Streptococcus anginosus group infections: Management and outcome at a tertiary care hospital.

BACKGROUND: Data on patients with invasive Streptococcus anginosus group (SAG) infections is limited, as it's been considered commensal bacteria in the human microbiota. We conducted an analysis of SAG infections to assist clinicians in understanding their burden and clinical outcomes.

METHODS: A retrospective study of medical records, identifying invasive SAG bacteria of sterile-site isolates that were managed from May 2015 to April 2017, at a tertiary care hospital in Riyadh, Saudi Arabia. Demographic data, clinical presentation, site of infection, antibiotic use, and outcome were recorded and analyzed to identify factors associated with poor outcome and/or polymicrobial growth.

RESULTS: We identified 105 cases of SAG infections in adults, with 52% of the patients being male and the mean age of 52.4 years with comorbidities occurring in more than half of the cases such as diabetes (38%) and malignancy (15%). Overall mortality was 6%, and it was statistically associated with age older than 65 years, polymicrobial growth and a history of malignancy. The infection frequencies were skin and soft tissue infections (SSTI; 55%), intra-abdominal infections (24%), bacteremia (14%), genitourinary infections (8.5%), and pleuropulmonary infections (5%). Abscesses accounted for 68% of cases. Polymicrobial infection (46%) with Enterobacteriaceae and Gram-negative anaerobes coincided with SAG infection. Polymicrobial growth was significantly associated with abscess formation, intra-abdominal source of infections, and poor outcome. In addition, death in patients with SAG was statistically associated with patients older than 65 years of age and those with history of cancer or transplant.

CONCLUSION: SSTIs and intra-abdominal infections are the most common clinical presentations in our cohort. Bacteremia was uncommon; however, the prognosis is less favorable. Overall susceptibility to penicillin was 91%, therefore β-lactam antibiotics are the drug of choice and additional coverage for anaerobic and gram-negative bacteria should be considered for intra-abdominal collection and solid or organ abscesses.