Identification of S, F1C and three PapG fimbrial adhesins in uropathogenic Escherichia coli by polymerase chain reaction

Molecular Epidemiology of Extraintestinal Pathogenic Escherichia coli

Extraintestinal pathogenic Escherichia coli (ExPEC) are important pathogens in humans and certain animals. Molecular epidemiological analyses of ExPEC are based on structured observations of E. coli strains as they occur in the wild. By assessing real-world phenomena as they occur in authentic contexts and hosts, they provide an important complement to experimental assessment. Fundamental to the success of molecular epidemiological studies are the careful selection of subjects and the use of appropriate typing methods and statistical analysis. To date, molecular epidemiological studies have yielded numerous important insights into putative virulence factors, host-pathogen relationships, phylogenetic background, reservoirs, antimicrobial-resistant strains, clinical diagnostics, and transmission pathways of ExPEC, and have delineated areas in which further study is needed. The rapid pace of discovery of new putative virulence factors and the increasing awareness of the importance of virulence factor regulation, expression, and molecular variation should stimulate many future molecular epidemiological investigations. The growing sophistication and availability of molecular typing methodologies, and of the new computational and statistical approaches that are being developed to address the huge amounts of data that whole genome sequencing generates, provide improved tools for such studies and allow new questions to be addressed.

Cross Talk between MarR-Like Transcription Factors Coordinates the Regulation of Motility in Uropathogenic Escherichia coli

The MarR-like protein PapX represses the transcription of the flagellar master regulator genes flhDC in uropathogenic Escherichia coli (UPEC), the primary cause of uncomplicated urinary tract infections (UTIs). PapX is encoded by the pap operon, which also encodes the adherence factors termed P fimbriae.

The MarR-like protein PapX represses the transcription of the flagellar master regulator genes flhDC in uropathogenic Escherichia coli (UPEC), the primary cause of uncomplicated urinary tract infections (UTIs). PapX is encoded by the pap operon, which also encodes the adherence factors termed P fimbriae. Both adherence and motility are critical for productive colonization of the urinary tract. However, the mechanisms involved in coordinating the transition between adherence and motility are not well characterized. UPEC strain CFT073 carries both papX and a homolog, focX, located in the foc operon encoding F1C fimbriae. In this study, we characterized the dose effects of “X” genes on flagellar gene expression and cross talk between focX and papX. We found that both FocX and PapX repress flhD transcription. However, we determined that the ΔpapX mutant was hypermotile, while the loss of focX did not affect motility. We further investigated this phenotype and found that FocX functions as a repressor of papX. Additionally, we identified a proximal independent promoter upstream of both focX and papX and assessed the expression of focX and papX during culture in human urine and on LB agar plates compared to LB medium. Finally, we characterized the contributions of PapX and FocX to fitness in the ascending murine model of UTI and observed a subtle, but not statistically significant, fitness defect in colonization of the kidneys. Altogether, these results expand our understanding of the impact of carrying multiple X genes on the coordinated regulation of motility and adherence in UPEC.

Multilocus Sequence Typing and Virulence Profiles in Uropathogenic Escherichia coli Isolated from Cats in the United States

The population structure, virulence, and antimicrobial resistance of uropathogenic E. coli (UPEC) from cats are rarely characterized. The aim of this study was to compare and characterize the UPEC isolated from cats in four geographic regions of USA in terms of their multilocus sequence typing (MLST), virulence profiles, clinical signs, antimicrobial resistance and phylogenetic grouping. The results showed that a total of 74 E. coli isolates were typed to 40 sequence types with 10 being novel. The most frequent phylogenetic group was B2 (n = 57). The most frequent sequence types were ST73 (n = 12) and ST83 (n = 6), ST73 was represented by four multidrug resistant (MDR) and eight non-multidrug resistant (SDR) isolates, and ST83 were significantly more likely to exhibit no drug resistant (NDR) isolates carrying the highest number of virulence genes. Additionally, MDR isolates were more diverse, and followed by SDR and NDR isolates in regards to the distribution of the STs. afa/draBC was the most prevalent among the 29 virulence-associated genes. Linking virulence profile and antimicrobial resistance, the majority of virulence-associated genes tested were more prevalent in NDR isolates, and followed by SDR and MDR isolates. Twenty (50%) MLST types in this study have previously been associated with human isolates, suggesting that these STs are potentially zoonotic. Our data enhanced the understanding of E. coli population structure and virulence association from cats. The diverse and various combinations of virulence-associated genes implied that the infection control may be challenging.

Molecular Epidemiology of Extraintestinal Pathogenic Escherichia coli

Extraintestinal pathogenic Escherichia coli (ExPEC), the specialized E. coli strains that possess the ability to overcome or subvert host defenses and cause extraintestinal disease, are important pathogens in humans and certain animals. Molecular epidemiological analysis has led to an appreciation of ExPEC as being distinct from other E. coli (including intestinal pathogenic and commensal variants) and has offered insights into the ecology, evolution, reservoirs, transmission pathways, host-pathogen interactions, and pathogenetic mechanisms of ExPEC. Molecular epidemiological analysis also provides an essential complement to experimental assessment of virulence mechanisms. This chapter first reviews the basic conceptual and methodological underpinnings of the molecular epidemiological approach and then summarizes the main aspects of ExPEC that have been investigated using this approach.

Detection of pap, sfa, afa, foc, and fim Adhesin-Encoding Operons in Uropathogenic Escherichia coli Isolates Collected From Patients With Urinary Tract Infection

Background:

Uropathogenic Escherichia coli (UPEC) with its virulence factors is the most prevalent cause of urinary tract infection (UTI).

Objectives;

This study aimed to determine the occurrence of fim, pap, sfa, and afa genes among 100 UPEC isolates collected from patients diagnosed with UTI.

Materials and Methods

A total of 100 UPEC isolates were obtained from urine samples of patients with UTI. The prevalence of 5 virulence genes encoding type 1 fimbriae (fimH), pili associated with pyelonephritis (pap), S and F1C fimbriae (sfa and foc) and afimbrial adhesins (afa) were determined through PCR method. We also investigated the phylogenetic background of all isolates. In addition, the distribution of adhesin-encoding operons between the phylogroups was assessed.

Results:

The prevalence of genes encoding for fimbrial adhesive systems was 95% for fim, 57% for pap, 16% for foc, and 81% for sfa. The operons encoding for afa afimbrial adhesins were identified in 12% of isolates. The various combinations of detected genes were designated as virulence patterns. The fim gene, which occurred in strains from all phylogenetic groups (A, B1, B2, and D) was evaluated and no significant differences were found among these groups. Conversely, significant differences were observed in relation to pap, afa, foc, and sfa operons.

Conclusions:

These results indicate that the PCR method is a powerful genotypic assay for the detection of adhesin-encoding operons. Thus, this assay can be recommended for clinical use to detect virulent urinary E. coli strains, as well as epidemiological studies.

Association of antibiotic resistance in agricultural Escherichia coli isolates with attachment to quartz

Surface water can be contaminated by bacteria from various sources, including manure from agricultural facilities. Attachment of these bacteria to soil and organic particles contributes to their transport through the environment, though the mechanism of attachment is unknown. As bacterial attachment to human tissues is known to be correlated with antibiotic resistance, we have investigated here the relationship between bacterial attachment to environmental particles and antibiotic resistance in agricultural isolates. We evaluated 203 Escherichia coli isolates collected from swine facilities for attachment to quartz, resistance to 13 antibiotics, and the presence of genes encoding 13 attachment factors. The genes encoding type I, EcpA, P pili, and Ag43 were detected, though none was significantly related to attachment. Quartz attachment was positively and significantly (P < 0.0038) related to combined resistance to amoxicillin/streptomycin/tetracycline/sulfamethazine/tylosin/chlortetracycline and negatively and significantly (P < 0.0038) related to combined resistance to nalidixic acid/kanamycin/neomycin. These results provide clear evidence for a link between antibiotic resistance and attachment to quartz in agricultural isolates. We propose that this may be due to encoding by the responsible genes on a mobile genetic element. Further exploration of the relationship between antibiotic resistance and attachment to environmental particles will improve the understanding and modeling of environmental transport processes, with the goal of preventing human exposure to antibiotic-resistant or virulent microorganisms.

Different roles of host and bacterial factors in Escherichia coli extra-intestinal infections

Many host and bacterial factors contribute to the development of different Escherichia coli extra-intestinal infections. The aim of this study was to evaluate the roles of host and bacterial factors in different extra-intestinal E. coli infections. A total of 221 E. coli isolates collected from urine, bile and peritoneal fluid were included in this retrospective study. Four main phylogenetic groups of E. coli, 14 genetic determinants, static biofilm formation and antimicrobial resistance data were assessed, as well as the immunological status of the hosts. Group B2 was the most common phylogenetic group (30%), especially in cases of asymptomatic bacteriuria (ABU), urinary tract infection (UTI), acute appendicitis/gastrointestinal perforation, and spontaneous bacterial peritonitis (SBP), and was associated with elevated prevalence of papG III, fimH, sfa, iha, hlyA, cnf1, ompT and usp. Phylogenetic group A was most common in the isolates from asymptomatic bacteriocholia, biliary tract infection, and peritoneal dialysis (PD)-related peritonitis. There was similarity with respect to both phylogenetic groups and virulence factors in strains from faeces and ABU, and in strains from faeces and SBP/PD-related peritonitis. Host characteristics were important in patients with ABU, UTI, and SBP/PD-related peritonitis. Immunocompetence of hosts was associated with a relatively high prevalence of papG II, afa and iha, and relatively low antimicrobial resistance to fluoroquinolones. This study demonstrates that, in most E. coli extra-intestinal infections, phylogenetic group B2 was predominant and was more virulent than the three other phylogenetic groups in the Taiwanese population studied. The diverse patterns of host and bacterial factors demonstrate that there were different host and bacterial factors dominating in different extra-intestinal E. coli infections.

Genomic islands of uropathogenic Escherichia coli contribute to virulence

Uropathogenic Escherichia coli (UPEC) strain CFT073 contains 13 large genomic islands ranging in size from 32 kb to 123 kb. Eleven of these genomic islands were individually deleted from the genome, and nine isogenic mutants were tested for their ability to colonize the CBA/J mouse model of ascending urinary tract infection. Three genomic island mutants (Delta PAI-aspV, Delta PAI-metV, and Delta PAI-asnT) were significantly outcompeted by wild-type CFT073 in the bladders and/or kidneys following transurethral cochallenge (P <or= 0.0139). The PAI-metV mutant also showed significant attenuation in the ability to independently colonize the kidneys (P = 0.0011). Specific genes within these islands contributed to the observed phenotype, including a previously uncharacterized iron acquisition cluster, fbpABCD (c0294 to c0297 [c0294-97]), autotransporter, picU (c0350), and RTX family exoprotein, tosA (c0363) in the PAI-aspV island. The double deletion mutant with deletions in both copies of the fbp iron acquisition operon (Deltac0294-97 Delta c2518-15) was significantly outcompeted by wild-type CFT073 in cochallenge. Strains with mutations in a type VI secretion system within the PAI-metV island did not show attenuation. The attenuation of the PAI-metV island was localized to genes c3405-10, encoding a putative phosphotransferase transport system, which is common to UPEC and avian pathogenic E. coli strains but absent from E. coli K-12. We have shown that, in addition to encoding virulence genes, genomic islands contribute to the overall fitness of UPEC strain CFT073 in vivo.

Defining genomic islands and uropathogen-specific genes in uropathogenic Escherichia coli

Uropathogenic Escherichia coli (UPEC) strains are responsible for the majority of uncomplicated urinary tract infections, which can present clinically as cystitis or pyelonephritis. UPEC strain CFT073, isolated from the blood of a patient with acute pyelonephritis, was most cytotoxic and most virulent in mice among our strain collection. Based on the genome sequence of CFT073, microarrays were utilized in comparative genomic hybridization (CGH) analysis of a panel of uropathogenic and fecal/commensal E. coli isolates. Genomic DNA from seven UPEC (three pyelonephritis and four cystitis) isolates and three fecal/commensal strains, including K-12 MG1655, was hybridized to the CFT073 microarray. The CFT073 genome contains 5,379 genes; CGH analysis revealed that 2,820 (52.4%) of these genes were common to all 11 E. coli strains, yet only 173 UPEC-specific genes were found by CGH to be present in all UPEC strains but in none of the fecal/commensal strains. When the sequences of three additional sequenced UPEC strains (UTI89, 536, and F11) and a commensal strain (HS) were added to the analysis, 131 genes present in all UPEC strains but in no fecal/commensal strains were identified. Seven previously unrecognized genomic islands (>30 kb) were delineated by CGH in addition to the three known pathogenicity islands. These genomic islands comprise 672 kb of the 5,231-kb (12.8%) genome, demonstrating the importance of horizontal transfer for UPEC and the mosaic structure of the genome. UPEC strains contain a greater number of iron acquisition systems than do fecal/commensal strains, which is reflective of the adaptation to the iron-limiting urinary tract environment. Each strain displayed distinct differences in the number and type of known virulence factors. The large number of hypothetical genes in the CFT073 genome, especially those shown to be UPEC specific, strongly suggests that many urovirulence factors remain uncharacterized.

Comparison of urovirulence factors and genotypes for bacteria causing acute lobar nephronia and acute pyelonephritis

BACKGROUND

Acute lobar nephronia (ALN) is a severe renal parenchymal inflammatory disease that has been diagnosed with increasing frequency as a result of newer noninvasive diagnostic modalities. Escherichia coli is the most common bacterial pathogen isolated from the urine samples of ALN patients. This prospective study was conducted to elucidate and distinguish the bacterial virulence factors associated with ALN and acute pyelonephritis (APN) in pediatric patients.

METHODS

Patients included in the present study were those suspected of an upper urinary tract infection who underwent ultrasonographic, computed tomographic and technetium 99m-dimercaptosuccinic acid scintigraphic evaluation to distinguish between ALN and APN. The E. coli isolates from the urine samples of patients were screened with polymerase chain reaction analysis for various urovirulence genes. Pulsed-field gel electrophoresis was used to analyze the genetic association of the isolates.

RESULTS

A total of 88 patients were enrolled. Forty-six patients were diagnosed with ALN and 42 with APN. Demographic characteristics and clinical results were similar except for longer fever duration before admission, longer fever continuation following antibiotic treatment and higher C-reactive protein values noted in the ALN group. Diverse genotypes were found among the E. coli isolates in both groups. Among the pathogenetic determinants examined, multivariate logistic regression analysis indicated that a papG II allele was the only significant urovirulence factor associated with ALN (P < 0.005; odds ratio, 17.16). This association was independent of the presence of VUR.

CONCLUSIONS

While no specific genetic lineage was identified among the E. coli isolates studied, a papG II gene was found to be strongly associated with the cause of ALN among pediatric patients.

Common virulence factors and genetic relationships between O18:K1:H7 Escherichia coli isolates of human and avian origin

Extraintestinal pathogenic (ExPEC) Escherichia coli strains of serotype O18:K1:H7 are mainly responsible for neonatal meningitis and sepsis in humans and belong to a limited number of closely related clones. The same serotype is also frequently isolated from the extraintestinal lesions of colibacillosis in poultry, but it is not well known to what extent human and avian strains of this particular serotype are related. Twenty-two ExPEC isolates of human origin and 33 isolates of avian origin were compared on the basis of their virulence determinants, lethality for chicks, pulsed-field gel electrophoresis (PFGE) patterns, and classification in the main phylogenetic groups. Both avian and human isolates were lethal for chicks and harbored similar virulence genotypes. A major virulence pattern, identified in 75% of the isolates, was characterized by the presence of F1 variant fimbriae; S fimbriae; IbeA; the aerobactin system; and genomic fragments A9, A12, D1, D7, D10, and D11 and by the absence of P fimbriae, F1C fimbriae, Afa adhesin, and CNF1. All but one of the avian and human isolates also belonged to major phylogenetic group B2. However, various subclonal populations could be distinguished by PFGE in relation to animal species and geographical origin. These results demonstrate that very closely related clones can be recovered from extraintestinal infections in humans and chickens and suggest that avian pathogenic E. coli isolates of serotype O18:K1:H7 are potential human pathogens.

Molecular epidemiology of extraintestinal pathogenic (uropathogenic) Escherichia coli

Molecular epidemiological analyses of extraintestinal pathogenic Escherichia coli (ExPEC), which are also called "uropathogenic E. coli" since they are the principle pathogens in urinary tract infection, involve structured observations of E. coli as they occur in the wild. Careful selection of subjects and use of appropriate methods for genotyping and statistical analysis are required for optimal results. Molecular epidemiological studies have helped to clarify the host-pathogen relationships, phylogenetic background, reservoirs, and transmission pathways of ExPEC, to assess potential vaccine candidates, and to delineate areas for further study. Ongoing discovery of new putative virulence factors (VFs), increasing awareness of the importance of VF expression and molecular variants of VFs, and growing appreciation of transmission as an important contributor to ExPEC infections provide abundant stimulus for future molecular epidemiological studies. Published by Elsevier GmbH.

Coordinate expression of fimbriae in uropathogenic Escherichia coli

Uropathogenic Escherichia coli is the most common etiological agent of urinary tract infections. Bacteria can often express multiple adhesins during infection in order to favor attachment to specific niches within the urinary tract. We have recently demonstrated that type 1 fimbria, a phase-variable virulence factor involved in adherence, was the most highly expressed adhesin during urinary tract infection. Here, we examine whether the expression of type 1 fimbriae can affect the expression of other adhesins. Type 1 fimbrial phase-locked mutants of E. coli strain CFT073, which harbors genes for numerous adhesins, were employed in this study. CFT073-specific DNA microarray analysis of these strains demonstrates that the expression of type 1 fimbriae coordinately affects the expression of P fimbriae in an inverse manner. This represents evidence for direct communication between genes relating to pathogenesis, perhaps to aid the sequential occupation of different urinary tract tissues. While the role of type 1 fimbriae during infection has been clear, the role of P fimbriae must be further defined to assert the relevance of coordinated regulation in vivo. Therefore, we examined the ability of P fimbrial isogenic mutants, constructed in a type 1 fimbrial-negative background, to compete in the murine urinary tract over a period of 168 h. No differences in the colonization of these mutants were observed. However, comparison of these results with previous studies suggests that inversely coordinated expression of adhesin gene clusters does occur in vivo. Interestingly, the mutant that was incapable of expressing either type 1 or P fimbriae compensated by synthesizing F1C fimbriae.

Host and bacterial virulence factors predisposing to emphysematous pyelonephritis

BACKGROUND

Emphysematous pyelonephritis (EPN) is a rare, severe, gas-forming infection of the kidney, and its precise pathogenesis remains obscure.

METHODS

To investigate the roles of host and bacterial virulence factors in the pathogenesis of EPN, we compared: (1) host factors in patients with EPN (n = 47) with those in patients with acute renal infections without gas formation (non-EPN; n = 79), (2) the prevalence of virulence gene in causative Escherichia coli strains from 16 of the 47 EPN cases with all 79 non-EPN cases by means of polymerase chain reaction analysis, and (3) gas volumes produced by EPN and non-EPN strains cultured in broths at 3 glucose concentrations (100, 180, and 250 mg/dL [5.6, 10.0, and 13.9 mmol/L]).

RESULTS

Diabetes mellitus (DM) with poor glycemic control (ie, hemoglobin A1c level > 11%) and urinary tract obstruction were more prevalent in the EPN group. However, DM with poor glycemic control was the only host factor independently associated with EPN (odds ratio, 4.9; P = 0.018). EPN strains had a greater prevalence of the uropathogenic-specific protein (usp) genes. Multivariate analyses also showed the association between usp and EPN with borderline significance (odds ratio, 8.4; P = 0.057). There was no significant difference in gas production by E coli isolated from patients with or without EPN.

CONCLUSION

DM with poor glycemic control and urinary tract obstruction are host factors predisposing to EPN. There was no difference in gas production between EPN and non-EPN E coli strains. The distribution of E coli virulence genes was remarkably similar between the 2 groups. However, the PapG II adhesin (papG II) gene is significantly decreased and the usp gene is increased with borderline significance in EPN E coli strains.

Comparative study of Escherichia coli virulence determinants in strains causing urinary tract bacteremia versus strains causing pyelonephritis and other sources of bacteremia

To assess the role of phylogenetic background and putative virulence factors (VFs) in Escherichia coli causing urinary bacteremia, 50 strains isolated from this condition were compared with 50 strains isolated from pyelonephritis and 50 from other sources of bacteremia. papA and papGII were significantly more prevalent in urinary bacteremia and pyelonephritis (78%, 66% and 70%, 58%) than in other-source bacteremia (48% and 24%), whereas sfa/focDE and cnf1 were more prevalent in urinary-source bacteremia (56% and 44%) than in pyelonephritis and other-source bacteremia (28%, 42% and 20%, 28%). Group B2 was the most frequent in all conditions (63% of isolates) and exhibited the greatest concentration of VFs. Urinary tract bacteremia, pyelonephritis, and other-source bacteremia isolates presented similar virulence scores (7.8, 7.0, and 6.6); however, there were striking differences among the phylogenetic groups (8.7 in group B2 versus 3.4 in group A; P < .001). Group A and B1 strains almost exclusively infected compromised hosts.

Bacterial response to eukaryotic cells

Host-bacteria interactions have mostly been investigated with regard to the host response or to activities of pathogenic bacteria. In contrast, we aim to identify reactions of non-pathogenic bacteria that result from their contact with host cells of the gastrointestinal tract. In a proteomic approach, the response of non-pathogenic human Escherichia coli bacteria on gut epithelial cells (rat IEC-6) was investigated in an in vitro co-culture model. For this purpose, a sensitive analytical procedure was developed based on the identification of two-dimensional polyacrylamide gel electrophoresis separated proteins by online nanoLC-electrospray ionization MS/MS using a quadrupole time-of-flight tandem mass spectrometer for accurate mass determination. We demonstrate here the efficiency of this technique by the identification of a total of 43 differentially expressed proteins, out of which 25 were up-regulated and 18 were down-regulated. They represent a wide range of molecular weight and different metabolic and physiological functions.

Detection of virulence factors in alpha-haemolytic Escherichia coli strains isolated from various clinical materials

In total, 201 alpha-haemolytic Escherichia coli isolates from various clinical materials (urine samples and vaginal and rectal swabs) were examined by PCR for the presence of genes for the virulence factors alpha-haemolysin (hly), cytotoxic necrotising factor type 1 (cnf1), P-fimbriae (pap), S/F1C-fimbriae (sfa/foc), aerobactin (aer) and afimbrial adhesin (afaI). Among vaginal isolates, 96% were positive for cnf1, compared with 80% of urine strains (p 0.02) and 63% of rectal strains (p 0.0001). Similarly, sfa/foc-specific DNA sequences were found in 97% of vaginal isolates compared with 75% of rectal strains (p 0.004). The afa1 and aer genes were associated more with rectal alpha-haemolytic E. coli strains than with extra-intestinal isolates. The results suggested that CNF1 and/or S/F1C-fimbriae contribute to colonisation and persistence of alpha-haemolytic E. coli strains in the vaginal environment.

Rapid identification of Escherichia coli pathotypes by virulence gene detection with DNA microarrays

One approach to the accurate determination of the pathogenic potential (pathotype) of isolated Escherichia coli strains would be through a complete assessment of each strain for the presence of all known E. coli virulence factors. To accomplish this, an E. coli virulence factor DNA microarray composed of 105 DNA PCR amplicons printed on glass slides and arranged in eight subarrays corresponding to different E. coli pathotypes was developed. Fluorescently labeled genomic DNAs from E. coli strains representing known pathotypes were initially hybridized to the virulence gene microarrays for both chip optimization and validation. Hybridization pattern analysis with clinical isolates permitted a rapid assessment of their virulence attributes and determination of the pathogenic group to which they belonged. Virulence factors belonging to two different pathotypes were detected in one human E. coli isolate (strain H87-5406). The microarray was also tested for its ability to distinguish among phylogenetic groups of genes by using gene probes derived from the attaching-and-effacing locus (espA, espB, tir). After hybridization with these probes, we were able to distinguish E. coli strains harboring espA, espB, and tir sequences closely related to the gene sequences of an enterohemorrhagic strain (EDL933), a human enteropathogenic strain (E2348/69), or an animal enteropathogenic strain (RDEC-1). Our results show that the virulence factor microarray is a powerful tool for diagnosis-based studies and that the concept is useful for both gene quantitation and subtyping. Additionally, the multitude of virulence genes present on the microarray should greatly facilitate the detection of virulence genes acquired by horizontal transfer and the identification of emerging pathotypes.

The role of bacterial virulence and host factors in patients with Escherichia coli bacteremia who have acute cholangitis or upper urinary tract infection

We studied the pathogenic role of host and Escherichia coli virulence factors in the development of E. coli bacteremia in patients with acute cholangitis (AC) or upper urinary tract infection (UTI). Isolates recovered from 75 adult patients consecutively admitted to the hospital with E. coli bacteremia caused by AC (n=24) or upper UTI (n=51) were evaluated, as were 30 fecal strains isolated from healthy control individuals. Virulence genes of E. coli were detected by polymerase chain reaction analysis, including papG genes (classes I-III), sfa/foc, fimH, afa, hlyA, cnf1, and iutA. Our results show that biliary tract obstruction and urinary tract obstruction are important host factors for the development of E. coli bacteremia in patients with AC and upper UTI, respectively. With regard to E. coli virulence factors, the papG class II gene might play a more important role in the development of E. coli bacteremia in patients with upper UTI than in those with AC.

Roles of host and bacterial virulence factors in the development of upper urinary tract infection caused by Escherichia coli

Aims of this study are to identify host and Escherichia coli virulence factors associated with upper urinary tract infection (UTI) by comparing them with those for lower UTI and determining the association between major predisposing host factors for upper UTI and urovirulence genes for E coli. Host factors and urovirulence genes of E coli associated with bacteremia in patients with upper UTI and their interactions also were studied. One hundred thirty-nine adult patients who fulfilled clinical diagnostic criteria for upper (n = 81) or lower UTI (n = 58) caused by E coli between January 1997 and December 1999 were retrospectively enrolled into this study. Old age (> or =60 years), male sex, diabetes with poor blood glucose control (ie, glycosylated hemoglobin A1C > or = 8.1%), immunosuppression, and urinary tract obstruction were more frequently associated host factors for patients with upper UTI than for those with lower UTI. Using polymerase chain reaction, the papG class II allele was detected more frequently for E coli strains isolated from patients with upper UTI than for those from patients with lower UTI (85% versus 52%; P < 0.0001). Multivariate analysis showed that diabetes with poor blood glucose control, immunosuppression, urinary tract obstruction, and papG class II allele were independently associated with upper UTI. For patients without these three predisposing host factors, the prevalence of papG class II allele was significantly greater in those with upper UTI than those with lower UTI. However, the papG class II allele was less prevalent in strains isolated from patients with upper UTI with urinary tract obstruction or with two of the three predisposing host factors. In addition, both univariate and multivariate analyses showed that old age and papG class II allele were risk factors for the development of E coli bacteremia in patients with upper UTI. In conclusion, both host and E coli virulence factors contribute to the development of upper UTI, and less virulent strains can cause upper UTI in hosts with predisposing factors.

Virulence factors of Escherichia coli isolated from female reproductive tract infections and neonatal sepsis

OBJECTIVE

The presence of enterobacteria such as Escherichia coli in the vagina of normal women is not synonymous with infection. However, vaginal E. coli may also cause symptomatic infections. We examined bacterial virulence properties that may promote symptomatic female reproductive tract infections (RTI) and neonatal sepsis.

METHODS

E. coli isolated as the causative agent from cases of vaginitis (n = 50), tubo-ovarian abscess (n = 45) and neonatal sepsis (n = 45) was examined for selected phenotypic and genetic virulence properties. Results were compared with the frequency of the same properties among fecal E. coli not associated with disease.

RESULTS

A significantly greater proportion of infection E. coli exhibited D-mannose resistant hemagglutination compared with fecal E. coli (p < 0.01). This adherence phenotype was associated with the presence of P fimbriae (pap) genes which were also significantly more prevalent among isolates from all three infection sites (p < 0.01). The majority of pap+ isolates contained the papG3 allele (Class II) regardless of infection type. Increased frequency of Type IC genes among vaginitis and abscess isolates was also noted. No significant differences in frequency of other bacterial adherence genes, fim, sfa, uca (gaf or dra were observed. E. coli associated with vaginitis was significantly more likely to be hemolytic (Hly+) than were fecal isolates (p < 0.05). The Hly+ phenotype was also more prevalent among tubo-ovarian abscess and neonatal sepsis isolates (p < 0.08).

CONCLUSIONS

E. coli isolated from female RTI and neonatal sepses possess unique properties that may enhance their virulence. These properties are similar to those associated with other E. coli extra-intestinal infections, indicating that strategies such as vaccination or bacterial interference that may be developed against urinary tract infections (UTI) and other E. coli extra-intestinal infections may also prevent selected female RTI.

Quantitative PCR

The classic molecular biology methods like Northern or Southern blot analyse non-amplified DNA or RNA, but need large amounts of nucleic acids, in many instances from tissues or cells that are heterogeneous. In contrast, polymerase chain reaction (PCR)-based techniques allow us to obtain genetic information through the specific amplification of nucleic acid sequences starting with a very low number of target copies. These reactions are characterized by a logarithmic amplification of the target sequences i.e. increase of PCR copies followed by a plateau phase showing a rapid decrease to zero of copy number increment per cycle. Accordingly, the amount of specific DNA product at the end of the PCR run bears no correlation to the number of target copies present in the original specimen. However, many applications in medicine or research require quantification of the number of specific targets in the specimen. This has generated a rapidly increasing need for the development of quantitative PCR techniques. Prominent examples are the determination of viral load in blood specimens for the diagnosis of HIV or HCV infections, the determination of changes in gene dosage through amplification or deletion e.g. of MDR-1, erb-B2, c-myc or the loss of heterozygosity in general. Finally, the analysis of gene expression on the mRNA level does require quantitative approaches to reverse transcriptase PCR, e.g. for studies in morphogenesis or the profiling of cancer cells. Recent advances in technology allow detection of the increment per cycle of a specifically generated PCR product in "real-time mode". Together with the new powerful methods to dissect heterogeneous tissues or fractionate bodily fluids, this now sets the stage for a detailed analysis not only of the genes and genetic changes within a single cell, but also of the use such cell makes of its genes e.g. in pharmacogenomics. Examples of recent developments of the technology and their applications will be given.

Development of polymerase chain reaction-based assays for bacterial gene detection

Polymerase chain reaction-based assays provide rapid, simple, and sensitive detection of bacterial genes, but are not without their drawbacks. This review summarizes the principal advantages and disadvantages of PCR-based bacterial gene detection, provides guidelines for the development and validation of new PCR assays, and describes potential pitfalls that may be encountered and how these can be avoided.