neutropenia
oral mucositis
irradiation to the oral cavity
antibiotic prophylaxis with trimethoprim-sulfamethoxazole or fluoroquinolones
intravenous hyperalimentation
high dose chemotherapy
Viridans-Group Streptococci
Streptococcus Genus
Staphylococcus
Staphylococcus aureus
Staphylococcus epidermidis
Methicillin-Sensitive Staphylococcus Aureus 
Streptococcus pneumoniae
Streptococcus anginosus