Occurrence and distribution of Salmonella serovars in carcasses and foods in southern Italy: Eleven-year monitoring (2011-2021)

Antibiotic-Resistant Salmonella Circulation in the Human Population in Campania Region (2010-2023)

Background/Objectives: A retrospective study was conducted to evaluate antibiotic resistance among Salmonella strains isolated during human infection using data from the computer database (SIGLA) of the Salmonella Typing Center (Ce.Ti.Sa) of the Istituto Zooprofilattico del Mezzogiorno (IZSM). Methods: From 2010 to 2023, the Ce.Ti.Sa laboratory tested 680 Salmonella strains against the following: amoxicillin/clavulanic acid, ampicillin, azithromycin, cefixime, cefoxitin, cefotaxime, ceftazidime, chloramphenicol, ciprofloxacin, colistin, erythromycin, gentamicin, kanamycin, meropenem, nalidixic acid, pefloxacin, streptomycin, sulfisoxazole, sulfonamides, tetracyclines, tigecycline, and trimethoprim. Results: The most common serovars were S. monophasic Typhimurium (23.2%), S. Enteritidis (16.8%), and S. Typhimurium (16.0%). Nearly all strains were resistant to azithromycin (99.4%) and showed high resistance to sulphonamides, tetracycline, streptomycin, and ampicillin. The study found that 45.8% of strains exhibited multidrug resistance. Resistance to ciprofloxacin increased over time. Serovar-specific resistance varied: S. monophasic Typhimurium was resistant to azithromycin (100.0%), tetracycline (93.0%), and ampicillin (92.4%); S. Enteritidis showed 100.0% resistance to azithromycin; S. Typhimurium had high resistance to azithromycin, streptomycin, and ampicillin; and S. Infantis was resistant to erythromycin, sulfonamides, and azithromycin. Conclusions: The study highlights a troubling prevalence of Salmonella-resistant strains, emphasizing the need for infection prevention, proper antibiotic use in humans and animals, and the development of new antibiotics.

Evaluation of multi-drug resistance, virulence factors, and antimicrobial resistance genes of non-typhoidal Salmonella isolated from ruminants as a potential human health threat in Razavi Khorasan, northeastern Iran

Non-typhoidal Salmonella (NTS) is a significant foodborne pathogen that poses a threat to human health by causing infections and potentially acquiring antibiotic resistance. We evaluated thirty-five Salmonella serovars previously isolated from cattle, sheep, goats, and their retail meat in Razavi Khorasan Province, Iran. The isolates were confirmed with Salmonella polyvalent antiserum. Furthermore, PCR was used to identify the Salmonella Enteritidis, Salmonella Typhimurium, and the host-adapted serovars Salmonella Dublin and Salmonella Abortusovis. Additionally, the antimicrobial susceptibility of the serovars was evaluated using the disk diffusion method. Subsequently, the occurrence of antimicrobial resistance genes and virulence factors was evaluated using the PCR technique. Molecular typing revealed that 20 % of the isolates were S. Typhimurium, 11.4 % were S. Dublin, 8.6 % were S. Enteritidis, 5.7 % were S. Abortusovis, and 54.3 % (19 isolates) were classified as non-typed serovars. Salmonella isolates showed high susceptibility to ciprofloxacin (91.4 %), colistin (88.6 %), gentamicin (88.6 %), and cefotaxime (85.7 %) while exhibiting high resistance to others such as ampicillin (88.6 %), streptomycin (74.3 %), and tetracycline (51.4 %). The most prevalent resistance genes in non-typhoidal Salmonella (NTS) are blaTEM (91.4 %), sul1 (65.7 %), and aadA (54.3 %). Additionally, twenty-five isolates (71.4 %) showed multi-drug resistance profiles. The most frequent virulence genes are stn (100 %), iroN (100 %), and pefA (42.9 %). The current study has revealed that Salmonella serovars isolated from sheep and goats, like those from cattle, exhibit multi-drug resistance and harbor antimicrobial resistance genes. Additionally, they possess diverse virulence factors that can threaten human health by spreading diseases and developing drug resistance, leading to antibiotic treatment failure.

Combatting Salmonella: a focus on antimicrobial resistance and the need for effective vaccination

BACKGROUND

Salmonella infections represent a major global public health concern due to their widespread zoonotic transmission, antimicrobial resistance, and associated morbidity and mortality. This review aimed to summarize the zoonotic nature of Salmonella, the challenges posed by antimicrobial resistance, the global burden of infections, and the need for effective vaccination strategies to mitigate the rising threat of Salmonella.

METHODS

A systematic review of literature was conducted using databases such as PubMed, Scopus, Web of Science, and Google Scholar. Relevant studies published in English were identified using keywords including Salmonella, vaccination, antimicrobial resistance, and public health. Articles focusing on epidemiology, vaccine development, and strategies to control Salmonella infections were included, while conference abstracts and non-peer-reviewed studies were excluded.

RESULTS

Salmonella infections result in approximately 95 million global cases annually, with an estimated 150,000 deaths. Regional variations were evident, with higher infection rates in low- and middle-income countries due to poor sanitation and food safety standards. Salmonella Enteritidis and S. Typhimurium were the most prevalent serovars associated with human infections. The review highlighted an alarming rise in multidrug-resistant (MDR) Salmonella strains, particularly due to the overuse of antibiotics in humans and livestock. Despite progress in vaccine development, challenges remain in achieving a universal vaccine that targets diverse Salmonella serovars. Live-attenuated, killed, recombinant, subunit, and conjugate vaccines are currently under development, but limitations such as efficacy, cost, and accessibility persist.

CONCLUSIONS

Salmonella infections continue to impose a significant burden on global health, exacerbated by rising antimicrobial resistance. There is an urgent need for a multifaceted approach, including improved sanitation, prudent antibiotic use, and the development of affordable, broad-spectrum vaccines. Strengthening surveillance systems and promoting collaborative global efforts are essential to effectively control and reduce the burden of Salmonella.

Prevalence of Non-typhoidal Salmonellae in the Retail Chicken Meat in Alexandria, Egypt

The objective of this study was to evaluate the extent of Salmonella contamination in retail chicken carcasses within Alexandria, Egypt, while also identifying the specific serotypes present. The research addresses the scarcity of comprehensive data concerning Salmonella distribution and its phenotypic attributes in chicken meat across the Alexandria Governorate. A total of sixty raw chicken carcass samples were randomly acquired from six different markets in Alexandria. Detection of Salmonella spp. was conducted based on standard culture techniques, biochemical analyses, and serological tests. The results revealed an overall occurrence of 33.3% in Salmonella contamination. The most prevalent serotypes were S. typhimurium and S. kentucky. Among the sampled chicken carcass components, the liver and gizzard exhibited the highest contamination rates at 60% each, followed by the neck at 50%, and the wing at 30%. Conversely, no traces of Salmonella were detected in the heart and small intestine samples. This absence could be attributed to the administration of antibiotics in poultry feeds at the farm level. Analysis of various markets highlighted differing contamination rates; Asafra, Alabrahimih, and Mansheya registered the highest rates at 60%, 40%, and 40% respectively. In contrast, Borg El Arab and Amriya experienced lower rates with both displaying a 30% contamination level. Intriguingly, a supermarket within Alexandria showed no presence of Salmonella spp. The study underscores substantial carcass contamination during the market handling phase, emphasizing the need for intervention strategies from relevant stakeholders to mitigate these contamination impacts.

Salmonella enterica Serovar Infantis in Broiler Chickens: A Systematic Review and Meta-Analysis

Salmonella enterica subsp. enterica serovar Infantis poses a growing threat to public health, due to its increasing prevalence worldwide and its association with high levels of antimicrobial resistance. Among livestock, S. Infantis is especially isolated from broilers. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a systematic review was conducted by searching in three databases (Web of Science, Scopus, and PubMed) for English-language studies (1957-2023) that reported the prevalence of S. Infantis in broiler farms. Eligible studies included epidemiological investigations conducted in broiler chickens by sampling the house environment (flock-level prevalence) or the birds (individual-level prevalence). A random-effect model was applied to calculate S. Infantis pooled prevalence estimates with 95% confidence intervals (CIs). Furthermore, to assess between-study heterogeneity, the inconsistency index statistic (I2) was calculated. Among 537 studies retrieved, a total of 9 studies reporting flock-level prevalence of S. Infantis and 4 reporting individual-level prevalence were retained for analysis. The flock-level pooled prevalence was estimated to be 9% (95% CI: 1-26%) and a high between-study heterogeneity was found (I2 = 99%, p < 0.01). Concerning individual-level prevalence, a meta-analysis was not performed due to the scarcity of eligible studies. The data presented underscore the significant occurrence of S. Infantis in broilers at the farm level. By summarizing the existing literature, this work provides useful insights for conducting future surveys of Salmonella spp. in live broiler chickens as a preliminary step for developing more efficient control strategies.

Exploring resource competition by protective lactic acid bacteria cultures to control Salmonella in food: an Achilles' heel to target?

Salmonella is a pathogenic bacterium, being the second most commonly reported foodborne pathogen in Europe, due to the ability of its different serovars to contaminate a wide variety of foods, with differences among countries. Common chemical or physical control methods are not always effective, eco-sustainable and adapted to the diversity of Salmonella serovars. Thus, great attention is given to developing complementary or alternative control methods that can be tailor made for specific situations. One of these methods is biopreservation using lactic acid bacteria, with most studies on their antagonistic activity focused on the production of antimicrobials. Less attention has been given to competition by exploitation of nutrients. This review is thus set to investigate and highlight limiting resources that may be involved in the competitive exclusion of Salmonella in food matrices. To do this the needs for nutrients and microelements and the known homeostatic pathways of Salmonella and lactic acid bacteria are examined. Finally, milk, intended for the manufacture of fermented dairy foods, is pointed out as an example of food to investigate the bioavailable macronutrients, metals and vitamins that could be involved in competition between the different species and serovars, and could be exploited for targeted biopreservation.

Prevalence, serovars, and risk factors associated with the presence of Salmonella in pork sold in public markets in Quito, Ecuador

Background

Salmonella enterica are bacteria that include more than 2,500 serovars. Most of these serovars have been linked to human foodborne illnesses, mainly related to poultry and pigs. Thus, these animals are considered the reservoirs of many Salmonella serovars and strains related to antibiotic resistance. This study aimed to determine the prevalence, serovars, β-lactam resistance genes, and the risk factors associated with Salmonella enterica in pork commercialized in open markets of Quito city.

Methods

For this, 165 pork meat samples were taken from municipal markets in three areas in the city. These samples were microbiologically processed following the ISO 6579-2014 standardized method. The polymerase chain reaction (PCR) test was used to identify Salmonella serotyping and resistance genes. Strains not identified by PCR were typed by the Kauffman White Le Minor scheme. A multivariate analysis was performed to identify risk factors associated with the presence of the microorganism.

Results

Salmonella prevalence in pork was 9.1%. Identified serovars were 4, [5], 12: i:- (53.3%), Infantis (33.3%), and Derby (13.4%). Furthermore, the β-lactam resistance genes bla CTX-M-65 could be identified in three S. infantis isolates. Multivariate analysis showed that temperature (above 8°C) and cutting surfaces (wood) presented significant association values.

Conclusions

In conclusion, pork in traditional markets of Quito is contaminated with Salmonella enterica, whose main serovars pose a public health concern, and shows beta-lactam resistance.

Detection of Salmonella Reservoirs in Birds of Prey Hosted in an Italian Wildlife Centre: Molecular and Antimicrobial Resistance Characterisation

In the European Union, salmonellosis is one of the most important zoonoses reported. Poultry meat and egg products are the most common food matrices associated with Salmonella presence. Moreover, wild and domestic animals could represent an important reservoir that could favour the direct and indirect transmission of pathogens to humans. Salmonella spp. can infect carnivorous or omnivorous wild birds that regularly ingest food and water exposed to faecal contamination. Birds kept in captivity can act as reservoirs of Salmonella spp. following ingestion of infected prey or feed. In this paper, we describe the isolation of different Salmonella serovars in several species of raptors hosted in aviaries in an Italian wildlife centre and in the raw chicken necks used as their feed but intended for human consumption. Characterisations of strains were carried out by integrating classical methods and whole genome sequencing analysis. The strains of S. bredeney isolated in poultry meat and birds belonged to the same cluster, with some of them being multidrug-resistant (MDR) and carrying the Col(pHAD28) plasmid-borne qnrB19 (fluoro)quinolone resistance gene, thus confirming the source of infection. Differently, the S. infantis found in feed and raptors were all MDR, carried a plasmid of emerging S. infantis (pESI)-like plasmid and belonged to different clusters, possibly suggesting a long-lasting infection or the presence of additional undetected sources. Due to the high risk of fuelling a reservoir of human pathogens, the control and treatment of feed for captive species are crucial.

Prevalence and Antimicrobial Resistance Diversity of Salmonella Isolates in Jiaxing City, China

Nontyphoidal Salmonella (NTS) is a cause of foodborne diarrheal diseases worldwide. Important emerging NTS serotypes that have spread as multidrug-resistant high-risk clones include S. Typhimurium monophasic variant and S. Kentucky. In this study, we isolated Salmonella in 5019 stool samples collected from patients with clinical diarrhea and 484 food samples. Antibiotic susceptibility testing and whole-genome sequencing were performed on positive strains. The detection rates of Salmonella among patients with diarrhea and food samples were 4.0% (200/5019) and 3.1% (15/484), respectively. These 215 Salmonella isolates comprised five main serotypes, namely S. Typhimurium monophasic variant, S. Typhimurium, S. London, S. Enteritidis, and S. Rissen, and were mainly resistant to ampicillin, tetracycline, chloramphenicol, and trimethoprim/sulfamethoxazole. The MDR rates of five major serotypes were 77.4%, 56.0%, 66.7%, 53.3%, and 80.0%, respectively. The most commonly acquired extended-spectrum β-lactamase-encoding genes were blaTEM-1B, blaOXA-10, and blaCTX-M-65. The S. Typhimurium monophasic variant strains from Jiaxing City belonged to a unique clone with broad antibiotic resistance. S. Kentucky isolates showed the highest drug resistance, and all were MDR strains. The discovery of high antibiotic resistance rates in this common foodborne pathogen is a growing concern; therefore, ongoing surveillance is crucial to effectively monitor this pathogen.

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.

Isolation and Characterisation of Human-Derived blaKPC-3-Producing Salmonella enterica Serovar Rissen in 2018

In this study, we describe a Salmonella enterica serovar (S.) Rissen strain with a reduced susceptibility to meropenem, isolated from a urinary infection in an 89-year-old woman in 2018 during activity surveillance in Italy (Enter-Net Italia). The genomic characteristics, pathogenicity, and antimicrobial resistance mechanisms were investigated via a genomic approach. Antimicrobial susceptibility testing revealed a "susceptible, increased exposure" phenotype to meropenem in the S. Rissen strain (4_29_19). Whole-genome sequencing (WGS) was performed using both the NovaSeq 6000 S4 PE150 XP platform (Illumina, San Diego, CA, USA) and MinION (Oxford Nanopore). The S. Rissen 4_29_19 strain harboured two plasmids: a pKpQIL-like plasmid carrying the blaKPC-3 resistance gene in a Tn4401a transposon (pKPC_4_29_19), and a ColE-like plasmid (p4_4_29_19) without resistance genes, highly prevalent among Enterobacterales. Comparative analysis revealed that the pKPC_4_29_19 plasmid was highly related to the pKpQIL reference plasmid (GU595196), with 57% coverage and 99.96% identity, but lacking a region of about 30 kb, involving the FIIK2 replicon region and the entire transfer locus, causing the loss of its ability to conjugate. To our knowledge, this is the first time that a pKpQIL-like plasmid, carrying blaKPC-3, highly diffused in Klebsiella pneumoniae strains, has been identified in a Salmonella strain in our country. The acquisition of blaKPC genes by Salmonella spp. is extremely rare, and is reported only sporadically. In zoonotic bacteria isolated from humans, the presence of a carbapenem resistance gene carried by mobile genetic elements, usually described in healthcare-associated infection bacteria, represents an important concern for public health.

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.

Surveillance of Human Cases of Salmonellosis, Campylobacteriosis, Listeriosis, and Hepatitis A in Campania (Southern Italy): Seven-Year Monitoring (2013-2019)

Foodborne infections cause illness and death every year worldwide. The aim of this study was to describe trends in 2013-2019 in the occurrence of human cases of salmonellosis, campylobacteriosis, listeriosis, and hepatitis A in the Campania region. Human case data were provided by the National Surveillance System of disease and were grouped by year, province, age group, and sex. Moreover, the number of people hospitalized was recorded. In the Campania region, the total number of confirmed human cases for the diseases investigated was 1924, with Hepatitis A and the Salmonellosis as the first most reported (1009 and 825 cases, respectively). The incidence rates of gastroenteritis under study were lower than those in Italy and European Union in the same period, with the exception of Hepatitis A whose incidence was higher than that recorded in Italy. Data on hospitalizations pointed out the onset of severe forms of infection also for listeriosis and campylobacteriosis, whose incidence was very low (27 and 63 cases, respectively). Unfortunately, no information on the foods implicated is available. Although probably underestimated, gastroenteritis due to foodborne agents still represents a burden in Campania, and continuous monitoring and implementation of the currently available regional surveillance system is required.