Antimicrobial death

FIGURE 2.19 Antimicrobial death kinetics curve. ( ) Actual collected data points (—) predicted data points (regression analysis) that should be confirmed by the... 

Nonoxidizing Antimicrobials. Nonoxidizing antimicrobials usually control growths by one of two mechanisms. In one, microbes are inhibited or killed as a result of damage to the ceU membrane. In the other, microbial death results from damage to the biochemical machinery involved in energy production or energy utilization. 

Considerable work has been done to try to explain why quats are antimicrobial. The following sequence of steps is beheved to occur in the attack by the quat on the microbial cell (/) adsorption of the compound on the bacterial cell surface (2) diffusion through the cell wall (J) binding to the cytoplasmic membrane (4) dismption of the cytoplasmic membrane (5) release of cations and other cytoplasmic cell constituents (6) precipitation of cell contents and death of the cell. 

Figure 1.1. Opposite) Sulpha drugs and their mode of action. The first sulpha drug to be used medically was the red dye prontosil rubrum (a). In the early 1930s, experiments illustrated that the administration of this dye to mice infected with haemolytic streptococci prevented the death of the mice. This drug, while effective in vivo, was devoid of in vitro antibacterial activity. It was first used clinically in 1935 under the name Streptozon. It was subsequently shown that prontosil rubrum was enzymatically reduced by the liver, forming sulphanilamide, the actual active antimicrobial agent (b). Sulphanilamide induces its effect by acting as an anti-metabolite with respect to /iflra-aminobenzoic acid (PABA) (c). PABA is an essential component of tetrahydrofolic acid (THF) (d). THF serves as an essential co-factor for several cellular enzymes. Sulphanilamide (at sufficiently high concentrations) inhibits manufacture of THF by competing with PABA. This effectively inhibits essential THF-dependent enzyme reactions within the cell. Unlike humans, who can derive folates from their diets, most bacteria must synthesize it de novo, as they cannot absorb it intact from their surroundings...

The antimicrobial activity of eugenol may be associated with structural damage and alteration of the permeability mechanism of microsome, lysosome, and cell walls. The substance acts primarily on cytoplasm membranes, causing alteration of its permeability, and thus allowing leakage of essential bacterial cell constituents with subsequent death of the bacteria. 

Vitamin K is an essential cofactor for the synthesis of prothrombin and other blood-clotting factors. Vitamin K deficiency occurs due to liver disease, longterm antimicrobial therapy, and malabsorption. Vitamin K deficiency can lead to hemorrhages in newborns and development of hypoprothrombobinemia. Rapid intravenous injection of emulsified vitamin K produces flushing, breathlessness, hypotension, and may lead to death. 

The essential oil of cumin exhibits strong antimicrobial activity against Escherichia coli, Staphylococcus aureus and Listeria monocytogenes. Complete death time on exposure to cumin oil was 20, 180 and 90 min for E. coli, S. aureus and L. monocytogenes, respectively (Gachkar et al., 2007). 

The antimicrobial properties of silver and its salts have been discussed in various books [14, 16-18] and particular reference must be made to Grier s review in 1983 [15]. Ag usually used in the form of silver nitrate, is bacteriostatic or bactericidal [19-29], antifungal [30-32], protozoicidal [33] and lethal to herpes simplex virus [34]. However, bacterial spores [19], cysts of Entamoeba histolytica [19] and mycobacteria [35] are not killed by Ag. Brown and Anderson [20] observed a non-linear order of death in Pseudomonas aeruginosa exposed to Ag, whereas Ricketts et al. [22] reported a rapid bactericidal action of Ag in water, but not in broth, at concentrations of silver nitrate of 0.5 and 1 pg/ml (2.9 x 10 and 5.8 x 10 M, respectively) with inactivation at concentrations above 1 p.g/ml being too fast for measurement. 

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