STREPTOCOCCUS ANGINOSUS GROUP - BRIEF CHARACTERIZATION AND ITS
CONTRIBUTION TO THE BRAIN ABSCESS PATHOGENESIS
the evolution might be fatal, as happened in a
case presented by Matamala et al. referring to
a previously healthy woman who developed a
severe intracranial hypertension due to a brain
abscess and a subdural empyema produced by
these streptococci.12
S. intermedius is the most frequent species
belonging to Anginosus group isolated from brain
abscess and there are several research works which
described the pathogenic factors and mechanisms
of this microorganism involved in cerebral
abscess.13 A very important virulence factor
detected in S. intermedius strains is the cholesteroldependent cytolysin named intermedilysin, which
is strongly associated with brain and liver abscess
production.14 S. intermedius may express surface
proteins belonging to antigen I/II family with a role
in pathogenesis, which bind to fibronectin and
laminin and may induce the release of interleukine
(IL) -8 from monocytes, followed by chemotaxis
and activation of neutrophilic leucocytes.
S. intermedius produces high levels of ammonia
from the amino acids released by proteolysis
associated to brain tissues distruction, which
contribute to brain aedema and different
symptoms observed in brain abscess.15 The brain
suppurative process due to this species may
induce host inflammatory response, especially
high levels of Th1 and T17 cytokines, like: TNF-a,
IFN-g, IL1-b and IL-17, IL-23, respectively.16
S. intermedius can also cause multiple cerebral
abscesses as it was shown by a study published in
2012, describing a case of a young man hospitalized
for pneumonia and multiple brain abscesses17
The Gram-stained smear of the bronchoalveolar
lavage fluid showed Gram-positive cocci, while
S. intermedius was detected by a polymerase chain
reaction and by electrospray ionization with mass
spectrometry in both cerebrospinal fluid and fixed
tissue from subcarinal lymph node biopsy sample.
Multiple cerebral abscesses developed more
frequently in imunocompromised persons, and
Hanna and Das reported a case of multiple brain
abscesses due to S. intermedius in a patient with
oesophageal adenocarcinoma.18
S. intermedius can produce concomitant solitary
brain abscess and other deep-seated abscesses,
like spleen abscess19 or lung abscess20 in either
immunocompromised individuals or previously
healthy persons. S. intermedius and the other
species of Anginosus group may cause brain
abscess in children too21, 22, and like in adult cases,
the frequency of this infection was found to be
2-3 times higher in male than in female patients.22
Moskovitz et al. reported a case of cerebral
abscess in a pediatric patient with cyanotic heart
disease and extensive dental caries.23 The authors
considered a dentoalveolar abscess to be the
source of the S. intermedius strain isolated from
the cerebrospinal fluid of the patient. Besides
craniotomy with abscess drainage, the child was
treated with antibiotics for some months and
underwent proper dental procedures. Another
recent paper presented 4 cases of pediatric
patients with fever, meningeal syndrome and
seizures, diagnosed with cerebral abscess by
brain imaging, with S. intermedius isolated from
cerebrospinal fluid.24 All 3 boys and the girl were
over 12 years of age and recovered well after
abscess puncture and antibiotic treatment.
In a systematic review of intracranial abscesses of
odontogenic origin, 60 reported cases in PubMed
database have been analysed for the predisposing
condition of the patients, the clinical outcome of
the infection and the microbiological findings. 25
The conclusions were that the odontogenic brain
abscess predominated in adult men and more
than half of the patients presented signs of dental
lesions, mainly periapical lesions due to caries
and periodontitis, while many patients underwent
dental extractions.
The viridans streptococci and especially
S. anginosus group were the most frequently
isolated microorganisms from the brain abscesses,
while the rest of the isolates belonged to the
following genera or species: Peptostreptococcus,
Prevotella,
Fusobacterium,
Actinomyces,
Eikenella
corrodens
and
Aggregatibacter
actinomycetemcomitans. The abscesses have
developed in different brain regions with no
correlation between the respective site and the
side of dental infection, which suggested the
haematogenous spread. The mortality rate found
in this study was of 8.3%.
The mortality rate increases when the brain abscess
is associated with intraventricular rupture, but full
recovery has been registered also in such situations.
Nishizachi et al. reported a case of a 69-year-old
patient with brain abscess due to S. intermedius,
who underwent a neuroendoscopic evacuation
of the intraventricular pus.26 The patient has
been discharged completely recovered after one
month, during which he received intraventricular
gentamicin
and
intravenous
cefotaxime,
continuing afterwards with oral cefcapene.
Simone and colab. presented a case of a
disseminated infection with S. intermedius in a
61-year-old man with brain abscess and multiple
pulmonary and liver lesions.6 The same authors
also reviewed literature on the disseminated
infections produced by S. anginosus group and
concluded that both surgical and antibiotic therapy
were very important for the complete recovery of
the patients, mentioning that the infections caused
by these streptococci responded satisfactorily to
penicillin or cephalosporins.
Lee et al. isolated S. intermedius from a brain
abscess developed in a 47- year-old woman
with congenital heart conditions with rightto-left shunting and thromboemboly.27 The
patient was treated by surgery (craniotomy
and corticectomy) and antibiotics (penicillin
G and metronidazole). Yanagihara et al. found
S. intermedius as the etiological agent in
a cerebellar abscess case secondary to a
hepatopulmonary syndrome in a 76-year-old
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