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Updated: Jul 10, 2025
Quasi-metagenomic Analysis of Salmonella from Food and Environmental Samples
Published on: October 25, 2018
Invasive and Non-Invasive Human Salmonellosis Cases Admitted between 2015 and 2021 in Four Suburban Hospitals in the
Gabriele Pagani1, Marco Parenti2, Marco Franzetti1
1UOC Malattie Infettive, ASST Ovest-Milanese, Ospedale Nuovo di Legnano, Via Papa Giovanni II s.n., Legnano, 20025 Milano, Italy.
Abstract:
Non-Typhoidal Salmonellas (NTSs) are diffused worldwide. In Italy, more than 3500 cases are notified each year, but despite this, data about salmonellosis are scarce. Our multi-center, retrospective, descriptive study selected 252 patients with positive cultures for Salmonella spp. (feces 79.8%, blood 8.7%, feces and blood 7.5%), aiming to describe the epidemiological and clinical characteristics of this population. Bacteremic infections constituted 16.3% (41/252) of patients. Extreme ages (≤12 and ≥65 years old) accounted for 79.7%, but only elder ages were strongly associated with bacteremic infections (aOR 5.78). Invasive infections had a 7-fold higher mortality rate than non-invasive disease (9.8% vs. 1.4%, p = 0.013), with an overall rate of 2.8%. The two more represented serogroups were O:4 (52.8%) and O:9 (22.2%). The O:9 serogroup was strongly associated with a higher frequency of invasive infection (aOR 2.96, 95% CI 1.17-7.63). In particular, S. napoli, an emerging serovar in Europe, accounted for 31.7% of bacteremic infections and only 9.5% of non-bacteremic ones (p < 0.001). Antibiotic microbial resistance (AMR) observed a steep increasing trend and was detected in 60.4% of cases (122/202): amoxicillin/clavulanate, ampicillin, and gentamicin were most commonly involved (26.7%, 21.8%, 14.3%, respectively), while TMP/SMX, ciprofloxacin, and ceftriaxone were <10%. Resistance was, in general, less common in the O:9 serogroup, while amikacin resistance was significantly more common. Factors associated with an MDR Salmonella acquisition were time (OR 1.37 per year more), O:4 serogroup (OR 2.67), and being a woman (OR 2.11). The most frequent symptoms were diarrhea (90.5%) and fever (81.7%). In conclusion, our study highlights a high burden of NTS infections, leading to severe or fatal outcomes in frail patients. Furthermore, AMR shows an increasing trend with a concerning high prevalence of cephalosporine resistance compared to the rest of Europe.
Insights
Non-Typhoidal Salmonella (NTS) infections are a significant health concern, particularly in Italy, with elderly patients facing higher risks of severe outcomes. Antibiotic resistance is a growing problem, demanding urgent attention to treatment strategies.
Area of Science:
- * Infectious Diseases
- * Microbiology
- * Epidemiology
Background:
- * Non-Typhoidal Salmonella (NTS) infections are prevalent globally, with over 3500 cases annually in Italy, yet detailed data remain scarce.
- * Salmonellosis poses a significant public health challenge, necessitating a deeper understanding of its epidemiological and clinical aspects.
Purpose of the Study:
- * To describe the epidemiological and clinical characteristics of 252 patients with Salmonella spp. infections in Italy.
- * To identify risk factors for invasive infections and antibiotic resistance in Salmonella.
Main Methods:
- * Multi-center, retrospective, descriptive study of patients with positive Salmonella cultures.
- * Analysis of patient demographics, clinical presentation, serogroups, and antimicrobial resistance patterns.
Main Results:
- * Elderly patients (≥65 years) had a significantly higher risk of bacteremic infections (aOR 5.78) and mortality (9.8% vs. 1.4%).
- * Serogroup O:9 was associated with invasive infections (aOR 2.96), and *S. napoli* was prominent in bacteremic cases.
- * Antibiotic microbial resistance (AMR) was high (60.4%), with increasing trends and concerning cephalosporin resistance.
Conclusions:
- * NTS infections represent a substantial burden, causing severe outcomes in vulnerable populations, especially the elderly.
- * Emerging serovars like *S. napoli* and increasing AMR, particularly cephalosporin resistance, require enhanced surveillance and antimicrobial stewardship.
