Discussion:
Actinomycosis is an infrequent invasive bacterial disease that has been
recognized for over a century. Actinomyces spp. are filamentous
Gram-positive bacilli, mainly belonging to the human commensal flora of
the oropharynx, gastrointestinal tract, and urogenital tract. To date,
multiple different clinical features of actinomycosis have been
described, as various anatomical sites (such as the face, bone, joint
and …) can be affected. (19,20,21)
Osseous actinomycosis usually results from a direct invasion of bone
from adjacent soft-tissue infection. Involvement of the jaw and
vertebral column has been frequently reported, but involvement of the
bones of the wrist or hand is rare. (20)
The use of broad-spectrum antibiotics can indeed impact the microbiome,
making it challenging to extract and identify Actinomyces. (13) To
ensure efficient recovery, specific anaerobic transport methods and
pre-reduced anaerobically sterilized (PRAS) media are necessary.
Your emphasis on strict anaerobic conditions during incubation is
well-placed. Actinomyces species are more resistant to ambient oxygen
compared to other anaerobic bacteria, making anaerobic incubation
essential. (14) Gram staining can be more sensitive than culture,
especially in patients who have received antibiotics. Actinomyces are
Gram-positive rods that do not produce spores, except for A. meyeri,
which is tiny and nonbranching. (10)
The slow growth of Actinomyces, requiring up to 15-20 days for full
maturation, necessitates extended incubation periods. Negative cultures
should be incubated for at least 10 days before concluding as negative.
In bone infections, where bacterial growth may be limited, even longer
incubation periods may be necessary. On chocolate blood agar media at
37°C, Actinomyces can be grown.
Histological examination plays a crucial role in identifying
actinomycosis. (8) The formation of sulfur granules, characterized by
the presence of small aggregates stabilized by a protein-polysaccharide
complex, is a hallmark of Actinomyces invasion. (15) Histopathology
reveals the presence of sulfur granules in approximately 75% of
patients, which appear basophilic with eosinophilic distal branches when
stained.
While the presence of sulfur granules is highly suggestive of
actinomycosis, it is important to note that they can also occur in other
infectious disorders. Gram staining, revealing Gram-positive filamentous
branching bacteria near the periphery of the granules, provides further
evidence of actinomycosis. (16)
When it comes to treatment, beta-lactams, particularly penicillin G or
amoxicillin, are highly effective against Actinomyces species and are
the preferred drugs of choice. Piperacillin-tazobactam, imipenem, and
meropenem are also effective antibiotics, but their use should be
reserved for serious and resistant cases to prevent the development of
resistant microflora. (17)
Metronidazole and aminoglycosides have limited efficacy against
Actinomyces, while fluoroquinolones like ciprofloxacin and moxifloxacin
are generally considered ineffective. (18) However, doxycycline has
shown clinical effectiveness, despite initial beliefs of low activity.
Macrolides and clindamycin are also effective treatment options for
actinomycosis.
The patient’s case presents a complex and challenging scenario. After
the initial appearance of pustules on the dorsal side of the left hand,
the lesion progressed and recurred despite previous treatment attempts.
The subsequent histopathologic evaluation confirmed the diagnosis of
actinomycosis, and further imaging studies revealed osteomyelitis in the
carpal bones and proximal metacarpals, along with multiple collections
and joint destruction. The patient reported experiencing numbness and
paresthesia in the hand, which was likely due to compression of nerves
and vessels in the carpal tunnel by the tumor-like abscesses and
lesions.
Orthopedic consultation recommended extensive debridement and possible
amputation due to the severity of the condition. However, the patient
did not provide consent for surgery. In light of this, antibiotic
treatment with amoxicillin and TMP-SMX was initiated. Fortunately, the
patient has responded well to the treatment, as evidenced by the
shrinking of the lesion, reduction in vascular engorgement, and
resolution of paresthesia.
It is crucial to closely monitor the patient’s progress and continue the
antibiotic therapy to ensure complete remission and prevent any further
complications. Regular follow-up examinations and imaging studies will
help assess the effectiveness of the treatment and guide further
management decisions.