Proficiency in detecting vancomycin resistance in enterococci among clinical laboratories in Santiago, Chile.

the basis of the following characteristics: catalase negativity, α-hemolytic gram-positive cocci forming pairs and tetrads (not chains) in broth culture; growth in the presence of 40% bile and 6.5% NaCl and ability to hydrolyze esculin; pyrrolidony l-aminopeptidase positivity, leucineaminopeptidase negativity; and production of acid from trehalose, sucrose, maltose, and lactose but not from sorbitol. Susceptibility testing by the agar dilution method showed that the isolate was susceptible to penicillin-G (MIC = 0.12 μg/ml) and vancomycin (MIC = 0.25 μg/ml). On the basis of this case and previous reports (1,2), we believe that A. viridans is a potential pathogen that can cause serious infections in immunocompromised patients. The presumed route of infection in this patient was esophageal ulcers. Clinical microbiologists should pay close attention to α-hemolytic, catalasenegative streptococci recovered from sterile body sites that form tetrads rather than chains on Gram stain.