Peptostreptococcus infection is rarely reported in general practice, but this genus of anaerobic bacteria can cause infections of virtually any tissue. Osteomyelitis, endocarditis, genitourinary and upper respiratory tract infections, as well as central nervous system infections, have all been described in the literature. This pathogen, being sensitive to aerobic conditions, is often underrecognized due to improper sampling and storage. Meticulous microbiological workup is crucial in order to identify Peptostreptococcus as the cause of infection.
Peptostreptococcus infection is a term encompassing a wide range of infections caused by Peptostreptococci, a large group of more than a dozen bacteria   . Peptostreptococci are the main representatives of Gram-positive anaerobic cocci and most notable species are Peptostreptococcus micros and Peptostreptococcus magnus, both being a part of the normal flora of the skin, genitourinary tract, and the oral cavity   . Although these bacterial species have been confirmed as causative agents of many types of infections, Peptostreptococcus seems to be missed in many cases, presumably because of its sensitivity to oxygen and poorly handled specimens obtained for microbiological investigations     . Nevertheless, endocarditis (involving both native and artificial valves), infections of the oral cavity, osteomyelitis, genitourinary (such as prostatitis) and respiratory tract infections, as well as central nervous system (CNS), cutaneous, and intra-abdominal infections, have all been documented by various authors      . Furthermore, they are among the most frequently described pathogens when it comes to polymicrobial infections, especially in the formation of abscesses . The clinical presentation depends on the site. Severe localized pain is typical for joint and other soft tissue infections , whereas high fever and chills, either with or without heart murmurs, are seen in cases of endocarditis .
The diagnosis of a Peptostreptococcus infection starts with a thorough clinical assessment. A detailed patient history, during which the physician must assess the presence of symptoms, their course, and progression, is highly important. The role of a proper physical examination has an equal value, particularly if endocarditis, osteomyelitis, or CNS infections are suspected. Once sufficient evidence is obtained and a presumptive diagnosis of an infection is made, microbiological testing is the cornerstone for identifying the underlying cause. Because Peptostreptococci are anaerobes, the use of swabs for obtaining a sample for evaluation can often yield a false-negative result. Aspirates, tissue specimens, or blood are much better samples for the preservation of Peptostreptococcus species during the process of microbiological identification  . Despite the fact that Peptostreptococci are commensals of the skin and the oral cavity, their presence must not be overlooked when other sites are involved in the infectious process, particularly if a polymicrobial infection is recognized. Additional methods to confirm Peptostreptococcus are described, such as enzyme assays. The introduction of molecular methods such as polymerase chain reaction (PCR) has greatly improved the overall rate of the diagnosis   .