Penicillin Gram positive

Plasmid-mediated resistance to penicillins and cephalosporins ((3-lactam antibiotics) is due to the formation of (3-lactamase enzymes by Staphylococcus aureus or enteric Gram-negative rods. Some (3-lactamases can be firmly bound by compounds such as clavulanic acid (combined with amoxycillin or ticar-cillin) and sulbactam (combined with ampicillin) and can thus be prevented from attacking hydrolysable penicillins. Gram-positive bacteria, apart from staphylococci, generally lack the ability to acquire R plasmids. 

Erythromycin is active against gram-positive and certain gram-negative bacteria, also against Rickettsia and spirochaetes. It is used for patients who are allergic to or do not respond to treatment with penicillins or tetracyclines. 

The mechanism of antibacterial activity is through inhibition of gram-positive bacterial cell-wall synthesis thus, the penicillins are most effective against actively multiplying organisms. Because mammalian cells do not have a definitive cell-wall stmcture as do bacteria, the mammalian toxicity of the penicillins is low. Allergic phenomena in patients following sensitization may occur. 

Penicillin Penicillium chrysogenum Gram-positive bacteria Wall synthesis... 

These antibiotics are effective in die treatment of infections caused by a wide range of gram-negative and gram-positive microorganisms. The tetracyclines are used in infections caused by Rickettsiae (Rocky Mountain spotted fever, typhus fever, and tick fevers). Tetracyclines are also used in situations in which penicillin is contraindicated, in the treatment of intestinal amebiasis, and in some skin and soft tissue infections. Oral... 

The lincosamides, another group of anti-infectives, are effective against many gram-positive organisms, such as streptococci and staphylococci. However, because of their high potential for toxicity, the lincosamides are usually used only for the treatment of serious infections in which penicillin or erythromycin (a macrolide) is not effective... 

Kanamycin (a complex of three antibiotics. A, B and C) is active in low concentrations against various Gram-positive (including penicillin-resistant staphylococci) and Gram-negative bacteria. It is a recognized second-line dmg in the treatment of tuberculosis. 

A 75-year-old male develops a cough that produces blood-tinged sputum. He has a fever of 104°F Gram-positive cocci in clusters are found in a sputum smear. A chest x-ray shows increased density in the right upper lobe. Of the following penicillins, which is most likely to be ineffective ... 

The answer is b. (Hardman, pp 1077—1086.) Piperacillin is a broad-spectrum, semisynthetic penicillin for parenteral use. Its spectrum of activity includes various Gram-positive and Gram-negative organisms including Pseudomonas. The indications for piperacillin are similar to those for car-benicillin, ticarcillin, and mezlocillin, with the primary use being sus-... 

The answer is b. (Hardman, p 1077.) Unlike the other listed drugs, oxacillin is resistant to penicillinase. The other four agents are broad-spectrum penicillins, while oxacillin is generally specific for Gram-positive microorganisms Use of penicillinase-resistant penicillins should be resewed for infections caused by penicillinase-producing staphylococci... 

The answer is a. (Hardman, pp 1084-1085J Amoxicillin is classified as an aminopenicillin along with ampicillin. Because it is less affected than ampicillin by the presence of food, it has a superior absorption in the GI tract. It is sensitive to penicillinase and has a narrow spectrum of activity toward certain Gram-positive and Gram-negative organisms, but not Pseudomonas. Because it is in the penicillin family, hypersensitivity reactions are a possibility... 

The emergence of multidrug-resistant Gram-positive bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), penicillin-resistant Streptococcus pneumoniae (PRSP), and vancomycin-resistant enterococci... 

The introduction of techniques for mutagenesis by UV irradiation or by the use of chemicals considerably extended the applications of microbial studies to nutrition (Davis, 1954-1955). Auxotrophic mutants were produced with nutrient dependencies not shown in the untreated parental strains (Beadle and Tatum, 1940). The fortuitous discovery of penicillin by Fleming and its successful use in the treatment of infections (Florey) promoted exhaustive research into its mode of action. Eventually it was established that penicillin prevented the proliferation of gram-positive bacteria by blocking the synthesis of their cell walls... 

First Activity against Gram-positive bacteria similar to that of penicillins Cefalothin... 

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