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Molecular variations in Klebsiella pneumoniae and Escherichia coli FimH affect function and pathogenesis in the urinary tract.

ABSTRACT: Type 1 pili mediate binding, invasion, and biofilm formation of uropathogenic Escherichia coli (UPEC) in the host urothelium during urinary tract infection (UTI) via the adhesin FimH. In this study, we characterized the molecular basis of functional differences between FimH of the UPEC isolate UTI89 and the Klebsiella pneumoniae cystitis isolate TOP52. Type 1 pili characteristically mediate mannose-sensitive hemagglutination of guinea pig erythrocytes. Although the adhesin domain of K. pneumoniae TOP52 FimH (FimH(52)) is highly homologous to that of E. coli, with an identical mannose binding pocket and surrounding hydrophobic ridge, it lacks the ability to agglutinate guinea pig erythrocytes. In addition, FimH-dependent biofilm formation in K. pneumoniae is inhibited by heptyl mannose, but not methyl mannose, suggesting the need for contacts outside of the mannose binding pocket. The binding specificity differences observed for FimH(52) resulted in significant functional differences seen in the pathogenesis of K. pneumoniae UTI compared to E. coli UTI. Infections in a murine model of UTI demonstrated that although the K. pneumoniae strain TOP52 required FimH(52) for invasion and IBC formation in the bladder, FimH(52) was not essential for early colonization. This work reveals that a limited amount of sequence variation between the FimH of E. coli and K. pneumoniae results in significant differences in function and ability to colonize the urinary tract.

SUBMITTER: Rosen DA

PROVIDER: S-EPMC2446687 | biostudies-literature | 2008 Jul

REPOSITORIES: biostudies-literature

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Molecular variations in Klebsiella pneumoniae and Escherichia coli FimH affect function and pathogenesis in the urinary tract.

Rosen David A DA Pinkner Jerome S JS Walker Jennifer N JN Elam Jennifer Stine JS Jones Jennifer M JM Hultgren Scott J SJ

Infection and immunity 20080512 7

Type 1 pili mediate binding, invasion, and biofilm formation of uropathogenic Escherichia coli (UPEC) in the host urothelium during urinary tract infection (UTI) via the adhesin FimH. In this study, we characterized the molecular basis of functional differences between FimH of the UPEC isolate UTI89 and the Klebsiella pneumoniae cystitis isolate TOP52. Type 1 pili characteristically mediate mannose-sensitive hemagglutination of guinea pig erythrocytes. Although the adhesin domain of K. pneumonia ...[more]

PMID: 18474655

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Project description:ObjectivesUrinary tract infections (UTIs) in children are rapidly increasing worldwide and are commonly caused by extensively drug-resistant bacteria. This study determines the prevalence of UTIs in paediatric patients and evaluates the pattern of extensively drug-resistance in Escherichia coli and Klebsiella pneumoniae strains isolated from paediatric UTI patients.MethodsUropathogenic bacterial strains were isolated from paediatric patients with UTIs admitted to the Institute of Child Health, Lahore, Pakistan. Strains of both E. coli and K. pneumoniae were identified using biochemical characterisation and subjected to antibiotic susceptibility assays for 21 common antimicrobial drugs in order to determine their extensively drug-resistant profile.ResultsWe isolated 63 E. coli and 37 K. pneumoniae strains from 130 paediatric patients with UTIs over a period of six months. The antibiotic susceptibility assays showed that both the E. coli and K. pneumoniae strains exhibited a high degree of resistance against co-amoxiclav, cefuroxime, cefixime, cefotaxime, ceftazidime, ceftriaxone, ciprofloxacin, nalidixic acid, norfloxacin, pepedemic acid, and co-trimoxazole. However, several of the antimicrobial agents, including polymyxin B, colistin sulphate, chloramphenicol, nitrofurantoin, and fosfomycin, were found to retain their antimicrobial activities against both pathogens. The five highest antibiotic resistant strains were identified as E. coli strains ZK9, ZK40, and ZK60 and K. pneumoniae ZK32 and ZK89 using 16S rRNA gene sequencing.ConclusionOur study demonstrates that E. coli and K. pneumonia are the dominant extensively drug-resistant uropathogenic bacteria in community-acquired UTIs in our cohort. These uropathogens were found to be resistant to the majority of the routinely-used classes of β-lactams, pyridopyrimidines, quinolones, and fluoroquinolone antibiotics, and these findings may be useful for clinicians in their treatment of paediatric UTIs.

Project description:UnlabelledUropathogenic Escherichia coli (UPEC) is the primary etiological agent of over 85% of community-acquired urinary tract infections (UTIs). Mouse models of infection have shown that UPEC can invade bladder epithelial cells in a type 1 pilus-dependent mechanism, avoid a TLR4-mediated exocytic process, and escape into the host cell cytoplasm. The internalized UPEC can clonally replicate into biofilm-like intracellular bacterial communities (IBCs) of thousands of bacteria while avoiding many host clearance mechanisms. Importantly, IBCs have been documented in urine from women and children suffering acute UTI. To understand this protected bacterial niche, we elucidated the transcriptional profile of bacteria within IBCs using microarrays. We delineated the upregulation within the IBC of genes involved in iron acquisition, metabolism, and transport. Interestingly, lacZ was highly upregulated, suggesting that bacteria were sensing and/or utilizing a galactoside for metabolism in the IBC. A ?lacZ strain displayed significantly smaller IBCs than the wild-type strain and was attenuated during competitive infection with a wild-type strain. Similarly, a galK mutant resulted in smaller IBCs and attenuated infection. Further, analysis of the highly upregulated gene yeaR revealed that this gene contributes to oxidative stress resistance and type 1 pilus production. These results suggest that bacteria within the IBC are under oxidative stress and, consistent with previous reports, utilize nonglucose carbon metabolites. Better understanding of the bacterial mechanisms used for IBC development and establishment of infection may give insights into development of novel anti-virulence strategies.ImportanceUrinary tract infections (UTIs) are one of the most common bacterial infections, impacting mostly women. Every year, millions of UTIs occur in the U.S. with most being caused by uropathogenic E. coli(UPEC). During a UTI, UPEC invade bladder cells and form an intracellular bacterial community (IBC) that allows for the bacteria to replicate protected from the host immune response. In this study, we investigated genes that are expressed by UPEC within the IBC and determined how they contribute to the formation of this specialized community. Our findings suggest that galactose is important for UPEC growth in the IBC. Additionally, we found that a gene involved in oxidative stress is also important in the regulation of a key factor needed for UPEC invasion of bladder cells. These results may open the door for the development of treatments to diminish UTI frequency and/or severity.

Project description:BackgroundTransferrable mechanisms of quinolone resistance (TMQR) can lead to fluoroquinolone non-susceptibility in addition to chromosomal mechanisms. Some evidence suggests that fluoroquinolone resistance is increasing among the pediatric population. We sought to determine the occurrence of TMQR genes among quinolone-resistant E. coli and K. pneumoniae causing urinary tract infections among Nepalese outpatient children (< 18 years) and identify molecular characteristics of TMQR-harboring isolates.MethodsWe performed antimicrobial susceptibility testing, phenotypic extended-spectrum β-lactamase (ESBL) and modified carbapenem inactivation method tests, and investigated the presence of six TMQR genes (qnrA, qnrB, qnrS, aac(6')-Ib-cr, oqxAB, qepA), three ESBL genes (blaCTX-M, blaTEM, blaSHV), and five carbapenemase genes (blaNDM, blaOXA-48, blaKPC, blaIMP, blaVIM). The quinolone resistance-determining region (QRDR) of gyrA and parC were sequenced for 35 TMQR-positive isolates.ResultsA total of 74/147 (50.3%) isolates were TMQR positive by multiplex PCR [aac(6')-Ib-cr in 48 (32.7%), qnrB in 23 (15.7%), qnrS in 18 (12.3%), qnrA in 1 (0.7%), and oqxAB in 1 (0.7%) isolate]. The median ciprofloxacin minimum inhibitory concentration of TMQR-positive isolates (64 µg/mL) was two-fold higher than those without TMQR (32 µg/mL) (p = 0.004). Ser-83→Leu and Asp-87→Asn in GyrA and Ser-80→Ile in ParC were the most common QRDR mutations (23 of 35). In addition, there was a statistically significant association between TMQR and two β-lactamase genes; blaCTX-M (p = 0.037) and blaTEM (p = 0.000).ConclusionThis study suggests a high prevalence of TMQR among the quinolone-resistant E. coli and K. pneumoniae isolates causing urinary tract infection in children in this area of Nepal and an association with the carriage of ESBL gene. This is a challenge for the management of urinary infections in children. Comprehensive prospective surveillance of antimicrobial resistance in these common pathogens will be necessary to devise strategies to mitigate the emergence of further resistance.

Dataset Information

Molecular variations in Klebsiella pneumoniae and Escherichia coli FimH affect function and pathogenesis in the urinary tract.

Publications

Molecular variations in Klebsiella pneumoniae and Escherichia coli FimH affect function and pathogenesis in the urinary tract.

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