Evaluation of CHROMagar Staph. aureus, a new chromogenic medium, for isolation and presumptive identification of Staphylococcus aureus from human clinical specimens

• Published in: Journal of clinical microbiology Vol. 38; no. 4; pp. 1587 - 1591
• Main Authors: GAILLOT, O, WETSCH, M, FORTINEAU, N, BERCHE, P
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for Microbiology 01-04-2000
• Subjects: Bacterial diseases; Bacteriological methods and techniques used in bacteriology; Bacteriological Techniques; Bacteriology; Biological and medical sciences; Chromogenic Compounds - metabolism; Coagulase - metabolism; Culture Media; Evaluation Studies as Topic; Fundamental and applied biological sciences. Psychology; Human bacterial diseases; Humans; Infectious diseases; Medical sciences; Microbiology; Predictive Value of Tests; Reagent Kits, Diagnostic; Sensitivity and Specificity; Staphylococcal Infections - diagnosis; Staphylococcal Infections - microbiology; Staphylococcal infections, streptococcal infections, pneumococcal infections; Staphylococcus aureus; Staphylococcus aureus - classification; Staphylococcus aureus - growth & development; Staphylococcus aureus - isolation & purification; Human; Culture medium; Identification; Species specificity; Infection; Chromogenic reagent; Bacteriosis; Bacteria; Micrococcales; Micrococcaceae; Diagnosis; Staphylococcal infection; Staphylococcus aureus
• ISSN: 0095-1137; 1098-660X
• DOI: 10.1128/JCM.38.4.1587-1591.2000

CHROMagar Staph. aureus (CSA) is a new chromogenic medium for presumptive identification of Staphylococcus aureus as mauve colonies after 24 h of incubation. We conducted a preliminary study with 100 S. aureus and 45 coagulase-negative Staphylococcus (CoNS) stock isolates plated on CSA. All S. aureus isolates yielded mauve colonies after 24 h of incubation at 37 degrees C, while CoNS isolates grew as blue, white, or beige colonies. Culture on CSA was then prospectively compared to a conventional laboratory method, i.e. , culture on 5% horse blood agar (HBA), catalase test, and latex agglutination test (HBA-catalase-latex), for isolation and presumptive identification of S. aureus from 2,000 consecutive clinical samples. Among the 310 S. aureus isolates recovered by at least one of the two methods, 296 grew as typical mauve colonies on CSA, while only 254 yielded catalase-positive, latex-positive colonies on HBA. The sensitivity of CSA was significantly higher than that of the conventional method (95.5 and 81.9%, respectively; P < 0.001) and allowed the recovery of important clinical isolates that were undetected on blood agar. The specificities of the two methods were not significantly different, although that of CSA was slightly higher (99.4% versus 98.9% for HBA-catalase-latex; P = 0. 08). On the basis of its excellent sensitivity and specificity, ease of identification of positive colonies, and absence of complementary testing, CSA can be recommended as a routine plating medium for presumptive identification of S. aureus in clinical specimens.