Actinomycetes.pptx...microbiology.........

Microbiology

1. Actinomycete s

2. Objective Introduction Classification Morphology & Identification Actinomycosis Pathology Clinical signs Diagnosis Treatment References

3. Introduction Actinomyces  is a genus of the Actinobacteria class of bacteria. They all are Gram- positiv . Actinomyces species are facultatively anaerobic (except   A. meyeri  and   A. israelii  are obligate anaerobe) , and they grow best under anaerobic conditions. Actinomyces  species may form endospores, and while individual bacteria are rod-shaped,  Actinomyces  colonies form fungus-like branched networks of hyphae The aspect of these colonies initially led to the incorrect assumption that the organism was a fungus and to the name  Actinomyces , "ray fungus" (from Greek  actis , ray or beam, and  mykes , fungus). Actinomycetales are generally gram-positive and anaerobic and have mycelium in a filamentous and branching growth pattern . Some actinobacteria can form rod- or coccoid -shaped forms , while others can form spores on aerial hyphae (Abdel- fattah and Olama ., 2002).

4. Classification Classification :- Domain : bacteria Phylum : actinobacteria Class : actinobacteria Order : actinomycetaceae Family : actinomycetaceae Genus : actinomyces

5. Morphology & Identification Most strains of a israelii and the other agents of actinomycosis are facultative anaerobes that grow best in an atmosphere with increased carbon dioxide . On enriched medium , such as brain – heart infusion agar , young colonies (24-48 hours) produce gram – positive substrate filament that fragment into short chains , diphtheroids , coccobacilli . After a week , these “spider “colonies develop into white , heaped-up “moral tooth “ colonies . In thioglycolate broth , A israelii grows below the surface in compact colonies . Species are identified based on cell wall chemotype . diverse group , gram- positive , non-motile , non- sporing , non-capsulated , straight ; curved or pleomorphic , arranged in chains or branching filaments , related to mycobacteria and corynebacteria , mycelium – tangled mass of hyphae m found in nature ( Essaid et al., 2016)

6. Unicellular like bacteria but produce mycelium which is non septate & more slender Don’t contain chitin and cellulose . They produce hyphae and conidia / sporangia like fungi . Certain actinomycetes whose hyphae undergo segmentation resemble bacteria , both morphology and physiologically . Note : morphology resembles to fungi , cellular organization typical of bacteria .

7. Actinomycosis Actinomycosis :- is a chronic suppurative and granulomatous infection that produces pyogenic lesions with interconnecting sins tracts that contain granules composed of microcolonices of the bacteria embedded in tissue elements . The etiologic agents are several closely related members of the normal flora of the mouth and gastrointestinal tract . Most cases are due to Actinomyces israelii , Actinomyces naeslundii , and related anaerobic or facultative bacteria . Based on the site of in volvement, the 3 common forms are cervicofacial , thoracic , and abdominal actinomycosis . Regardless of site , infection is initiated by trauma that introduces these endogenous bacteria into the mucosa . Often , in addition to the primary agent of actinomycosis , there are concomitant bacteria present . Some of these are relatively fastidious gram-negative bacilli such as Actinobacillus actinomycetemcomitans , haemophilus aphrophilus , eikenella corrodens , capnocytophaga species . Occasionally , staphylococci , streptococci , or enteric gram – negative bacilli are found .

8. pathology Actinobacteria are normally present in the gums, and are the most common cause of infection in dental procedures and oral abscesses. Many  Actinomyces  species are opportunistic pathogens of humans and other mammals, particularly in the oral cavity. In rare cases, these bacteria can cause actinomycosis, a disease characterized by the formation of abscesses in the mouth, lungs, or the gastrointestinal tract. Actinomycosis is most frequently caused by  A. israelii , which may also cause endocarditis, though the resulting symptoms may be similar to those resulting from infections by other bacterial species.  Aggregatibacter actinomycetemcomitans  has been identified as being of note in periodontal disease (Riedel S et al ., 2019).

9. Clinical signs The genus is typically the cause of oral- cervicofacial disease. It is characterized by a painless "lumpy jaw". Lymphadenopathy is uncommon in this form of the disease. Another form of actinomycosis is thoracic disease, which is often misdiagnosed as a neoplasm, as it forms a mass that extends to the chest wall. It arises from aspiration of organisms from the oropharynx. Symptoms include chest pain, fever, and weight loss. Abdominal disease is another manifestation of actinomycosis. This can lead to a sinus tract that drains to the abdominal wall or the perianal area. Symptoms include fever, abdominal pain, and weight loss ( Pelvic actinomycosis is a rare but proven complication of use of intrauterine devices. In extreme cases, pelvic abscesses might develop. Treatment of pelvic actinomycosis associated with intrauterine devices involves removal of the device and antibiotic treatment ( Sharma S et al ., 2020).

10. Diagnosis Laboratory Tests Organisms may be demonstrated as a granule or as scattered branching gram-positive filaments in the pus Anaerobic culture is necessary to distinguish from  Nocardia Histopathology exam of affected tissue and bone is useful in identifying organisms, which are fastidious and slow to culture Imaging Studies Chest radiograph shows areas of consolidation and, in many cases, pleural effusion Abdominal pelvic CT scanning reveals an inflammatory mass that may extend to involve bone

11. Treatment Penicillin G Drug of choice 10–20 million units intravenously for 4–6 weeks followed by penicillin V, 500 mg four times daily orally Alternatives include Ampicillin, 12 g/day intravenously for 4–6 weeks, followed by amoxicillin, 500 mg three times daily orally  or Doxycycline, 100 mg twice daily intravenously or orally Sulfonamides such as sulfamethoxazole may be an alternative regimen at a total daily dosage of 2–4 g Therapy should be continued .

12. References Abdel- fattah YR and olama ZA 2002 . L- asparaginase production by pseudomonas aeruginosa in solid state culture : evaluations and optimization of culture conditions using factorial designs . Process biochemistry 38 (1) : 115-122 Essaid ait barka et al . (2016) .taxonomy , physiology , and natural products of actinobacteria . Riedel S, Hobden JA, et al (Eds.) (2019). Infections caused by anaerobic bacteria. In Jawetz, Melnick, & Adelberg’s Medical Microbiology (28th ed.) McGraw-Hill. Russo TA. (2018). Actinomycosis. In Jameson J, Fauci AS, et al (Eds.), Harrison’s Principles of Internal Medicine (20th ed.) McGraw-Hill.

13. 5. Ryan KJ (Ed.) (2017). Actinomyces and nocardia. In Sherris Medical Microbiology (7th ed.) McGraw-Hill 6. Sharma S, Hashmi M, Valentino D. (2020). Actinomycosis. StatPearls. Retrieved Nov 25, 2020 7. Valour F, Sénéchal A, et al (2014). Actinomycosis: etiology, clinical features, diagnosis, treatment, and management. Infect Drug Resist, 7, 183–197 .