Identification and detection of methicillin resistance in non-epidermidis coagulase-negative staphylococci

• Published in: The Brazilian journal of infectious diseases Vol. 12; no. 4; pp. 316 - 320
• Main Authors: Secchi, Carina, Antunes, Ana Lúcia Souza, Perez, Leandro Reus Rodrigues, Cantarelli, Vlademir Vicente, d'Azevedo, Pedro Alves
• Format: Journal Article
• Language: English
• Published: Brazil Contexto 01.08.2008; Brazilian Society of Infectious Diseases; Elsevier
• Subjects: Anti-Bacterial Agents - pharmacology; Bacterial Proteins - analysis; Bacterial Proteins - genetics; cefoxitin; Coagulase; Coagulase-negative Staphylococcus; Diseases; Disk Diffusion Antimicrobial Tests - methods; Distribution; Drug resistance in microorganisms; Genetic aspects; Health aspects; Humans; Immunocompromised host; INFECTIOUS DISEASES; mecA gene; Medical examination; Methicillin Resistance - genetics; oxacillin; Penicillin-Binding Proteins; Reproducibility of Results; Risk factors; Sensitivity and Specificity; Staphylococcal infections; Staphylococcus - drug effects; Staphylococcus - enzymology; Staphylococcus - genetics; Staphylococcus - isolation & purification; susceptibility diagnostic; Brazil; susceptibility diagnostic; cefoxitin; Coagulase-negative Staphylococcus; oxacillin; mecA gene
• ISSN: 1413-8670; 1678-4391; 1678-4391
• DOI: 10.1590/S1413-86702008000400012

The NCCLS (2004) presented a new methodology to detect, by disk-diffusion agar, oxacillin-resistance using a cefoxitin disk. We identified coagulase-negative staphylococci (SCoN) to the species level and compared the use of cefoxitin disks (30 microg) with oxacillin disks (1 microg), agar dilution (minimum inhibitory concentration of oxacillin) and mecA gene detection in isolates of coagulase-negative bacteria other than Staphylococcus epidermidis (SCoNne). A total of 238 SCoNne was evaluated; oxacillin-resistance (the mecA gene) was detected in 71% of the isolates. All methods gave 100% sensitivity, based on presence of the mecA gene. The specificity of the cefoxitin disk was 100%, while the oxacillin disk gave a specificity of 91% and agar dilution oxacillin gave a specificity of 88%. We conclude that the cefoxitin disk is an efficient test, and it is an easy method for use in clinical laboratories to detect oxacillin-resistance in staphylococci.