Application of DNA probes to antimicrobial susceptibility testing of Legionella pneumophila.
The commercial availability of a DNA probe assay for the detection of Legionella (Gen-Probe Incorporated, San Diego, CA) provides a unique opportunity to investigate the application of this technology to antibiotic susceptibility testing of L. pneumophila. We examined the ability of erythromycin, rifampin, and ciprofloxacin to kill L. pneumophila in buffered ACES-yeast extract broth (YEB). The test organism was incubated for a total of 96 hr in the presence of 10 micrograms/ml erythromycin, 1 micrograms/ml rifampin, or 1 micrograms/ml ciprofloxacin. Growth was monitored at 24-hr intervals by quantitative plating and the DNA probe assay. The correlation between organism concentration [colony-forming units (CFU) per ml] and DNA probe activity (counts per min) was excellent (r = 0.97). The percent decrease in CFU/ml at 96 hr relative to control counts was greater than 99% for erythromycin, rifampin, and ciprofloxacin. The percent decrease in CPM at 96 hr versus control was 87% for erythromycin, 89% for rifampin, and 93% for ciprofloxacin. This data documents a novel application of DNA probe technology, which may be useful in future studies of in vitro susceptibility of Legionella to various agents.
Reznicek
M
M
Department of Pathology, University of Iowa Hospitals and Clinics, Iowa City.
Bale
M
M
Pfaller
M
M
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002939:Ciprofloxacin / Q000494:pharmacology; D015169:Colony Count, Microbial; D015342:DNA Probes; D004917:Erythromycin / Q000494:pharmacology; D006801:Humans; D007875:Legionella / Q000187:drug effects* / Q000254:growth & development; D008826:Microbial Sensitivity Tests / Q000379:methods*; D012293:Rifampin / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D015342:DNA Probes; D002939:Ciprofloxacin; D004917:Erythromycin; D012293:Rifampin