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      Uropathogenic Escherichia coli in Iran: Serogroup distributions, virulence factors and antimicrobial resistance properties

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          Urinary tract infections (UTIs) are one of the most common bacterial infections with global expansion. These infections are predominantly caused by uropathogenic Escherichia coli (UPEC).


          Totally, 123 strains of Escherichia coli isolated from UTIs patients, using bacterial culture method were subjected to polymerase chain reactions for detection of various O- serogroups, some urovirulence factors, antibiotic resistance genes and resistance to 13 different antibiotics.


          According to data, the distribution of O1, O2, O6, O7 and O16 serogroups were 2.43%, besides O22, O75 and O83 serogroups were 1.62%. Furthermore, the distribution of O4, O8, O15, O21 and O25 serogroups were 5.69%, 3.25%, 21.13%, 4.06% and 26.01%, respectively. Overall, the fim virulence gene had the highest (86.17%) while the usp virulence gene had the lowest distributions of virulence genes in UPEC strains isolated from UTIs patients. The vat and sen virulence genes were not detected in any UPEC strains. Totally, aadA1 (52.84%), and qnr (46.34%) were the most prevalent antibiotic resistance genes while the distribution of cat1 (15.44%), cmlA (15.44%) and dfrA1 (21.95%) were the least. Resistance to penicillin (100%) and tetracycline (73.98%) had the highest while resistance to nitrofurantoin (5.69%) and trimethoprim (16.26%) had the lowest frequencies.


          This study indicated that the UPEC strains which harbored the high numbers of virulence and antibiotic resistance genes had the high ability to cause diseases that are resistant to most antibiotics. In the current situation, it seems that the administration of penicillin and tetracycline for the treatment of UTIs is vain.

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          Most cited references 51

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          Virulence factors in Escherichia coli urinary tract infection.

          Uropathogenic strains of Escherichia coli are characterized by the expression of distinctive bacterial properties, products, or structures referred to as virulence factors because they help the organism overcome host defenses and colonize or invade the urinary tract. Virulence factors of recognized importance in the pathogenesis of urinary tract infection (UTI) include adhesins (P fimbriae, certain other mannose-resistant adhesins, and type 1 fimbriae), the aerobactin system, hemolysin, K capsule, and resistance to serum killing. This review summarizes the virtual explosion of information regarding the epidemiology, biochemistry, mechanisms of action, and genetic basis of these urovirulence factors that has occurred in the past decade and identifies areas in need of further study. Virulence factor expression is more common among certain genetically related groups of E. coli which constitute virulent clones within the larger E. coli population. In general, the more virulence factors a strain expresses, the more severe an infection it is able to cause. Certain virulence factors specifically favor the development of pyelonephritis, others favor cystitis, and others favor asymptomatic bacteriuria. The currently defined virulence factors clearly contribute to the virulence of wild-type strains but are usually insufficient in themselves to transform an avirulent organism into a pathogen, demonstrating that other as-yet-undefined virulence properties await discovery. Virulence factor testing is a useful epidemiological and research tool but as yet has no defined clinical role. Immunological and biochemical anti-virulence factor interventions are effective in animal models of UTI and hold promise for the prevention of UTI in humans.
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            Structure and genetics of Shigella O antigens.

            This review covers the O antigens of the 46 serotypes of Shigella, but those of most Shigella flexneri are variants of one basic structure, leaving 34 Shigella distinct O antigens to review, together with their gene clusters. Several of the structures and gene clusters are reported for the first time and this is the first such group for which structures and DNA sequences have been determined for all O antigens. Shigella strains are in effect Escherichia coli with a specific mode of pathogenicity, and 18 of the 34 O antigens are also found in traditional E. coli. Three are very similar to E. coli O antigens and 13 are unique to Shigella strains. The O antigen of Shigella sonnei is quite atypical for E. coli and is thought to have transferred from Plesiomonas. The other 12 O antigens unique to Shigella strains have structures that are typical of E. coli, but there are considerably more anomalies in their gene clusters, probably reflecting recent modification of the structures. Having the complete set of structures and genes opens the way for experimental studies on the role of this diversity in pathogenicity.
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              Increasing prevalence of antimicrobial resistance among uropathogens causing acute uncomplicated cystitis in women.

               Kalpana Gupta (1999)
              Guidelines for the management of acute uncomplicated cystitis in women that recommend empirical therapy in properly selected patients rely on the predictability of the agents causing cystitis and knowledge of their antimicrobial susceptibility patterns. To assess the prevalence of and trends in antimicrobial resistance among uropathogens causing well-defined episodes of acute uncomplicated cystitis in a large population of women. Cross-sectional survey of antimicrobial susceptibilities of urine isolates collected during a 5-year period (January, May, and September 1992-1996). Health maintenance organization. Women aged 18 to 50 years with an outpatient diagnosis of acute cystitis. Proportion of uropathogens demonstrating in vitro resistance to selected antimicrobials; trends in resistance over the 5-year study period. Escherichia coli and Staphylococcus saprophyticus were the most common uropathogens, accounting for 90% of the 4342 urine isolates studied. The prevalence of resistance among E coli and all isolates combined was more than 20% for ampicillin, cephalothin, and sulfamethoxazole in each year studied. The prevalence of resistance to trimethoprim and trimethoprim-sulfamethoxazole rose from more than 9% in 1992 to more than 18% in 1996 among E coli, and from 8% to 16% among all isolates combined. There was a statistically significant increasing linear trend in the prevalence of resistance from 1992 to 1996 among E coli and all isolates combined to ampicillin (P<.002), and to cephalothin, trimethoprim, and trimethoprim-sulfamethoxazole (P<.001). In contrast, the prevalence of resistance to nitrofurantoin, gentamicin, and ciprofloxacin hydrochloride was 0% to 2% among E coli and less than 10% among all isolates combined, and did not change significantly during the 5-year period. While the prevalence of resistance to trimethoprim-sulfamethoxazole, ampicillin, and cephalothin increased significantly among uropathogens causing acute cystitis, resistance to nitrofurantoin and ciprofloxacin remained infrequent. These in vitro susceptibility patterns should be considered along with other factors, such as efficacy, cost, and cost-effectiveness in selecting empirical therapy for acute uncomplicated cystitis in women.

                Author and article information

                Ann Clin Microbiol Antimicrob
                Ann. Clin. Microbiol. Antimicrob
                Annals of Clinical Microbiology and Antimicrobials
                BioMed Central
                29 April 2013
                : 12
                : 8
                [1 ]Department of Microbiology, ShahreKord Branch, Islamic Azad University, P.O. Box: 166, ShahreKord, Iran
                [2 ]Department of Microbiology, Falavarjan Branch, Islamic Azad University, Isfahan, Iran
                [3 ]Graduated of Veterinary Medicine, ShahreKord Branch, Islamic Azad University, ShahreKord, Iran
                [4 ]Molecular Biology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran
                [5 ]Young Researchers club, Jahrom Branch, Islamic Azad University, Jahrom, Iran
                Copyright ©2013 Momtaz et al.; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.



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