The following is a summary of data from the 47th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) meeting in Chicago, which ended Thursday.

• Advanced Life Sciences Holdings Inc., of Woodridge, Ill., reported data showing the in vitro activity of cethromycin against key susceptible and resistant pathogens involved in community-acquired pneumonia. Findings demonstrated that the antibiotic maintained good in vitro potency against telithromycin-resistant Staphylococcus pneumonia isolates, all other S. pneumonia populations, and all Haemophilus influenza isolates studied. The company also reported results from a preclinical study testing cethromycin against lethal inhalation anthrax, showing that all animals treated with cethromycin survived, with only one of 10 demonstrating abnormal hematologic parameters following antibiotic cessation.

• Arpida Ltd., of Basel, Switzerland, reported data from several preclinical and clinical studies of iclaprim, a late-stage investigational agent that has exhibited activity against Gram-positive bacteria, including those resistant to current therapies. Results from the first pivotal Phase III trial showed iclaprim had high microbiological eradication rates against major complicated skin and skin structure infections, comparable with linezolid. In another study, iclaprim exhibited rapid bactericidal activity against several clones of methicillin-resistant Staphylococcus aureus predominant in community and hospital infections. Iclaprim's post-antibiotic effect was comparable to other agents in that study.

• Optimer Pharmaceuticals Inc., of San Diego, reported in vitro data showing that ulifloxacin, the active metabolite of the firm's prodrug antibiotic candidate prulifloxacin, exhibited two to four times greater activity than ciprofloxacin. In another study, OP-1118, the major metabolite of Optimer's OPT-80 investigational compound, demonstrated selective in vitro antimicrobial activity against Clostridium difficile and was as active in vitro as vancomycin. OPT-80 currently is being investigated in two Phase III trials for the treatment of C. difficile-associated diarrhea.