Caracterización de Escherichia coli de los grupos filogenéticos A y B1 causantes de infección extraintestinal

Correlation of biofilm formation, virulence factors, and phylogenetic groups among Escherichia coli strains causing urinary tract infection: A global systematic review and meta-analysis

Background

Different virulence factors are involved in the pathogenesis of urinary tract infection (UTI) caused by Uropathogenic Escherichia coli (UPEC); hence, this study aimed to study the prevalence of biofilm formation, virulence factors, and phylogenetic groups and their correlation with biofilm formation among UPEC isolates through a systematic review and meta-analysis.

Materials and Methods

A literature search was conducted from 1, 2000, to the end of 2021 in different databases for studies that reported biofilm together with virulence genes or phylogenetic groups in UPEC isolates from patients with UTI according to PRISMA protocol. Data were analyzed by Comprehensive meta-analysis software.

Results

The pooled prevalence of biofilm formers was 74.7%. The combined prevalence of phylogenetic Groups A, B1, B2, and D (s) were reported at 19.6%, 11%, 50.7%, and 20.5%, respectively. The most common virulence genes reported worldwide were fimA, ecpA, and fimH, with a combined prevalence of 90.3%, 86.6%, and 64.9%, respectively. The pooled prevalence of biofilm formation in UPEC isolates with phylogenetic Groups A, B1, B2, D, C, and F were 12.4%, 8.7%, 33.7%, 12.4%, 2.6%, and 2.65%, respectively. Several studies showed a correlation between biofilm production and virulence genes, or phylogenetic groups.

Conclusion

Regarding data obtained, the high level of combined biofilm formation (74.7%) and the presence of a positive correlation between biofilm production and virulence genes, or phylogenetic groups as reported by the most studies included in the present review, indicates an important role of biofilm in the persistence of UPEC in the UTI.

Virulence and antibiotic resistance profile of avian Escherichia coli strains isolated from colibacillosis lesions in central of Algeria

Background and Aim

Avian pathogenic Escherichia coli cause extensive mortality in poultry flocks, leading to extensive economic losses. To date, in Algeria, little information has been available on virulence potential and antibiotics resistance of avian E. coli isolates. Therefore, the aim of this study was the characterization of virulence genes and antibiotic resistance profile of Algerian E. coli strains isolated from diseased broilers.

Materials and Methods

In this study, 43 avian E. coli strains isolated from chicken colibacillosis lesions at different years were analyzed to determine their contents in 10 virulence factors by polymerase chain reaction, antimicrobial susceptibility to 22 antibiotics belonging to six different chemical classes and genomic diversity by pulsed-field gel electrophoresis (PFGE).

Results

Mainly E. coli isolates (58.1%) carried two at six virulence genes and the most frequent virulence gene association detected were ompT (protectin), hlyF (hemolysin) with 55.8% (p<0.001), and iroN, sitA (iron acquisition/uptake systems), and iss (protectin) with 41.8% (p<0.001). Some strains were diagnosed as virulent according to their virulence gene profile. Indeed, 23.25% of the isolates harbored iroN, ompT, hlyF, iss, and sitA combination, 14% ompT, hlyF, and frz_orf4 (sugar metabolism), and 11,6% iroN, hlyF, ompT, iss, iutA (iron acquisition/uptake systems), and frz _orf4. The chicken embryo lethality assay performed on five isolates confirmed the potential virulence of these strains. All isolates submitted to PFGE analysis yielded different genetic profiles, which revealed their diversity. Overall, 97.2% of the isolates were resistant to at least one antibiotic and 53.5% demonstrated multi-antimicrobial resistance to three different antimicrobial classes. The highest resistance levels were against nalidixic acid (83.4%), amoxicillin and ampicillin (83.3%), ticarcillin (80.5%), pipemidic acid (75%), and triméthoprim-sulfamethoxazole (66.6%). For beta-lactam class, the main phenotype observed belonged to broad-spectrum beta-lactamases. However, extended-spectrum beta-lactamase associated with three at six virulence factors was also detected in 13 isolates. Two of them were attested virulent as demonstrated in the embryo lethality test which constitutes a real public threat.

Conclusion

It would be imperative in avian production to discourage misuse while maintaining constant vigilance guidelines and regulations, to limit and rationalize antimicrobial use.

Phylogenetic analysis, biofilm production, and antimicrobial resistance profile of Escherichia coli isolated from slaughtered pigs

ABSTRACT Enteric diseases of bacterial origin are frequent in the pig industry, of particular notoriety are the colibacillosis that mainly affect piglets and cause great damage to the swine industry worldwide. The aim of the study was to analyze phylogenetics, to detect biofilm production, and to determine antimicrobial resistance profile in 126 strains of Escherichia coli isolated from swabs obtained from fragments of the small intestines of 235 healthy pigs killed in slaughterhouses in Pernambuco (Brazil) using polymerase chain reaction (PCR), adherence to microplates test and disc diffusion technique. Of the analyzed samples, 88.10% (111/126) were classified in phylogenetic group B1; 4.76% (6/126) in group D; 3.97% (5/126) in group B2 and, 3.17% (4/126) in group A. Antimicrobial resistance rates observed were: lincomycin 100% (126/126), erythromycin 100% (126/126), chlortetracycline 94.44% (119/126), cephalothin 51.59% (65/126), ampicillin 38.89% (49/126), sulfamethoxazole + trimethoprim 37.3% (47/126), ciprofloxacin 19.84% (25/126), norfloxacin 14.29% (18/126), gentamicin 8.73% (11/126) and, chloramphenicol 5.55% (7/126). Multiple antibiotic resistance (MAR) ranged from 0.2 to 0.9. Of the strains tested 46.03% (58/126) produced biofilm, and 99.21% (125/126) of the strains exhibited multi-resistance. Further studies are required to elucidate the importance of each phylogenetic group in pigs and to prevent the propagation of multi-resistant E. coli strains.

[Genetic diversity of extraintestinal Escherichia coli strains producers of beta-lactamases TEM, SHV and CTX-M associated with healthcare]

INTRODUCTION

There are few reports from Venezuela describing the genetic basis that sustains the pathogenic potential and phylogenetics of Escherichia coli extraintestinal strains isolated in health care units.

OBJECTIVE

To establish the genetic diversity of extraintestinal E. coli strains producers of betalactamases TEM, SHV and CTX-M associated with healthcare.

MATERIALS AND METHODS

We studied a collection of 12 strains of extraintestinal E. coli with diminished sensitivity to broad-spectrum cephalosporins. Antimicrobial susceptibility was determined by minimum inhibitory concentration. We determined the phylogenetic groups, virulence factors and genes encoding antimicrobial resistance using PCR, and clonal characterization by repetitive element palindromic-PCR rep-PCR.

RESULTS

All strains showed resistance to cephalosporins and joint resistance to quinolones and aminoglycosides. The phylogenetic distribution showed that the A and B1 groups were the most frequent, followed by D and B2. We found all the virulence factors analyzed in the B2 group, and fimH gene was the most frequent among them. We found blaCTX-M in all strains,with a higher prevalence of blaCTX-M-8; two of these strains showed coproduction of blaCTX-M-9 and were genetically identified as blaCTXM-65 and blaCTX-M-147 by sequencing.

CONCLUSION

The strains under study showed genetic diversity, hosting a variety of virulence genes, as well as antimicrobial resistance with no particular phylogroup prevalence. This is the first report of blaCTX-M alleles in Venezuela and in the world associated to non-genetically related strains isolated in health care units, a situation that deserves attention, as well as the rationalization of antimicrobials use.

Characterization and virulence clustering analysis of extraintestinal pathogenic Escherichia coli isolated from swine in China

BACKGROUND

Swine extraintestinal pathogenic Escherichia coli (ExPEC) is an important pathogen that leads to economic and welfare costs in the swine industry worldwide, and is occurring with increasing frequency in China. By far, various virulence factors have been recognized in ExPEC. Here, we investigated the virulence genotypes and clonal structure of collected strains to improve the knowledge of phylogenetic traits of porcine ExPECs in China.

RESULTS

We isolated 64 Chinese porcine ExPEC strains from 2013 to 14 in China. By multiplex PCR, the distribution of isolates belonging to phylogenetic groups B1, B2, A and D was 9.4%, 10.9%, 57.8% and 21.9%, respectively. Nineteen virulence-related genes were detected by PCR assay; ompA, fimH, vat, traT and iutA were highly prevalent. Virulence-related genes were remarkably more prevalent in group B2 than in groups A, B1 and D; notably, usp, cnf1, hlyD, papA and ibeA were only found in group B2 strains. Genotyping analysis was performed and four clusters of strains (named I to IV) were identified. Cluster IV contained all isolates from group B2 and Cluster IV isolates had the strongest pathogenicity in a mouse infection model. As phylogenetic group B2 and D ExPEC isolates are generally considered virulent, multilocus sequence typing (MLST) analysis was performed for these isolates to further investigate genetic relationships. Two novel sequence types, ST5170 and ST5171, were discovered. Among the nine clonal complexes identified among our group B2 and D isolates, CC12 and CC95 have been indicated to have high zoonotic pathogenicity. The distinction between group B2 and non-B2 isolates in virulence and genotype accorded with MLST analysis.

CONCLUSION

This study reveals significant genetic diversity among ExPEC isolates and helps us to better understand their pathogenesis. Importantly, our data suggest group B2 (Cluster IV) strains have the highest risk of causing animal disease and illustrate the correlation between genotype and virulence.

Relationship between virulence factors, resistance to antibiotics and phylogenetic groups of uropathogenic Escherichia coli in two locations in Mexico

INTRODUCTION

Escherichia coli is the major causative agent of urinary tract infections (UTI), and virulence factors are responsible for the severity of these emerging infections. The aim of this study was to evaluate the relationship between virulence determinants and antibiotic susceptibility with phylogenetic groups of E.coli isolates of UTI in two locations in Mexico.

METHODS

An analysis was performed on 50 isolates of E.coli from the centre of the country and 57 from a town in the southwest. The isolates were characterized by phenotype (serotyping assays, in vitro adhesion, biofilm formation, production of haemolysin, and antibiotic susceptibility) and genotype (phylogenetic groups and virulence genes).

RESULTS

In the centre of the country location the phylogenetic group B2 (60%) and F (12%) were significantly more prevalent and had a higher frequency of genes, fimH (96%), iutA (66%), sat (36%), compared to the southwest location, where the group A (35%) and B1 (21%) were significantly predominant and had fewer virulence genes. About one-fifth (21.5%) of all isolates belonged to the O25-ST131 group. Haemolysin and biofilm producing strains were significantly higher in the southwest location. Resistance to ampicillin (92.5%), tetracycline (76.6%), and trimethoprim/sulfamethoxazole (70.1%) were the most common in both groups.

CONCLUSION

The phylogenetic group, virulence factors, and antibiotic susceptibility of the E.coli that causes UTI in the community, varies significantly among the Mexican populations studied. Phylogenetic groups A and B1 may be multidrug resistant and have the ability to produce UTI.

[Distribution of phylogenetic groups and virulence factors in CTX-M-15 β-lactamase-producing uropathogenic Escherichia coli strains isolated from patients in the community of Mérida, Venezuela]

In this study, the distribution of phylogenetic groups and the genetic detection of virulence factors in CTX-M-15 β-lactamase-producing uropathogenic Escherichia coli (UPEC) strains were analyzed. Twenty eight strains were isolated between January 2009 and July 2011 from patients with urinary tract infection (UTI) who attended the Public Health Laboratory at Mérida, Venezuela. Determination of phylogenetic groups and detection of six virulence genes, fimH, fyuA, kpsMTII, usp, PAI and papAH, were performed by PCR amplification. Fifteen of the 28 isolates were mainly located in the phylogenetic group A, followed by B2 (12/28) and D (1/28). No direct relationship between the severity or recurrence of UTI and the distribution of phylogroups was observed. All studied virulence factors were found in group B2 strains with the highest frequency. The prevalent virulence profile included the combination of three main genes: fimH, kpsMTII and fyuA and, to a lesser extent, the presence of other determinants such as usp, PAI and/or papAH. These results indicate that virulent UPEC incorporated three important properties: adhesion, iron uptake and evasion of phagocytosis, which favored the production of recurrent UTI. This is the first report describing the association of phylogenetic groups with the potential virulence of CTX-M-15 β-lactamase producing UPEC strains in Venezuela.

Inhibitor-resistant TEM- and OXA-1-producing Escherichia coli isolates resistant to amoxicillin-clavulanate are more clonal and possess lower virulence gene content than susceptible clinical isolates

In a previous prospective multicenter study in Spain, we found that OXA-1 and inhibitor-resistant TEM (IRT) β-lactamases constitute the most common plasmid-borne mechanisms of genuine amoxicillin-clavulanate (AMC) resistance in Escherichia coli. In the present study, we investigated the population structure and virulence traits of clinical AMC-resistant E. coli strains expressing OXA-1 or IRT and compared these traits to those in a control group of clinical AMC-susceptible E. coli isolates. All OXA-1-producing (n = 67) and IRT-producing (n = 45) isolates were matched by geographical and temporal origin to the AMC-susceptible control set (n = 56). We performed multilocus sequence typing and phylogenetic group characterization for each isolate and then studied the isolates for the presence of 49 virulence factors (VFs) by PCR and sequencing. The most prevalent clone detected was distinct for each group: group C isolates of sequence type (ST) 88 (C/ST88) were the most common in OXA-1 producers, B2/ST131 isolates were the most common in IRT producers, and B2/ST73 isolates were the most common in AMC-susceptible isolates. The median numbers of isolates per ST were 3.72 in OXA-1 producers, 2.04 in IRT producers, and 1.69 in AMC-susceptible isolates; the proportions of STs represented by one unique isolate in each group were 19.4%, 31.1%, and 48.2%, respectively. The sum of all VFs detected, calculated as a virulence score, was significantly higher in AMC-susceptible isolates than OXA-1 and IRT producers (means, 12.5 versus 8.3 and 8.2, respectively). Our findings suggest that IRT- and OXA-1-producing E. coli isolates resistant to AMC have a different and less diverse population structure than AMC-susceptible clinical E. coli isolates. The AMC-susceptible population also contains more VFs than AMC-resistant isolates.

Long-term dissemination of acquired AmpC β-lactamases among Klebsiella spp. and Escherichia coli in Portuguese clinical settings

We investigated the occurrence, diversity and molecular epidemiology of genes coding for acquired AmpC β-lactamases (qAmpC) among clinical isolates of Enterobacteriaceae lacking inducible chromosomal AmpCs in Portugal. A total of 675 isolates non-susceptible to broad-spectrum cephalosporins obtained from four hospitals and three community laboratories during a 7-year period (2002-2008) were analysed. The presence of genes coding for qAmpC was investigated by phenotypic criteria, polymerase chain reaction (PCR) and sequencing. Bacterial identification, antibiotic susceptibility testing, conjugation assays and clonal analysis were performed by standard procedures. The presence of bla(qAmpC) genes was detected in 50 % (50/100; 41 Klebsiella pneumoniae, 5 Escherichia coli, 4 Klebsiella oxytoca) of the presumptive qAmpC producers. DHA-1, detected in those species, was the most prevalent qAmpC (94 %, 47/50), being identified since 2003 and throughout the studied period in different institutions. Despite the high clonal diversity observed, three DHA-1-producing Klebsiella spp. clones were more frequently identified. CMY-2 (6 %, 3/50) was observed in B1-E. coli clones. Conjugative transfer was only observed in one (2 %) CMY-2-producing isolate. Most qAmpC producers (94 %, 47/50) co-expressed SHV-type and/or OXA-1 or CTX-M-32 extended-spectrum β-lactamases (ESBLs). To the authors' knowledge, this is the first description of the molecular epidemiology and the long-term dissemination of qAmpC-producing Enterobacteriaceae in Portuguese clinical settings, highlighting an evolution towards a more complex epidemiological situation regarding cephalosporin resistance in Portugal.

Commensal Enterobacteriaceae as reservoirs of extended-spectrum beta-lactamases, integrons, and sul genes in Portugal

Bacteria colonizing the human intestine have a relevant role in the spread of antimicrobial resistance. We investigated the faecal carriage of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae in healthy humans from Portugal and analyzed the distribution of sul genes and class 1 and 2 integrons. Faecal samples (n = 113) were recovered from healthy persons (North/Centre of Portugal, 2001-2004) and plated on MacConkey agar with and without ceftazidime (1 mg/L) or cefotaxime (1 mg/L). Isolates representing different morphotypes/plate and antibiotic susceptibility patterns (n = 201) were selected. Isolates resistant to sulfonamides and/or streptomycin, gentamicin, and trimethoprim were screened (PCR and sequencing) for sul genes (sul1, sul2, sul3) and class 1 and 2 integrons. Presence of ESBLs was inferred using the double disk synergy test (DDST) and further confirmed by PCR and sequencing. ESBL producers were selected for clonal analysis, plasmid characterization and conjugation assays by standard methods. ESBL-producing isolates were found in 1.8% (2/113) of samples, corresponding to Escherichia coli of phylogroups A (n = 1) and B1 (n = 1) carrying transferable bla CTX-M-14 and the new bla TEM-153, respectively. A 80kb IncK plasmid bearing bla CTX-M-14 was found, being highly related to that widely spread among CTX-M-14 producers of humans and animals from Portugal and other European countries. sul genes were found in 88% (22/25; sul2-60%, sul1-48%, sul3-4%) of the sulfonamide resistant isolates. Class 1 integrons were more frequently found than class 2 (7%, 14/201 vs. 3%, 6/201). Interestingly, gene cassette arrangements within these platforms were identical to those commonly observed among Enterobacteriaceae from Portuguese food-producing animals, although aadA13 is here firstly described in Morganella morganii. These results reinforce the relevance of human commensal flora as reservoir of clinically relevant antibiotic resistance genes including bla ESBLs, and highly transferable genetic platforms as IncK epidemic plasmids.

Virulence profiles of bacteremic extended-spectrum β-lactamase-producing Escherichia coli: association with epidemiological and clinical features

There is scarce data about the importance of phylogroups and virulence factors (VF) in bloodstream infections (BSI) caused by extended-spectrum β-lactamase-producing Escherichia coli (ESBLEC). A prospective multicenter Spanish cohort including 191 cases of BSI due to ESBLEC was studied. Phylogroups and 25 VF genes were investigated by PCR. ESBLEC were classified into clusters according to their virulence profiles. The association of phylogropus, VF, and clusters with epidemiological features were studied using multivariate analysis. Overall, 57.6%, 26.7%, and 15.7% of isolates belonged to A/B1, D and B2 phylogroups, respectively. By multivariate analysis (adjusted OR [95% CI]), virulence cluster C2 was independently associated with urinary tract source (5.05 [0.96–25.48]); cluster C4 with sources other than urinary of biliary tract (2.89 [1.05–7.93]), and cluster C5 with BSI in non-predisposed patients (2.80 [0.99–7.93]). Isolates producing CTX-M-9 group ESBLs and from phylogroup D predominated among cluster C2 and C5, while CTX-M-1 group of ESBL and phylogroup B2 predominantes among C4 isolates. These results suggest that host factors and previous antimicrobial use were more important than phylogroup or specific VF in the occurrence of BSI due to ESBLEC. However, some associations between virulence clusters and some specific epidemiological features were found.

Clonal analysis and virulent traits of pathogenic extraintestinal Escherichia coli isolates from swine in China

BACKGROUND

Extraintestinal pathogenic Escherichia coli (ExPEC) can cause a variety of infections outside the gastrointestinal tract in humans and animals. Infections due to swine ExPECs have been occurring with increasing frequency in China. These ExPECs may now be considered a new food-borne pathogen that causes cross-infections between humans and pigs. Knowledge of the clonal structure and virulence genes is needed as a framework to improve the understanding of phylogenetic traits of porcine ExPECs.

RESULTS

Multilocus sequence typing (MLST) data showed that the isolates investigated in this study could be placed into four main clonal complexes, designated as CC10, CC1687, CC88 and CC58. Strains within CC10 were classified as phylogroup A, and these accounted for most of our porcine ExPEC isolates. Isolates in the CC1687 clonal complex, formed by new sequence types (STs), was classified as phylogroup D, with CC88 isolates considered as B2 and CC58 isolates as B1. Porcine ExPECs in these four clonal complexes demonstrated significantly different virulence gene patterns. A few porcine ExPECs were indentified in phylogroup B2, the phylogroup in which human ExPECs mainly exist. However some STs in the four clonal groups of porcine ExPECs were reported to cause extraintestinal infections in human, based on data in the MLST database.

CONCLUSION

Porcine ExPECs have different virulence gene patterns for different clonal complexes. However, these strains are mostly fell in phylogenentic phylogroup A, B1 and D, which is different from human ExPECs that concentrate in phylogroup B2. Our findings provide a better understanding relating to the clonal structure of ExPECs in diseased pigs and indicate a need to re-evaluate their contribution to human ExPEC diseases.

Chicken as reservoir for extraintestinal pathogenic Escherichia coli in humans, Canada

Urinary tract infections can be difficult and expensive to treat. Most (85%) are caused by bacteria called E. coli. Historically, doctors have believed that these urinary tract E. coli came from the patient’s own intestines. But recently, Canadian researchers discovered that not only can these E. coli come from outside the patient’s intestines, they can actually come from outside the patient: from food. After comparing the genetic makeup of E. coli from human urinary tract infections with E. coli from retail meat (chicken, beef, and pork), they concluded that chickens are a likely source of E. coli and that the infections probably come directly from the chickens themselves, not from human contamination during food processing. Therefore, prevention of E. coli urinary tract infections in people might need to start on chicken farms.

We previously described how retail meat, particularly chicken, might be a reservoir for extraintestinal pathogenic Escherichia coli (ExPEC) causing urinary tract infections (UTIs) in humans. To rule out retail beef and pork as potential reservoirs, we tested 320 additional E. coli isolates from these meats. Isolates from beef and pork were significantly less likely than those from chicken to be genetically related to isolates from humans with UTIs. We then tested whether the reservoir for ExPEC in humans could be food animals themselves by comparing geographically and temporally matched E. coli isolates from 475 humans with UTIs and from cecal contents of 349 slaughtered animals. We found genetic similarities between E. coli from animals in abattoirs, principally chickens, and ExPEC causing UTIs in humans. ExPEC transmission from food animals could be responsible for human infections, and chickens are the most probable reservoir.

Major differences exist in frequencies of virulence factors and multidrug resistance between community and nosocomial Escherichia coli bloodstream isolates

Escherichia coli is a major cause of bloodstream infections and death due to sepsis. It is the most frequent Gram-negative bacterial pathogen recovered from cultures of blood from both community-acquired and nosocomial cases. We set out to determine the relationships between E. coli virulence factors (VFs), phylogenetic groups, and antibiotic resistance and whether bacteremia cases had a community, health care-associated. or nosocomial origin. Isolates from consecutive episodes of E. coli bacteremia in 303 patients presenting to a university hospital were screened for their VFs, phylogenetic group, and antibiotic resistance. The majority of VFs present in the collection were equally distributed between antibiotic-susceptible and multiple-drug-resistant (MDR) isolates, but the overall VF score was higher for isolates of community and health care-associated origin than those of nosocomial origin (P = 0.0002 and P = 0.0172, respectively); the papA, papG allele II, hlyA, and hek VFs were more prevalent in this cohort. Most isolates belonged to phylogenetic group B2, which harbored a greater proportion of antibiotic-susceptible isolates than MDR isolates (P = 0.04). The community, health care-associated, or nosocomial origin of E. coli bacteremia determines the virulence capacity of an isolate better than the phylogenetic group does. This study provides new insights into the relationships between the pathogenesis and epidemiology of E. coli bacteremia.

Structure and urovirulence characteristics of the fecal Escherichia coli population among healthy women

The fecal Escherichia coli population structure may influence the occurrence and etiology of extraintestinal infection, but is poorly understood. Accordingly, fecal E. coli from 39 healthy women (30 putative colonies per subject) were characterized for clonal identity, urinary tract infection-associated virulence traits, and phylogenetic background. The 120 unique E. coli clones (mean, three per sample) were distributed by phylogenetic group as follows: A (33%), D (31%), B1 (19%), and B2 (17%). However, 36% of women carried > or =1 clone from group B2, and 87% had clones from groups B2 and/or D. Of the B2 clones, 90% were from pauciclonal fecal samples (< or =4 clones), compared with 47% and 52% of A and B1 clones (P=.001 and P=.007, respectively). Group B2 and D clones more often were dominant within the source sample than group A and B1 clones (60% vs. 41%: P=.05). Dominant clones exhibited higher virulence scores than non-dominant clones (mean 4.4 vs. 3.1: P=.015). In multilevel regression models, pauciclonal sample, B2, and clonal prevalence significantly predicted virulence score. In conclusion, within the intestinal E. coli population, virulence-associated traits, clonal prevalence, and low fecal clonal diversity are related. Virulence-associated traits of group B2/D E. coli may enhance fitness within the gut, thereby increasing strains' likelihood of causing extraintestinal infection.

Role of host and bacterial virulence factors in Escherichia coli spontaneous bacterial peritonitis

OBJECTIVES

Host factors and bacterial virulence determinants may play a role in Escherichia coli (E. coli) spontaneous bacterial peritonitis. We evaluated the importance of these factors in the emergence of fluoroquinolone-resistant strains and outcome in cirrhotic patients with E. coli spontaneous bacterial peritonitis.

METHODS

E. coli spontaneous bacterial peritonitis was detected in a 2-year period in three tertiary hospitals. Clinical and bacteriological data were obtained. Phylogenetic group and 15 virulence genes of E. coli strains were analyzed by polymerase gene reaction and compared with 50 isolates from pyelonephritis patients.

RESULTS

Forty-seven E. coli spontaneous bacterial peritonitis patients were identified, 18 (38%) were fluoroquinolone-resistant, a 12% increase compared with our earlier series from 1997 to 2002. Fluoroquinolone resistance was associated with norfloxacin prophylaxis, increased resistance to trimethoprim-sulfamethoxazole and cefotaxime, and less bacterial virulence, as demonstrated by a higher prevalence of 'nonpathogenic' phylogenetic groups A+B1 (56 vs. 28%; P=0.04) and lower virulence scores in fluoroquinolone-resistant E. coli compared with fluoroquinolone-susceptible E. coli. E. coli strains from cirrhotic patients belonged more frequently to 'nonpathogenic' phylogenetic groups A+B1, had fewer virulence factors and higher rates of fluoroquinolone resistance than isolates from pyelonephytis patients. Immunosuppression was independently associated with in-hospital and 3-month mortality. Bacterial virulence factors were unrelated to mortality.

CONCLUSION

Fluoroquinolone-resistant E. coli spontaneous bacterial peritonitis prevalence is increasing because of norfloxacin prophylaxis. Strains from peritonitis are less virulent than strains from pyelonephritis because of a higher prevalence of A+B1 phylogeny and quinolone resistance. Mortality is related to immunosuppression, but not to bacterial virulence factors.

Virulence and antimicrobial resistance profiles among Escherichia coli strains isolated from human and animal wastewater

To gain insight into whether Escherichia coli isolated from humans and resistant to some common antimicrobial agents are derived from animals, 85 E. coli strains were selected by ERIC-PCR from human and animal wastewater samples. Phylogroup, pathogenicity islands (PAIs), resistance to quinolones, fluoroquinolones and presence of extended-spectrum beta-lactamases (ESBLs) were analyzed. Among the total, 55% were resistant to nalidixic acid and 38% to ciprofloxacin; 12% produced ESBLs. Chicken-derived strains were associated with quinolone and fluoroquinolone resistance and presence of ESBLs, while human strains were associated with susceptibility. Group B2 E. coli strains were associated with human origin, susceptibility to fluoroquinolones and presence of PAIs, whereas groups A, B1 and D showed a low virulence profile and a high level of antimicrobial resistance. In both human and animal wastewater, E. coli A, B1 and D were prevalent, and strains from both origins showed a similar virulence profile in each phylogroup. These findings led us to hypothesize that abusive antibiotic use in food animal production may promote the development of resistance among these intestinal E. coli phylogroups, which could later be transmitted to humans through the food supply. The low prevalence of E. coli group B2 in the animal gut may explain, at least in part, the absence of emergence of resistant B2 isolates.