Prevalence of pathogenicity island IICFT073 genes among extraintestinal clinical isolates of Escherichia coli

Uropathogenic Escherichia coli is the most common cause of urinary tract infection (UTI). Cystitis in women is by far the most common UTI; pyelonephritis in both sexes and prostatitis in men are more severe but are less frequent complaints. The ability of E. coli to cause UTI is associated with specific virulence determinants, some of which are encoded on pathogenicity islands (PAI). One such PAI (PAI IICFT073), of the prototypical uropathogenic E. coli strain CFT073, contains 116 open reading frames, including iron-regulated genes, carbohydrate biosynthetic genes, the serine protease autotransporter picU, a two-partner secretion system, a type I secretion system, mobility genes, and a large number of hypothetical genes. To determine the association of PAI IICFT073 with UTI, PCR was used to examine the prevalence of the five virulence-associated loci among the ECOR collection and a collection of E. coli isolated from patients with cystitis, pyelonephritis, prostatitis, or septicemia. All PAI IICFT073 loci were found to be more prevalent among the B2 phylogenetic group than any other group within the ECOR collection and among invasive prostatitis strains than were cystitis or pyelonephritis strains. These data support the theory that clinical isolates causing prostatitis are more virulent than those producing cystitis or pyelonephritis in women.     

Bacterial characteristics in relation to clinical source of Escherichia coli isolates from women with acute cystitis or pyelonephritis and uninfected women

Characteristics differentiating Escherichia coli strains that cause cystitis or pyelonephritis from fecal E. coli remain incompletely defined, particularly among adult women in the United States. Accordingly, phylogenetic group, O antigens, and virulence factors (VFs) were analyzed among 329 E. coli isolates from the mid-to-late 1990s from women in the United States with acute pyelonephritis (n = 170), cystitis (n = 83), or no infection (fecal; n = 76). Compared with fecal and cystitis isolates, pyelonephritis isolates exhibited a greater prevalence of phylogenetic group B2, most virulence-associated O antigens, and most VFs and had higher VF scores. In contrast, cystitis and fecal isolates differed minimally. By stepwise multivariable logistic regression, significant (P < or = 0.015) predictors of cystitis and/or pyelonephritis (versus fecal) included afa/dra (Dr-binding adhesins), ibeA (invasion of brain endothelium), iha (putative adhesin-siderophore), malX (pathogenicity island marker), the O75 antigen, papEF (P fimbriae), papG allele II (P adhesin variant), group B2, and sfa/foc (S and F1C fimbriae). However, virulence profiles overlapped considerably among source groups and varied greatly within each group. E. coli "clonal group A" (CGA) and the O2:K5/K7:H1 and O75:K+ clonal groups were significantly associated with cystitis and/or pyelonephritis. These findings identify potential vaccine targets, suggest that urovirulence is multiply determined, and confirm the urovirulence of specific E. coli clonal groups, including recently recognized CGA.     

Virulence factors profile of drug-resistant Escherichia coli isolates from urinary tract infections in Punjab, Pakistan

Escherichia coli is considered to be the main causative agent of urinary tract infections (UTIs). The primary objective of this study was to investigate the spectrum of five virulence factors among drug-resistant clinical E. coli isolates associated with pyelonephritis and cystitis. A total of 101 samples were positive for E. coli (42 from pyelonephritis cases and 59 from cystitis cases) out of 457 urine samples of patients. Among toxins, haemolysin and secreted autotransporter toxin are found more frequently in isolates causing pyelonephritis (p < 0.020) than cystitis (p < 0.083). The frequent occurrence of P-pili, S-fimbria and protein involved in intestinal colonisation was noted among E. coli isolates associated with pyelonephritis. Overall, the study suggests that clinical isolates associated with pyelonephritis are more virulent than those associated with cystitis and diversified association with various antimicrobial resistance phenotypes was noted.     

Molecular epidemiology of adhesin and hemolysin virulence factors among uropathogenic Escherichia coli

The pap, prs, pil, and hly operons of the pyelonephritic Escherichia coli isolate J96 code for the expression of P, F, and type 1 adhesins and the production of hemolysin, respectively; the afaI operon of the pyelonephritic E. coli KS52 encodes an X adhesin. Using different segments of these operons as probes, colony hybridizations were performed on 97 E. coli urinary tract and 40 fecal clinical isolates to determine (i) the presence in the infecting bacteria of nucleotide sequences related to virulence operons, and (ii) the phenotypic properties associated with such sequences. Coexpression of P and F adhesins encoded by pap-related sequences was detected more frequently among isolates from patients with pyelonephritis (32 of 49, 65%) than among those with cystitis (11 of 48, 23%; P less than 0.0001) or from fecal specimens (6 of 40, 15%; P less than 0.0001). Therefore, the expression of both adhesins appears to be critical in the colonization of the upper urinary tract. In contrast, afaI-related sequences were detected significantly more frequently among isolates from patients with cystitis, suggesting that this class of X adhesin may have a role in lower urinary tract infections. Urinary tract isolates differed from fecal isolates by a low incidence of type 1 adhesin expression among pil probe-positive isolates. hly-related sequences were only detected in pap probe-positive isolates. The frequency of hemolysin production among pap probe-positive isolates was not associated with a particular pattern of infection. The distribution of these virulence factors was similar in the presence or absence of reflux, indicating that structural abnormalities of the urinary tract did not facilitate colonization by adhesin-negative isolates.     

Expression of type 1 fimbriae may be required for persistence of Escherichia coli in the catheterized urinary tract.

Long-term urinary catheterization results in polymicrobial bacteriuria and is complicated by fever, bacteremia, acute pyelonephritis, and death. Escherichia coli is a common urine isolate from catheterized patients and can persist for months. We hypothesized that fimbria-mediated adherence contributes to its persistence. For 1 year, urine specimens were collected from 51 patients greater than or equal to 65 years of age who were catheterized for greater than or equal to 30 days. E. coli was isolated at greater than or equal to 10(5) CFU/ml from 447 (36%) of 1,230 weekly urine specimens from 26 patients. Week 1 isolates from 52 definable episodes were tested for hemagglutination, hybridization with gene sequences from the pil and pap operons, in vitro adherence to catheter material, binding of 125I-labeled Tamm-Horsfall protein, hemolysin and colicin V production, and serum resistance. The proportions of isolates of short (1 week only), medium (2 to 11 weeks) and long (greater than or equal to 12 weeks) episodes of bacteriuria which expressed type 1 fimbriae as assayed by mannose-sensitive hemagglutination were 59, 65, and 92%, respectively. Isolates with the pil operon (the genome for type 1 fimbriae) from episodes lasting greater than 1 week expressed mannose-sensitive hemagglutination more frequently (P = 0.011) than pil-positive isolates from episodes of less than or equal to 1 week. Isolates from episodes of greater than 1 week also bound significantly more Tamm-Horsfall protein than isolates from episodes of less than or equal to 1 week (P = 0.044). Although nearly half of the isolates produced P fimbriae, an important virulence factor for the development of pyelonephritis, no correlation with persistence could be made. Overall, the E. coli isolates expressed traits similar to those of strains that caused cystitis. Type 1 fimbriae appear to be important for the persistence of E. coli in the long-term-catheterized urinary tract.     

The IrgA homologue adhesin Iha is an Escherichia coli virulence factor in murine urinary tract infection

The role of the Escherichia coli iron-regulated gene homologue adhesin (Iha) in the pathogenesis of urinary tract infections (UTIs) is unknown. We performed a series of complementary analyses to confirm or refute the hypothesis that Iha is a virulence factor in uropathogenic E. coli. Fecal E. coli isolates exhibited significantly lower prevalences of iha (range, 14 to 22%) than did clinical isolates from cases of pediatric cystitis or pyelonephritis, adult pyelonephritis or urosepsis, or bacteremia (range, 38 to 74%). Recombinant Iha from E. coli pyelonephritis isolate CFT073 conferred upon nonadherent E. coli ORN172 the ability to adhere to cultured T-24 human uroepithelial cells. In a well-established mouse model of ascending UTI, CFT073 and its derivative UPEC76 (a pap [P fimbriae] mutant version of strain CFT073) each significantly outcompeted their respective iha deletion mutants in CBA/J mice 48 h after bladder challenge (P < 0.03 for urine, both kidneys, and bladders of both constructs, except for bladders of mice challenged with UPEC76 and its deletion mutant, where P = 0.11). These data suggest that Iha(CFT073) is a virulence factor and might be a target for anti-UTI interventions.     

Distribution of phylogenetic groups,sequence type ST131, and virulence-associated traits among Escherichia coli isolates from men with pyelonephritis or cystitis and healthy controls

Urinary tract infections (UTI), which are mostly caused by Escherichia coli, are an important public health problem worldwide. Although men experience diverse UTI syndromes, there have been relatively few molecular-epidemiological studies of UTI pathogenesis in men. We studied the distribution of 22 E. coli virulence factor (VF) genes, major phylogenetic groups, sequence type ST131, and UTI-associated O antigens among 101 pyelonephritis, 153 cystitis and 135 fecal healthy control E. coli isolates from men aged 30–70 years in a regional area of NSW, Australia. Overall, the studied traits exhibited a prevalence gradient across these groups, highest in pyelonephritis, intermediate in cystitis, and lowest among fecal isolates. Differences in virulence gene prevalence between cystitis and pyelonephritis isolates were limited to eight genes. The UTI-associated O antigens were also distributed widely, but types O6, O25 and O75 were significantly associated with pyelonephritis. The ST131 clonal group, which accounted for 13% of isolates overall (22% of group B2 isolates), likewise exhibited a significant descending prevalence gradient from pyelonephritis (36%), through cystitis (8%), to fecal (0%) isolates. These findings contribute to better understanding of the pathogenesis of UTIs in men and identify specific VF genes and O types, and a prominent clonal group (ST131), as being important in UTI pathogenesis in this population.     

Do Escherichia coli strains causing acute cystitis have a distinct virulence repertoire?

Bacterial virulence factors influence the site and severity of urinary tract infections. While pyelonephritis-associated molecular traits have been defined, virulence factors specific for acute cystitis strains have not been identified. This study examined the virulence factor repertoire of 247 Escherichia coli strains, prospectively isolated from women with community-acquired acute cystitis. Fim sequences were present in 96% of the isolates, which also expressed Type 1 fimbriae. Curli were detected in 75%, 13% of which formed cellulose. Pap sequences were present in 47%, 27% were papG+, 23% were prsG+ and 42% expressed P fimbriae. TcpC was expressed by 33% of the strains, 32% in a subgroup of patients who only had symptoms of cystitis and 42% in patients with signs of upper urinary tract involvement; most frequently by the papG+/prsG+ subgroup. Strains with the full fim, pap and TcpC and curli virulence profile were more common in cystitis patients with than in patients without upper tract involvement (p < 0.05). The varied virulence profile of E. coli strains causing acute cystitis suggests that diverse bacterial strains, expressing Type 1 fimbriae trigger a convergent host response, involving pathways that give rise to the characteristic symptoms of acute cystitis.     

Expression of P fimbriae of uropathogenic Escherichia coli strains

The occurrence of P fimbriae in a total of 222 uropathogenic Escherichia coli (UPEC) strains was investigated. Out of the total, 31 (14%) were P fimbriated. Of 24 pyelonephritogenic E. coli strains, three (13%) with P fimbriae occurred in children with clinical pyelonephritis, and of 198 E. coli strains 29 (15%) occurred in children with cystitis. Prevalence of P fimbriae of E. coli strains was found to be quite similar in patients with cystitis and pyelonephritis     

Online-Only Abstract

Urinary tract infections (UTI), which are mostly caused by Escherichia coli, are an important public health problem worldwide. Although men experience diverse UTI syndromes, there have been relatively few molecular-epidemiological studies of UTI pathogenesis in men. We studied the distribution of 22 E. coli virulence factor (VF) genes, major phylogenetic groups, sequence type ST131, and UTI-associated O antigens among 101 pyelonephritis, 153 cystitis and 135 fecal healthy control E. coli isolates from men aged 30–70 years in a regional area of NSW, Australia. Overall, the studied traits exhibited a prevalence gradient across these groups, highest in pyelonephritis, intermediate in cystitis, and lowest among fecal isolates. Differences in virulence gene prevalence between cystitis and pyelonephritis isolates were limited to eight genes. The UTI-associated O antigens were also distributed widely, but types O6, O25 and O75 were significantly associated with pyelonephritis. The ST131 clonal group, which accounted for 13% of isolates overall (22% of group B2 isolates), likewise exhibited a significant descending prevalence gradient from pyelonephritis (36%), through cystitis (8%), to fecal (0%) isolates. These findings contribute to better understanding of the pathogenesis of UTIs in men and identify specific VF genes and O types, and a prominent clonal group (ST131), as being important in UTI pathogenesis in this population.     

Escherichia coli Sequence Type 131 as a Prominent Cause of Antibiotic Resistance among Urinary Escherichia coli Isolates from Reproductive-Age Women

The recent emergence of multidrug-resistant Escherichia coli sequence type 131 (ST131) has coincided with an increase in general antibiotic resistance of E. coli, suggesting that ST131 has a contributing role in resistance. However, there is little information about the contribution of ST131 to different clinical syndromes or the basis for its impressive emergence and epidemic spread. To investigate this, we studied 953 E. coli isolates from women of reproductive age in the central west region of New South Wales, Australia, including 623 urinary isolates from patients with cystitis (cystitis isolates) (n = 322) or pyelonephritis (pyelonephritis isolates) (n = 301) and 330 fecal isolates from healthy controls. The characteristics studied included ST131 clonal group status, resistance to different antibiotics, presence of virulence factor (VF) genes, and biofilm production. As expected, fecal isolates differed significantly from urinary (cystitis and pyelonephritis) isolates in most of the studied characteristics. Antibiotic resistance was significantly more common in ST131 than in non-ST131 isolates. Both antibiotic resistance and ST131 were more common in pyelonephritis than cystitis isolates and least so among fecal isolates. Within each source group, individual VF genes were more prevalent and VF scores were higher for ST131 than for non-ST131 isolates. For ST131 only, the prevalences of most individual VF genes and VF scores were the lowest in the fecal isolates, higher in the cystitis isolates, and highest in the pyelonephritis isolates. Biofilm production was strongly associated with ST131 status and antibiotic resistance. These results clarify the distribution of the ST131 clonal group and its epidemiological associations in our region and suggest that it exhibits both enhanced virulence and increased antibiotic resistance compared with those of other urinary tract infection (UTI) and fecal E. coli isolates from women of reproductive age.     

Proteus mirabilis flagella and MR/P fimbriae: isolation, purification, N-terminal analysis, and serum antibody response following experimental urinary tract infection.

Urinary tract infection with Proteus mirabilis may lead to serious complications, including cystitis, acute pyelonephritis, fever, bacteremia, and death. In addition to the production of hemolysin and the enzyme urease, fimbriae and flagellum-mediated motility have been postulated as virulence factors for this species. We purified mannose-resistant/proteuslike (MR/P) fimbriae and flagella from strains CFT322 and HU2450, respectively. Electron microscopy revealed highly concentrated preparations of fimbriae and flagella. Fimbrial and flagellar structural subunits were estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be 18.5 and 41 kDa, respectively. N-terminal sequencing revealed that 10 of the first 20 amino acids of the major MR/P subunit matched the sequence of the P. mirabilis uroepithelial cell adhesin N terminus and 11 of 20 amino acids matched the predicted amino acid sequence of the Escherichia coli P fimbriae structural subunit, PapA. In addition, 90 and 80% homologies were found between the first 20 amino acids of P. mirabilis flagellin and those of Salmonella typhimurium phase-1 flagellin and the E. coli hag gene product, respectively. An enzyme-linked immunosorbent assay using purified antigens showed a strong reaction between the MR/P fimbriae or flagella and sera of CBA mice challenged transurethrally with P. mirabilis. A possible role for MR/P fimbriae in the pathogenesis of urinary tract infection is supported by (i) a strong immune response to the antigen in experimentally infected animals, (ii) amino acid sequence similarity to other enteric surface structure, and (iii) our previously reported observation that MR/P fimbriae are expressed preferentially as the sole fimbrial type in human pyelonephritis isolates.     

Canine feces as a reservoir of extraintestinal pathogenic Escherichia coli

To test the canine reservoir hypothesis of extraintestinal pathogenic Escherichia coli (ExPEC), 63 environmental canine fecal deposits were evaluated for the presence of ExPEC by a combination of selective culturing, extended virulence genotyping, hemagglutination testing, O serotyping, and PCR-based phylotyping. Overall, 30% of canine fecal samples (56% of those that yielded viable E. coli) contained papG-positive E. coli, usually as the predominant E. coli strain and always possessing papG allele III (which encodes variant III of the P-fimbrial adhesin molecule PapG). Multiple other virulence-associated genes typical of human ExPEC were prevalent among the canine fecal isolates. According to serotyping, virulence genotyping, and random amplified polymorphic DNA analysis, over 50% of papG-positive fecal E. coli could be directly correlated with specific human clinical isolates from patients with cystitis, pyelonephritis, bacteremia, or meningitis, including archetypal human ExPEC strains 536, CP9, and RS218. Five canine fecal isolates and (clonally related) archetypal human pyelonephritis isolate 536 were found to share a novel allele of papA (which encodes the P-fimbrial structural subunit PapA). These data confirm that ExPEC representing known virulent clones are highly prevalent in canine feces, which consequently may provide a reservoir of ExPEC for acquisition by humans.     

Analysis of Escherichia coli strains causing bacteriuria during pregnancy: selection for strains that do not express type 1 fimbriae

Escherichia coli isolates from patients with bacteriuria of pregnancy were compared by PCR with isolates from patients with community-acquired cystitis for the presence of established virulence determinants. The strains from patients with bacteriuria of pregnancy were less likely to carry genes for P-family, S-family, and F1C adhesins, cytotoxic necrotizing factor 1, and aerobactin, but virtually all of the strains carried the genes for type 1 fimbriae. Standard mannose-sensitive agglutination of yeast cells showed that only 15 of 42 bacteriuria strains (36%) expressed type 1 fimbriae compared with 32 of 42 strains from community-acquired symptomatic infections (76%) (P < 0.01). This difference was confirmed by analysis of all isolates for an allele of the type 1 fimbrial regulatory region (fim switch), which negates type 1 fimbrial expression by preventing the fim switch from being inverted to the on phase. This allele, fimS49, was found in 8 of 47 bacteriuria strains from pregnant women (17.0%) compared with 2 of 60 strains isolated from patients with cystitis (3.3%) (P < 0.05). Determination of the phase switch orientation in vivo by analysis of freshly collected infected urine from patients with bacteriuria showed that the fim switch was detectable in the off orientation in 17 of 23 urine samples analyzed (74%). These data indicate that type 1 fimbriae are not necessary to maintain the majority of E. coli bacteriurias in pregnant women since there appears to be selection against their expression in this particular group. This is in contrast to the considered role of this adhesin in community-acquired symptomatic infections. The lack of type 1 fimbria expression is likely to contribute to the asymptomatic nature of bacteriuria in pregnant women, although approximately one-third of the bacteriuria isolates do possess key virulence determinants. If left untreated, this subset of isolates pose the greatest threat to the health of the mother and unborn child.     

Serum resistance in Escherichia coli strains causing acute pyelonephritis and bacteraemia.

The capacity of Escherichia coli to resist the bactericidal action of serum was examined in 367 clinical isolates obtained from children with acute pyelonephritis (n = 57), adults with acute pyelonephritis (n = 55), non-diabetic patients with bacteraemia (n = 101), diabetic patients with bacteraemia (n = 65) and from the faecal flora of healthy controls (n = 89). The incidence of serum-resistant E. coli strains was significantly higher in pyelonephritogenic strains from children and adults (93% and 82%) as compared to faecal control strains (57%, p less than 0.001 and p less than 0.005 respectively). Strains causing bacteraemia in non-diabetic and diabetic patients were more often serum resistant (72% and 80%) as compared to control strains (p less than 0.05 and p less than 0.001 respectively). The frequency of serum-sensitive strains was similar in diabetic patients with decreased renal function or proteinuria compared to those with normal renal function. There were no significant correlations between serum resistance of E. coli and expression of P fimbriae, type I fimbriae or mannose-resistant haemagglutination, cell surface hydrophobic properties, production of aerobactin, haemolysin or cytotoxic necrotizing factor in 53 pyelonephritogenic strains from adult patients.     

Characteristics of haemolytic Escherichia coli with particular reference to production of cytotoxic necrotizing factor type 1 (CNF1).

A total of 1,106 Escherichia coli strains isolated in Spain between 1986 and 1991 from extraintestinal infections and faeces of healthy controls were examined for production of alpha-haemolysin (Hly). Among strains causing urinary tract infections, sepsis and other extraintestinal infections, Hly production was detected in 51% (P < 0.001), 32% (P < 0.001) and 18% (P < 0.02), respectively. In contrast, only 9% of faecal isolates from healthy individuals synthesized Hly. The 356 haemolytic E. coli strains characterized in this study belonged to 28 different serogroups. However, 284 (80%) were of one of eight serogroups (02, 04, 06, 08, 018, 022, 075 and 083); 40% and 31% of haemolytic strains expressed P fimbriae and mannose-resistant haemagglutination (MRHA) type III, respectively. We have found that haemolytic isolates of E. coli may clearly be divided into two categories on the basis of the ability to produce cytotoxic necrotizing factor type 1 (CNF1). The serogroups and adhesins determined in Hly+CNF1+ strains were generally different from those found in Hly+CNF1- strains. Thus, serogroups 02, 06 and 075 were associated with haemolytic E. coli producing CNF1+, whereas serogroups 01, 08, 018, 028 and 086 were established more frequently among Hly+CNF1- strains. While expression of P fimbriae was more frequently detected in Hly+CNF1- strains (70 versus 29%, P < 0.001), MRHA type III was usually identified in Hly+CNF1+ E. coli (42 versus 1%, P < 0.001). Furthermore, the sonic extracts of Hly+CNF1+ strains caused necrosis in rabbit skin (96 versus 25%, P < 0.001) and death in intraperitoneally injected mice (73 versus 11%, P < 0.001) more frequently than sonic extracts of Hly+CNF1- strains.     

Aerobactin and other virulence factor genes among strains of Escherichia coli causing urosepsis: association with patient characteristics.

To assess the role of aerobactin as a virulence factor among uropathogenic Escherichia coli, we determined the prevalence, location, and phenotypic expression of aerobactin determinants among 58 E. coli strains causing bacteremic urinary tract infections. We correlated the presence of the aerobactin system with antimicrobial-agent resistance, the presence and phenotypic expression of other uropathogenic virulence factor determinants (P fimbriae, hemolysin, and type 1 fimbriae), and characteristics of patients. Colony and Southern hybridization of total and plasmid DNA with DNA probes for each virulence factor showed that aerobactin determinants were present in 78% of the strains and were plasmid associated in 21%, whereas P fimbria, hemolysin, and type 1 fimbria determinants were present in 74, 43, and 98% of the strains, respectively, and were always chromosomal. Chromosomal aerobactin, P fimbria, and hemolysin determinants occurred together on the chromosome more often in strains from patients without predisposing urological or medical conditions (P = 0.04). Strains with plasmid-encoded aerobactin lacked determinants for P fimbriae (P = 0.004) and hemolysin (P = 0.0004), were resistant to multiple antimicrobial agents (P = 0.0001), and were found only in compromised patients. Mating experiments demonstrated that some aerobactin plasmids also encoded antimicrobial-agent resistance. These findings suggest that the determinants for aerobactin, P fimbriae, and hemolysin are conserved on the chromosome of the antimicrobial-agent-susceptible uropathogenic strains of E. coli which invade noncompromised patients. In contrast, these chromosomal virulence factors are often absent from E. coli strains causing urosepsis in compromised hosts; these strains may acquire plasmid aerobactin in conjunction with antimicrobial-agent resistance genes.     

Genomic Analysis of a Pathogenicity Island in Uropathogenic Escherichia coli CFT073: Distribution of Homologous Sequences among Isolates from Patients with Pyelonephritis, Cystitis, and CatheterAssociated Bacteriuria and from Fecal Samples

Urinary tract infection is the most frequently diagnosed kidney and urologic disease and Escherichia coli is by far the most common etiologic agent. Uropathogenic strains have been shown to contain blocks of DNA termed pathogenicity islands (PAIs) which contribute to their virulence. We have defined one of these regions of DNA within the chromosome of a highly virulent E. coli strain, CFT073, isolated from the blood and urine of a woman with acute pyelonephritis. The 57,988-bp stretch of DNA has characteristics which define PAIs, including a size greater than 30 kb, the presence of insertion sequences, distinct segmentation of K-12 and J96 origin, GC content (42.9%) different from that of total genomic DNA (50.8%), and the presence of virulence genes (hly and pap). Within this region, we have identified 44 open reading frames; of these 44, 10 are homologous to entries in the complete K-12 genome sequence, 4 are nearly identical to the sequences of E. coli J96 encoding the HlyA hemolysin, 11 encode P fimbriae, and 19 show no homology to J96 or K-12 entries. To determine whether sequences found within the junctions of the PAI of CFT073 were common to other uropathogenic strains of E. coli, 11 probes were isolated along the length of the PAI and were hybridized to dot blots of genomic DNA isolated from clinical isolates (67 from patients with acute pyelonephritis, 38 from patients with cystitis, 49 from patients with catheter-associated bacteriuria, and 27 from fecal samples). These sequences were found significantly more often in strains associated with the clinical syndromes of acute pyelonephritis (79%) and cystitis (82%) than in those associated with catheter-associated bacteriuria (58%) and in fecal strains (22%) (P < 0.001). From these regions, we have identified a putative iron transport system and genes other than hly and pap that may contribute to the virulent phenotype of uropathogenic E. coli strains.     

Escherichia coli from urine of female patients with urinary tract infections is competent for intracellular bacterial community formation

Nearly 50% of women experience at least one urinary tract infection (UTI) in their lifetime. Studies with mice have revealed that uropathogenic Escherichia coli (UPEC) isolates invade superficial umbrella cells that line the bladder, allowing them to find a safe haven and subvert clearance by innate host responses. Rapid intracellular replication results in the formation of distinctive intracellular bacterial communities (IBCs). In this study, we evaluated whether UPEC strains cultured from the urine of women and classified as causing acute cystitis, recurrent cystitis, asymptomatic bacteriuria, or pyelonephritis could progress through the IBC cascade in a well-characterized mouse model of cystitis. Of 18 UPEC isolates collected from women, 15 formed IBCs. Variations in the size, number, and kinetics of IBC formation were observed with strains isolated from women with different clinical syndromes. Two of the three isolates that did not form IBCs when inoculated alone were able to do so when coinoculated with an isolate that was capable of generating IBCs. The mixed infections dramatically altered the behavior of the coinfecting bacteria relative to their behavior in a single infection. The study also showed that mice with five different genetic backgrounds can support IBC formation. Although UPEC isolates differ genetically in their virulence factors, the majority of UPEC isolates from different types of UTI proceed through the IBC pathway, confirming the generality of IBCs in UTI pathogenesis in mice.