September 2000 Molecule of the Month
by David S. Goodsell
Previous Features
Lysozyme protects us from the ever-present danger of bacterial infection. It is a small enzyme that attacks the protective cell walls of bacteria. Bacteria build a tough skin of carbohydrate chains, interlocked by short peptide strands, that braces their delicate membrane against the cell's high osmotic pressure. Lysozyme breaks these carbohydrate chains, destroying the structural integrity of the cell wall. The bacteria burst under their own internal pressure.
Alexander Fleming discovered lysozyme during a deliberate search for medical antibiotics. Over a period of years, he added everything that he could think of to bacterial cultures, looking for anything that would slow their growth. He discovered lysozyme by chance. One day, when he had a cold, he added a drop of mucus to the culture and, much to his surprise, it killed the bacteria. He had discovered one of our own natural defenses against infection. Unfortunately, lysozyme is a large molecule that is not particularly useful as a drug. It can be applied topically, but cannot rid the entire body of disease, because it is too large to travel between cells. Fortunately, Fleming continued his search, finding a true antibiotic drug five years later: penicillin.
Staphylococcus
Once MRSA was just a simple germ
Staphylococcus - A genus of spherical bacteria of the family Micrococcaceae, is the best known species of which are universally present in very great numbers, on the mucous membranes and skin of humans, and some other warm-blooded animals. The term staphylococcus, generally used for all the species, refers to the cell's habit of assembling in grapelike clusters. Staph, is a commonly used slang name for this bug.
Staphylococci are microbiologically characterized as gram-positive - in young cultures, and non-spore-forming, non-motile, facultative anaerobes - not requiring oxygen.
The cells average 1 μm - micrometer; 1 μm = 0.00l mm, in diameter and are usually clustered.
Micrometer - also called Micron, metric unit of measure for length equal to 0.00l mm, or about 0.000039 inch. Its symbol is μm, or one millionth of a meter. The micrometer is commonly employed to measure the thickness or diameter of microscopic objects, such as microorgaisms and colloidal particles. Minute distances, as, for example, the wavelengths of infrared radiation, are also given in micrometers.
Significant to humans, are two variants of the species Staphylococcus. Aureus, an important agent of wound infections, boils, pustules, and other human skin infections, and one of the most common causes of food poisoning. Staphylococcus. Aureus, also causes udder inflammation, or mastitis, in domestic animals and breast infections in women.
It has become a difficult hospital pathogen because of its resistance to antibiotics. Staphylococcus. Aureus epidermis is a milder pathogen that is opportunistic in persons with lowered resistance. Many strains of Staphylococcus Aureus are now resistant to penicillin. This is because Staphylococcus Aureus has evolved or mutated, simply by accident, to make a substance called ß-lactamase - pronounced beta-lactamase, that degrades penicillin, destroying its antibacterial activity. Tests done on any Staphylococcus Aureus grown from such specimens can then decide how sensitive the organisms is to antibiotics and if it is a Methicillin resistant (MRSA) organism. These test usually take 2-3 days.
Bactericidal - Bactericides - Capable of killing bacteria. Common bactericides are some antibiotics, antiseptics, and disinfectants. many cleaning products are sold, that claim or state to kill all or 99% of all known germs. There are many antibiotics, antiseptics, and disinfectants that will readily kill bacteria, but may also kill or damage the host you wish to cure. Bleach will kill 99.9% of all known micro-organisms but will also kill any person who hosts the germs, you want to attack.
Aerobic bacteria, Staphylococcus aureus, cultured on an agar plate for drug sensitivity test in an anaerobic environment. The toxin produced by Staphylococcus aureus causes the illness "staphylococcal intoxication". Symptoms of this intoxication include nausea, vomiting, and diarrhea.
Gram-Positive Bacterial Infections, Staphylococcal Infections
http://search.yahoo.com/search?ei=UTF-8&q=mrsa&fr=megaup&p=mrsa+pictures&rs=2&fr2=rs-bottom
ไม่มีความคิดเห็น:
แสดงความคิดเห็น