ABSTRACT
A technique for determining the susceptibility to ganciclovir of cytomegalovirus (CMV) strains isolated in clinical samples is described. The inoculum was composed of a partially infected suspension of cells from a young positive culture (< 10 days), usually the first passage of the primary culture. The appropriate dilution of the cell suspension to provide a suitable inoculum was based on a previous study of five strains grown in different dilutions which provided a countable number of plaques and avoided titration of each of the isolated strains. Fifty-three strains were studied at three different dilutions. Five from patients on maintenance ganciclovir therapy with poor clinical response had a 50% inhibitory dose (ID50) between 21.46 and 13.35 microM and the remainder an ID50 between 2.31 and 10.5 microM, comparable to results obtained by other authors using susceptibility techniques with a sonicated inoculum. Three of these strains were studied by both methods using sonicated inoculum and cell suspension inoculum. The mean time which elapsed between seeding the specimen and obtaining sensitivity was 39.00 and 27.66 days, respectively. The technique reduces significantly the time involved since relatively young cultures can be studied and previous titration is not required.
Subject(s)
Antiviral Agents/pharmacology , Cytomegalovirus/drug effects , Ganciclovir/pharmacology , Cells, Cultured , Child , HumansABSTRACT
BACKGROUND: Virus investigation, specially cytomegalovirus (CMV), in blood has increased such that the capacity of hospitalary laboratories is threatened with collapse. The causal agents of viremia are analyzed being correlated with the clinical symptoms and underlying disease to establish the selection criteria of patients for virologic study. METHODS: Two thousand six hundred nineteen patients suspected of having viral infection, fundamentally by CMV were studied over 6 years by 4,394 blood samples. Of these patients 1,646 were immunosuppressed, 824 were considered immunocompetent and this data was unknown in 149 patients. The leukocytes were separated using standardized techniques being seeded in cell cultures (human embryo lung fibroblasts). RESULTS: Three hundred forty-seven specimens corresponding to 242 patients were positive with isolation of the following pathogens: 327 strains of CMV, 4 enterovirus, 2 adenovirus, 1 herpes simplex virus, 1 varicella-zoster, another 5 unidentified cytopathic agents, 6 strains of toxoplasma and 1 Cryptococcus. With regard to the base disease, 302 positive samples to CMV pertained to 204 immunosuppressed patients: 103 (13.6% positives among the cases studied) AIDS or AIDS-related complex, 54 (21.3%) kidney transplant patients, 31 (24.8%) liver transplant patients, 2 (1.5%) lung transplant patients, and 2 (1.5%) bone marrow transplant patients. A non CMV microorganism was isolated in 13 samples from 12 immunosuppressed patients. Only 24 (2.5% of those studied) immunocompetent or with unknown immunity status had viremia by CMV, being detected in 25 samples. Non CMV cytopathic agents were isolated in another 7 samples from 6 patients. CONCLUSIONS: Analysis of blood cultures allows the isolation of cytomegalovirus and occasionally other unsuspected agents such as toxoplasma. This investigation is indicated in immunosuppressed patients but not in immunocompetent patients who present a febrile syndrome with no clinical suspicion of cytomegalovirus infection.
