International Multicenter Evaluation of Latex Agglutination Tests for Identification of Staphylococcus aureus

Abstract

A newly marketed rapid agglutination kit for the identification ofStaphylococcus aureus is one of the most frequently isolated pathogens in clinical specimens (8). In fact, S. aureus is currently the most common cause of infections in hospitalized patients (1). Misidentification of S. aureus as coagulase-negative staphylococcus (CoNS) can result in a costly search for other pathogens or unwarranted broad-spectrum empiric antimicrobial coverage (11). Although the tube coagulase test for the detection of free coagulase is generally considered the standard test for differentiating S. aureus from CoNS, the timeconsuming nature of the test (incubation for 4 to 24 h is required) often forces clinical microbiology laboratories to use more rapid alternatives. The slide coagulase test, which detects bound coagulase (clumping factor) is rapid (Ͻ1 min), but 10 to 15% of S. aureus strains may yield a false-negative result (7). Through the years many manufacturers have developed commercial agglutination kits for the rapid identification of S. aureus. The earliest of these tests consisted of erythrocytes sensitized with fibrinogen for the detection of clumping factor. Thereafter, a second generation of products was marketed, which employed coated latex particles and/or sensitized sheep erythrocytes to identify S. aureus by the simultaneous detection of clumping factor and protein A (12). Initially, these tests were reported to be very accurate, but later reports documented false-negative results among methicillin-resistant S. aureus (MRSA) strains (4,8,9,13,14). It was hypothesized that these false-negative MRSA strains do not expose clumping factor or protein A on their surface, which might be explained by the presence of a large amount of capsular polysaccharides masking other cell wall structures. The observation that capsular polysaccharide serotype 5 predominated among MRSA isolates which were not identified by rapid agglutination methods offered a target for improvement of the available tests (4). Third-generation tests were developed, which incorporated antibodies against capsular polysaccharides or antibodies against group-specific antigens on the S. aureus cell surface (4,5,12).In this international multicenter study, a newly marketed rapid latex agglutination test, Slidex Staph Plus (bioMérieux, Marcy-l'Etoile, France), was compared to two other latex agglutination tests of the same generation, Staphaurex Plus (Murex Diagnostics Ltd., Dartford, England) and Pastorex Staph-Plus (Sanofi Diagnostics Pasteur, SA, Marnes-La-Coquette, France). All three tests detect clumping factor and staphylococcal protein A, in addition, Slidex Staph Plus and Staphaurex Plus detect group-specific antigens on the S. aureus cell surface, and Pastorex Staph-Plus detects capsular polysaccharides.(This study was presented at the 10th European Congress of Clinical Microbiology and Infectious Diseases, Stockholm, Sweden, 2000.) MATERIALS AND METHODSThe study was conducted at three clinical microbiology laboratories in three European countries...

Evaluation of Hiaureus TM Coagulase Confirmation Kit in Identification of Staphylococcus aureus

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Methods for Identification of Staphylococcus aureus Isolates in Cases of Bovine Mastitis

“…Several rapid identification tests for S. aureus are commercially available and have been extensively validated for use in human medicine (8,26). They could be very helpful for the identification of S. aureus in cultures from milk samples but seem not to be used frequently for this purpose.…”

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

“…The Slidex Staph Plus test (bioMérieux) is an LAT that simultaneously detects clumping factor, protein A, and capsular polysaccharides on the S. aureus cell surface (20). It was used according to the recommendations of the manufacturer.…”