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Saudi Journal of Kidney Diseases and Transplantation
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RENAL DATA FROM THE ASIA - AFRICA  
Year : 2011  |  Volume : 22  |  Issue : 3  |  Page : 597-601
The prevalence of O serogroups of Escherichia coli strains causing acute urinary tract infection in children in Iran


1 Pediatric Department, Jahrom University of Medical Sciences, Jahrom, Iran
2 Prof. Alborzi Clinical Microbiology Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
3 Laboratory of Motahary Hospital, Jahrom University of Medical Sciences, Jahrom, Iran
4 Laboratory of Peymanieh Hospital, Jahrom University of Medical Sciences, Jahrom, Iran

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Date of Web Publication7-May-2011
 

   Abstract 

The aim of present study was to determine the prevalence of O serogroups of Escherichia coli (E. coli) strains that cause community-acquired urinary tract infections (UTI) in children. In this study, 96 children with UTI referred to two Jahrom University-affiliated Hospitals in Iran were enrolled, during the period from August 2005 to August 2006. Drug sensitivity was tested by disk diffusion method and serotyping done by slide agglutination method. A total of 96 E. coli strains were isolated from urine samples of the study children whose age ranged from one month to 14 years. Cystitis was diagnosed in 49.2% and pyelonephritis in 50.8% of the study patients. Maximum drug resistance was seen with ampicilin (80.2%) and the least with imipenem (1.1%). The most common type of O antigen was O1 (12.2%). There was significant correlation between the presence of O antigens and sensitivity to nalidixic acid and gentamicin (P < 0.05). This is the first report of E. coli serotyping in children with UTI from the south of Iran and their relation to antibiotic resistance and clinical presentation. Further studies from other parts of Iran and on other serotypes are recommended.

How to cite this article:
Emamghorashi F, Farshad S, Kalani M, Rajabi S, Hoseini M. The prevalence of O serogroups of Escherichia coli strains causing acute urinary tract infection in children in Iran. Saudi J Kidney Dis Transpl 2011;22:597-601

How to cite this URL:
Emamghorashi F, Farshad S, Kalani M, Rajabi S, Hoseini M. The prevalence of O serogroups of Escherichia coli strains causing acute urinary tract infection in children in Iran. Saudi J Kidney Dis Transpl [serial online] 2011 [cited 2019 Nov 19];22:597-601. Available from: http://www.sjkdt.org/text.asp?2011/22/3/597/80511

   Introduction Top


Urinary tract infection (UTI) is one of the most common infections and  Escherichia More Details coli (E. coli) is the most common causative agent, [1] accounting-for as much as 90% of all UTIs seen among ambulatory patients. [2] O antigen is a liposaccharide present in the bacterial cell wall.

E. coli strains were classified based on the various types of O antigen for the first time by Kauffmann; [3] 164 types of O antigen have been detected till now. [4] These days, E. coli strains are generally named based on the serotypes O and H (e.g., O1H3). Each serotype of E. coli has an important role in clinical presentation of UTI, and the prevalence of different serotypes varies in different regions. In Iran, despite the high prevalence of UTI, very few studies have been conducted to determine the prevalence of various serotypes of E. coli. The aim of this study was to determine the prevalence of O serogroups of E. coli strains that cause community acquired UTI in children.


   Materials and Methods Top


Patients

In this study, children with UTI, referred to two university-affiliated teaching hospitals (referral hospitals) in Jahrom, Iran, during the period between August 2005 and August 2006, were enrolled. The study group included outpatients as well as in-patients. The diagnosis of UTI was established by the hospital medical staff based on clinical symptoms and positive urine culture. The methods selected for urine sampling were based on age of the patients and their cooperation, and included use of urine bag and mid-stream urine collection. Acute pyelonephritis was clinically defined as the presence of fever (temperature >38.5°C) and/ or costo-vertebral angle tenderness, and in neonates it was defined as the presence of hypothermia or hyperthermia, lethargy and poor feeding without any other causes. Cystitis was considered when dysuria and pyuria were present without fever. Data including age, sex, previous history of infection, recent antibiotic usage and history of hospitalization during the last 28 days were collected for all patients with community-acquired UTIs, using the questionnaire form. The patients with nosocomial infection, which was defined as infection noted after 48 hours following admission or within four weeks after a previous discharge, were excluded from the study.

Bacterial isolation

The E. coli strains were isolated from urine samples and identified using standard methods. [5] The strains were then stored and sub-cultured for further analysis by standard methods.

Susceptibility test

Susceptibility of all isolates to different anti-biotics was determined using the disk diffusion method as recommended by the National Committee for Clinical Laboratory Standards, [6] with commercial anti-microbial disks (Mast. Co., UK). The antibiotic disks used in this study were ampicilin, nalidixic acid, cefixime, gentamicin, nitrofurantoin, ciprofloxacin, amikacin and imipenem. E. coli ATCC 25922 was used for quality control purposes.

Serotyping

Slide agglutination was performed according to the manufacturer's guidelines for the kit. At the beginning, heat-treated suspension of the organism was prepared and labeled as antigen suspension; two loop full of this suspension were placed on a microscopic slide. One drop of antiserum was placed on one drop of suspension and one drop of normal saline was placed on the other, which served as control. The reagents were mixed by titling back and forth for 60 seconds while viewing it under indirect light against a dark background. Distinct clumping or agglutination within this pe-riod, along with absence of clumping in the saline control, was regarded as positive result.

We had limitation for testing all types of O antigen; hence, based on literature review, four of the more common O types of uropathogenic E. coli were selected and tested. They were types O1, O6, O15 and O18.


   Statistical Analysis Top


Statistical analysis was performed using SPSS software for Windows, version 11.5. Descriptive analyses were done for parametric and non-parametric variables. Chi-square test was used for evaluation of correlation between anti-biotic resistant patterns, sonography findings and site of infection with serotypes. Relationship between age of the patients and serotypes was analyzed by Student's "t" test. P value less than 0.05 was considered significant.


   Results Top


Antibiotic susceptibility

Totally, 96 strains of E. coli were isolated from urine samples of children with UTI, aged one month to 14 years (mean 21.8 ± 26.9 months). The female to male ratio was 1.9, with 65.2% of the patients being females. Cystitis was diagnosed in 49.2% and pyelonephritis in 50.8% of these patients.

Drug sensitivities of the isolates were as follows: 19.8% to ampicilin, 75.5% to nalidixic acid, 80.4% to cefixime, 84.6% to gentamycin, 91.4% to ciprofloxacin, 96.8% to nitrofurantoin and 96.8% to amikacin [Figure 1]. Resistance to imipenem was less than 1.2%. Multiple drug resistance to ampicilin, gentamicin, nalidixic acid and cefixime was seen in 2.1% of the isolates, but no case of multiple drug resistance to all drugs was seen. Only 12.5% of the strains were susceptible to all tested antibiotics.
Figure 1: Antibiotic sensitivity of E. coli strains isolated from children with urinary tract infection.

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Bacterial strains

A total of 26 samples were positive for one of the types of O antigens that were tested (27%). The most common type of O antigen was O1 (12.2%), followed by O6 (10.2%) and O15 (4.1%). We did not encounter any case positive for O18.

There was significant correlation between the presence of the O antigens and sensitivity to nalidixic acid and gentamicin [Table 1]. All the 26 O antigen-positive cases were sensitive to gentamicin (P=0.006) and 25 O antigen-positive cases were sensitive to nalidixic acid (P = 0.002). There was no correlation between multiple drug resistance and O antigen type. There was no significant correlation between the presence of O antigen and the site of infection (lower or upper), abnormal finding on renal sonography and age of the patients.
Table 1: Relation between O antigen and antibiotic sensitivity in the study patients.

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   Discussion Top


We studied limited types of O antigen in UTI-isolated E. coli strains. Totally, 26 samples were positive for one type of O antigen (27%), with the most common of them being O1 (12.2%). E. coli strains were classified based on various types of O antigen for the first time by Kauffmann; [3] 164 types of O antigen have been detected till now. [4] Various studies have been conducted in other centers for serotyping of uropathogenic E. coli. One of the earliest studies was conducted by Orskov and co-workers in 1982. Their study on O, K and H serotype determination of 267 E. coli strains in patients with pyelonephritis or cystitis led them to consider some O, K and H types, for example, O6:K2:H1 as pyelonephritis-associated types and O6:K13:H1 as cystitis-associated types. In that study, O6 was commonly seen in patients with both pyelonephritis or cystitis. [7] Johnson studied the relationship between bacterial characteristics and clinical source of E. coli. One of the predictors of cystitis and/or pyelonephritis was O75 antigen. [8] In our present study, there was no significant correlation between cystitis and/or pyelonephritis and the type of O antigen.

In Rio de Janeiro, 40 E. coli isolates were tested between 1999 and 2004, and O6 was the most common type found. [9] In a study by Blanco and co-workers, most uropathogenic E. coli belonged to 10 (O1, O2, O4, O6, O7, O14, O18, O22, O75 and O83) of the 12 serogroups. [10] Serotype O101 was found to be the commonest serotype (7/26) of uropathogenic E. coli causing UTI in two studies from India. [11],[12] In 1994, Blanco examined 96 E. coli strains isolated from cultures of blood specimens taken from both urosepsis patients and non-urosepsis patients; 56 (58%) belonged to one of the eight serogroups (O1, O2, O4, O6, O8, O9, O18 and O83). [13] Although serotype O6 was the most common type found in many studies, in our present study, O1 was the most common type, while O6 was a common sero-type in E. coli strains isolated from children with UTI in Slovakia. [14] In a study of community-acquired UTI in Santiago, the uropathogenic strains of E. coli characterized belonged to 27 different O serogroups; 68% were from one of ten serogroups (O1, O2, O4, O6, O9, O18, O27, O73, O75 and O77) and 36% were from one of three serogroups (O2, O4 and O6). [15]

In the present study, no correlation was seen between type of O antigen and antibiotic resistance. The majority of seropositive cases were sensitive to all antibiotics except ampicilin. Few other studies have been conducted for evaluation of the correlation between antibiotic resistance and O antigen expression. [16],[17] One of the earliest studies was conducted in 1975. The researchers showed that resistant E. coli were associated with O-antigen types 8, 9 and 101, while the susceptible strains covered a wide range of O-antigen types. [17] We were unable to prepare antiserum for serotype O101, and due to this limitation, we restricted our study to evaluate more common serotypes (O1, O6, O15 and O18). This is the first report of E. coli serotyping in children with UTI from south of Iran and their relation to antibiotic resistance and clinical presentation. O1 (12.2%) and O6 (10.2%) were two common types that correlated with anti-biotic sensitivity.


   Acknowledgment Top


This study was supported by Jahrom University of Medical Sciences. The authors wish to thank Mr. Jalil Nasiri for his technical assistance in isolation and genotyping of the strains.

 
   References Top

1.Gruneberg RN. Antibiotic sensitivities of urinary pathogens, 1971-1982. J Antimicrob Chemother 1984;14:17-23.  Back to cited text no. 1
    
2.Kunin CM. Urinary tract infections: detection, prevention, and management. 5th ed. Baltimore, Md: Williams & Wilkins; 1997.  Back to cited text no. 2
    
3.Kauffmann F. Ueber neue themolabile Korper-antigene der colibakterien. Acta Pathol Microbiol Scand 1943;20:21-44.  Back to cited text no. 3
    
4.Kauffmann F. Zur serologie coli Gruppe. Acta Pathol Microbiol Scand 1944;21:21-45.  Back to cited text no. 4
    
5.Farmer JJ. Enterobacteriaceae: introduction and identification. Manual of clinical microbiology. 7th ed. Washington: ASM Press; 1999.  Back to cited text no. 5
    
6.National Committee for Clinical Laboratory Standards. (2000). Performance standards for antimicrobial susceptibility testing. Eighth informational supplement. Approved Standard M2-A7. National Committee for Clinical Laboratory Standards, Villanova, Pa. Procedure guidelines in Mast pathogenic Escherichia coli O antiserum brochure in kit package.  Back to cited text no. 6
    
7.Orskov F, Birch-Andersen AO. Fimbrial antigens in Escherichia coli serotypes associated with pyelonephritis and cystitis. Scand J Infect Dis Suppl 1982;33:18-25.  Back to cited text no. 7
    
8.Johnson JR, Owens K, Gajewski A, et al. Bacterial characteristics in relation to clinical source of Escherichia coli isolates from women with acute cystitis or pyelonephritis and uninfected women. J Clin Microbiol 2005;43(12): 6064-72.  Back to cited text no. 8
    
9.Esparis CM, Teixeira LM, Irino K, et al. Biological and molecular characteristics of uro-pathogenic Escherichia coli strains isolated in the city of Rio de Janeiro. Rev Soc Bras Med Trop 2006;39(6):573-6.  Back to cited text no. 9
    
10.Blanco M, Blanco JE, Alonso MP, et al. Virulence factors and O groups of Escherichia coli isolates from patients with acute pyelonephritis, cystitis and asymptomatic bacteriuria. Eur J Epidemiol 1996;12(2):191-8.  Back to cited text no. 10
    
11.Mandal P, Kapil A, Goswami K, et al. Uro-pathogenic Escherichia coli causing urinary tract infections. Indian J Med Res 2001;114: 207-11.  Back to cited text no. 11
    
12.Srikanth NS, Macaden R. Uropathogenic Escherichia coli-a preliminary study. Indian J Pathol Microbiol 2003;46(1):145-6.  Back to cited text no. 12
    
13.Blanco M, Blanco JE, Alonso MP. Virulence factors and O groups of Escherichia coli strains isolated from cultures of blood specimens from urosepsis and non-urosepsis patients. Microbiologia 1994;10(3):249-56.  Back to cited text no. 13
    
14.Siegfried L, Kmetova M, Puzova H, et al. Virulence-associated factors in Escherichia coli strains isolated from children with urinary tract infections. J Med Microbiol 1994;41(2): 127-32.  Back to cited text no. 14
    
15.Blanco M, Blanco J, Blanco JE, et al. Viru-lence factors and 0 serogroups of Escherichia coli as a cause of community-acquired urinary infections. Enferm Infect Microbiol Clin 1995; 13(4):236-41.  Back to cited text no. 15
    
16.Hartley CL, Howe K, Linton AH, et al. Distribution of R Plasmids Among the O-Antigen Types of Escherichia coli Isolated from Human and Animal Sources. Antimicrob Agents Chemother 1975;8(2):122-31.  Back to cited text no. 16
    
17.Tarr PI, Clausen CR, Whittam TS, et al. Anti-biotic resistance and O antigen expression in Escherichia coli. J Infect Dis 1998;177(6): 1774-5.  Back to cited text no. 17
    

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Correspondence Address:
Fatemeh Emamghorashi
Pediatric Department, Jahrom University of Medical Sciences, Jahrom
Iran
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