Production Of Various Virulence Factors Research Articles

Effect of low concentrations of quinolone antibiotics on bacterial virulence mechanisms

Recent studies have shown that exposure to quinolone antibiotics at or below the minimal inhibitory concentration (MIC) results in reduction in the level of production or total elimination of certain factors that contribute to the virulence of bacteria. This study was designed to determine whether low concentrations of enoxacin, lomefloxacin, and ciprofloxacin altered the morphology or affected the production of various virulence factors in several different genera of bacteria. The factors studied were nuclease and α toxin production in Staphylococcus aureus, cell size, pili and fimbriae production, and adherence of Salmonella typhimurium, Escherichia coli, and Pseudomonas aeruginosa to urinary epithelial cells and dog bladder cells, and the major virulence factor in Yersinia pseudotuberculosis. In addition, the effect of growth in low levels of enoxacin on phagocytosis of S. aureus by human polymorphonuclear leukocytes (PMNs) was studied. Following exposure to subinhibitory levels of quinolones tested, significant reduction in activity or complete elimination was seen in all of those factors measured. Minor differences were noted in the efficiency of elimination among the three quinolones tested. At as low as 1 8 MIC there is significant enhancement of phagocytic activity by human PMNs. These data suggest that exposure to quinolones at concentrations below the MIC disrupts the regulatory mechanisms that control cell morphology, adherence as well as exocellular enzyme production and plasmid maintenance. This may mean that certain virulent organisms that survive exposure to quinolone antibiotics may be less likely to produce or maintain the disease state in susceptible hosts.

The contribution of diffusible toxins of Pseudomonas aeruginosa to the pathogenesis of experimental pyelonephritis

Summary Five strains of Pseudomonas aeruginosa differing in their production of various virulence factors were examined for their ability to cause pyelonephritis when injected intravenously into mice. The severity of infection produced was found to correlate with the degree of production in vitro of the protein exotoxin A, except in a strain which also simultaneously produced a protease. A strain which produced both haemolysin and exotoxin A caused a more persistent infection than one which produced more exotoxin A but no haemolysin. These findings support the current view that exotoxin A is the most clearly identifiable virulence factor of Ps. aeruginosa , but suggest that the final outcome of infection may depend on an interplay with other factors produced by individual strains.