What are the common bacteria responsible for mouth infections?

Common Bacteria Responsible for Mouth Infections

The most common bacteria responsible for mouth infections include Viridans streptococci, Prevotella species, Peptostreptococcus, Fusobacterium, and Staphylococcus species, with specific prevalence varying by infection type. 1

Primary Bacterial Pathogens by Prevalence

Aerobic Bacteria

• Viridans streptococci (64% of orofacial infections) 2
  • Includes Streptococcus salivarius, Streptococcus gordoni, and Streptococcus mitis groups
• Staphylococcus species
  • S. aureus and S. epidermidis commonly found in oral infections
  • Present in 40% of human bite wound infections 1
• Neisseria species (common in healthy oral flora) 1
• Haemophilus species 1

Anaerobic Bacteria

• Prevotella species (43% of orofacial infections) 2
  • Present in 12-38% of peritonsillar abscesses 3
  • Produce β-lactamases, making them resistant to penicillin 3
• Peptostreptococcus species (26% of orofacial infections) 2
  • Found in 17-27% of tonsil abscesses 3
• Fusobacterium species (14% of orofacial infections) 2
  • Present in approximately 38% of tonsil abscesses 3
• Porphyromonas species (7% of orofacial infections) 2
• Bacteroides species 4

Bacteria by Specific Oral Infection Types

Dental/Periodontal Infections

• Primary pathogens: Viridans streptococci, Prevotella, Fusobacterium, Peptostreptococcus 2
• Dental caries: Predominantly Gram-positive facultative anaerobes, especially mutans streptococci 5
• Periodontal disease: Predominantly Gram-negative anaerobes including Prevotella, Porphyromonas, and Fusobacterium 5

Tonsil/Peritonsillar Abscesses

• Group A Streptococcus (approximately 45% of cases) 3
• Fusobacterium species (38% of cases) 3
• Streptococcus milleri group (27% of cases) 3
• Prevotella species (12-38% of cases) 3
• Peptostreptococcus species (17-27% of cases) 3

Oral Bite Wounds (Human)

• Streptococcus species (50% of human bite wounds) 1
• Staphylococcus aureus (40% of human bite wounds) 1
• Eikenella corrodens (30% of human bite wounds) 1
• Anaerobes: Fusobacterium, Prevotella, Bacteroides, Porphyromonas 1

Age-Related Variations

• Infants (edentulous): Lower incidence of anaerobes overall 4
• Children: Infections more commonly from tonsil and lymphatic sources 6
• Adults:
  • Infections more commonly from odontogenic sources 6
  • Oral flora becomes more diverse with age 1
  • Anaerobes invariably present, especially in gingival sulcus 4

Clinical Implications

• Antimicrobial resistance is an increasing concern, particularly with inappropriate antibiotic use 2
• Most orofacial infection isolates remain sensitive to amoxicillin-clavulanate, amoxicillin alone, clindamycin, and levofloxacin 2
• Increasing resistance to erythromycin has been observed 2
• Many Prevotella strains produce β-lactamases, making them resistant to penicillin and first-generation cephalosporins 3

Sampling Considerations

• Proper anaerobic collection techniques are essential to avoid false negatives, particularly for Prevotella species 3
• Swabs are often not the specimen of choice for many oral infections 1
• Gram stain should be performed to assess for inflammation indicators and contamination 1

Treatment Approach

For severe oral infections requiring antibiotics:

• First-line options: Amoxicillin-clavulanate, ampicillin-sulbactam, or clindamycin 3
• For penicillin-allergic patients: Clindamycin or metronidazole plus coverage for aerobes 3
• Surgical drainage is essential alongside appropriate antibiotic therapy for abscesses 3

Understanding the complex polymicrobial nature of oral infections is crucial for effective treatment and prevention of serious complications such as bacteremia, which can lead to infective endocarditis in susceptible individuals 1.