176. Streptococcus intermedius: A Study of 107 Isolates

Abstract

Background Streptococcus anginosus (SA), Streptococcus constellatus (SC), and Streptococcus intermedius (SI) constitute the S. anginosus group (SAG). The majority of SI reports are single or few cases and small series. In a 2017 study of 263 cases of SAG only 36 (13.7%) were identified as SI, responsible for pyogenic nonbacteremic infections. Another study (2001) found 14 SI out of 122 SAG isolates of which 12 were from abscesses. In some reports, SI was only identified after molecular sequencing as original culture reports were negative. We present results of the analysis of 335 SAG isolates during a 3-year period with much higher numbers of SI (107) 32%, and bacteremia (17) 16% than previously reported. SI isolates exceeded S. constellatus (77) 23% with SA being the majority (45%)151. Our study disclosed previously unreported sites of infection and differences in the type of bacteremia (monomicrobial vs. polymicrobial).MethodsWe reviewed the charts of 1321 Streptococcal isolates which included 335 SAG with 107 SI during the last 3 years, in patients admitted to our network hospitals. Age, sex, clinical findings, lab reports, procedures, imaging, and susceptibilities were analyzed.ResultsAge range was one month to 90 years with 167 males and 166 females. There were 335 SAG isolates, SA 151(67M/84F), SI 107(56M/51F) and SC 77 (47M/30F). 70% of SI patients were in the 40–80 age group. There were 17 SI bacteremias (all monomicrobial) compared with 26 SA (17%), with 14 (54%) polymicrobial and 11 SC with 5 polymicrobial l (46%). 16 isolates were from empyema fluid, 11 related to IVDU, 9 liver abscesses, 6 perforated bowel, 3 peritonsillar abscesses, 3 breast abscesses, 3 mandibular osteomyelitis, 3 neck infections, 3 myositis, 3 pancreas associated, 1 each of mandibular sialadenitis, epidural abscess, cranial osteomyelitis, brain abscess, vertebral osteomyelitis and remainder soft-tissue infections in extremities or face. Some were related to poor oral hygiene or dental procedures. One abdominal wall infection was from a toothpick puncture. Twenty-five were polymicrobial infections. There were 4 deaths, three attributable to SI infection. All isolates tested (32) were susceptible to penicillin (MIC 0.008–0.125 μg/mL), ceftriaxone (MIC = 0.032–0.125 μg/mL) and vancomycin (MIC 0.38–1.0 μg/mL).ConclusionSI appears to be underreported. All SI bacteremias in the study were monomicrobial in contrast to 54% SA and 45% SC blood cultures with multiple organisms. The most common isolation site was empyema fluid. Almost all isolates appeared to originate from oral or gastrointestinal flora. Several of the sites encountered have not been reported previously. All isolates tested were susceptible to penicillin, ceftriaxone, and vancomycin.Disclosures All authors: No reported disclosures.