CHICAGO, Dec 19 (AFP) - For more than half of North Americans infected with HIV, the virus that causes AIDS, their infection is resistant to one or more of the drugs used to inhibit its spread.
According to a study presented here Tuesday, 51 percent of the 210,000 HIV-positive Americans are infected with a strain that is resistant to more than one drug, while 20 percent of all new infections are drug-resistant "even before we start antiviral therapy," said lead author Douglas Richman.
"The high proportion is surprising," Richman told the 41st Interscience Conference on Antimicrobial Agents and Chemotherapy here. "If they are drug-resistant viruses, there are fewer options of treatments.
"There needs to be more use of drug resistance testing to manage patients who have failed treatment" to help select drugs more likely to work, he added.
In 1999, Richman tested 1,647 HIV-positive patients from 10 US and Canadian cities in a study conducted under the aegis of the US Department of Veterans Affairs in San Diego, California.
"I'm confident there is a lot more multiple drug class resistance" now than in 1999, he said, adding drug-resistance was more pronounced in "gay white males with a good level of education" than in women or people from less privileged backgrounds.
Gay white males are more likely to have better access to treatment than the other groups, and thus more likely to develop resistances to certain drug therapies.
But Daniel Kuritzkes said the figures showing 20 percent of new infections are drug resistant before therapy means that educators and health care practitioners are doing an inadequate job at increasing awareness about safe sex.
"We are doing a pretty poor job at counseling patients regarding safe sex," the University of Colorado at Denver AIDS specialist said, since drug-resistant infections are likely passed from an infected patient already in treatment and ignoring physicians' recommendations about sexual activity.
Other studies showed that HIV was capable of mutating to the point it would resist all treatment. But Samuel Bozette, a colleague of Richman's, offered a glimmer of hope: "Many of the previous studies were relatively small and in highly-selected populations, so accurate estimates were not possible."
There are four classes of drugs that can control, but not cure, HIV.
Its capacity to develop resistance to drugs is "a time bomb" for researchers who must now redirect their efforts to test resistance in their patients, said Gilles Force of the French hospital Notre Dame of Perpetual Mercy.
"Resistance-testing is closer and closer to be selected as standard care," Kuritzkes said.
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