Liver Abscess due to Streptococcus constellatus in an Immunocompetent Adult: A Less Known Entity.

BACKGROUND: Pyogenic liver abscesses (PLAs) are an uncommon, but potentially life threatening infection. We report a case of PLA due to Streptococcus constellatus, a member of the Streptococcus anginosus group (SAG) bacteria, commonly found as commensals of the oropharyngeal, gastrointestinal and genitourinary flora.

CASE: The patient, a 42-year-old man with no premorbidities, non-smoker and non-alcoholic, presented to our hospital with high-grade fever associated with chills and rigors and right upper quadrant pain of one month duration. Culture of the ultrasound-guided liver aspirate yielded a pure growth of S. constellatus subspecies constellatus identified by conventional biochemical tests. In a standard antimicrobial disk-diffusion test, the isolate was susceptible to cefepime, cefotaxime, ceftriaxone, vancomcyin, levofloxacin, clindamycin and linezolid. Treatment with parenteral ceftriaxone alongwith appropriate surgical management led to resolution of the abscess with no recurrence of infection at three months follow-up.

CONCLUSIONS: The pathogenic potential of SAG has generally been disregarded because of the commensal nature of these microorganisms; however, streptococci belonging to this group have been increasingly reported as relevant pathogens in abscesses and blood cultures. An underlying condition, such as diabetes, cirrhosis or cancer or some medical manipulation, such as dental extraction, acupuncture, or hemorrhoidectomy is associated with the majority of patients with SAG abscess. However, the present case highlights the need to include S. constellatus and other members of the SAG while investigating for etiology of PLA, even in immunocompetent adults.