Coagulase-negative staphylococci in outpatient routines: the implications of switching from CLSI to BrCAST/EUCAST guidelines

Abstract

Coagulase-negative staphylococci (CoNS) are frequently isolated in clinical specimens and are important reservoirs of resistance genes. In 2019, the Brazilian government set the BrCAST/EUCAST (Brazilian Committee on Antimicrobial Susceptibility Testing) guidelines as the national standard, resulting in changes in the interpretation of CoNS susceptibility tests. From outpatients, disk-diffusion susceptibility of 65 CoNS cultures were evaluated and compared using classification criteria from both CLSI and BrCAST/EUCAST. The isolates were identified using matrix assisted laser desorption ionization-time of flight (MALDI-TOF), and the presence of the mecA gene was determined. The most prevalent species were Staphylococcus saprophyticus (32.3%), S. haemolyticus (18.5%), and S. epidermidis (9.2%). Almost perfect agreement was seen between the guidelines, except concerning oxacillin and gentamicin, and the prevalence of multidrug resistant isolates increased with the use of BrCAST/EUCAST. Of all, 15 (23.1%) isolates, mainly S. epidermidis and S. haemolyticus, were positive for the mecA gene, and only three were detected when using CLSI or BrCAST/EUCAST disk-diffusion screening. This, using either guideline, could reveal the difficulty of determining oxacillin resistance. Using warning zones or molecular methods might well be indicated for CoNS. In conclusion, adoption of the BrCAST/EUCAST guidelines will result in certain artificial changes in epidemiological susceptibility profiles, and clinicians and institutions should be aware of the possible implications.

Molecular Structure and Antibacterial Activity of Degradation Products from Cephalexin Solutions Submitted to Thermal and Photolytic Stress

“…Cod. WDCM 00012) was determined by the broth microdilution method, following the recommendations of the Brazilian Committee for Antimicrobial Susceptibility Tests (BrCAST/EUCAST) [44] . Briefly, certified reference discs were dissolved in Mueller Hinton broth (M−H) and left to grow overnight at 35 °C under mild stirring.…”

“…WDCM 00012) was determined by the broth microdilution method, following the recommendations of the Brazilian Committee for Antimicrobial Susceptibility Tests (BrCAST/ EUCAST). [44] Briefly, certified reference discs were dissolved in Mueller Hinton broth (MÀ H) and left to grow overnight at 35 °C under mild stirring. Aliquots from this suspension were seeded on tryptic soy agar plates, left to grow for 48 h, and colonies harvested from the plates were transferred into fresh MÀ H broth at amounts of 1.5 × 10 8 CFU/ml (0.5 McFarland).…”