Penicillinase production and in vitro susceptibilities of Staphylococcus lugdunensis

Of 59 clinical isolates of Staphylococcus lugdunensis, 76% were beta-lactamase negative, with penicillin G MICs of less than or equal to 0.13 microgram/ml, and 24% were beta-lactamase positive, with penicillin MICs of greater than or equal to 0.5 microgram/ml. Bimodal distributions were observed also with ampicillin, ampicillin-sulbactam, and amoxicillin-clavulanate. All strains were susceptible to oxacillin, cephalothin, gentamicin, rifampin, and vancomycin; 98% were erythromycin susceptible.