Bactericidal antibiotic concentrations

Though the rationale of antimicrobial approaches to treatment is evident, their limitations have also been evident. With systemic therapy, it may be difficult to achieve bacteriostatic or bactericidal antibiotic concentrations in pockets without using doses that evoke systemic side effects. The development of bacterial resistance is also an issue. The rise of antibiotic resistant, disease-producing bacterial strains is currently a... 

P-lactam antibiotics, exert thek antibacterial effect by interfering with the synthesis of the bacterial cell wall. These antibiotics tend to be "kreversible" inhibitors of cell wall biosynthesis and they are usually bactericidal at concentrations close to thek bacteriostatic levels. Cephalospotins are widely used for treating bacterial infections. They are highly effective antibiotics and have low toxicity. 

Bactericidal antibiotic tissue concentrations should be maintained throughout the surgical procedure. 

The aminoglycosides include streptomycin, gentamicin, tobramycin, netilmicin, kanamycin, amikacin, sisomicin, neomycin, paromomycin and others. Those are bactericidal antibiotics. This bactericidal activity is concentration dependent in contrast to the... 

Early clinical trials showed no benefit from antibiotic prophylaxis, but studies were flawed, as they included patients with all degrees of disease severity and did not have a sufficient number of patients with severe necrotizing AP. " In addition, the studies utilized ampicillin, which does not penetrate well into pancreatic tissue." Imipenem-cilastatin, metronidazole, cefotaxime, piperacillin, mezlocillin, ofloxacin, and ciprofloxacin all achieve satisfactory bactericidal tissue concentrations, whereas aminoglycosides have poor penetration." " However, the importance of antibiotic penetration into pancreatic tissue has been debated, as it is the peripancreatic retroperitoneal necrotic fat and debris, not the pancreas itself, that becomes infected. 

Pharmacodynamic investigations in the IE animal model allow quantitation of bacterial densities within vegetations over time as a function of antibiotic concentration. These models empirically confirm many of the observed IE treatment principles. The antibiotic concentration in serum that is needed to kill bacteria within vegetations may be many times the minimal bactericidal concentration... 

In general, penicillins exert their biological effect, as do the other p-lactams, by inhibiting the synthesis of essential structural components of the bacterial cell wall. These components are absent in mammalian cells so that inhibition of the synthesis of the bacterial cell wall structure occurs with little or no effect on mammalian cell metabolism. Additionally, penicillins tend to be irreversible inhibitors of bacterial cell-wall synthesis and are generally bactericidal at concentrations close to their bacteriostatic levels. Consequendy penicillins have become widely used for the treatment of bacterial infections and are regarded as one of the safest and most efficacious classes of antibiotics. 

Bacteriostatic antibiotics inhibit bacterial growth and proliferation, while bactericidal antibiotics actually kill bacteria. Many antibiotics are bacteriostatic at low concentrations and bactericidal at higher concentrations. This distinction is often not important clinically. If bacteria are prevented from multiplying, they will eventually be destroyed by the normal immune reaction of the host. Infections in inmiunocompromized individuals (for example, those with human immunodeficiency virus (HIV) infection and those on systemic corticosteroid, anticancer or immunosuppressant therapy) have to be treated with potent bactericidal drugs. 

Antibiotic concentration, however, may not be the sole determinant of antibiotic efficacy because the host may augment antimicrobial activity by the bactericidal actions of macrophages and neutrophils. These strategies can be impaired by the certain characteristics exhibited by the chosen antibiotic. For example, an acid environment and anaerobic condition may lessen the effect of aminoglycosides. 

Vancomycin is bactericidal to most susceptible bacteria at concentrations near its minimum inhibitory concentration (MIC) and is an inhibitor of bacterial cell wall peptidoglycan synthesis, although at a site different from that of j3-lactam antibiotics (Chapter 9). 

Minimum bactericidal concentration The lowest concentration of antibiotic that will eliminate 3 logs or 99.9% of bacteria. 

Integration of both pharmacokinetic and pharmacodynamic properties of an agent is important when choosing antimicrobial therapy to ensure efficacy and prevent resistance. Antibiotics may demonstrate concentration-dependent (aminoglycosides and fluoroquinolones) or time-depen-dent (/l-1 acta ms) bactericidal effects. 

Pharmacology Macrolide antibiotics reversibly bind to the P site of the SOS ribosomal subunit of susceptible organisms and inhibit RNA-dependent protein synthesis. They may be bacteriostatic or bactericidal, depending on such factors as drug concentration. 

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