Role of P-fimbrial-mediated adherence in pyelonephritis and persistence of uropathogenic Escherichia coli (UPEC) in the mammalian kidney

P fimbria, a mannose-resistant adhesin of uropathogenic Escherichia coli (UPEC), has been shown to be associated with acute pyelonephritis. The pap gene cluster encodes the proteins required for P-fimbrial biogenesis, including papG, which encodes the tip adhesin. The three most studied PapG molecular variants, which are shown to bind distinct isoreceptors, are PapGI, -II, and -III. PapGII preferentially binds globoside, or GbO4, a glycolipid isoreceptor of the human kidney. Studies using different animal models of ascending urinary tract infection (UTI) have demonstrated a variable role for P fimbriae, and specifically PapGII-mediated adherence, in renal colonization. The disparities in the results obtained from those studies are likely to be attributed to the differences in animal models and UPEC strains utilized. One explanation that is discussed in detail is the contribution of multiple fimbriae of UPEC that potentially mediate adherence to the mammalian kidney. Overall, P fimbriae appear to play some role in mediating adherence to uroepithelial cells in vivo and establishing an inflammatory response during renal colonization, thus contributing to kidney damage during acute pyelonephritis. To verify that P fimbriae contribute to the pathogenesis of UPEC during ascending UTI (and in particular acute pyelonephritis), future studies should be conducted to satisfy fully all three tenets of the molecular Koch's postulates, including complementation of a mutated allele.     

Biofilm formation in uropathogenic Escherichia coli strains: relationship with prostatitis, urovirulence factors and antimicrobial resistance

PURPOSE: Escherichia coli strains are the most frequent cause of urinary tract infections. Biofilm formation allows the strains to persist a long time in the genitourinary tract and interfere with bacterial eradication. We determined the possible relationships between the different urinary tract infections, and in vitro biofilm formation, the presence of urovirulence factors and nalidixic acid resistance. MATERIALS AND METHODS: A total of 151 E. coli strains collected from patients with cystitis (44 strains), pyelonephritis (75) and prostatitis (32) were analyzed for in vitro biofilm formation, the phylogenetic group, the presence of several urovirulence factors and resistance to nalidixic acid. RESULTS: E. coli strains causing prostatitis produced biofilm in vitro more frequently than those causing other urinary tract infections and had a higher frequency of hemolysin (p = 0.03 and 0.0002, respectively). However, only hemolysin was independently associated with prostatitis. On the other hand, strains forming biofilm presented a significantly higher frequency of hemolysin and type 1 fimbriae expression. CONCLUSIONS: Although hemolysin is the main virulence factor by which E. coli causes acute prostatitis, the association between hemolysin and biofilm formation may result in increased ability of E. coli strains to persist in the prostate.     

Characterization of Escherichia coli strains causing urinary tract infections in patients with transposed intestinal segments

PURPOSE: Transposition of intestinal segments into the urinary tract predisposes to urinary tract infections. We characterized bacterial infections in these patients and examined the virulence genotype and persistence of Escherichia coli isolates. MATERIALS AND METHODS: We followed 26 patients who underwent bladder reconstructive surgery using transposed intestinal segments. E. coli strains isolated from the urine of these patients were genotyped for established virulence determinants and the frequency of carriage was compared with E. coli strains isolated from community acquired urinary infections and the fecal flora of anonymous volunteers. A longitudinal study of E. coli strains in 9 patients was also done using pulsed field gel electrophoresis. RESULTS: E. coli was the most frequently isolated organism, responsible for 59% (62 of 105) of monobacterial infections. Other bacteria isolated included Klebsiella species, Proteus species and Enterococcus faecalis. Community acquired E. coli strains were more likely to carry multiple determinants for particular adhesins (P and S fimbriae) and toxins (alpha-hemolysin and cytotoxic necrotizing factor) than fecal strains. Carriage frequency for bladder reconstruction strains was intermediary and not significantly different. The key finding was that E. coli strains persisted for prolonged periods, including 2 years in certain patients, often despite various antimicrobial treatments. CONCLUSIONS: This study highlights that further steps must be taken to prevent and treat urinary tract infections in this susceptible group. Particular attention should be given to the treatment of persistent infections.     

In vitro and in vivo adherence of uropathogenic Escherichia coli strains

Twenty-eight Escherichia coli strains isolated from the urine of patients with urinary tract infections were assayed for fimbrial type, in vitro capacity to agglutinate guinea pig red blood cells, and in vivo adherence to rat bladder uroepithelium. A direct correlation was found between hemagglutinating capacity and in vivo adherence. Strains with both Type 1 and P fimbriae showed the greatest adherence in vivo. Of the 28 strains, seven did not manifest either Type 1 or P fimbriae but agglutinated red blood cells and did adhere in vivo. In studies on bacterial adherence and urinary tract infections, both in vivo and in vitro studies may contribute to understanding the relevance of bacterial adhesins in initiating urinary tract infections.     

Renal Allograft Injury Is Associated with Urinary Tract Infection Caused by Escherichia coli Bearing Adherence Factors

Urinary tract infections are the most common infection in renal transplant patients and Escherichia coli (E. coli) is the most common clinical isolate. Although acute allograft injury (AAI) secondary to urinary tract infection (UTI) has been reported, the incidence of AAI associated with UTI, the virulence factors express by uropathic E. coli and whether virulence factors are associated with renal allograft outcome have not been described. We collected E. coli from our renal transplant patients with UTI, determined O:H serotypes, P and Dr fimbriae expression and the clinical presentation and allograft function during the UTI and post-UTI period. Pyelonephritis occurred in 40% of our patients, 82% of which had AAI (>20% increase in SCr). Sixty-two percent of E. coli isolates that expressed P fimbriae were associated with AAI, whereas only 29% that did not express P fimbriae had AAI (p = 0.03). The pattern of P fimbriae and O serotypes differed from reported isolates, as the P fimbriae PapG class II and the O25 serotype were the most common. Dr adhesin was expressed on 7 isolates, including 2 of 3 with urosepsis. We propose a unique pattern of uropathogenic serotypes and adherence factors contribute to acute allograft injury in renal transplant patients with UTI.     

Etiology and pathophysiology of pyelonephritis.

Escherichia coli is the most frequent cause of pyelonephritis. Its possible virulence factors include the ability to adhere and colonize the urinary tract, an important initiating factor in all urinary tract infections (UTIs). The importance of P fimbriae in this adhesion is stressed and the evidence for its importance in pyelonephritis is presented in epidemiologic studies of patients, as well as in animal studies. It appears that both host receptor density and the nonsecretor state is responsible for susceptibility to urinary tract infection. Vesicoureteral reflux can be responsible for ascending upper tract infection, but infection with P-fimbriated E coli may lead to ascending pyelonephritis without reflux because of the paralytic effect of lipid A on ureteral peristaltic activity. Renal ischemia leads to renal damage following infection by reperfusion damage due to the release of superoxide. Experimentally, this ischemic damage can be prevented by allopurinol, a xanthine oxidase inhibitor. The acute inflammatory response can produce renal damage because of the respiratory burst of phagocytosis, which while killing phagocytosed bacteria also damages renal tubules. An amelioration of the inflammatory response by treatment with superoxide dismutase or corticosteroids has been shown to modulate renal damage. Vaccination with P fimbriae has been shown experimentally to prevent the initiation of the disease. However, since vaccines are not clinically available, the clinical and animal studies on therapy of acute disease are stressed. Acute pyelonephritis during the first 3 years of life more often produced the renal damage that could lead to end-stage renal disease.(ABSTRACT TRUNCATED AT 250 WORDS)     

Selective use of excretory urography in women with acute pyelonephritis

The outcome of excretory urography was analyzed in 103 nonpregnant women followed prospectively after community acquired acute pyelonephritis. Radiological abnormality was found in 40 per cent of the patients (17 per cent had major abnormalities, including renal scarring, calculi and obstruction). All 5 women with surgically correctable lesions had rapid bacteriological relapse or recurrent acute pyelonephritis. Neither a history of urinary tract infection, the acute inflammatory response nor infection due to Escherichia coli with or without adhesins specific for Gal alpha 1----4Gal beta-containing receptors was efficient in predicting major radiographic lesions or the outcome of treatment. Bacteremia was detected in 27 per cent of the patients but in the absence of obstruction. These results suggest that excretory urography is dispensable in most women with acute pyelonephritis, and that those needing such investigation may be identified by failure to respond to antibiotic treatment or by the recurrence pattern.     

The presence of the virulence island containing the usp gene in uropathogenic Escherichia coli is associated with urinary tract infection in an experimental mouse model

PURPOSE: A putative virulence island commonly noted in the genome of uropathogenic Escherichia coli strains has recently been reported. We have observed that the island includes a gene consisting of a protein designated uropathogenic specific protein (usp) and 3 small open reading frames (orfU1-3). In our current study we assessed the importance of the genes located in the putative virulence island in the pathogenesis of urinary tract infection using a mouse pyelonephritis model. MATERIALS AND METHODS: A total of 427 E. coli strains isolated from the urine of 194, 76 and 107 subjects suffering from cystitis, pyelonephritis and prostatitis, respectively, and 50 isolates from the feces of healthy individuals were examined for genotypes and serotypes. In addition, several recombinant E. coli strains possessing usp and/or orfU1 to 3 were constructed for evaluating the significance of these genes using an experimental pyelonephritis mouse model. RESULTS: The usp was significantly more often associated with uropathogenic E. coli strains (79.4% from cystitis, 93.4% from pyelonephritis and 88.8% from prostatitis) than with fecal E. coli strains from healthy individuals (24%). Furthermore, usp was frequently associated with all common serotypes of uropathogenic E. coli (71.7% to 100%). In challenge experiments using the mouse urinary tract infection model the vector possessing usp significantly enhanced the infectibility of the E. coli host cell, whereas the 3 small proteins at the downstream of usp failed to show the effect. CONCLUSION: Our results indicate that usp may contribute to the causation of urinary tract infection and may be considered a major virulence determinant of uropathogenic E. coli.     

Virulence of wild-type E. coli uroisolates in experimental pyelonephritis

This study was designed to analyze the colonizing and invasive properties of wild-type bacteriuric E. coli possessing a variety of phenotypic characteristics in experimental nonobstructive pyelonephritis (P and Type 1 [T] fimbriae, hemolysin [Hly], presence of K capsules, flagella [H], serotype, biotype, human and mouse serumcidal resistance). Special emphasis was on the role of Gal-Gal adhesin (P fimbriae) of non-genetically engineered uroisolates. It was shown that organisms that are P+ or T+ or Hly+ are more likely to colonize bladders than strains negative for those parameters (P less than 0.001). Additionally, P+ strains were more often associated with kidney histopathology than P- E. coli (P less than 0.05). However, the data also indicated that fimbriae (P and Type 1) were not sole determinants of virulence since two strains devoid of fimbriae, hemolysin, K capsules and sensitive to human serumcidal activity caused incipient and acute pyelonephritis. Even among identical serotypes and biotypes, the presence/absence of fimbriae did not appear to be the critical factor in urovirulence, nor did the presence of several positive characteristics (hemolysin, K capsule, flagella, serum resistance) in a given strain enhance uropathogenicity. Therefore, these properties do not need to work together to render an E. coli urovirulent. These phenotypic characters may simply represent associated or serologic markers with the host serving as the dominant determinant of susceptibility to urinary infection. The findings emphasize the inherent limitations in relating and extrapolating colonizing and invasive properties of genetically engineered strains to those of naturally occurring, wild-type E. coli human uroisolates causing pyelonephritis.     

Pyelonephritic Escherichia coli expressing P fimbriae decrease immune response of the mouse kidney

P fimbriae are proteinaceous appendages on the surface of Escherichia coli bacteria that mediate adherence to uroepithelial cells. E. coli that express P fimbriae account for the majority of ascending urinary tract infections in women with normal urinary tracts. The hypothesis that P fimbriae on uropathic E. coli attach to renal epithelia and may regulate the immune response to establish infection was investigated. The polymeric Ig receptor (pIgR), produced by renal epithelia, transports IgA into the urinary space. Kidney pIgR and urine IgA levels were analyzed in a mouse model of ascending pyelonephritis, using E. coli with (P+) and without (P-) P fimbriae, to determine whether P(+) E. coli regulate epithelial pIgR expression and IgA transport into the urine. (P+) E. coli establish infection and persist to a greater amount than P(-) E. coli. P(+)-infected mice downregulate pIgR mRNA and protein levels compared with P(-)-infected or PBS controls at > or =48 h. The decrease in pIgR was associated with decreased urinary IgA levels in the P(+)-infected group at 48 h. pIgR mRNA and protein also decline in P(+) E. coli-infected LPS-hyporesponsive mice. These studies identify a novel virulence mechanism of E. coli that express P fimbriae. It is proposed that P fimbriae decrease pIgR expression in the kidney and consequently decrease IgA transport into the urinary space. This may explain, in part, how E. coli that bear P fimbriae exploit the immune system of human hosts to establish ascending pyelonephritis.     

Escherichia coli Virulence Factors and Serotypes in Acute Bacterial Prostatitis

Background Escherichia coli is the most frequent pathogen in both acute bacterial prostatitis and acute uncomplicated urinary infections. To assess the virulence profiles of E. coli in acute prostatitis, the serotypes and virulence factor (VF) genotypes were determined.
Methods We studied 107 E. coli isolates from cases of acute bacterial prostatitis, 76 isolates from acute pyelonephritis, 194 isolates from acute cystitis and 80 fecal isolates from healthy people. All pyelonephritis and cystitis isolates were from women. Seven urovirulence determinants were analyzed by DNA colony hybridization, including the genes for type 1 fimbria (pil) , P fimbria (pap) , S fimbria (sfa) , afimbrial adhesin AFA-I (afal), α -hemolysin (hly) , cytotoxic necrotizing factor 1 (cnfl) and aerobactin (aer). 0:H:K serotypes were also determined.
Results With the exception of pil and afal , all VFs were significantly more often associated with prostatitis, pyelonephritis and cystitis isolates than with the fecal isolates. The prevalence of sfa, hly and cnfl was higher in prostatitis isolates than in pyelonephritis and cystitis isolates, and the pap⁺sfa⁺hly⁺cnf⁺ genotype was dominant among prostatitis isolates (48.8%). Nine O serotypes(01, 02, 04, 06, 01 6, Ol 8, 022, 025 and 075) accounted for 79.4%, 73.7% and 78.4% of the prostatitis, pyelonephritis and cystitis strains, respectively. There was an apparent correlation between serotype and genotype in uropathogenic E. coli.
Conclusion The predominance of O serotypes in female urinary tract infections and a high percentage of multiple VFs among the prostatitis isolates suggested that VFs play important roles in the pathogenesis of acute bacterial prostatitis.     

Fimbrial lectins influence the chemokine repertoire in the urinary tract mucosa

The defense against mucosal infections relies on chemokines that recruit inflammatory cells to the mucosa. This study examined if the chemokine response to uro-pathogenic Escherichia coli is influenced by fimbrial expression. The CXC (CXCL1, CXCL5, CXCL8, CXCL9, CXCL10) and CC chemokines (CCL2, CCL3, CCL5) were quantified after in vitro infection of uro-epithelial cells with a fimbriated E. coli pyelonephritis isolate, or with P or type 1 fimbriated transformants of an avirulent E. coli K-12 strain. The response profile was shown to vary with the fimbrial type. Type 1 fimbriated E. coli elicited mainly CXCL1 and CXCL8, whereas P fimbriated E. coli stimulated CCL2 and CCL5 and class II were more potent chemokine inducers than class III P fimbriae. Chemokines were also quantified in urine samples from 73 patients with febrile urinary tract infection, and analyzed as a function of disease severity and fimbrial expression by the strain infecting each patient. A complex CXC and CC chemokine response was detected in patient urine, with a significant influence of the fimbrial type. The results show that virulence factors like fimbriae may modify the mucosal chemokine response. This mechanism may allow the host to adjust the inflammatory cell infiltrate to fit the infecting strain.     

VIRULENCE CHARACTERISTICS AND DNA FINGERPRINTS OF ESCHERICHIA COLI ISOLATED FROM WOMEN WITH ACUTE UNCOMPLICATED PYELONEPHRITIS

Purpose

Previous studies indicated that acute pyelonephritis in infants is initiated by the dominance of uropathogenic strains in fecal flora. Such pathogenic evidence, however, is still lacking for adult women. In this study, the validity of a fecal-perineal-urethral hypothesis in acute uncomplicated pyelonephritis of adult women was assessed at a genetic level.

Materials and Methods

A total of 1,200 Escherichia coli isolates from the urine and rectal swab of 12 adult women with acute uncomplicated pyelonephritis were examined. The clonality of the urinary and fecal isolates was evaluated by genotyping of 6 urovirulence determinants and pulsed-field gel electrophoresis. Furthermore, urovirulence genotypes were examined in E. coli isolates from the rectal swab of 30 normal healthy women (mean 26.7 isolates per person).

Results

The E. coli strains causing pyelonephritis were present in the rectal swab in 10 of 12 patients and were a predominant fecal clone in 9 cases. Also, P-fimbriated strains dominated in the fecal flora in 10 of 30 normal healthy women.

Conclusions

The clonal identity of the urinary and fecal strains in acute pyelonephritis clearly supports the fecal-perineal-urethral hypothesis.     

Adhesiveness to urinary tract epithelial cells of fecal and urinary Escherichia coli isolates from patients with symptomatic urinary tract infections or asymptomatic bacteriuria of varying duration.

Adhesiveness to human urinary tract epithelial cells was high for Escherichia coli strains isolated from patients with acute pyelonephritis and acute cystitis, and low for asymptomatic bacteriuria strains detected at screening. Escherichia coli bacteria causing asymptomatic reinfections, detected near the onset of bacteriuria, adhered more than those detected at screening. No difference in the adhesive ability was found between fecal isolates of the strain causing urinary tract infection, isolated at or before onset of bacteriuria, and the urinary strain in symptomatic or asymptomatic patients. Normal fecal Escherichia coli from non-bacteriuric patients adhered less than all other strains tested.     

Urinary Escherichia coli causing recurrent infections--a prospective follow-up of biochemical phenotypes.

Twenty-three women with non-obstructive acute pyelonephritis due to Escherichia coli were prospectively studied during 880 patient months, mean observation time 38 months. Each patient had between 1 and 4 new episodes of E. coli bacteriuria during the study period (altogether 49 recurrencies). All E. coli isolates were typed by biochemical fingerprinting. Twenty-six of the recurrencies were caused by an E. coli strain identical to one of those that had previously appeared. Sixteen of these infections were caused by a strain identical to the one that gave rise to the original acute pyelonephritis. Ten further recurrencies were due to an E. coli strain that had previously caused symptomatic or asymptomatic bacteriuria during the observation period. Despite appropriate treatment and repeated negative urine cultures post-treatment, infections caused by identical E. coli strains occurred up to 35 months after the initial episode of acute pyelonephritis. We suggest that the infecting E. coli strain may survive in the fecal flora or is harboured in the patient's surroundings, and after recolonizing the patient, these strains may give rise to further urinary tract infections.     

Tamm-Horsfall protein knockout mice are more prone to urinary tract infection: rapid communication

BACKGROUND: Human colon contains many bacteria that commonly colonize the perineum and frequently enter the urinary tract. Uropathogenic Escherichia coli are the most common cause of urinary tract infection. Type 1 fimbriated E. coli have been associated with cystitis, and P fimbriated E. coli with pyelonephritis. Factors involved in clearing bacteria from the urinary tract are poorly understood. Tamm-Horsfall protein (THP), the most abundant protein in mammalian urine, has been postulated to play a role in defense against urinary tract infection but definitive proof for this idea has been lacking. METHODS: In this study, we generated THP gene knockout mice by the technique of homologous recombination, and examined if the THP-deficient (THP-/-) mice were more prone to urinary tract infection. Various strains of E. coli expressing type 1 or P fimbriae were introduced transurethrally into the bladders of the THP-/- and genetically similar wild-type (THP+/+) mice. Urine, bladder, and kidney tissues were obtained from the mice and cultured for bacterial growth. RESULTS: THP-/- mice inoculated with type 1 fimbriated E. coli had a longer duration of bacteriuria, and more intense colonization of the urinary bladder in comparison with THP+/+ mice. When inoculated with a P fimbriated strain of E. coli, the THP-/- mice showed no difference in kidney bacterial load when compared with the THP+/+ mice. CONCLUSION: These findings support the idea that THP serves as a soluble receptor for type 1 fimbriated E. coli and helps eliminate bacteria from the urinary tract.     

尿路结构异常儿童合并泌尿系感染的病原菌分析

目的探讨尿路结构异常儿童合并泌尿系感染（UTI）致病菌的分布及药物敏感及耐药情况。 方法收集2012年1月至2016年12月中山大学附属第三医院及汕头市中心医院符合UTI住院患儿476例,分为尿路正常组及尿路异常组,比较两组间病原菌构成比及对抗菌药物的敏感和耐药情况。 结果尿路异常者162例（肾积水最为常见,占43.83%）,尿路正常儿童314例。尿路异常儿童合并感染常见于男性（P<0.05）,共检出致病菌166株,革兰氏阴性菌（G^-）为主（71.08%）,大肠埃希菌占首位（40.36%）,肠球菌属居第2位（22.89%）,粪肠球菌在尿路异常组常见（χ²=4.59,P=0.032）。两组间常见病原菌耐药性差异无统计学意义。 结论尿路结构异常男性儿童易发生泌尿系感染,且肠球菌感染的发生率高于尿路结构正常儿童。     

Frequency and distribution of uropathogenic Escherichia coli adhesins: a clinical correlation over 2,000 cases.

In order to determine the pathogenic responsibility of Escherichia coli adhesins (ADHs) in urinary infections (UI), 2,000 different patients suffering different clinical urinary and male sexual gland infections were monitored. The ADHs were determined by agglutination techniques with human and guinea-pig red blood cells, Candida albicans and Saccharomyces cerevisiae cells and latex sensitized with GAL-GAL. In uncomplicated UIs, the possession of ADH is the main invasion mechanism for E. coli. The rate of E. coli ADH strains is very high (89%) in acute cases (727 of 818 cases: 310 of 362 cystitis; 104 of 113 recidivant cystitis; 120 of 126 pyelonephritis; 158 of 173 prostatitis, and 34 of 43 orchiepididymitis) and rare (10%) in asymptomatic or chronic cases (24 of 235 cases: 14 of 148 bacteriurias; 8 of 74 prostatitis, and 2 of 13 orchiepididymitis). A close relation is established between the presence of ADH and clinical symptoms. 90% (218 of 242) of acute cases with systemic symptoms are due to MR-type ADH strains, especially the P subtype. 71% (409 of 576) of acute cases with local symptoms are due to MS-type ADH strains. In complicated UIs the expression of ADH is not an essential condition for the invasion of the urinary apparatus. It has been strongly suggested that males are significantly more resistant to UI, both in the tract and parenchyma, than women. It can be deduced that the underlying disease is more liable to UI the lower the adherence level shown by isolated strains. Thus catheters, reflux and neurogenic bladder are, by far, more aggressive alterations than the prostatic adenoma, vesical tumor or lithiasis.     

The role of fimbriae of Escherichia coli in urinary tract infections]

The incidence of P-fimbriated E. coli from patients with pyelonephritis, cystitis and asymptomatic bacteriuria was 78.6%, 31.9% and 22.2%, respectively. Almost all of the P-fimbriated E. coli have also type-1 fimbriae. In the in vitro test, P-fimbriated E. coli attached to the uroepithelial cells in higher number than the type 1 fimbriated E. coli. The results of the adhesion inhibition test suggested that simultaneous presence of P-and type 1 fimbriae is the most significant virulence factor in urinary tract infections.     

Subtyping of uropathogenic Escherichia coli according to the pathogenicity island encoding uropathogenic-specific protein: Comparison with phylogenetic groups

BACKGROUND: Phylogenetic analysis has been used widely to characterize extraintestinal pathogenic Escherichia coli in molecular epidemiological studies. We have recently reported a putative pathogenicity island (PAI), carrying uropathogenic-specific protein (usp) and a unique mosaic structure of small open reading frames following usp, providing four subtypes of PAIusp classified from their sequential patterns. METHODS: A total of 427 E. coli isolates from uncomplicated urinary tract infections (194 cystitis, 76 pyelonephritis, and 107 prostatitis) and 50 fecal isolates were examined for phylogenetic grouping and PAIusp subtyping as well as the prevalence of virulence factors (VF) and O serogroups. RESULTS: Both phylogenetic group B2 and usp-positive strains were equally predominant in cystitis, pyelonephritis and prostatitis (B2, 80.9%, 86.8%, and 86.9%; usp, 79.4%, 93.4%, and 88.8%, respectively). Furthermore, each PAIusp subtype was shown to be closely associated with several VF genes as well as several common O serogroups of uropathogenic E. coli. CONCLUSIONS: In molecular epidemiological studies, PAIusp subtyping will provide additional informative findings of E. coli strains belonging to phylogenetic group B2.