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A screening UDT can result in a false positive for opioids if the donor is on a quinolone antibiotic or a false negative if the donor is on a synthetic opioid such as fentanyl or methadone.

Quinolone antibiotics, first developed in the 1960s, kill bacteria by blocking enzymes called class II topoisomerases, which normally untangle DNA during cell replication.

It helped to trigger a wave of reports on websites such as the Quinolone Antibiotics Adverse Reaction Forum, which by 2001 hosted more than 5,000 posts.

Helping coordinate the effort is the patient advocacy group Quinolone Vigilance Foundation.

In 2013, one-quarter of campylobacter samples from sick people were resistant to quinolone antibiotics such as ciprofloxacin, the agency said.