Heart valve allograft decontamination with antibiotics: impact of the temperature of incubation on efficacy
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Heart valve allograft decontamination with antibiotics: impact of the temperature of incubation on efficacy Marc Germain Æ Louis Thibault Æ Annie Jacques Æ Jacynthe Tremblay Æ Re´mi Bourgeois
Received: 13 March 2009 / Accepted: 26 August 2009 / Published online: 14 April 2010 Ó Springer Science+Business Media B.V. 2009
Abstract Heart valve allografts are typically processed at 4°C in North America, including the step of antibiotic decontamination. In our own experience with heart valve banking, we often observe persistent positive cultures following decontamination at wet ice temperature. We hypothesized that warmer temperatures of incubation might increase the efficacy of the decontamination procedure. In a first series of experiments, 12 different bacterial species were grown overnight, frozen in standardized aliquots and used directly to inoculate antibiotic cocktail aliquots at 105 colony-forming units (CFU)/ml. The antibiotic cocktail contains vancomycin (50 lg/ml), gentamicin (80 lg/ml) and cefoxitin (240 lg/ml) in Dulbecco’s Modified Eagle’s Medium. Inoculated aliquots were incubated at 4, 22 and 37°C and CFUs were determined at regular intervals up to 24 h post-inoculation. In a second set of experiments, 10 heart valves were spiked with 5000 CFU/ml and incubated with antibiotics at 4 and 37°C for 24 h. The final rinse solutions of these heart valves were filtered and tested for bacterial growth. After 24 h of incubation, CFUs of all 12 bacterial species were reduced by a factor of only one
M. Germain (&) L. Thibault (&) A. Jacques J. Tremblay R. Bourgeois He´ma-Que´bec, 1070, avenue des Sciences-de-la-Vie, Quebec, QC G1V 5C3, Canada e-mail: [email protected] L. Thibault e-mail: [email protected]
to two logs at 4°C whereas log reductions of 3.7 and 5.0 or higher were obtained at 22 and 37°C, respectively. Most microorganisms, including Staphylococcus epidermidis, Lactococcus lactis lactis and Propionibacterium acnes survived well the 24-h antibiotic treatment at 4°C (\1 Log reduction). All 10 heart valves that were spiked with microorganisms had positive final rinse solutions after antibiotic soaking at 4°C, whereas 8 out of 10 cultures were negative when antibiotic decontamination was done at 37°C. These experiments show that a wet ice temperature greatly reduces the efficacy of the allograft decontamination process as microorganisms survived well to a 24-h 4°C antibiotic treatment. This could explain the high rate of positive post-processing cultures obtained with our routine tissue decontamination procedure. Increasing the decontamination temperature from 4 to 37°C may significantly reduce the incidence of post-disinfection bacterial contamination of heart valves. Keywords Disinfection Valvular Homograft Bacterial contamination
Introduction During procurement and processing of heart valve allografts, specific procedures are applied to decrease the risk of transmitting infectious agents to recipients.
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In addition to donor screening tests for viral a
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