Evaluation of two novel biofilm-specific antibiotic resistance genes in clinical Pseudomonas aeruginosa isolates

Effects of Four Antibiotics on Pseudomonas aeruginosa Motility, Biofilm Formation, and Biofilm-Specific Antibiotic Resistance Genes Expression

The aim of this study was to determine the effects of 4 antibiotics (tobramycin, fosfomycin, ciprofloxacin, and piperacillin/tazobactam) against Pseudomonas aeruginosa motility, biofilm formation, and biofilm resistance gene expression changes using different methods including microscopy, microdilution, crystal violet staining, and qRT-PCR. Although the antibiotics reduced swarming motility, they inhibited biofilm formation to a greater extent than the minimum inhibitory concentration (MIC) value. The qRT-PCR results showed that the antibiotics, other than fosfomycin, decreased the expression levels of the selected biofilm resistance genes (ndvB, tssC1, PA5033 and PA2070) in the biofilm structure compared to planktonic cells. Furthermore, it was found that there was an increase in the expression levels of biofilm resistance genes in the antibiotic application groups compared to the biofilm structure that was not treated with antibiotics. These results showed for the first time that the treatment of antibiotics at sub-MIC concentrations increases the expression levels of biofilm-specific resistance genes and contributes to resistance and motility.

Antisense peptide nucleic acids againstftsZ andefaA genes inhibit growth and biofilm formation of Enterococcusfaecalis

Enterococcus faecalis is one of the important causes of nosocomial infections. Nowadays, increasing prevalence of antibiotic-resistant bacteria and slow progress in recognizing new antimicrobial agents has limited the efficiency of conventional antibiotics, which cause to find novel strategies to overcome bacteria. Therefore, in this study, we aimed to assess the role of efaA gene in the biofilm formation and the role of ftsZ gene in the controlling of bacterial growth by the anti-sense PNAs(Peptide Nucleic Acid).E. faecalis ATCC® 29212™was used for the study of PNAs designed to targeting the start codon section of the ftsZ andefaA genes. PNA attachment to RNA was confirmed by blotting. Electroporation technique was used for the intracellular transfer of anti-ftsZ PNAs. The spot-plating method was used to the assessment of alteration in bacterial growth. Biofilm formation assay and real-time PCR were used for detection of biofilm inhibitory effect of cell penetrating peptide (CPP) conjugated to anti-efaA PNAs.ByftsZ PNAs treatment, no growth was seen from the strain in agar by a spot plating method and the inhibition zone of anti-ftsZ PNAs was not seen. PNAs against the efaA gene decreased by 95% the expression of the efaA gene and biofilm formation. In addition, the(3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide) MTT assay showed no toxicity on MCF7 cells for both of anti-ftsZand anti-efaA PNAs.This study used new genetic and molecular tools to inhibit pathogenicity and infection by E. faecalis. In this study, we suggested that efaA gene plays a critical role in the biofilm formation and anti-efaA PNAs could decrease the formation of biofilm, as well as, anti-ftsZ PNAs could eliminate bacterial growth.

Peptide nucleic acid-mediated re-sensitization of colistin resistance Escherichia coli KP81 harboring mcr-1 plasmid

Escherichia coli is a gram-negative bacterium and it causes a variety of diseases in humans. It causes a wide range of clinical infections in humans; urinary tract infections is the most prevalent infection caused by uropathogenic Escherichia coli. In recent years, the observation of antibiotic-resistant genes such as resistance to colistin, makes the Escherichia coli resistant to antibiotics like colistin (polymyxin E), because of that the use of new therapies like peptide nucleic acid (PNA) has attracted the consideration of scientists. The aim of this study is the assessment of the inhibitory role of PNA against mcr-1 gene and reduction of mcr-1 gene expression and MIC in colistin resistant E. coli by PNA. NCBI database was used to design PNA. Our study was carried out on E. coli KP81 bacteria containing the mcr-1 gene. Microbroth dilution (MIC) method was used to survey phenotypic sensitivity and determine the sensitivity of the bacteria to the colistin antibiotic. E. coli KP81 isolates were further investigated by polymerase chain reaction to assess the presence of mcr-1 genes and target genes were quantified by real-time PCR assay using specific primers. The MIC result after treatment with specific PNA showed that the resistance to colistin reduced about three fold and the resistance level dropped from 32 μg/ml to 4 μg/ml. The expression analysis of mcr-1 gene in E. coli KP81 isolate indicates the PNA, 95% reduced the expression of the mcr-1 gene. Our observations showed that by inhibiting the expression of mcr-1, sensitivity to colistin can be defeated. Using higher concentrations of PNA and an in vivo study can reveal more clinical application of this method.