Evaluation of manufacturer's recommended growth value thresholds for BACTEC media

Abstract

LETTERS TO THE EDITOR dimethyl sulfoxide (DMSO) enhancement of CMV and herpes simplex virus, he will be aware that both of these studies were done entirely with fresh specimens (2, 3). We saw absolutely no difference in the appearance of CMV inclusions with these fresh specimens and that of CMV inclusions with our older specimens and no evidence of false positives caused by "artifacts" or "particulates-precipitates" with our monoclonal anti-CMV antibodies. Neither have we found any accounts of such false positives in the literature or heard of them from colleagues. What we have seen, rather, is a loss in viability of the virus with storage, resulting in specimens becoming negative. We took advantage of this fact to push our system to the limit and to create a more rigorous test of sensitivity by including a larger percentage of these borderline positives. Another reason for using previously determined positives was the expense of shell vials. We did not wish to waste large numbers of them on negative specimens which would not figure into our data. Another point worth touching on is the fact that methods of virus recovery may vary considerably with the type of specimen involved. Judging from the titles of Dr. Lipson's papers and abstract (1), two out ot three of these articles deal with CMV in blood specimens. None of our studies have included blood specimens. Along the same lines, Dr. Lipson seems to question the efficacy of DEX (we use DEX not alone but in conjunction with DMSO and calcium) as an enhancing agent, yet the title of one of his papers is "Enhanced Detection of Cytomegalovirus in Shell Vial Culture following MRC-5 Monolayer Pretreatment with Glucocorticoids." Unfortunately, since his papers are not yet published, it is impossible for me to further compare our work with Dr. Lipson's until his data and methodologies become available.