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Antibiotics for Actinomyces


Actinomycetes - Actinomycosis - Actinobacteria
Actinomycetes, Actinomycete Antibiotics

Actinomycetes are a subgroup of the actinobacteria, which are Gram positive organisms with a high G+C ratio in their DNA. This group is very ancient, and branched off from the other groups very early in the evolutionary sequence.

The actinomycete group includes many familiar and important bacteria, includingMycobacterium (the causal agents of tuberculosis and leprosy), Corynebacterium (a common commensal on human skin, and therefore often recovered in bacterial air samples), and Streptomyces (the source of many antibiotics as well as the pleasant odor of freshly turned soil).


The actinomycetes are rod shaped or filamentous. Those that are rod shaped may form long, branching, chains of cells. Many actinomycetes form true filaments that branch and form colonies that look like fungi, although the diameter of the filaments is much smaller than that of the fungi. Filamentous forms produce spores that may be single, in short chains, or in very long chains that may form beautiful spirals.

There are both anaerobic and aerobic actinomycetes. Actinomyces is an important anaerobic genus (see below). The truly filamentous forms are predominantly aerobic.

Ecological Importance

Actinomycetes are abundant in soil, and are responsible for much of the digestion of resistant carbohydrates such as chitin and cellulose. They are responsible for the pleasant odor of freshly turned soil. Many actinomycetes and other actinobacteria are well known as degraders of toxic materials and are used in bioremediation. They are particularly well adapted to survival in harsh environments. Some are able to grow at elevated temperatures (>50°C) and are essential to the composting process.

Human Health Importance

Antibiotics
Many of our best known and most valuable antibiotics are produced by actinomycetes. These include novobiocin, amphotericin, vancomycin, neomycin, gentimycin, chloramphenicol, tetracycline, erythromycin, nystatin, etc. Some of these antibiotics target bacterial ribosomes and are used in treating respiratory infections, including Legionnaires' disease (tetracycline, erythromycin). Vancomycin attacks bacterial cell walls and deadly organisms such as MRSA (methicillin-resistant Staphylococcus aureus) (multiply drug resistant staph). Rifamycin targets bacterial RNA polymerase, and is useful against tuberculosis and leprosy. Amphotericin is one of the few antibiotics that attacks fungal membranes. These antibiotics generally do not affect human cells and therefore have few side effects. However, actinomycete metabolites such as adriamycin, prevent DNA replication, and are used in the treatment of cancer, while rapamycin is used to suppress the immune system to enable organ transplants.

Antibiotics Produced by Actinomycetes Fungi and Bacteria


Antibiotic

Isolated from

Active against

Amphomycin

Streptomyces canus

Gram-positive bacteria

Amphotericin B

Streptomyces nodosus

Yeast, fungi

Aterrimin

Bacillus subtilis

Gram-positive bacteria

Bacitracin

Bacillus subtilis

Gram-positive bacteria

Blasticidin S

Streptomucyes

Fungi

 

Griseochromogenes

 

Candicidin B

Streptomyces griseus

Yeast, fungi

Cephalosporins and

Cephalosporium acremonium

Staphylococcus, Steptococcus, E.coli, K. pneumoniae, Serratia

Chlorampheniod

Streptomyces venezuelae

Gram-positive and Gram-negative bacteria; Rickettsiae

Colistin

Bacilius colistinus

Gram-negative bacteria

Cycloheximide

Streptomyces griseus

Fungi

Cycloserine

Streptomyces orchidaceus

Gram-positive and TB bacteria

Dactinomycin

(Actinomycin D)

Streptomyces antibioticus

Gram-positive bacteria; anti-tumor principle

Erythromycin

Streptomuces erythreus

Gram-positive bacteria

Fusidic acid

Fusidium coccineum

Gram-positive bacteria

Gentamycin

Micromonospora purpurea

Gram-positive bacteria

Gramicidin

Bacillus brevis

Gram-positive bacteria

Griseofulvin

Penicillium griseofulvum

Fungi

Hygromycin

Streptomyces hygroscopicus

Gram-positive and Gram-negative and TB bacteria

Kanamycin

Streptomuces kanamyceticus

Gram-positive, Gram-negative and TB bacteria

 

Leucomycin

Streptomyces kitasoensis

Gram-positive bacteria

 

Lincomycin

Streptomuces lincolnensis

Gram-positive, Gram-negative and TB bacteria

Neomycins

Streptomyces fradiae

Gram-positive, Gram-negative and TB bacteria

Novobiocin

Streptomyces niveus

Gram-positive bacteria

Nystatin

Streptomyces noursei

Fungi and yeast

Oleandomycin

Streptomyces antibioticus

Gram-positive, Gram-negative and TB bacteria; protozoa

Penicillin and its

Chemical derivatives

Penicilliium chrysogenum

Gram-positive bacteria

Polymyxin B

Aerobacillus polymyxa

Gram-negative bacteria

Pristinamycin

Streptomyces sp.

Gram-positive bacteria

Rifomycin SV

Streptomyces mediterranei

Gram-positive and TB bacteria

Ristocetin

Nocardia lurida

Gram-positive bacteria

Spiramycin

Streptomyces ambofaciens

Gram-positive and Gram-negative bacteria; Rickettsiae

Staphylomycin

Streptomyces virginiae

Gram-positive bacteria

Stendomycin

Streptomyces endus

Gram-positive and
Gram-negative bacteria

Streptomycin and chemical derivatives

Streptomyces griseus

Gram-positive, Gram-negative and TB bacteria

Tetracycline and chemical derivatives

Streptomyces aureofaciens

Gram-positive and Gram negative bacteria; Rickettsiae

5-Hydroxytetracycline

Streptomyces rimosus

Gram-positive and Gram-negative bacteria; Rickettsiae


Melon canker caused by Mycosphaerella and powdery mildews caused by Erysiphe. Griseofulvin is a systemic fungicide since the antibiotic permeates plant tissues uniformly and forms a barrier to the penetration by pathogenic fungi.

Aureofungin is a broad spectrum antifungal antibiotic with the unique property of inhibiting growth of a large number of phytopathogens. It was once commercially produced in India at the Hindustan Antibiotics, Pimpri, Poona. The antifungal activity of the antibiotic has been demonstrated in pure cultures on Pyricularia oryzae, Helminthosporium oryzae, H. turcicum, H. nodulosum, Alternaria tenuis, Curvularia lunata, Verticillium alboatrum, Phytophthora citrophthora, Aspergillus niger, A. Fumigatus, Candida albicans, Cryptococcus neoformans, Trichophyton mentagrophytes and T. rubrum. The minimum inhibitory concentration of the antibiotic ranges from 0.005 to 1 mg/ml. The antibiotic is insoluble in water but soluble in alcohols and can be made soluble in water at alkaline pH. Its effectiveness against citrus gummosis incited by Phytophthora sp., powdery mildew of apple caused by Podosphaera leucotricha and diseases of grapes such as powdery mildew, downy mildew and the anthrachnose is well established. It has also been reported that aureofungin has potentialities in the control of seed-borne infection and seedling blight caused by Helminthosporium oryzae and Pyricularia oryzae disease of ragi, and many other disease including post­harvest and storage diseases.

Some antibiotics are of limited application such as cycloheximide (actidione), blasticidin-S, kasugamycin and streptomycin. Cycloheximide has been shown to be active against leaf spots, powdery mildews and blister rust of pine while blasticidin-S has shown promise against P. oryzae. Streptomycin has proved effective against diseases caused by Erwinia, Xanthomonas, Pseudomonas, Corynebacterium, Agrobacterium, Pseudoperonospora, Peronospora and Sphaerotheca.

In Japan, agriculturally useful antibiotics have, been widely used to protect plants against diseases and pests. Some of the examples are cited below:
(1) Cycloheximide (from Streptomyces griseus) as a wettable powder against onion downy mildew and shoot blight of Japanese larch,
(2) Kasugamycin (from Streptomyces kasugaensis) as dust against rice blast,
(3) Polyoxins (produced by Streptomyces cacaoi var asoensis) as dust, wettable powder and emulsion against rice sheath blight and fungal diseases of fruits and vegetables,
(4) Validamycin A (from Streptomyces hygroscopicus var. limoneus) as dust against rice sheath blight,
(5) Streptomycin (from Streptomyces griseus) as wettable powder or liquid against bacterial diseases of fruits and vegetables,
(6) Oxytetracycline (from Streptomyces viridifaciens) as wettable powder against citrus canker and peach bacterial leaf spot and
(7) Tetranactin as emulsion against carmine mite of fruits and tea. The primary sites of action of these antibiotics relate to chitin synthesis of cell wall, cation leakage from mitochondria, biosynthesis of inositol and protein and DNA synthesis. Limitations in the use of antibiotics in agriculture are difficulties in analysis because they are used in small amounts and there is a likelihood of development of plant pathogens resistant to antibiotics. Therefore, the use of chemicals and antibiotics in alternate years has been recommended to overcome such a possibility.

Antibiotics are also widely used as growth stimulants in poultry and livestock feeds. The use of aureomycin, terramycin and penicillin at the rate of 5-20 g/ ton of wheat increases the rate of growth of farm animals from 5 to 50%. Although the mechanism behind such stimulating effect of antibiotics is not known, it is believed that they may kill unwanted bacteria in the intestine and also increase the availability of vitamin B12.

Infections
Members of the genus Actinomyces are normal commensal members of human oral cavities. They can cause serious infections when they invade tissues through breaks in the oral mucosa. The disease is becoming less common, but is still present in the USA, especially in inner city populations.

Nocardia asteroides is an actinomycete that is common in soil, and can cause infection via the respiratory route. Infection is opportunistic, and relies on deficits in cell-mediated immunity. Other species of Nocardia may also be involved.

Hypersensitivity pneumonitis (HP)
Thermophilic actinomycetes are the most common cause of HP. Farmer's lung disease is HP resulting from exposure to hay that has become colonized with thermophilic actinomycetes, which produce an abundance of airborne spores. Clouds of these spores are released when farmers (especially dairy farmers) handle stored hay in winter and early spring. The same fungi that cause molding of hay are common inhabitants of soil, and have also been documented to colonize ventilation systems, clothes dryers, refrigerator drip pans, and any other site that combines heat, cellulosic or other carbohydrate material, and water. Common species include Thermoactinomyces vulgaris, Saccharopolyspora rectivirgula,Thermoactinomyces viridis and others.

Volatile Organic Compounds (VOCs)
The odor of freshly turned soil is the result of geosmin, a volatile organic compound produced by actinomycetes. Geosmin is also produced by some cyanobacteria and produces an earthy taste in drinking water. Some fungi also produce geosmin, which can impart the same earthy taste to wine made from moldy grapes. In general, people find the geosmin odor pleasant in soil. However, one indoor air research group is investigating the possibility that exposure to geosmin is related to building-related symptoms. The data at present is too limited for conclusions. However, in the future, collection of samples that will reveal these organisms might be recommended.

Source - www.planetmold.com, www.microbiologyprocedure.com

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