What would you conclude if an inoculated plate had colonies between the streak lines? What would you conclude if an inoculated plate had colonies between the streak lines? Solution It depends, if there is no growth or colony appearance on streak line and only it shows growth in between streak line then it is certainly a contamination.If there are colonies on streak line and not resemble with the streak culture then also it is a contamination but there can be a chance that colony appears due to some fault in streaking procedure and the inoculum drops between the streak line..