Characterization of antibiotic and disinfectant susceptibility profiles amongPseudomonas aeruginosaveterinary isolates recovered during 1994-2003

Abstract

This is the first report of Ps. aeruginosa susceptibility to 24 disinfectants and illustrates the high resistance of Ps. aeruginosa to both antibiotics and disinfectants.

Interactions of Organic Acids with Salmonella Strains from Feedlot Water-Sprinkled Cattle

“…After comparing the study here of Salmonella strains to the previous three studies, E. coli O157:H7 [34], the non-O157 STECs [37] and P. aeruginosa [35], we observed a trend beginning to develop. The MIC M s of 100% of the Salmonella strains with acetic acid was at pH 4.9, 98.6% of non-O157 STECs with acetic acid was at pH 4.79 [37] and the MIC M s of 99% of the P. aeruginosa strains with acetic acid was at pH 4.9 [35]. Since E. coli O157:H7 has glutamateand arginine-dependent acid-resistance systems to protect it from extreme acid stress [42], we see more acid-tolerance in E. coli O157:H7.…”

“…If pH were the primary factor in inhibition of the bacteria, then one would expect the MICs for these same bacteria for all the different acids would be at the same pH value, but that is not the case. The Salmonella strains demonstrated similar behavior against the organic acids as did E. coli O157:H7 [34], non-O157 STECs [37] and P. aeruginosa [35], except the pH values for the E. coli O157:H7 strains were somewhat lower, possibly because O157:H7 strains are known to have multiple acid-resistance systems to protect them from extreme acid stress [42]. After comparing the study here of Salmonella strains to the previous three studies, E. coli O157:H7 [34], the non-O157 STECs [37] and P. aeruginosa [35], we observed a trend beginning to develop.…”

“…The Salmonella strains demonstrated similar behavior against the organic acids as did E. coli O157:H7 [34], non-O157 STECs [37] and P. aeruginosa [35], except the pH values for the E. coli O157:H7 strains were somewhat lower, possibly because O157:H7 strains are known to have multiple acid-resistance systems to protect them from extreme acid stress [42]. After comparing the study here of Salmonella strains to the previous three studies, E. coli O157:H7 [34], the non-O157 STECs [37] and P. aeruginosa [35], we observed a trend beginning to develop. The MIC M s of 100% of the Salmonella strains with acetic acid was at pH 4.9, 98.6% of non-O157 STECs with acetic acid was at pH 4.79 [37] and the MIC M s of 99% of the P. aeruginosa strains with acetic acid was at pH 4.9 [35].…”

“…But the specific mechanisms by which pH and organic acids inhibit bacteria are not completely understood [33]. We have previously evaluated Escherichia coli O157:H7 strains from cattle carcasses, feces and hides and ground beef [34], Pseudomonas aeruginosa veterinary isolates [35], and the organic acid inhibition was clearly associated with the dissociated acid species. The disintegration of the LPS layer can be caused by a fully dissociable acid [36].…”

“…MICs were determined as the lowest concentration of a compound that showed no visible growth of the organism [40]. The organic acid susceptibility studies were carried out similarly to earlier studies with other pathogens [34,35,37]. Briefly, 50 µL of each organic acid solution was diluted 1:2 across a 96-well U-bottom Greiner bio-one microplate ((#82050-626, VWR, Houston, TX, USA) through column 11, and column 12 was the positive control.…”