New method for detecting slime production by coagulase negative staphylococci.

TLDR

The study compared a new Congo red agar method, using brain‑heart infusion broth with 5 % sucrose and Congo red stain, to the standard Christensen method for detecting slime production in 124 coagulase‑negative staphylococci isolates. The Congo red method showed complete agreement with Christensen in 107 cases, correctly identified one strain missed by Christensen, and proved rapid, sensitive, reproducible, and free from inter‑batch media variation.

Abstract

An alternative method for detecting the production of slime by coagulase negative staphylococci was compared with the routinely used Christensen method on 124 isolates of coagulase negative staphylococci from carriage sites, blood cultures, and infected peritoneal dialysis fluids. The alternative method requires the use of a specially prepared solid medium--brain heart infusion broth, supplemented with 5% sucrose, and Congo red stain. Of the 124 tests, there was complete agreement between methods in 107 and only one strain was clearly negative by Christensen's method while positive on Congo red agar. The Congo red method is rapid, sensitive, and reproducible and has the advantage that colonies remain viable on the medium. It is also not subject ot interbatch variation of media which sometimes affects the reproducibility of the Christensen method.