Optimization method for identifying Actinomyces spp. and related species : Evaluating if antibiotic discs on agar plates facilitates identification of Actinomyces spp. and related species in a mix of bacterial microbiota
2024
Bergqvist, Hilda
Actinomycosis is an infrequent bacterial infection involving Actinomyces spp and related organisms which may occur at many body sites. It can also be found in the microbiota. Actinomyces spp are described as gram-positive bacilli whereas some species grow strictly anaerobically and some facultative. Culturing is a standardized method when suspecting actinomycosis and can be a diagnostic challenge because of inhibition of microbiota and slow growth. Enriched agar plates are used when culturing fastidious bacteria and may be more selective when including antibiotics. The aim of this project was to evaluate if using antibiotic disc facilitates identification of Actinomyces spp when mixed with microbiota. A mix of microbiota was made by pooling together several species. The susceptibility of different isolates and microbiota was analysed using antibiotic discs to determine which disc to use in a trial. A trial was done by inoculating the isolates with the microbiota on agar plates, dispensing ciprofloxacin, and trimethoprim discs. A control group without antibiotic discs were also tested. Results showed variance for most isolates susceptibility. No disc performed superior in the trial, but ciprofloxacin on FAA plates incubated anaerobically gave slightly higher recovery. Both discs facilitated identification of some isolates by supressing much microbiota. Considering that the isolates had varying susceptibility it may be problematic to find one common disc. This study has given new insights on what may facilitate identification. Further studies are needed to determine if antibiotic discs could facilitate identification of Actinomyces and needs testing on clinical samples using larger sample size.
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