Antimicrobial Susceptibility of Clinical Oral Isolates of Actinomyces spp.

Actinomyces species play an important role in the pathogenesis of oral diseases and infections. Susceptibility testing is not always routinely performed, and one may oversee a shift in resistance patterns. The aim of the study was to analyze the antimicrobial susceptibility of 100 well-identified clinical oral isolates of Actinomyces spp. against eight selected antimicrobial agents using the agar dilution (AD) and E-Test (ET) methods. We observed no to low resistance against penicillin, ampicillin-sulbactam, meropenem, clindamycin, linezolid and tigecycline (0–2% ET, 0% AD) but high levels of resistance to moxifloxacin (93% ET, 87% AD) and daptomycin (83% ET, 95% AD). The essential agreement of the two methods was very good for benzylpenicillin (EA 95%) and meropenem (EA 92%). The ET method was reliable for correctly categorizing susceptibility, in comparison with the reference method agar dilution, except for daptomycin (categorical agreement 87%). Penicillin is still the first-choice antibiotic for therapy of diseases caused by Actinomyces spp.

Actinomycosis in head and neck region of pediatric patients: a review

The majority of cases of actinomycosis are of odontogenic origin and related to the perimandibular region with other sites of primary actinomycosis in the head and neck region include the tongue, paranasal sinuses, middle ear, larynx, lacrimal passage, and thyroid gland. Actinomycosis is an uncommon infection caused by Actinomyces species, facultative anaerobic bacteria that are part of the normal flora in the oropharynx, gastrointestinal tract, and female genital tract. The risk factors for actinomycosis in the pediatric age group are dental caries, trauma, debilitation, and poorly controlled diabetes mellitus. The pathogenesis of the actinomycosis in the head and neck region is often unclear. The hallmark of actinomycosis is the spread of infection which fails to respect the tissue or fascial planes. The organism causing actinomycosis is often difficult to isolate from culture and the differential diagnosis is extensive which prompts clinicians to name the actinomycosis the masquerader of the head and neck area. This clinical entity in pediatric patients may mimic malignancy or granulomatous disease in the head and neck region. Clinicians must be aware of typical presentations of actinomycosis in the head and neck region. Bacterial cultures and histopathological study are the cornerstones of the diagnosis of actinomycosis, however, particular conditions are needed to find the exact diagnosis. The treatment of actinomycosis includes a combination of surgery and antibiotic therapy. Surgery is an important adjunctive to medical therapy in patients with extensive lesions of actinomycosis. Actinomyces species are uniformly susceptible to penicillin. This review article discusses the etiopathology, epidemiology, clinical manifestations, diagnosis, and current treatment of the actinomycosis in the head and neck region of pediatric patients.

943. Epidemiology of Actinomycosis in a Tertiary Care Cancer Center

Background Actinomyces are human commensals with significant pathogenic potential. The aim of this study was to determine the epidemiology of Actinomycosis in a tertiary care cancer center and identify species most commonly associated with invasive disease. Methods We retrospectively reviewed all patients referred to our institution with suspected or documented solid or hematological malignancies and positive cultures for Actinomyces species from July 2007 to June 2020 (13 years). Species identification was performed by VITEK® automated system (bioMerieux Inc.). Probable invasive actinomycosis was defined as cases with consistent clinical presentation, suggestive radiographic findings, and a positive culture from a nonsterile site, but lack of histopathological confirmation. Proven invasive actinomycosis was defined as the presence of consistent clinical symptoms, suggestive radiographic findings, a positive culture and histopathological confirmation, or cultures from sterile site without histopathological confirmation. Contaminants were considered positive cultures from sterile or non-sterile site without evidence of disease. Results Of 233 cases with positive cultures 194 (83.3%) were considered contaminants and 39 (16.7%) diagnostic of invasive actinomycosis. Of 39 cases of invasive actinomycosis, 64% were documented in patients with solid tumors, 13% in hematological malignancy and 23% among individuals without proven malignancy, 25 (64%) were probable and 14 (36%) proven. Of patients with proven/probable actinomycosis 27 (69%) had polymicrobial growth. Abdominopelvic was the most frequent site of invasive actinomycosis. A. odontolyticus was the most common species isolated (41%) followed by A. meyeri (28%) in patients with invasive disease, and A. odontolyticus (42%) among contaminants. Conclusion The majority of positive cultures for Actinomyces species were considered contaminants. In our cohort Invasive actinomycosis affected mainly patients with solid tumors. Abdominopelvic was the most common site of invasive disease. Species most commonly associated with invasive actinomycosis were A. odontolyticus followed by A. meyeri with A. israelii isolated less frequently. Disclosures All Authors: No reported disclosures

218. A 5-Year Retrospective Study of Actinomyces Odontolyticus Bacteraemia

Background Actinomyces species are Gram positive anaerobic, non-sporulating, non-acid fast, non-motile, irregularly staining bacterium. It is associated with a wide range of infections including; dental caries, abscesses, intraabdominal and bloodstream infections. A. odontolyticus normally a commensal organism found in the mouth, was first isolated from dental caries in 1958. The incidence of Actinomyces odontolyticus bacteremia is less common. Methods We are reporting 15 cases of isolated A. odontolyticus blood stream infection at HMC, State of Qatar from 1/1/2016 to 1/11/2020. We aim to describe their clinical characteristic, risk factors and treatment outcome. Results Our patients with bacteraemia fall into one of two groups. The first group consists of paediatric patients with unremarkable co-morbidities. The second group includes older adults, often with co-morbidities that pre-dispose to infection, such as diabetes mellitus or hypertension. Fever was the main presenting sign and symptom in 12 patients (80%). Nine of the patients were females (60%). 13 patients (86%) received antibiotics. Maximum duration of antibiotics was 60 days and minimum duration was three days. The infectious disease team was consulted for six patients (40%). One patient died while the other 14 recovered uneventfully with a case fatality rate of 6.6%. Reported cases of Actinomyces odontolyticus bacteraemia in Hamad Medical Corporation between 1/1/2016 to 1/11/2020 Minimal inhibitory concentrations (MICs) of selected antibiotics against A. odontolyticus, including interpretations and breakpoints, as reported by the AMRHAI reference unit, PHE Colindale Conclusion Clinicians of all specialties need to be aware of the rising number of reports of Actinomyces species bacteraemia due to widespread availability of molecular identification techniques, including MALTI-TOF. 3 Furthermore, more studies are needed to determine guidelines for treating these resilient microbes Disclosures All Authors: No reported disclosures

Perianal Actinomycosis: A Surgeon’s Perspective and Review of Literature

Actinomycosis is a serious suppurative, bacterial infection caused by the gram-positive anaerobic Actinomyces species. Primary perianal actinomycosis is rare and challenging for the colorectal surgeon. We aimed to present our experience and compare this with available literature. All patients with isolated Actinomyces on microbiology reports, between January 2013 and February 2021, were identified and reviewed. Data collection was retrospective based on electronic patient records. The site of infection and treatment strategy were examined. Perianal cases were evaluated in depth. All publications available in the literature were interrogated. Fifty-nine cases of positive actinomycosis cultures were reviewed. Six cases of colonization were excluded. Actinomyces turicensis was the most common organism isolated. Five cases of perianal actinomycosis were identified requiring prolonged antibiotic and surgical therapy. Twenty-one studies, most case reports, published since 1951 were also reviewed. Diagnosis of perianal actinomycosis may be challenging but should be suspected particularly in recurrent cases. Prolonged bacterial cultures in anaerobic conditions are necessary to identify the bacterium. An extended course of antibiotic therapy (months) is required for eradication in certain cases.

Clinical Characteristics of Actinomyces viscosus Bacteremia

Background and Objectives: Actinomyces species are part of the normal flora of humans and rarely cause disease. It is an uncommon cause of disease in humans. The clinical features of actinomycosis have been described, and various anatomical sites (such as face, bones and joints, respiratory tract, genitourinary tract, digestive tract, central nervous system, skin, and soft tissue structures) can be affected. It is not easy to identify actinomycosis because it sometimes mimics cancer due to under-recognition. As new diagnostic methods have been applied, Actinomyces can now more easily be identified at the species level. Recent studies have also highlighted differences among Actinomyces species. We report a case of Actinomyces viscosus bacteremia with cutaneous actinomycosis. Materials and Methods: A 66 years old male developed fever for a day with progressive right lower-leg erythematous swelling. Blood culture isolates yielded Actinomyces species, which was identified as Actinomyces viscosus by sequencing of the 16S rRNA gene. In addition, we searched for the term Actinomyces or actinomycosis cross-referenced with bacteremia or “blood culture” or “blood stream” from January 2010 to July 2020. The infectious diseases caused by species of A. viscosus from January 1977 to July 2020 were also reviewed. Results: The patient recovered well after intravenous ampicillin treatment. Poor oral hygiene was confirmed by dental examination. There were no disease relapses during the following period. Most cases of actinomycosis can be treated with penicillin. However, clinical alertness, risk factor evaluation, and identification of Actinomyces species can prevent inappropriate antibiotic or intervention. We also compiled a total of 18 cases of Actinomyces bacteremia after conducting an online database search. Conclusions: In summary, we describe a case of fever and progressive cellulitis. Actinomyces species was isolated from blood culture, which was further identified as Actinomyces viscosus by 16S rRNA sequencing. The cellulitis improved after pathogen-directed antibiotics. Evaluation of risk factors in patients with Actinomyces bacteremia and further identification of the Actinomyces species are recommended for successful treatment.

Applications and Restrictions of Integrated Genomic and Metabolomic Screening: An Accelerator for Drug Discovery from Actinomycetes?

Since the golden age of antibiotics in the 1950s and 1960s actinomycetes have been the most prolific source for bioactive natural products. However, the number of discoveries of new bioactive compounds decreases since decades. New procedures (e.g., activating strategies or innovative fermentation techniques) were developed to enhance the productivity of actinomycetes. Nevertheless, compound identification remains challenging among others due to high rediscovery rates. Rapid and cheap genome sequencing as well as the advent of bioinformatical analysis tools for biosynthetic gene cluster identification in combination with mass spectrometry-based molecular networking facilitated the tedious process of dereplication. In recent years several studies have been dedicated to accessing the biosynthetic potential of Actinomyces species, especially streptomycetes, by using integrated genomic and metabolomic screening in order to boost the discovery rate of new antibiotics. This review aims to present the various possible applications of this approach as well as the newly discovered molecules, covering studies between 2014 and 2021. Finally, the effectiveness of this approach with regard to find new bioactive agents from actinomycetes will be evaluated.

Pelvic actinomycosis mimicking an advanced ovarian carcinoma: a rare case report with review of literature

Actinomycosis is a rare subacute to chronic granulomatous bacterial infection caused by actinomyces species. Pelvic actinomycosis is rare, often pretends to be malignant and therefore it is difficult to diagnose preoperatively. Here we discuss a case of a 45-years-old female who was operated for a pelvic mass thought to be malignant, but on histopathological examination it turned out to be a case of ovarian actinomycosis.

Endobronchial actinomycosis in a child during COVID-19 pandemic

Actinomycosis is a rare, indolent and invasive infection caused by Actinomyces species. Pulmonary actinomycosis is very rarely seen in the paediatric population. The classic radiological presentation of thoracic involvement of actinomycosis includes lower lobe consolidation, empyema and periostitis of the ribs. We report a case of endobronchial pulmonary actinomycosis in a child diagnosed on endobronchial biopsy and broncho-alveolar lavage taken during bronchoscopy. Bronchoscopy can be dangerous when performed on these cases, as there is a risk of severe bleeding and large airway obstruction, as was the case with this patient.