Abstract
Susceptibility of the tested Pseudomonas aeruginosa strain to two different antibiotics, tetracycline (TE) and ciprofloxacin (CIP), was carried out using liquid dilution method. Minimum inhibitory concentrations of TE and CIP were 9.0 and 6.0 mg/100 mL, respectively. Some metabolic changes due to both, the mode of action of TE and CIP on P. aeruginosa and its resistance to high concentrations of antibiotics (sub-MIC) were detected. The total cellular protein contents decreased after antibiotic treatment, while outer membrane protein (OMP) contents were approximately constant for both treated and untreated cells. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the OMPs for untreated and TE and CIP treated cells indicated that the molecular changes were achieved as; lost in, induction and stability of some protein bands as a result of antibiotics treatment. Five bands (with mol. wt. 71.75, 54.8, 31.72, 28.63, and 20.33 KDa) were stable in both treated and untreated tested strains, while two bands (with mol. wt. 194.8 and 118.3 KDa) were induced and the lost of only one band (with mol. wt. 142.5 KDa) after antibiotics treatment. On the other hand, total lipids and phospholipids increased in antibiotic treated cells, while neutral lipids decreased. Also, there was observable stability in the number of fatty acids in untreated and treated cells (11 fatty acids). The unsaturation index was decreased to 56% and 17.6% in both TE and CIP treatments, respectively. The produced amount of EPSs in untreated cultures of P. aeruginosa was relatively higher than in treated cultures with sub-MICs of TE and CIP antibiotics. It was also observed that the amounts of exopolysaccharides (EPSs) increased by increasing the incubation period up to five days of incubation in case of untreated and antibiotic treated cultures.
Highlights
Bacterial cells grow and divide, replicating repeatedly to reach the large numbers present during an infection or on the surface of the body
The reduction of total cellular protein contents might be referred to the mode of action of antibiotic on bacterial cell, where tetracycline inhibited the binding of aminoacyl-tRNA into the A site of the bacterial 30S ribosome and inhibited protein synthesis [1]
The quantity of EPSs produced by P. aeruginosa cells treated with TE was higher than cells treated with CIP at all incubation periods
Summary
Bacterial cells grow and divide, replicating repeatedly to reach the large numbers present during an infection or on the surface of the body. There were four major sites in bacterial cell that they serve as the basis for the action of antibiotics: the cell wall, ribosome, nucleic acids, and cell membrane [2]. This classification did not mean that antibiotics inhibited only the mentioned vital process of the bacterial cell; each particular antibiotic was classified by the mechanism of its concentration, chemical nature, or other microbial conditions [3]. The basic mechanisms by which microorganisms can resist antibiotics were (1) to alter the receptor for the drug (the molecule on which it exerted its effect) as fluoroquinolones, (2) to decrease the amount of drug that reached the receptor by altering entering or increasing removal of the drug as tetracyclines, (3) to destroy or inactivate the drug, (4) to develop resistant metabolic pathways, [1] and (5) to exclude from the cell by the outer membrane of Gram-negative bacteria [4]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
