Association of tcdA[+]/tcdB[+] clostridium difficile genotype with emergence of multidrug-resistant strains conferring metronidazole resistant phenotype

Reduced susceptibility of Clostridium difficile to antibiotics is problematic in clinical settings. There is new evidence indicating the cotransfer of toxin-encoding genes and conjugative transposons encoding resistance to antibiotics among different C. difficile strains. To analyze this association, in the current study, we evaluated the frequency of toxigenic C. difficile among the strains with different multidrug-resistant [MDR] profiles in Iran. Antimicrobial susceptibility patterns and minimal inhibitory concentrations [MIC] of the isolates were determined against metronidazole, imipenem, ceftazidime, amikacin, and ciprofloxacin by agar dilution method. The association of the resistance profiles and toxigenicity of the strains were studied by PCR targeting tcdA and tcdB genes. Among 86 characterized strains, the highest and lowest resistance rates were related to ciprofloxacin [97%] and metronidazole [5%], respectively. The frequency of resistance to other antibiotics was as follow: imipenem [48%], ceftazidime [76%], and amikacin [76.5%]. Among the resistant strains, double drug resistance and MDR phenotypes were detected in the frequencies of 10.4% and 66.2%, respectively. All of the metronidazole-resistant strains belonged to tcdA [+]/tcdB[+] genotype with triple or quintuple drug resistance phenotypes. MIC[50] and MIC[90] for this antibiotic was equally

Isolation of Enteropathogenic Escherichia coli from lettuce samples in Tehran

Aim: The purpose of this study was to find the isolation rate of enteropathogenic Escherichia coli [EPEC] from lettuce samples collected in Tehran

Background: During the last decade, the prevalence of infectious diarrheal diseases due to consumption of contaminated food especially raw vegetable has been increasingly reported. Enteropathogenic Escherichia coli strains are an important group of diarrheagenic E. coli that can cause infant diarrhea especially in the developing world

Material and Methods: One hundred lettuce samples collected in Tehran were transported to the laboratory, homogenized by a stomacher in EC broth containing cefixime, and cultured on MacConkey agar plates. Bacterial DNA was extracted by boiling method and PCR was performed using three pairs of primers targeting stx1, stx2 and eaeA genes

Results: Screening of 100 lettuce samples by PCR showed four samples were positive for the presence of EPEC

Conclusion: This study suggests contamination of the lettuce by the EPEC and its possible role as the source of infection in this region

Determination of adhesion virulence factors of enteropathogenic escherichia coli [eaeA,bfpA] isolates from asymptomatic individuals compared to those with diarrhea

The aim of the this study was to investigate the prevalence of toxB, paa, Ipf and iha adhesion genes in enteropathogenic Escherichia coli [EPEC] isolates lacking in two important adhesion factors, the eaeA and bfpA genes. We examined a total of 70 serologically confirmed EPEC [eaeA, bfpA] isolates. DNA from the isolates was extracted by the phenol-chloroform method. toxB, paa, Ipf and iha adhesion genes in the EPEC isolates were detected by polymerase chain reaction. Data were analyzed by SPSS software and statistical analysis using the chi square test. P-values less than 0.05 were considered significant. PCR was positive for the toxB gene in 2 [2.85%], paa in 3 [4.28%], Ipf in 32 [45.71%] and iha in 15 [21.42%] of the 70 strains. Statistically, none of the toxB.paa, and Ipf genes were associated with diarrhea. However, the iha gene showed a weak significant relation to diarrhea [P=0.11]. The main mechanism of pathogenicity for EPEC is attachment and effacement. Therefore, EPEC [eaeA, bfpA] should have another adhesin factor, which should be investigated. EPEC strains [eaeA-, bfpA-] that possess the Ipf gene are common. Further investigations of the virulence properties of these strains are necessary in order to elucidate the role of these virulence factors in diarrhea among Iranian children

Prevalence and antibiotic resistance patterns of diarrheagenic Escherichia coli isolated from adolescents and adults in Hamedan, Western Iran

Pathogenic strains of Escherichia coli are a common cause of acute infectious diarrhea. The aim of this study was to investigate the frequency, virulence markers and antibiotic resistance patterns of diarrheagenic E. coli [DEC] isolated from adolescents and adults in Hamadan, west of Iran. A total of 187 stool samples were collected from adults with acute diarrhea. Stool culture was performed by conventional methods for enteropathogenic bacteria. Virulence factor genes for DEC were detected by polymerase chain reaction. Antimicrobial susceptibility was tested using the disk diffusion method. Among the 187 patients, 40 [21.4%] were positive for DEC. The most frequently identified DEC was enteropathogenic E. coli [47.5%], followed by enteroaggregative [20%], enterotoxigenic [17.5%] and shiga-toxin producing E. coli [15%]. No isolates of enteroinvasive E. coli were detected. All STEC strains were stx[+] / eaeA[-]. Out of the seven ETEC strains, five [71.4%] produced ST, one [14.3%] produced only LT and one [14.3%] of the isolates produced both ST and LT encoded by est and elt genes, respectively. Among the 40 DEC strains 27[67.5%] were multidrug resistant. DEC contribute to the burden of diarrhea in adults in Hamadan. Enteropathogenic E. coli was the most commonly identified DEC strain in the region studied

Enteroaggregative Escherichia coli, a heterogenous, underestimated and under-diagnosed E. coli pathotype in Iran

The main features of enteroaggregative Escherichia coli [EAEC] pathogenesis include attachment of bacteria to the intestinal mucosa, production of various toxins and cytotoxins, and stimulation of mucosal inflammation. 'Virulence' genes encode these features. Comparison of different EAEC isolates has shown that the virulence gene content of these isolates varies considerably. The heterogeneity of EAEC strains was concluded from the results obtained from the volunteer as well as other studies. Although the underlying mechanism behind the apparent increase in O104:H4 virulence is not known, several bacterial factors have been implicated. In this review, the known virulence factors involved in pathogenesis of EAEC pathotype are summarized

Ribotyping of EPEC isolates from diarrheal and asymptomatic patients in Iran

We intended to find out the diversity of EPEC isolates among asymptomatic or diarrheal children in Iran using ribotyping. Enteropathogenic Escherichia coli [EPEC] is responsible for gastroenteritis especially in young children. A total of 39 EPEC collected strains were serotyped and the presence of virulence genes as well as EAF plasmid among the strains was studied. Adherence assay was also performed. Clonal diversity of the isolates was investigated using ribotyping. Of 39 studied strains of E. coli, 6 serogroups of EPEC were represented. The presence of the stx gene was ascertained in 7 isolates and the eaeA, eaeB and bfpA genes were harbored by 5, 3 and 1 strains, respectively. Ribotyping yielded 9 different clusters. According to our results there was not a significant correlation between the results of serotyping and those of ribotyping. However, different serotypes of E. coli may belong to the same ribotype clusters and vice versa

[Study of antibiotic susceptibility pattern and presence of ipaH gene among shigella strains isolated from selected provinces in Iran]

Shigellosis is one of the most common causes of morbidity and mortality in children with diarrhea in developing countries. It is essential to assess the antibiotic resistance patterns of these bacteria. ipaH gene is one of the virulence factors which can be used for detection of Shigella spp. Total of 100 isolates of Shigella were collected from different provinces of Iran. This isolates were characterized by biochemical tests and serological tests using polyclonal antisera for 4 species of S. dysenteriae, S. sonnei, S. boydii and S. flexneri. Antibiotic susceptibility assay for 14 different antibiotics was carried out using agar disc diffusion method. Presence of ipaH gene was investigated by PCR using specific primers. From the results of this study the Shigella isolates were classified as follows: 36 [%73] Shigella sonnei, 9 [%18] Shigella flexneri, 3 [%5] Shigella boydii, 2 [%4] Shigella dysenteriae. Approximately%50 of the Shigella isolates were resistant to Tetracycline and Cotrimoxazole. Shigella sonnei showed more resistance than other serotypes against the studied antibiotics. PCR assays showed that all isolates harbored ipaH gene. The results showed that prevalence of Shigella sonnei is higher than other serotypes. The isolates showed high sensitivity to third generation cephalosporines and aminoglycosides. PCR detection of ipaH gene as a reliable marker for identification of Shigella species could be recommended

[Molecular detection and identification of virulence factors of Pseudomonas aeruginosa isolated from wound and burn infections]

In recent decades, Pseudomonas aeruginosa has emerged as one of the most important nosocomial pathogens. Due to the clinical importance this bacterium, various methods have been developed to rapidly and accurately identify it. The aim of this research was to detect P. aeruginosa isolated from wound and burn infections on the basis of the amplification of the oprl, oprL and toxA genes, and to determine the prevalence of nanl and exoS genes among them. A total of 150 P. aeruginosa isolates was collected from patients with burn and wound infections of Imam-Khomaini, Tohid and Motahari hospitals in Tehran. The isolates were identified as P. aeruginosa using specific biochemical tests. Chromosomal DNA of the isolates was extracted with phenol chloroform method and used for PCR of oprl, oprL, toxA, exoS and nanl genes by specific primers. Among 150 P. aeruginosa isolates all carried the oprl and oprL genes; 98 [65.3%] 142 [94.7%] and 19 [12.66%] of the isolates were positive for exoS, toxA and nanl genes respectively. The presence of nanl gene in wound isolates [30%] was significantly higher [p<0.05] than in burn isolates [4%].Our results indicated that simultaneous use of oprl, oprL and toxA genes provide sufficient sensitivity to detect P. aeruginosa in clinical samples. The high prevalence of exoS in isolates suggests invasive phenotype of wound and burn isolates. The high prevalence of nanl in wound isolates suggests a possible role of this gene in those infections

Antibiotic susceptibility profile of Helicobacter pylori isolated from the dyspepsia patients in Tehran, Iran

Helicobacter pylori is an important pathogen for gastroduodenal diseases. Infection with H. pylori can be limited by regimens of multiple antimicrobial agents. However, antibiotic resistance is a leading cause of treatment failure. The aim of this study has been to determine the resistance patterns of H. pylori strains isolated from gastric biopsies of patients with dyspepsia by agar dilution method, in Tehran, Iran. H. pylori isolates from patients with gastrointestinal diseases were evaluated for susceptibility testing by agar dilution method. Susceptibility testing was performed to commonly used antibiotics including clarithromycin, tetracycline, amoxicillin, metronidazole and ciprofloxacin. Among 92 patients with dyspepsia, H. pylori strains were isolated from 42 patients. Seventeen [40.5%] of the isolates were resistant to metronidazole [MICs >/= 8 microg/1], whereas one isolate [2.4%] was resistant to amoxicillin [MICs

Genetic diversity and drug resistance of helicobacter pylori strains in Isfahan, Iran

Resistance to antimicrobial agents, particularly metronidazole and clarithromycin, is frequently observed in Helicobacter pylori and may be associated with treatment failure. This resistance rate varies according to the population studied. The aim of this study was to assess the pattern of antimicrobial resistance of H. pylori isolates from dyspeptic patients in Isfahan. Antral gastric biopsies from 230 dyspeptic patients were cultured. Susceptibility testing to commonly used antibiotics performed on pure cultures of 80 H. pylori-positive isolates by Modified Disk Diffusion Method [MDDM]. Genomic DNA extracted and subjected for study of entire genomic pattern using Random Amplified Polymorphic DNA- Polymerase Chain Reaction [RAPD-PCR]. The overall rates of primary resistance were 30.0%, 8.75%, 6.25%, 3.75%, 3.75%, and 2.50% for metronidazole, ciprofloxacin, clarithromycin, azithromycin, tetracycline, and amoxicillin, respectively. Multiple antibiotic resistances were observed in 8 of 27 resistant isolates [29.6%] that mainly were double resistance with the prevalence of 6.25%. No association between antimicrobial resistance and either the gender, age or clinical presentation of the patients were detected. In RAPD-PCR, great diversity observed in 27 resistant strains isolated from different patients and this heterogeneity was not significantly different from susceptible strains. Primary H, pylori resistance to metronidazole in our population was lower than the developing world and even other parts of Iran, to ciprofloxacin was considerable in comparison with results in most other countries. Moreover, antibiotic resistance had no effect on genomic pattern of H. pylori isolates. Finally, pretreatment H. pylori isolates susceptibility testing is highly recommended

Characterization and distribution of virulence factors in aeromonas hydrophila strains isolated from fecal samples of diarrheal and asympotmatic healthy persons, in Ilam, Iran

Aeromonas hydrophila secretes several extracellular proteins including enterotoxin, hemolysin and aerolysin that are associated with the bacterial virulence. Previous studies have shown that two hemolytic toxins, hemolysin A and aerolysin A contribute to the virulence of Aeromonas hydrophila. In the current study, a total of 50 strains of Aeromonas hydrophila, including 28 [56%] strains isolated from diarrheal cases and 22 [44%] strains isolated from healthy asymptomatic controls, were used. These strains were tested for cytochrome oxidase activity based on Kovac's method and confirmed as A. hydrophila with API 20E multi-test systems. To determine hemolysin, cytotoxin and enterotoxin activities, horse blood agar, Vero cells and the suckling mouse model were used, respectively. The presence of two hemolytic toxin genes: hlyA and aerA was determined by PCR assay. About 89% of diarrheal strains tested were positive for hemolysins, 68% for cytotoxin and 89% for enterotoxin activity. These figures for healthy asymptomatic isolates were 72%, 23% and 14%, respectively. A significant association was found between cytotoxin and enterotoxin activity in diarrheal disease, whereas such association was not found in case of hemolysin. Almost 93% of diarrheal isolates and 73% of healthy person strains were PCR positive for hly A gene. The corresponding figures for aerA gene were 86% and 45.5% respectively. The aerA + hlyA + genotype and in some cases aerA + genotype could be considered as reasonable predictors of human diarrheal disease. However, the role of other unknown hemolytic and cytolytic factors cannot be discounted