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

Kiehn, Timothy E.; Capitolo, C; Armstrong, David

doi:10.1128/jcm.16.1.96-98.1982

Cited by 20 publications

(12 citation statements)

References 7 publications

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“…Kiehn et al (6) found only 0.7% categorical discrepancies between MicroScan MIC panels inoculated directly and by standard methodology from nonautomated blood culture systems. More recently, Pettigrew et al (13) compared results of direct inoculation from positive BacT/Alert bottles to Micro-Scan gram-positive and gram-negative rapid panels.…”

Section: Discussionmentioning

confidence: 99%

“…Automated blood culture systems such as BacT/Alert and rapid MIC panels provided by automated bacterial identification and susceptibility testing systems such as MicroScan can potentially make direct susceptibility testing even more clinically valuable, allowing preliminary results in a matter of hours after growth is first detected in the blood culture bottle. Although the concept of direct inoculation of fluid from positive blood culture bottles into MIC panels was investigated in the early 1980s (6), no prospective evaluations by using the current MicroScan instrumentation, panels, software, and database, newer antimicrobials, or with more recently developed continuously monitoring blood culture instruments such as the BacT/Alert have been published.…”

Section: Discussionmentioning

confidence: 99%

“…Even though automated systems have reduced the time required to detect microorganisms in bloodstream infections, the relatively low number of bacteria in culture bottles may compromise the inoculum concentration, if not standardized, for susceptibility tests. This may partially account for the relatively high error rates for direct susceptibility testing with MIC methods reported by some studies evaluating blood cultures performed in automated instruments (5,12), but others (2,6,13) yielded more favorable comparisons.…”

Section: Discussionmentioning

confidence: 99%

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Direct Susceptibility Testing with Positive BacT/Alert Blood Cultures by Using MicroScan Overnight and Rapid Panels

et al. 1998

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Studies were conducted on a method of direct inoculation of MicroScan dried overnight and of rapid panels with positive aerobic blood cultures obtained from the BacT/Alert to determine antimicrobial susceptibilities. Inocula were limited to specimens that appeared unimicrobic on Gram stain. Results were compared to those obtained from panels inoculated following subculture. For 133 gram-negative bacilli, there were 94.7 and 93.5% categorical agreements between direct and standard methods for all drugs tested with overnight and rapid panels, respectively. For 104 gram-positive cocci, there were 93.2 and 93.1% categorical agreements for overnight and rapid panels, respectively. The major error (false resistance) rate for gram negatives was 1.4% for overnight versus 0.7% for rapid panels. The very major error (false susceptibility) rate was 2.7% for overnight versus 8.1% for rapid panels. The total error rates were 1.6% for overnight panels and 1.5% for rapid panels. The major error rates for gram-positive direct susceptibility tests were 2.6% for overnight and 2.5% for rapid panels. The very major error rates were 8.8 and 7.2% for overnight and rapid panels, respectively. Total error rates were 3.6% for overnight and rapid gram-positive panels. These findings suggest that susceptibility results obtained from directly inoculated gram-negative overnight panels have the greatest correlation to those obtained by standard methods. When discrepant results occur with direct-susceptibility testing, they are more likely to show false susceptibility than false resistance.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Direct Susceptibility Testing with Positive BacT/Alert Blood Cultures by Using MicroScan Overnight and Rapid Panels

et al. 1998

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“…Direct antimicrobial susceptibility testing, either by agar disk diffusion (8,13,17) or broth dilution (14), of positive blood cultures containing bacteria was found to be feasible under most conditions. In addition, an impedimetric method has been developed for direct antimicrobial susceptibility testing of gram-negative bacilli (12) and for detection of oxacillin-resistant Staphylococcus aureus in blood cultures (36).…”

Section: Discussionmentioning

confidence: 99%

Evaluation of a Capacitance Method for Direct Antifungal Susceptibility Testing of Yeasts in Positive Blood Cultures

Chang

Huang

et al. 2000

J Clin Microbiol

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The feasibility of using a capacitance method (CM) for direct antifungal susceptibility testing of yeasts in positive blood cultures was evaluated. The CM used the same test conditions as those recommended by the National Committee for Clinical Laboratory Standards. After direct inoculation of positive culture broths into module wells (Bactometer; bioMérieux, Inc., Hazelwood, Mo.), the end-point determination was made by monitoring the capacitance change in the culture broths with Bactometer. The MIC of amphotericin B was the lowest concentration at which yeast growth was completely inhibited, while the MICs of ketoconazole, flucytosine, and fluconazole were the concentrations at which a ≥80% reduction in capacitance change was observed. The MICs of the four drugs against each blood isolate obtained on subculture plates were also determined by the macrodilution method. For 51 positive blood cultures tested, the percent agreement (±2 log2 dilutions) between the CM and the macrodilution method were as follows: amphotericin B (98%), ketoconazole (92%), flucytosine (84%), and fluconazole (96%). The CM was further used for breakpoint susceptibility testing of fluconazole (8 and 64 μg/ml) and flucytosine (4 and 32 μg/ml) against yeasts in positive blood cultures. After testing of 74 specimens by the CM, flucytosine and fluconazole produced one (1.4%) major error and two (2.8%) minor errors, respectively. All yeasts that displayed resistance to flucytosine or fluconazole were detected within 24 h after direct inoculation of the positive broths into Bactometer. The CM may be useful for the rapid detection of antifungal resistance in positive blood cultures containing yeasts.

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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.…”

mentioning

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

Cited by 20 publications

References 7 publications

Direct Susceptibility Testing with Positive BacT/Alert Blood Cultures by Using MicroScan Overnight and Rapid Panels

Direct Susceptibility Testing with Positive BacT/Alert Blood Cultures by Using MicroScan Overnight and Rapid Panels

Evaluation of a Capacitance Method for Direct Antifungal Susceptibility Testing of Yeasts in Positive Blood Cultures

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

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