---

Background&Objective: Shiga-toxin producing E. coli (STEC) belonging to several different O serotypes are one of the etiological agent of diarrhea. The STEC strains are considered as an etiological agent for enteritis after non-typhoidal salmonellosis and Campylobacter. They have also been associated closely with the hemolytic uremic syndrome (HUS) and hemorrhagic colitis(HC). The aim of this study was to determine of the frequency of STEC in patients with hemorrhagic colitis referring to Tehran hospitals. Materials&Methods: From March to September 2004, 70 patients with hemorrhagic colitis (Case)an 70 patients with diarrhea (Control) were included in this study. The stx gene was detected by PCR and was used for the determination of STEC strains. Slide agglutination with specific antisera used to detect O serogroup. Polymerase chain reaction- restriction fragment length polymorphism (PCR-RFLP) analysis of the flagellin gene (fliC) was performed for determining their flagellar antigen (H). Results: Two samples (2.9%) from Hemorrhagic colitis cases and 12 samples (17.1 %) from diarrheal cases were positive for STEC. There was no significant correlation between STEC and Hemorrhagic colitis but there was a significant correlation between STEC and diarrhea (p<0.05). STEC isolates O142:H48 serotype was from hemorrhagic colitis cases and O126:H47, O126:H6, O26:H4 and O111:H23 serotypes were from diarrheal cases. These serotypes were not reported in hemorrhagic colitis cases. Conclusion: Our data showed that there was no significant correlation between STEC and hemorrhagic colitis. This could be explained since serotype responsible for hemorrhagic colitis i.e. O157:H7 serotype is not present in Iran.

---

Background and Objective: Listeria monocytogenes is an important food-borne intracellular pathogen which can transmit to human through contaminated foods and causing meningitis, meningoencephalitis and abortion. This study was done to determine the frequency, antimicrobial susceptibility and serotyping of Listeria monocytogenes isolated from food samples in Tehran, Iran.
Methods: This descriptive was carried on 150 food samples including vegetables, cheese and meat were collected from supermarkets, open-air markets, and delicatessens in different regions of Tehran, Iran since April to September 2018. The presumptive isolates were characterized biochemically. All L. monocytogenes isolates were further analyzed by serotyping and antimicrobial susceptibility tests.
Results: Out of 150 samples, Listeria spp. was detected in 30 (20%) samples in which 9 (6%) were positive for L. monocytogenes [vegetables (n=4, 44.44%), cheese (n=2, 22.22%) and meat (n=3, 33.33%)]. of the 9 L. monocytogenes isolates, 5 (55.55 %), 3 (33.33 %), and 1 (11.11%) belonged to serotypes 4b, 1/2b, and 1/2a, respectively. The most L. monocytogenes isolates were resistant to Trimetoprime, Sulfamethoxazole, Tetracycline, Streptomycin, Chloramphenicol, and Ciprofloxacin while were sensitive to Penicillin G, Gentamicin, Streptomycin, and Ampicillin, and were intermediately resistant to Ciprofloxacin.
Conclusion: The rate of Contamination of vegetable, cheese and meat samples with L. monocytogenes is important in Tehran, Iran. Due to the potential contamination samples to Listeria, there is necessity need for continuous monitoring and the development of a precise program for identifying this bacterium in Tehran and the whole country.