How to identify & confirm Enterococci in Laboratory ?
They are gram positive spherical cells that occur in chains. Most of members in this group produce non haemolytic or α haemolytic colonies which are often larger than that of other streptococci. And they grow well at 10 0C and 450C, but other streptococci grow at much narrow temperature range.
Most of them causes disease in hospitalized , immune compromised patients,
They are part of normal enteric flora. but they can cause diseases in urinary tract and soft tissues adjacent to the intestinal flora. These diseases are not highly virulent and often mixed with other intestinal flora.
Always if we go for diagnosis a particular infection, we are looking for clinical background, culture characteristics, then microscopy and biochemical and serological tests.
when we look the Growth on Blood Agar, enterococci spp give small non haemolytic colonies ,but it may be α or β haemolytic as well and colonies are larger than other streptococcal colonies. ( see below video for more photos )
Growth on MacConkey Agar is important if we suspect strep spp. Magenta colour colonies can be seen on macconkey agar if it is belong to enterococcus spp
Gram positive cocci in chain can be seen if we correctly pick the enterococci colonies for smear preparation. ( see below video for photos )
similar to other strep spp this one is also catalase negative.
The especial feature of enterococcus spp is that they can survive in bile and hydrolyses esculin. therefor we need to do bile esculin test if we suspect for enterococci. Some group d strep spp can also give positivity in bile esculin test. To differentiate this we can look for growth on 6.5% NaCl. Enterococci grow in 6.5% NaCl and thus show turbidity
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