Abstract
Pseudomonas aeruginosa is an opportunistic pathogen causing different types of infections, particularly in intensive care unit patients. Characteristics that favor its persistence artificial environments are related to its high adaptability, wide arsenal of virulence factors and resistance to several antimicrobial classes. Among the several virulence determinants, T3SS stands as the most important due to the clinical impact of exoS and exoU genes in patient's outcome. The molecular characterization of P. aeruginosa isolates helps in the comprehension of transmission dynamics and enhance knowledge of virulence and resistance roles in infection process. In the present study, we investigated virulence and resistance properties and the genetic background of P. aeruginosa isolated from ICUs patients at a referral hospital in Brazilian Amazon. A total of 54 P. aeruginosa isolates were characterized by detecting 19 virulence-related genes, antimicrobial susceptibility testing, molecular detection of β-lactamase-encoding genes and genotyping by MLST and rep-PCR. Our findings showed high prevalence of virulence-related markers, where 53.7% of the isolates presented at least 17 genes among the 19 investigated (P = 0.01). The rare exoS+/exoU+ cytotoxic virulotype was detected in 55.6% of isolates. Antimicrobial susceptibility testing revealed percentages of antibiotic resistance above 50% to carbapenems, cephalosporins and fluoroquinolones associated to MDR/XDR isolates. Isolates harboring both blaSPM-1 and blaOXA genes were also detected. Genotyping methods demonstrated a wide genetic diversity of strains spread among the different intensive care units, circulation of international MDR/XDR high-risk clones (ST111, ST235, ST244 and ST277) and emergence of seven novel MLST lineages. Finally, our findings highlight the circulation of strains with high virulence potential and resistance to antimicrobials and may be useful on comprehension of pathogenicity process, treatment guidance and establishment of strategies to control the spread of epidemic P. aeruginosa strains.
Highlights
Pseudomonas aeruginosa is an opportunistic pathogen, causing a wide spectrum of infections, including acute and chronic respiratory tract infections (RTIs) and bloodstream infections (BSIs) as the main infection sites [1,2,3,4]
This study evaluated 54 P. aeruginosa isolates distributed in the adult intensive care units (ICUs) (AICU, 28/54– 51.8%), followed by pediatric ICU (PICU, 14/54–26.0%) and neonatal ICU (NICU, 12/54– 22.2%)
Definition of virulotypes was based on the detection of T3SS exoS/exoU genes, where it was observed the presence of invasive/cytotoxic and invasive virulotypes. exoS+/exoU+ virulotype and phzH gene were detected with significantly lower frequency at NICU (P = 0.0461 and p = 0.0491, respectively), and among isolates from BSI (P = 0.0027 and P = 0.0244, respectively), as well as exoY gene (P = 0.0435) (Tables 1 and 2)
Summary
Pseudomonas aeruginosa is an opportunistic pathogen, causing a wide spectrum of infections, including acute and chronic respiratory tract infections (RTIs) and bloodstream infections (BSIs) as the main infection sites [1,2,3,4]. Pathogenicity in P. aeruginosa is multifactorial, relying on the regulation of virulencerelated genes and expression of their respective factors, including adhesins, exotoxins, proteases and pigments. Only four effector exotoxins encoded by the exoS, exoU, exoT and exoY genes have been identified, which are variably present and expressed by P. aeruginosa strains. ExoS and ExoU are associated to invasive and cytotoxic phenotypes, respectively, and rarely concomitant detected, while ExoT and ExoY demonstrate few cytotoxic effects and are encoded by most of strains [8, 14,15,16,17]. Survey of cytotoxic/exoU+ virulotype has been highly recommended due to the impact of this exotoxin in patient’s mortality, especially in isolates from high risk settings, such as ICUs [18, 19]
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