scholarly journals Detection of AmpC β-lactamases in Escherichia coli using different screening agars

2019 ◽  
Author(s):  
Evert den Drijver ◽  
Jaco J. Verweij ◽  
Carlo Verhulst ◽  
Joke Soer ◽  
Kees Veldman ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Confidence Interval ◽  
Sensitivity And Specificity ◽  
False Positive ◽  
E Coli ◽  
Specificity And Sensitivity ◽  
Positive Results

AbstractThe aim of this study was to determine the performance of both cefotaxime and ceftazidime containing agars on the specificity and sensitivity for chromosomal AmpC-hyperproducing and plasmid AmpC harboring Escherichia coli compared to ESBL-producing E. coli and E. coli without ESBL, pAmpC or cAmpC hyperproduction. Second, we evaluated the influence of adding cefoxitin to these agars for detection of both chromosomal AmpC-hyperproducing and plasmid AmpC harboring E. coli.Four different homemade screening agars with cefotaxime (1mg/L), ceftazidime (1mg/L), cefotaxime (1mg/L) with cefoxitin (8mg/L), and ceftazidime (1mg/L) with cefoxitin (8mg/L) were compared to each other for the identification of AmpC producing E. coli. A total of 40 isolates with plasmid encoded AmpC β-lactamases, 40 isolates with alterations in the promoter/attenuator region of the AmpC gene leading to hyperproduction of the β-lactamase, 40 isolates with ESBL genes and 39 isolates lacking both a AmpC and ESBL genotype were used to test the four agars.The sensitivity and specificity were 100% (95% confidence interval (95% CI) 96.1% to 100%) and 48.1% (95% CI 38.6%-60.2%), respectively, for the cefotaxime agar; 100% (95% CI 96.1% to 100%) and 49.41% (95% CI 39.8%-61.4%), respectively, for the ceftazidime agar; 96.3% (95% CI 89.1% to 99.2%) and 77.2% (95% CI 66.7%-85.2%) respectively, for the cefotaxime with cefoxitin agar; 98.8% (95% CI) 92.6% to 99.6%) and 81.0% (95% CI 70.9%-88.3%) respectively, for the ceftazidime agar with cefoxitin. The main reason for false-positive results were ESBL-harboring strains that grew on various agars; therefore, the specificity of each agar reported here was influenced mainly by the proportion of ESBL isolates tested. In conclusion addition of cefoxitin to cefotaxime and ceftazidime containing agars had little influence on sensitivity, but increased specificity for the detection of AmpC in E. coli.

scholarly journals Modified CIM-Test As a Useful Tool to Detect Carbapenemase Activity Among Extensively Drug- Resistant Klebsiella Pneumoniae, Escherichia Coli and Acinetobacter Baumannii

2021 ◽  
Author(s):  
Abed Zahedi bialvaei ◽  
Alireza Dolatyar Dehkharghani ◽  
Farhad Asgari ◽  
Firouzeh Shamloo ◽  
Parisa Eslami ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Klebsiella Pneumoniae ◽  
Acinetobacter Baumannii ◽  
Sensitivity And Specificity ◽  
E Coli ◽  
Carbapenem Resistant ◽  
Polymerase Chain ◽  
Phenotypic Methods ◽  
Encoding Genes ◽  
Positive Results

Abstract Background Timely detection of carbapenemases is essential for developing strategies to control the spread of infections by carbapenem-resistant isolates. The purpose of our study was to determine the epidemiology of carbapenemase genes among carbapenem resistant isolates of Acinetobacter baumannii, Klebsiella pneumoniae and Escherichia coli and to compare efficacy of modified Hodge Test (MHT), Carba NP and modified carbapenem inactivation method (mCIM) tests. Methods A total of 122 carbapenem-resistant clinical isolates including 77 K. pneumoniae, 39 A. baumannii, and six E. coli were collected from hospitalized patients. Three phenotypic methods, including MHT, Carba NP test and mCIM were used for investigation of carbapenemase production. In addition, polymerase chain reaction (PCR) was performed to detect carbapenemase encoding genes. Results The sensitivity and specificity of the MHT were 75.0% and 100% respectively. In addition, CarbaNP displayed 80.8% sensitivity and 100% specificity, whereas the sensitivity and specificity were 90.4% and 100% for the mCIM test, respectively. Among carbapenem-resistant isolates, 70, 84 and 87 isolates exhibited positive results according to MHT, CarbaNP test and mCIM, respectively. PCR indicated the presence of one or more carbapenemase genes in 119 of carbapenem-resistant isolates, with blaKPC and blaVIM being the most commonly encountered. Co-production of ‘KPC and VIM’, ‘KPC and IMP’ and ‘KPC and OXA-48’ was detected in nine, seven and three isolates, respectively. Conclusion Our results confirm that the mCIM test is a useful tool for the reliable detection of carbapenemases-activity in enterobacterial isolates, especially in clinical microbiological laboratories with limited resources.

scholarly journals Membrane filtration media for the enumeration of coliform organisms and Escherichia coli in water: comparison of Tergitol 7 and lauryl sulphate with Teepol 610

1980 ◽  
Vol 85 (2) ◽  
pp. 181-191 ◽  
Author(s):  
Keyword(s):  
Escherichia Coli ◽  
Water Samples ◽  
False Positive ◽  
Membrane Filtration ◽  
Sodium Lauryl Sulphate ◽  
Standard Medium ◽  
E Coli ◽  
Laboratory Trial ◽  
Positive Results ◽  
Filtration Technique

SUMMARYIn a multi-laboratory trial with the mombrane filtration technique, three surfactants – Teepol 610 (T610), Tergitol 7 (T7) and sodium lauryl sulphate (LS) – were compared in media for the enumeration of coliform organisms and Escherichia coli in water. A total of 170 samples of water (87 raw and 92 marginally chlorinated) were examined for colony counts of coliform organisms, and 185 water samples (94 raw and 91 marginally chlorinated) for E. coli. Slight differences in the confirmed colony counts between the three media were noted, but few of these were observed consistently in every laboratory. In most laboratories, T7 gave slightly higher counts of E. coli than LS with chlorinated waters; a higher incidence of false-positive results for E. coli at 44 °C was also noted with T7. As there were no outstanding differences in the trial, sodium lauryl sulphate, which is chemically defined, cheap and readily available, is therefore recommended for use at a concentration of 0·1% instead of Teepol 610 in the standard medium for the enumeration of coliform organisms and E. coli in water by the membrane filtration technique.

scholarly journals Modified CIM test as a useful tool to detect carbapenemase activity among extensively drug-resistant Klebsiella pneumoniae, Escherichia coli and Acinetobacter baumannii

2021 ◽  
Vol 71 (1) ◽  
Author(s):  
Abed Zahedi Bialvaei ◽  
Alireza Dolatyar Dehkharghani ◽  
Farhad Asgari ◽  
Firouzeh Shamloo ◽  
Parisa Eslami ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Klebsiella Pneumoniae ◽  
Acinetobacter Baumannii ◽  
Sensitivity And Specificity ◽  
E Coli ◽  
Carbapenem Resistant ◽  
Polymerase Chain ◽  
Phenotypic Methods ◽  
Encoding Genes ◽  
Positive Results

Abstract Purpose Timely detection of carbapenemases is essential for developing strategies to control the spread of infections by carbapenem-resistant isolates. The purpose of this study was to determine the epidemiology of carbapenemase genes among carbapenem-resistant isolates of Acinetobacter baumannii, Klebsiella pneumoniae, and Escherichia coli. In addition, the efficacy of the modified Hodge test (MHT), Carba NP test, and modified carbapenem inactivation method (mCIM) were compared. Methods A total of 122 carbapenem-resistant clinical isolates including 77 K. pneumoniae, 39 A. baumannii, and six E. coli were collected from hospitalized patients. Three phenotypic methods, including the MHT, Carba NP test, and mCIM were used for investigation of carbapenemase production. In addition, polymerase chain reaction (PCR) was performed to detect carbapenemase-encoding genes. Result The sensitivity and specificity of the MHT were 75.0% and 100%, respectively. In addition, Carba NP displayed 80.8% sensitivity and 100% specificity, whereas the sensitivity and specificity were 90.4% and 100% for the mCIM test, respectively. Among carbapenem-resistant isolates, 70, 84, and 87 isolates exhibited positive results according to the MHT, Carba NP test, and mCIM, respectively. PCR indicated the presence of one or more carbapenemase genes in 119 of carbapenem-resistant isolates, with blaKPC and blaVIM being the most commonly encountered. Co-production of ‘KPC and OXA-48’, ‘KPC and VIM’, and ‘KPC and IMP’ was detected in three, nine, and seven isolates, respectively. Conclusion Our results confirm that the mCIM test is a useful tool for the reliable detection of carbapenemase activity in enterobacterial isolates, especially in clinical microbiological laboratories with limited resources.

Evaluation of Culture- and PCR-Based Detection Methods for Escherichia coli O157:H7 in Inoculated Ground Beef†

2005 ◽  
Vol 68 (8) ◽  
pp. 1566-1574 ◽  
Author(s):  
TERRANCE M. ARTHUR ◽  
JOSEPH M. BOSILEVAC ◽  
XIANGWU NOU ◽  
MOHAMMAD KOOHMARAIE
Keyword(s):  
Escherichia Coli ◽  
False Positive ◽  
False Negative ◽  
Ground Beef ◽  
Immunomagnetic Separation ◽  
Detection Methods ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Perishable Product ◽  
Specificity And Sensitivity

Currently, several beef processors employ test-and-hold systems for increased quality control of ground beef. In such programs, each lot of product must be tested and found negative for Escherichia coli O157:H7 prior to release of the product into commerce. Optimization of three testing attributes (detection time, specificity, and sensitivity) is critical to the success of such strategies. Because ground beef is a highly perishable product, the testing methodology used must be as rapid as possible. The test also must have a low false-positive result rate so product is not needlessly discarded. False-negative results cannot be tolerated because they would allow contaminated product to be released and potentially cause disease. In this study, two culture-based and three PCR-based methods for detecting E. coli O157:H7 in ground beef were compared for their abilities to meet the above criteria. Ground beef samples were individually spiked with five genetically distinct strains of E. coli O157: H7 at concentrations of 17 and 1.7 CFU/65 g and then subjected to the various testing methodologies. There was no difference (P > 0.05) in the abilities of the PCR-based methods to detect E. coli O157:H7 inoculated in ground beef at 1.7 CFU/65 g. The culture-based systems detected more positive samples than did the PCR-based systems, but the detection times (21 to 48 h) were at least 9 h longer than those for the PCR-based methods (7.5 to 12 h). Ground beef samples were also spiked with potentially cross-reactive strains. The PCR-based systems that employed an immunomagnetic separation step prior to detection produced fewer false-positive results.

scholarly journals Marine Bacteria Cause False-Positive Results in the Colilert-18 Rapid Identification Test for Escherichia coli in Florida Waters

2002 ◽  
Vol 68 (2) ◽  
pp. 539-544 ◽  
Author(s):  
John M. Pisciotta ◽  
Damon F. Rath ◽  
Paul A. Stanek ◽  
D. Michael Flanery ◽  
Valerie J. Harwood
Keyword(s):  
Escherichia Coli ◽  
False Positive ◽  
Fecal Coliform ◽  
Membrane Filtration ◽  
False Positives ◽  
Fecal Coliforms ◽  
Marine Waters ◽  
E Coli ◽  
Marine Samples ◽  
Positive Results

ABSTRACT The Colilert-18 system for enumeration of total coliforms and Escherichia coli is approved by the U.S. Environmental Protection Agency for use in drinking water analysis and is also used by various agencies and research studies for enumeration of indicator organisms in fresh and saline waters. During monitoring of Pinellas County, Fla., marine waters, estimates of E. coli numbers (by Colilert-18) frequently exceeded fecal coliform counts (by membrane filtration) by 1 to 3 orders of magnitude. Samples from freshwater sites did not display similar discrepancies. Fecal coliforms, including E. coli, could be cultured from 100% of yellow fluorescent wells (denoting E. coli-positive results) inoculated with freshwater samples but could be cultured from only 17.1% of the “positive” wells inoculated with marine samples. Ortho-nitrophenyl-β-d-galactopyranoside (ONPG)-positive or 4-methylumbelliferyl-β-d-glucuronide (MUG)-positive noncoliform bacteria were readily cultured from Colilert-18 test wells inoculated with marine samples. Filtered cell-free seawater did not cause false positives. Coculture preparations of as few as 5 CFU of Vibrio cholerae (ONPG positive) and Providencia sp. (MUG positive) ml−1 inoculated into Colilert-18 caused false-positive E. coli results. Salinity conditions influenced coculture results, as the concentration of coculture inoculum required to cause false positives in most wells increased from about 5 CFU ml−1 in seawater diluted 1:10 with freshwater to ≈5,000 CFU ml−1 in seawater diluted 1:20 with freshwater. Estimated E. coli numbers in various marine water samples processed at the 1:10 dilution ranged from 10 to 7,270 CFU�100 ml−1, while E. coli numbers in the same samples processed at the 1:20 dilution did not exceed 40 CFU�100 ml−1. The lower estimates of E. coli numbers corresponded well with fecal coliform counts by membrane filtration. This study indicates that assessment of E. coli in subtropical marine waters by Colilert-18 is not accurate when the recommended 1:10 sample dilution is used. The results suggest that greater dilution may diminish the false-positive problem, but further study of this possibility is recommended.

Characterization of O157:H7 and Other Escherichia coli Isolates Recovered from Cattle Hides, Feces, and Carcasses†

2004 ◽  
Vol 67 (5) ◽  
pp. 993-998 ◽  
Author(s):  
GENEVIEVE A. BARKOCY-GALLAGHER ◽  
TERRANCE M. ARTHUR ◽  
MILDRED RIVERA-BETANCOURT ◽  
XIANGWU NOU ◽  
STEVEN D. SHACKELFORD ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Seasonal Variations ◽  
False Positive ◽  
Significant Trend ◽  
Escherichia Coli O157 ◽  
Seasonal Prevalence ◽  
E Coli ◽  
Beef Processing ◽  
Positive Results

In a previous study, the seasonal prevalence was reported for stx+ Escherichia coli O157:H7 in feces and on hides and carcasses of cattle at processing. Overall, 1,697 O157:H7 isolates have now been characterized for the incidence of (i) eaeO157, hlyA, stx1, and stx2 in the recovered isolates and (ii) presumptive rough and presumptive nonmotile isolates. Seven O157:H7 isolates (0.4%) lacked stx genes, although they carried eae and hlyA. All but one of the isolates carried both eae and hlyA. Approximately two-thirds of the isolates (64% when one isolate per sample was considered) carried both stx1 and stx2. E. coli O157:H7 cells that harbored both stx1 and stx2 were more often recovered from hides in the fall (79% of the fall hide isolates) and winter (84% of the winter hide isolates) than in the spring (53%) and summer (59%). Isolates recovered from preevisceration carcasses showed a similar but not statistically significant trend. Twenty-three of the 25 O157:H7 isolates carrying stx1 but not stx2 were recovered during summer. Fifteen presumptive rough and 117 presumptive nonmotile stx+ O157:H7 isolates were recovered. Ten (67%) of the presumptive rough isolates were recovered during summer. Ninety-five of the presumptive nonmotile isolates (81%) were recovered during fall. Forty-eight percent of the false-positive isolates (175 of 363) tentatively identified as O157:H7 were O157+ H7− and lacked eaeO157, hlyA, and stx. These data suggest that in beef processing samples (i) there are minor seasonal variations in the prevalence of stx genes among E. coli O157:H7 isolates, (ii) presumptive rough and presumptive nonmotile stx+ O157:H7 isolates are present, (iii) E. coli O157:H7 isolates lacking stx genes may be rare, and (iv) O157+ H7− isolates lacking stx genes can result in many false-positive results.

Comparison of colony and stool blots for detection of enteropathogens by DNA probes

1991 ◽  
Vol 37 (5) ◽  
pp. 407-410
Author(s):  
Mônica A. M. Vieira ◽  
Beatriz E. C. Guth ◽  
Tânia A. T. Gomes
Keyword(s):  
Escherichia Coli ◽  
Key Words ◽  
Sensitivity And Specificity ◽  
Dna Probes ◽  
Type I ◽  
Enteropathogenic Escherichia Coli ◽  
Key Words Dna ◽  
E Coli ◽  
Heat Stable

DNA probes that identify genes coding for heat-labile type I (LT-I) and heat-stable type 1 (ST-I) enterotoxins, enteropathogenic Escherichia coli adherence factor (EAF), and Shigella-like, invasiveness (INV) are used to evaluate the sensitivity and specificity of stool blots in comparison with the sensitivity and specificity of colony blots in detecting enteropathoghens. The sensitivities of the probes in stool blots are 91.7% for the LT-I probe, 76.9% for the ST-I probes, 78.9% for the EAF probe, and 45.5% for the INV probe. The specificity of all probes is higher than 95%. In general, the stool blot method identifies as many if not more LT-I-, ST-I-, and EAF-producing E. coli infections than the colony blots. Key words: DNA probes, stool blots, enteropathogens, diagnosis.

scholarly journals A comparison of ten USEPA approved total coliform/E. coli tests

2007 ◽  
Vol 5 (2) ◽  
pp. 267-282 ◽  
Author(s):  
Jeremy Olstadt ◽  
James Jay Schauer ◽  
Jon Standridge ◽  
Sharon Kluender
Keyword(s):  
Environmental Protection Agency ◽  
False Positive ◽  
The United States ◽  
Total Coliform ◽  
Test System ◽  
E Coli ◽  
Test Systems ◽  
High Concentrations ◽  
Different Strains ◽  
Positive Results

Since 2002, the United States Environmental Protection Agency (USEPA) has approved ten enzyme-based total coliform and E. coli detection tests for examination of drinking water. These tests include: Colilert®, Colilert-18®, Colisure®, m-Coli Blue 24®, Readycult® Coliforms 100, Chromocult®, Coliscan®, E*Colite®, Colitag™ and MI Agar. The utility of the enzyme based test systems is based on both the ability of the test to detect the target organisms at low levels and the ability of the test system to suppress the growth of non-target organisms that might result in false positive results. Differences in the ability of some of these methods to detect total coliform and E. coli, as well as suppress Aeromonas spp., a common cause of “false positive” results, have been observed. As a result, this study was undertaken to elucidate the strengths and weaknesses of each method. Water samples were collected from three geographically and chemically diverse groundwaters in Wisconsin. One-hundred milliliter aliquots were individually spiked with both low concentrations (one to ten organisms) and high concentrations (fifty to one-hundred) of each of five different total coliform organisms (Serratia, Citrobacter, Enterobacter, E. coli, & Klebsiella). These spiked samples were used to test the capability of ten enzyme-based test systems to both detect and enumerate the spiked organisms. In addition, 100 ml samples were independently spiked with two different strains of Aeromonas spp. at six different levels, to assess the ability of each enzyme-based test to suppress Aeromonas spp. Analysis of the data indicated that wide variability exists among USEPA approved tests to detect and quantify total coliforms, as well as suppress Aeromonas spp.

scholarly journals National Prevalence of Resistance to Third-Generation Cephalosporins in Escherichia coli Isolates from Layer Flocks in France

2013 ◽  
Vol 57 (12) ◽  
pp. 6351-6353 ◽  
Author(s):  
Claire Chauvin ◽  
Laetitia Le Devendec ◽  
Eric Jouy ◽  
Maena Le Cornec ◽  
Sylvie Francart ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Confidence Interval ◽  
Egg Production ◽  
Generation Cephalosporin ◽  
Gene Control ◽  
Third Generation ◽  
Content Type ◽  
E Coli ◽  
National Prevalence ◽  
Third Generation Cephalosporins

ABSTRACTResistance ofEscherichia colito third-generation cephalosporin (3GC) in fecal samples representative of French egg production was studied. The susceptibility to cefotaxime ofE. coliisolates obtained by culture on nonselective media was determined. Twenty-two nonsusceptible isolates were obtained (7.51%; 95% confidence interval, 4.49 to 10.54%), the majority of which came from young birds. Most isolates carried ablaCTX-M-1group gene, and a few carried ablaCMY-2-like gene. Control of 3GC resistance in laying hens is needed.

Specific Identification of Escherichia coli O157 by an Immunostick Method Using Commercially Available Antibodies

1996 ◽  
Vol 59 (6) ◽  
pp. 670-673 ◽  
Author(s):  
SHIU W. HUANG ◽  
TSUNG C. CHANG
Keyword(s):  
Escherichia Coli ◽  
Rapid Identification ◽  
Escherichia Coli O157 ◽  
Commercial Preparation ◽  
E Coli ◽  
Specificity And Sensitivity ◽  
Sandwich Enzyme Immunoassay ◽  
Antigen Antibody ◽  
Phosphate Buffered Saline ◽  
Somatic Antigens

A sandwich enzyme-immunoassay performed on plastic sticks was developed to specifically identify Escherichia coli O157. Colonies of test bacteria grown on tryptic soy agar were suspended in phosphate-buffered saline, heated in a 100°C water bath for 15 min, and incubated with the plastic sticks coated with a commercial preparation of anti-E. coli O157 antibodies at 37°C for 1.5 h. After incubation, the same antibodies labeled with peroxidase were used to produce the signal of antigen-antibody reaction. For 35 strains of E. coli O157 (among them 34 were E. coli O157:H7) tested, all produced strong reactions by the immunoassay. For 162 strains of E. coli with somatic antigens other than O157 and 38 strains of other genera tested, only one strain (Salmonella bietri) produced a false-positive reaction. The specificity and sensitivity of the immunostick assay were 100% (35/35) and 99.5% (199/200), respectively. The detection limit of the assay for E. coli O157:H7 (CCRC 15991) was about 105 CFU/ml. The method, which can be carried out within 3 h, is useful for rapid identification of suspect E. coli O157 isolated on selective media.

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