Cytomegalovirus retinitis and viral resistance. Prevalence of resistance at diagnosis, 1994. Cytomegalovirus Retinitis and Viral Resistance Study Group.

OBJECTIVE

To determine the prevalence of cytomegalovirus (CMV) isolates resistant to ganciclovir sodium or foscarnet sodium at the time of diagnosis of CMV retinitis, prior to the initiation of therapy.

DESIGN

Prospective epidemiologic study.

SETTING

An acquired immunodeficiency syndrome ophthalmology clinic.

PATIENTS: Patients with acquired immunodeficiency syndrome and newly diagnosed CMV retinitis.

INTERVENTION: Culturing blood and urine samples for CMV and testing of all positive isolates for sensitivity to ganciclovir and foscarnet.

MAIN OUTCOME MEASURE: Prevalence of the following: blood culture isolates resistant to ganciclovir (inhibitory concentration 50% [IC50] > 5.5 mumol/L) or foscarnet (IC50 > 400 mumol/L) and urine culture isolates resistant to ganciclovir or foscarnet.

RESULTS

Forty-nine patients were enrolled during a 13-month period. Forty-four patients had blood culture samples that could be evaluated; of these, 66% were positive (59% of patients). Thirty-four patients had urine cultures that were evaluable; of these, 82% were positive (57% of patients). Overall, 78% of patients had either a urine or blood culture sample positive for CMV. No blood culture isolates were resistant to ganciclovir, and only 1 urine culture isolate (2% of patients) was resistant to ganciclovir. Three percent of blood culture isolates and 4% of urine culture isolates (2% and 2% of patients, respectively) were resistant to foscarnet. Overall, 4% of patients had either a blood or urine culture isolate resistant to foscarnet.

CONCLUSION

Resistance to ganciclovir or foscarnet at the time of diagnosis of CMV retinitis is uncommon.