Prevalence and antimicrobial resistance of salmonellae isolated from eggs of local chicken in selected towns of Ethiopia.

BACKGROUND: Salmonellosis is one of the most common food-borne diseases in industrialised and developing countries. In recent year, an increase in antimicrobial resistance among different Salmonella serotypes has been observed. OBJECTIVE: A cross-sectional study was conducted to assess the prevalence and antimicrobial susceptibility of Salmonella isolated from local chicken eggs in four selected towns in Ethiopia. METHODS: A total of 115 eggs were examined to detect Salmonella by using standard microbiological methods. The susceptibilities of the isolates to nine antimicrobials were tested by the Kirby-Bauer disk diffusion method. RESULT: The study revealed that of the 115 eggs examined, 22 (19.1%) were positive for Salmonella of which 14 (12.2%) and 8 (7%) of the isolates were from shells and contents, respectively. The occurrence of Salmonella in egg shells and content and between different altitudes did not differ significantly (p > 0.05). Most isolates were resistant to more than three antimicrobials with a high resistance to kanamycin, ampicillin, nalidixic acid, cotrimoxazole, oxytetracycline and chloramphenicol. CONCLUSION: The results indicate the potential importance of local chicken eggs as source of multiple antimicrobial-resistant salmonellae and the need for proper cooking before consumption. Further studies are required to describe the epidemiology of Salmonella in various agroclimatic zones of Ethiopia.

Characterization of Salmonella species from poultry slaughterhouses in South Korea: carry-over transmission of Salmonella Thompson ST292 in slaughtering process.

IMPORTANCE: Salmonella outbreaks linked to poultry meat have been reported continuously worldwide. Therefore, Salmonella contamination of poultry meats in slaughterhouses is one of the critical control points for reducing disease outbreaks in humans. OBJECTIVE: This study examined the carry-over contamination of Salmonella species through the entire slaughtering process in South Korea. METHODS: From 2018 to 2019, 1,097 samples were collected from the nine slaughterhouses distributed nationwide. One hundred and seventeen isolates of Salmonella species were identified using the invA gene-specific polymerase chain reaction, as described previously. The serotype, phylogeny, and antimicrobial resistance of isolates were examined. RESULTS: Among the 117 isolates, 93 were serotyped into Salmonella Mbandaka (n = 36 isolates, 30.8%), Salmonella Thompson (n = 33, 28.2%), and Salmonella Infantis (n = 24, 20.5%). Interestingly, allelic profiling showed that all S. Mbandaka isolates belonged to the lineage of the sequence type (ST) 413, whereas all S. Thompson isolates were ST292. Moreover, almost all S. Thompson isolates (97.0%, 32/33 isolates) belonging to ST292 were multidrug-resistant and possessed the major virulence genes whose products are required for full virulence. Both serotypes were distributed widely throughout the slaughtering process. Pulsed-field gel electrophoretic analysis demonstrated that seven S. Infantis showed 100% identities in their phylogenetic relatedness, indicating that they were sequentially transmitted along the slaughtering processes. CONCLUSIONS AND RELEVANCE: This study provides more evidence of the carry-over transmission of Salmonella species during the slaughtering processes. ST292 S. Thompson is a potential pathogenic clone of Salmonella species possibly associated with foodborne outbreaks in South Korea.

Development of a decision support tool to compare diagnostic strategies for establishing the herd status for infectious diseases: An example with Salmonella Dublin infection in dairies.

The diagnosis of infectious diseases at herd level can be challenging as different stakeholders can have conflicting priorities. The current study proposes a "proof of concept" of an approach that considers a reasonable number of criteria to rank plausible diagnostic strategies using multi-criteria decision analysis (MCDA) methods. The example of Salmonella Dublin diagnostic in Québec dairy herds is presented according to two epidemiological contexts: (i) in herds with no history of S. Dublin infection and absence of clinical signs, (ii) in herds with a previous history of infection, but absence of clinical signs at the moment of testing. Multiple multiparty exchanges were conducted to determine: 1) stakeholders' groups; 2) the decision problem; 3) solutions to the problem (options) or diagnostic strategies to be ordered; 4) criteria and indicators; 5) criteria weights; 6) the construction of a performance matrix for each option; 7) the multi-criteria analyses using the visual preference ranking organization method for enrichment of evaluations approach; 8) the sensitivity analyses, and 9) the final decision. A total of nine people from four Québec's organizations (the dairy producers provincial association along with the DHI company, the ministry of agriculture, the association of veterinary practitioners, and experts in epidemiology) composed the MCDA team. The decision problem was "What is the optimal diagnostic strategy for establishing the status of a dairy herd for S. Dublin infection when there are no clinical signs of infection?". Fourteen diagnostic strategies composed of the three following parameters were considered: 1) biological samples (bulk tank milk or blood from 10 heifers aged over three months); 2) sampling frequencies (one to three samples collection visits); 3) case definitions to conclude to a positive status using imperfect milk- or blood-ELISA tests. The top-ranking diagnostic strategy was the same in the two contexts: testing the bulk tank milk and the blood samples, all samples collected during one visit and the herd being assigned a S. Dublin positive status if one sample is ELISA-positive. The final decision favored the top-ranking option for both contexts. This MCDA approach and its application to S. Dublin infection in dairy herds allowed a consensual, rational, and transparent ranking of feasible diagnostic strategies while taking into account the diagnostic tests accuracy, socio-economic, logistic, and perception considerations of the key actors in the dairy industry. This promising tool can be applied to other infectious diseases that lack a well-established diagnostic procedure to define a herd status.

Investigation of prevalence and antimicrobial resistance of Salmonella in pet dogs and cats in Turkey.

BACKGROUND: Although salmonellosis is considered to be a foodborne zoonotic disease, pets can play a significant role in the dissemination of antimicrobial-resistant Salmonella organisms to humans because of close contact with their owners. OBJECTIVES: To determine the prevalence, risk factors, virulence factors, serotypes, and antimicrobial resistance profile of Salmonella in pet dogs and cats in Turkey and to assess the public health risk. Furthermore, to perform macroscopic comparison of lactic acid bacteria (LAB) in Salmonella-positive and Salmonella-negative animals. METHODS: International Standards Organization (ISO) 6579-1:2017 and Food and Drug Administration (FDA) methods were used to compare the effectiveness of culture methods in the identification of Salmonella in 348 rectal swabs. Positive isolates were serotyped using the slide agglutination method according to the White-Kauffmann-Le Minor scheme and the presence of virulence genes (invA and stn) were evaluated by polymerase chain reaction (PCR). Antimicrobial activity was tested by Kirby-Bauer disk diffusion method according to Clinical and Laboratory Standards Institute (CLSI) guidelines. RESULTS: Salmonella prevalence was 5.73% (9/157) in dogs and 0.0% (0/191) in cats. Eight (8/9) isolates were cultured with the ISO method and 5 (5/9) isolates were cultured with the FDA method. Macroscopic results revealed that Salmonella agents had no effect on LAB. Three different serotypes were detected and all isolates were positive for virulence genes. Antibiotic resistance profiling indicated that 11.1% of the isolates were MDR and the highest resistance was found for ciprofloxacin. MDR-resistant S. Virchow and carbapenem-resistant S. Enteritidis were detected from dog isolates. There was a significant difference between raw meat consumption and Salmonella carriage (p < 0.01). CONCLUSIONS: Dogs could be potential carriers of Salmonella infection. The isolation of Salmonella in healthy dogs instead of dogs suffering from diarrhoea indicates that attention should be paid to asymptomatic carriage. The emergence of resistance among zoonotic Salmonella isolates poses a significant threat to public health.

Accumulation of resistance genes in Salmonella Typhimurium transmitted between poultry and dairy farms increases the risk to public health.

Salmonella Typhimurium is a zoonotic pathogen that poses a major threat to public health. This generalist serotype can be found in many hosts and the environment where varying selection pressures may result in the accumulation of antimicrobial resistance determinants. However, the transmission of this serotype between food-producing hosts, specifically between poultry layer flocks and nearby dairy herds, was never demonstrated. We investigated an outbreak at a dairy in Israel to determine the role of nearby poultry houses to be sources of infection. The 2-month outbreak resulted in a 47% mortality rate among 15 calves born in that period. Routine treatment of fluid therapy, a nonsteroidal anti-inflammatory, and cefquinome was ineffective, and control was achieved by the introduction of vaccination of dry cows against Salmonella (Bovivac S, MSD Animal Health) and a strict colostrum regime. Whole genome sequencing and antimicrobial sensitivity tests were performed on S. Typhimurium strains isolated from the dairy (n = 4) and strains recovered from poultry layer farms (n = 10). We identified acquired antimicrobial-resistant genes, including the blaCTX-M-55 gene, conferring resistance to extended-spectrum cephalosporins, which was exclusive to dairy isolates. Genetic similarity with less than five single nucleotide polymorphism differences between dairy and poultry strains suggested a transmission link. This investigation highlights the severe impact of S. Typhimurium on dairy farms and the transmission risk from nearby poultry farms. The accumulation of potentially transferable genes conferring resistance to critically important antimicrobials underscores the increased public health risk associated with S. Typhimurium circulation between animal hosts.IMPORTANCESalmonella Typhimurium is one of the major causes of food-borne illness globally. Infections may result in severe invasive disease, in which antimicrobial treatment is warranted. Therefore, the emergence of multi-drug-resistant strains poses a significant challenge to successful treatment and is considered one of the major threats to global health. S. Typhimurium can be found in a variety of animal hosts and environments; however, its transmission between food-producing animals, specifically poultry layers flocks and dairy herds, was never studied. Here, we demonstrate the transmission of the pathogen from poultry to a nearby dairy farm. Alarmingly, the multi-drug-resistant strains collected during the outbreak in the dairy had acquired resistance to extended-spectrum cephalosporins, antibiotics critically important in treating Salmonellosis in humans. The findings of the study emphasize the increased risk to public health posed by zoonotic pathogens' circulation between animal hosts.

Serovar and sequence type distribution and phenotypic and genotypic antimicrobial resistance of Salmonella originating from pet animals in Chongqing, China.

A total of 334 Salmonella isolates were recovered from 6,223 pet rectal samples collected at 50 pet clinics, 42 pet shops, 7 residential areas, and 4 plazas. Forty serovars were identified that included all strains except for one isolate that did not cluster via self-agglutination, with Salmonella Typhimurium monophasic variant, Salmonella Kentucky, Salmonella Enteritidis, Salmonella Pomona, and Salmonella Give being the predominant serovars. Fifty-one sequence types were identified among the isolates, and ST198, ST11, ST19, ST451, ST34, and ST155 were the most common. The top four dominant antimicrobials to which isolates were resistant were sulfisoxazole, ampicillin, doxycycline, and tetracycline, and 217 isolates exhibited multidrug resistance. The prevalence of ß-lactamase genes in Salmonella isolates was 59.6%, and among these isolates, 185 harbored blaTEM, followed by blaCTX-M (66) and blaOXA (10). Moreover, six PMQR genes, namely, including qnrA (4.8%), qnrB (4.2%), qnrD (0.9%), qnrS (18.9%), aac(6')-Ib-cr (16.5%), and oqxB (1.5%), were detected. QRDR mutations (76.6%) were very common in Salmonella isolates, with the most frequent mutation in parC (T57S) (47.3%). Furthermore, we detected six tetracycline resistance genes in 176 isolates, namely, tet(A) (39.5%), tet(B) (8.1%), tet(M) (7.7%), tet(D) (5.4%), tet(J) (3.3%), and tet(C) (1.8%), and three sulfonamide resistance genes in 303 isolates, namely, sul1 (84.4%), sul2 (31.1%), and sul3 (4.2%). Finally, we found 86 isolates simultaneously harboring four types of resistance genes that cotransferred 2-7 resistance genes to recipient bacteria. The frequent occurrence of antimicrobial resistance, particularly in dogs and cats, suggests that antibiotic misuse may be driving multidrug-resistant Salmonella among pets.IMPORTANCEPet-associated human salmonellosis has been reported for many years, and antimicrobial resistance in pet-associated Salmonella has become a serious public health problem and has attracted increasing attention. There are no reports of Salmonella from pets and their antimicrobial resistance in Chongqing, China. In this study, we investigated the prevalence, serovar diversity, sequence types, and antimicrobial resistance of Salmonella strains isolated from pet fecal samples in Chongqing. In addition, ß-lactamase, QRDR, PMQR, tetracycline and sulfonamide resistance genes, and mutations in QRDRs in Salmonella isolates were examined. Our findings demonstrated the diversity of serovars and sequence types of Salmonella isolates. The isolates were widely resistant to antimicrobials, notably with a high proportion of multidrug-resistant strains, which highlights the potential direct or indirect transmission of multidrug-resistant Salmonella from pets to humans. Furthermore, resistance genes were widely prevalent in the isolates, and most of the resistance genes were spread horizontally between strains.

Mercury Exposure Is Associated with Urbanization but not Salmonella Status in White Ibis (Eudocimus albus).

Mercury (Hg) is a ubiquitous contaminant in wetlands that can cause immunosuppression in birds, which may increase susceptibility to colonization with Salmonella spp. Previously, we found that White Ibis (Eudocimus albus), a recently urbanized wading bird, shed Salmonella spp. at a higher prevalence when captured at urban sites, compared with natural sites. In this study, we sought to determine if Hg burdens in ibis are related to Salmonella status or degree of urbanization or both. We analyzed feathers from 94 ibis in Palm Beach County, Florida, USA, along an urbanization gradient (0-68% urbanization) and from individuals with confirmed Salmonella spp. status (shedding or not shedding). We detected Hg in all ibis feathers (0.22-8.47 mg/kg; mean=1.96 mg/kg; SD=1.94). The Hg concentration was not significantly correlated to Salmonella spp. shedding status (Wilcoxon rank sum test, W=1170; P=0.596) but was negatively associated with capture site urbanization level (R2=0.327; P=0.026). Our findings may suggest that the immunosuppressive effects of Hg do not affect Salmonella shedding in the ibis or that Hg burdens were too low to affect Salmonella shedding status. Further, ibis that were captured in high urbanization sites appeared to have a lower risk of Hg exposure than ibis that were captured within low urbanization sites.

Salmonella carriage and change in serovar distribution in broiler giblets at slaughterhouse level in Turkiye: first report using ISO 6579-1:2017 and ISO 6579-3:2014.

This study aimed to determine the prevalence and serovar distribution of salmonellae in liver, heart, and spleen (LHS) and gizzard (G) of slaughtered broilers. For this, a total of 60 sample units, comprised of 30 LHS and 30 G collected from 3 slaughterhouses, were analysed by reference methods for detection and serotyping as revised ISO 6579-1:2017 and ISO 6579-3:2014, respectively. Also, Salmonella-specific real-time PCR (Salm-PCR) was used for species confirmation, while Salmonella Enteritidis (S. Enteritidis) and Salmonella Typhimurium (S. Typhimurium) specific real-time PCR (SE/ST-PCR) was evaluated to determine its efficiency for rapid detection of the serovars mandated in current legal regulations compared to standard serotyping. All LHS (100%-30/30) and 90% (27/30) of G samples harbored Salmonella with an overall prevalence of 95% (57/60) in samples examined, where all isolates were confirmed as Salmonella by Salm-PCR. The most prevalent serovar in broiler giblets was S. Virchow (80.70%-46/57) followed by S. Enteritidis (19.30%-11/57). SE/ST-PCR (%17.54-10/57) could not detect one G isolate, which was serotyped as S. Enteritidis by standard serotyping. High relative accuracy (98.25%), sensitivity (100%) and specificity (100%), and agreement between methods (κ: 0.94) verified SE/ST-PCR's potential to be used as an alternative in rapid detection of S. Enteritidis and S. Typhimurium. Data on high Salmonella prevalence in broiler giblets of slaughterhouse origin, and detection of the pathogen by the implementation of all requirements indicated in the revised ISO 6579-1:2017 standard method, enabling the determination of actual prevalence in the samples with high sensitivity and specificity is of significance for public health. Additionally, identification of S. Virchow as the dominant serovar followed by S. Enteritidis with a relatively lower prevalence, and absence of S. Typhimurium in broiler giblets are important findings for Turkiye. This up to date data, obtained by strict application of ISO 6579-3:2014 procedures, indicated a shift in circulating serovars in the broiler industry. The objective findings in this study would bring awareness to national/international literature, and may be of use in future improvements in legal regulations.

Centralized industrialization of pork in Europe and America contributes to the global spread of Salmonella enterica.

Salmonella enterica causes severe food-borne infections through contamination of the food supply chain. Its evolution has been associated with human activities, especially animal husbandry. Advances in intensive farming and global transportation have substantially reshaped the pig industry, but their impact on the evolution of associated zoonotic pathogens such as S. enterica remains unresolved. Here we investigated the population fluctuation, accumulation of antimicrobial resistance genes and international serovar Choleraesuis transmission of nine pig-enriched S. enterica populations comprising more than 9,000 genomes. Most changes were found to be attributable to the developments of the modern pig industry. All pig-enriched salmonellae experienced host transfers in pigs and/or population expansions over the past century, with pigs and pork having become the main sources of S. enterica transmissions to other hosts. Overall, our analysis revealed strong associations between the transmission of pig-enriched salmonellae and the global pork trade.

Prevalence and antimicrobial susceptibility of Salmonella enteritidis and Salmonella typhimurium isolated from hen eggs and quail eggs in Karaj, Iran.

BACKGROUND AND AIM: Different Salmonella serotypes are considered one of the most important food pathogens in the world. Poultry meat and eggs are the primary carriers of Salmonella in human populations. This study aimed to estimate the Salmonella enteritidis and Salmonella typhimurium contamination rates of retail hen and quail eggs in Karaj, Iran. Moreover, the antimicrobial resistance patterns of the strains were evaluated, and the efficiency of the standard culture method and multiplex polymerase chain reaction (m-PCR) were compared. MATERIALS AND METHODS: In this descriptive cross-sectional study over 1 year (Jan-Dec 2022), 150 commercial and 150 backyard hen eggs and 300 commercial quail eggs, without cracks and fractures, were collected randomly from best selling groceries in Karaj city. All samples were examined for Salmonella contamination independently by standard culture and m-PCR approaches. A standard disc diffusion method was employed to assess the antimicrobial susceptibility of the strains against 18 antimicrobial agents. RESULTS: Out of 300 examined eggs, 2 S. enteritidis strains were isolated from the shell of backyard hen eggs. The same serotype was also detected in the contents of one of these two eggs. One S. typhimurium was isolated from the shell of a commercial hen egg. Overall, the Salmonella contamination of the shell and contents was 1% and 0.3%, respectively. Salmonella was not isolated from the eggshells or the contents of the quail eggs. There was complete agreement between the results of m-PCR and the standard culture methods. Among the 18 tested antibiotics, the highest resistance was recorded for colistin (100%), followed by nalidixic acid (75%). CONCLUSION: As most Salmonella spp. are associated with human food poisoning, continuous surveillance is required to effectively reduce the risk posed by contaminated poultry eggs. Furthermore, mandatory monitoring of antimicrobial use on Iranian poultry farms is recommended.

Comparative genomics reveals high genetic similarity among strains of Salmonella enterica serovar Infantis isolated from multiple sources in Brazil.

Background: Salmonella enterica serovar Infantis (Salmonella Infantis) is a zoonotic, ubiquitous and foodborne pathogen of worldwide distribution. Despite Brazil's relevance as a major meat exporter, few studies were conducted to characterize strains of this serovar by genomic analyses in this country. Therefore, this study aimed to assess the diversity of 80 Salmonella Infantis strains isolated from veterinary, food and human sources in Brazil between 2013 and 2018 by comparative genomic analyses. Additional genomes of non-Brazilian countries (n = 18) were included for comparison purposes in some analyses. Methods: Analyses of whole-genome multi-locus sequence typing (wgMLST), using PGAdb-builder, and of fragmented genomes, using Gegenees, were conducted to compare the 80 Brazilian strains to the 18 non-Brazilian genomes. Pangenome analyses and calculations were performed for all Salmonella Infantis genomes analyzed. The presence of prophages was determined using PHASTER for the 80 Brazilian strains. The genome plasticity using BLAST Ring Image Generator (BRIG) and gene synteny using Mauve were evaluated for 20 selected Salmonella Infantis genomes from Brazil and ten from non-Brazilian countries. Unique orthologous protein clusters were searched in ten selected Salmonella Infantis genomes from Brazil and ten from non-Brazilian countries. Results: wgMLST and Gegenees showed a high genomic similarity among some Brazilian Salmonella Infantis genomes, and also the correlation of some clusters with non-Brazilian genomes. Gegenees also showed an overall similarity >91% among all Salmonella Infantis genomes. Pangenome calculations revealed an open pangenome for all Salmonella Infantis subsets analyzed and a high gene content in the core genomes. Fifteen types of prophages were detected among 97.5% of the Brazilian strains. BRIG and Mauve demonstrated a high structural similarity among the Brazilian and non-Brazilian isolates. Unique orthologous protein clusters related to biological processes, molecular functions, and cellular components were detected among Brazilian and non-Brazilian genomes. Conclusion: The results presented using different genomic approaches emphasized the significant genomic similarity among Brazilian Salmonella Infantis genomes analyzed, suggesting wide distribution of closely related genotypes among diverse sources in Brazil. The data generated contributed to novel information regarding the genomic diversity of Brazilian and non-Brazilian Salmonella Infantis in comparison. The different genetically related subtypes of Salmonella Infantis from Brazil can either occur exclusively within the country, or also in other countries, suggesting that some exportation of the Brazilian genotypes may have already occurred.

Occurrence, virulence, and resistance genes in Salmonella enterica isolated from an integrated poultry company in Jordan.

Salmonella is considered one of the most common foodborne pathogens worldwide. The annual number of hospitalizations and deaths related to zoonotic salmonellosis, which is transmitted from animals to humans and infects poultry and meat, is expected to be significant. Hence, the primary aims of this research were to isolate and characterize Salmonella species obtained from an integrated poultry company and identify some virulence, and antimicrobial resistance, with a specific concern about colistin resistance genes. A total of 635 samples collected from various sources in an integrated company in Jordan were screened for Salmonella species accompanying their virulence and antimicrobial resistance genes. Samples were collected from parent stock house drag swabs, broiler farms, premix, cecum at the slaughterhouse level, prechilling and postchilling stages, and the final product. Salmonella species were detected in 3% (6/200) of investigated parent stock house drag swabs, 13.8% (11/80) from cloacal swabs from broiler farms, 16.9% (11/65) from boiler farms premix, 24.4% (11/45) from the cecum at slaughterhouse level, 16.4% (9/55) from the prechilling stage, 37.8% (17/45) from the postchilling stage and 53.3% (24/45) from the final product stage. No isolates were detected in feed mills (0/20), parents' premix (0/40), or hatcheries (0/40). Salmonella isolates were resistant to ciprofloxacin (91.0%), nalidixic acid (86.5%), doxycycline (83.1%), tetracycline (83.1%), sulphamethoxazole-trimethoprim (79.8%) and ampicillin (76.4%). Serotyping shows that S. Infantis was the predominant serovar, with 56.2%. Based on the minimum inhibitory concentration (MIC) test, 39.3% (35/89) of the isolates were resistant to colistin; however, no mcr genes were detected. Among antimicrobial-resistant genes, blaTEM was the most prevalent (88.8%). Furthermore, the spvC, ompA, and ompF virulence genes showed the highest percentages (97.8%, 97.8%, and 96.6%, respectively). In conclusion, Salmonella isolates were found at various stages in the integrated company. S. Infantis was the most prevalent serotype. No mcr genes were detected. Cross-contamination between poultry production stages highlights the importance of good hygiene practices. Furthermore, the presence of virulence genes and the patterns of antimicrobial resistance present significant challenges for public health.

Evolution and genomic profile of Salmonella enterica serovar Gallinarum biovar Pullorum isolates from Brazil.

Salmonella enterica subspecies enterica serovar Gallinarum biovar Pullorum (S. Pullorum) is a pathogenic bacterium that causes Pullorum disease (PD). PD is an acute systemic disease that affects young chickens, causing white diarrhea and high mortality. Although many sanitary programs have been carried out to eradicate S. Pullorum, PD outbreaks have been reported in different types of birds (layers, broilers, breeders) worldwide. This study aimed to evaluate the evolution and genetic characteristics of S. Pullorum isolated from PD in Brazil. Phylogenetic analysis of S. Pullorum genomes sequenced in this study and available genomic databases demonstrated that all isolates from Brazil are from sequence type 92 (ST92) and cluster into two lineages (III and IV). ColpVC, IncFIC(FII), and IncFII(S) were plasmid replicons frequently found in the Brazilian lineages. Two resistance genes (aac(6')-Iaa, conferring resistance to aminoglycoside, disinfecting agents, and antiseptics (mdf(A)) and tetracycline (mdf(A)) were detected frequently. Altogether, these results are important to understand the circulation of S. Pullorum and, consequently, to develop strategies to reduce losses due to PD.

Evolución y perfil genómico de aislados de Salmonella enterica serovar Gallinarum biovar Pullorum de Brasil. Salmonella enterica subespecie enterica serovar Gallinarum biovar Pullorum (S. Pullorum) es una bacteria patógena que causa la enfermedad de Pullorum (EP). La EP es una enfermedad sistémica aguda que afecta a los pollos jóvenes causando diarrea blanca y alta mortalidad. Aunque se han llevado a cabo muchos programas sanitarios para erradicar S. Pullorum, se han informado brotes de EP en diferentes tipos de aves (ponedoras, pollos de engorde, reproductoras) en todo el mundo. Este estudio tuvo como objetivo evaluar la evolución y las características genéticas de S. Pullorum aislado de EP en Brasil. El análisis filogenético de los genomas de S. Pullorum secuenciados en este estudio y las bases de datos genómicas disponibles demostraron que todos los aislamientos de Brasil son del tipo de secuencia 92 (ST92) y se agrupan en dos linajes (III y IV). ColpVC, IncFIC (FII) e IncFII(S) fueron replicones de plásmidos frecuentemente encontrados en los linajes brasileños. Dos genes de resistencia (aac(6')-Iaa, que confiere resistencia a aminoglucósidos, desinfectantes y antisépticos (mdf(A)), y tetraciclina (mdf(A)) fueron detectados con frecuencia. En conjunto, estos resultados son importantes para comprender la circulación de S. Pullorum y, en consecuencia, desarrollar estrategias para reducir las pérdidas por EP.

The optimisation of Salmonella surveillance programmes for pullet and layer farms using local farm density as a risk factor.

Human salmonellosis cases are often caused by Salmonella serovars Enteritidis and Typhimurium and associated with the consumption of eggs and egg products. Many countries therefore implemented general surveillance programmes on pullet and layer farms. The identification of risk factors for Salmonella infection may be used to improve the performance of these surveillance programmes. The aims of this study were therefore to determine 1) whether local farm density is a risk factor for the infection of pullet and layer farms by Salmonella Enteritidis and Typhimurium and 2) whether the sampling effort of surveillance programmes can be reduced by accounting for this risk factor, while still providing sufficient control of these serovars. We assessed the importance of local farm density as a risk factor by fitting transmission kernels to Israeli surveillance data during the period from June 2017 to April 2019. The analysis shows that the risk of infection by serovars Enteritidis and Typhimurium significantly increased if infected farms were present within a radius of approximately 4 km and 0.3 km, respectively. We subsequently optimized a surveillance programme that subdivided layer farms into low and high risk groups based on the local farm density with and allowed the sampling frequency to vary between these groups. In this design, the pullet farms were always sampled one week prior to pullet distribution. Our analysis shows that the risk-based surveillance programme is able to keep the between-farm R0 of serovars Enteritidis and Typhimurium below 1 for all pullet and layer farms, while reducing the sampling effort by 32% compared to the currently implemented surveillance programme in Israel. The results of our study therefore indicate that local farm density is an important risk factor for infection of pullet and layer farms by Salmonella Enteritidis and Typhimurium and can be used to improve the performance of surveillance programmes.

Prevalence and characterization of non-typhoidal Salmonella in egg from grading and packing plants in Korea.

Egg washing guidelines vary across countries; however, since 2020, Korea has required that all eggs produced from farms with more than 10,000 laying hens must be washed through egg grading and packing (GP) plant. This study investigated the prevalence and characterization of non-typhoidal Salmonella in eggs after washing at GP plants. In total, 16,800 eggs were collected from 60 egg GP plants located inside commercial layer farms, and 840 pooled eggshell and egg contents were tested for Salmonella, respectively. Of the 60 GP plants tested, 11 (18.3%) and 12 (20.0%) plants were positive for Salmonella spp. In the eggshells and egg contents, respectively. In particular, High Salmonella prevalence in the eggshells and egg contents occurred most often in farms with laying hens older than 80 weeks (33.3% and 40.0%, respectively). However, among 840 pooled eggshells and egg content samples, only 19 (2.3%) of each sample type were positive only for non-typhoidal Salmonella spp. The most common Salmonella serovar in both eggshells and egg contents was S. Infantis, which was found in five (8.3%) of 60 GP plants for both samples types. The other Salmonella serovars detected in eggshells were S. Bareilly (5.0%), S. Agona (3.3%), S. Enteritidis (1.7%), and S. Montevideo (1.7%), whereas those detected in egg contents were S. Enteritidis (5.0%), S. Agona (3.3%), S. Newport (3.3%), S. Senftenberg (3.3%), and S. Derby (1.7%). Of the 19 virulence genes tested, 14 genes were detected in all Salmonella. Interestingly, the spvB gene was detected only in S. Enteritidis, and the sefC gene was detected only in S. Enteritidis and S. Senftenberg. Moreover, all S. Infantis isolates showed multidrug resistance (MDR) against five or more classes, and the other serovars only showed MDR against three to four classes or no MDR. These results suggest that comprehensive surveillance and advanced management approaches for egg GP plants are required to minimize egg contamination with non-typhoidal Salmonella.

Prevalence and transmission of extensively drug-resistant Salmonella enterica serovar Kentucky ST198 based on whole-genome sequence in an intensive laying hen farm in Jiangsu, China.

Salmonella, which is widely distributed in nature, is an important zoonotic pathogen affecting humans, livestock, and other animals. Salmonella infection not only hinders the development of livestock and poultry-related industries but also poses a great threat to human health. In this study, we collected 1,537 samples including weak chicks, dead embryos, fecal samples and environmental samples from 2020 to 2023 (for a period of 1 to 2 months per year) to keep a long-term monitor the prevalence of Salmonella in an intensive laying hen farm, 105 Salmonella strains were isolated with an isolation rate of 6.83% (105/1,537). It revealed a significant decrease in prevalence rates of Salmonella over time (P < 0.001). Before 2020, the predominant serotype was S. Enteritidis. S. Kentucky was first detected in November 2020 and its proportion was gradually found to exceed that of S. Enteritidis since then. S. Kentucky isolates were distributed in various links of the four regions in the poultry farm. A total of 55 S. Kentucky strains, were assigned to ST198 based on whole genome sequencing. Among them, 54 strains were resistant to 12 to 16 antibiotics, indicating that they were extensively drug-resistant (XDR). Seventeen antimicrobial resistance genes were detected in 55 S. Kentucky isolates. For most of these isolates, antibiotic resistance phenotypes were concordant with their genotypes. All S. Kentucky strains isolated from this farm in 2020 to 2023 showed a high similarity based on their core-genome SNP-based phylogeny. The traceability analysis revealed that S. Kentucky was introduced to the farm through newly purchased flocks. The long-term existence of XDR S. Kentucky ST198 poses a substantial risk because of the multiage management and circulation of workers in this poultry farm. Thus, this study is the first to report extensively drug-resistant S. Kentucky ST198 detected in this intensive poultry farm in China.

Phenotypic and genetic characterization of antimicrobial resistance in Salmonella enterica serovar Choleraesuis isolates from humans and animals in Spain from 2006 to 2021.

OBJECTIVES: While an increase in the levels of MDR in Salmonella enterica sevorar Choleraesuis has been reported in Europe, little is known about the situation in Spain. Therefore, we first aimed to assess the phenotypic resistance profile and to determine the presence of genetic determinants of resistance of S. Choleraesuis isolates collected in animal and human. Our second objective was to identify and characterize clusters of highly related isolates. METHODS: We analysed 50 human and 45 animal isolates retrieved from 2006 to 2021 using the disc diffusion method and performed WGS followed by analyses of genetic determinants and phylogenetic analysis. RESULTS: All isolates were of ST145 and corresponded to the variant Kunzendorf. Swine isolates harboured a significantly higher number of antimicrobial resistance genes than human isolates, and often carried plasmid replicons of the IncHI2/IncHI2A type (42% of all animal isolates). In addition, we identified several MDR S. Choleraesuis strains circulating in humans and swine between 2006 and 2021. The phylogenetic analyses identified four clades associated with specific patterns of resistance genes and plasmid replicons. The clades also included isolates that differed in terms of year and region of isolation as well as host of origin. CONCLUSIONS: This One Health approach highlights that reducing human MDR S. Choleraesuis infections may require the adoption of strategies that not only seek to prevent cases in humans but also to characterize and reduce the infection burden in swine.

Emergence of Salmonella Infantis carrying the pESI megaplasmid in commercial farms of five major integrated broiler operations in Korea.

Considering Salmonella transmission occurs through several routes in integrated broiler operations, control of nontyphoidal Salmonella in commercial farms is essential. This study aimed to compare the distribution of persistent Salmonella serovars in environments and dead chickens between 5 major integrated broiler operations in Korea. The prevalence of Salmonella-positive farms in dust prior to placement by operations was 0 to 25%, but the prevalence in dust and feces at the time of depletion was increased to 16.7 to 41.7% and 16.7 to 66.7%, respectively. Moreover, the prevalence of farms with Salmonella in chickens that died within 1 week old and at 4 to 5 weeks old ranged from 8.3 to 58.3% and 16.7 to 41.7%, respectively. The prevalence of Salmonella enterica serovar Infantis-positive farms in dust prior to placement and in chickens that died within 1 week old was 5.2 and 3.4%, respectively, but the prevalence in dust and feces at the time of depletion and in chickens that died at 4 to 5 weeks old was significantly increased to 27.6, 41.4, and 20.7%, respectively (P < 0.05). Interestingly, the plasmid of emerging S. Infantis (pESI) was only identified in S. Infantis, and the prevalence of multidrug-resistance was significantly higher in pESI-positive S. Infantis (99.2%) than in pESI-negative S. Infantis (6.7%) (P < 0.05). The distribution of pulsotypes between pESI-positive and pESI-negative S. Infantis were varied, but a majority of S. Infantis were clustered only 2 pulsotypes. Moreover, pESI-positive S. Infantis harbored more virulence factors than pESI-negative S. Infantis. This study is the first report on characteristics of S. Infantis carrying the pESI plasmid in commercial broiler farms in Korea.