Background: Aerococcus viridans is an aerobic, α-hemolytic, Gram positive cocci with a strong tendency to from tetrads. It has been isolated from patients with urinary tract infections, endocarditis,
bacteremia, and pneumonia.Case Report: We report a case of Aerococcus viridanspneumonia in a newborn who was receiving prophylactic ampicillin and netilmicin treatment for minimally respiratuar distress syndrome. Since respiratory functions were also aggraveted, the quantitative culture of endotracheal aspirate fluid revealed 105 coloni forming unit/ml alpha hemolytic streptococcus. This microorganism was resistant to all penicillin minimal inhibitory concentrations (MIC) values and highly resistantto claritromycin (MIC values ?2 µg/ml) and cefotaxime (MIC values ?32 µg/ml) and intermediate resistant to meropenem (MIC values ?2 µg/ml). It was suspectible to clindamycin (MIC values ?0.16µg/ml) and vancomycin (MIC values ?1µg/ml). This case was treated with teicoplanin successfully.Although A. viridans is rarely involved in pediatric infections, it should be considered as a causitive agent of bacteremia, meningitis or pneumonitis in newborns and should not be overlooked as a contaminant, if the clinical symptoms are associated.Conclusions: To our knowledge this is the third reported case of infection due to a penicillin resistant strain, and the first reported case of infection due to a multi-drug resistant strain.

Keywords: nosocomial infection, multi-drug resistance, Aerococcus viridans, newborn, pneumoniae