Occurrence and distribution of Salmonella serovars associated with human infection isolated from irrigation waters and food-producing animals in southern Italy: eleven-year monitoring (2011-2021).

Salmonella is one of the main zoonotic agents causing foodborne diseases in Europe. The main reservoirs of the infection are represented by domestic and wild animals, and the infection occurs by direct contact or following the consumption of contaminated food or water. The study aimed to evaluate the presence of Salmonella spp. in food-producing animals and irrigation waters in southern Italy and the serovar distribution. From 2011 to 2021, a total of 473 samples from 6 different animal species (bovine, buffalo, goat, ovine, swine, poultry, and wild boars) and 313 irrigation water samples were collected and analyzed. The overall percentage of positive samples was 56.87% in organs, 50.85% in feces, and 20.45% in irrigation waters. By animal species, the most frequently detected serovar was Salmonella Typhimurium in bovine (17.39%), in buffalo (13.10%) and swine (28.21%), and S. Kentucky (24.78%) in poultry. The subspecies diarizonaeIIIb was frequently detected in goats (40.00%) and ovine (83.33%), while salamaeII (14.12%) and diarizonaeIIIb (11.76%) were frequently isolated in wild boars. In the irrigation water samples, the most frequently detected serovar was S. Napoli (25%). Results revealed that, although in Europe, control strategies aimed at preventing the spread of Salmonella have been implemented, the prevalence of this pathogen in food-producing animals and irrigation waters is high. Considering the risk to public health associated with the contamination of products or foods, more stringent control interventions are needed at primary production and along the food chain.

Antimicrobial Resistance and Genomic Characterization of Salmonella Infantis from Different Sources.

The epidemiology of Salmonella Infantis is complex in terms of its distribution and transmission. The continuous collection and analysis of updated data on the prevalence and antimicrobic resistance are essential. The present work aimed to investigate the antimicrobial resistance and the correlation among S. Infantis isolates from different sources through the multiple-locus variable-number of tandem repeat (VNTR) analysis (MLVA). A total of 562 Salmonella strains isolated from 2018 to 2020 from poultry, humans, swine, water buffalo, mussels, cattle, and wild boar were serotyped, and 185 S. Infantis strains (32.92%) were identified. S. Infantis was commonly isolated in poultry and, to a lesser extent, in other sources. The isolates were tested against 12 antimicrobials, and a high prevalence of resistant strains was recorded. S. Infantis showed high resistance against fluoroquinolones, ampicillin, and tetracycline, which are commonly used in human and veterinary medicine. From all S. Infantis isolates, five VNTR loci were amplified. The use of MLVA was not sufficient to understand the complexity of the epidemiological relationships between S. Infantis strains. In conclusion, an alternative methodology to investigate genetic similarities and differences among S. Infantis strains is needed.

Identification of a New Serovar of Salmonella enterica in Mediterranean Buffalo Calves (Bubalus bubalis).

This case report describes for the first-time cases of severe gastroenteritis in water buffalo calves due to a new serovar of Salmonella enterica. The study was carried out on fecal matrix collected from live water buffalo calves that showed profuse diarrhea, severe dehydration and fever, exhibiting a systemic course. Culture and molecular investigations identified the pathogens isolated from intestinal contents as two Salmonella serovars, Salmonella enterica enterica O:35 and a new serovar of Salmonella enterica. The isolates showed multi-drug resistance. Timely diagnosis associated with a targeted antimicrobial treatment were found to be sufficient for the survival and recovery of the infected animals. Herd vaccines prepared from isolated pathogens were used to prevent further deaths of the calves.

Serotyping and Evaluation of Antimicrobial Resistance of Salmonella Strains Detected in Wildlife and Natural Environments in Southern Italy.

Wild animals are potential vectors of antibiotic-resistant bacteria in the environment. The present study aimed to investigate the occurrence of antimicrobial resistance among Salmonella serovars isolated from wildlife and the environment in Italy. A total of 164 Salmonella isolates were analyzed, and six different subspecies and 64 serovars were detected. High proportions of Salmonella isolates proved resistant to streptomycin (34.1%), followed by trimethoprim-sulfamethoxazole (23.2%), tetracycline (17.7%), ciprofloxacin (14.63%) and ampicillin (11.59%). By source, the lowest level of resistance was observed in Salmonella serovars isolated from a water environment, while antimicrobial resistance was frequent in strains collected from shellfish, reptiles and birds. Multidrug-resistant strains were recovered from seafood (n = 11), mammals (n = 3) and water (n = 1). Three S. Typhimurium monophasic variant strains showed asimultaneous resistance to ampicillin, streptomycin, tetracycline and trimethoprim-sulfamethoxazole, which represents a recognized alert resistance profile for this serovar. These data indicate the environmental dissemination of resistant strains due to anthropogenic activities, which, in southern Italy, probably have a higher impact on marine ecosystems than on terrestrial ones. Moreover, as most of the animals considered in the present study are usually consumed by humans, the presence of resistant bacteria in them is a matter of great concern.

Occurrence and antimicrobial resistance of Salmonella strains from food of animal origin in southern Italy.

Six hundred fourteen strains of Salmonella enterica were isolated from 16,926 samples of food of animal origin collected in southern Italy from 2003 to 2012. The isolates were identified, serotyped, and challenged against 15 antibiotics according to the protocol defined at national level for veterinary isolates of Salmonella (EnterVet surveillance network). Salmonella serotypes Typhimurium, Hadar, Enteritidis, Derby, and 4,[5],12:i:- were those most frequently isolated. The widest resistances were recorded towards sulfonamides (69 % of the isolates), trimethoprim-sulfamethoxazole (52 % of the isolates), and tetracycline (51 % of the isolates). The rate of multidrug resistance of the isolates decreased significantly from the first 5 years of the study period (82.6 %) to the last 5 years (54.3 %).