Russian Open Medical Journal (Sep 2013)
Is Haemophilus influenzae better satellite for Enterococcus faecalis?
Abstract
Background — Haemophilus influenzae can grow on blood agar media with Staphylococcus aureus which can provide factor V as it is called “Satellite phenomenon”. Objectives — In this study we tested and compared three different beta-haemolytic genus including three Staphylococcus aureus, three coagulase-negative staphylococci, and two Enterococcus faecalis strains in order to determine an alternative microorganism to be used for satellite test to identify H. influenzae conventionally. Materials and Methods — We used suspensions of H. influenzae in two different tribudities as 0.5 and 4 McFarland for each strain. Five totally-blinded reviewers examined the test results and scored both the colony sizes of H. influenzae and the diameter of the growth-zone. The sum of the scores for the colony sizes and the growth-zones were determined as “total diagnostic score” (TDS) as being between 0-6 points for each test. Results — A total of 320 test scores were analysed. The mean TDS of E. faecalis group was significantly higher than the other groups (p<0.001). In the S. aureus group, 23 (19.2%) tests had 0 points as TDS; but in enterococci group no isolates had lower scores than 3 points. In enterococci group, the rate of isolates which had 5 or 6 points was 77.5% (62/80); but in S. aureus group no isolate had higher than 4 points. Conclusions — Our study shows that using a beta-haemolytic E. faecalis strain will provide significantly more accurate results and will significantly reduce false-negative results for satellite test instead of S. aureus, which is particularly proposed to be used.
