Non-typhoidal Salmonella in Calabria, Italy: a laboratory and patient-based survey

INTRODUCTION: Although there has been a decrease in the number of cases of salmonellosis in the European Union, it still represents the primary cause of foodborne outbreaks. In Calabria region, data are lacking for the incidence of human non-typhoid salmonellosis as active surveillance has never been carried out. OBJECTIVE: To report the results of a laboratory and patient-based morbidity survey in Calabria to describe the incidence and distribution of Salmonella serovars isolated from humans, with a focus on antimicrobial resistance patterns. METHODS: Positive cultures from human samples were collected from every laboratory participating in the surveillance, with a minimum set of information about each isolate. A questionnaire was then administered to the patients by telephone interview to assess the potential risk exposures. Salmonella isolates underwent biochemical identification, molecular analysis by PCR and antimicrobial susceptibility testing by the disk-diffusion method. RESULTS: During a 2-year period, 105 strains of Salmonella spp were isolated from samples of patients with diarrhoea, with the highest isolation rate for children aged 1–5 years. The standardised rate was 2.7 cases per 1 00 000 population. The most common Salmonella isolates belonged to monophasic variant of S. Typhimurium (S. 4,[5],12:i:-) (33.3%), followed by S. Typhimurium (21.9%). 30.5% of the isolates were susceptible to all microbial agents tested and the most common pan-susceptible serotype was S. Napoli (100%). S. 4,[5],12:i:- was resistant to ampicillin, streptomycin, sulfonamides and tetracyclines in 42.9% cases, while resistance to quinolones was seen in 14.3% of the isolates. CONCLUSIONS: The results provide evidence that an active surveillance system effectively enhances Salmonella notifications. The high prevalence of antimicrobial resistance, including resistance to quinolones and multiresistance, enforces the need to strengthen strategies of surveillance and monitoring of antimicrobial use.