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

Abstract

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.

Prevalence of Shigella species and Antimicrobial Resistance Patterns of Isolated Strains from Infected Pediatrics in Tehran

“…Initially, Shigella invades (by virulence plasmid) the large intestine epithelium (8,13). Invasive strains arrive to epithelial cells which follows intracellular proliferation, intra-and intercellular spreading, and finally cause host cell death (14,15).…”

“…are generally believed to have only a human or primate host. Primarily, shigellosis is transmitted from person to person through the fecal-oral route, but it may also spread indirectly by fecal contamination of water or food (8,9). Many individuals who are infected with Shigella expand fever, painful bloody or mucous diarrhea, and stomach cramps (3,10).…”

<i>Shigella</i> Serogroups, Entro-Hemoragic <i>E. coli</i> and Their Antibiogram Pattern Among Food Handlers in Food-Handling Establishments in Southern Ethiopia

“…Shigellosis, an acute invasive enteric infection caused by Shigella species, is also recognized as a major public health problem [5]. It is transmitted either through the feces of an infected person or through food or water contaminated by an infected person, with as few as 10 to 100 organisms capable of causing infection [6].…”

Molecular Detection of Shigella spp. Contamination in Ready-to-Eat Salad Samples in West of Tehran

“…11 In the other research from these authors, 2% (4 out of 197) of salad samples were positive based on routine culturebased methods while PCR results showed the presence of ipaH gene in 8.6% (24 out of 280) of food samples including salad. 12 Finally, there was no positive sample in evaluation of 100 ready-to-eat salads in a culture-based survey carried out in Turkey by Cetinkaya et al 13 The high percentage of the positive samples and rate of contamination with Shigella in this research may be due to poor education and personal hygiene of people involved in the production and distribution of pre-packed salads and probably contaminated water sources for irrigation of the farms and because the human body is the only natural host of Shigella spp. This strengthen the hypothesis of the pollution of the water sources by sewage.…”