scholarly journals Beta-lactams susceptibility testing of penicillin-resistant, ampicillin-susceptible Enterococcus faecalis isolates: a comparative assessment of Etest and disk diffusion methods against broth dilution

2020 ◽  
Vol 19 (1) ◽  
Author(s):  
Natália Conceição ◽  
Wellington Francisco Rodrigues ◽  
Kessys Lorrânya Peralta de Oliveira ◽  
Lucas Emanuel Pinheiro da Silva ◽  
Laís Rezende Cardoso de Souza ◽  
...  
Keyword(s):  
Enterococcus Faecalis ◽  
Reference Method ◽  
Poor Performance ◽  
Accurate Method ◽  
Disk Diffusion ◽  
Beta Lactam ◽  
Beta Lactams ◽  
Antimicrobial Susceptibility Tests ◽  
Susceptibility Tests ◽  
Broth Dilution

Abstract This study aimed to evaluate the accuracy of disk diffusion and Etest methods, compared to that of the broth dilution reference method for identifying beta-lactam susceptibilities of Penicillin-Resistant, Ampicillin-Susceptible Enterococcus faecalis (PRASEF) isolates. Fifty-nine PRASEF and 15 Penicillin-Susceptible, Ampicillin-Susceptible E. faecalis (PSASEF) clinical nonrepetitive isolates were evaluated. The effectiveness of five beta-lactams (ampicillin, amoxicillin, imipenem, penicillin, and piperacillin) was tested. All antimicrobial susceptibility tests were performed and interpreted according to the Clinical and Laboratory Standards Institute guidelines. Interpretative discrepancies, such as essential agreement, categorical agreement, and errors, were assessed. The acceptability was ≥ 90% for both categorical agreement and essential agreement. Etest proved to be an accurate method for testing beta-lactam susceptibilities of the emerging PRASEF isolates, disk diffusion presented poor performance, particularly for imipenem and piperacillin.

Variability of Beta-Lactam Broth Microdilution for Pseudomonas aeruginosa

2021 ◽  
Author(s):  
A. A. Bhalodi ◽  
N. Oppermann ◽  
S. A. Campeau ◽  
R. M. Humphries
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Treatment Options ◽  
Reference Method ◽  
Broth Microdilution ◽  
Beta Lactam ◽  
Beta Lactams ◽  
The Media ◽  
Susceptibility Tests ◽  
Inherent Strain ◽  
The Impact

Antimicrobial susceptibility testing for Pseudomonas aeruginosa is critical to determine suitable treatment options. Commercial susceptibility tests are typically calibrated against the reference method, broth microdilution (BMD). Imprecision of minimum inhibitory concentrations (MICs) obtained by BMD for the same isolate on repeat testing is known to exist. Factors that impact the extent of variability include concentration of the inoculum, operator effects, contents of the media, inherent strain properties, and the testing process or materials. We evaluated the variability of BMD for anti-pseudomonal beta-lactams (aztreonam, cefepime, ceftazidime, meropenem, piperacillin-tazobactam, ceftazidime-avibactam, ceftolozane-tazobactam) tested against a collection of P. aeruginosa isolates. Multiple replicate BMD tests were performed and MICs were compared to assess reproducibility, including the impact of the inoculum and operator. Overall, essential agreement (EA) was ≥ 90% for all beta-lactams tested. Absolute agreement (AA) was as low as 70% for some beta-lactams. Variability from the inoculum and operators impacted the reproducibility of MICs. Piperacillin-tazobactam exhibited the highest degree of variability with 74% AA and 94%% EA. The implications of MIC variability are extensive as the MIC is essential for multiple facets of microbiology, such as the development of new compounds and susceptibility tests, dose optimization and pharmacokinetic/pharmacodynamic (PK/PD) targets for individual patients.

scholarly journals Quality Control Guidelines for Disk Diffusion and Broth Microdilution Antimicrobial Susceptibility Tests with Seven Drugs for Veterinary Applications

2000 ◽  
Vol 38 (1) ◽  
pp. 453-455
Author(s):  
Brant A. Odland ◽  
Meredith E. Erwin ◽  
Ronald N. Jones
Keyword(s):  
Quality Control ◽  
Antimicrobial Susceptibility ◽  
Susceptibility Testing ◽  
Clinical Laboratory ◽  
Disk Diffusion ◽  
National Committee ◽  
Broth Microdilution ◽  
E Coli ◽  
Antimicrobial Susceptibility Tests ◽  
Susceptibility Tests

ABSTRACT This multicenter study proposes antimicrobial susceptibility (MIC and disk diffusion methods) quality control (QC) parameters for seven compounds utilized in veterinary health. Alexomycin, apramycin, tiamulin, tilmicosin, and tylosin were tested by broth microdilution against various National Committee for Clinical Laboratory Standards (NCCLS)-recommended QC organisms ( Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212, Streptococcus pneumoniae ATCC 49619, Escherichia coli ATCC 25922, and Pseudomonas aeruginosa ATCC 27853). In addition, disk diffusion zone diameter QC limits were determined for apramycin, enrofloxacin, and premafloxacin by using E. coli ATCC 25922, P. aeruginosa ATCC 27853, and S. aureus ATCC 25923. The results from five or six participating laboratories produced ≥99.0% of MICs and ≥95.0% of the zone diameters within suggested guidelines. The NCCLS Subcommittee for Veterinary Antimicrobial Susceptibility Testing has recently approved these ranges for publication in the next M31 document.

scholarly journals Haemophilus influenzae with Non-Beta-Lactamase-Mediated Beta-Lactam Resistance: Easy To Find but Hard To Categorize

2015 ◽  
Vol 53 (11) ◽  
pp. 3589-3595 ◽  
Author(s):  
Dagfinn Skaare ◽  
Astrid Lia ◽  
Anja Hannisdal ◽  
Yngvar Tveten ◽  
Erika Matuschek ◽  
...  
Keyword(s):  
Haemophilus Influenzae ◽  
Disk Diffusion ◽  
High Dose ◽  
Beta Lactamase ◽  
Penicillin Binding Protein ◽  
Beta Lactam ◽  
Beta Lactams ◽  
Content Type ◽  
Severe Infections ◽  
Clinical Breakpoints

Haemophilus influenzaeis a major pathogen, and beta-lactams are first-line drugs. Resistance due to altered penicillin-binding protein 3 (rPBP3) is frequent, and susceptibility testing of such strains is challenging. A collection of 154 beta-lactamase-negative isolates with a large proportion of rPBP3 (67.5%) was used to evaluate and compare Etest (Haemophilustest medium [HTM]) and disk diffusion (EUCAST method) for categorization of susceptibility to aminopenicillins and cefuroxime, using MICs generated with broth (HTM) microdilution and clinical breakpoints from CLSI and EUCAST as the gold standards. In addition, the proficiency of nine disks in screening for the rPBP3 genotype (N526K positive) was evaluated. By Etest, both essential and categorical agreement were generally poor (<70%), with high very major errors (VME) (CLSI, 13.0%; EUCAST, 34.3%) and falsely susceptible rates (FSR) (CLSI, 87.0%; EUCAST, 88.3%) for ampicillin. Ampicillin (2 μg) with adjusted (+2 mm) zone breakpoints was superior to Etest for categorization of susceptibility to ampicillin (agreement, 74.0%; VME, 11.0%; FSR, 28.3%). Conversely, Etest was superior to 30 μg cefuroxime for categorization of susceptibility to cefuroxime (agreement, 57.1% versus 60.4%; VME, 2.6% versus 9.7%; FSR, 7.1% versus 26.8%). Benzylpenicillin (1 unit) (EUCAST screening disk) and cefuroxime (5 μg) identified rPBP3 isolates with highest accuracies (95.5% and 92.2%, respectively). In conclusion, disk screening reliably detects rPBP3H. influenzae, but false ampicillin susceptibility is frequent with routine methods. We suggest adding a comment recommending high-dose aminopenicillin therapy or the use of other agents for severe infections with screening-positive isolates that are susceptible to aminopenicillins by gradient or disk diffusion.

scholarly journals Combinations of Vancomycin and β-Lactams Are Synergistic against Staphylococci with Reduced Susceptibilities to Vancomycin

1999 ◽  
Vol 43 (7) ◽  
pp. 1747-1753 ◽  
Author(s):  
Michael W. Climo ◽  
Roberto L. Patron ◽  
Gordon L. Archer
Keyword(s):  
Single Agent ◽  
Rabbit Model ◽  
Test Methods ◽  
Disk Diffusion ◽  
Antistaphylococcal Activity ◽  
Vancomycin Mics ◽  
Disk Diffusion Testing ◽  
Antimicrobial Susceptibility Tests ◽  
Amoxicillin Clavulanate ◽  
Susceptibility Tests

ABSTRACT Evidence of synergism between combinations of vancomycin and β-lactam antibiotics against 59 isolates of methicillin-resistant staphylococci (Staphylococcus aureus, Staphylococcus epidermidis, and Staphylococcus haemolyticus) for which vancomycin MICs ranged from 1 to 16 μg/ml were tested by broth microdilution checkerboard, disk diffusion, agar dilution, and time-kill antimicrobial susceptibility tests. The combination of vancomycin and oxacillin demonstrated synergy by all test methods against 30 of 59 isolates; no antagonism was seen. Synergy with vancomycin was also found by modified disk diffusion testing for ceftriaxone, ceftazidime, cefpodoxime, and amoxicillin-clavulanate but not for aztreonam. Evidence of synergy correlated directly with vancomycin MICs. The efficacy of vancomycin given alone and in combination with nafcillin was tested in the rabbit model of experimental endocarditis caused by three clinical isolates of glycopeptide-intermediate-susceptible S. aureus (GISA) (isolates HIP5827, HIP5836, and MU50). Two of the GISA isolates (isolates MU50 and HIP5836) were extremely virulent in this model, with 27 of 42 (64%) animals dying during the 3-day trial. Therapy with either vancomycin or nafcillin given as a single agent was ineffective for animals infected with HIP5827 or MU50. However, the combination of vancomycin and nafcillin resulted in a mean reduction of 4.52 log10 CFU/g of aortic valvular vegetations per g compared to the reduction for controls for animals infected with HIP5827 and a reduction of 4.15 log10 CFU/g for animals infected with MU50. Renal abscesses caused by HIP5827 were sterilized significantly better with the combination of vancomycin and nafcillin than by either treatment alone. We conclude that the combination of vancomycin and β-lactams with antistaphylococcal activity is an effective regimen for the treatment of infections with clinical strains of staphylococci which demonstrate reduced susceptibility to glycopeptides.

scholarly journals Ampicillin Plus Ceftriaxone Regimen against Enterococcus faecalis Endocarditis: A Literature Review

2021 ◽  
Vol 10 (19) ◽  
pp. 4594
Author(s):  
Andrea Marino ◽  
Antonio Munafò ◽  
Aldo Zagami ◽  
Manuela Ceccarelli ◽  
Rosaria Di Mauro ◽  
...  
Keyword(s):  
Enterococcus Faecalis ◽  
Clinical Settings ◽  
Drug Resistant ◽  
Efficacy And Safety ◽  
Beta Lactam ◽  
Beta Lactams ◽  
Therapeutic Approaches ◽  
Resistant Strains ◽  
Changing Demographics ◽  
Drug Resistant Strains

Enterococcus faecalis infective endocarditis (EFIE) continues to represent a potentially fatal infectious disease characterized by elevated morbidity and mortality. Despite advances in antimicrobial therapy, changing demographics and the reduced availability of useful antibiotics combined with the dissemination of multi-drug resistant strains, the mortality rate remained unchanged in the last decades. Nowadays, optimizing the antibiotic regimen is still of paramount importance. Historically, aminoglycosides were considered as a cornerstone for treatment even though their use is associated with a high risk of kidney failure. It is against this background that, in recent years, several studies have been carried in order to assess the validity of alternative therapeutic approaches, including combinations of beta-lactams, that, acting synergistically, have yielded useful results in different clinical settings. In this scenario, we searched and critically report clinical studies assessing the efficacy and safety of double beta-lactam therapy in treating EFIE.

scholarly journals Beta-lactamases and detection of beta-lactam resistance in Enterobacter spp.

1997 ◽  
Vol 41 (1) ◽  
pp. 35-39 ◽  
Author(s):  
J D Pitout ◽  
E S Moland ◽  
C C Sanders ◽  
K S Thomson ◽  
S R Fitzsimmons
Keyword(s):  
Disk Diffusion ◽  
Broth Microdilution ◽  
Beta Lactam ◽  
Disk Diffusion Test ◽  
Beta Lactamases ◽  
Beta Lactam Antibiotics ◽  
Resistant Strains ◽  
Group 2 ◽  
Susceptibility Tests ◽  
Group 1

Enterobacter spp. are becoming increasingly frequent nosocomial pathogens, and beta-lactam-resistant strains are on the increase, especially among isolates recovered from intensive care units. Therefore, a study was designed to characterize the beta-lactamases produced by 80 isolates of E. cloacae, E. aerogenes, E. taylorae, E. gergoviae, E. sakazakii, E. asburiae, and E. agglomerans by induction studies, spectrophotometric hydrolysis assays, and isoelectric focusing. The ability of broth microdilution and disk diffusion susceptibility tests to detect resistance to 16 beta-lactam antibiotics among these species was also assessed. All species except E. agglomerans, E. gergoviae, and some isolates of E. sakazakii were found to produce a Bush group 1 cephalosporinase that was expressed inducibly or constitutively at high levels. In addition, some strains also produced a Bush group 2 beta-lactamase. In comparisons of broth microdilution and disk diffusion tests, disk diffusion tests failed to detect resistance in 1 of 25 isolates resistant to aztreonam and 2 of 30 isolates resistant to ceftazidime. These results indicate that species of Enterobacter can possess a variety of beta-lactamases that are responsible for beta-lactam resistance in this genus and that the disk diffusion test may occasionally miss resistance in some strains.

scholarly journals Investigations On The Resistance Of Porcine Commensal E. Coli Isolates To Beta Lactams

2015 ◽  
Vol 65 (4) ◽  
pp. 538-547 ◽  
Author(s):  
Valentina Urumova
Keyword(s):  
Antimicrobial Agents ◽  
Disk Diffusion ◽  
Diffusion Method ◽  
Dilution Method ◽  
Beta Lactams ◽  
Disk Diffusion Method ◽  
E Coli ◽  
Resistance Patterns ◽  
The Republic ◽  
Broth Dilution

AbstractThe aim of this study was to describe the prevalence of antibiotic resistance to beta-lactams and to evaluate two resistance genesblaTEMandblaOXA-1inEscherichia coliisolates from faeces on six swine farms in the Republic of Bulgaria. A total of 186E. coliisolates from 192 faecal swabs were tested by the disk diffusion method to determine resistance patterns to 11 antimicrobial agents. Resistance to beta-lactams was determined by disk diffusion method, E-test, micro-broth dilution method and PCR. About 40.3% of theE. coliisolates from swine were resistant to ampicillin. The highest resistance was observed inE.coliisolates from weaned pigs to ampicillin – 60.0% and to cephalotin – 45.5 %. TheE. coliisolates resistant to beta-lactams were examined for the presence ofblaTEMandblaOXA-1genes. The most commonblagene identified wasblaTEM, which was found in 92.0% of swine isolates.

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