Got black swimming dots in your cell culture? Identification of Achromobacter as a novel cell culture contaminant

Abstract

Cell culture model systems are utilized for their ease of use, relative inexpensiveness, and potentially limitless sample size. Reliable results cannot be obtained, however, when cultures contain contamination. This report discusses the observation and identification of mobile black specks observed in multiple cell lines. Cultures of the contamination were grown, and DNA was purified from isolated colonies. The 16S rDNA gene was PCR amplified using primers that will amplify the gene from many genera, and then sequenced. Sequencing results matched the members of the genus Achromobacter, bacteria common in the environment. Achromobacter species have been shown to be resistant to multiple antibiotics. Attempts to decontaminate the eukaryotic cell culture used multiple antibiotics at different concentrations. The contaminating Achromobacter was eventually eliminated, without permanently harming the eukaryotic cells, using a combination of the antibiotics ciprofloxacin and piperacillin.

Figure 1

A) Phase contrast microscopy of Achromobacter contaminant in 0.5% agarose (400×) as it might look in culture under a typical microscope. B) Magnification (3200×) of Achromobacter contaminant in 0.5% agarose.