Specific Identification of Staphylococcus aureus by Staphychrom II, a Rapid Chromogenic Staphylocoagulase Test

Abstract

We compared the performance of Staphychrom II (International Microbio, Signes, France), a rapid (2-h) chromogenic staphylocoagulase test that uses human prothrombin and protease inhibitors, with those of the reference tube coagulase test (TCT) and the latex agglutination test (LAT) Slidex Staph Plus for the rapid identification of S. aureus. Prospective evaluation with 293 fresh clinical isolates yielded sensitivities, specificities, and predictive and negative predictive values of 98.1, 100, 100, and 95.1%, respectively, for the Staphychrom II test; 98.6, 98.7, 99.6, and 96.3%, respectively, for LAT; and 97.6, 98.7, 99.5, and 93.9%, respectively, for TCT. The perfect specificity of the Staphychrom II test was confirmed by testing 193 collection strains selected because of their potential testing pitfalls. The Staphychrom II test was positive for 90% of the 215 S. aureus strains tested after only 1 h of incubation. The Staphychrom II test was as sensitive as the reference TCT and was 100% specific.Rapid identification of Staphylococcus aureus is a major priority for clinical microbiologists. The tube coagulase test (TCT) is the reference method for distinguishing S. aureus and rare coagulase-positive non-S. aureus staphylococci (e.g., S. intermedius) from coagulase-negative staphylococci. However, this test requires 18 to 24 h of incubation and is not perfectly reliable (1,13,16,18). Agglutination tests with either erythrocytes or latex particles coated with various ligands may lack sensitivity, notably, for methicillin-resistant S. aureus (MRSA), and may also lack specificity for non-S. aureus staphylococci, such as S. lugdunensis, S. schleiferi, and S. intermedius (3,8,14,15).In the present study we evaluated Staphychrom II (International Microbio, Signes, France), a rapid (2-h) chromogenic staphylocoagulase test which specifically detects S. aureus, and compared the results obtained with those obtained by a reference TCT (Becton Dickinson, Le Pont de Claix, France) and the latex agglutination test (LAT) Slidex Staph Plus (bioMérieux, Marcy l'Etoile, France). The tests were compared prospectively with 293 clinical isolates in two clinical laboratories and retrospectively with 193 typical and atypical collection strains chosen because of their potential testing pitfalls. MATERIALS AND METHODS Test organisms. From March 2002 to May 2002, a total of 293Staphylococcus isolates were prospectively tested at Bellevue Hospital, Saint Etienne, France (n ϭ 149) or Debrousse Hospital, Lyon, France (n ϭ 144). They comprised 215 S. aureus isolates (43 MRSA strains and 172 methicillin-susceptible strains) and 78 non-S. aureus staphylococci. The 78 non-S. aureus isolates comprised S. capitis (n ϭ 14), S. caprae (n ϭ 3), S. cohnii (n ϭ 1), S. epidermidis (n ϭ 49), S. haemolyticus (n ϭ 3), S. hominis (n ϭ 4), S. simulans (n ϭ 2), and S. warneri (n ϭ 2). The strains were isolated from the following clinical specimens: pus (n ϭ 85), respiratory tract (n ϭ 83), nose (n ϭ 32), blood (n ϭ 26), catheter (n ϭ 22), urine (n ϭ 13), sto...

Staphylococcus aureuscoagulases are exploitable yet stable public goods in clinically relevant conditions

“…This dense fibrous clot is further strengthened by the cross-linking activity of the transglutaminase factor XIIIa, a fibrin-stabilizing enzyme that is nonproteolytically activated by the ProT • vWbp • fXIII complex (22). Despite Coa-and vWbp-mediated clots being vital for S. aureus during infection, phenotypes of low expression levels, loss-of-function mutations, and/or complete deficiency of coagulases are observed among clinical isolates (23)(24)(25)(26)(27)(28)(29)(30). In this sense, we propose that secretion of coagulases is a defining feature of S. aureus fitness during infection, but it is also a costly and potentially exploitable trait-a public good.…”

Persistence and progression of staphylococcal infection in the presence of public goods

“…Earlier work highlighted the stages of staphylococcal abscess formation and the role that sortase A-anchored surface proteins and coagulases play 17,18 . However, phenotypes of low expression levels, loss-of-function mutations, and/or complete deficiency of coagulases are observed among clinical isolates [19][20][21][22][23][24][25] . Here, we dissect the relative contribution of coagulases from a microbial interactions perspective-whether or not they can function as public goods in mixed S. aureus communities of coagulase-positive and -negative isogenic strains during systemic spread and abscess formation.…”

Whole Genome Molecular Characterization of Methicillin Resistant Staphylococcus aureus Isolated From Clinical Settings in Lebanon. (c2022)

“…Rapid and effective laboratory routine tests have been used for the identification of S. aureus, such as the tube coagulase test (TCT) that is used to distinguish the coagulase positive S. aureus from coagulase-negative staphylococci (CoNS) (Fonsale et al, 2004). The free coagulase secreted S. aureus reacts with the coagulase reacting factor in human/animal plasma forming staphylothrombin that converts fibrinogen to fibrin leading after few hours of incubation to plasma clotting (Lourdes & Kunha, 2018).…”