In our study, we have described 31 cases of miscellaneous forms of actinomycosis, a rare life-threatening infectious disease with nonspecific features, and as far as we know, this is the largest study of actinomycosis in a single institution in China. In all of the presented cases of actinomycosis it is clear that a late diagnosis of this infection is still an ongoing difficulty, delaying appropriate treatment and increasing infection duration. Although it is readily treatable and curable if the patient is appropriately managed. Thus, this infection represents a great diagnostic challenge.
Actinomycosis is certainly under-reported as a consequence of diagnostic errors, difficulties in confirming the disease, and the empirical utilization of antibiotics. Data about the incidence estimates are nor recent and lack in developing countries. It was reported about one per 300 000 in the 1970s of Cleveland, USA while it was estimated to be one per million in the 1960s of Germany and the Netherlands[1]. The incidence of all forms of actinomycosis is thought to have declined in recent years, especially in developed countries as a result of better oral hygiene and susceptibility to a broad range of antibiotics. Largest series focused on single anatomical forms[10, 18], whereas some case reports of unusual presentations have been published in China[3, 19]. To our knowledge, there is no report about multiple forms of actinomycosis in China. This study try to outline the etiology, diagnosis, clinical features, treatment, and prognosis of the disease in a teaching hospital in southern China during the past 20 years.
Clinical picture of the actinomycosis can mimic different diseases, for example, tumors, tuberculosis, nocardiosis, fungal or other diseases, consequently, diagnosis may be very difficult[1]. Besides, the bacteriological identification of Actinomyces occur in only a minority of cases because of previous antibiotic therapy, inhibition of Actinomyces growth by concomitant and/or contaminant microorganisms, inadequate culture conditions, or inadequate short-term incubation, especially in developing country[7]. A Gram stain of the specimen is usually more sensitive than culture, especially if the patient had received antibiotics. Actinomyces are non-spore-forming Gram-positive rods. Except for A. meyeri, which is small and nonbranching, all the other species are branching filamentous rods. Sulphur granules are colonies of organisms that appear as round or oval basophilic masses with eosinophilic terminal “clubs” on staining with haematoxylin-eosin. Although the presence of sulphur granules is helpful in making the diagnosis, they are not always recovered in culture confirmed cases of actinomycosis. Only one patient (Patient 16) presented with Sulphur granules in lung specimens. Gram staining of Nocardia spp. is morphologically similar to that of Actinomyces spp. and there is some features that may help to distinguish these 2 microorganisms [20]. In our study, only two patients (Patient 19, 20) were diagnosed by sputum culture while the rest patients were confirmed by different tissue samples histologically. The failure rate of culture seems higher than that reported in the west, meanwhile the median duration from first symptoms to diagnosis is also longer [21].
Most commonly, the actinomycosis presents as a slowly progressive, indolent infiltration with dense fibrosis, multiple abscesses, fistulas and draining sinuses. Rarely, the infection is acute and rapidly progressive, which is consistent with our study. To date, multiple different clinical features of actinomycosis have been described, as various anatomical sites (such as face, bone and joint, respiratory tract, genitourinary tract, digestive tract, central nervous system, skin, and soft tissue structures) can be affected. Our study try to picture the panorama of actinomycosis in multiple possible focalizations.
Actinomyces are commensals of the human oropharynx, and are particularly prevalent within gingival crevices, tonsillar crypts, periodontal pockets and dental plaques, as well as on carious teeth. If the anatomical barriers are breached, the bacteria can become pathogenic and and usually presents as a chronic, painless or occasionally painful soft-tissue swelling of the submandibular or perimandibular region, draining sinus tracts with sulfur granules, difficulties in chewing and chronic/relapsing course of the infection. Consequently, cervicofacial actinomycosis is the most frequent clinical form of actinomycosis, representing approximately 60% of all reported cases[1]. It is about 45% in our study, and the susceptibility to a broad range of antibiotics and misdiagnose may account for less cases despite the poor oral hygiene in the most patients. Cervicofacial actinomycosis could be associated with large abscesses and/or mandibular osteomyelitis with or without sinus tract. Risk factors for cervicofacial and oral actinomycosis are dental procedures such as dental extractions, dental caries, trauma, gingivitis, chronic tonsillitis, periodontal disease, otitis or mastoiditis, possibly diabetes and immunosuppression, malnutrition, and local tissue injuries by tumors, surgery, or irradiation. All the patients were identified with aboved predisposing conditions in our study.
Thoracic actinomycosis, including intrathoracic organs and the thoracic wall, accounts for 15-20% of cases [1]. Actinomyces rarely causes endocarditis but sometimes can be life-threatening [22], and there are just some case reports about this uncommon type of actinomycosis [23]. Thoracic actinomycosis exhibits a pulmonary infiltrate, causing cough and hemoptysis (most common clinical signs), chest wall pain, weight loss, sputum production or draining sinuses from the chest wall and later can be disseminated to the pleura, pericardium or chest wall[24]. The clinical manifestations of pulmonary actinomycosis may be different in different regions. Hemoptysis was more commonly seen in Asian patients while chest pain were reported to be the most common complaints in Europe [25]. Our study also reveals a high incidence of hemoptysis, which is twice of chest pain. Furthermore, imaging modalities in pulmonary actinomycosis are still nonspecific and undiagnostic. Without microbiological or histological confirmation, misdiagnosis for malignancy, tuberculosis or other infections is still fairly common. FDG-PET may be a proper choice to distinguish infection and malignancy for only one patient was misinterpreted as malignancy in total 4 patients undertaken the examination in our study. What’s more, only two patients were confirmed by culture of bronchopulmonary secretions through flexible bronchoscopy, obviously less than that reported in Simon Bonnefond study[21]. Coexistence of actinomycosis with neoplasm or tuberculosis is seen in patient 18 and 20, leading to a more challenging diagnosis and treatment of thoracic actinomycosis.
Risk factors for the abdominopelvic form can be abdominal operations, perforated acute appendicitis or colonic diverticulitis, mesenteric vascular insufficiency, ingestion of foreign bodies, caesarean sections or presence of prosthetic devices such as IUD contraceptives [26]. In our study, 3 female patents all has a history of prolonged use of an IUD, among whom patient 26 had the IUD for more than 20 years. It has been reported that the abdominal form presents classically as a slowly growing tumor, usually at the ileocecal region (less often at the stomach, duodenum, liver, rectum or several organs), causing vague abdominal pain, weight loss, low-grade fever, nausea or vomiting. For pelvic form, the most common clinical complaints are lower abdominal discomfort, abnormal vaginal bleeding or discharge [27]. But all the symptoms are often nonspecific and differential diagnosis often involves digestive and genital tumors, inflammatory disease and endometriosis. In our study, we reported an unusual case of abdominal wall actinomycosis with no risk factors which is different from other cases reported [28, 29]. Other sites of actinomycosis, such as the central nervous system, urinary tract, bones, muscle tissue and skin are rare [1].
Actinomyces spp. is known to be susceptible to penicillins and to other ß-lactams, with the exception of oxacillin, dicloxacillin, and cephalexin. This anaerobe is also susceptible to doxycycline, clindamycin, erythromycin and clarithromycin, linezolide, and tigecicline. In our study, one patient was cured by prescribing doxycycline because of allergic history of pencillin. Although the organism is multisusceptible, in most cases of infection, an initial intravenous treatment with antibiotics for 2 to 6 weeks (preferably with penicillin G) with subsequent prolonged oral treatment for 6 to 12 month (amoxicillin 2g/day divided in 4 doses) is required[1]. Antibiotic treatment duration depends on infection localization and severity, and concomitant surgical approach may be required. Complete resection of the infection lesions alone is effective showed in our study but the necessity of surgery must be fully evaluated. In conclusion, individualized treatment programs based on the the best characteristics of patients is an ideal therapeutic schedule for actinomycosis.
A few limitations are apparent in this study. First, as a retrospective analysis, selection bias may have affected the statistical robustness to some extent. Second, ten patients were lost to follow-up; however, the other patients were followed at least for 9 months, which can be considered as satisfactory in the setting of an infectious disease. Third, almost all of our patients were diagnosed from histological criteria postoperatively, some cases of actinomycosis could be missing. In spite of these defects, this study provides some important information about actinomycosis in a developing country, and a comparison with that in developed countries will expedite the understanding for actinomycosis.