The parotid gland is the salivary gland most commonly affected by inflammation. However, infection of the salivary glands can occur in any of the glands. The most common pathogens associated with acute bacterial infection are Staphylococcus aureus and anaerobic bacteria. The predominant anaerobes include: anaerobic Gram negative bacilli (eg, pigmented Prevotella and Porphyromonas); Fusobacterium spp; and Peptostreptococcus spp. In addition, Streptococcus spp (including Streptococcus pneumoniae) and aerobic and facultative Gram-negative bacilli (including Escherichia coli) have been reported. Aerobic and facultative Gram-negative bacilli are often seen in hospitalized patients. Organisms less frequently found are Haemophilus influenzae, Treponema pallidum, Bartonella henselae, and Eikenella corrodens. Mycobacterium tuberculosis and atypical mycobacteria are rare causes of infection. The choice of antibiotics should be guided by identification of the etiologic agent.