But health officials are alarmed about the spread of drug resistant forms, which can be difficult to treat or even deadly.

Death rates exceeding 80 percent have been reported for the drug resistant form in some outbreaks reported by Federal officials.

Death rates from the resistant forms of tuberculosis have been high.

Use as an agricultural growth stimulant is generating resistant forms.

Doctors in Mumbai said 12 patients had a "totally drug resistant" form of the infection, and three have died.

Another problem is the multi-drug resistant form of the disease.

The locks were highly resistant to most forms of attack.

Almost half of patients with the multi-drug resistant form of the disease die.

Her sandstorm form is resistant to most forms of injury.

This results in the development of resistant forms of the disease, as has happened with malaria.