title: Mucoid and pigmentation characters can be suppressed by non-anti-Pseudomonas aeruginosa antibiotics in cystic fibrosis: a report of promising preliminary results.
abstract: In an effort to develop new strategies, the authors are exploring the hypothesis that non-anti-Pseudomonas aeruginosa antibiotics can affect some major virulence factors in cystic fibrosis P. aeruginosa. Recent samples (127) of P. aeruginosa isolated from the sputum of cystic fibrosis patients and manifesting a mucoid growth were stored at -70 degrees C until experimentation. The mucoid character was retested after thawing and one 24-h in-vitro passage at 37 degrees C onto 100-mm blood agar plates to prepare a bacterial suspension for inoculation (Steers or MIC-2000 plus replicator) and cultivation (48 h, 37 degrees C) onto different 100-mm or 150-mm Mueller-Hinton agar plates containing either no antibiotics or antibiotics alone, and antibiotic combinations without presumed anti-P. aeruginosa activity. Some isolates (49, 38.6%) of P. aeruginosa expressed again the mucoid character on antibiotic-free Mueller-Hinton agar and growth was prevented by antibiotics in a number of them: 7 with doxycycline (16.0 micrograms/ml), 2 with rifampicin (16.0 micrograms/ml), 6 with roxithromycin-sulfamethoxazole (16.0-304.0 micrograms/ml) and 23 with trimethoprim-sulfamethoxazole. In the remaining evaluable isolates, the mucoid was modified towards the rough character in 36 out of 42 with doxycyline, 36 out of 47 with rifampicin, 31 out of 43 with roxithromycin-sulfamethoxazole and 20 out of 26 with trimethoprim-sulfamethoxazole. In parallel, the pigmentation was lost in the presence of antibiotics in those P. aeruginosa isolates having manifested this character on Mueller-Hinton agar. These results suggest that non-anti-P. aeruginosa antibiotics can modify the in vitro markers of virulence in cystic fibrosis P. aeruginosa and that they merit further investigation.
authors.affiliation: Department of Microbiology, St Justine's Hospital, Montreal, Quebec, Canada.
authors.forename: J R
authors.initials: JR
authors.lastname: Lapointe
authors.forename: C
authors.initials: C
authors.lastname: Bourget
authors.forename: L
authors.initials: L
authors.lastname: Lafleur
authors.forename: J
authors.initials: J
authors.lastname: Lagacé
authors.forename: S
authors.initials: S
authors.lastname: Montplaisir
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003550:Cystic Fibrosis / Q000382:microbiology*; D004318:Doxycycline / Q000494:pharmacology; D004338:Drug Combinations / Q000494:pharmacology; D006801:Humans; D007933:Leucomycins / Q000494:pharmacology; D010858:Pigmentation / Q000187:drug effects; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000302:isolation & purification / Q000472:pathogenicity; D012293:Rifampin / Q000494:pharmacology; D013420:Sulfamethoxazole / Q000494:pharmacology; D014295:Trimethoprim / Q000494:pharmacology; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D014774:Virulence
chemical_list: D000900:Anti-Bacterial Agents; D004338:Drug Combinations; D007933:Leucomycins; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D014295:Trimethoprim; D013420:Sulfamethoxazole; D004318:Doxycycline; D012293:Rifampin