|Year : 2018 | Volume
| Issue : 3 | Page : 191-197
Distribution of virulence factors according to antibiotic susceptibility among Escherichia coli isolated from urinary tract infection
S Derakhshan1, M Pourzare2, D Roshani2
1 Department of Microbiology, Faculty of Medicine, Kurdistan University of Medical Sciences; Liver and Digestive Research Center, Kurdistan University of Medical Sciences, Sanandaj, Iran
2 Department of Microbiology, Faculty of Medicine, Kurdistan University of Medical Sciences, Sanandaj, Iran
|Date of Web Publication||29-May-2018|
Department of Microbiology, Faculty of Medicine, Kurdistan University of Medical Sciences, Sanandaj
Source of Support: None, Conflict of Interest: None
Escherichia coli is the major causative pathogen of urinary tract infection (UTI) in humans. Virulence and drug resistance play important roles in the pathogenesis of E. coli infections. The aims were to investigate the presence of uropathogenic virulence genes and to evaluate a relationship between antibiotic resistance and virulence in E. coli from UTI. A total of 132 E. coli were collected between April and June 2015 in two hospitals of Sanandaj, Iran. Isolates were examined for susceptibility to 16 antibiotic disks using the disk diffusion method and for possession of virulence genes by polymerase chain reaction. Associations between antimicrobial resistance and virulence genes were investigated. A P < 0.05 was considered significant. Of the 132 isolates, the most prevalent virulence gene was pap (31.1%), followed by cnf (28.8%), hly (16.7%), and afa (10.6%). Different patterns of virulence genes were identified. A significant association was detected between the simultaneous presence of hly and pap. The most effective antibiotics were nitrofurantoin, cefoxitin, and imipenem and the least effective were ampicillin, trimethoprim-sulfamethoxazole, and cefotaxime. An association was seen between the presence of cnf and susceptibility to the certain antibiotics, whereas strains with a reduced susceptibility to the certain antibiotics were associated with a significantly increased prevalence of afa and hly (P < 0.05). These findings suggest a correlation between the presence of virulence gene and resistance in E. coli strains from UTI. The results indicate that there is a need for surveillance programs to monitor drug resistance in pathogenic E. coli.
Keywords: Antimicrobial agents, Escherichia coli, resistance, urinary tract infection, virulence
|How to cite this article:|
Derakhshan S, Pourzare M, Roshani D. Distribution of virulence factors according to antibiotic susceptibility among Escherichia coli isolated from urinary tract infection. Indian J Nephrol 2018;28:191-7
|How to cite this URL:|
Derakhshan S, Pourzare M, Roshani D. Distribution of virulence factors according to antibiotic susceptibility among Escherichia coli isolated from urinary tract infection. Indian J Nephrol [serial online] 2018 [cited 2020 Feb 22];28:191-7. Available from: http://www.indianjnephrol.org/text.asp?2018/28/3/191/230217
| Introduction|| |
Pathogenic strains of Escherichia coli have the potential to cause a wide variety of infectious diseases, including neonatal meningitis, septicemia, intestinal tract infection, and urinary tract infections (UTIs). UTI is one of the most frequent bacterial infections, affecting both inpatients and outpatients, and E. coli is the major causative pathogen. Due to anatomical differences and the hormonal milieu of the urinary tract, the probability of developing a UTI in women is significantly more than men. It is estimated that around 50%–60% of women will experience a UTI during their lifetime.
UTI caused by E. coli strains remains an important health problem in many countries and leads to considerable morbidity costs.,, These strains encode various virulence factors such as toxins, capsules, invasins, and adhesins, which contribute to enhanced pathogenicity. The severity of UTI reflects the virulence profile of the infecting strain, and the frequency of expression of virulence factors is higher in more pathogenic strains.
Pyelonephritis-associated pilus (Pap), afimbrial adehsin (Afa), α-hemolysin (HlyA), and cytotoxic necrotizing factor 1 (CNF1) are among the most important virulence factors of E. coli involved in the development of UTI.,, Pap is one of the most commonly found adhesins. Binding of P-fimbrial adhesin to the cell receptors of renal tissue leads to mucosal inflammation and tissue damage. Afa has been implicated in the occurrence of recurrent and chronic UTIs. Apart from adhesins, exotoxins such as HlyA and CNF1 are also implicated in the pathogenesis of UTIs. HlyA encoded by hly is the most important secreted virulence factor of E. coli isolated from UTI. This toxin is able to lyse host cells for crossing of the mucosal barriers, having access to host nutrients and iron stores, and damaging effector immune cells such as T-lymphocytes and neutrophils. CNF1 has been shown to have a role in dissemination of strains in the urinary tract. This toxin causes bladder cell exfoliation and increases bacterial access to the underlying tissue.
Another problem is antibiotic resistance of the E. coli strains. The emergence of resistance limits the utility of older agents, such as trimethoprim-sulfamethoxazole (SXT), and increases reliance on newer broad-spectrum agents, such as extended-spectrum cephalosporins and fluoroquinolones. Unfortunately, emerging resistance now threatens the use of these newer agents as well.,, Resistance to antimicrobial agents is often associated with the spread of transmissible plasmids, which may also carry virulence determinants. Some studies showed that among clinical isolates of E. coli, the production of virulence factors is negatively associated with resistance to some antibiotics., On the other hand, such phenomenon was not observed in other studies.,, The acquisition of resistance and virulent traits may provide a benefit for the survival of microorganism. This situation may lead to ecological changes and domination of virulent antibiotic-resistant bacteria in the environment.
Hence, the aims of this study were to determine the presence of the most important virulence genes involved in the development of UTI including pap, afa, cnf-1, and hly,, among E. coli isolated from UTI and to evaluate a possible association between virulence factors and susceptibility to antimicrobial agents.
| Materials and Methods|| |
Bacterial isolates and identification
In this cross-sectional study, from April to June 2015, 132 consecutive nonduplicate E. coli were isolated from patients with UTI admitted to Besat and Tohid Tertiary Hospitals in Sanandaj, Iran. Sanandaj is the center of Kurdistan Province in the west of Iran, with a population of more than 300,000. The Besat and Tohid Hospitals are referral and teaching hospitals, which are affiliated to Kurdistan University of Medical Sciences. UTI was defined according to the 2015 European Association of Urology guidelines. E. coli isolates were identified according to the standard bacteriological and biochemical tests  including Gram staining, fermentation of lactose, motility, ability to produce indole, and lysine decarboxylation. All bacterial isolates were preserved at −70°C in Trypticase soy broth (Quelab, New Mexico, USA), containing 15% v/v glycerol for further investigations.
Antimicrobial susceptibility testing
Susceptibility of E. coli isolates was determined to 16 antibiotics using the disk diffusion method on Mueller-Hinton agar plates (Merck, Germany) as recommended by the 2014 Clinical and Laboratory Standards Institute guidelines. The following antibiotic disks (Rosco company, Denmark) were tested: ampicillin (AM) (10 μg), cefotaxime (CTX) (30 μg), ceftazidime (CAZ) (30 μg), imipenem (IPM) (10 μg), amoxicillin/clavulanic acid (AMC) (20/10 μg), aztreonam (AZT) (30 μg), ciprofloxacin (CP) (5 μg), tetracycline (TE) (30 μg), SXT, gentamicin (GM) (10 μg), cefepime (FEP) (30 μg), cefoxitin (CFO) (30 μg), amikacin (AN) (30 μg), norfloxacin (NOR) (10 μg), nalidixic acid (NA) (30 μg), and nitrofurantoin (FM) (300 μg). E. coli ATCC 25922 was used as a quality control strain.
DNA extraction and detection of virulence factors by polymerase chain reaction
Genomic DNA was extracted from E. coli strains by the freeze-thaw method and used as the template for polymerase chain reaction (PCR) reactions. For DNA extraction, bacterial pellets prepared from 1.5 ml of an overnight culture in brain–heart infusion broth (Quelab, New Mexico, USA) were suspended in 200 μl sterile distilled water, and the suspensions were heated at 100°C for 10 min. The suspensions were then immediately placed on ice for 5 min. Samples taken through a total of three cycles of freezing-thawing were centrifuged, and the supernatants were stored at −20°C as DNA template stocks.
Detection of virulence genes was carried out by PCR. Amplification of pap, afa, cnf-1, and hly was performed using published primer pairs (SinaClon, Iran) as follows: 5′-AACAAGGATAAGCACTGTTCTGGCT-3′, 5′-ACCA TATAAGCGGTCATTCCCGTCA-3′ (for hly, amplicon size: 1177 bp); 5′-AAGATGGAGTTTCCTATGCAGGAG-3′, 5′-CATTCAGAGTCCTGCCCTCATTATT-3′ (for cnf, amplicon size: 498 bp); 5′-GCTG GGCAGCAAACTGATAACTCTC-3′, 5′-CATCAAGCTGTTTGTTCGTCCGCCG-3′ (for afa, amplicon size: 750 bp); and 5′-GA CGGCTGTACTGCAGGGTGTGGCG-3′, 5′-ATATCCTTTCTGCAGGGATGCAATA-3′ (for pap, amplicon size: 328 bp).
Amplification reactions were done in a total volume of 25 μl containing 3 μl DNA extract, 1 U of Taq DNA polymerase, 0.4 μM of each primer, 1X reaction buffer, 1.5 mM MgCl2, and 200 μM of each dNTP (SinaClon, Iran). The PCR was performed in a thermal cycler (Eppendorf, Germany) under the following conditions: initial denaturation of 5 min at 94°C followed by 35 cycles of denaturation of 1 min at 94°C, annealing of 1 min at 65°C, extension of 1 min at 72°C, and a final extension of 7 min at 72°C. Conditions were the same for all genes.
The amplified products were separated on a 1% agarose gel (SinaClon) in 0.5X tris-borate EDTA buffer alongside an appropriate molecular size marker (100 bp Plus DNA ladder, SinaClon). The amplified products were visualized after staining with DNA safe stain (SinaClon) and photographed using a UV transillumination imaging system. Positive controls were kindly given by Dr. S. Najar Peerayeh (Tarbiat Modares University, Iran) and Dr. A. Rashki (University of Zabol, Iran).
Data were analyzed using SPSS software version 16.0 (SPSS, Chicago, IL, USA). The relationship between virulence factors and antibiotic susceptibility was determined using Pearson's Chi-square test or Fisher's exact test. To facilitate our analysis, the isolates showing intermediate susceptibility were grouped with the resistant strains. A P< 0.05 was considered significant.
| Results|| |
A total of 132 E. coli strains were collected from patients with UTI between April and June 2015. The average age of the patients was 35.7 years; the oldest patient was 93 years (one patient) and four 1-year-old children were the youngest patients. Among the 132 isolates, 107 isolates (81.1%) were from females and 25 (18.9%) were from males. Forty-seven (35.6%) of the 132 isolates were from hospitalized patients and 85 (64.4%) were from outpatients.
Antimicrobial susceptibility results showed that all isolates (97%) were susceptible to FM, except for four isolates. Of the 132 isolates, 122 (92.4%) were susceptible to CFO, 116 (87.9%) to IPM, 99 (75%) to AN, and 95 (72%) to AMC. The susceptibility rate of isolates to 16 antimicrobial agents is presented in [Table 1]. Compared with the isolates from inpatients, except for AMC, FM, IPM, AN, and GM, the frequency of susceptibility to the antimicrobial agents was higher or similar in the outpatients isolates [Table 1].
|Table 1: Antimicrobial susceptibility of 132 Escherichia coli isolated from urinary tract infection inpatient and outpatient groups|
Click here to view
Distribution of virulence genes
Prevalence of virulence genes was analyzed by PCR. Of the 132 isolates, the pap gene was found in 41 (31.1%) isolates, the cnf in 38 (28.8%), the hly in 22 (16.7%), and the afa in 14 (10.6%) isolates. Fifty-seven strains were negative for all the studied virulence genes. The prevalence of virulence genes was higher in males, except for afa, which was detected in a higher prevalence in females than in males (11.2% vs. 8%) [Table 2]. Among the studied virulence genes, only pap showed a meaningful difference of distribution according to sex group (P = 0.01).
|Table 2: Prevalence of the virulence genes among 132 Escherichia coli isolates from urinary tract infection in males and females|
Click here to view
Except pap gene, that its prevalence in the inpatient group was higher than outpatient group (16/47 [34%] vs. 25/85 [29.4%]), the prevalence of other virulence genes was higher in the outpatient group. The hly, cnf, and afa were detected in 7 (14.9%), 12 (25.5%), and 2 (4.3%) of the 47 strains collected from inpatients and in 15 (17.6%), 26 (30.6%), and 12 (14.1%) of the 85 strains collected from outpatients, respectively. However, the prevalence of virulence genes was not significantly different between the two groups (P > 0.05).
To identify phenotypes of the isolates, the prevalence of profiles of the virulence genes was ascertained. A total of 75 (56.8%) isolates were found to harbor at least one of the four urogenes investigated. The maximum number of detected amplicons in one strain was three of the virulence gene regions targeted. Combinations of adhesin and toxin genes encoded by E. coli isolates are presented in [Table 3]. Considering all virulence genes together, the studied strains exhibited 11 virulence gene profiles, referred to as urovirulence profile (UP) followed by an Arabic numeral. Of these 11 combinations, the most common gene profile was UP1, which was characterized by the presence of only the cnf gene (16 isolates) followed by UP2, which was found in 15 isolates and characterized by the presence of the pap gene only. The least distributed profile was UP11, which was detected in only one strain and characterized by the simultaneous presence of hly and afa genes.
|Table 3: Virulence patterns identified among 132 Escherichia coli isolated from urinary tract infection|
Click here to view
A significant association was detected between the simultaneous presence of hly and pap genes (P< 0.001), which corresponded to 14 (10.6%) strains. Sixteen isolates carried both pap and cnf, 10 strains hly and cnf, and three isolates pap and afa but lacked significance according to the Chi-square and Fisher's tests.
Associations between antimicrobial resistance and virulence traits
[Table 4] shows the prevalence of each virulence gene according to antibiotic susceptibility status of isolates. In general, pap was more prevalent in nonsusceptible isolates group (resistant plus intermediately resistant [for FEP: susceptible dose dependent]). Exceptions were beta-lactam antibiotics (IPM, CAZ, FEP, AZT, and CFO), for which susceptible isolates showed a higher prevalence of the pap gene. The afa gene was also more prevalent in nonsusceptible isolates, except TE, AN, FM, and AMC, for which the susceptible isolates showed a higher prevalence. By contrast, the cnf gene was more prevalent in susceptible isolates; the only exceptions were GM and FM for which nonsusceptible isolates showed a higher prevalence. The hly was almost equally distributed between susceptible and nonsusceptible groups although was slightly shifted toward susceptible isolates group and away from nonsusceptible isolates [Table 4].
|Table 4: Distribution of virulence genes according to antibiotic susceptibility among 132 Escherichia coli isolated from urinary tract infection|
Click here to view
The possible statistical association between antibiotic susceptibility/nonsusceptibility phenotypes and virulence genes of isolates was subsequently investigated. We found that the distribution of hly and pap in relation to antimicrobial resistance phenotypes was not different (P > 0.05), except that AN-susceptible isolates significantly exhibited a lower prevalence of the hly (P< 0.05). A more analysis revealed two further groups of associations: first, an association between the presence of afa and nonsusceptibility to beta-lactams (CTX and FEP) and the quinolone NA as well as the fluoroquinolone CP (P< 0.05), and second, an association between the presence of cnf and susceptibility to beta-lactams (AM, IPM, CAZ, FEP, AMC), quinolone (NA), and fluoroquinolones (CP, NOR) (P< 0.05) [Figure 1].
|Figure 1: Relationships between virulence factors and antimicrobial susceptibility: (a) susceptibility to the antibiotics shown was significantly related to the lower prevalence of hly and afa genes. (b) A significant relationship between presence of cnf gene and susceptibility to antibiotics (*P < 0.05)|
Click here to view
| Discussion|| |
UTI is one of the important bacterial infections, affecting both inpatients and outpatients, and E. coli is the leading causative agent of UTI. It is thought that the pathogenic potential of E. coli isolates is dependent on the presence of various virulence factors. In our study, of the 132 E. coli isolated from UTI, the pap gene was present in 31.1%, the afa in 10.6%, the cnf in 28.8%, and the hly in 16.7% of isolates. The hly was found to be significantly associated with pap. The pap adhesion gene was the most commonly identified virulence gene, in agreement with other reports.,, It has been shown that transformation of E. coli with pap sequence makes it a more potent inducer of the host response. It is conceivable that in some strains of E. coli, pap has important role in the progression to more severe infections of the urinary tract. Isolates from outpatients showed a higher prevalence of the studied virulence genes except pap gene.
In recent years, management of UTIs has become increasingly problematic due to the emergence of drug-resistant E. coli strains in many countries.,, The emergence of resistance limits the utility of older agents, such as SXT, which results in increased reliance on newer broad-spectrum agents, such as extended-spectrum cephalosporins and fluoroquinolones. Antibiotic sensitivity test in our isolates showed FM as the most effective followed by CFO and IPM. AM, SXT, and CTX were the least effective antibiotics. The isolates from outpatients were more resistant to FM, IPM, AMC, AN, and GM than those from inpatients, in particular AMC. The likely reasons for the high resistance rates to these antibiotics among outpatients are the inappropriate use of these antimicrobials, ineffective infection control and health programs, and cross-resistance among antibiotics of the same class, such as AN and GM. In humans, 80%–90% of antimicrobial drugs are used in outpatients, and it is estimated that 20%–50% of the use of antibiotics is questionable. Resistant strains can be traced from the community to hospitals and contribute to multidrug resistance in hospital settings.
Several studies indicate that resistance to some antibiotics is associated with decreased virulence traits among clinical E. coli isolates., On the other hand, such phenomenon was not observed in some other studies.,, We observed an association between the presence of cnf and susceptibility to the tested beta-lactams, quinolone, and fluoroquinolones [Figure 1]. However, E. coli strains with a reduced susceptibility to the studied extended-spectrum cephalosporins (CTX and FEP), quinolone NA, and fluoroquinolone CP were associated with a significantly increased prevalence of afa. E. coli strains expressing adhesins of the Afa family have unique renal tissue tropisms that favor the establishment of chronic and/or recurrent infections. Moreover, isolates with a reduced susceptibility to AN significantly exhibited a higher prevalence of the hly, resulting in a slightly increased inferred virulence potential compared with susceptible isolates. Compared to their susceptible counterparts, resistant bacterial infections with more virulence factors are generally associated with increased morbidity, mortality, and treatment costs.
The reasons for this correlation are not entirely clear. A biological basis for the association of antimicrobial resistance with virulence genes in E. coli has been previously reported for certain genes; for example, an 80-megadalton plasmid coding for AM resistance has been associated with genes for ST (heat-stable enterotoxin) synthesis. Recently, some in vitro studies have shown that decreased pathogenicity of E. coli is associated with the acquisition of quinolone resistance. Soto et al. suggested that subinhibitory concentrations of quinolones induce the SOS system response (DNA repairing mechanism), which could favor in vitro loss of virulence genes in E. coli strains. According to their results, the virulence genes may have been lost in exchange for resistance. However, the finding that spontaneous fluoroquinolone-resistant mutants derived from hemolytic fluoroquinolone-susceptible strains are still able to produce hemolysin  suggested otherwise. Although one hypothesis does not exclude the other, further studies are needed to consolidate the findings. It is also possible that ecological factors such as the geographic origin of isolates represent important additional factors that should be considered. It is worthwhile to investigate whether gene linkage on plasmids or other mobile genetic elements underlies the associations observed in our study.
In conclusion, this study describes the prevalence of resistance phenotypes and virulence genes in E. coli isolates from UTI in Kurdistan Province, Iran. The study also shows the relationship between antimicrobial resistance and virulence genes. The increasing emergence of antimicrobial resistance and relationships between resistance and virulence genes suggest that there is a great need for surveillance programs to monitor drug resistance in pathogenic bacteria. Such surveillance programs would provide appropriate guidelines for restriction of antimicrobial use and would be important steps in efforts to understand, prevent, and control the emergence and spread of antimicrobial resistance and virulence genes.
We are grateful to the staff of the microbiology laboratory at Besat and Tohid Hospitals for collecting E. coli isolates used in this study.
Financial support and sponsorship
This study was supported by Faculty of Medicine, Kurdistan University of Medical Sciences, Sanandaj, Iran.
Conflicts of interest
There are no conflicts of interest.
| References|| |
Arisoy M, Rad AY, Akin A, Akar N. Relationship between susceptibility to antimicrobials and virulence factors in paediatric Escherichia coli
isolates. Int J Antimicrob Agents 2008;31 Suppl 1:S4-8.
Kawamura-Sato K, Yoshida R, Shibayama K, Ohta M. Virulence genes, quinolone and fluoroquinolone resistance, and phylogenetic background of uropathogenic Escherichia coli
strains isolated in Japan. Jpn J Infect Dis 2010;63:113-5.
Al-Badr A, Al-Shaikh G. Recurrent urinary tract infections management in women: A review. Sultan Qaboos Univ Med J 2013;13:359-67.
Poey ME, Laviña M. Integrons in uropathogenic Escherichia coli
and their relationship with phylogeny and virulence. Microb Pathog 2014;77:73-7.
Momtaz H, Karimian A, Madani M, Safarpoor Dehkordi F, Ranjbar R, Sarshar M, et al.
Uropathogenic Escherichia coli
in Iran: Serogroup distributions, virulence factors and antimicrobial resistance properties. Ann Clin Microbiol Antimicrob 2013;12:8.
Yun KW, Kim HY, Park HK, Kim W, Lim IS. Virulence factors of uropathogenic Escherichia coli
of urinary tract infections and asymptomatic bacteriuria in children. J Microbiol Immunol Infect 2014;47:455-61.
Lee JH, Subhadra B, Son YJ, Kim DH, Park HS, Kim JM, et al.
Phylogenetic group distributions, virulence factors and antimicrobial resistance properties of uropathogenic Escherichia coli
strains isolated from patients with urinary tract infections in South Korea. Lett Appl Microbiol 2016;62:84-90.
Bien J, Sokolova O, Bozko P. Role of uropathogenic Escherichia coli
virulence factors in development of urinary tract infection and kidney damage. Int J Nephrol 2012;2012:681473.
Jadhav S, Hussain A, Devi S, Kumar A, Parveen S, Gandham N, et al.
Virulence characteristics and genetic affinities of multiple drug resistant uropathogenic Escherichia coli
from a semi urban locality in India. PLoS One 2011;6:e18063.
Tarchouna M, Ferjani A, Ben-Selma W, Boukadida J. Distribution of uropathogenic virulence genes in Escherichia coli
isolated from patients with urinary tract infection. Int J Infect Dis 2013;17:e450-3.
van Belkum A, Goessens W, van der Schee C, Lemmens-den Toom N, Vos MC, Cornelissen J, et al.
Rapid emergence of ciprofloxacin-resistant Enterobacteriaceae containing multiple gentamicin resistance-associated integrons in a Dutch hospital. Emerg Infect Dis 2001;7:862-71.
Odeh R, Kelkar S, Hujer AM, Bonomo RA, Schreckenberger PC, Quinn JP, et al.
Broad resistance due to plasmid-mediated AmpC beta-lactamases in clinical isolates of Escherichia coli
. Clin Infect Dis 2002;35:140-5.
Karaca Y, Coplu N, Gozalan A, Oncul O, Citil BE, Esen B, et al.
Co-trimoxazole and quinolone resistance in Escherichia coli
isolated from urinary tract infections over the last 10 years. Int J Antimicrob Agents 2005;26:75-7.
Da Silva GJ, Mendonça N. Association between antimicrobial resistance and virulence in Escherichia coli
. Virulence 2012;3:18-28.
Johnson JR, Kuskowski MA, Owens K, Gajewski A, Winokur PL. Phylogenetic origin and virulence genotype in relation to resistance to fluoroquinolones and/or extended-spectrum cephalosporins and cephamycins among Escherichia coli
isolates from animals and humans. J Infect Dis 2003;188:759-68.
Moreno E, Prats G, Sabaté M, Pérez T, Johnson JR, Andreu A, et al.
Quinolone, fluoroquinolone and trimethoprim/sulfamethoxazole resistance in relation to virulence determinants and phylogenetic background among uropathogenic Escherichia coli
. J Antimicrob Chemother 2006;57:204-11.
Johnson JR, Kuskowski MA, O'bryan TT, Colodner R, Raz R. Virulence genotype and phylogenetic origin in relation to antibiotic resistance profile among Escherichia coli
urine sample isolates from Israeli women with acute uncomplicated cystitis. Antimicrob Agents Chemother 2005;49:26-31.
Martínez-Martínez L, Fernández F, Perea EJ. Relationship between haemolysis production and resistance to fluoroquinolones among clinical isolates of Escherichia coli
. J Antimicrob Chemother 1999;43:277-9.
Houdouin V, Bonacorsi S, Bidet P, Bingen-Bidois M, Barraud D, Bingen E, et al.
Phylogenetic background and carriage of pathogenicity island-like domains in relation to antibiotic resistance profiles among Escherichia coli
urosepsis isolates. J Antimicrob Chemother 2006;58:748-51.
Turcovský I, Kuniková K, Drahovská H, Kaclíková E. Biochemical and molecular characterization of Cronobacter
spp. (formerly Enterobacter sakazakii) isolated from foods. Antonie Van Leeuwenhoek 2011;99:257-69.
Clinical and Laboratory Standards Institute. Performance Standards for Antimicrobial Susceptibility Testing, 24th
Informational Supplement (M100-S24). Wayne Pa: Clinical and Laboratory Standards Institute; 2014. p. 34.
Derakhshan S, Peerayeh SN, Bakhshi B. Genotyping and characterization of CTX-M-15 -producing Klebsiella pneumoniae
isolated from an Iranian hospital. J Chemother 2016;28:289-96.
Yamamoto S, Terai A, Yuri K, Kurazono H, Takeda Y, Yoshida O, et al.
Detection of urovirulence factors in Escherichia coli
by multiplex polymerase chain reaction. FEMS Immunol Med Microbiol 1995;12:85-90.
Le Bouguenec C, Archambaud M, Labigne A. Rapid and specific detection of the pap
, and sfa
adhesin-encoding operons in uropathogenic Escherichia coli
strains by polymerase chain reaction. J Clin Microbiol 1992;30:1189-93.
Tiba MR, Yano T, Leite Dda S. Genotypic characterization of virulence factors in Escherichia coli
strains from patients with cystitis. Rev Inst Med Trop Sao Paulo 2008;50:255-60.
Asadi S, Kargar M, Solhjoo K, Najafi A, Ghorbani-Dalini S. The association of virulence determinants of uropathogenic Escherichia coli
with antibiotic resistance. Jundishapur J Microbiol 2014;7:e9936.
Oliveira FA, Paludo KS, Arend LN, Farah SM, Pedrosa FO, Souza EM, et al.
Virulence characteristics and antimicrobial susceptibility of uropathogenic Escherichia coli
strains. Genet Mol Res 2011;10:4114-25.
Gupta K, Hooton TM, Stamm WE. Increasing antimicrobial resistance and the management of uncomplicated community-acquired urinary tract infections. Ann Intern Med 2001;135:41-50.
Larson E. Community factors in the development of antibiotic resistance. Annu Rev Public Health 2007;28:435-47.
Cizman M. The use and resistance to antibiotics in the community. Int J Antimicrob Agents 2003;21:297-307.
Leverstein-van Hall MA, Box AT, Blok HE, Paauw A, Fluit AC, Verhoef J, et al.
Evidence of extensive interspecies transfer of integron-mediated antimicrobial resistance genes among multidrug-resistant Enterobacteriaceae in a clinical setting. J Infect Dis 2002;186:49-56.
Barza M, Travers K. Excess infections due to antimicrobial resistance: The “Attributable fraction”. Clin Infect Dis 2002;34 Suppl 3:S126-30.
Stieglitz H, Fonseca R, Olarte J, Kupersztoch-Portnoy YM. Linkage of heat-stable enterotoxin activity and ampicillin resistance in a plasmid isolated from an Escherichia coli
strain of human origin. Infect Immun 1980;30:617-20.
Vila J, Simon K, Ruiz J, Horcajada JP, Velasco M, Barranco M, et al.
Are quinolone-resistant uropathogenic Escherichia coli
less virulent? J Infect Dis 2002;186:1039-42.
Soto SM, Jimenez de Anta MT, Vila J. Quinolones induce partial or total loss of pathogenicity islands in uropathogenic Escherichia coli
by SOS-dependent or – Independent pathways, respectively. Antimicrob Agents Chemother 2006;50:649-53.
Wang XM, Jiang HX, Liao XP, Liu JH, Zhang WJ, Zhang H, et al.
Antimicrobial resistance, virulence genes, and phylogenetic background in Escherichia coli
isolates from diseased pigs. FEMS Microbiol Lett 2010;306:15-21.
[Table 1], [Table 2], [Table 3], [Table 4]