Detection of virulence genes in uropathogenic Escherichia coli by polymerase chain reaction (PCR): comparison with results obtained using phenotypic methods

Multidrug resistance in pathogenic Escherichia coli isolates from urinary tract infections in dogs, Spain

Escherichia coli (E. coli) is a pathogen frequently isolated in cases of urinary tract infections (UTIs) in both humans and dogs and evidence exists that dogs are reservoirs for human infections. In addition, E. coli is associated to increasing antimicrobial resistance rates. This study focuses on the analysis of antimicrobial resistance and the presence of selected virulence genes in E. coli isolates from a Spanish dog population suffering from UTI. This collection of isolates showed an extremely high level of phenotypic resistance to 1st-3rd generation cephalosporins, followed by penicillins, fluoroquinolones and amphenicols. Apart from that, 13.46% of them were considered extended-spectrum beta-lactamase producers. An alarmingly high percentage (71.15%) of multidrug resistant isolates were also detected. There was a good correlation between the antimicrobial resistance genes found and the phenotypic resistance expressed. Most of the isolates were classified as extraintestinal pathogenic E. coli, and two others harbored virulence factors related to diarrheagenic pathotypes. A significant relationship between low antibiotic resistance and high virulence factor carriage was found, but the mechanisms behind it are still poorly understood. The detection of high antimicrobial resistance rates to first-choice treatments highlights the need of constant antimicrobial resistance surveillance, as well as continuous revision of therapeutic guidelines for canine UTI to adapt them to changes in antimicrobial resistance patterns.

Severe outbreak of bovine neonatal diarrhea in a dairy calf rearing unit with multifactorial etiology

This study describes the etiological diversity observed in a severe neonatal diarrhea outbreak with morbidity and mortality rates of 80 and 20%, respectively, with detection of mixed infections with viral, bacterial, and protozoan disease agents in a dairy calf rearing unit. Diarrheic fecal samples were collected from eight 5 to 18 days of age calves and were submitted to the investigation of the presence of rotavirus A (RVA), bovine coronavirus (BCoV), bovine kobuvirus (BKV), bovine viral diarrhea virus 1 and 2 (BVDV-1 and BVDV-2), enteropathogenic Escherichia coli (ETEC), Salmonella sp., and Cryptosporidium spp. Fragments of the small intestine of one calf with diarrhea that spontaneously died were submitted for histopathological analyses. The most frequent infectious agent detected in diarrheic fecal samples was BKV (8/8—100%), followed by RVA (5/8—62.5%), BVDV (5/8—62.5%), Cryptosporidium parvum (5/8—62.5%), ETEC (4/8—50%), and Cryptosporidium ryanae (1/8—12.5%). These etiological agents were found in mixed infections with two or more pathogens per diarrheic fecal sample. The association of viral and protozoan pathogens was the most frequently identified (37.5%) in these samples, followed by viral and bacterial (25%); viral, bacterial, and protozoan (25%); and only viral agents (12.5%). BCoV and Salmonella sp. were not identified in the diarrheic fecal samples analyzed. Additionally, histopathology of the small intestine diagnosed chronic lymphocytic enteritis. In conclusion, in calf rearing units, the adoption and strict monitoring of health management practices are critical to the success of this calf creation system.

Antimicrobial resistance among canine enteric Escherichia coli isolates and prevalence of attaching-effacing and extraintestinal pathogenic virulence factors in Spain

The aim of this study was to estimate the prevalence of antimicrobial resistance (AMR) in Escherichia coli from a dog population in Spain and assess specific virulence factors. Susceptibility to 22 antimicrobials was tested along with the production of extended-spectrum β-lactamases (ESBLs) and AmpC in faecal isolates from 100 dogs. Virulence-related genes associated with attaching and effacing E. coli (eae, Stx1, Stx2) and extraintestinal pathogenic E. coli - ExPEC - (papC, hlyA and cnf1) were detected by PCR. At least one kind of AMR was observed in 73% of the isolates. The highest prevalences corresponded to penicillin (45%), aminoglycoside (40%) and non-extended spectrum cephalosporin (39%) classes. Multidrug resistance (MDR) was observed in 53.4% of the resistant isolates. No resistance to colistin was found. Production of ESBL/AmpC enzymes was detected in 5% of E. coli. Shiga toxin-producing E. coli were not observed, enteropathogenic E. coli were identified in only 12% of them, and ExPEC were found in 25%. Dog faeces can be a source of E. coli strains potentially presenting a threat to humans through their virulence factors or AMR. The non-hygienic keeping of animals may increase the risk of colonisation of such pathogens in humans.

Occurrence of ESBL-Producing Escherichia coli ST131, Including the H30-Rx and C1-M27 Subclones, Among Urban Seagulls from the United Kingdom

Antimicrobial resistance is a public health concern. Understanding any role that urban seagulls may have as a reservoir of resistant bacteria could be important for reducing transmission. This study investigated fecal Escherichia coli isolates from seagulls (herring gulls and lesser black-backed gulls) to determine the prevalence of extended-spectrum cephalosporin-resistant (ESC-R) and fluoroquinolone-resistant E. coli among gull species from two cities (Taunton and Birmingham) in the United Kingdom (UK). We characterized the genetic background and carriage of plasmid-mediated resistance genes in extended-spectrum β-lactamase (ESBL)-producing E. coli obtained from these birds. Sixty ESC-R E. coli isolates were obtained from 39 seagulls (39/78, 50%), of which 28 (28/60, 46.7%) were positive for plasmid-mediated CTX-M and/or AmpC β-lactamase resistance genes. Among these, bla_CTX-M-15, bla_CTX-M-14, and bla_CMY-2 predominated. Three isolates belonging to the B2-ST131 clone were detected, of which two harbored bla_CTX-M-15 (typed to C2/H30Rx) and one harbored bla_CTX-M-27 and was typed to C1/H30-R (recently described as the C1-M27 sublineage). The plasmid-mediated quinolone resistance (PMQR) gene carriage prevalence (11.7%) consisted of aac(6')-Ib-cr and qnrB genes. No carbapenem or colistin resistance genes were detected. Urban seagulls in the UK are colonized and can spread major antimicrobial-resistant E. coli isolates harboring ESBL and PMQR determinants, including clinically important strains such as the pandemic clone B2-ST131 and the C1-M27 subclade. This is the first report of ST131-C1-M27 subclade in wildlife in the UK and in seagulls worldwide.

Detecção dos genes codificantes da toxina CDT, e pesquisa de fatores que influenciam na produção de hemolisinas em amostras de Campylobacter jejuni de origem avícola

Resumo: Membros termofílicos do gênero Campylobacter são reconhecidos como importantes enteropatógenos para o ser humano e animais. A grande diversidade ecológica destes micro-organismos em diferentes habitats tais como água, animais e alimentos predispõem ao aparecimento de novos fatores de virulência. Este trabalho teve por objetivo detectar os genes codificantes da Toxina Distensiva Citoletal (CDT) por meio da técnica de PCR, pesquisar a atividade de hemolisinas e a influência de soluções quelantes e de íons nesta atividade. Foram utilizadas 45 amostras de Campylobacter jejuni de origem avícola para pesquisa de atividade hemolítica, cultivadas em Caldo Triptona de Soja (TSB). Após o crescimento bacteriano, as amostras foram semeadas em Ágar tríptico de soja (TSA) contendo 5% de sangue de ovino. Para verificar a influência de agentes quelantes e solução de íons na atividade hemolítica, as amostras de C. jejuni foram cultivadas em TSB contendo separadamente os quelantes EDTA, ácido acético, soluções de íons CaCl2, MgCl2 e FeCl3, em atmosfera de microaerofilia. Quanto à atividade de hemolisina de C. jejuni em placas de TSA - sangue ovino foi possível observar que houve hemólise em 40% das amostras analisadas apenas com caldo TSB. Somente o ácido acético apresentou ação quelante sobre a atividade de hemolisinas em amostras de C. jejuni semeadas em placas de TSA - sangue ovino. Para detecção dos genes cdtA, cdtB e cdtC através da técnica da Reação em Cadeia da Polimerase (PCR) foram utilizadas 119 amostras de C. jejuni de origem avícola. Foi possível observar que 37,8% possuíam o perfil de genes cdtABC. Os resultados demonstraram em amostras avícolas a presença de cepas de C. jejuni com potencial virulento, devido à presença dos genes da toxina CDT e potencial hemolítico, que apresentou ação reduzida in vitro com ácido acético.

The influence of antibiotic resistance gene carriage on biofilm formation by two Escherichia coli strains associated with urinary tract infections

Urinary tract infections (UTI) caused by uropathogenic Escherichia coli are one of the most common forms of human disease. In this study, the effect of the presence of newly acquired antibiotic resistance genes on biofilm formation of UTI-associated E. coli strains was examined. Two clinical UTI-associated E. coli strains (SMC18 and SMC20) carrying different combinations of virulence genes were transformed with pGEM-T, pGEM-T::KmΔAmp, or pGEM-T::Km to construct ampicillin-resistant (KmSAmpR), kanamycin-resistant (KmRAmpS), or ampicillin- and kanamycin-resistant (KmRAmpR) strains. Transformed and wild-type strains were characterized for biofilm formation, bacterial surface hydrophobicity, auto-aggregation, morphology, and attachment to abiotic surfaces. Transformation with a plasmid carrying an ampicillin resistance gene alone decreased (p < 0.05) biofilm formation by SMC18 (8 virulence marker genes) but increased (p < 0.05) biofilm formation by SMC20 (5 virulence marker genes). On the other hand, transformation with a plasmid carrying a kanamycin resistance gene alone or both ampicillin and kanamycin resistance genes resulted in a decrease (p < 0.05) in biofilm formation by SMC18 but did not affect (p > 0.05) the biofilm formation by SMC20. Our results suggest that transformation of UTI-associated E. coli with plasmids carrying different antibiotic resistance gene(s) had a significant impact on biofilm formation and that these effects were both strain dependent and varied between different antibiotics.

Virulence factors and genetic variability of uropathogenic Escherichia coli isolated from dogs and cats in Italy

In this study, the association between virulence genotypes and phylogenetic groups among Escherichia (E.) coli isolates obtained from pet dogs and cats with cystitis was detected, and fingerprinting methods were used to explore the relationship among strains. Forty uropathogenic E. coli (UPEC) isolated from dogs (n = 30) and cats (n = 10) in Italy were analysed by polymerase chain reaction (PCR) for the presence of virulence factors and their classification into phylogenetic groups. The same strains were characterized by repetitive extragenic palindromic (REP)- and enterobacterial repetitive intergenic consensus (ERIC)-PCR techniques. We found a high number of virulence factors such as fimbriae A, S fimbriae (sfa) and cytotoxic necrotizing factor 1 (cnf1) significantly associated with phylogenetic group B2. We demonstrated a high correlation between α-hemolysin A and pyelonephritis C, sfa, and cnf1 operons, confirming the presence of pathogenicity islands in these strains. In addition, UPEC belonging to group B2 harboured a greater number of virulence factors than strains from phylogenetic groups A, B1, and D. REP- and ERIC-PCR grouped the UPEC isolates into two major clusters, the former grouping E. coli strains belonging to phylogenetic group B2 and D, the latter grouping those belonging to groups A and B1. Given the significant genetic variability among the UPEC strains found in our study, it can be hypothesized that no specific genotype is responsible for cystitis in cats or dogs.

Occurrence and functionality of cycle inhibiting factor, cytotoxic necrotising factors and cytolethal distending toxins in Escherichia coli isolated from calves and dogs in Italy

Escherichia coli isolated from animals up to three months of age, with diarrhea (255 calves and 29 dogs (pups)), without diarrhea (21 calves and 11 pups, used as controls), and 58 adult dogs with cystitis were tested to investigate the occurrence and functional expression of cyclomodulins cycle inhibiting factor (CIF), cytotoxic necrotizing factors (CNFs) and cytolethal distending toxins (CDTs). In cyclomodulin-positive isolates the association was assessed with other virulence genotypes and phylogenetic groups. Of 374 E. coli isolates, 80 (21.4%) were positive for at least one cyclomodulin and 14 of the latter (3.7%) showed different combinations of more than one. cif-positive isolates showed a low number of additional virulence factors, and were commonly associated with phylogroup B1, while cnf- and cdt-positive isolates, harboring many extraintestinal virulence factors, belonged to phylogroups B2 and D. Almost all isolates showed an irreversible cytopathic effect (CPE), displaying functionality of cyclomodulins. Five isolates that presented a mutation of cif were CPE-negative.

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.

Measurement of biofilm formation by clinical isolates of Escherichia coli is method-dependent

AIMS

In this study, we have evaluated the impact of methodological approaches in the determination of biofilm formation by four clinical isolates of Escherichia coli in static assays.

METHODS AND RESULTS

The assays were performed in microtitre plates with two minimal and two enriched broths, with one- or two-steps protocol, and using three different mathematical formulas to quantify adherent bacteria. Different biofilm formation patterns were found depending on the E. coli strain, culture medium and reading optical density on one- and two-steps protocol. Strong or moderate biofilm formation occurred mostly in minimal media. The mathematical formulas used to quantify biofilm formation also gave different results and bacterial growth rate should be taken into account to quantify biofilm.

CONCLUSIONS

Escherichia coli forms biofilms on static assays in a method-dependent fashion, depending on strain, and it is strongly modulated by culture conditions.

SIGNIFICANCE AND IMPACT OF THE STUDY

As verified in the studied E. coli strains, biofilm formation by any organism should be cautiously interpreted, considering all variables in the experimental settings.

E. coli virulence factors in children with neurogenic bladder associated with bacteriuria

The value of E. coli virulence factors in patients with neurogenic bladder has not been established. The aim of this study is to correlate E. coli virulence factors with asymptomatic and symptomatic UTI in children with neurogenic bladder. Fifty E. coli strains, which were collected in sequence, underwent analysis in relation to: the association to pyuria, serotype (O:H), the presence of genes and expression of fimbriae P, type 1, S and hemagglutinin Dr, the presence of the gene and production of hemolysins and cytotoxins (CNF1). We also analyzed the cell adherence capability and pattern and presence of usp (uropathogenic-specific protein). Pyuria was present in most of the positive urine cultures, with 86% AB and 97% UTI. Low rates of uropathogenic strains were observed in the two groups, with 18% AB and 21% UTI. Type 1 fimbria predominated in 44% of the E. coli strains. Of the bacteria studied, 30% (15 strains) exhibited papG genotypes (11 class II and 4 class III). Of these, 12/15 patients presented AB. Production of hemolysins was detected in 38% of the strains (16 AB and 3 UTI) and usp in only 18% of the strains, with 8 AB and 1 UTI. Adherence tests demonstrated the adhesive capacity in all samples analyzed. Neither group (AB or symptomatic UTI) presented a statistically significant difference in relation to the virulence factors studied. E. coli clones that caused symptomatic UTI in children with neurogenic bladder expressed few virulence factors, with no statistically significant difference in comparison to the AB group.

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.

Search for cytolethal distending toxin production among fecal Escherichia coli isolates from Brazilian children with diarrhea and without diarrhea

The enteropathogenic role of cytolethal distending toxin-producing Escherichia coli was investigated by searching sequences homologous to the cdt genes of an O86 strain among 2,074 isolates from 200 children with acute diarrhea and 200 controls in Brazil. Only one (0.5%) diarrheic child and two (1.0%) non-diarrheic controls harbored cdt-positive isolates.

Occurrence and genetic association of selected virulence factors in clinical Escherichia coli isolates

Occurrence of cnf1+ E. coli pathogenic strains among extraintestinal E. coli isolates was evaluated to explain an impact of cytotoxic necrotizing factor type 1 (CNF1) in human infections. A total of 120 E. coli isolates were characterized for presence of virulence factors cnf1- and pap--specific sequences by PCR, and the production of alpha-hemolysin using blood agar-plate test. Different association patterns among the detected virulence factors were obtained by comparison of various groups of clinical E. coli isolates. These differences probably reflect a potential impact of CNF1 in the colonization of vaginal environment.

Detection of pap-, sfa- and afa-specific DNA sequences in Escherichia coli strains isolated from extraintestinal material

P-fimbriae, S-fimbriae and AFA-adhesins are virulence factors responsible for adherence of Escherichia coli strains to extraintestinal host-cell surface. Detection of pap-, sfa- and afa-specific sequences performed by PCR revealed 74% pap+, 65% sfa+, and 8.3% afa+ strains in a group of 84 extraintestinal E. coli isolates. Detection in a group of fecal strains showed 29% pap+, 21% sfa+ and 4% afa+ strains. pap together with sfa were found as the most frequent combination (56%) among extraintestinal isolates probably due to localization of pap- and sfa-operons on a common pathogenicity island. The occurrence of afa-specific sequence among 56 urine strains was 11%, although no afa+ strain was detected among 28 gynecological isolates. No strains with detected adhesin operons were found among twenty (24%) extraintestinal E. coli strains.

Escherichia coli serotype O15:K52:H1 as a uropathogenic clone

To clarify the clinical and bacteriological correlates of urinary-tract infection (UTI) due to Escherichia coli O15:K52:H1, during a 1-year surveillance period we prospectively screened all 1, 871 significant E. coli urine isolates at the Hospital de la Santa Creu i Sant Pau, Barcelona, Spain, for this serotype and assessed the epidemiological features of community-acquired UTI due to E. coli O15:K52:H1 versus other E. coli serotypes. We also compared the 25 O15:K52:H1 UTI isolates from the present study with 22 O15:K52:H1 isolates from other, diverse geographic locales and with 23 standard control strains (8 strains from the ECOR reference collection and 15 strains of nonpathogenic O:K:H serotypes) with respect to multiple phenotypic and genotypic traits. Although E. coli O15:K52:H1 caused only 1.4% of community-acquired E. coli UTIs during the surveillance period, these UTIs were more likely to present as pyelonephritis and to occur in younger hosts, with similar risk factors, than were UTIs due to other E. coli serotypes. Irrespective of geographic origin, E. coli O15:K52:H1 strains exhibited a comparatively restricted repertoire of distinctive virulence factor profiles (typically, they were positive for papG allele II, papA allele F16, and aer and negative for sfa, afa, hly, and cnf1), biotypes, ribotypes, and amplotypes, consistent with a common clonal origin. In contrast, their antimicrobial resistance profiles were more extensive and more diverse than those of control strains. These findings indicate that E. coli O15:K52:H1 constitutes a broadly distributed and clinically significant uropathogenic clone with fluid antimicrobial resistance capabilities.