Direct detection of groups A, C and G streptococci in clinical specimens by a trivalent colour test

Abstract

A simple trivalent colour test, developed for the rapid detection and identification of streptococci belonging to Lancefield groups A, C and G, was evaluated for sensitivity and specificity with cultures and when directly used with wound and throat swabs. In tests performed on cultures, all of 94 group A, 78 group C and 94 group G cultures were correctly identified. In direct tests on wound swabs, 49 of 52 group A, 17 of 19 group C and 48 of 51 group G streptococci were detected and correctly identified; no false positives were observed. With throat swabs from pharyngitis patients 34 of 36 group A, 3 of 6 group C and 5 of 8 group G streptococci gave positive results. Almost 10% of these swabs gave false positive reactions with the group C component of the test system. Samples taken from uninfected individuals indicated that the false positives were probably associated with blood group A. The test system gives rapid and reliable results with streptococcal cultures, but when directly applied to clinical samples the results must be interpreted with caution, particularly if the patient's blood group is not known.

Use of rapid diagnostic techniques in ICU patients with infections

“…The steps recommended for the early diagnosis of a SSTI by Streptococcus pyogenes are: direct Gram staining of skin biopsies, tissues, fascia, muscle, purulent exudate or joint aspirates and the rapid detection of capsule and protein antigens in skin and/or tissues using available kits that show a Se of 60% to 91% and a Sp of 85% to 98% [ 142 ]-[ 144 ].…”

Current challenges in acute bacterial skin infection management

“…SSTI caused by Streptococcus pyogenes can be diagnosed through various methods such as direct Gram staining of skin samples, detection of capsule and protein antigens with commercial kits, or PCR on swab specimens [31,32 ▪ ,33 ▪ ]. These tests offer a sensitivity and specificity of 100 and 99.5%, respectively.…”

Evaluation of the Oxoid Dryspot Streptococcal Grouping Kit for Grouping Beta-Hemolytic Streptococci

“…In the second investigation, 153 clinical isolates were tested; 60 of these had also been tested in the first investigation. The strains from the culture collections consisted of groups (4)(5)(6). The clinical strains were confirmed as catalase-negative, gram-positive cocci, and their Lancefield groups were determined with Oxoid latex streptococcal grouping reagents, but the results were not revealed to me until the end of the investigation.…”