Evaluation of antibiotic resistance and prevalence of common Salmonella enterica serovars isolated from foodborne outbreaks
Introduction
Foodborne Salmonella enteric infection is the most prevalent cause of gastroenteritis around the world. The Institute for Health Metrics and Evaluation has listed typhoid and paratyphoid enteric infections as among the major causes of communicable diseases with significant global burden. Salmonella infections cause about 1.2 million cases of food poisoning, 23,000 cases of hospitalisation and about 450 deaths every year in the United States, as reported by the Center for Disease Control and Prevention (CDC) [1].
Several studies have been done of corresponding pathogens in foodborne outbreaks or endemic events around the world, and they reported various prevalence rates for different pathogens in different countries but, as it clear, Salmonella enterica spp are the dominant pathogens in these events, and their presence is independent of location, season and the primary health level of a country [2].
Salmonella enterica serovars cause a wide range of infections. They can induce severe gastric symptoms like enterocolitis, enteritis, systemic infection and gastroenteritis [3]. Gastroenteritis is the most frequent manifestation of Salmonella enterica infection, especially in the lower gastrointestinal tract.
Eight to 48 h after the ingestion of contaminated food or water, people suffer nausea, headache, abdominal cramp, vomiting and fever (38–39 °C; 100.5–102.2 °F). Diarrheal stools are usually non-bloody and of moderate volume, but large volumes of watery stools and dysentery may occur. Blood culture results are usually negative, but stool culture results are positive for 4–5 weeks after infection and, in rare cases of chronic carriage (<1%), for >1 year [4].
Salmonella Gastroenteritis is usually a self-limiting disease normally without antibiotic therapy, but two groups require medication including sensitive persons (children, elderlies) and immunocompromised patients such as the HIV-positive, diabetics or rheumatoid arthritis cases. Pre-emptive antibiotic treatment should be considered in these cases.
Treatment of patients with HIV/AIDS and NTS bacteraemia should have 1–2 weeks of IV antibiotic therapy followed by 4 weeks of oral therapy with a fluoroquinolone IV β-lactam antibiotic such as ceftriaxone or ampicillin for the patient's endocarditis or arteritis for 6 weeks, as recommended in Table 1 [5].
The major global problem in antibiotic therapy in gastric and other bacterial infections is antibiotic resistance. Various studies have been done of Salmonella enterica serovars’ antibiotic resistance in order to modify the treatment procedure. Resistance serovars and resistance level are different from country to country based on the available studies, so determination of resistant serovars in different areas is necessary to control infection transmission between and within societies. Primary health services, especially in food safety, are the same in many of regions in the world such as European countries but, in some areas like the Middle East, the coverage and level of food safety programmes is very unbalanced between countries. The incidence of Salmonella foodborne poisoning by more serovars of Salmonella is therefore possible, so the aims of this study are first, the determination of Salmonella serovars in Salmonella-positive patients from food poisoning events; second, the determination of Salmonella prevalence in food poisoning events; third, the determination of the most common transmitter foods; and fourth, the determination of the antibiotic resistance level of isolated Salmonella serovars to compare with other similar studies around the world.
Section snippets
Sample collection and screening
Between 2013 to 2019, a total of 2098 foodborne outbreaks occurred in Iran. 1425 stool samples were screened to detect Salmonella-positive cases by confirmation test (conventional biochemical and serological tests) and labelled as positive samples [6].
Serotyping of positive samples
There was no pre-designed primer for Salmonella paratyphi A, B, C, and senftenberg, so serotyping for these serovars carried out by classical methods and, for other serovars, PCR was performed.
Serotyping of the isolated Salmonella strains was
Results
We found 350 Salmonella-corresponding foodborne outbreaks between 2013 and 2019 in Iran. The 83 Salmonella isolates were collected from 1425 stool samples. 80 Salmonella strains were identified in 7 serovars from these 83 isolates including S. enteritidis,S. typhimurium, S. typhi,S. paratyphi A, B, C and S. senftenberg. A further three strains could not be categorised.
From 80 cases in this study, 46 cases were male and there was no significant difference in incidence rate between male and
Discussion
Despite significant promotion of public health, the Salmonellosis prevalence rate is still high. The morbidity rate resulting from these infections is also still high as CDC reports [1], [11]. Foodborne outbreaks are caused by different Salmonella serovars, whose distribution varies in different regions of the world, leading to differences in the most common serogroup [12], [13], [14], [15], [16], [17]. Major studies around the world, as well as in Iran, have identified S. enteritidis as the
Conclusion
This study showed that S. enteritidis is the main cause of salmonellosis in Iran. No studies have identified Salmonella Senftenberg as one of the common serotypes of food-borne outbreaks, but this serotype was highly prevalent, making this serovar less resistant than was found in other studies. Other serotypes observed in this study were Salmonella paratyphi C (13.8%), which was different from other studies. In a small number of studies, this serotype was isolated from clinical specimens, while
CRediT authorship contribution statement
Zahra Rahimi Nadi: Investigation, Writing - original draft. Taghi Zahraei Salehi: Methodology. Iradj Ashrafi Tamai: Resources. Abbas Rahimi Foroushani: Formal analysis. Mika Sillanpaa: Writing - review & editing. Mohammad Mehdi Soltan Dallal: Project administration, Supervision.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgement
This work was supported by Vice-Chancellor for Research grant (no. 41388) of Tehran University of Medical Sciences (Tehran, Iran).
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