STREPTOCOCCUS ANGINOSUS GROUP - BRIEF CHARACTERIZATION AND ITS
CONTRIBUTION TO THE BRAIN ABSCESS PATHOGENESIS
focus and only 31% and 61% of them were isolated
by culture or detected by Sanger DNA sequencing,
respectively. Twenty-four strains of S. intermedius,
16 strains of Fusobacterium nucleatum and 11
strains of Aggregatibacter aphrophilus were
present in different combinations in all the samples
and therefore, the authors concluded that these
species should be considered key pathogens for
the establishment of polybacterial abscesses. In the
respective research, S. constellatus was detected
only in 2 cases of polymicrobial brain abscesses,
while S. intermedius and F. nucleatum represented
the only microorganisms found in monobacterial
abscesses too. All Anginosus group streptococcal
isolates were susceptible to ceftriaxone and
cefotaxime. These cephalosporins associated with
metronidazole represent the first line antimicrobial
therapy for brain abscess in Norway.42
The species of Anginosus group involved in
cerebral abscess may originate not only from the
mouth and upper respiratory tract, but also from
the gut flora. Thus, Zhou et al. reported a very recent
case of a 30-year-old patient with a brain abscess
secondary to a recurrent sigmoid diverticular
abscess, with isolation of the same strain of S.
anginosus from both abscesses.43 A Dutch team
published a case report of a 51-year-old patient
who developed a temporo-parieto-occipital
abscess with leakage into the ventricle following
a transanal hemorrhoidal dearterialization done
under spinal anesthesia 2 weeks ago.44 The initial
treatment consisted in dexamethasone and
intravenous penicillin, metronidazole (for 2 weeks)
and ceftriaxone (for 3 days). Antibiotic treatment
was continued with penicillin and ventriculoscopy
with abscess drainage were performed after 3
weeks. A penicillin-susceptible strain of S. milleri
group was isolated from the pus culture.
Unfortunately, there are more studies in which the
isolates of the Anginosus group were not identified
at species level, and were reported using the
present or the former name of this streptococcal
group. Thus, in a case-report of a 51-year-old
man with concomitant brain and lung abscess
associated with T4-T5 spondylodiscitis, treated with
surgical drainage and antibiotics, the etiological
agent found was S. milleri. 45 The isolation of
S. milleri was also reported in a case of a 28-year-old
man with headache, fever, limited homonymous
hemianopsia and a drift leg, who was diagnosed
by magnetic resonance imaging with parafalcine
subdural empyema and occipital brain abscess. 46
The patient was treated with penicillin G.
The logistic regression analysis applied for a
20-year review of medical records of pediatric
patients with intracranial complications following
rhinosinusitis indicated that S. anginosus group was
involved in about one third of the total 50 cases,
developed more severe intracranial complications,
with permanent neurologic deficit, and required
frequent surgical treatment and longer period of
intravenous antimicrobial administration.47
A Chinese team conducted a retrospective study
on the etiology, management and outcome of
the brain abscesses recorded in a single hospital
in Shanghai, between 2001- 201.48 Sixty patients
were treated by stereotactic guided aspiration
or craniotomy excision during that period.
Because many of them received antibiotics before
neurosurgery, the cultures were positive only
in 13,33% cases, with the streptococcal isolates
predominating, including S. anginosus and S.
intermedius strains. Another retrospective study
made in a Japanese hospital indicated the same
predominance of S. milleri isolates in the brain
abscess etiology, either the source of infection was
known or not. 49 A retrospective study performed
by a British team in a tertiary pediatric infectious
diseases and neurosurgical center showed that
there were 17 children diagnosed and treated
with brain abscesses, 22 children with subdural
empyema and 2 children with both types of
suppuration, between 2001 - 2009.50 The main
underlying condition was sinusitis and the
most isolated bacteria were the streptococci of
anginosus group.
A 5-year period research by another British
team, based on clinical data, radiological and
microbiological findings, surgical management
and outcomes in pediatric patients with sinogenic
intracranial abscesses from a university hospital,
found the streptococci belonging to anginosus
group involved in more than 2/3 of the investigated
cases.51
An Australian team performed a retrospective
study focused on the clinical, microbiologic and
treatment data obtained from 118 pediatric
patients with brain abscesses recorded between
1999 - 2009 in 4 neurosurgical centers.52 More
than half of those children received antimicrobial
agents before diagnosis, while the classical
symptom triad, long-term neurological sequelae
and fatal evolution were noticed only in: 13%,
35% and 6% of the cases, respectively. The most
frequent etiological agent was S. milleri (38%),
except for the head trauma cases, when S. aureus
predominated. The ceftriaxone/cefotaxime and
metronidazole represented the main empiric
antimicrobial treatment and it was effective in
more than 80% of cases; it is worth mentioning
that metronidazole should have been required
only in 7% of cases.
S. milleri was isolated also from a thalamic
abscess in a 56-year-old man with type 2 diabetes,
periodontitis and dental abscess.53 The patient was
cured within 2 months by stereotactic puncture,
external drainage and both intrathecally and
systemically administrated antibiotics.
In 2012 a Danish team published the results
of a 15-year retrospective review of 102 cases
of adult patients with brain abscess, treated
between January 1994 and April 2009, at
the Departments of Neurosurgery, Infectious
Medicine and Neurology of a university