What bacteria are Gram-positive cocci in clusters that are anaerobes?

From the Guidelines

Gram-positive cocci in clusters that are anaerobes are likely to be Peptostreptococcus or Finegoldia magna, as Staphylococcus species, which are commonly found in clusters, are generally facultative anaerobes or aerobes, not strict anaerobes.

Bacterial Characteristics

• Morphology: Gram-positive cocci in clusters are typically associated with Staphylococcus species, but since the question specifies anaerobes, we must consider other possibilities.
• Oxygen Tolerance: The fact that the bacteria are anaerobes helps to narrow down the possibilities, as Staphylococcus species are not strict anaerobes.

Relevant Evidence

The provided studies 1 focus on the diagnostic accuracy of Gram staining in predicting Staphylococcus aureus in hospital-acquired pneumonia and ventilator-associated pneumonia, but do not directly address anaerobic Gram-positive cocci in clusters.

Clinical Considerations

In clinical practice, when encountering Gram-positive cocci in clusters that are anaerobes, it is essential to consider the possibility of Peptostreptococcus or Finegoldia magna, which are both anaerobic bacteria that can exhibit this morphology. However, the provided evidence does not support a definitive answer, as it primarily focuses on Staphylococcus aureus, which is not an anaerobe.

• Peptostreptococcus: An anaerobic bacterium that can be found in various infections, including those of the skin, soft tissue, and respiratory tract.
• Finegoldia magna: A type of anaerobic bacterium that can be isolated from human infections, particularly in the context of polymicrobial infections.

From the Research

Bacteria Characteristics

• Gram-positive cocci in clusters that are anaerobes are identified as Gram-positive anaerobic cocci (GPAC) 2, 3
• GPAC are a heterogeneous group of organisms defined by their morphological appearance and their inability to grow in the presence of oxygen 2

Types of GPAC

• The most important GPAC genera isolated from human infections include:
  • Anaerococcus
  • Finegoldia
  • Parvimonas
  • Peptoniphilus
  • Peptostreptococcus 3
• Specific species of GPAC that have been studied include:
  • Peptostreptococcus magnus
  • Peptostreptococcus micros
  • Finegoldia magna
  • Anaerococcus vaginalis 2, 4

Identification and Classification

• GPAC can be identified using various methods, including:
  • Carbohydrate fermentation tests
  • Preformed enzyme kits
  • Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS)
  • 16S rRNA gene sequencing 2, 4, 5
• The taxonomy of GPAC has undergone considerable changes over the years, mainly due to the development of molecular identification methods 3

Antimicrobial Susceptibility

• GPAC have been reported to develop resistance to antimicrobial drugs 6
• Antimicrobial susceptibility patterns of GPAC vary, with some species showing high resistance rates to certain antimicrobials, such as clindamycin, tetracycline, and moxifloxacin 6
• Metronidazole, tigecycline, and meropenem have been shown to be effective against GPAC, while penicillin and amoxicillin/clavulanic acid are also effective, but with some resistance rates observed 6