Introduction
Streptococcus (S.) intermedius is a catalase-negative, gram-positive cocci, whose most isolates are nonhemolytic with small-colony-forming species, which belongs to the Streptococcus anginosus group (SAG), which has also been referred to as the Streptococcus milleri group, which includes 3 organisms: S. anginous, S. intermedius, and S. constellatus1. This bacterial group has not been recognised as a causative pathogen. However, with the presence of certain factors, SAG could induce noninvasive infections and also invasive infections after getting into sterile body sites, such as the blood and serosal cavity, which is why it could affect the tissues and organs of several systems of the body 2.
The SAG species differ in the virulence factors that they produce. Because S. intermedius produces sialidase and hyaluronidase, which can destroy host tissues, converting them into nutrients for bacterial growth, while S. constellatus produces only hyaluronidase and S. anginous none of these 3. Probably for this reason, S. intermedius has the ability to form abscesses in several body locations. However, its virulence factors are unclear at present4. This feature gives it a unique distinction compared to other alpha-hemolytic streptococcal species and makes its management require, in most cases, surgical intervention along with antibiotic therapy 4.
S. intermedius is part of the commensal oral flora in humans, and it is frequently associated with brain and liver abscesses, but less frequently with pleuropulmonary infections including pneumonia, pleural effusion, and empyema, and in a few cases, it can also be the causal agent of lung abscesses. 1,5. Among the risk factors for these infections, smoking, alcoholism, dental diseases, chronic obstructive pulmonary disease, malignant neoplasms, liver cirrhosis, and diabetes have been described 1. Through this case report with a literature review, we discuss an acute presentation of S. intermedius lung abscess in a pregnant woman with radiological findings that make it difficult to distinguish it as a lung neoplasm, empyema or abscess.