Abstract
Streptococcus bovis/Streptococcus equinus complex (SBSEC), a non-enterococcal group D Streptococcus spp. complex, has been described as commensal bacteria in humans and animals, with a fecal carriage rate in humans varying from 5% to over 60%. Among streptococci, SBSEC isolates represent the most antibiotic-resistant species—with variable resistance rates reported for clindamycin, erythromycin, tetracycline, and levofloxacin—and might act as a reservoir of multiple acquired genes. Moreover, reduced susceptibility to penicillin and vancomycin associated with mobile genetic elements have also been detected, although rarely. Since the association of SBSEC bacteremia and colon lesions, infective endocarditis and hepatobiliary diseases has been established, particularly in elderly individuals, an accurate identification of SBSEC isolates to the species and subspecies level, as well as the evaluation of antibiotic resistance, are needed. In this paper, we reviewed the major methods used to identify SBSEC isolates and the antimicrobial resistance rates reported in the scientific literature among SBSEC species.
Highlights
Streptococcus bovis/Streptococcus equinus complex (SBSEC), a non-enterococcal group D Streptococcus spp. complex, comprises several species: Streptococcus equinus, Streptococcus infantarius subsp. infantarius, Streptococcus lutetiensis, Streptococcus alactolyticus and three subspecies of the clade Streptococcus gallolyticus, namely S. gallolyticus subsp. gallolyticus (SGSG), S. gallolyticus subsp. macedonicus and S. gallolyticus subsp. pasteurianus (SGSP)
Streptococcus bovis/Streptococcus equinus complex (SBSEC), a non-enterococcal group D Streptococcus spp. complex, has been described as commensal bacteria in humans and animals, with a fecal carriage rate in humans varying from 5% to over 60%
Several studies from Spain conducted on SBSEC and complying the criteria used in the present review reported variable antibiotic resistance rates for erythromycin (48-78%) and clindamycin (45–72%)
Summary
Streptococcus bovis/Streptococcus equinus complex (SBSEC), a non-enterococcal group D Streptococcus spp. complex, comprises several species: Streptococcus equinus, Streptococcus infantarius subsp. infantarius, Streptococcus lutetiensis, Streptococcus alactolyticus and three subspecies of the clade Streptococcus gallolyticus, namely S. gallolyticus subsp. gallolyticus (SGSG), S. gallolyticus subsp. macedonicus and S. gallolyticus subsp. pasteurianus (SGSP). An association between S. bovis isolation and chronic liver and biliary tract disorders has been described [10] It is still unclear how commensal-to-pathogens transition occurs in SBSEC members, relating to survival, colonization, adhesion, invasion, and interaction with the host immune system. The difficulties encountered over the years in the correct identification of SBSEC to the species and subspecies level by phenotypic and genotypic methods, made a harmonized analysis of the literature difficult to achieve [12]. SGSG represents the major cause of infective endocarditis and monomicrobial bacteremia, associated with colorectal cancer [13,14,15]. SGSP and S. infantarius seem, instead, mainly related to immunosuppressive comorbidities and polymicrobial bacteremia, while being associated with biliary-pancreatic diseases and biliary tract infections. The present narrative review is focused on the major diagnostic methods used to identify SBSEC isolates, as well as on the antimicrobial resistance rates reported among SBSEC species
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