Gram negative bacteria acids

High activity against gram-positive bacteria. Low activity against gram-negative bacteria. Acid-labile. Destroyed by [5 lactamase. 60% protein-bound. 

Viomycin S. fioridae S. vinaeeus S. pumceus Gram-pos. bac ia Gram-neg. bacteria Acid-fast bacteria 475... 

A 1,8-naphthyridine, nalidixic acid (39), shows clinically useful antibacterial activity against Gram-negative bacteria as such, the drug is used in the treatment of infections of the urinary tract. Condensation of ethoxymethylenemalonate with 2-amino-6-methylpyridine (36) proceeds directly to the naphthyri-dine (38) the first step in this transformation probably involves an addition-elimination reaction to afford the intermediate, 37. W-Ethylation with ethyl iodide and base followed by saponification then affords nalidixic acid (39). 

A number of amide- and ester-linked fatty acids and (/ )-3-hydroxy acids are components of the lipid A part in the LPS from Gram-negative bacteria. The acids have been tabulatedand the chemistry of lipid A summarized. The most common acids in lipid A from Enterobacteriaceae are the saturated 12 0,14 0, and 16 0, and the (/ )-3-hydroxy-14 0, The last is linked to N-2 and 0-3 of the 2-amino-2-deoxy-D-glucopyranosyl residues, and the others are ester-linked to the hydroxy acid, as in the lipid A (44) of Salmonella minnesota. Other linear and branched fatty acids, unsaturated acids, S)-2- and (/ )-3-hydroxy acids, and 3-oxotetradecanoic acid are components of lipid A from certain different species. In the lipid A from Rhizobium trifolii, 2,7-dihydroxyoctanoic acid is linked as amide to a 2-amino-2-deoxy-D-gl ucopy ranosy 1 residue. ... 

Penicillanic acid sulphone (Tig. 5.6D) protects ampicillin flom hydrolysis by staphylococcal Alactamase and some, but not all, of the Mactamases produced by Gram-negative bacteria, but is less potent than clavulanic acid. /3-bromopenicillanic acid (Tig. 5.6E) inhibits some types of Alactamases. 

Gram-negative bacteria are intrinsically resistant to low levels of fusidic acid (a steroid) due to exclusion by the outer membrane. Nevertheless, acquired resistance does occur which has the effect of increasing the level of resistance to the antibiotic. Acquired resistance also occurs in Gram-positive bacteria normally susceptible to fusidic acid. 

Members of the genus Proteus are unusually resistant to high concentrations of ehlorhexidine and other cationic biocides and are more resistant to EDTA than most other types of Gram-negative bacteria. A less acidic type of LPS may be responsible... 

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