Detection and characterization of Shigella species isolated from food and human stool samples in Nabeul, Tunisia, by molecular methods and culture techniques

• Published in: Journal of applied microbiology Vol. 113; no. 1; pp. 209 - 222
• Main Authors: Mokhtari, W, Nsaibia, S, Majouri, D, Ben Hassen, A, Gharbi, A, Aouni, M
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-07-2012; Blackwell; Oxford University Press
• Subjects: antibiotic resistance; autumn; Bacteria; Bacteriological Techniques - methods; Biological and medical sciences; diagnostic techniques; Diarrhea - epidemiology; Diarrhea - microbiology; disease outbreaks; DNA primers; DNA, Bacterial - genetics; Drug Resistance, Multiple, Bacterial; Dysentery, Bacillary - epidemiology; Dysentery, Bacillary - microbiology; Electrophoresis, Gel, Pulsed-Field; Feces; Feces - microbiology; Female; food; food contamination; Food contamination & poisoning; Food Contamination - analysis; food handling; Food Microbiology - methods; Foodborne Diseases - epidemiology; Foodborne Diseases - microbiology; foodborne illness; foods; Fundamental and applied biological sciences. Psychology; genes; human faeces; Humans; in vitro culture; ipaH; Male; Meat - microbiology; Microbial Sensitivity Tests; Microbiology; molecular biology; patients; PCR; Polymerase Chain Reaction; public health; pulsed-field gel electrophoresis; Seafood - microbiology; seasonal variation; Seasons; serotypes; Shigella; Shigella - genetics; Shigella - isolation & purification; Shigella - pathogenicity; Shigella sonnei; Shigella spp; signs and symptoms (animals and humans); summer; Tunisia - epidemiology; Vegetables - microbiology; virulence; Virulence - genetics; virulence gene; virulent strains; Tunisia; Human; Applied microbiology; Sample; Virulence; Foodstuff; food; Characterization; Polymerase chain reaction; Shigella spp; Pulsed field electrophoresis; Analysis method; Gene; virulence gene; Bacteria; pulsed-field gel electrophoresis; Feces; Technique; human faeces; Detection; Culture; Shigella; PCR; Enterobacteriaceae; ipaH
• ISSN: 1364-5072; 1365-2672
• DOI: 10.1111/j.1365-2672.2012.05324.x

Aims: This study was designed to isolate Shigella spp. strains from food and stool samples by a combination of PCR and culture methods and characterize their serotypes, antibiotic resistance profiles, virulence genes and pulsed‐field gel electrophoresis (PFGE) patterns to investigate possible clonal relationships amongst strains circulating. Methods and Results: Six Shigella spp. strains were isolated from 280 food samples against 16 Shigella isolates from 236 stool samples of symptomatic patients and asymptomatic food handlers during the period from January 2007 to December 2009 in Public Health Regional Laboratory of Nabeul. The detection of ipaH, ipaBCD, ial, ShET‐1 and ShET‐2 was performed by a PCR technique with specific primers. Conclusions: The use of PCR technique improved the rate of detecting Shigella in stool samples from 6·7 to 14% and in food samples from 2·1 to 8·6%. Percentage of Shigella isolates and ipaH‐specific PCR demonstrated a marked pattern of seasonality, increasing in summer and fall seasons for human and food isolates. Amongst the environmental strains, 50% of isolates were invasive. However, for the 16 clinical strains isolated, nine were found to be positive for both ial and ipaBCD gene and 11 were found to produce ShET‐1 and/or ShET‐2. XbaI PFGE analysis revealed the presence of a predominant clone amongst Shigella sonnei strains recovered from different sources circulating in Nabeul, Tunisia, throughout the years 2007–2009. Significance and Impact of the Study: This study demonstrated the existence of Shigella in food samples and dispersion of different virulence genes amongst these isolates, which appear to constitute an environmental source of epidemic spread. The clonal relationships amongst strains isolated from food elements and human stools indicate the incrimination of different kinds of foods as vehicle of transmission of Shigella, which are usually escaped from detection by traditional culture methods.