TRUST/Ocular TRUST data document durability of fluoroquinolone activity nationwide

To get a better understanding of antimicrobial susceptibility patterns over time, the microbiology and internal medicine communities rely on the TRUST (Tracking Resistance in the United States Today) study, an ongoing surveillance program that has collected more than 70,000 isolates from a network of more than 200 laboratories throughout the country over the last 10 years, said Penny A. Asbell, MD, FACS, MBA, professor of ophthalmology and director of the cornea and refractive surgery service at Mount Sinai School of Medicine in New York.

This annual surveillance program began in 1996 when the fluoroquinolone levofloxacin (Levaquin, Ortho-McNeil) was introduced as a systemic agent to treat respiratory infections such as pneumonia, Dr. Asbell said. Levofloxacin ophthalmic solution 0.5% (Quixin, Vistakon Pharmaceuticals) was introduced 4 years later. Because resistance to penicillin and other systemic antibiotics had developed with widespread use, TRUST was launched to monitor for trends of emerging fluoroquinolone resistance. The TRUST program collects isolates from laboratories throughout the country and performs all testing at a single, centralized laboratory using standardized methodology.

According to Dr. Asbell, data from the ocular isolates collected in TRUST matched the overall surveillance results. Susceptibility of ocular S pneumoniae and Haemophilus influenzae to levofloxacin continues to be more than 99% and identical to the two other newer ophthalmic fluoroquinolones, gatifloxacin 0.3% (Zymar, Allergan) and moxifloxacin 0.5% (Vigamox, Alcon Laboratories). S pneumoniae susceptibility to ciprofloxacin (Ciloxan, Alcon), an older fluoroquinolone also used topically, has decreased slightly over time, however, Dr. Asbell said.

"Out of more than 1,000 ocular isolates collected between 1999 and 2006, all but one S pneumoniae and one H influenzae isolate were susceptible to levofloxacin, gatifloxacin, and moxifloxacin. That's a remarkable indication that resistance to these fluoroquinolones has not developed in these ocular pathogens," she said.

Because these newer fluoroquinolone antibiotics all work similarly, one should expect similar results, she added. But although the TRUST dataset is a valuable and publicly available source of information that may help in making antibiotic treatment decisions, Dr. Asbell cautioned that laboratory data do not necessarily reflect clinical response.

To serve the ophthalmology community better, a new initiative modeled after the TRUST study has been launched. Ocular TRUST specifically collects ocular isolates from eye centers and community hospitals across the United States and determines susceptibilities to a panel of nine antimicrobials. The first Ocular TRUST study included Staphylococcus aureus as well as S pneumoniae and H influenzae. For future studies, the pathogen panel has been expanded to include coagulase-negative staphylococci and Pseudomonas aeruginosa.