Peptostreptococcus

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The page below is a sample from the LabCE course Medically Important Anaerobes. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

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Peptostreptococcus

Significant Peptostreptococcus species include:
  • P. anaerobius
Things to remember:
  • Nomenclature note: In recent years, several species have been reclassified to other genera. These include Anaerococcus (formerly P. prevotii), Finegoldia (species magna, formerly P. magnus), Peptoniphilus (formerly P. asacchrolyticus), Parvimonas (species micra, formerly Peptostreptococcus micros), and others.
  • Some of the Peptostreptococcus species were once included in the genus formerly known as Peptococcus.
  • Regarding clinical infections, Peptostreptococcus is the only genus characterized among the gram-positive anaerobic cocci. (Recall that microaerophilic streptococci, although clinically significant, are aerotolerant.)
Figure 27. Centers for Disease Control and Prevention. (1980). This photomicrograph of a Gram-stained specimen, reveals the presence of numerous, darkly-stained, spherical, Peptostreptococcus anaerobius bacteria, which had been cultivated on a blood agar plate (BAP) and incubated for a 48-hour time period. Note that many of these organisms had linked together for chain-like configurations. [Image]. https://phil.cdc.gov/Details.aspx?pid=4347.
Figure 28. Centers for Disease Control and Prevention. (1980). Blood agar growth medium inoculated with Peptostreptococcus anaerobius bacteria and incubated for a 48-hour time period. [Image]. https://phil.cdc.gov/Details.aspx?pid=17360.

Figure 27. Peptostreptococcus anaerobius bacteria as seen on a
Gram stain. Note the appearance of tiny cocci in chains
Figure 28. Peptostreptococcus anaerobius colonial growth on
anaerobic blood agar after 48 hours of incubation