Gram-negative organisms

Gram-negative organisms produce ced-bound P-lactamases which reside in the periplasmic space. Thus, for gram-negative bacteria, the antibiotic must penetrate the outer ced membrane/wad before coming in contact with a P-lactamase (80,139,140). 

Gram-negative organisms sc " Low High" Low High" Low High" Low Hig h"... 

Some polymyxins are sold for second-line systemic therapy. Polymyxin B sulfate and colistimethate sodium can be used for intravenous, intramuscular, or intrathecal administration, especially for Pseudomonas aerupinosa mP QXiosis, but also for most other gram-negative organisms, such as those resistant to first-line antibiotics. Nephrotoxicity and various neurotoxicities are common in parenteral, but not in topical, use. Resistance to polymyxins develops slowly, involves mutation and, at least in some bacteria, adaptation, a poorly understood type of resistance that is rapidly lost on transfer to a medium free of polymyxin. Resistance can involve changes in the proteins, the lipopolysaccharides, and lipids of the outer membrane of the cell (52). Polymyxin and colistin show complete cross-resistance. 

Susceptible Gram-negative organisms such as some Escherichia coli and Proteus mirabilis. 

Phenylethanol (phenylethy 1 alcohol 2-phenylethanol). Typical in-use concentration 0.25-0.5%. It is reported to have greater activity against Gram-negative organisms and is usually employed in conjunction with another agent. 

A nnmber of factors may therefore be involved in the tolerance of bacteria to aromatic hydrocarbons, althongh greatest attention has hitherto been centered on Gram-negative organisms. 

Other gram-negative organisms, such as Pseudomonas spp., have been noted to cause IE, especially in IVDUs and patients with prosthetic valves. Additionally, IE caused by Salmonella spp., Escherichia coli, Citrobacter spp., Klebsiella spp., Enterobacter spp., Serratia marcescens, Proteus spp. and Providencia spp. also has been reported.1... 

Intra-abdominal operations necessitate broad-spectrum coverage of gram-negative organisms and anaerobes. Anti-anaerobic cephalosporins, cefoxitin and cefotetan, are useful but suffer from limited availability. Fluoroquinolones or aminoglycosides, paired with clindamycin or metronidazole, should provide adequate coverage for intra-abdominal operations. 

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