title: Group G beta-hemolytic streptococcal bacteremia characterized by 16S ribosomal RNA gene sequencing.
abstract: Little is known about the relative importance of the four species of Lancefield group G beta-hemolytic streptococci in causing bacteremia and the factors that determine the outcome for patients with group G beta-hemolytic streptococcal bacteremia. From 1997 to 2000, 75 group G beta-hemolytic streptococcal strains were isolated from the blood cultures of 66 patients. Sequencing of the 16S rRNA genes of the group G beta-hemolytic streptococci showed that all 75 isolates were Streptococcus dysgalactiae subspecies equisimilis. The API system (20 STREP) and Vitek system (GPI) successfully identified 65 (98.5%) and 62 (93.9%) isolates, respectively, as S. dysgalactiae subspecies equisimilis with >95% confidence, whereas the ATB Expression system (ID32 STREP) only successfully identified 49 isolates (74.2%) as S. dysgalactiae subspecies equisimilis with >95% confidence. The median age of the patients was 76 years (range, 33 to 99 years). Fifty-six patients (85%) were over 60 years old. All patients had underlying diseases. No source of the bacteremia was identified (primary bacteremia) in 34 patients (52%), whereas 17 (26%) had cellulitis and 8 (12%) had bed sore or wound infections. Fifty-eight patients (88%) had community-acquired group G streptococcal bacteremia. Sixty-two patients (94%) had group G Streptococcus recovered in one blood culture, whereas 4 patients (6%) had it recovered in multiple blood cultures. Fifty-nine patients (89%) had group G Streptococcus as the only bacterium recovered in their blood cultures, whereas in 7 patients other bacteria were recovered concomitantly with the group G Streptococcus in the blood cultures (Staphylococcus aureus in 3, Clostridium perfringens in 2, Citrobacter freundii in 1, and Bacteroides fragilis in 1). Overall, 10 patients (15%) died. Male sex, diagnosis other than cellulitis, hospital-acquired bacteremia, and multiple positive blood cultures were associated with mortality [P < 0.005 (relative risk [RR] = 7.6), P < 0.05 (RR = 3.7), P < 0.005 (RR = 5.6), and P < 0.05 (RR = 5.6), respectively]. Unlike group C beta-hemolytic streptococcal bacteremia, group G beta-hemolytic streptococcal bacteremia is not a zoonotic infection in Hong Kong.
authors.affiliation: Department of Microbiology, The University of Hong Kong, Queen Mary Hospital, Hong Kong.
authors.forename: P C
authors.initials: PC
authors.lastname: Woo
authors.forename: A M
authors.initials: AM
authors.lastname: Fung
authors.forename: S K
authors.initials: SK
authors.lastname: Lau
authors.forename: S S
authors.initials: SS
authors.lastname: Wong
authors.forename: K Y
authors.initials: KY
authors.lastname: Yuen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016470:Bacteremia / Q000382:microbiology*; D015373:Bacterial Typing Techniques; D001483:Base Sequence; D001769:Blood / Q000382:microbiology; D003470:Culture Media; D005260:Female; D020459:Genes, rRNA; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D012336:RNA, Ribosomal, 16S / Q000235:genetics*; D017422:Sequence Analysis, DNA; D013290:Streptococcal Infections / Q000382:microbiology*; D013291:Streptococcus / Q000145:classification* / Q000235:genetics
chemical_list: D003470:Culture Media; D012336:RNA, Ribosomal, 16S