However, these drugs are less preferred because they also interfere with human DNA replication and transcription Rifampicin (Rifampin): Semi-synthetic compound produced from rifamycin. Drugs that inhibits the transcription of mRNA. It has been particularly effective in treating tuberculosis and leprosy. It inhibits the growth of gram-positive, gram-negative, and acid fast bacteria, can be taken orally, and is effective in low concentrations. Quinolones and Fluoroquinolones: inhibit the synthesis of DNA. Norfloxacin, ofloxacin, lomefloxacin, and ciprofloxacin (Cipro) are the most used fluoroquinolones. These compounds have a very broad spectrum and are used for systemic diseases. o Inhibition of cell wall synthesis – There are antibiotics that inhibit the synthesis of peptidoglycan in growing bacterial cells; this would weaken the cell wall eventually resulting to cell lysis Polymyxins These antibiotics are simple polypeptides that are able to disrupt the function of the cytoplasmic membrane. They are quite toxic to humans. The most used polymyxin is Polymycin B, due to its high toxicity it is used only topically as an antiseptic ointment combined with bacitracin and neomycin. – Neosporin is an example of this combination.
Polyenes: specifically change the permeability of cell membranes of fungi – it targets “ergosterol” (animal cells have cholesterol). The most common used Polyenes are amphoterecin B and nystantin. Nystantin is limited to topical used due to it high toxicity. Amphotericin B is only given intravenous to patients with systemic fungal infections. It is very toxic to kidneys (disrupt potassium gradient). It may cause cardiac arrhythmia. Imidazoles and Triazoles: Imidazoles are used topically against cutaneous fungal infections. Triazoles are taken orally for systemic infections. Host-Microorganism Interactions (Chapters 10 - 14) VOCABULARY Aerosolized / Droplets – small-particle residues of evaporated droplets containing microbes; because of their small size, they remain suspended in air for long periods of times Bacteremia – the presence of bacteria in the bloodstream Bacteriocins – proteins produced by certain bacteria that can kill other bacteria Carrier – an individual having an asymptomatic infection that can be transmitted to other susceptible individuals Commensalism – a symbolic relationship in which one party derives benefit and the other party is unaffected; many members of the indigenous microflora are commensals Communicable – a disease capable of being transmitted person to person Compromised host – a patient with acquired or congenital immunologic deficiency at increased risk for infectious disease complications Contagious – a disease easily transmitted from one person to another Endotoxin – - the liquid portion of the lipopolysaccharide found in the cell walls of Gram-negative bacteria; intracellular toxin Epidemic – a disease occurring in a higher than usual number of cases in a population during a given time interval Epidemiology