cancer etc. The methanol extract of the resin was tested for antioxidant activity using scavenging activity of DPPH (1,1-diphenyl-2-picrylhydrazil) radical method, reducing power by FeCl3 and antibacterial activity against gram positive and gram negative bacteria using disc diffusion method. The phytochemical screening considered the presence of triterpenoids, tannins and flavoniods. Overall, the plant extract is a source of natural antioxidants which might be helpful in preventing the progress of various oxidative stress mediated diseases including aging. The half inhibition concentration (IC50) of resin extract of Shorea robusta and ascorbic acid were 35.60 µg/ml and 31.91 µg/ml respectively. The resin extract exhibit a significant dose dependent inhibition of DPPH activity. Antibacterial activity was observed against gram positive and gram negative bacteria in dose dependent manner.Key Words: Shorea robusta, antioxidant, antibacterial, Disc-diffusion, DPPH.

scholarly journals Enaminone-Derived Pyrazoles with Antimicrobial Activity

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Mashooq Ahmad Bhat ◽  
Mohamed A. Al-Omar ◽  
Ahmed M. Naglah ◽  
Abdul Arif Khan
Keyword(s):  
Antimicrobial Activity ◽  
Gram Negative Bacteria ◽  
Significant Activity ◽  
Disc Diffusion ◽  
Initial Screening ◽  
Gram Positive ◽  
Gram Negative ◽  
Disc Diffusion Assay ◽  
Gram Positive Bacteria ◽  
Diffusion Assay

A series of pyrazoles derived from the substituted enaminones were synthesized and were evaluated for antimicrobial activity. All the compounds were characterized by the spectral data and elemental analysis. The synthesized compounds were initially screened for their antimicrobial activity against ATCC 6538, NCTC 10400, NCTC 10418, and ATCC 27853. During initial screening, compounds (P1, P6, and P11) presented significant antimicrobial activity through disc diffusion assay. These compounds were further evaluated for antimicrobial activity at different time points against Gram-positive and Gram-negative bacteria and presented significant activity for 6 hours. The activity was found to be greater against Gram-positive bacteria. In contrast at 24 hours, the activity was found only against Gram-positive bacteria except compound (P11), showing activity against both types of bacteria. Compound (P11) was found to have highest activity against both Gram-positive and Gram-negative bacteria.

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 “ISOLATION AND CHARACTERIZATION OF LACTOSE AND NON- LACTOSE FERMENTING BACTERIA FROM TERTIARY CARE HOSPITAL AND THEIR ANTIMICROBIAL SUSCEPTIBILITY TEST”

2017 ◽  
Vol 10 (2) ◽  
pp. 201
Author(s):  
Kumud Bala ◽  
Ridhima Wadhwa ◽  
Rachana Bohra
Keyword(s):  
Tertiary Care Hospital ◽  
Tertiary Care ◽  
Susceptibility Test ◽  
Diffusion Method ◽  
Gram Negative Bacteria ◽  
Care Hospital ◽  
Disc Diffusion ◽  
Gram Negative ◽  
Fermenting Bacteria ◽  
Vitek 2

Objective: The purpose of the present study was to identify the fermenting and non-fermenting gram negative bacteria from the tertiary care hospital.Methods: The conventional method of identification by biochemical analysis and antibiotic susceptibility test was performed by Kirby-Bauer disc diffusion method. Furthermore, analysis of microbes was done by Vitek-2.Results: 424strains of lactose fermenting and non-lactose fermenting gram negative bacilli were isolated from 3097 clinical samples. From the total lactose fermenting bacteria Escherichia coli was the predominant isolate accounting for 50.94% specimens, followed by Klebsiella pneumonia 27.59% and Enterobacter 0.47%. From the total non-lactose fermenting gram negative bacilli Acinetobacter baumannii was the predominant isolate accounting for 12.73% specimens followed by Pseudomonas aeroginosa 6.13%, other isolates were Stenotrophomonas maltophilia 1.17% , Burkholderia cepacia 0.94%. In the present study male were more infected than female. The study also showed that lactose fermenting bacteria were more infectious than non lactose-fermenting bacteria and isolates were from urine samples.Conclusion: Both Non-Lactose Fermenting Gram Negative Bacilli and Lactose Fermenting Gram Negative Bacilli were found to be major contaminants, and are important pathogenic bacteria causing wide range of infections in the tertiary care hospital.Keywords: Lactose fermenting gram negative bacteria, Vitek-2, Tertiary Care Hospital, Kirby-Bauer Disc Diffusion, Lactose non-fermenting gram negative bacteria  

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