A Microdilution Method for Antibiotic Susceptibility Testing: An Evaluation

Gavan, Thomas L.; Town, Mary Ann

doi:10.1093/ajcp/53.6.880

Cited by 55 publications

(38 citation statements)

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“…The results of this study show a good agreement between these two techniques. Because many other studies have also attested to the accuracy and reproducibility of the microdilution technique when compared to the broth dilution method (3,7,13), serious consideration should be given to its implementation.…”

Section: Resultsmentioning

confidence: 99%

Synergism of Cefazolin-Gentamicin Against Enterococci

Bourque¹,

Quintiliani

Tilton³

1976

Antimicrob Agents Chemother

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A miniaturized technique for detecting antibiotic synergy by using microliter volumes was perfected. With this microtiter serial dilution method, the effect of the previously untried combination of cefazolin and gentamicin on 10 strains of enterococci was evaluated. At clinically achievable concentrations, the combination of cefazolin and gentamicin was found to be synergistic against all 10 strains when the data were plotted in the form of an isobologram. These results were compared with the conventional method of detecting synergy in vitro, namely, the determination of the rate of killing of the microorganisms with the antibiotics, singly and in combination. Similar results were also observed. These findings indicate that the microtiter serial dilution technique is a useful method for the routine determination of drug synergy. Moreover, in a patient with penicillin hypersensitivity and enterococcal infection, the combination of cefazolin and gentamicin should be considered for possible therapy.

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Section: Resultsmentioning

confidence: 99%

Synergism of Cefazolin-Gentamicin Against Enterococci

Bourque¹,

Quintiliani

Tilton³

1976

Antimicrob Agents Chemother

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“…This time trays were prepared once a week for 4 consecutive weeks, and 12 wells were selected from each tray for bioassay. The results of these initial tests before storage of the trays are included in Table 2.…”

Section: Resultsmentioning

confidence: 99%

“…Trays containing ampicillin prepared in experiment 1 were stored for 1, 2, or 3 weeks at both -20 and -60 C. On week 4 b Based on 32 tests for each storage condition or for each set of "fresh" plates.…”

Section: Resultsmentioning

confidence: 99%

“…The bags were then sealed with masking tape and stored in a Revco freezer (-60 C) or in a household freezer without automatic defrost (-20 C). After 1, 2, 3, or 4 weeks of storage, the trays were removed from the freezer and allowed to thaw at room temperature before testing.…”

Section: Methodsmentioning

confidence: 99%

“…Quantitative susceptibility tests can be performed efficiently with a microdilution technique (3)(4)(5)(6)(7)(8)(9)(10), especially since the development of semiautomated equipment for preparing serial dilutions of the antimicrobial agent. Such semiautomated equipment can be used effectively only when large numbers of trays containing antimicrobial dilutions can be prepared at one time and held frozen until needed, rather than preparing fresh sets of dilutions each day.…”

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confidence: 99%

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Short-Term Storage of Six Penicillins and Cephalothin in Microdilution Trays for Antimicrobial Susceptibility Tests

Barry

Effinger²,

Badal³

1976

Antimicrob Agents Chemother

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To perform microdilution antimicrobial susceptibility tests efficiently, broth dilutions of the antimicrobial drugs should be prepared in large batches and stored frozen until needed. Studies were carried out to document the stability of ampicillin, benzylpenicillin, carbenicillin, methicillin, oxacillin, nafcillin, and cephalothin in microdilution trays during storage at -20 and -60 C. No significant deterioration was noted after 21 days of storage, as detected by bioassay and by replicate minimal inhibitory concentration determinations with control organisms. No significant differences were noted moreover between trays stored for three weeks at -20 C and those stored at -60 C. The microdilution technique was found to be a highly reproducible method for quantitative determination of antimicrobial susceptibility.Quantitative susceptibility tests can be performed efficiently with a microdilution technique (3-10), especially since the development of semiautomated equipment for preparing serial dilutions of the antimicrobial agent. Such semiautomated equipment can be used effectively only when large numbers of trays containing antimicrobial dilutions can be prepared at one time and held frozen until needed, rather than preparing fresh sets of dilutions each day. The present report documents the stability of ampicillin, benzylpenicillin, carbenicillin, methicillin, oxacillin, nafcillin, and cephalothin during short-term storage of microdilution trays at -20 and -60 C. These drugs were selected for study because they are notoriously unstable and most likely to become inactive during storage. To document the stability of these drugs, it was first necessary to estimate the accuracy and precision by which antibiotic dilutions could be prepared with our semiautomated system, an Autotiter IV (Canalco Ltd.). MATERIALS AND METHODSAntibiotic dilutions. Antibiotic powders were obtained from Canalco Ltd., Rockville, Md., and diluted in sterile distilled water to give stock solutions of the appropriate concentration. Serial dilutions were then prepared with an Autotiter IV (Canalco Ltd.), each well containing 50 ,ul of drug diluted in Mueller-Hinton broth (Difco). Each tray contained 16 series of seven doubling dilutions of antibiotics under study. The trays were either tested immediately or returned to the plastic bags in which they were received; each bag held a maximum of four trays plus an empty cover tray. The bags were then sealed with masking tape and stored in a Revco freezer (-60 C) or in a household freezer without automatic defrost (-20 C). After 1, 2, 3, or 4 weeks of storage, the trays were removed from the freezer and allowed to thaw at room temperature before testing.Inoculation of antibiotic dilutions. To evaluate the performance of different antibiotic trays replicate tests were performed with the "Seattle" Escherichia coli or Staphylococcus aureus (originally obtained fromn a subculture of ATCC 25922 or ATCC 25923) strains. The inoculum was standardized by diluting an actively growing broth culture to match th...

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Mass spectrometry methods for predicting antibiotic resistance

Charretier

Schrenzel

2016

Proteomics Clinical Apps

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Developing elaborate techniques for clinical applications can be a complicated process. Whole-cell MALDI-TOF MS revolutionized reliable microorganism identification in clinical microbiology laboratories and is now replacing phenotypic microbial identification. This technique is a generic, accurate, rapid, and cost-effective growth-based method. Antibiotic resistance keeps emerging in environmental and clinical microorganisms, leading to clinical therapeutic challenges, especially for Gram-negative bacteria. Antimicrobial susceptibility testing is used to reliably predict antimicrobial success in treating infection, but it is inherently limited by the need to isolate and grow cultures, delaying the application of appropriate therapies. Antibiotic resistance prediction by growth-independent methods is expected to reduce the turnaround time. Recently, the potential of next-generation sequencing and microarrays in predicting microbial resistance has been demonstrated, and this review evaluates the potential of MS in this field. First, technological advances are described, and the possibility of predicting antibiotic resistance by MS is then illustrated for three prototypical human pathogens: Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Clearly, MS methods can identify antimicrobial resistance mediated by horizontal gene transfers or by mutations that affect the quantity of a gene product, whereas antimicrobial resistance mediated by target mutations remains difficult to detect.

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A Microdilution Method for Antibiotic Susceptibility Testing: An Evaluation

Cited by 55 publications

References 0 publications

Synergism of Cefazolin-Gentamicin Against Enterococci

Synergism of Cefazolin-Gentamicin Against Enterococci

Short-Term Storage of Six Penicillins and Cephalothin in Microdilution Trays for Antimicrobial Susceptibility Tests

Mass spectrometry methods for predicting antibiotic resistance

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