Actinomyces meyeri infection: case report and review of the literature

A Strange Case of Traumatic Pleural Effusion: Pleural Empyema Due to Actinomyces meyeri, a Case Report

BACKGROUND

Actinomycosis by Actinomyces meyeri is rare and scarcely reported in the literature. The lung is the main organ involved. Penicillin and amoxicillin are the first-choice treatments. Surgery is indicated when empyema and abscesses are resistant to medical treatment.

CASE PRESENTATION

We report an underdiagnosed case of pleural empyema due to A. meyeri in a patient with closed chest trauma. The patient, a male, 47 years old, presented with a dry cough, thoracic pain, and dyspnea a month after the trauma. A chest X-ray showed a left lower lobe pleural effusion, so he was subjected to a thoracentesis, leading to a partial re-expansion of the left lung. The patient also complained about gum discomfort; thus, a dental x-ray scan was taken, which showed the presence of vertical bone resorption in a periodontal pocket. The patient was treated with levofloxacin 500 mg orally once a day, which was continued for 15 days after discharge. Two months after the accident, he presented again with intermittent fever, a worsening cough, and dyspnea. A CT scan showed thickening of the left pleura and a loculated pleural effusion with partial collapse of the left lower lobe. A decision was made to refer the patient to the Thoracic Unit to undergo surgery via a left thoracoscopic uniportal approach. The lung was thoroughly decorticated, and the purulent fluid was aspirated. The postoperative course was uneventful. Cultures showed the growth of Actinomyces meyeri, which is sensitive to imipenem and amoxicillin. The patient started a proper antibiotic regimen and, whenever possible, was discharged. At 12 months follow-up, a chest X-ray showed a complete resolution of the left pleural effusion with complete re-expansion of the left lung.

CONCLUSIONS

Although rare, Actinomycetes infections must be considered especially in front of non-solving empyema or severe pneumonia of unknown cause because in the majority of cases, with the proper treatment, the restitutio ad integrum is possible.

The diagnosis and management of pulmonary actinomycosis

Pulmonary actinomycosis is a rare infection caused by the bacterial species actinomyces. This paper aims to provide a comprehensive review of pulmonary actinomycosis to improve awareness and knowledge. The literature was analysed using databases including Pubmed, Medline and Embase from 1974 to 2021. After inclusion and exclusion, a total of 142 papers were reviewed. Pulmonary actinomycosis is a rare disease occurring in approximately 1 per 3,000,000 people annually. Historically, pulmonary actinomycosis was a common infection with high mortality; however, the infection has become rarer since the widespread use of penicillins. Actinomycosis is known as "the great masquerade"; however, it can be differentiated from other diseases with acid-fast negative ray-like bacilli and sulphur granules being pathognomonic. Complications of the infection include empyema, endocarditis, pericarditis, pericardial effusion, and sepsis. The mainstay of treatment is prolonged antibiotic therapy, with adjuvant surgery in severe cases. Future research should focus on multiple areas, including the potential risk secondary to immunosuppression from newer immunotherapies, the utility of newer diagnostic techniques and ongoing surveillance post-therapy.

Herpes Zoster: A Case Report of a Rare Ramification Leading to Secondary Infection

The herpes virus causes herpes zoster (HZ) (shingles). It develops years later in elderly patients who were affected by the varicella-zoster virus in their childhood. The virus gets reactivated and typically localizes its symptoms to a particular dermatome. If left untreated, it can lead to dental complications, such as osteonecrosis, tooth exfoliation, periodontitis, calcified and devitalized pulps, periapical lesions, and root resorption, in addition to developmental irregularities, such as abnormally short roots and missing teeth. Here, we present the case of a 61-year-old male affected by a rare bacterial superinfection followed by an HZ infection. Our report aims at making clinicians aware of the various potential complications that can develop after an HZ infection.

Increased Abundance of Achromobacter xylosoxidans and Bacillus cereus in Upper Airway Transcriptionally Active Microbiome of COVID-19 Mortality Patients Indicates Role of Co-Infections in Disease Severity and Outcome

The modulators of severe COVID-19 have emerged as the most intriguing features of SARS-CoV-2 pathogenesis. This is especially true as we are encountering variants of concern (VOC) with increased transmissibility and vaccination breakthroughs. Microbial co-infections are being investigated as one of the crucial factors for exacerbation of disease severity and complications of COVID-19. A key question remains whether early transcriptionally active microbial signature/s in COVID-19 patients can provide a window for future disease severity susceptibility and outcome? Using complementary metagenomics sequencing approaches, respiratory virus oligo panel (RVOP) and Holo-seq, our study highlights the possible functional role of nasopharyngeal early resident transcriptionally active microbes in modulating disease severity, within recovered patients with sub-phenotypes (mild, moderate, severe) and mortality. The integrative analysis combines patients' clinical parameters, SARS-CoV-2 phylogenetic analysis, microbial differential composition, and their functional role. The clinical sub-phenotypes analysis led to the identification of transcriptionally active bacterial species associated with disease severity. We found significant transcript abundance of Achromobacter xylosoxidans and Bacillus cereus in the mortality, Leptotrichia buccalis in the severe, Veillonella parvula in the moderate, and Actinomyces meyeri and Halomonas sp. in the mild COVID-19 patients. Additionally, the metabolic pathways, distinguishing the microbial functional signatures between the clinical sub-phenotypes, were also identified. We report a plausible mechanism wherein the increased transcriptionally active bacterial isolates might contribute to enhanced inflammatory response and co-infections that could modulate the disease severity in these groups. Current study provides an opportunity for potentially using these bacterial species for screening and identifying COVID-19 patient sub-groups with severe disease outcome and priority medical care. IMPORTANCE COVID-19 is invariably a disease of diverse clinical manifestation, with multiple facets involved in modulating the progression and outcome. In this regard, we investigated the role of transcriptionally active microbial co-infections as possible modulators of disease pathology in hospital admitted SARS-CoV-2 infected patients. Specifically, can there be early nasopharyngeal microbial signatures indicative of prospective disease severity? Based on disease severity symptoms, the patients were segregated into clinical sub-phenotypes: mild, moderate, severe (recovered), and mortality. We identified significant presence of transcriptionally active isolates, Achromobacter xylosoxidans and Bacillus cereus in the mortality patients. Importantly, the bacterial species might contribute toward enhancing the inflammatory responses as well as reported to be resistant to common antibiotic therapy, which together hold potential to alter the disease severity and outcome.

Distribution and Evolutionary History of Sialic Acid Catabolism in the Phylum Actinobacteria

Sialic acids are present in humans and other metazoans, playing essential roles in physiological and pathological processes. Commensal and pathogenic bacteria have evolved the capacity to utilize sialic acids as nutrient and energy sources. However, in some actinobacteria, sialic acid catabolism (SAC) is associated with free-living populations. To unravel the distribution and evolutionary history of SAC in the phylum Actinobacteria, we analyzed the presence and diversity of the putative SAC gene cluster (nan) in 7,180 high-quality, nonredundant actinobacterial genomes that covered 1,969 species. The results showed that ∼13% of actinobacterial species had the potential to utilize sialic acids, with 45 species capable of anhydro-SAC, all except two of them through the canonical pathway. These species belonged to 20 orders and 81 genera, with ∼36% of them from four genera, Actinomyces, Bifidobacterium, Corynebacterium, and Streptomyces. Moreover, ∼40% of the nan-positive species are free living. Phylogenetic analysis of the key nan genes, nanA, nanK, and nanE, revealed a strong signal of horizontal gene transfer (HGT), accompanied with vertical inheritance and gene loss. This evolutionary pattern led to high diversity and differential distribution of nan among actinobacterial taxa and might cause the cluster to spread to some free-living species while losing in some host-associated species. The evolution of SAC in actinobacteria probably represents the evolution of certain kinds of noncore bacterial functions for environmental adaptation and lifestyle switch, in which HGT plays a dominant role. IMPORTANCE Sialic acids play essential roles in the physiology of humans and other metazoan animals, and microbial sialic acid catabolism (SAC) is one of the processes critical for pathogenesis. To date, microbial SAC is studied mainly in commensals and pathogens, while its distribution in free-living microbes and evolutionary pathway remain largely unexplored. Here, by examining all actinobacterial genomes available, we demonstrate that putative SAC is present in a small proportion of actinobacterial species, of which, however, ∼40% are free-living species. We also reveal remarkable difference in the distribution of SAC among actinobacterial taxa and high diversity of the putative SAC gene clusters. HGT plays a significant role in the evolution of SAC, accompanied with vertical inheritance and gene loss. Our results provide a comprehensive and systematic picture of the distribution and evolutionary history of SAC in actinobacteria, expanding the current knowledge on bacterial adaptation and diversification.

Actinomyces meyeri pleural empyema: A case report

We report the case of a man with intense cough for several months and a few days of severe dyspnea. A massive pleural empyema due to Actinomyces meyeri was diagnosed by radiological, microbiological and thoracoscopic means. Pleural infections caused by this anaerobic bacterium are very rare and should be considered when risk factors like male gender, chronic alcohol abuse, and poor oral hygiene are present. Penicillin-based antibiotic treatment and surgical decortication led to recovery.

Polymicrobial empyema; a novel case of Actinomyces turicensis

Empyema or infection of the pleural space is a well described complication of pneumonia, however knowledge of culprit pathogens is still evolving. We report a novel case of empyema due to Actinomyces turicensis, a commensal of the oropharynx and female urogenital tract but previously undescribed cause of empyema. We additionally review general pathogenesis of Actinomyces species within the pleural space. Familiarity with this unique pleural infection pathogen is important for selection of adequate antimicrobial therapy given the propensity of anaerobes such as Actinomyces species to disobey anatomic boundaries and recrudescence of infection in the absence of appropriate therapy.

Disseminated Pelvic Actinomycosis Caused by Actinomyces Naeslundii

Actinomycosis is a chronic bacterial infection characterized by continuous local spread, irrespective of anatomical barriers, and granulomatous suppurative inflammation. Due to its expansive local growth, it can simulate a malignant tumour. Subsequent hematogenous dissemination to distant organs can mimic metastases and further increase suspicion for malignancy. A case of severe disseminated pelvic actinomycosis associated with intrauterine device is described here. The patient presented with a pelvic mass mimicking a tumour, bilateral ureteral obstruction, ascites, multinodular involvement of the liver, lungs and spleen, inferior vena cava thrombosis and extreme cachexia. Actinomycosis was diagnosed by liver biopsy and confirmed by culture of Actinomyces naeslundii from extracted intrauterine contraceptive device (IUD). Prolonged treatment with aminopenicillin and surgery resulted in recovery with moderate sequelae.

Intracranial Subdural Abscess Caused by <i>Actinomyces meyeri</i> Related to Dental Treatment: A Case Report

Intracranial subdural abscess is a rare condition. Although brain abscess is often reported in relation to dental infection, reports of intracranial subdural abscess are few. Actinomyces spp. forms part of the normal flora of the oral, gastrointestinal, and genital tract, and is rarely the cause of intracranial infection; moreover, the pathogen Actinomyces meyeri is very rare. We report an exceptional case of intracranial subdural abscess caused by A. meyeri and related to dental treatment.

A 57-year-old woman initially presented with a 5-day history of headache. Because left arm numbness and weakness became apparent, she was admitted to our department. She had a history of hypertension and dental problems requiring tooth extractions. Diffusion-weighted imaging (DWI) showed a 1-cm right convexity hyperintense mass above the postcentral gyrus. A post-gadolinium T1-weighted image showed a thin hypointense area with peripheral rim enhancement in the right subdural space that appeared to partially thicken in the same location as the DWI-positive mass. She underwent emergent navigation-guided drainage and 4 mL of pus was obtained. Postoperatively, left arm numbness and weakness disappeared. Cultures showed growth of A. meyeri and Fusobacterium nucleatum. She was started on intravenous penicillin G and metronidazole. After a 4-week course of the intravenous antibiotics, her headache gradually improved and the abscess in the subdural space subsided.

To our best knowledge this is the first case report of intracranial subdural abscess caused by A. meyeri associated with dental treatment.

Viral, bacterial, and fungal infections of the oral mucosa: Types, incidence, predisposing factors, diagnostic algorithms, and management

For millions of years, microbiota residing within us, including those in the oral cavity, coexisted in a harmonious symbiotic fashion that provided a quintessential foundation for human health. It is now clear that disruption of such a healthy relationship leading to microbial dysbiosis causes a wide array of infections, ranging from localized, mild, superficial infections to deep, disseminated life-threatening diseases. With recent advances in research, diagnostics, and improved surveillance we are witnessing an array of emerging and re-emerging oral infections and orofacial manifestations of systemic infections. Orofacial infections may cause significant discomfort to the patients and unnecessary economic burden. Thus, the early recognition of such infections is paramount for holistic patient management, and oral clinicians have a critical role in recognizing, diagnosing, managing, and preventing either new or old orofacial infections. This paper aims to provide an update on current understanding of well-established and emerging viral, bacterial, and fungal infections manifesting in the human oral cavity.

Actinomyces Meyeri Empyema Necessitatis-A Case Report and Review of the Literature

Pleural empyema necessitatis caused by Actinomyces meyeri is a rare but severe infection. A. species predominantly A. meyeri and A. israelii represent the second most common pathogen for empyema necessitans after mycobacteria. The incidence is reported in the literature to be 1:300,000. Men are thrice more likely to be affected than women. Pathogenetically, an infection can be triggered by aspiration in immunocompromised individuals which leads to an atelectasis with pneumonitis.

In two cases, a 38-year-old construction worker and a 61-year-old woman with ulcerative breast carcinoma, who presented to the local emergency department with a painful swelling of the left chest, diagnostic workup revealed a pleural empyema necessitatis of the left chest. An antibiotic treatment was initiated with piperacillin/tazobactam and sulbactam/ampicillin, respectively. Temporally vacuum-dressing therapy was initiated after surgical debridement. In the course of the procedure, a reconstruction of tissue damage was feasible. The patients were recovered completely and discharged with an oral antibiotic treatment (amoxicillin) for 6 and 12 months, respectively.

Thoracic actinomycosis is a relatively uncommon and traditionally chronic, indolent infection secondary to pulmonary infection with A. species . Surgical treatment is generally reserved for cases failing to resolve with antibiotic therapy. Early diagnosis, prompt debridement, and narrow spectrum β-lactam antibiotics can result in complete resolution of infection and good prognosis.

Diagnosis and Management of a Cryptoglandular Actinomycotic Fistula-in-Ano: An Update on 7 New Cases and a Review of the Literature

Purpose

Primary anal actinomycosis of cryptoglandular origin, a rare cause of anal suppurative disease, requires specific management to be cured. The aims of this retrospective study were to describe clinical, morphological, and microbiological features of this entity and to evaluate management practices for new cases observed since 2001.

Methods

This was a retrospective case series conducted at the Diaconesses-Croix Saint-Simon Hospital in Paris.

Results

From January 2001 to July 2016, 7 patients, 6 males and 1 female (median, 49 years), presenting with an actinomycotic abscess with a cryptoglandular anal fistula were included for study. The main symptom was an acute painful ischioanal abscess. One patient exhibited macroscopic small yellow granules (“sulfur granules”), another “watery pus” and a third subcutaneous gluteal septic metastasis. All patients were overweight (body mass index ≥ 25 kg/m²). Histological study of surgically excised tissue established the diagnosis. All the patients were managed with a combination of classical surgical treatment and prolonged antibiotic therapy. No recurrence was observed during follow-up, the median follow-up being 3 years.

Conclusion

Actinomycosis should be suspected particularly when sulfur granules are present in the pus, patients have undergone multiple surgeries or suppuration has an unusual aspect. Careful histological examination and appropriate cultures of pus are needed to achieve complete eradication of this rare, but easily curable, disease.

Actinomyces meyeri: A Rare Cause of Postsurgical Pelvic Actinomycosis

Actinomyces meyeri bacterium resides on mucosal surfaces and is uncommonly pathogenic. When A. meyeri does cause infection, these infections are typically pulmonary in origin and have the capacity to disseminate throughout the body. A. meyeri is an uncommon cause of pelvic infection. We present a unique case of a posthysterectomy abscess caused by this particular bacterium.

A rare case of Actinomyces meyeri empyema: Still a challenging entity to manage

Actinomyces meyeri is a rare pathogen and an infrequent cause of human actinomycosis. Less than ten cases were reported in the English-literature to date concerning A. meyeri empyema. We herein report a case to promote the awareness and adequate management of the disease.

A 44-year-old immunocompetent male with known pulmonary disease was diagnosed with an A. meyeri empyema. He underwent chest tube drainage and a short-term treatment with clindamycin for 4 months.

This is the first report of a patient with structural pulmonary disease with an A. meyeri empyema treated with 4-month of clindamycin and chest tube drainage. In comparison to previous reports, our case was diagnosed early, empyema was effectively drained with one chest tube and symptoms and radiological findings were rapidly improved. Short-term antibiotic treatment can be well succeeded if an early diagnosis is made, there is no evidence of dissemination and adequate management is promptly instituted.

Actinomyces meyeri Popliteal Cyst Infection and Review of the Literature

A 66-year-old, Caucasian male presented with pain and swelling involving the left knee of one-week duration. Arthrocentesis was negative for evidence of septic arthritis. Magnetic resonance imaging (MRI) study of the left knee showed degenerative arthritis, partial tear of medial meniscus, and a complex fluid collection along the posteromedial aspect of the left knee suggestive of popliteal cyst. He underwent arthroscopy with partial medial meniscectomy. Intraoperative joint fluid was noted to be cloudy but cultures were negative. Arthroscopic procedure provided him with temporary relief but the pain and swelling in the posterior aspect of the left knee recurred in 6 weeks. Repeat MRI showed complex fluid collection in the posterolateral aspect of left knee. Ultrasound guided aspiration of the fluid collection revealed purulent material and cultures grew Actinomyces meyeri. He was treated with 6 weeks of intravenous penicillin regimen followed by 18 months of oral penicillin.

Empyema Secondary to Actinomyces meyeri Treated Successfully with Ceftriaxone Followed by Doxycycline

Actinomycosis is a relatively rare infection caused by Gram-positive bacteria. We present the case of a 54-year-old, previously healthy, male patient with a history of severe penicillin allergy who developed severe pneumonia and empyema caused by Actinomyces meyeri. Presenting symptoms included productive cough, right upper quadrant pain, and chills and rigors. He required drainage of the empyema via tube and prolonged antibiotic treatment with intravenous ceftriaxone for 2 weeks followed by oral doxycycline for 6 months.

Olecranon Osteomyelitis due to Actinomyces meyeri: Report of a Culture-Proven Case

Actinomyces meyeri is a Gram positive, strict anaerobic bacterium, which was first described by Meyer in 1911. Primary actinomycotic osteomyelitis is rare and primarily affects the cervicofacial region, including mandible. We present an unusual case of osteomyelitis of a long bone combined with myoabscess due to A. meyeri. A 70-year-old man was admitted for pain and pus discharge of the right elbow. Twenty-five days before admission, he had hit his elbow against a table. MRI of the elbow showed a partial tear of the distal triceps tendon and myositis. He underwent open debridement and partial bone resection for the osteomyelitis of the olecranon. Biopsy showed no sulfur granules, but acute and chronic osteomyelitis. The excised tissue grew A. meyeri and Peptoniphilus asaccharolyticus. Intravenous ceftriaxone was administered and switched to oral amoxicillin. Infection of the extremities of actinomycosis often poses diagnostic difficulties, but it should not be neglected even when the characteristic pathologic findings are not present.

Actinomyces meyeri, a Common Agent of Actinomycosis

BACKGROUND

Actinomyces, particularly Actinomyces israelii, may cause indolent, persistent infections or represent normal mucosal flora, leading to management dilemmas.

MATERIALS AND METHODS

Prompted by a refractory Actinomyces meyeri infection complicating AIDS, clinical data for all Actinomyces isolates at our hospital laboratory since 1998 were analyzed.

RESULTS

A total of 140 cases had a positive result for Actinomyces cultures. Of 130 cases with adequate follow-up, 36 (28%) cases had end-organ or disseminated disease treated with prolonged antibiotics or surgery or both (Group 1). A. meyeri was more common than A. israelii (33% versus 8%; P < 0.05) in Group 1, particularly thoracic infections. Another 56 (43%) cases were considered local pathogens, treated with drainage only or short-course antibiotics (Group 2). Another 38 (29%) cases were deemed commensals (Group 3). Immunosuppression was less frequent in Group 1 versus Group 2 or 3 (P = 0.05) and human immunodeficiency virus or AIDS was uncommon. Foreign bodies or devices (Group 1 versus Group 2 or 3, P = 0.003) and alcoholism (Group 1 versus Group 2 or 3; P = 0.03) were associated with actinomycosis. Isolates from the central nervous system and musculoskeletal sites were more often treated as definitive disease; skin, abdominal or pelvic or single blood culture isolates were more likely commensals (all P < 0.05). Disease progression or recurrence did not occur in Groups 2 and 3, whereas Group 1 had complex and variable courses, including 2 deaths.

CONCLUSIONS

In the absence of disseminated or end-organ disease, avoiding prolonged therapy for Actinomyces isolates was not associated with adverse outcomes. Alcoholism or foreign bodies were associated with actinomycosis. A. meyeri may be a more common cause of actinomycosis than previously recognized.

Actinomyces meyeri Empyema: A Case Report and Review of the Literature

Actinomyces meyeri is an uncommon cause of human actinomycosis. Here, we report a rare case of empyema caused by A. meyeri. A 49-year-old male presented with a history of 10 days of dyspnea and chest pain. A large amount of loculated pleural effusion was present on the right side and multiple lung nodules were documented on radiological studies. A chest tube was inserted and purulent pleural fluid was drained. A. meyeri was isolated in anaerobic cultures of the pleural fluid. The infection was alleviated in response to treatment with intravenous penicillin G (20 million IU daily) and oral amoxicillin (500 mg every 8 hours) for 4 months, demonstrating that short-term antibiotic treatment was effective.

Actinomyces and related organisms in human infections

Actinomyces israelii has long been recognized as a causative agent of actinomycosis. During the past 3 decades, a large number of novel Actinomyces species have been described. Their detection and identification in clinical microbiology laboratories and recognition as pathogens in clinical settings can be challenging. With the introduction of advanced molecular methods, knowledge about their clinical relevance is gradually increasing, and the spectrum of diseases associated with Actinomyces and Actinomyces-like organisms is widening accordingly; for example, Actinomyces meyeri, Actinomyces neuii, and Actinomyces turicensis as well as Actinotignum (formerly Actinobaculum) schaalii are emerging as important causes of specific infections at various body sites. In the present review, we have gathered this information to provide a comprehensive and microbiologically consistent overview of the significance of Actinomyces and some closely related taxa in human infections.

A Case of Disseminated Infection due to Actinomyces meyeri Involving Lung and Brain

Actinomyces meyeri is rarely isolated in cases of actinomycosis. The identification of A. meyeri had historically been difficult and unreliable. With the recent development of 16S ribosomal RNA (16S rRNA) sequencing, Actinomyces species such as A. meyeri can be isolated much more reliably. A. meyeri often causes disseminated disease, which can be secondary to frequent pulmonary infections. A penicillin-based regimen is the mainstay of A. meyeri treatment, with a prolonged course usually required. Here, we report a case of pulmonary actinomycosis with brain abscess caused by A. meyeri that was initially thought to represent lung cancer with brain metastasis.

Fulminant course of unilateral emphysematous pyelonephritis revealing a renal actinomycosis caused by Actinomyces meyeri, an unknown cause of septic shock

The objective of this case report is to describe the first case of renal actinomycosis caused by Actinomyces meyeri presenting as severe emphysematous pyelonephritis and complicated by septic shock and multi-organ failure. Emphysematous pyelonephritis is a potentially life-threatening infection mostly described in diabetic patients and predominantly caused by uropathogenic bacteria. Actinomycosis is an uncommon chronic infection due to anaerobic gram-positive bacteria that unusually involves the urinary tract. We report the first case of emphysematous pyelonephritis caused by A. meyeri in a 75-year-old non-diabetic woman. The patient presented with an altered status, fever, nausea, and vomiting lasting for 2 days. A computed tomography scan revealed unilateral emphysematous pyelonephritis. She was rapidly admitted to intensive care unit for a septic shock with multiple organ dysfunctions. A conservative management consisting in renal percutaneous drainage, supportive measures, and prolonged adapted antibiotic therapy resulted in complete recovery. This case report illustrates that renal actinomycosis should be considered in case of emphysematous pyelonephritis given the good prognosis of this infection with conservative medical treatment.

Actinomycosis: etiology, clinical features, diagnosis, treatment, and management

Actinomycosis is a rare chronic disease caused by Actinomyces spp., anaerobic Gram-positive bacteria that normally colonize the human mouth and digestive and genital tracts. Physicians must be aware of typical clinical presentations (such as cervicofacial actinomycosis following dental focus of infection, pelvic actinomycosis in women with an intrauterine device, and pulmonary actinomycosis in smokers with poor dental hygiene), but also that actinomycosis may mimic the malignancy process in various anatomical sites. Bacterial cultures and pathology are the cornerstone of diagnosis, but particular conditions are required in order to get the correct diagnosis. Prolonged bacterial cultures in anaerobic conditions are necessary to identify the bacterium and typical microscopic findings include necrosis with yellowish sulfur granules and filamentous Gram-positive fungal-like pathogens. Patients with actinomycosis require prolonged (6- to 12-month) high doses (to facilitate the drug penetration in abscess and in infected tissues) of penicillin G or amoxicillin, but the duration of antimicrobial therapy could probably be shortened to 3 months in patients in whom optimal surgical resection of infected tissues has been performed. Preventive measures, such as reduction of alcohol abuse and improvement of dental hygiene, may limit occurrence of pulmonary, cervicofacial, and central nervous system actinomycosis. In women, intrauterine devices must be changed every 5 years in order to limit the occurrence of pelvic actinomycosis.

Mediastinitis by Actinomyces meyeri after oesophageal stent placement

Actinomyces meyeri is a Gram-positive anaerobic forming bacterium of the genus Actinomyces, part of the oral cavity's flora, and its classification remains an unresolved issue. It is an extremely rare cause of disease, occurring in middle-aged immunocompetent patients and frequently misdiagnosed as malignancy or lung abscess. A 56-year-old man diagnosed with oesophageal squamous cell carcinoma had an endoscopically placed stent to palliate his dysphagia. Two weeks later he presented with thoracalgia and fever, interpreted as a common lung infection. Owing to lack of improvement, additional examinations were undertaken revealing mediastinum involvement. Unlike the good prognosis usually associated with this infection, the patient eventually died, reflecting the aggressive nature of his underlying condition. To our knowledge, this is the first report of mediastinitis by A. meyeri, supporting the described propensity of this agent to disseminate, particularly to the thoracic cavity, although probably in this case with an iatrogenic contribution.

Actinomyces meyeri: from "lumpy jaw" to empyema

While the most common presentation of actinomycosis is cervicofacial disease, or "lumpy jaw syndrome," Actinomyces meyeri has a predilection for pulmonary disease as well as dissemination to distant organs. We describe a 61-year-old Caucasian male with a relapsing-remitting mandibular sinus tract who would go on to develop weight loss, dyspnea, and a cough productive of malodorous sputum. Imaging revealed a right lower lobe pneumonia and a large left sided empyema. He underwent thoracotomy and decortication on the left side, and 1 L of foul-smelling purulent fluid was drained. Culture grew Actinomyces meyeri. He completed an extended antibiotic course and had his teeth extracted with good clinical outcome.