Results of salmonella isolation from poultry products, poultry, poultry environment, and other characteristics

A review of the global emergence of multidrug-resistant Salmonella enterica subsp. enterica Serovar Infantis

Salmonella enterica serovar Infantis is an emergent foodborne and zoonotic Salmonella serovar with critical implications for global health. In recent years, the prevalence of S. Infantis infections has increased in the United States, Europe, and Latin America, due to contaminated chicken and other foods. An essential trait of S. Infantis is its resistance to multiple antibiotics, including the critically important third-generation cephalosporins and quinolones, undermining effective medical treatment, particularly in low-resource settings. We describe the emergence of multidrug-resistant (MDR) S. Infantis, focusing on humans, animals, the environment, and food. We conducted a systematic review (1979-2021), selected 183 studies, and analyzed the origin, source, antimicrobial resistance, and presence of a conjugative plasmid of emerging S. Infantis (pESI) in reported isolates. S. Infantis has been detected worldwide, with a substantial increase since 2011. We found the highest number of isolations in the Americas (42.9 %), Europe (29.8 %), Western Pacific (17.2 %), Eastern Mediterranean (6.6 %), Africa (3.4 %), and South-East Asia (0.1 %). S. Infantis showed MDR patterns and numerous resistant genes in all sources. The primary source of MDR S. Infantis is broiler and their meat; however, this emerging pathogen is also present in other reservoirs such as food, wildlife, and the environment. Clinical cases of MDR S. Infantis have been reported in children and adults. The global emergence of S. Infantis is related to a plasmid (pESI) with antibiotic and arsenic- and mercury-resistance genes. Additionally, a new megaplasmid (pESI-like), carrying blaCTX-M-65 and antibiotic-resistant genes reported in an ancestral version, was detected in the broiler, human, and chicken meat isolates. Strains harboring pESI-like were primarily observed in the Americas and Europe. MDR S. Infantis has spread globally, potentially becoming a major public health threat, particularly in low- and middle-income countries.

A systematic review and meta-analysis of the sources of Salmonella in poultry production (pre-harvest) and their relative contributions to the microbial risk of poultry meat

Salmonella is a major foodborne pathogen associated with poultry and poultry products and a leading cause for human salmonellosis. Salmonella is known to transmit in poultry flocks both vertically and horizontally. However, there is a lack of knowledge on relative contribution of the factors on Salmonella prevalence in poultry live production system including hatchery, feed, water, environment-interior, and -exterior. Therefore, a systematic review and meta-analysis was conducted to quantify the potential sources of Salmonella during preharvest and their relative contributions to the microbial risk of poultry meat. A total of 16,800 studies identified from Google Scholar and 37 relevant studies were included in the meta-analysis for relative contributions to Salmonella positivity on broilers after applying exclusion criteria. A generalized linear mixed model approach combined with logit transformation was used in the current study to stabilize the variance. The analysis revealed that the hatchery is the most significant contributor of Salmonella with a prevalence of 48.5%. Litter, feces, and poultry house internal environment were the other 3 major contributing factors with a prevalence of 25.4, 16.3, and 7.9%, respectively. Moreover, poultry house external environment (4.7%), feed (4.8%), chicks (4.7%), and drinker water also contributed to the Salmonella positivity. Results from this meta-analysis informed the urgent need for controls in live production to further reduce Salmonella in fresh, processed poultry. The control strategies can include eliminating the sources of Salmonella and incorporating interventions in live production to reduce Salmonella concentrations in broilers.

Antibiotic Resistance Genes Occurrence in Conventional and Antibiotic-Free Poultry Farming, Italy

Antimicrobial resistance is a complex and widespread problem threatening human and animal health. In poultry farms, a wide distribution of resistant bacteria and their relative genes is described worldwide, including in Italy. In this paper, a comparison of resistance gene distribution in litter samples, recovered from four conventional and four antibiotic-free broiler flocks, was performed to highlight any influence of farming systems on the spreading and maintenance of resistance determinants. Conventional PCR tests, targeting the resistance genes related to the most used antibiotics in poultry farming, along with some critically important antibiotics for human medicine, were applied. In conventional farms, n. 10 out of n. 30 investigated genes were present in at least one sample, the most abundant fragments being the tet genes specific for tetracyclines, followed by those for aminoglycosides and chloramphenicol. All conventional samples resulted negative for colistin, carbapenems, and vancomycin resistance genes. A similar trend was observed for antibiotic-free herds, with n. 13 out of n. 30 amplified genes, while a positivity for the mcr-1 gene, specific for colistin, was observed in one antibiotic-free flock. The statistical analysis revealed a significant difference for the tetM gene, which was found more frequently in the antibiotic-free category. The analysis carried out in this study allowed us to obtain new data about the distribution of resistance patterns in the poultry industry in relation to farming types. The PCR test is a quick and non-expensive laboratory tool for the environmental monitoring of resistance determinants identifying potential indicators of AMR dissemination.

Evaluation of the different methods to detect Salmonella in poultry feces samples

Salmonella is one of the most common causes of foodborne outbreaks and infection worldwide. The gold-standard detection method of Salmonella is cultivation. There is a need to investigate rapid and accurate processes with time-consuming cultivation. The study evaluated different approaches to detect Salmonella in poultry feces samples. Poultry farm feces samples from 21 cities in Iran were collected from January 2016 to December 2019. Microbiological cultures, serological assays, and multiplex PCR (m-PCR) were used to detect and characterize Salmonella spp. isolates. Serological assays and m-PCR were used to determine the serogroups A, B, C1, C2, D1, E, H, and FliC. The m-PCR was used to detect seven Salmonella serovars, and a Chi-square test was performed to compare the discriminatory power of the methods. Of 2300 poultry feces samples, 173 (7.5%) and 166 (7.2%) samples were detected as Salmonella spp. by cultivation and m-PCR, respectively. The sensitivity of the molecular method was equal to cultivation at 0.96 (CI = 95%). Assessment of H antigenic subgroups showed the same for both m-PCR and serological tests. Therefore, the matching rate of the two methods for detecting all H antigenic subgroups was 100%. Thus, the relationship between the results obtained from both methods was significant in the contingency table test (P < 0.01). The PCR-based approach confirmed the detection of Salmonella in a shorter period (24-36 h) compared to the conventional microbiological approach (3-8 days).

Sex Differences in Salmonellosis Incidence Rates-An Eight-Country National Data-Pooled Analysis

Background: There are few studies on sex differences in the incidence rates (IR) for salmonellosis over several countries by age and time period. The purpose of this study was to explore the extent and consistency of the sex and age-specific differences. Methods: We analyzed national data from eight countries between 1994 and 2016. We computed country-specific male to female incidence rate ratios (IRRs) for each age group and pooled the data using meta-analytic methods. Variations of the IRRs by age, country and time period were evaluated using meta-regression. Results: The pooled male to female incidence RRs for ages 0–1, 1–4, 5–9 and 10–14, were 1.04 (1.02–1.06), 1.02 (1.01–1.03), 1.07 (1.05–1.08) and 1.28 (1.23–1.33), respectively. For the ages 15–44 and 45–64, the incidence rates were significantly higher in females. Meta-regression analyses indicate that age groups contributed most of the variation in the male to female IRRs. Conclusions: We suggest that genetic and hormonal factors and interactions between hormones and gut microbiota could contribute to the sex differences observed in young children. These findings should provide clues about the mechanisms of the infection, and should be useful in targeting treatments and development of vaccines. Highlights: (1) This manuscript provides consistent estimates of the excess salmonellosis incidence rates in male children up to age 15, which suggests an impact of sex hormones or genetic differences. (2) Our findings should promote the further investigations on sex-related determinants of infectious diseases.

Effects of Salmonella enterica ser. Enteritidis and Heidelberg on host CD4+CD25+ regulatory T cell suppressive immune responses in chickens

Poultry infected with Salmonella mount an immune response initially, however the immune responses eventually disappear leading the bird to be a carrier of Salmonella. The hypothesis of this study is that Salmonella infection induces T regulatory cell numbers and cytokine production and suppress host T cells locally in the gut to escape the host immune responses. An experiment was conducted to comparatively analyze the effect of S. enterica ser. Enteritidis (S. Enteritidis) and S. enterica ser. Heidelberg (S. Heidelberg) infection on CD4⁺CD25⁺ T regulatory cell properties in chickens. A total of 144 broiler chicks were randomly distributed into three experimental groups of non-infected control, S. Enteritidis infected and S. Heidelberg infected groups. Chickens were orally inoculated with PBS (control) or 5x10⁶ CFU/mL of either S. Enteritidis or S. Heidelberg at 3 d of age. Each group was replicated in six pens with eight chickens per pen. Chickens infected with S. Enteritidis had 6.2, 5.4, and 3.8 log₁₀ CFU/g, and chickens infected with S. Heidelberg had 7.1, 4.8, and 4.1 log₁₀ CFU/g Salmonella in the cecal contents at 4, 11, and 32 dpi, respectively. Both S. Enteritidis and S. Heidelberg were recovered from the liver and spleen 4 dpi. At 4, 11, and 32 dpi, chickens infected with S. Enteritidis and S. Heidelberg had increased CD4⁺CD25⁺ cell numbers as well as IL-10 mRNA transcription of CD4⁺CD25⁺ cells compared to that in the control group. CD4⁺CD25⁺ cells from S. Enteritidis- and S. Heidelberg-infected chickens and restimulated with 1 μg antigen in vitro, had higher (P < 0.05) IL-10 mRNA transcription than the CD4⁺CD25⁺ cells from the non-infected controls Though at 4dpi, chickens infected with S. Enteritidis and S. Heidelberg had a significant (P < 0.05) increase in CD4⁺CD25^- IL-2, IL-1β, and IFNγ mRNA transcription, the CD4⁺CD25^- IL-2, IL-1β, and IFNγ mRNA transcription, were comparable to that in the control group at 11 and 32dpi identifying that the host inflammatory response against Salmonella disappears at 11 dpi. It can be concluded that S. Enteritidis and S. Heidelberg infection at 3 d of age induces a persistent infection through inducing CD4⁺CD25⁺ cells and altering the IL-10 mRNA transcription of CD4⁺CD25⁺ cell numbers and cytokine production in chickens between 3 to 32 dpi allowing chickens to become asymptomatic carriers of Salmonella after 18 dpi.

Antibiotic resistance in the pathogenic foodborne bacteria isolated from raw kebab and hamburger: phenotypic and genotypic study

Background

In recent years, interest in the consumption of ready-to-eat (RTE) food products has been increased in many countries. However, RTE products particularly those prepared by meat may be potential vehicles of antibiotic-resistance foodborne pathogens. Considering kebab and hamburger are the most popular RTE meat products in Iran, this study aimed to investigate the prevalence and antimicrobial resistance of common foodborne pathogens (Escherichia coli, Salmonella spp., Staphylococcus aureus, and Listeria monocytogenes) in raw kebab and hamburger samples collected from fast-food centers and restaurants. Therefore, total bacterial count (TBC), as well as the prevalence rates and antibiogram patterns of foodborne pathogens in the samples were investigated. Also, the presence of antibiotic-resistance genes (bla_SHV, bla_TEM,bla_Z, and mecA) was studied in the isolates by PCR.

Results

The mean value of TBC in raw kebab and hamburger samples was 6.72 ± 0.68 log CFU/g and 6.64 ± 0.66 log CFU/g, respectively. E. coli had the highest prevalence rate among the investigated pathogenic bacteria in kebab (70%) and hamburger samples (48%). Salmonella spp., L. monocytogenes, and S. aureus were also recovered from 58, 50, and 36% of kebab samples, respectively. The contamination of hamburger samples was detected to S. aureus (22%), L. monocytogenes (22%), and Salmonella spp. (10%). In the antimicrobial susceptibility tests, all isolates exhibited high rates of antibiotic resistance, particularly against amoxicillin, penicillin, and cefalexin (79.66–100%). The bla_TEM was the most common resistant gene in the isolates of E. coli (52.54%) and Salmonella spp. (44.11%). Fourteen isolates (23.72%) of E. coli and 10 isolates (29.41%) of Salmonella spp. were positive for bla_SHV. Also, 16 isolates (55.17%) of S. aureus and 10 isolates (27.27%) of L. monocytogenes were positive for mecA gene.

Conclusions

The findings of this study showed that raw kebab and hamburger are potential carriers of antibiotic-resistance pathogenic bacteria, which can be a serious threat to public health.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02326-8.

Global spread of Salmonella Enteritidis via centralized sourcing and international trade of poultry breeding stocks

A pandemic of Salmonella enterica serotype Enteritidis emerged in the 1980s due to contaminated poultry products. How Salmonella Enteritidis rapidly swept through continents remains a historical puzzle as the pathogen continues to cause outbreaks and poultry supply becomes globalized. We hypothesize that international trade of infected breeding stocks causes global spread of the pathogen. By integrating over 30,000 Salmonella Enteritidis genomes from 98 countries during 1949-2020 and international trade of live poultry from the 1980s to the late 2010s, we present multifaceted evidence that converges on a high likelihood, global scale, and extended protraction of Salmonella Enteritidis dissemination via centralized sourcing and international trade of breeding stocks. We discovered recent, genetically near-identical isolates from domestically raised poultry in North and South America. We obtained phylodynamic characteristics of global Salmonella Enteritidis populations that lend spatiotemporal support for its dispersal from centralized origins during the pandemic. We identified concordant patterns of international trade of breeding stocks and quantitatively established a driving role of the trade in the geographic dispersal of Salmonella Enteritidis, suggesting that the centralized origins were infected breeding stocks. Here we demonstrate the value of integrative and hypothesis-driven data mining in unravelling otherwise difficult-to-probe pathogen dissemination from hidden origins.

Emergence and Spread of Different ESBL-Producing Salmonella enterica Serovars in Hospitalized Horses Sharing a Highly Transferable IncM2 CTX-M-3-Encoding Plasmid

Salmonella enterica is a major causative pathogen of human and animal gastroenteritis. Antibiotic resistant strains have emerged due to the production of extended-spectrum β-lactamases (ESBLs) posing a major health concern. With the increasing reports on ESBL-producing Enterobacterales that colonize companion animals, we aimed to investigate ESBL dissemination among ESBL-producing Salmonella enterica (ESBL-S) in hospitalized horses. We prospectively collected ESBL-S isolates from hospitalized horses in a Veterinary-Teaching Hospital during Dec 2015-Dec 2017. Selection criteria for ESBL-S were white colonies on CHROMagarESBL plates and an ESBL phenotypic confirmation. Salmonella enterica serovars were determined using the Kaufmann-White-Le-Minor serological scheme. ESBL-encoding plasmids were purified, transformed and compared using restriction fragment length polymorphism (RFLP). Whole genome sequencing (Illumina and MinION platforms) were performed for detailed phylogenetic and plasmid analyses. Twelve ESBL-S were included in this study. Molecular investigation and Sequence Read Archive (SRA) meta-analysis revealed the presence of three unique Salmonella enterica serovars, Cerro, Havana and Liverpool, all reported for the first time in horses. PFGE revealed the clonal spread of S. Cerro between seven horses. All twelve isolates carried bla CTX-M- 3 and showed an identical multidrug resistance profile with co-resistance to trimethoprim/sulfamethoxazole and to aminoglycosides. Plasmid RFLP proved the inter-serovar horizontal spread of a single bla CTX-M- 3-encoding plasmid. Complete sequence of a representative plasmid (S. Havana strain 373.3.1), designated pSEIL-3 was a -86.4 Kb IncM2 plasmid, that encoded nine antibiotic resistance genes. pSEIL-3 was virtually identical to pCTX-M3 from Citrobacter freundii, and showed high identity (>95%) to six other bla CTX-M- 3 or bla NDM- 1 IncM2 broad host range plasmids from various Enterobacterales of human origin. Using a specific six gene-based multiplex PCR, we detected pSEIL-3 in various Enterobacterales species that co-colonized the horses' gut. Together, our findings show the alarming emergence of ESBL-S in hospitalized horses associated with gut shedding and foal morbidity and mortality. We demonstrated the dissemination of CTX-M-3 ESBL among different Salmonella enterica serovars due to transmission of a broad host range plasmid. This report highlights horses as a zoonotic reservoir for ESBL-S, including highly transmissible plasmids that may represent a 'One-Health' hazard. This risk calls for the implementation of infection control measures to monitor and control the spread of ESBL-S in hospitalized horses.

Shared Extended-Spectrum β-Lactamase-Producing Salmonella Serovars between Agricultural and Aquatic Environments Revealed through invA Amplicon Sequencing

The presence of antibiotic-resistant Salmonella spp. in the environment is of great public health interest, worldwide. Furthermore, its extended-spectrum β-lactamase (ESBL)-producing strains constitute an emerging global health concern due to their limited treatment options in hospital. Therefore, this study aimed at characterising and tracking nonresistant and ESBL-producing Salmonella spp. from agricultural settings to nearby water sources highlighting their antibiotic resistance genes (ARG) and virulence factor (VF) distribution using a combination of both culture-dependent and independent methods. Furthermore, this study investigated the diversity and shared serovars among sampled matrices using amplicon sequencing of the invasion gene A (invA) of Salmonella spp. The results showed that soil had the highest prevalence of Salmonella spp. (62.5%, 65/104) and ESBL-producing Salmonella (34.6%, 36/104). For typed ARG, the most commonly detected gene was blaOXA with 75% (30/40), followed by blaCTX-M 67.5% (27/40),blaTEM 40% (16/40) and sul1 30% (12/40) gene; blaSHV gene was not detected in isolated ESBL-producing Salmonella spp. For VF, the most detected gene was invA (96.9%, 38/40), followed by spaM (17.5%, 7/40), spiC (40%, 16/40), orfL (32.5%, 13/40), misL 32.5% (13/40) and pipD 32.5 (13/40). For diversity analysis, soil, manure, irrigation water and nearby freshwater revealed 81, 68, 12 and 9 serovars, respectively. Soil, manure, irrigation water and freshwater stream samples shared five serovars, which indicated circulation of ESBL-producing Salmonella spp. within the agricultural environment and nearby water sources. Soil is therefore identified as one of the major reservoirs of ESBL-producing Salmonella spp. It is concluded that agricultural environment contamination may have a direct relationship with the presence of antibiotic-producing Salmonella in freshwater streams.

Self-made Salmonella Pullorum agglutination antigen development and its potential practical application

Pullorum disease caused by Salmonella Pullorum is one of the most important infectious diseases in the poultry industry worldwide, which leads to serious economic losses in many developing countries because of its high mortality rate in young chicks. The traditional slide agglutination test with low cost, fast reaction, and on-site detection has been widely used in the diagnosis of Pullorum disease. However, in practice, the test performance is with the disadvantages of false positive results and unstable detection results. In this paper, we developed self-made agglutination antigens prepared by local isolates in the poultry farm and compare the detection performance with commercial agglutination antigens (China Institute of Veterinary Drug Control) and Group D Salmonella ELISA kit (BioChek UK Ltd). The results of detecting 200 serum samples indicated that the consistency of commercial agglutination antigen detecting in 2 times was only 79.5%. Using the ELISA kit as the reference method, the commercial agglutination antigen detecting results of the Kappa test were only moderately consistent (0.58 ∼ 0.59). Meanwhile, positive and total coincidence rates of the self-made agglutination antigen test with more reliable repeat could reach 97.4 and 88%, respectively, and the result of Kappa test was highly consistent (0.75). The Receiver Operating Characteristic curve analysis clarified that the area under the receiver-operating-characteristic curve values of self-made and commercial agglutination antigen tests could reach 0.861 and 0.804, respectively. These results were coincident when detecting known positive serum from the infected chickens. It's worth mentioning that the visible positive reaction of self-made agglutination antigen test appeared faster and stronger than commercial antigen test. In conclusion, self-made Salmonella Pullorum agglutination antigen developed in this study was much better than commercial agglutination antigen and is expected to be a valuable tool in the diagnosis of the epidemiology of Salmonella Pullorum.

Increasing Frequencies of Antibiotic Resistant Non-typhoidal Salmonella Infections in Michigan and Risk Factors for Disease

Non-typhoidal Salmonella (NTS) are important enteric pathogens causing over 1 million foodborne illnesses in the U.S. annually. The widespread emergence of antibiotic resistance in NTS isolates has limited the availability of antibiotics that can be used for therapy. Since Michigan is not part of the FoodNet surveillance system, few studies have quantified antibiotic resistance frequencies and identified risk factors for NTS infections in the state. We obtained 198 clinical NTS isolates via active surveillance at four Michigan hospitals from 2011 to 2014 for classification of serovars and susceptibility to 24 antibiotics using broth microdilution. The 198 isolates belonged to 35 different serovars with Enteritidis (36.9%) predominating followed by Typhimurium (19.5%) and Newport (9.7%), though the proportion of each varied by year, residence, and season. The number of Enteritidis and Typhimurium cases was higher in the summer, while Enteritidis cases were significantly more common among urban vs. rural residents. A total of 30 (15.2%) NTS isolates were resistant to ≥1 antibiotic and 15 (7.5%) were resistant to ≥3 antimicrobial classes; a significantly greater proportion of Typhimurium isolates were resistant compared to Enteritidis isolates and an increasing trend in the frequency of tetracycline resistance and multidrug resistance was observed over the 4-year period. Resistant infections were associated with longer hospital stays as the mean stay was 5.9 days for patients with resistant isolates relative to 4.0 days for patients infected with susceptible isolates. Multinomial logistic regression indicated that infection with serovars other than Enteritidis [Odds ratio (OR): 3.8, 95% confidence interval (CI): 1.23-11.82] as well as infection during the fall (OR: 3.0; 95% CI: 1.22-7.60) were independently associated with resistance. Together, these findings demonstrate the importance of surveillance, monitoring resistance frequencies, and identifying risk factors that can aid in the development of new prevention strategies.

Prevalence and antimicrobial resistance patterns of Salmonella isolated from poultry farms in southeastern United States

Salmonella spp. are among the most common foodborne pathogens, and increase in the occurrence of antimicrobial drug-resistant Salmonella poses a severe risk to public health. The main objective of this study was to determine changes in Salmonella prevalence and their antimicrobial resistance on poultry farms following recommendations to changes in biosecurity practices. Four poultry farms were sampled by collecting cloacal swabs, drag swabs, and litter samples prior to recommended biosecurity changes (March-April) and post recommendations (October-November). Prevalence of Salmonella was 3 to 4% during pre-recommendations, while the prevalence was higher (P > 0.05), ranging from 5 to 14% during post recommendations. Higher Salmonella prevalence was observed for pre- and post-recommendation phases by sample type in cloacal and drag samples -5% for farm 1, drag swab -6% on farm 2, cloacal swab -6% for farm 3, and drag swab -17% on farm 4. The PCR confirmed Salmonella were serotyped and tested for antimicrobial resistance. Six serotypes of Salmonella were identified with S. Enteritidis (52%) being the most prevalent, followed by S. Berta (38%), S. Mbandaka (7%), S. Typhimurium (2%), S. Kentucky (0.4%), and S. Tennessee (0.4%). A total of 7% isolates exhibited resistance to at least one of the 8 antimicrobials. Higher resistance was observed for tetracycline, streptomycin, and nalidixic acid. A single isolate of S. Mbandaka exhibited multidrug resistance to tetracycline, amoxicillin/clavulanic acid, and ampicillin. Based on these prevalence results, it can be inferred that, irrespective of implementation of improved biosecurity practices, seasonal variation can cause changes in the prevalence of Salmonella on the farms. Resistance to clinically important antimicrobials used to treat salmonellosis is a concern to public health.

Population dynamics and antimicrobial resistance of the most prevalent poultry-associated Salmonella serotypes

Salmonella spp. is the most predominant bacterial cause of foodborne gastroenteritis in humans. Due to the risk of human infection associated with poultry products and the prevalence of antimicrobial resistance, Salmonella also poses a significant challenge to commercial poultry production. During the last decade (2002 to 2012), the 12 most prevalent poultry-associated Salmonella serotypes (MPPSTs) were frequently and consistently isolated from poultry products in the United States. These MPPSTs and their percent prevalence in poultry products include Kentucky (4%), Enteritidis (2%) Heidelberg (2%), Typhimurium (2%), S. I 4,[5],12:i:- (0.31%), Montevideo (0.20%), Infantis (0.16%) Schwarzengrund (0.15%), Hadar (0.15%), Mbandaka (0.13%), Thompson (0.12%), and Senftenberg (0.04%). All MPPSTs except Kentucky are among the top 30 clinically significant serotypes that cause human illnesses in the United States. However with the exception of a few widely studied serotypes such as S. Enteritidis and Typhimurium, the ecology and epidemiology of the majority of MPPSTs still remain poorly investigated. Published data from the United States suggests that MPPSTs such as Heidelberg, Typhimurium, Kentucky, and Sentfenberg are more likely to be multi-drug resistant (MDR, ≥3 antimicobial classes) whereas Enteritidis, Montevideo, Schwarzengrund, Hadar, Infantis, Thompson, and Mbandaka are generally pan-susceptible or display resistance to fewer antimicobials. In contrast, the majority of MPPSTs isolated globally have been reported to display MDR phenotype. There also appears to be an international spread of a few MDR serotypes including Kentucky, Schwarzengrund, Hadar, Thomson, Sentfenberg, and Enteritidis, which may pose significant challenges to the public health. The current knowledge gaps on the ecology, epidemiology, and antimicrobial resistance of MPPSTs are discussed.

Salmonella Thompson outbreak associated with consumption of chicken shawarma and the usefulness of genome sequencing in the investigation

Background

A sudden increase in Salmonella Thompson (S. Thompson) cases distributed throughout three border regions in the province of Quebec in November 2016 triggered a provincial investigation to identify a common source of contamination and to put the appropriate control measures into place.

Objective

To report on the outbreak and to describe the use of genomic sequencing to identify the salmonella serotype responsible.

Methods

A descriptive survey of all reported cases of Salmonella serogroup C1 that had occurred between October 1, 2016 and February 15, 2017 was conducted. A case definition was developed. Pulsed field gel electrophoresis supplemented by analyses of genome sequences using the single nucleotide variant phylogenomics method were used to demarcate and manage the outbreak.

Results

Eighteen cases of S. Thompson were identified through whole genome sequencing. The onset dates of symptoms for the 16 cases that presented enteric symptoms were November 21-December 2, 2016. Two cases that presented with atypical symptoms were not reported until February 2017. Among the 18 cases, 16 had eaten or probably eaten chicken shawarma at the same restaurant chain and nine of these cases ate it at the same restaurant. In total, five restaurants from this chain, spread throughout three border regions of Quebec, were identified.

Conclusion

Outbreaks associated with chicken shawarma have been identified in the past. Efforts must be made to ensure that the owners of this type of restaurant know the contamination risk associated with this type of cooking and take the necessary steps to reduce this risk. The use of the genome sequencing method was very useful in defining the outbreak.

Prevalence and Antimicrobial Resistance of Salmonella enterica Serovar Indiana in China (1984-2016)

Salmonella enterica serovar Indiana, first described in 1955, is generally regarded as having a low frequency worldwide with outbreaks of gastroenteritis and abortions described in North America and Europe. In China, S. Indiana was first reported in 1984 and in the subsequent 71 surveys in 35 cities/municipalities from 18 provinces, 70% of which were after 2012, S. Indiana has been shown to have become widely prevalent in people, animals, food and the environment around abattoirs and meat processing facilities. The organism is now one of the most common serovars found in livestock and raw meat in China with S. Indiana isolates having high levels of drug resistance, especially against tetracyclines, quinolones, folate pathway inhibitors, phenicols, penicillins, monobactams and nitrofurans. Further, S. Indiana isolates that are concurrently resistant to ciprofloxacin and ceftriaxone/cefotaxime have emerged. Studies have suggested the high levels of multidrug resistance of S. Indiana might be associated with the presence of class 1 integrons and plasmids. Unfortunately, information on the high prevalence of S. Indiana and its extensive drug resistance in China has largely escaped international recognition as it largely appears in local reports written in Chinese. To address this situation, we reviewed all the available local Chinese and international publications on the organism in China and report our findings in this review.

Characterization of Resistance Genes and Plasmids from Outbreaks and Illness Clusters Caused by Salmonella Resistant to Ceftriaxone in the United States, 2011-2012

Salmonella is an important cause of foodborne illness; however, quickly identifying the source of these infections can be difficult, and source identification is a crucial step in preventing additional illnesses. Although most infections are self-limited, invasive salmonellosis may require antimicrobial treatment. Ceftriaxone, an extended-spectrum cephalosporin, is commonly used for treatment of salmonellosis. Previous studies have identified a correlation between the food animal/retail meat source of ceftriaxone-resistant Salmonella and the type of resistance gene and plasmid it carries. In this study, we examined seven outbreaks of ceftriaxone-resistant Salmonella infections, caused by serotypes Typhimurium, Newport, Heidelberg, and Infantis. All isolates were positive for a plasmid-encoded bla_CMY gene. Plasmid incompatibility typing identified five IncI1 and two IncA/C plasmids. Both outbreaks containing bla_CMY-IncA/C plasmids were linked to consumption of cattle products. Three of five outbreaks with bla_CMY-IncI1 (ST12) plasmids were linked to a poultry source. The remaining IncI1 outbreaks were associated with ground beef (ST20) and tomatoes (ST12). In addition, we examined isolates from five unsolved clusters of ceftriaxone-resistant Salmonella infections and used our plasmid-encoded gene findings to predict the source. Overall, we identified a likely association between the source of ceftriaxone-resistant Salmonella outbreaks and the type of resistance gene/plasmid it carries.

Tissue colonization and circulating T lymphocytes in laying hens upon oral challenge with Salmonella enterica serovars

Evaluating the potential of Salmonella serovars for tissue colonization and egg contamination in laying hens is critical due to widespread consumption of poultry and egg-containing products. The 2009 FDA Egg Rule was implemented to target the eradication of Salmonella enterica Enteritidis (SE) from layers; however, other Salmonella serovars, such as Heidelberg (SH) and Typhimurium (ST), have also been associated with poultry-related outbreaks. We conducted this study to see if serovars other than SE could colonize in laying hens, cause egg contamination, and modulate circulating T-cell populations. Laying hens were orally gavaged with 10⁷ colony forming units (CFU) of SE, SH, or ST and assessed for colonization in spleen, ovaries, and oviduct 10 d postchallenge. Splenic colonization was similar for all the serovars; however, colonization of ovaries and oviducts was significantly higher with SH compared to SE and ST. Furthermore, SH challenge resulted in egg contamination, while SE and ST did not result in contaminated eggs. Phenotypic evaluation of peripheral blood lymphocytes showed significant reduction in CD4 cells in SH-challenged birds and lower CD8α and CD8β cells in SE-challenged birds compared to controls. Our data showed that non-SE serovars have equal or higher potential to colonize reproductive tissues of laying hens and may be accompanied by altered lymphocyte populations.

Immortalization of Fetal Bovine Colon Epithelial Cells by Expression of Human Cyclin D1, Mutant Cyclin Dependent Kinase 4, and Telomerase Reverse Transcriptase: An In Vitro Model for Bacterial Infection

Cattle are the economically important animals in human society. They are essential for the production of livestock products such as milk and meats. The production efficiency of livestock products is negatively impacted by infection with zoonotic pathogens. To prevent and control infectious diseases, it is important to understand the interaction between cattle tissue and pathogenic bacteria. In this study, we established an in vitro infection model of an immortalized bovine colon-derived epithelial cell line by transducing the cells with lentiviral vectors containing genes encoding cell cycle regulators cyclin D1, mutant cyclin dependent kinase 4 (CDK4), and human telomerase reverse transcriptase (TERT). The established cell line showed continuous cell proliferation, expression of epithelial markers, and an intact karyotype, indicating that the cells maintained their original nature as colon-derived epithelium. Furthermore, we exposed the established cell line to two strains of Salmonella enterica and EHEC. Interestingly, S. Typhimurium showed higher affinity for the established cell line and invaded the cytoplasm than S. Enteritidis. Quantitative RT-PCR revealed that gene expression of Toll-like receptor 1 (TLR1), TLR 2 and TLR 3, whereas TLR 4, 5 and 6 were not detectable in established cells. Our established immortalized colon-derived epithelial cell should be a useful tool for studies evaluating the molecular mechanisms underlying bacterial infection.

Prevalence and Serogroup Diversity of Salmonella for Broiler Neck Skin, Whole Carcass Rinse, and Whole Carcass Enrichment Sampling Methodologies following Air or Immersion Chilling

The purpose of this study was to evaluate neck skin (NS), whole carcass rinse (WCR), and whole carcass enrichment (WCE) sampling procedures for Salmonella isolation and serogroup identification from the same broiler chicken carcass treated with air or immersion chilling. Commercially processed and eviscerated broiler carcasses were collected from a commercial processing plant, individually bagged, and transported to the pilot processing plant. In experiment 1, carcasses were air chilled to 4°C. In experiment 2, carcasses were immersion chilled with or without chlorine. After air chilling, Salmonella was detected on 78% of NS and 89% of WCE samples. Only one Salmonella serogroup was detected from each of 13 Salmonella-positive NS samples, and two serogroups were detected on 1 Salmonella-positive NS sample. Only one Salmonella serogroup was detected from each of 13 Salmonella-positive WCE samples, and two serogroups were detected from 3 Salmonella-positive WCE samples. After immersion chilling without chlorine, Salmonella was detected on 38% of NS, 45% of WCR, and 100% of WCE samples. Without chlorine, the 15 Salmonella-positive NS samples included 14 samples with one serogroup and 1 sample with two serogroups. Only one Salmonella serogroup was detected from WCR samples after immersion chilling. Of 40 Salmonella-positive WCE samples, 23 had a one, 14 had two, and 3 had three Salmonella serogroups. After immersion chilling with chlorine, Salmonella was detected on 35% of NS, 0% of WCR, and 90% of WCE samples. With chlorine, the 14 Salmonella-positive NS samples included 11 samples with one serogroup and 3 samples with two serogroups. No Salmonella serogroups were detected from WCR samples after immersion chilling with 20 mg/liter free chlorine. The 36 Salmonella-positive WCE samples included 21 samples with one serogroup and 15 samples with two serogroups. NS and WCE sampling methodologies yielded similar prevalence and serogroup diversity after air chilling. However, after immersion chilling with or without chlorine, WCE sampling yielded significantly higher (α ≤ 0.05) prevalence and serogroup diversity than either NS or WCR sampling methodologies.

Genetic characterisation of multidrug-resistant Salmonella enterica serotypes isolated from poultry in Cairo, Egypt

Background

Food-borne diseases pose serious health problems, affecting public health and economic development worldwide.

Methods

Salmonella was isolated from samples of chicken parts, skin samples of whole chicken carcasses, raw egg yolks, eggshells and chicken faeces. Resulting isolates were characterised by serogrouping, serotyping, antimicrobial susceptibility testing and detection of extended-spectrum β-lactamase (ESBL) production. Antibiotic resistance genes and integrons were identified by polymerase chain reaction (PCR).

Results

The detection rates of Salmonella were 60%, 64% and 62% in chicken parts, skin, and faeces, respectively, whereas the egg yolks and eggshells were uniformly negative. Salmonella Kentucky and S. Enteritidis serotypes comprised 43.6% and 2.6% of the isolates, respectively, whilst S. Typhimurium was absent. Variable resistance rates were observed against 16 antibiotics; 97% were resistant to sulfamethoxazole, 96% to nalidixic acid and tetracycline and 76% to ampicillin. Multidrug resistance was detected in 82% (64/78) of the isolates and ESBL production was detected in 8% (6/78). The β-lactamase blaTEM-1 gene was detected in 57.6% and blaSHV-1 in 6.8% of the isolates, whilst the blaOXA gene was absent. The sul1 gene was detected in 97.3% and the sul2 gene in 5.3% of the isolates. Sixty-four of the 78 isolates (82%) were positive for the integrase gene (int I) from class 1 integrons, whilst int II was absent.

Conclusion

This study reveals the presence of an alarming number of multidrug-resistant Salmonella isolates in the local poultry markets in Cairo. The high levels of drug resistance suggest an emerging problem that could impact negatively on efforts to prevent and treat poultry and poultry-transmitted human diseases in Egypt.

Salmonella enterica: survival, colonization, and virulence differences among serovars

Data indicate that prevalence of specific serovars of Salmonella enterica in human foodborne illness is not correlated with their prevalence in feed. Given that feed is a suboptimal environment for S. enterica, it appears that survival in poultry feed may be an independent factor unrelated to virulence of specific serovars of Salmonella. Additionally, S. enterica serovars appear to have different host specificity and the ability to cause disease in those hosts is also serovar dependent. These differences among the serovars may be related to gene presence or absence and expression levels of those genes. With a better understanding of serovar specificity, mitigation methods can be implemented to control Salmonella at preharvest and postharvest levels.

Prevalence of salmonella in neck skin and bone of chickens

Bone-in and boneless parts, such as drumsticks, are used in ground chicken production. In addition, neck skin is used as a source of fat in ground products. Contaminated chicken neck skin and bones containing internalized Salmonella are potential sources of this pathogen in ground chicken. This study determined the prevalence of Salmonella and serotype distribution in drumstick bones and neck skin of postchill chicken carcasses. One week prior to slaughter, chicken houses (n = 26) at nine farms were tested for the presence of Salmonella, using the boot sock method. Chicken flocks from these houses originated from Salmonella-positive breeders. Eight Salmonella-positive chicken flocks and one flock with undetermined Salmonella status were monitored through processing. Three hundred postchill drumsticks and 299 neck skin samples were analyzed for Salmonella prevalence. Skin samples were rinsed and stomached prior to analysis. Bones were extracted from the drumsticks, external surfaces were sterilized, and bones were crushed for analysis. One Salmonella isolate from each positive sample was serogrouped. Half of the isolates representing different sample types were serotyped. Overall, Salmonella was found in 0.8, 21.4, and 80.1% of bone marrow, neck skin, and farms, respectively. Prevalence of Salmonella on rinsed skin samples (2.3%) and stomached skin samples (20.7%) differed significantly (P ≤ 0.05). Serogroups B, C2, D, and E were found at 23.4, 31.9, 11.7, and 29.8%, respectively. Six Salmonella serotypes were identified: Liverpool (37.9%), Kentucky (27.6%), and Typhimurium (27.6%) were isolated most frequently from neck skin; the two bone isolates were Kentucky; and more than 50% of the farm isolates were Kentucky and Ouakam. Salmonella-contaminated neck skin might be a more significant source of this contamination in ground chicken than Salmonella internalized in bones.

Prevalence of Salmonella spp. in Packed and Unpacked Red Meat and Chicken in South of Tehran

Background:

Despite of the advances in infectious diseases prevention and food technology, food-borne diseases are considered major problems in developed and developing countries. Meat plays a key role in transferring zoonotic diseases to human.

Objectives:

This study was conducted in south of Tehran, Iran, to investigate the prevalence rate of Salmonella spp. in packed and unpacked red meat and chicken.

Materials and Methods:

A total of 379 packed and unpacked samples including 189 red meat and 190 chicken samples were collected randomly. From each sample, 25 g was separated and treated with 225 mL of buffered peptone water, homogenized and incubated at 37°C for 24 hours. Samples were enriched using Rappaport-Vassiliadis broth and then streaked onto Hektoen enteric agar.

Results:

Totally, 86 out of 190 chicken and 38 out of 189 red meat samples were contaminated with Salmonella spp. The most isolated serotypes were Salmonella thompson (67.7%), S. heaardt (6.5%), S. enteritidis (4.8%), and S. veyle (4%), respectively. In general, the rate of chicken contamination was higher than meat, as 43.3% of packed and 46% of unpacked chicken samples were contaminated.

Conclusions:

These results confirmed the pervious findings, stating that proper packaging of meat products can effectively decreases the rate of microbial contaminations.

Salmonella pathogenicity and host adaptation in chicken-associated serovars

Enteric pathogens such as Salmonella enterica cause significant morbidity and mortality. S. enterica serovars are a diverse group of pathogens that have evolved to survive in a wide range of environments and across multiple hosts. S. enterica serovars such as S. Typhi, S. Dublin, and S. Gallinarum have a restricted host range, in which they are typically associated with one or a few host species, while S. Enteritidis and S. Typhimurium have broad host ranges. This review examines how S. enterica has evolved through adaptation to different host environments, especially as related to the chicken host, and continues to be an important human pathogen. Several factors impact host range, and these include the acquisition of genes via horizontal gene transfer with plasmids, transposons, and phages, which can potentially expand host range, and the loss of genes or their function, which would reduce the range of hosts that the organism can infect. S. Gallinarum, with a limited host range, has a large number of pseudogenes in its genome compared to broader-host-range serovars. S. enterica serovars such as S. Kentucky and S. Heidelberg also often have plasmids that may help them colonize poultry more efficiently. The ability to colonize different hosts also involves interactions with the host's immune system and commensal organisms that are present. Thus, the factors that impact the ability of Salmonella to colonize a particular host species, such as chickens, are complex and multifactorial, involving the host, the pathogen, and extrinsic pressures. It is the interplay of these factors which leads to the differences in host ranges that we observe today.

Landscape and seasonal factors influence Salmonella and Campylobacter prevalence in a rural mixed use watershed

Salmonella and Campylobacter prevalence in stream networks of the Satilla River Basin (SRB) were monitored monthly from August 2007 to August 2009 to study relationships between these pathogens and land use, presence of poultry houses and wastewater treatment plant (WWTP) discharge. Salmonella and Campylobacter were detected at all 10 stream sites and the three sites at the sole wastewater treatment plant (WWTP) in the study area. In all, 43% (129/299) and 62% (96/156) of samples were positive for Salmonella and Campylobacter, respectively, with detection frequency increasing in downstream sites with more poultry production and influence of WWTP discharge. Both Salmonella and Campylobacter detection frequencies were positively associated with the number of poultry houses in the subwatersheds, but agricultural land use as a proportion of the watershed was not a significant predictor of either pathogen. Fecal indicator bacterial levels were assessed and evaluated for their ability to predict the presence of pathogens. Of those examined, enterococci was most predictive; of the 129 samples positive for Salmonella, 88% (113/129) were detected when enterococci were above EPA single sample threshold (61 CFU 100 ml(-1)); and of the 96 samples positive for Campylobacter, 90% (86/96) were detected when enterococci levels exceeded this level. Comparatively, Escherichia coli concentrations were above EPA single sample thresholds in 38% (49/129) of the positive Salmonella samples. Detection of the pathogens throughout the watershed indicated that there was potential for waterborne transmission especially in downstream areas that were more likely to have recreational users.

A Review of the Use of Organic Amendments and the Risk to Human Health

Historically, organic amendments—organic wastes—have been the main source of plant nutrients, especially N. Their use allows better management of often-finite resources to counter changes in soils that result from essential practices for crop production. Organic amendments provide macro- and micronutrients, including carbon for the restoration of soil physical and chemical properties. Challenges from the use of organic amendments arise from the presence of heavy metals and the inability to control the transformations required to convert the organic forms of N and P into the minerals available to crops, and particularly to minimize the losses of these nutrients in forms that may present a threat to human health. Animal manure and sewage biosolids, the organic amendments in greatest abundance, contain components that can be hazardous to human health, other animals and plants. Pathogens pose an immediate threat. Antibiotics, other pharmaceuticals and naturally produced hormones may pose a threat if they increase the number of zoonotic disease organisms that are resistant to multiple antimicrobial drugs or interfere with reproductive processes. Some approaches aimed at limiting N losses (e.g. covered liquid or slurry storage, rapid incorporation into the soil, timing applications to minimize delay before plant uptake) also tend to favor survival of pathogens. Risks to human health, through the food chain and drinking water, from the pathogens, antibiotics and hormonal substances that may be present in organic amendments can be reduced by treatment before land application, such as in the case of sewage biosolids. Other sources, such as livestock and poultry manures, are largely managed by ensuring that they are applied at the rate, time and place most appropriate to the crops and soils. A more holistic approach to management is required as intensification of agriculture increases.

Development and validation of a drag swab method using tampons and different diluents for the detection of members of Salmonella in broiler houses

Members of the genus Salmonella represent a significant public health concern and also a colonizer of commercial poultry. Therefore, the early detection and management of colonized broiler breeders and their progeny is essential. There have been numerous methods for farm-based detection, with gauze-based drag swabs being the most commonly used. In the present study, the wet (boiled water, buffered peptone water and double-strength skin milk) tampon was compared with the gauze to determine the recovery rate (10(2) colony-forming units/swab) of five common poultry serovars of Salmonella and after cold (4°C/48 h) storage. The recovery was found to be equivalent when tested using the ISO6572:2002 method, for all diluents (Cohen's κ =1.0; sensitivity = 1.0; specificity = 1.0). The subsequent field trial (n = 15 farms) compared the tampon drag swab (TDS) with a statistically appropriate (90% confidence, detect 10% prevalence) number of faecal swabs (n = 22), which also showed high agreement between the TDS and faecal sampling (κ = 0.86; McNemar's χ(2) = 1.0; sensitivity = 0.9; specificity = 1.0). However, direct faecal sampling showed a wider diversity of serovars of Salmonella than the corresponding TDS. The TDS is a very sensitive, readily available and cost-effective screening method for salmonellas in broiler breeder houses. This TDS technique may be used for routinely screening of broiler houses, and faecal sampling would only be used to confirm colonization or contamination, and to measure flock serovar variance.

Horizontal gene transfer of a ColV plasmid has resulted in a dominant avian clonal type of Salmonella enterica serovar Kentucky

Salmonella enterica continues to be a significant cause of foodborne gastrointestinal illness in humans. A wide variety of Salmonella serovars have been isolated from production birds and from retail poultry meat. Recently, though, S. enterica subsp. enterica serovar Kentucky has emerged as one of the prominent Salmonella serovars isolated from broiler chickens. Recent work suggests that its emergence apparently coincides with its acquisition of a ColV virulence plasmid. In the present study, we examined 902 Salmonella isolates belonging to 59 different serovars for the presence of this plasmid. Of the serovars examined, the ColV plasmid was found only among isolates belonging to the serovars Kentucky (72.9%), Typhimurium (15.0%) and Heidelberg (1.7%). We demonstrated that a single PFGE clonal type of S. Kentucky harbors this plasmid, and acquisition of this plasmid by S. Kentucky significantly increased its ability to colonize the chicken cecum and cause extraintestinal disease. Comparison of the completed sequences of three ColV plasmids from S. Kentucky isolated from different geographical locales, timepoints and sources revealed a nearly identical genetic structure with few single nucleotide changes or insertions/deletions. Overall, it appears that the ColV plasmid was recently acquired by a single clonal type S. Kentucky and confers to its host enhanced colonization and fitness capabilities. Thus, the potential for horizontal gene transfer of virulence and fitness factors to Salmonella from other enteric bacteria exists in poultry, representing a potential human health hazard.

Nationwide survey of salmonella prevalence in environmental dust from layer farms in Japan

A nationwide survey was conducted to determine Salmonella prevalence in airborne dust from layer farms. Of the 4,090 layer farms in Japan, 203 were surveyed and 48 (23.6%) of these were positive for Salmonella. Salmonella isolation rates were higher in the eastern (24.3%), central (25.6%), western (23.9%), and southern (27.5%) prefectures than they were in the northern (13.3%) prefecture. We recovered 380 Salmonella isolates and identified 34 different Salmonella serovars. Salmonella Infantis was the most prevalent serovar (42 [11.1%] of 380), followed by Salmonella Agona (39 [10.3%] of 380), Salmonella Mbandaka (37 [9.7%] of 380), Salmonella Cerro (32 [8.4%] of 380), Salmonella Thompson (29 [7.6%] of 380), and Salmonella Braenderup (27 [7.1%] of 380). Of the 380 isolates, 273 (71.8%) were resistant to more than one antibiotic. Salmonella Infantis (41 [97.6%] of 42), Salmonella Agona (38 [97.4%] of 39), and Salmonella Mbandaka (34 [91.9%] of 37) showed the highest resistance rates. We found 18 different resistance patterns and the most common (179 [47.1%] of 273) was resistant to dihydrostreptomycin. One of the 13 Salmonella Hadar isolates was resistant to eight antibiotics. To investigate characteristics of Salmonella Agona, Salmonella Infantis, and Salmonella Mbandaka isolates across different prefectures, we performed pulsed-field gel electrophoresis by using XbaI and BlnI. The Salmonella Agona and Salmonella Mbandaka dendrograms were grouped into seven clusters, with 80 and 70% similarity, respectively. Because the Salmonella Infantis dendrogram showed low similarity, there is a possibility of genetic diffusion of this serovar across Japan. This report is the first to describe Salmonella contamination in airborne dust from layer farms in Japan. Our findings should be useful for future Salmonella infection monitoring and control.

Risk factors associated withSalmonella entericasubsp.entericacontamination of chicken carcases in Senegal

The objective of this study was to identify the risk factors for Salmonella spp. contamination of Senegalese chicken carcases during slaughtering. One hundred and twenty traditional slaughterhouses were studied from January 2000 to December 2002 in and around Dakar. A questionnaire was administered to the slaughterers and samples of breast skin were taken to assess the Salmonella spp. status of chicken carcases. Results showed that 43.3% of the chicken batches were contaminated with Salmonella spp., with Salmonella Hadar and Salmonella Brancaster as the two main serovars. Salmonella spp. contamination of the live birds before slaughtering was related to contamination of the carcases after slaughtering. Feed withdrawal before slaughtering and thorough cleaning and disinfection procedures decreased the risk of Salmonella contamination. One individual worker for each slaughtering stage was also associated with a decreased risk of Salmonella contamination. Using scalding water for plucking increased the risk of contamination. These results will help slaughterers to produce safer products for local consumers.

Serotype, genotype, and antimicrobial susceptibility profiles of Salmonella from chicken farms in Shanghai

Five hundred fifty samples were collected from five chicken farms in Shanghai during March 2005 to October 2006. Twenty-five samples tested positive for Salmonella from a total of 550 samples, of which 500 were obtained from feces of healthy chickens and 50 were obtained from diseased chicks. The 25 presumptive Salmonella isolates were confirmed by the API 20E identification kit. Serotyping of these isolates by agglutination tests with antiserum displayed seven serovars; genotyping of these isolates with multilocus sequence typing demonstrated six sequence type (ST) patterns (i.e., ST-11, ST-19, ST-92, ST-96, ST-290, and ST-367). The multilocus sequence typing data revealed that some of these strains, isolated from different farms, might have the same ST and might come from the same source. The susceptibilities of these strains to 14 antimicrobials were determined; most of the isolates (13 of 25) were resistant to doxycycline and tetracycline, and two isolates were resistant to cefotaxime and ceftazidime, but none was resistant to gentamicin or kanamycin.

Effect of citric acid, avilamycin, and their combination on the performance, tibia ash, and immune status of broilers

The aim of this study was to determine the effect of the supplementation of an organic acid (citric acid), antibiotic growth promoter (avilamycin), and their combination for a period of 35 d on the growth, feed efficiency, carcass yield, tibia ash, and immune status of broilers. One hundred sixty 1-d-old broiler chicks (Hubbard Classic) were randomly distributed into 4 groups with 4 replicate cages having 10 birds in each. A corn-soybean-based diet was used as the basal diet (control). The basal diet was supplemented with an organic acid (citric acid, 0.5%), an antibiotic growth promoter (avilamycin, 0.001%), and their combination in other groups. The highest BW was attained in citric acid-fed chicks (1,318 g), which was significantly (P < 0.05) higher than control chicks (1,094 g) or avilamycin-fed chicks (1,217 g). The combination-fed chicks showed similar weight (1,246 g) as citric acid- or avilamycin-fed chicks (P > 0.05). Total feed intake was higher in citric acid-fed chicks compared with antibiotic-supplemented chicks. The addition of citric acid improved feed conversion efficiency (g of weight gain/ kg of feed intake) significantly (P < 0.05) compared with control chicks or its combination with avilamycin. Higher carcass weights were found in chicks fed the combination diet. Supplementation of citric acid increased tibia ash percentage significantly (P < 0.05) compared with controls. Addition of citric acid reduced the pH of the formulated diets. An improvement of immune status was detected by densely populated immunocompetent cells in the lamina propria and submucosa of cecal tonsils and ileum and also in the cortex and medulla of bursa follicles in citric acid-supplemented chicks. Supplementation of citric acid at 0.5% in the diet had positive effects on growth, feed intake, feed efficiency, carcass yield, bone ash, and immune status of broilers. Therefore, citric acid might be a useful additive instead of antibiotic growth promoters such as avilamycin, considering performance and health status of broilers.

Food contamination with salmonella species in the Republic of Macedonia

OBJECTIVES

To evaluate contamination with Salmonella of food products from food markets in the Republic of Macedonia by assessment of the most frequently contaminated food products and the most frequently isolated serotypes of Salmonella.

METHODS

This is a retrospective study analyzing data from the national database for microbiological safety of food products for the period from 2003 to 2005 as well as a prospective study for 2006 and 2007. Isolation and identification of Salmonella spp. were performed in the Laboratory for Sanitary Microbiology of the Republic Institute for Health Protection in Skopje, Macedonia. All samples were tested using the horizontal method for detection of Salmonella spp., according to ISO 6579:2002. Two immunological methods were used: Singlepath and VIDAS Salmonella spp. in food.

RESULTS

Presence of Salmonella spp. was 0.04-0.06% during 2003-2005, 0.63% in 2006, and 0.39% in 2007. During the period 2003 to 2005, Salmonella spp. were most frequently isolated from meat and meat products (75%), followed by milk and dairy products. In 2006 and 2007, the most frequently contaminated food products were mechanically separated chicken meat (71% in 2006 and 75% in 2007). The most frequent serogroups of Salmonella spp. in 2006 were C(1) (47%), followed by B and D (17.6%), and F (11.7%). In 2007, the most frequent serogroups of Salmonella spp. were C(1) (50%), followed by D (20%), E(3) (15%), and B (10%).

CONCLUSIONS

We found an increasing trend in the contamination level of food products with Salmonella spp., especially in 2006 and 2007, in which the most frequently contaminated food products were mechanically separated chicken meat, milk, dairy products, and sweets, and the most frequently isolated serogroup was C(1).

Fecal indicator bacteria and Salmonella in ponds managed as bird habitat, San Francisco Bay, California, USA

Throughout the world, coastal resource managers are encouraging the restoration of previously modified coastal habitats back into wetlands and managed ponds for their ecosystem value. Because many coastal wetlands are adjacent to urban centers and waters used for human recreation, it is important to understand how wildlife can affect water quality. We measured fecal indicator bacteria (FIB) concentrations, presence/absence of Salmonella, bird abundance, and physico-chemical parameters in two coastal, managed ponds and adjacent sloughs for 4 weeks during the summer and winter in 2006. We characterized the microbial water quality in these waters relative to state water-quality standards and examined the relationship between FIB, bird abundance, and physico-chemical parameters. A box model approach was utilized to determine the net source or sink of FIB in the ponds during the study periods. FIB concentrations often exceeded state standards, particularly in the summer, and microbial water quality in the sloughs was generally lower than in ponds during both seasons. Specifically, the inflow of water from the sloughs to the ponds during the summer, more so than waterfowl use, appeared to increase the FIB concentrations in the ponds. The box model results suggested that the ponds served as net wetland sources and sinks for FIB, and high bird abundances in the winter likely contributed to net winter source terms for two of the three FIB in both ponds. Eight serovars of the human pathogen Salmonella were isolated from slough and pond waters, although the source of the pathogen to these wetlands was not identified. Thus, it appeared that factors other than bird abundance were most important in modulating FIB concentrations in these ponds.

Prevalence and antimicrobial resistance of Salmonella recovered from processed poultry

This study was conducted to determine the prevalence and antimicrobial resistance of Salmonella isolates recovered from processed poultry. Four hundred eighty pre- and postchill whole broiler chicken carcasses were collected from a poultry processing plant between July 2004 and June 2005. Water samples also were collected at the entrance and exit of the chiller. After preenrichment, carcass and water samples were analyzed for the presence of Salmonella using the automated BAX system followed by traditional culture methods. The proportions of pre- and postchill carcasses that were positive for Salmonella were 88.4 and 84.1%, respectively. Ninety-two percent of water samples collected at the entrance of the chiller were positive for Salmonella, but all exit samples were negative. There was no significant difference in the prevalence of Salmonella between pre- and postchill carcasses (P > 0.05). Salmonella isolates recovered were serotyped and tested for susceptibility to antimicrobials. Thirteen serotypes were identified; the most common were Salmonella Kentucky (59.5%) and Salmonella Typhimurium (17.8%). Three hundred thirty-nine (79.8%) of the isolates were resistant to at least one antimicrobial, and 53.4% were resistant to three or more antimicrobials. Resistance was most often observed to tetracycline (73.4% of isolates), ampicillin (52.9%), amoxicillin-clavulanic acid (52%), ceftiofur (51.7%), streptomycin (35.2%), and sulfisoxazole (21.8%). These results indicate the high prevalence of Salmonella contamination in whole broiler carcasses, and a large number of these Salmonella isolates were resistant to commonly used antimicrobials.

Excess salmonellosis in women in the United States: 1968-2000

We describe recent epidemiological changes in salmonellosis. Linking 1968-2000 National Salmonella Surveillance System to census data, we calculated population-based age- and sex-stratified rates of non-urinary salmonellosis for the top 30 non-typhoidal serotypes. Using 1996-1997, 1998-1999, and 2000-2001 population-based FoodNet surveys, we compared reported diarrhoea, medical visits, and stool cultures. Despite an overall female-to-male incidence rate ratio (FMRR) of 0.99, the sex-specific burden of salmonellosis varied by age (<5 years FMRR 0.92; 5-19 years 0.85; 20-39 years 1.09; 40-59 years 1.23, and 60 years 1.08) and serotype (FMRR range 0.87 for Mississippi to 1.25 for Senftenberg). Serotype-specific FMRRs and median age (range 2 years for Derby to 29 years for Senftenberg) were related (correlation 0.76, P<0.0001). Recently, the relative burden of salmonellosis in women has increased. FoodNet data suggest that this change is real rather than due to differential reporting. Excess salmonellosis in women may reflect differences in exposure or biological susceptibility.

Genotypes, serotypes, and antibiotic resistance profiles of Salmonella isolated from commercial North Carolina turkey farms

This study was designed to determine the serotypes, genotypes, and antibiotic resistance (AbR) patterns of 42 Salmonella isolates recovered from either fecal or litter samples of 12 commercial turkey farms across two seasons (summer and winter) and two ages (3 and 19 weeks). Isolates were serotyped on the basis of the Kauffmann-White scheme. Genotyping was done by restriction digestion of cDNA (XbaI) and subsequent pulsed-field gel electrophoresis (PFGE). The AbR was determined with Sensititre susceptibility plates. Serovar Kentucky was the most prevalent serotype (26%), followed by Senftenberg (19%), Muenster (17%), Mbandaka (10%), Javiana (7%), Hadar (5%), Heidelberg (5%), 8,(20):nonmotile (5%), Agona (2%), Infantis (2%), and 4,12:r:-(2%). Serovars Kentucky, Heidelberg, Hadar, and 8,(20):nonmotile were isolated only from the 19-week-old bird samples, whereas Senftenberg and Muenster were isolated only from the young birds (3 weeks old). Isolates within any one serotype showed minor PFGE banding pattern differences, but dendogram analysis indicated that sequence variability between serotypes was more significant than within serotypes. Isolates were resistant to tetracycline (86%), sulfisoxazole (71%), streptomycin (64%), gentamicin (41%), ampicillin (36%), kanamycin (26%), sulfamethoxazole-trimethoprim (7%), nalidixic acid (5%), cefoxitin (2%), and ceftiofur (2%). One isolate (Muenster) was resistant to nine antibiotics (2%), and the others were resistant to six (7%), five (12%), four (10%), three (21%), two (24%), and one (10%) antibiotic. Only two isolates (5%) were susceptible to all antibiotics tested. The AbR patterns were affected by age; on average, strains recovered from young birds were resistant to more than four drugs compared with fewer than three in older birds (P < 0.05). This study showed that Salmonella enterica subsp. enterica serotypes, genotypes and AbR patterns were affected by bird age but not by season or farm.

A longitudinal study of Salmonella and Campylobacter jejuni isolates from day of hatch through processing by automated ribotyping

Comparisons of bacterial populations over long periods of time allow researchers to identify clonal populations, perhaps those responsible for contamination of farms or humans. Salmonella and Campylobacter can cause human illness, and our objective was to use a library typing system to track strains that persist in the poultry house and through the processing plant. Two farms, over four consecutive flocks, were studied. Multiple samples were taken of the poultry house environment, feed mill, transport crates, and carcasses in the processing plant. Sample collection on the farm took place on chick placement day, midgrowout, and the day of harvest. This study found that 80.3% of isolates belonged to a single strain of Salmonella Kentucky that persisted in several environmental samples for all flocks at both farms, from chick placement day to the final product at the plant. Surgical shoe covers produced most isolates (n = 26), and processing day yielded the highest recovery (n = 68). Additional serotypes were recovered, but the Salmonella Kentucky-positive eggshells and chick mortality appeared to be the source of the organism for both farms. All Campylobacter isolates recovered were identified as C. jejuni. Most Campylobacter isolates (90.1%) belonged to one of three core strains. C. jejuni was not recovered on chick placement day. Cecal droppings yielded all nine strains. Most isolates (98.2%) were from one farm. Cluster analysis grouped C. jejuni and Salmonella isolates into four and six distinct clusters, respectively, on the basis of a similarity level of 80%.

Presence of inoculated Campylobacter and Salmonella in unabsorbed yolks of male breeders raised as broilers

Day-old male broiler breeder chicks were obtained from a commercial hatchery and raised as broilers. For Experiment 1, at 5 wk of age, the broilers were orally inoculated with a 10(6) cfu/ml of a characterized strain of Campylobacter jejuni and a cocktail (three naladixic acid-resistant strains) of Salmonella serovars. One week after inoculation, the birds were euthanatized and defeathered. The abdominal cavity was examined and any unabsorbed yolk material (and remaining yolk stalk) and ceca were aseptically removed for microbiological analyses. For each pooled sample (two birds per pool), an aerobic plate count (APC), an Enterobacteriaceae (ENT) count, and a test for the presence of Campylobacter and Salmonella was performed. For Experiment 2, at 5 wk of age, the broilers were orally inoculated with 10(5) cfu/ml of a characterized strain of Campylobacter jejuni. One week after inoculation, the birds (n = 20) were killed, defeathered, and the yolk stalk, attached yolk, or free-floating yolk and ceca were individually analyzed for presence of Campylobacter. For Experiment 1, the Salmonella-inoculated birds had 2/12 ceca and 0/12 unabsorbed yolk samples positive for Salmonella. The average yolk APC was log10 3.4 cfu/g and the average ENT was log10 1.9 cfu/g. For the Campylobacter-inoculated birds, 12/12 ceca and 9/12 unabsorbed yolk samples were positive for Campylobacter. The average yolk APC was log10 3.5 cfu/g and the average ENT was log10 3.1 cfu/g. For Experiment 2, the inoculated Campylobacter birds had 19/20 ceca, 5/20 free floating yolks, and 19/20 yolk stalks positive. In Experiment 1, the inoculated Campylobacter colonized the ceca in every instance and were present in 75% of the unabsorbed yolks. Alternatively, the inoculated Salmonella were not found in any of the unabsorbed yolks and only rarely in the ceca. In Experiment 2, the inoculated Campylobacter was found in very high numbers in the yolk and internal body samples. Determining to what extent these internal bodies and unabsorbed yolks play in bacterial colonization and contamination of the birds at processing has not been determined. The next step will be to determine the incidence of unabsorbed yolks and presence of Campylobacter and Salmonella in these bodies of commercial broilers at processing.

The distribution of Salmonella serovars in chicken and humans in Lithuania

We studied serovars of Salmonella strains isolated from chicken and humans in Lithuania over the period from 2000 to 2004. Salmonella strains were isolated and identified according to the techniques recommended by International Organisation for Standardization (Microbiology of Food and Animal Feeding Stuff--Horizontal Method for the Detection of Salmonella, 1998, ISO, Geneva). The per cent of infected flocks with Salmonella in separate years was between 1.01% and 3.2% during the period of investigation. The contamination rate of broiler legs and breasts was higher (2.36% and 4.25%) than that of wings (0.82%). Eighteen serovars of Salmonella were identified from the total 300 isolated samples. The most prevalent serovars in chicken were Salmonella Enteritidis, Salmonella Infantis and Salmonella Typhimurium. Other serovars such as Salmonella Montevideo, Salmonella Djugu, Salmonella Isangi, Salmonella Bovismorbificans, Salmonella Mbankada, Salmonella Hadar were detected only in one to two samples. In general, similar serovars of Salmonella were found in humans and chicken (S. Enteritidis and S. Typhimurium), although distinct serovars were found only in humans or only in chicken. Analysis of the distribution of Salmonella serovars in humans during the seasons of the year indicated that the highest incidence of Salmonella was in Summer and in the beginning of Autumn. Analysis of the distribution of serovars during the study period indicated that there is a shift over time in both humans and chicken.

Risk factors associated with Salmonella enterica subsp. enterica contamination of chicken carcases in Senegal

This study was to identify the risk factors for Salmonella spp. contamination of Senegalese chicken carcases during slaughtering. One hundred and twenty traditional slaughterhouses were studied from January 2000 to December 2002 in and around Dakar. A questionnaire was answered by the slaughterers, and samples of breast skin were taken to assess the Salmonella status of chicken carcases. Results showed that 43.3% of the batches were contaminated with Salmonella, indicating Salmonella Hadar and Salmonella Brancaster as the two main serovars. Salmonella contamination of the carcases after slaughtering was related to contamination of the live birds. Feed withdrawal before slaughtering and thorough cleaning and disinfection procedures decreased the risk of contamination. One individual worker for each slaughtering stage was also associated with a decreasing risk of contamination. Using scalding water for plucking the chicken carcases increased contamination risk. These results will help slaughters to produce safer products for local consumers.