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Antimicrobial Agents and Chemotherapy, October 2006, p. 3450-3453, Vol. 50, No. 10
0066-4804/06/$08.00+0 doi:10.1128/AAC.00658-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
3)-ß-D-Glucan Assay with Commonly Used Intravenous Antimicrobials
Brigham & Women's Hospital,1 Dana-Farber Cancer Institute,2 Harvard Medical School, Boston, Massachusetts,3 Associates of Cape Cod, Inc., East Falmouth, Massachusetts4
Received 30 May 2006/ Returned for modification 15 July 2006/ Accepted 31 July 2006
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3)-ß-D-glucan (BG). Colistin, ertapenem, cefazolin, trimethoprim-sulfamethoxazole, cefotaxime, cefepime, and ampicillin-sulbactam tested positive for BG at reconstituted-vial concentrations but not when diluted to usual maximum plasma concentrations. False-positive BG assays may occur when some antimicrobials are administered; however, this needs to be confirmed. |
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3)-ß-D-Glucan (BG) is present in the cell walls of many pathogenic fungi, including Candida sp., Aspergillus sp., and Fusarium sp. (11). Galactomannan detection by sandwich enzyme-linked immunosorbent assay (Platelia Aspergillus enzyme-linked immunosorbent assay; Bio-Rad Laboratories, Hercules, CA) was approved by the FDA as a diagnostic aid for the diagnosis of invasive aspergillosis in 2003 (2). Although the in vitro cross-reactivity of galactomannan with piperacillin-tazobactam had been reported (1, 18), it was only after marketing the assay that clinical false-positive results were observed (14, 17). This diminished the diagnostic utility of galactomannan detection in centers where piperacillin-tazobactam had become the empirical antibacterial treatment of febrile neutropenic patients.
False-positive BG results are known to occur in patients undergoing hemodialysis with cellulose membranes (5); patients treated with immunoglobulin, albumin (4, 12), or other blood products filtered through cellulose depth filters containing BG (9, 16); and patients with serosal exposure to glucan-containing gauze (6).
Given the potential for fungal cell wall elements or leachates from cellulosic materials to be present in antimicrobial preparations, we sought to determine the reactivity of the BG assay among intravenous antimicrobials available in the United States.
(This work was presented in part previously [F. M. Marty, C. M. Lowry, S. J. Lempitski, D. W. Kubiak, M. A. Findelman, and L. R. Baden, Abstr. 45th Intersci. Conf. Antimicrob. Agents Chemother., abstr. M-163, 2005].)
Forty-four commercially available intravenous antimicrobial agents were tested for the presence of BG using the Glucatell assay (Table 1). An initial lot was tested for each agent, with the exception of piperacillin-tazobactam, for which three lots were tested. All drug samples were diluted or solubilized, as specified in the product's package insert, to yield reconstituted-vial concentrations (RVC). All diluents used in the reconstitution process were also tested. Once prepared, samples were coded, placed in BG-free vials, frozen to 80°C, and shipped for analysis to Beacon Diagnostics Laboratory (East Falmouth, MA), where all samples were tested in a blind fashion.
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TABLE 1. Antimicrobials, manufacturers, and lots tested
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RVC drug solutions that tested positive or inhibited the BG reaction when diluted to concentrations above the drug infusate concentration (DIC) were retested at the DIC and maximum plasma concentrations (MPC) as directed in the package insert or scientific literature (Table 1). Further lots of those antimicrobials that tested positive or inhibited the BG reaction were analyzed for reproducibility. All these samples were prepared and tested in a blind fashion.
Seven antimicrobial agents tested positive for BG at the RVC: colistin, ertapenem, cefazolin (in vials), trimethoprim-sulfamethoxazole, cefotaxime, cefepime, and ampicillin-sulbactam in decreasing order (Table 2). BG was detected in additional lots of these antimicrobials at the RVC, with the exception of ampicillin-sulbactam, of which two additional lots were nonreactive. Colistin, ertapenem, cefotaxime, and cefepime had detectable BG at concentrations greater than 80 pg/ml when diluted to the DIC; two lots of colistin inhibited the reaction and needed to be diluted 500-fold in order to obtain a valid result at the DIC. Although all lyophilized cefazolin vials had detectable BG at the RVC, no premixed cefazolin bag lots from a different manufacturer had detectable BG. None of the seven agents tested positive for BG when diluted to concentrations representing the MPC. Diluents and products used in the transfer of drug did not have detectable BG levels. Several antimicrobials inhibited the BG assay at the RVC, but only azithromycin, pentamidine, and colistin remained highly inhibitory at the DIC (Table 2).
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TABLE 2. BG content of intravenous antimicrobialsa
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BG was detected in 7 of the 44 antimicrobial agents at RVC. BG was still detected in four of seven of these antimicrobials at DICs that are above the current positivity threshold for the assay. BG positivity was consistent among different antimicrobial lots, except with ampicillin-sulbactam. Some antimicrobials caused optical artifacts or inhibited the BG assay at high concentrations. Although not available in the United States, intravenous amoxicillin-clavulanic acid was found to contain high BG levels and to cause false-positive results after clinical administration (8).
There was no obvious antimicrobial class effect in terms of the BG reactivity. No antimicrobial solution had detectable BG at the usual drug MPC, but this should be interpreted with caution. As learned from the galactomannan enzyme-linked immunosorbent assay cross-reactivity experience with piperacillin-tazobactam administration (7, 17, 18), the false-positive results were not due to detection of the antimicrobial itself but to the introduction of galactofuran in the manufacturing process, which has a pharmacokinetic behavior different than that of the antimicrobial itself (18).
The findings of BG content cannot be generalized to products produced by manufacturers other than those tested (Table 1). There can be lot-to-lot variability in BG content, as in the case of galactomannan (7), so additional periodic testing of antimicrobial lots commonly used in patients at risk for IFI may be warranted, especially if unexplained BG results are encountered. Interestingly, no piperacillin-tazobactam lots tested positive for BG. This may allow centers that use piperacillin-tazobactam for empirical febrile neutropenia therapy the possibility of using BG for noninvasive surveillance and diagnosis of IFI.
There is limited reactivity between the BG assay and most commonly used intravenous antimicrobial agents. Caution should be used in interpreting BG assay results for drug preparations that do contain BG, as the kinetics of BG are not yet defined. Validation of these findings and correlation with clinical samples are warranted.
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3)-beta-D-glucan level. Kidney Int. 60:319-323.[CrossRef][Medline]
3)-beta-D-glucan caused by filtration with cellulose filters in the manufacturing process. J. Artif. Organs 6:49-54.[CrossRef][Medline]
3)-beta-D-glucan test following immunoglobulin product replacement in an adult bone marrow recipient. Int. J. Hematol. 80:97-98.[CrossRef][Medline]
3)-beta-D-glucan in the horseshoe crab coagulation factor G: implications for a molecular basis of the pattern recognition in innate immunity. J. Biol. Chem. 277:14281-14287.
3)-beta-D-glucan in blood components and release of (1
3)-beta-D-glucan from depth-type membrane filters for blood processing. Transfusion 42:1189-1195.[CrossRef][Medline]This article has been cited by other articles:
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