Pcy. Woo et al., Group G beta-hemolytic streptococcal bacteremia characterized by 16S ribosomal RNA gene sequencing, J CLIN MICR, 39(9), 2001, pp. 3147-3155
Little is known about the relative importance of the four species of Lancef
ield group G beta-hemolytic streptococci in causing bacteremia and the fact
ors that determine the outcome for patients with group G beta-hemolytic str
eptococcal bacteremia. From 1997 to 2000, 75 group G beta-hemolytic strepto
coccal strains were isolated from the blood cultures of 66 patients. Sequen
cing of the 16S rRNA genes of the group G beta-hemolytic streptococci showe
d that all 75 isolates were Streptococcus dysgalactiae subspecies equisimil
is. The API system (20 STREP) and Vitek system (GPI) successfully identifie
d 65 (98.5%) and 62 (93.9%) isolates, respectively, as S. dysgalactiae subs
pecies equisimilis with >95% confidence, whereas the ATB Expression system
(ID32 STREP) only successfully identified 49 isolates (74.2%) as S. dysgala
ctiae subspecies equisimilis with >95% confidence. The median age of the pa
tients 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 b
acteremia was identified (primary bacteremia) in 34 patients (52%), whereas
17 (26%) had cellulitis and 8 (12%) had bed sore or wound infections. Fift
y-eight patients (88%) had community-acquired group G streptococcal bactere
mia. Sixty-two patients (94%) had group G Streptococcus recovered in one bl
ood culture, whereas 4 patients (6%) had it recovered in multiple blood cul
tures. Fifty-nine patients (89%) had group G Streptococcus as the only bact
erium recovered in their blood cultures, whereas in 7 patients other bacter
ia were recovered concomitantly with the group G Streptococcus in the blood
cultures (Staphylococcus aureus in 3, Clostridium perfringens in 2, Citrob
acter freundii in 1, and Bacteroides fragilis in 1). Overall, 10 patients (
15%) died. Male sex, diagnosis other than cellulitis, hospital-acquired bac
teremia, and multiple positive blood cultures were associated with mortalit
y {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 streptococca
l bacteremia, group G beta-hemolytic streptococcal bacteremia is not a zoon
otic infection in Hong Kong.