Infections : Actinomycoses
Pathogen/Epidemiology
Actinomyces israelii is the cause behind the majority of human actinomycoses
Bacteria characteristic
Filamentous, Gram-positive, branched, anaerobic, non-motile, non-acid-resistant bacteria
Saprophytes of the oral cavity, oropharynx, digestive tract, and genital mucosa
Epidemiology
Actinomycosis is endemic, without geographical predisposition
Occurs at any age and regardless of immunity
The natural reservoir is humans
Pathophysiology
Pathogenicity of these saprophytic bacteria by breaking the skin-mucosal barrier: trauma, surgery, inflammatory diseases; predisposing factors: diabetes, neoplasia
Development in deep tissues with suppuration by contiguity, formation of multiple abscesses in neighboring organs, masses capable of mimicking tumors
Subacute or chronic suppuration with progression to fistulization
Possible hematogenous dissemination
Transmission
No human-to-human transmission
Clinical
Subacute or chronic invasive infection, mimicking tuberculosis or a tumor, always serious
Possible hematogenous dissemination with cerebral or subcutaneous localizations.
Multiple clinical presentations:
Cervicofacial actinomycoses (55 to 60%)
Follow dental care or local pathology (salivary lithiasis, oral trauma)
Favored by poor oral hygiene and/or systemic corticosteroid therapy
Usual evolution without fever, formation of an infiltrating abscess, violaceous red, located submandibular, preauricular, cervical, or facial, slowly progressive evolution towards fistulization to the skin or into the oral cavity
Dreaded complications: mandibular osteitis and cervical spondylitis
Abdominal actinomycoses (20 to 25%)
Occurs after abdominal surgery (appendectomy, appendicular abscess) or perforation of the stomach, duodenum, or intestine (sigmoiditis, ulcer, trauma)
Preferential abdominal localization: ileocecal. Other organs that may be affected: stomach, liver, gallbladder
Non-specific clinical signs: fever, abdominal pain, transit disorders, palpable mass
Extension by contiguity to the peritoneal and retroperitoneal cavity, pelvic organs, vertebral bodies, and abdominal wall, in the form of chronic abscesses fistulizing to the skin or into a hollow viscera
Thoracic actinomycoses (15%)
Caused by food aspiration, esophageal fistula (traumatic or neoplastic), extension to the mediastinum from a neighboring actinomycosis (cervical or abdominal)
Sometimes complicates bronchiectasis
Extension by contiguity to the lungs, pleurae, pericardium, mediastinum, rib cage, vertebrae
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Possible thoracic X-ray images: poorly defined parenchymal mass,
chronic infiltrate, thick-walled cavity image, pleural effusion. It may be normal in cases of dorsal spondylitis or wall abscess. Interest of CT scan or MRI to specify lesions
Pelvic actinomycoses (5%)
Primary (after IUD placement) or secondary to peritoneal localization
Association with other saprophytic anaerobes or other bacteria
Brain abscess, chronic osteomyelitis (drug addict), suppuration after bite
Diagnosis
Diagnosis of actinomycosis requires a meticulous approach due to the specific characteristics of the causative bacteria and the varied clinical presentations of the infection. Rapid transport of samples to the laboratory is imperative to ensure accurate diagnosis, especially considering the anaerobic nature of the bacteria involved. Upon receiving the samples, it is essential to notify the bacteriologist to facilitate proper processing and culture.
Culturing actinomycotic bacteria can be challenging, particularly on enriched anaerobic media. These bacteria exhibit slow growth, with cultures often taking 2 to 3 weeks to yield results, especially in the case of Actinomyces israelii. Despite the difficulties, identifying characteristic features in cultures, such as sulfur granules within pus, can aid in confirming the diagnosis. These sulfur granules result from the secretion of polysaccharides by the bacteria, forming yellow particles that are pathognomonic for actinomycosis.
Histological examination of tissue samples provides further insight into the nature of the infection. Microscopic evaluation reveals palisading filaments and grains within poorly vascularized actinomycotic follicles, accompanied by intense fibrosis. These findings corroborate the clinical suspicion of actinomycosis and contribute to confirming the diagnosis.
Imaging studies play a crucial role in diagnosing actinomycosis, often presenting findings that mimic neoplastic processes. Radiological investigations, such as X-rays, CT scans, or MRI scans, may reveal parenchymal masses, chronic infiltrates, or thick-walled cavities characteristic of the infection. However, it is essential to interpret these findings in conjunction with clinical and histological data to reach an accurate diagnosis.
Treatment
The treatment of actinomycosis typically involves prolonged antibiotic therapy tailored to the susceptibility profile of the infecting bacteria. Actinomycotic bacteria are generally sensitive to Penicillin G and amoxicillin, which serve as first-line agents in the management of the infection. However, in cases of penicillin allergy, alternative antibiotics such as macrolides, synergistins, clindamycin, or tetracyclines may be prescribed.
In cases of penicillin allergy, doxycycline may be administered intravenously for 4 to 6 weeks, followed by oral therapy for 6 to 12 months. Additionally, other antibiotics such as macrolides, synergistins, and clindamycin may exhibit activity against actinomycotic bacteria and can be considered as alternative treatment options.
Prolonged treatment:
Due to the slow-growing nature of actinomycotic infections and the propensity for deep tissue involvement, treatment often necessitates a prolonged duration. Intravenous administration of antibiotics, such as amoxicillin, is initiated for 2 to 6 weeks, followed by a transition to oral therapy for several months. The duration of treatment varies depending on the extent of tissue involvement, with soft tissue infections typically requiring 3 to 6 months of therapy and osteitis necessitating 8 to 12 months of treatment.
Surgical drainage
Prevention
Preventing actinomycosis primarily involves maintaining good oral hygiene practices and seeking regular dental care. Adequate oral hygiene reduces the risk of oral infections and minimizes the potential for oral trauma, which can serve as a predisposing factor for actinomycotic infections.
Furthermore, individuals with intrauterine devices (IUDs) should undergo regular gynecological consultations to monitor for potential complications, including pelvic actinomycosis. Prompt identification and management of predisposing factors, such as IUD-related infections, can help prevent the development of actinomycotic infections and their associated complications.
In conclusion, the diagnosis and management of actinomycosis require a comprehensive approach encompassing clinical, microbiological, and radiological evaluations. Prompt initiation of appropriate antibiotic therapy, along with surgical intervention when indicated, can facilitate the resolution of the infection and prevent long-term sequelae. Emphasizing preventive measures, such as good oral hygiene and regular medical follow-up, is essential in reducing the incidence and burden of actinomycotic infection.