High frequency of the exoU+/exoS+ genotype associated with multidrug-resistant “high-risk clones” of Pseudomonas aeruginosa clinical isolates from Peruvian hospitals

Abstract

The type III secretion system of Pseudomonas aeruginosa is an important virulence factor contributing to the cytotoxicity and the invasion process of this microorganism. The current study aimed to determine the presence of the exoU +/ exoS + genotype in P . aeruginosa clinical isolates. The presence of exoS , exoT , exoU and exoY was determined in 189 P . aeruginosa by PCR, and the presence/absence of exoU was analysed according to source infection, clonal relationships, biofilm formation, motility and antimicrobial susceptibility. The gyrA , parC , oprD , efflux pump regulators and β-lactamases genes were also analysed by PCR/sequencing. The exoS , exoT and exoY genes were found in 100% of the isolates. Meanwhile, exoU was present in 43/189 (22.8%) of the isolates, being significantly associated with multidrug resistance, extensively drug resistance as well as with higher level quinolone resistance. However, the presence of β-lactamases, mutations in gyrA and parC , and relevant modifications in efflux pumps and OprD were not significantly associated with exoU + isolates. MLST analysis of a subset of 25 isolates showed 8 different STs displaying the exoU +/ exoS + genotype. The MDR basis of the exoU + isolates remain to be elucidated. Furthermore, the clinical implications and spread of exoU +/ exoS + P . aeruginosa isolates need to be established.

Characterization of Ocular Clinical Isolates of Pseudomonas aeruginosa from Non-Contact Lens Related Keratitis Patients from South India

“…Interestingly, out the thirty-four isolates screened in this study, seven were resistant to fluoroquinolones and 85% were exoU+. In a recent study by Horna et al, out of 189 P. aeruginosa isolates obtained from patients in the intensive care unit, majority of the multi-drug and extensively-drug resistant strains were exoU positive [58]. In agreement with this, we found that out of the seven strains which were multi-drug resistant, five were exoU positive.…”

High prevalence of atypical virulotype and genetically diverse background among Pseudomonas aeruginosa isolates from a referral hospital in the Brazilian Amazon

“…exoS results are in accordance with the hypothesis of a wider distribution of this gene due to its chromosomal nature. Nevertheless, the fact of in nearly 30% of our isolates exoT and exoY genes were not detected and a significant absence of exoY gene among BSI isolates demonstrate a contrary trend to the hypothesis of their universal distribution among P. aeruginosa strains, as well as, several studies that rarely report absence of these genes (P = 0.0435) ( Table 2) [13,15,16,55,56,70].…”

“…It is likely that inter-hospital transit patients and/or who spend short periods in the hospital environment, as well as healthcare professionals, carry isolates and insert them in the hospital environment, and consequently causing infections in ICU patients because of numerous risk factors, such as immunosuppression conditions and virulence potential of isolates. Our data also corroborate the hypothesis of epidemic non-clonal population structure of P. aeruginosa, indicating the dispersion of global HRC in hospitals settings and the continuous description of new P. aeruginosa STs worldwide [15,23,55,56,76,85,86].…”

“…In fact, the acquisition of resistance genes through the incorporation of mobile genetic elements in the bacterial chromosome can lead to the inactivation of genes involved in the production of some virulence factors and decreased cytotoxicity [23,72,74,83]. Nevertheless, other authors suggest that exoU + virulotype is associated to resistance to fluoroquinolones and carbapenems, pointing out that the relationship between virulence and resistance may also occur in a synergistic sense, especially in high antibiotic pressure settings, such as ICUs [9,13,15,16,84]. In spite of that, our data do not suggest this association, as the presence of T3SS virulotypes was not related to any antimicrobial class or resistance phenotype (Table 4).…”

“…So far, 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]. Furthermore, 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].…”