Erythromycin-resistant Bordetella pertussis--Yuma County, Arizona, May-October 1994.

In 1993, a total of 6586 cases of pertussis was reported in the United States, including 70 in Arizona. On June 27, 1994, a case of Bordetella pertussis disease caused by a strain resistant to erythromycin was reported to the Arizona Department of Health Services (ADHS) from Yuma County (1990 population: 106,895). Susceptibility testing at CDC confirmed that the isolate was highly resistant to erythromycin with a minimum inhibitory concentration (MIC) > 64 micrograms/mL. The MIC of erythromycin against B. pertussis usually ranges from 0.02 micrograms/mL to 0.1 micrograms/mL, and resistant isolates have not been previously reported (1). This report summarizes the case investigation and describes efforts to enhance surveillance for pertussis in Arizona.