Instability of Pathogenicity Islands in Uropathogenic Escherichia coli 536

Abstract

The uropathogenic Escherichia coli strain 536 carries at least five genetic elements on its chromosome that meet all criteria characteristic of pathogenicity islands (PAIs). One main feature of these distinct DNA regions is their instability. We applied the so-called island-probing approach and individually labeled all five PAIs of E. coli 536 with the counterselectable marker sacB to evaluate the frequency of PAI-negative colonies under the influence of different environmental conditions. Furthermore, we investigated the boundaries of these PAIs. According to our experiments, PAI II 536 and PAI III 536 were the most unstable islands followed by PAI I 536 and PAI V 536 , whereas PAI IV 536 was stable. In addition, we found that deletion of PAI II 536 and PAI III 536 was induced by several environmental stimuli. Whereas excision of PAI I 536 , PAI II 536 , and PAI V 536 was based on site-specific recombination between short direct repeat sequences at their boundaries, PAI III 536 was deleted either by site-specific recombination or by homologous recombination between two IS100-specific sequences. In all cases, deletion is thought to lead to the formation of nonreplicative circular intermediates. Such extrachromosomal derivatives of PAI II 536 and PAI III 536 were detected by a specific PCR assay. Our data indicate that the genome content of uropathogenic E. coli can be modulated by deletion of PAIs.

Evaluation of pathogenicity islands in uropathogenic Escherichia coli isolated from patients with urinary catheters

“…Dobrindt et al reported that PAI III536 was more common than PAI II536 or PAI I536 in UPEC strains, including isolates from women with chronic UTIs, in contrast with our UPEC isolates from patients without catheters [11]. In other reports [20], PAI III536 and PAI II536 were reported as unstable PAIs, which could be the reason for the difference between our results and Sabate et al's findings. PAI IJ96, and PAI IIJ96 were not identified in our UPEC isolates.…”

“…Our results also showed that one UPEC isolate from patients with an implanted catheter and four UPEC isolates from patients without urinary catheters suffering from sepsis carried only PAI IV536 as a single PAI marker. The high frequency of PAI IV536 has been documented in commensal isolates, although some studies have shown that HPI participates in pathogenicity of extraintestinal pathogenic E. coli [14,20]. The high frequency of PAI IV536 shows this Table 3.…”

Environmental phosphate differentially affects virulence phenotypes of uropathogenicEscherichia coliisolates causative of prostatitis

“…These results may be explained by the fact that, although associated to higher potential to form biofilm, 4,45 haemolysin is a trait involved in invasiveness and could be secreted in the planktonic lifestyle in order to injure host tissue and then colonize it by forming the biofilm. Unexpectedly, even when fimB was found in the genetic pool of the 3 isolates, fimA gene was not detected as the other virulence factors; this may be due to the loss of genes or pathogenicity islands in UPEC associated with different environmental conditions, according to Middendorf et al 46 Induction of siderophore related genes in BFC conditions indicate that UPEC may use a broad repertoire of systems to acquire iron in order to survive within the iron-limited urinary tract. 47 Interestingly, UPEC strains causative of asymptomatic bacteriuria, while lacking classical virulence factors such as fimbriae, express the full complement of iron acquisition systems, providing further evidence for the requirement of iron uptake during successful urinary tract colonization.…”

Viability and survival capability of quinolone-resistant uropathogenic Escherichia coli

“…It has been generally assumed that bacteria pay a physiological price -fitness deficit-for their acquisition of resistance to antibiotics [11]. Some mechanisms compensating for these costs of quinolone resistance in E. coli have been found [3,12]. Our study showed that quinolone-resistant uropathogenic strains of E. coli exhibit significantly reduced adhesive potential but relatively high resistance to serum and macrophage bactericidity.…”