Direct Method to Determine the Antibiotic Susceptibility of Rapidly Growing Blood Pathogens

Wegner, Dennis L.; Mathis, Clarence R.; Neblett, Thomas R.

doi:10.1128/aac.9.5.861

Cited by 19 publications

(18 citation statements)

References 1 publication

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“…They found that an inoculum of 0.03 ml of uncentrifuged blood culture fluid yielded acceptable results. Similarly, Wegner et al (5) observed excellent agreement between the results of direct and standardized disk diffusion tests when 0.01 ml of positive blood culture fluid was inoculated into 2 ml of Columbia broth, incubated at 37°C for 4 to 6 h, adjusted to a turbidity equivalent to a 0.5 BaSO4 McFarland standard with saline, and then used to inoculate susceptibility test plates. Although the inoculum size used in the present study (i.e., 0.05 ml of blood culture fluid) differed from those used by Fay and Oldfather (2) and Wegner et al (5), the level of agreement between direct and standardized test results was comparable.…”

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confidence: 79%

Evaluation of a direct blood culture disk diffusion antimicrobial susceptibility test

Doern¹,

Scott²,

Rashad³

et al. 1981

Antimicrob Agents Chemother

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A total of 556 unique blood culture isolates of nonfastidious aerobic and facultatively anaerobic bacteria were examined by direct and standardized disk susceptibility test methods (4,234 antibiotic-organism comparisons). When discrepancies which could be accounted for by the variability inherent in disk diffusion susceptibility tests were excluded, the direct method demonstrated 96.8% overall agreement with the standardized method. A total of 1.6% minor, 1.5% major, and 0.1% very major discrepancies were noted.

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confidence: 79%

Evaluation of a direct blood culture disk diffusion antimicrobial susceptibility test

Doern¹,

Scott²,

Rashad³

et al. 1981

Antimicrob Agents Chemother

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“…Rapid techniques for testing the susceptibilities of organisms in blood cultures include the direct disk diffusion test (3,4,9,11,16) and automated or semiautomated instrument systems. Direct disk diffusion susceptibility testing of the organisms in positive blood cultures has been shown to be reliable for most microorganisms and antimicrobial agents (4,6,16,24); this technique can save 18 to 24 h compared to the times required for the standardized protocols. Additional time savings can be obtained by early reading (6 to 10 h) of the plates after direct incubation (1,12,13); however, the test accuracy is sacrificed and some plates may not be readable due to limited bacterial growth.…”

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confidence: 99%

Direct Antimicrobial Susceptibility Testing of Gram-Negative Bacilli in Blood Cultures by an Electrochemical Method

Huang

Weng

et al. 1998

J Clin Microbiol

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Nonfastidious aerobic gram-negative bacilli (GNB) are commonly isolated from blood cultures. The feasibility of using an electrochemical method for direct antimicrobial susceptibility testing of GNB in positive blood cultures was evaluated. An aliquot (10 μl) of 1:10-diluted positive blood cultures containing GNB was inoculated into the Bactometer module well (bioMérieux Vitek, Hazelwood, Mo.) containing 1 ml of Mueller-Hinton broth supplemented with an antibiotic. Susceptibility tests were performed in a breakpoint broth dilution format, with the results being categorized as resistant, intermediate, or susceptible. Seven antibiotics (ampicillin, cephalothin, gentamicin, amikacin, cefamandole, cefotaxime, and ciprofloxacin) were used in this study, with each agent being tested at the two interpretive breakpoint concentrations. The inoculated modules were incubated at 35°C, and the change in impedance in each well was continuously monitored for 24 h by the Bactometer. The MICs of the seven antibiotics for each blood isolate were also determined by the standardized broth microdilution method. Of 146 positive blood cultures (1,022 microorganism-antibiotic combinations) containing GNB tested by the direct method, the rates of very major, major, and minor errors were 0, 1.1, and 2.5%, respectively. The impedance method was simple; no centrifugation, preincubation, or standardization of the inocula was required, and the susceptibility results were normally available within 3 to 6 h after inoculation. The rapid method may allow proper antimicrobial treatment almost 30 to 40 h before the results of the standard methods are available.

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“…In an effort to shorten the time required to obtain antibiotic susceptibility data on blood culture isolates, turbid blood broths have been directly inoculated into susceptibility testing systems. The direct inoculation procedure compared with the conventional method was shown to be accurate for disk diffusion (3,6,9) and agar dilution (5) methods.…”

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confidence: 99%

Comparison of direct and standard microtiter broth dilution susceptibility testing of blood culture isolates

Kiehn¹,

Capitolo²,

Armstrong³

1982

J Clin Microbiol

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Turbid broth (0.5 ml) from blood culture bottles was inoculated into 0.5 ml of brain heart infusion broth, incubated for 3 to 6 h, diluted 1:500 in distilled water, and then inoculated directly into microtiter broth dilution susceptibility trays to test for minimal inhibitory concentrations. The results were compared to the standard tests performed 24 h later on colonies from subculture plates. The minimal inhibitory concentrations measured by these two methods were compared in 1,875 organism-antibiotic tests. The two minimal inhibitory concentrations were identical in 86.0% and within one twofold dilution in 98.0% of the tests. An organism was judged to be susceptible by one method and resistant by the other in 13 tests (0.7%). These 13 discrepancies were distributed among several organism-antibiotic combinations; no more than two were seen for any one combination. Highly accurate susceptibility testing can be achieved by using direct inoculation of turbid blood culture broths.

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Direct Method to Determine the Antibiotic Susceptibility of Rapidly Growing Blood Pathogens

Abstract: Standardized direct disk diffusion antibiotic susceptibility testing on monomicrobial blood cultures is compared with the Food and Drug Administration method. The direct method yields acceptable data and may conserve 24 h in reporting results.

Cited by 19 publications

References 1 publication

Evaluation of a direct blood culture disk diffusion antimicrobial susceptibility test

Evaluation of a direct blood culture disk diffusion antimicrobial susceptibility test

Direct Antimicrobial Susceptibility Testing of Gram-Negative Bacilli in Blood Cultures by an Electrochemical Method

Comparison of direct and standard microtiter broth dilution susceptibility testing of blood culture isolates

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