Antimicrobial agents fluoroquinolone

C. jejuni is susceptible to a wide variety of antimicrobial agents. Fluoroquinolone resistance has increased to 10% to 13%... 

A fluorine atom in position 6 of the basic structure of quinolones enhances the antimicrobial activity considerably. All widely used quinolones are fluorinated in position 6 and the term fluoroquinolones is often used to describe these drugs. However, some new quinolones with similar antimicrobial activity are not fluorinated in position 6 (e.g. garenoxacin, PGE9262932) and therefore the term quinolones is more appropriate to describe this group of antimicrobial agents. 

Absorption of antimicrobial agents such as fluoroquinolones and tetracyclines that can be bound by divalent and trivalent cations potentially could be compromised by administration with EN formulas containing these cations. The fluoroquinolones (e.g., levofloxacin and ciprofloxacin) have been best studied in this regard, and results of studies are not consistent. Mechanisms for an interaction between fluoroquinolones and EN formulas other than chelation by cations have been postulated.40 Some institutions hold tube feedings for 30 to 60 minutes or more before and after enteral dosages of fluoroquinolones. Because ciprofloxacin absorption has been shown to be decreased with jejunal administration, this drug probably should not be given by jejunal tube.41... 

Antimicrobial agents as well as macrolide antibiotics and fluoroquinolones used in human and veterinary medicine are of particular interest due to their potential for... 

Animal and human studies support the use of antibiotics for the prevention of infectious morbidity and mortality in severe ANP. The most effective antimicrobial agents are the fluoroquinolones, imipenem-cilastatin, and metronidazole, which achieve adequate penetration into pancreatic juice and necrotic tissue and inhibit the growth of enteric bacteria. Although a recent meta-analysis [185] suggested that prophylactic antibiotic administration reduces sepsis and mortality and this approach has been recommended by recent guidelines and consensus state-... 

The majority of patients can be managed with oral antimicrobial agents, such as trimethoprim-sulfamethoxazole or the fluoroquinolones (ciprofloxacin, levofloxacin). When IV treatment is necessary, IV to oral sequential therapy with trimethoprim-sulfamethoxazole or a fluoroquinolone, such as ciprofloxacin or ofloxacin, would be appropriate. 

Olsen, K.M., Gentry-Nielsen, M., Yue, M., Snitily, M.U. and Preheim, L.C. (2006) Effect of ethanol on fluoroquinolone efficacy in a rat model of pneumococcal pneumonia. Antimicrobial Agents and Chemotherapy, 50, 210-219. 

Zhang, J.Z. and K.W. Ward (2008) Besi-floxacin, a novel fluoroquinolone antimicrobial agent, exhibits potent inhibition of pro-inflammatory cytokines in human THP-1 monocytes. J Antimicrob Chemother. 61, 111-6. 

Certain antimicrobial agents used to treat urinary tract infections act better in acidic pH i.e. nitrofurantoin, tetracycline, methenamine, cloxacillin. Certain other antimicrobial agents such as gentamicin, cephalosporins, fluoroquinolones, cotri-... 

Nitrofurantoin is bacteriostatic and bactericidal for many gram-positive and gram-negative bacteria but P aeruginosa and many strains of proteus are resistant. There is no cross-resistance between nitrofurantoin and other antimicrobial agents and resistance emerges slowly. As Escherichia coli resistant to trimethoprim-sulfamethoxazole and fluoroquinolones has become more common, nitrofurantoin has become an important alternative oral agent for treatment of uncomplicated urinary tract infection. 

Treatment of microbial keratitis is started immediately irrespective of whether microbiologic evaluation has been performed. The best antimicrobial agent or agents to use initially is debated in the ophthalmic literature. The two main choices for initial antibiotic treatment are the combination of two fortified antibiotics, such as cefazolin and tobramycin, or monotherapy with topical fluoroquinolones. Just as with the decision to culture, the choice of antibiotic is often influenced by history and clinical presentation. Milder presentations, in low-risk... 

The maximum plasma concentration reflects the extent of drug bioavailability. It can be used in relation to minimum inhibitory concentration (MIC) to predict the efficacy of concentration-dependent antimicrobial agents (e.g. fluoroquinolones, aminoglycosides). Both the maximum (peak) and minimum (trough) plasma concentrations are used during therapeutic drug monitoring to maximize efficacy and minimize the occurrence of undesirable effects. 

Payne et al. [13] used 19F MR to measure the hepatic concentration of sitafloxacin, a fluoroquinolone antimicrobial agent. Elevated liver enzymes have been reported after use of sitafloxacin, even though it is eliminated predominantly by renal excretion (>99%). This evaluation was to determine whether drug accumulation in the liver occurs. Sitafloxacin has two nonequivalent fluorines (m-oriented (I /(, 2. S ) - 2 -1 hio roc y c I o pro p y I a m i ne moiety) with resonances separated by 92 ppm. The experiments were focused only on one... 

Antimicrobial agents most likely to be affected by the first-pass effect include trimethoprim, sulphonamides, fluoroquinolones, chloramphenicol, metronidazole and rifampin. The metabolites of trimethoprim, sulphonamides, most fluoroquinolones and chloramphenicol are inactive, while ciprofloxacin and sarafloxacin formed by N-dealkylation of enrofloxacin and difloxacin, respectively, and desacetylrifampin have antimicrobial activity similar to or greater than (ciprofloxacin) the parent drug. Certain antimicrobial agents (chloramphenicol and erythromycin) inhibit hepatic microsomal enzyme activity, whereas rifampin is a potent inducer of hepatic microsomal enzymes. 

The chemical nature and related physicochemical properties largely govern the distribution and elimination, which refers to biotransformation (metabolism) and excretion, of antimicrobial agents. The majority of antimicrobial agents are weak organic electrolytes, either weak acids (penicillins, cephalosporins, sulphonamides) or weak bases (aminoglycosides, lincosamides, macrolides, diaminopyrimidines, metronidazole), while fluoroquinolones, tetracyclines and rifampin are amphoteric compounds, and chloramphenicol and its... 

Table 6.8 Suggested guideline for the interpretation of MIC (pg/mL) of various antimicrobial agents based on bacterial isolates of equine origin, apart from fluoroquinolones which relate to isolates of canine origin.

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