Decoding Genetic Features and Antimicrobial Susceptibility of Pseudomonas aeruginosa Strains Isolated from Bloodstream Infections

Abstract

Pseudomonas aeruginosa is a Gram-negative rod and an etiological factor of opportunistic infections. The infections of this etiology appear mostly among hospitalized patients and are relatively hard to treat due to widespread antimicrobial resistance. Many virulence factors are involved in the pathogenesis of P. aeruginosa infection, the coexistence of which have a significant impact on the course of an infection with a particular localization. The aim of this study was to assess the antimicrobial susceptibility profiles and the frequency of genes encoding selected virulence factors in clinical P. aeruginosa strains isolated from bloodstream infections (BSIs). The following genes encoding virulence factors of enzymatic activity were assessed: lasB, plC H, plC N, nan1, nan2, aprA and phzM. The frequency of the genes encoding the type III secretion system effector proteins (exoU and exoS) and the genes encoding pilin structural subunits (pilA and pilB) were also investigated. The occurrence of virulence-factor genes was assessed using polymerase chain reactions, each in a separate reaction. Seventy-one P. aeruginosa strains, isolated from blood samples of patients with confirmed bacteremia hospitalized at the University Hospital No. 1 of Dr. Antoni Jurasz in Bydgoszcz, Poland, were included in the study. All the investigated strains were susceptible to colistin, while the majority of the strains presented resistance to ticarcillin/clavulanate (71.8%), piperacillin (60.6 %), imipenem (57.7%) and piperacillin/tazobactam (52.1%). The presence of the lasB and plC H genes was noted in all the tested strains, while the plC N, nan2, aprA, phzM and nan1 genes were identified in 68 (95.8%), 66 (93.0%), 63 (88.7%), 55 (77.5%) and 34 (47.9%) isolates, respectively. In 44 (62.0%) and 41 (57.7%) strains, the presence of the exoU and exoS genes was confirmed, while the pilA and pilB genes were noted only in 14 (19.7%) and 3 (4.2%) isolates, respectively. This may be due to the diverse roles of these proteins in the development and maintenance of BSIs. Statistically significant correlations were observed between particular gene pairs’ coexistence (e.g., alkaline protease and neuraminidase 2). Altogether, twenty-seven distinctive genotypes were observed among the studied strains, indicating the vast variety of genetic compositions of P. aeruginosa strains causing BSIs.

Comparison of Virulence-Factor-Encoding Genes and Genotype Distribution amongst Clinical Pseudomonas aeruginosa Strains

“…This study identified the plC N gene in 100% of the MDR strains and in 87.8% of the MDS strains, while the gene encoding the synthesis of hemolytic phospholipase C was identified in 96.5% and 83.8% of the strains, respectively. The results are quite similar to the values obtained in our previous study on bloodstream-derived isolates, where the presence of the plC N and plC H genes was detected in 95.8% and 100% of the strains, respectively [ 22 ]. Meanwhile, Gonçalves et al [ 23 ] identified a lower prevalence of the plC N gene among carbapenem-resistant strains (88.0%) compared to the results of this work.…”

“…Our study reported the presence of the nan1 gene in 28.1% of the MDR and in 31.1% of the MDS strains. Our previous study identified the prevalence of the nan1 gene at a much higher level, occurring among 47.9% of the strains isolated from bloodstream infections, with variable levels of resistance to selected antibiotics [ 22 ]. It is noteworthy that the clinical samples in the previous study were also derived from patients at the same hospital.…”

“…It is noteworthy that the clinical samples in the previous study were also derived from patients at the same hospital. The absence of significant differences between the studies suggests a moderate dynamic of gene distribution in the local P. aeruginosa population [ 22 ]. Meanwhile, the study by Elmaraghy et al [ 32 ] reported a higher presence of the nan1 gene among MDR (46.4%) compared to MDS strains (31.6%), which stands in opposition to this study.…”

Carbapenem Resistance Related with Biofilm Formation and Pilin Genes in Clinical Pseudomonas aeruginosa Isolates

“…The genes that encode for pilin structural subunits (pil A and pil B) were also detected, the results of the molecular analysis of 25 isolates showed that the percentage of the pil B gene was (4%), and only one isolate was positive for this gene, the result is inconsistent with the result of Bogiel who showed that the lowest frequency of pil B gene was ranged (4.2_4. While the result of gene pil A was (92%), these results disagreed with the results obtained by (Bogiel et al, 2021(Bogiel et al, , 2022 who showed the frequency of pil A gene ranged from (19.7-to 15.9) %, this finding is very interesting because it suggests that the presence of this specific gene is essential for the colonization or infection of the human gastrointestinal tract, therefore, it might be a correlation between the presence of the chosen virulence genes and P. aeruginosa ability to form biofilm or colonize a specific location, but more studies are required to confirm this result (Bogiel et al, 2021), Figure (6)..…”

Determination of Antimicrobial Resistance and the Impact of Imipenem + Cilastatin Synergy with Tetracycline in Pseudomonas aeruginosa Isolates from Sepsis

“…The genes pilB and pilA encode components of the type IV pili (T4P) system in many bacteria, including P. aeruginosa. Only one strain expressed the pilB gene (5.26%), and some strains had the pilA gene (36.84%), which was expected given the low prevalence of this gene; their expression also varies with the infection type [68][69][70][71][72][73]. Both genes are required for type IV pili formation and function.…”