Hey !
Hello one and All
This is the third random selection of Organisms by Concept of Microbiology
Known as
" Actinomyces "
A Filamentous Bacterium
So without wasting time Dive in 🌊 it with our Concept Of Microbiology
Ready
Get set Go ,
1)Actinomyces :
Actinomyces is a genus of the Actinobacteria class of bacteria. They all are gram-positive. Actinomyces species are facultatively anaerobic (except A. meyeri and A. israelii both 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, beam and mykes, fungus).
Bacterial Classification :
Domain : Bacteria
Phylum : Actinobacteria
Class : Actinobacteria
Order : Actinomycetales
Family : Actinomycetaceae
Genus : Actinimyces
Species : bovis , canis , etc.
Introduction :
Actinomyces species are ubiquitous, occurring in soil and in the microbiota of animals, including the human microbiota.
They are known for the important role they play in soil ecology; they produce a number of enzymes that help degrade organic plant material, lignin, and chitin.
Thus their presence is important in the formation of compost. Certain species are commensal in the skin flora, oral flora, gut flora, and vaginal flora of humans and livestock. They are also known for causing diseases in humans and livestock, usually when they get an opportunity to gain access to the body's interior through wounds.
As with other opportunistic infections, people with immunodeficiency are at higher risk. In all of the preceding traits and in their branching filament formation, they bear similarities to Nocardia.
Like various other anaerobes, Actinomyces species are fastidious and thus not easy to culture and isolate.
Clinical laboratories do culture and isolate them, but a negative result does not rule out infection, because it may be due simply to reluctance to grow in vitro.
Ecology :
- Actinomycetes are classified as a group of gram-positive bacteria that are unique for their spore forming abilities and formation of mycelia structures.
- They show marked chemical and morphological diversity but form a distinct evolutionary line of organisms that range from coccoid and pleomorphic forms to branched filaments.
- These bacteria have been noted to serve as rich reservoirs of medicinal antibiotics and are therefore extremely relevant to scientists, pharmaceutical industries and agricultural industries.
The genus normally presents itself in the oral cavity. A study on biofilm growth of the Actinomyces species found that in the presence of Actinomyces gerencseriae, Lactobacillus plantarum and Lactobacillus rhamnosus grew 4-20 times more than in a presence of another bacterial species in the oral community. Lactobacillus plantarum and Lactobacillus rhamnosus are examples of bacterial species commonly found in the oral cavity of humans, and their accelerated growth in this case demonstrate that overall, A. gerencseriae promotes growth in its ecological niche. Actinomyces gerencseriae are primarily microaerophilic, though some strains appear to be anaerobic. The significance of research in this area reveals itself when the features of the Lactobacillus genus, which can tolerate and utilize lactic acid in plaque under anaerobic conditions, are coupled with the growth promoting effects of the Actinomyces genus. Actinomyces promoted the growth of lactobicilli by providing a biofilm matrix.
Material & Methods :
- First, soil slurry is made by suspending 1 gm of the collected dry soil in 10 ml distilled water. The slurry is mixed by vortexing for 2 minutes.
- Four 1 in 10 fold serial dilutions is made from the slurry in duplicates.
- 1 ml portions of each dilution, are then plated by spreading on the set agar plates (Actinomycete Isolation Agar supplemented with cyclohexamide (50 μg/ml) and nystatin (50 μg/ml) and Chitin agar/ Starch Casein Agar).
- All spread plates are labelled and incubated at 25 ̊C for a period of 7 to 14 days.
- On day 14, the number of colonies formed in each dilution of both groups of, are counted and recorded.
- All plates are carefully observed under the microscope to detect diversity in colonies formed. The richness, evenness and diversity index, are also calculated and recorded.
- Different colony types are then picked out with sterile forceps and streaked out on glucose yeast extract agar plates, to obtain pure single colonies.
- The streaked plates are then incubated and subsequently tested for antibiotic production.
Cell Structure :
The entirety of the Actinomyces genus consists of Gram positive bacteria. These Gram positive bacilli bacteria possess cell walls consisting of a large external peptidoglycan layer threaded with teichoic acids and lipoteichoic acids. This peptidoglycan layer is separated from the cell membrane bilayer by the periplasmic space. The cell membrane bilayer is interspersed with important membrane proteins.
When Actinomyces was initially discovered in the late 1800s as a source of oral infection first in cows (A. bovis) and then humans (A. Israelii), it was mistakenly identified as a fungal genus. The reason for this was the tendency for Actinomyces species to grow in a filamentous manner, and form hyphaes similar to eukaryotic fungi. Although this has been the typical classification of Actinomyces, several more recently discovered of these species lack the ‘typical’ branching rod appearance. 3
Actinomyces gerencseriae is a nonmotile, Gram positive bacterial species. The average Actinomyces gerencseriae colony is around 0.2 mm in diameter, circular in shape, are branching filamentous and white in color. Actinomyces gerencseriae have an incubation period of 2 days and is a non-spore forming bacterial species.
Metabolisms :
The ability to metabolize certain substances is an important distinguishing factor for the different Actinomyces species. The primary tests used in research include the ability for nitrate reduction, CAMP test reaction, as well as tests for the production of β-galactosidase, β-NAG, β-xylosidase, and 𝛼-fucosidase. Esculin hydrolysis is also a useful test for distinguishing certain species within the genus. Actinomyces as a genus has also been found to produce lactic acid in addition to succinic acid.
A common problem in recent years after the determination of A. gerencseriae as a separate species from A. israelii has been the separation of the two on a biochemical basis. It has been discovered, however, that these two species can be distinguished by their differential abilities to ferment different metabolites. A. israelii was found to possess the ability to ferment arabinose, while A. gerencseriae cannot. 3 Additional research has showed that these two species show differing abilities in the degradation of two mannopyranoside isomers. A. israelii can degrade the β-mannoside isomer, while A. gerencseriae can degrade the 𝛼-mannoside isomer.
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.
Actinomycosis is an infrequent invasive bacterial disease that has been recognized for over a century. Actinomyces spp. are filamentous Gram-positive bacilli, mainly belonging to the human commensal flora of the oropharynx, gastrointestinal tract, and urogenital tract. 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. Of note, in any site, actinomycosis frequently mimics malignancy, tuberculosis, or nocardiosis, as it spreads continuously and progressively, and often forms a cold abscess
Antibiotic Resistance :
Drug resistance is not considered a problem in actinomycosis. Indeed, Actinomyces spp. are usually extremely susceptible to beta-lactams, and especially penicillin G or amoxicillin. As a consequence, penicillin G or amoxicillin are considered drugs of choice for the treatment of actinomycosis.
Third-generation cephalosporins are less frequently used even if they are considered to be active on A. israelii; however, it is important to note that some species are resistant to ceftriaxone (Actinomyces europaeus and Actinomyces graevenitzii).
Piperacillin–tazobactam, imipenem, and meropenem are considered to be active, but the use of these broad-spectrum antibiotics should be limited to avoid acquisition of resistant flora. Oxacillin, cloxacillin, and cephalexin, a first-generation cephalosporin, are not considered to be active.
Metronidazole and aminoglycosides have no in vitro activity against Actinomyces. Fluoroquinolones (ciprofloxacin and moxifloxacin) are usually considered to be inactive, but data are limited and controversial. Doxycycline is considered to have a poor activity on Actinomyces spp., but clinical successes have been reported with this drug. Macrolides and clindamycin have been used successfully as alternatives. As Actinomyces spp. do not produce beta-lactamases, it is not useful to combine amoxicillin with beta-lactam inhibitors such as clavulanic acid, except if co-pathogens such as Enterobacteriaceae are involved in the disease.
Infection :
Actinomycosis is a rare infectious bacterial disease caused by Actinomyces species. About 70% of infections are due to either Actinomyces israelii or A. gerencseriae. Infection can also be caused by other Actinomyces species, as well as Propionibacterium propionicus, which presents similar symptoms.
Results :
Actinomycosis is a rare, infectious disease in which bacteria spread from one part of the body to another through body tissues. Over time, it can result in linked abscesses, pain, and inflammation. It can affect the skin or deeper areas within the body and sometimes the blood.
Comments
Post a Comment