Detection and identification of salmonellas from poultry-related samples by PCR

Phenotypic and molecular characterisation of Salmonella spp. isolates in healthy poultry

1. Epidemiological surveillance of Salmonella spp. serves as a primary tool for maintaining the health of poultry flocks. Characterising circulating serotypes is crucial for implementing control and prevention measures. This study conducted phenotypic and molecular characterisation of S. enterica Pullorum, S. enterica Heidelberg, and S. enterica Corvalis isolated from broiler chickens during slaughtering.2. All strains were susceptible to gentamicin, neomycin and norfloxacin. However, resistance rates exceeded 50% for ciprofloxacin and tiamulin, irrespective of the serotype. Approximately 64% of strains were classified as multidrug-resistant, with S. enterica Heidelberg strains exhibiting significantly higher overall resistance. The isolates demonstrated the ability to adhere and produce biofilm at a minimum of three temperatures, with S. enterica Pullorum capable of biofilm production at all temperatures encountered during poultry rearing.3. Each strain possessed between two and seven different virulence-associated genes. Genetic similarity, as indicated by pulsed field gel electrophoresis, exceeded 90% for all three serotypes and strains were classified in the R5 ribotype by PCR, regardless of serotype. Sequencing revealed high similarity among all strains, with homology ranging from 99.61 to 100% and all were classified to a single cluster.4. The results suggested a clonal relationship among the strains, indicating the possible circulation of a unique clonal group of S. enterica Pullorum in the southern region of Brazil.

Prevalence and characteristics of ESBL-producing Escherichia coli in clinically healthy pigs: implications for antibiotic resistance spread in livestock

AIM

This study aimed to compare and characterize the resistance profile and the presence of extended-spectrum beta-lactamase (ESBL) related genes in Escherichia coli isolated from healthy finishing pigs fed with or without antibiotics in their diets.

METHODS AND RESULTS

A total of 27 ceftiofur-resistant E. coli isolates were obtained from 96 healthy pigs. The antibiotic resistance profile was tested, and all 27 isolates were classified as multidrug-resistant (MDR). A high proportion of isolates were resistant to cephalosporins, ampicillin, ciprofloxacin, and tetracyclines. The ESBL production was observed in 85% of isolates by double-disc synergy test. The MDR-E. coli isolates harbored ESBL genes, such as blaTEM, blaCTX-M-1, blaCTX-M-2, and blaCTX-M-8,25. In addition, other antibiotics resistance genes (ARGs) were also detected, such as sul2, ant(3″)-I, tetA, and mcr-1. The mobilization of the blaCTX-M gene was confirmed for nine E. coli isolates by conjugation assays. The presence of blaCTX-M on mobile genetic elements in these isolates was demonstrated by Southern blot hybridization, and the resistance to cephalosporins was confirmed in the transconjugants. Our results indicate the prevalence of CTX-M-producing E. coli strains harboring mobile genetic elements in the normal microbiota of healthy pigs.

CONCLUSIONS

These findings highlight the significance of ESBL genes as a global health concern in livestock and the potential spread of antimicrobial resistance to other members of the gastrointestinal tract microbiota.

Surface conditioning with bacteriophages reduces biofilm formation of Salmonella Heidelberg

Salmonella remains one of the most common foodborne pathogens worldwide, and its resistance to antimicrobials has increased considerably over the years. In this context, was evaluated the action of three bacteriophages isolated or combined in inhibiting the adhesion and removal of Salmonella Heidelberg biofilm on a polystyrene surface. The bacteriophages UPF_BP1, UPF_BP2, UPF_BP3 and a pool of them were used for biocontrol of Salmonella Heidelberg biofilms on polystyrene surface in the action times of 3, 6 and 9 h. Individual and combined phages exhibited reductions in Salmonella Heidelberg adhesion of up to 83.4% and up to 64.0% in removal of preformed biofilm. The use of synergistic combinations between the phages is the most indicated option due to its potential to reduce biofilms. The use of the bacteriophage pool in surface conditioning is an alternative in the control of Salmonella Heidelberg biofilms.

Feed safety evaluation for prevalence of zoonotic Salmonella spp. in animal feed

Owing to the zoonotic nature of Salmonella, its transmission from feed-to-food is quite feasible and considered as one of the prime factors for the transmission and spread of virulent and drug-resistant strains in humans. Therefore, the present study was designed to investigate the prevalence of Salmonella in animal feed pellets from different feed mills in Jaipur and its nearby areas. For this, isolation of Salmonella was performed as per standard ISO methods and the presumable strains were further confirmed and characterized into different species by molecular methods. The confirmed strains were analyzed for virulence genes by PCR. Finally, the strains were analyzed for antimicrobial drug resistance by the standard disk diffusion method. The study revealed that the prevalence of Salmonella in feed pellets was moderate and Salmonella enteritidis and Salmonella typhimurium were the two dominated species. Strikingly, the majority of strains were found to possess the virulence genes and resistant to analyzed clinical antimicrobials. Results inferred that contaminated animal feeds may act as a potential source for the dissemination of virulent and drug-resistant Salmonella spp in animals as well as human beings. The present study implicated the need for more focused and extensive investigations from different parts of the country and the world for strict regulation of animal feed safety to assure one health concept.

A Ternary Copper (II) Complex with 4-Fluorophenoxyacetic Acid Hydrazide in Combination with Antibiotics Exhibits Positive Synergistic Effect against Salmonella Typhimurium

Salmonella spp. continues to figure prominently in world epidemiological registries as one of the leading causes of bacterial foodborne disease. We characterised 43 Brazilian lineages of Salmonella Typhimurium (ST) strains, characterized drug resistance patterns, tested copper (II) complex as control options, and proposed effective antimicrobial measures. The minimum inhibitory concentration was evaluated for seven antimicrobials, isolated and combined with the copper (II) complex [Cu(4-FH)(phen)(ClO4)2] (4-FH = 4-fluorophenoxyacetic acid hydrazide and phen = 1,10-phenanthroline), known as DRI-12, in planktonic and sessile ST. In parallel, 42 resistance genes were screened (PCR/microarray). All strains were multidrug resistant (MDR). Resistance to carbapenems and polymyxins (86 and 88%, respectively) have drawn attention to the emergence of the problem in Brazil, and resistance is observed also to CIP and CFT (42 and 67%, respectively), the drugs of choice in treatment. Resistance to beta-lactams was associated with the genes blaTEM/blaCTX-M in 39% of the strains. Lower concentrations of DRI-12 (62.7 mg/L, or 100 μM) controlled planktonic and sessile ST in relation to AMP/SUL/TET and AMP/SUL/TET/COL, respectively. The synergistic effect provided by DRI-12 was significant for COL/CFT and COL/AMP in planktonic and sessile ST, respectively, and represents promising alternatives for the control of MDR ST.

Virulence Factors and Antimicrobial Resistance in Salmonella Species Isolated from Retail Beef in Selected KwaZulu-Natal Municipality Areas, South Africa

Salmonellosis and antimicrobial resistance caused by non-typhoidal Salmonella are public health concerns. This study aimed at determining prevalence, serovars, virulence factors and antimicrobial resistance of Salmonella from beef products. Four-hundred beef samples from 25 retail outlets in KwaZulu-Natal, South Africa were analyzed for Salmonella using standard methods, confirmation with matrix-assisted laser desorption ionization–time of flight and serotyping according to the White–Kauffmann–Le Minor scheme. The Kirby Bauer disk diffusion method was used to determine antimicrobial resistance against Cefotaxime, Kanamycin, Ampicillin, Amoxicillin, Trimethoprim Sulfamethoxazole, Ciprofloxacin, Chloramphenicol, Gentamicin Cefoxitin and Tetracycline. A polymerase chain reaction was performed to detect invA, agfA, lpfA, hilA, sivH, sefA, sopE, and spvC virulence genes. Salmonella was observed in 1.25% (5/400) of the samples. Four serovars (Enteritidis, Hadar, Heidelberg, Stanley) were identified. Almost all Salmonella were susceptible to all antimicrobials except S. Enteritidis isolate that was resistant to Tetracycline, Ampicillin and Amoxicillin. All Salmonella isolates carried at least two virulence factors. The findings indicate low Salmonella prevalence in meat from selected KZN retail beef; however, routine surveillance to monitor risk associated with virulence factors is required to mitigate potential outbreaks. The resistant S. Enteritidis highlights a need to routinely monitor antimicrobial resistance in order to enhance human health.

Virulence and antimicrobial resistance profile of non-typhoidal Salmonella enterica serovars recovered from poultry processing environments at wet markets in Dhaka, Bangladesh

The rapid emergence of virulent and multidrug-resistant (MDR) non-typhoidal Salmonella (NTS) enterica serovars is a growing public health concern globally. The present study focused on the assessment of the pathogenicity and antimicrobial resistance (AMR) profiling of NTS enterica serovars isolated from the chicken processing environments at wet markets in Dhaka, Bangladesh. A total of 870 samples consisting of carcass dressing water (CDW), chopping board swabs (CBS), and knife swabs (KS) were collected from 29 wet markets. The prevalence of Salmonella was found to be 20% in CDW, 19.31% in CBS, and 17.58% in KS, respectively. Meanwhile, the MDR Salmonella was found to be 72.41%, 73.21%, and 68.62% in CDW, CBS, and KS, respectively. All isolates were screened by polymerase chain reaction (PCR) for eight virulence genes, namely invA, agfA, IpfA, hilA, sivH, sefA, sopE, and spvC. The S. Enteritidis and untyped Salmonella isolates harbored all virulence genes while S. Typhimurium isolates carried six virulence genes, except sefA and spvC. Phenotypic resistance revealed decreased susceptibility to ciprofloxacin, streptomycin, ampicillin, tetracycline, gentamicin, sulfamethoxazole-trimethoprim, amoxicillin-clavulanic acid, and azithromycin. Genotypic resistance showed a higher prevalence of plasmid-mediated blaTEM followed by tetA, sul1, sul2, sul3, and strA/B genes. The phenotypic and genotypic resistance profiles of the isolates showed a harmonic and symmetrical trend. According to the findings, MDR and virulent NTS enterica serovars predominate in wet market conditions and can easily enter the human food chain. The chi-square analysis showed significantly higher associations among the phenotypic resistance, genotypic resistance and virulence genes in CDW, CBS, and KS respectively (p < 0.05).

Molecular Characterization and Survive Abilities of Salmonella Heidelberg Strains of Poultry Origin in Brazil

The aim of the study was to evaluate the genotypic and phenotypic characteristics of 20 strains of S. Heidelberg (SH) isolated from broilers produced in southern Brazil. The similarity and presence of genetic determinants linked to virulence, antimicrobial resistance, biofilm formation, and in silico-predicted metabolic interactions revealed this serovar as a threat to public health. The presence of the ompC, invA, sodC, avrA, lpfA, and agfA genes was detected in 100% of the strains and the luxS gene in 70% of them. None of the strains carries the bla_SHV, mcr-1, qnrA, qnrB, and qnrS genes. All strains showed a multidrug-resistant profile to at least three non-β-lactam drugs, which include colistin, sulfamethoxazole, and tetracycline. Resistance to penicillin, ceftriaxone (90%), meropenem (25%), and cefoxitin (25%) were associated with the presence of bla_CTX–M and bla_CMY–2 genes. Biofilm formation reached a mature stage at 25 and 37°C, especially with chicken juice (CJ) addition. The sodium hypochlorite 1% was the least efficient in controlling the sessile cells. Genomic analysis of two strains identified more than 100 virulence genes and the presence of resistance to 24 classes of antibiotics correlated to phenotypic tests. Protein-protein interaction (PPI) prediction shows two metabolic pathways correlation with biofilm formation. Virulence, resistance, and biofilm determinants must be constant monitoring in SH, due to the possibility of occurring infections extremely difficult to cure and due risk of the maintenance of the bacterium in production environments.

The effect of vegetation barriers at reducing the transmission of Salmonella and Escherichia coli from animal operations to fresh produce

Due to the recent outbreaks of Salmonella and Escherichia coli in fresh produce in the United States, the transfer of foodborne pathogens between animal feeding operations and fresh produce continues to be a considerable risk. The purpose of this study was to determine if the establishment of a vegetation barrier (VB) on small-scale sustainable farms could prevent the transmission of Salmonella and E. coli to nearby fresh produce fields. A 5-layer VB (31 × 49 m) was constructed between a dairy farm, a poultry farm, and a nearby produce field. Fresh produce (i.e., romaine lettuce and tomato), animal feces, and environmental (i.e., air, soil, and barrier) samples were collected for 15 months from 2018 to 2019. Four replicates of soil and fresh produce samples were taken from three plots located 10 m, 61 m, and 122 m away from the respective animal locations and processed for Salmonella and E. coli. Air and vegetative strip samples were sampled at 15-day intervals. Multiple colonies were processed from each positive sample, and a total of 143 positive Salmonella (n = 15) and E. coli (n = 128) isolates were retrieved from the soil, produce, air, and fecal samples. Interestingly, 18.2% of the Salmonella and E. coli isolates (n = 26) were recovered from fresh produce (n = 9) samples. Surprisingly, Salmonella isolates (n = 9) were only found in fecal (n = 3) samples collected from the dairy pasture. Data analysis suggests that the VB is an effective tool at reducing the transmission of E. coli and Salmonella from animal farms to fresh produce fields. However, based on phenotypic and genotypic testing, it is clear that fecal samples from animal farms are not the only source of pathogen contamination. This indicates that the environment (e.g., soil and wind), as well as the initial setup of the farm (e.g., proximity to service roads and produce plot placement), can contribute to the contamination of fresh produce. Our study recommends the need for more effective bioremediation and prevention control measures to use in conjunction with VBs to reduce pathogen transmission.

Prevalence, Serovars, and Factors Associated with Salmonella Contamination of Chicken Carcasses Sold in Outlets of the Informal Market in Gauteng Province, South Africa

ABSTRACT

Salmonella has been linked to many foodborne illnesses and epidemics in both humans and animals. This cross-sectional study determined the prevalence, serovars, and factors associated with Salmonella contamination of chickens slaughtered in informal market outlets in Gauteng Province, South Africa. A total of 151 chicken carcasses were randomly collected from 47 outlets. Standard bacteriological and molecular methods were used to isolate, identify, and determine the serovar of Salmonella isolates. The prevalence of Salmonella in carcass swabs, cloacal swabs, and carcass drips was 29.1% (44 of 151), 27.2% (41 of 151), and 43.7% (66 of 151), respectively, and the differences were statistically significant (P = 0.004). Only 5 (township locations of outlet, throughput, carcass evisceration, location of carcass for sale, and outlet sanitation) of 10 factors investigated for the contamination of carcasses by Salmonella were statistically significantly (P < 0.05) associated with the isolation of Salmonella. Of the 268 isolates of Salmonella, 157 (58.6%) were typeable using a limited molecular PCR technique, and nine serovars were identified. The predominant Salmonella enterica serovars were Bovismorbificans (31.0%), Enteritidis (7.5%), and Hadar (6.7%). The five important factors found to be significantly associated with the isolation of Salmonella at these outlets offer opportunities for the reduction of Salmonella contamination. There is a need for further investigation of the probable causes of the predominant isolation of Salmonella serovar Bovismorbificans in chickens and its potential implications for human infections in South Africa. It is concluded that chickens purchased from the informal market in Gauteng Province can be a source for salmonellosis in humans if improperly cooked before consumption.

Retrospective whole-genome comparison of Salmonella enterica serovar Enteritidis from foodborne outbreaks in Southern Brazil

Salmonella enterica serovar Enteritidis is frequently isolated from animal-source foods associated with human salmonellosis outbreaks. This serovar was spread to animal (mainly poultry) farms worldwide in the 1980s, and it is still detected in foods produced in many countries, including Brazil. The present study reports a retrospective genome-wide comparison of S. Enteritidis from foodborne outbreaks in Southern Brazil in the last two decades. Fifty-two S. Enteritidis isolates were obtained from foodborne outbreaks occurring in different cities of the Brazilian southernmost State, Rio Grande do Sul (RS), from 2003 to 2015. Whole-genome sequences (WGS) from these isolates were obtained and comparatively analyzed with 65 additional genomes from NCBI. Phylogenetic and Bayesian analyses were performed to study temporal evolution. Genes related to antibiotic resistance and virulence were also evaluated. The results demonstrated that all S. Enteritidis isolates from Southern Brazil clustered in the global epidemic clade disseminated worldwide originally in the 1980s. Temporal analysis demonstrated that all Brazilian isolates had a tMRCA (time to most recent common ancestor) in 1986 with an effective population size (N_e) increase soon after until 1992, then becoming constant up to now. In Southern Brazil, there was a significant decrease in the spreading of S. Enteritidis in the last decade. In addition, three antibiotic resistance genes were detected in all isolates: aac(6')-Iaa, mdfA, and tet(34). These results demonstrate the high frequency of one only specific S. Enteritidis lineage (global epidemic clade) in foodborne outbreaks from Southern Brazil in the last two decades.

Characterization of Salmonella Isolates Recovered from Stages of the Processing Lines at Four Broiler Processing Plants in Trinidad and Tobago

This cross-sectional study determined the prevalence, characteristics, and risk factors for contamination of chicken with Salmonella at four operating broiler processing plants in Trinidad. Standard methods were used to isolate and characterize the Salmonella isolates. The overall prevalence of Salmonella at the four processing plants was 27.0% (107/396). The whole carcass enrichment (WCE) method yielded a statistically significantly (p = 0.0014) higher frequency of isolation (53.9%; 97/180) than the whole carcass rinse (35.0%; 63/180) and neck skin methods (42.2%; 38/90). S. enterica serotypes Enteritidis, Javiana, and Infantis were the predominant serotypes isolated accounting for 20.8%, 16.7% and 12.5%, respectively, of the serotyped isolates. Risk factors included the use of over 100 contract farmers (OR 4.4), pre-chiller (OR 2.3), addition of chlorine to chiller (OR 3.2), slaughtering sick broilers (OR 4.4), and flocks with >50% mortality. Multi-drug resistance was detected in 12.3% (14/114) of the isolates of Salmonella. Resistance was high to kanamycin (85.7%) and doxycycline (74.6%) but low to amoxicillin-clavulanic acid (2.4%) and sulphamethoxazole-trimethoprim (0.8%). The occurrence of resistant Salmonella in chickens processed at commercial broiler processing plants has implications for salmonellosis and therapeutic failure in consumers of improperly cooked contaminated chickens from these plants in the country.

Salmonella enterica Serovar Minnesota Biofilms, Susceptibility to Biocides, and Molecular Characterization

The presence of virulence genes, phylogenetic relationships, biofilm formation index (BFI), and ultrastructure in S. Minnesota at different temperatures (4, 25, and 36 °C) were analyzed. In addition, the ability of biocidal agents (chlorhexidine1%, sodium hypochlorite 1%, and peracetic acid 0.8%) to inhibit biofilms formed by 20 strains isolated from broiler slaughter plants from two Brazilian companies in 2009, 2010, and 2014 was determined. The presence of specific genes was evaluated by PCR and phylogeny between strains by pulsed-field gel electrophoresis. The BFI was determined using tryptone soy broth with 5% of chicken juice, and its structure was observed by scanning electron microscopy. The presence of specific genes indicated that S. Minnesota has the potential to cause disease in humans, adapting to adverse conditions. Temperatures of 25 and 36 °C favored biofilm formation, although at 4 °C, there was still biomass that could contaminate the final product. Tolerance to all biocides was identified in 12/20 (60%), representing a real risk of adaptation mechanisms development, especially regarding to resistance to sodium hypochlorite. Phylogenetic analysis indicated cross-contamination and spread among companies, which was probably related to biofilms formation. Results show the necessity of attention to this serovar considering its resistance to sodium hypochlorite, including the need for rigorous control, adopting low temperatures to prevent biofilms formation in the poultry industry.

Virulence and Antimicrobial Resistance Profiles of Salmonella enterica Serovars Isolated from Chicken at Wet Markets in Dhaka, Bangladesh

Virulent and multi drug resistant (MDR) Salmonellaenterica is a foremost cause of foodborne diseases and had serious public health concern globally. The present study was undertaken to identify the pathogenicity and antimicrobial resistance (AMR) profiles of Salmonellaenterica serovars recovered from chicken at wet markets in Dhaka, Bangladesh. A total of 870 cecal contents of broiler, sonali, and native chickens were collected from 29 wet markets. The overall prevalence of S. Typhimurium, S. Enteritidis, and untyped Salmonella spp., were found to be 3.67%, 0.57%, and 1.95% respectively. All isolates were screened by polymerase chain reaction (PCR) for eight virulence genes, namely invA, agfA, IpfA, hilA, sivH, sefA, sopE, and spvC. S. Enteritidis isolates carried all virulence genes whilst S. Typhimurium isolates carried six virulence genes except sefA and spvC. A diverse phenotypic and genotypic AMR pattern was found. Harmonic descending trends of resistance patterns were observed among the broiler, sonali, and native chickens. Interestingly, virulent and MDR Salmonella enterica serovars were found in native chicken, although antimicrobials were not used in their production cycle. The research findings anticipate that virulent and MDR Salmonella enterica are roaming in the wet markets which can easily anchor to the vendor, consumers, and in the food chain.

Antimicrobial Resistance Profiles of Salmonella Isolates on Chickens Processed and Retailed at Outlets of the Informal Market in Gauteng Province, South Africa

The study determined the antimicrobial resistance profiles of Salmonella on chickens processed and retailed at outlets of the informal markets in Gauteng province, South Africa. The study also investigated the relationship of antimicrobial resistant Salmonella to the source and type of samples and their serotypes. Carcass swabs, cloacal swabs and carcass drips were randomly collected from each of 151 slaughtered chickens from six townships. Isolation and identification were performed using standard and polymerase chain reaction (PCR) methods. The disc diffusion method was used to determine the resistance of Salmonella isolates to 16 antimicrobial agents and PCR to determine their serovars. Ninety-eight (64.9%) of the 151 chickens were contaminated with Salmonella of which 94.9% (93/98) were resistant serovars. The frequency of antimicrobial resistance of Salmonella isolates was high to erythromycin (94.9%) and spectinomycin (82.7%) but was low to ciprofloxacin (1.0%) and norfloxacin (1.0%) (p < 0.05). All 170 isolates of Salmonella tested exhibited resistance to one or more antimicrobial agents and the frequency varied significantly (p < 0.05) across the townships, the type of samples and the serovars. The prevalence of multidrug resistance (MDR) in Salmonella was 81.8% (139/170). Our findings pose zoonotic, food safety and therapeutic risks to workers and consumers of undercooked, contaminated chickens from these outlets.

Occurrence of Virulence and Resistance Genes in Salmonella in Cloacae of Slaughtered Chickens and Ducks at Pluck Shops in Trinidad

ABSTRACT

The study used PCR to determine the molecular basis of the antibiotic resistance and virulence profiles of isolates of Salmonella by targeting genes encoding for carriage and persistence in the poultry. Of a total 1,503 cecal samples collected from poultry, 91 (6.1%) were positive for Salmonella. Ten different serotypes were detected from Salmonella isolates. The study was also conducted to determine the occurrence of 13 virulence and 12 resistance genes in isolates of Salmonella. All 46 isolates of Salmonella tested were positive for one or more of the 12 virulence genes detected, ranging from 0.0% (viaB) to 100.0% (invA, mgtB, pipA, and spi4D) (P < 0.05). Occurrence of virulence genes varied significantly (P < 0.05) by serotype but not by animal species. Only 4 (33.3%) of 12 resistance genes assayed were detected: strA, ampC, cmy2, and qnrB. Overall, the occurrence of detected resistance genes was 71.7% (33 of 46), and 87.1 and 40.0% of the isolates from chickens and ducks, respectively, were positive (P = 0.0009). The occurrence of resistance genes ranged from 2.2% (cmy2) to 50.0% (qnrB) in isolates positive for resistance gene. The findings provide evidence that poultry from "pluck shops" are colonized by Salmonella pathogens that harbor virulence and antimicrobial resistance genes; this may have clinical and therapeutic consequences, if the genes detected are expressed. Although there is a need for prudent use of antimicrobial agents in poultry production systems, there should be constant monitoring for the prevalence of resistance in Salmonella isolates using phenotypic methods. The importance of monitoring the occurrence of resistance genes in the pathogens in Trinidad cannot be ignored.

HIGHLIGHTS

Pet birds as potential reservoirs of virulent and antibiotic resistant zoonotic bacteria

Bacterial pathogens carried by pet birds are considered a risk for birds, workers, and pet owners. This study investigated the potential of pet birds as reservoirs for virulent multidrug-resistant (MDR) zoonotic bacteria and assessed the genetic relatedness and diversity of bacterial isolates from pet birds and human contacts. Cloacal and tracheal swabs from 125 pet birds and 70 hand swabs from human contacts were collected. The results revealed that the pet birds were reservoirs for Escherichia coli, Klebsiella pneumoniae (17.6 %, each), and Staphylococcus aureus (15.2 %). These isolates were also identified in their human contacts, at percentages of 14.3 %, 12.9 %, and 24.3 %, respectively. Virulence associated genes were identified from E. coli (stx2, stx2f, eaeA, and hlyA), K. pneumoniae (fimH, TraT, and magA), and S. aureus (PVL, hly, sea, sed genes) isolates. Multidrug-resistant E. coli, K. pneumoniae, and S. aureus were highly prevalent (81.3 %, 90.3 %, and 61.1 %, respectively). The genetic relationship between the E. coli and K. pneumoniae isolates from the pet birds and human contacts were determined by ERIC-PCR, while, RAPD-PCR was used for the S. aureus isolates. ERIC-PCR was found to have the highest discriminatory power. The clustering of the isolates from the pet birds and human contacts indicated potential transmission between the birds and workers. In conclusion, pet birds could act as potential reservoirs for zoonotic bacterial pathogens; thus, posing a risk to their human contacts.

Prevalence of Salmonella enterica on poultry processing equipment after completion of sanitization procedures

Salmonella is a poultry-borne pathogen that causes illness throughout the world. Consequently, it is critical to control Salmonella during the process of converting broilers to poultry meat. Sanitization of a poultry processing facility, including processing equipment, is a crucial control measure that is utilized by poultry integrators. However, prevalence of Salmonella on equipment after sanitization and its potential risk to food safety has not been evaluated thoroughly. Therefore, the objective of this study was to evaluate the persistence of Salmonella on poultry processing equipment before and following cleaning and sanitization procedure. A total of 15 locations within 6 commercial processing plants were sampled at 3 time points: (A) after processing; (B) after cleaning; and (C) after sanitization, on 3 separate visits for a total of 135 samples per plant. Salmonella-positive isolates were recovered from samples using the United States Department of Agriculture MLG 4.09 conventional method. Presumptive Salmonella colonies were subjected to biochemical tests for confirmation. Salmonella isolates recovered after sanitization were serotyped and tested for the presence of specific virulence genes. A completely randomized design with a 6 × 3 × 15 factorial arrangement was utilized to analyze the results for Salmonella prevalence between processing plants. Means were separated using Fishers protected least significant difference when P ≤ 0.05. For Salmonella prevalence between processing plants, differences (P < 0.0001) were observed in the 6 plants tested where the maximum and minimum prevalence was 29.6 and 7.4%, respectively. As expected, there was a difference (P < 0.0001) in the recovery of Salmonella because of sampling time. Salmonella prevalence at time A (36%) was significantly higher, whereas there was no difference between time B (12%) and C (9%). There was a location effect (P < 0.0001) for the prevalence of Salmonella with the head puller, picker, cropper, and scalder having a significantly higher prevalence when compared with several other locations. At sampling time C, a trend toward a difference (P = 0.0899) was observed for Salmonella prevalence between the 6 plants, whereas significant differences were observed because of location (P = 0.0031). Five prominent Salmonella enterica serovars were identified, including Kentucky, Schwarzengrund, Enteritidis, Liverpool, and Typhimurium with S. Kentucky being the most prevalent. PCR analysis of 8 Salmonella virulence genes showed that the invA, sipB, spiA, sseC, and fimA were detected in all isolates, whereas genes carried on plasmids and/or fimbriae varied remarkably among all isolates. This study established Salmonella prevalence and persistence in poultry processing facilities after antimicrobial application through sanitization procedures which could result in contamination of poultry carcasses and food safety risks because of poultry meat.

Antimicrobial susceptibility and detection of virulence-associated genes of Escherichia coli and Salmonella spp. isolated from domestic pigeons (Columba livia) in Brazil

Overpopulation of domestic pigeons is considered to be one of the major problems of urban centers, as these birds are responsible for the dissemination of relevant pathogens to animal and human health. The aim of this study was to detect potentially pathogenic Escherichia coli and Salmonella spp. in domestic pigeons captured in areas near silos used for grain and feed storage, analyzing the antimicrobial sensitivity and the presence of virulence-associated genes. We evaluated 41 pigeons. From each bird, cecal contents and a pool of viscera (heart, spleen, and liver) were collected. Fifty strains of E. coli and three strains of S. Typhimurium were isolated. The antimicrobial susceptibility assay showed that 2% of the isolates of E. coli were resistant to chloramphenicol and the combination of sulfamethoxazole + trimethoprim and 4% to tetracycline, doxycycline, and sulfonamide. The three S. Typhimurium strains were sensitive to all antimicrobials tested. The pathogenicity profile demonstrated that no E. coli isolates showed a STEC compatible profile. Regarding the APEC pathotype, all genes were observed in 8% of E. coli, 6% had only the iss gene and 4% presented ompT, hlyF, and iutA genes. invA, hilA, avrA, and lpfA genes were detected in 100% of Salmonella isolates. The sitC and pefA genes were only present in one strain and the remaining genes were detected in two. In conclusion, it was found that pigeons living in the vicinity of silos are carriers of important pathogens, and control measures should be taken to minimize animal and human health risks.

Detection of Escherichia coli O157:H7 Using Automated Immunomagnetic Separation and Enzyme-Based Colorimetric Assay

The food industry requires rapid and simple detection methods for preventing harm from pathogenic bacteria. Until now, various technologies used to detect foodborne bacteria were time-consuming and laborious. Therefore, we have developed an automated immunomagnetic separation combined with a colorimetric assay for the rapid detection of E. coli O157:H7 in food samples. The colorimetric detection method using enzymatic reaction is fascinating because of its simplicity and rapidity and does not need sophisticated devices. Moreover, the proposed procedures for the detection of bacteria in food take less than 3 h including pre-enrichment, separation and detection steps. First, target-specific immunomagnetic beads were introduced to contaminated milk in a pre-enrichment step. Second, the pre-enriched sample solution containing target bacteria bound on immunomagnetic beads was injected into an automated pretreatment system. Subsequently, the immunomagnetic beads along with target bacteria were separated and concentrated into a recovery tube. Finally, released β-galactosidase from E. coli O157:H7 after lysis was reacted with chlorophenol red β-galactopyranoside (CPRG) used as a substrate and the colorimetric change of CPRG was determined by absorbance measuring or the naked eye. By the proposed approach in this study, we could detect 3 × 10² CFU/mL of E. coli O157:H7 from a milk sample within 3 h.

Prevalence and related factors of Salmonella spp. and Salmonella Typhimurium contamination among broiler farms in Kerman province, Iran

Salmonella is one of the most important pathogens in the poultry industry that not only causes financial and economic damage, but also, some serovars of this bacterium, including the S. Typhimurium, can infect humans through poultry-to-human transmission. The purpose of this study was to investigate the prevalence of this pathogen among broiler poultry houses in the Kerman region, southeast of Iran and to identify factors which could increase the risk for Salmonella contamination in the chickens. In a cross-sectional study, 110 poultry houses were surveyed from June to October 2018. Twenty-eight variables related to the prevalence of Salmonella contamination were considered by a questionnaire template with farmers' and laborers' help. Also, the prevalence of Salmonella in poultry manure was determined based on fecal sampling, microbiological tests and polymerase chain reaction (PCR) technique. A multivariable logistic regression model was developed to measure the influence of independent variables on Salmonella contamination. Results showed that a time interval less than one month between the two breeding periods (OR = 6.530), the number of fans less than 5 in each poultry house (OR = 4.094) and the number of houses less than 4 in each farm significantly increased the probability of infection with Salmonella spp. (ORs were respectively 9.650, 29.427 and 7.140 for one, two and three houses). Also, the results of multivariable logistic regression showed that the use of a bell drinking system (OR = 4.379) and the presence of fewer than 5 fans in each poultry house (OR = 2.512) increased significantly the risk of infection with Salmonella Typhimurium.

Detection of Salmonella in Food Matrices, from Conventional Methods to Recent Aptamer-Sensing Technologies

Rapid detection of the foodborne pathogen Salmonella in food processing is of crucial importance to prevent food outbreaks and to ensure consumer safety. Detection and quantification of Salmonella species in food samples is routinely performed using conventional culture-based techniques, which are labor intensive, involve well-trained personnel, and are unsuitable for on-site and high-throughput analysis. To overcome these drawbacks, many research teams have developed alternative methods like biosensors, and more particularly aptasensors, were a nucleic acid is used as biorecognition element. The increasing interest in these devices is related to their high specificity, convenience, and relative rapid response. This review aims to present the advances made in these last years in the development of biosensors for the detection and the quantification of Salmonella, highlighting applications on meat from the chicken food chain.

Detection of Salmonella pathogenicity island and Salmonella plasmid virulence genes in Salmonella Enteritidis originated from layer and broiler farms in Java Island

OBJECTIVE

The incidence of salmonellosis in humans and animals is still high due to the occurrence of virulence factors in Salmonella enterica which play a role in the process of infection in the host and the spread of disease and most of the S. enterica can infect humans and animals. The present study was aimed to identify Salmonella Enteritidis and detect virulence genes related to Salmonella pathogenicity islands (SPIs) and Salmonella plasmid virulence (Spv).

MATERIALS AND METHODS

A total of 27 S. Enteritidis archive isolates belonging to the National Veterinary Drug Assay Laboratory (NVDAL) were used in this study. The bacteria were collected in 2016 and 2017 from samples of the cloaca and fecal swabs from layer and broiler farms in five provinces of Java Island. Isolates were cultured in specific media, biochemical tests and Gram staining. Detection of S. Enteritidis and virulence genes was done by polymerase chain reaction (PCR) method.

RESULTS

Identification of serovar showed 100% (27/27) isolates were positive for the sdfI gene (304 bp). The result confirmed that all strains were S. Enteritidis. PCR based detection of virulence genes showed that 100% of isolates had virulence genes in SPI-1 to SPI-5, namely, invA, ssaQ, mgtC, spi4D, and pipA genes. All the isolates (27/27) were also positive to spvB gene-based PCR.

CONCLUSION

All the isolates of S. Enteritidis in this study carry virulence genes related to SPI-1 to SPI-5 and plasmid virulence. The existence of virulent genes indicates that the S. Enteritidis strain examined in this study is highly virulent and poses a potential threat of worse disease outcome in humans and animals.

Detection of virulence genes in Salmonella Heidelberg isolated from chicken carcasses

During the last years, Brazilian government control programs have detected an increase of Salmonella Heidelberg in poultry slaughterhouses a condition that poses a threat to human health However, the reasons remain unclear. Differences in genetic virulence profiles may be a possible justification. In addition, effective control of Salmonella is related to an efficient epidemiological surveillance system through genotyping techniques. In this context, the aim of this study was the detection of 24 virulence-associated genes in 126 S. Heidelberg isolates. We classified the isolates into 56 different genetic profiles. None of the isolates presented all the virulence genes. The prevalence of these genes was high in all tested samples as the lowest number of genes detected in one isolate was 10/24. The lpfA and csgA (fimbriae), invA and sivH (TTSS), and msgA and tolC (intracellular survival) genes were present in 100% of the isolates analyzed. Genes encoding effector proteins were detected in the majority of SH isolates. No single isolate had the sefA gene. The pefA gene was found in only four isolates. We have also performed a screening of genes associated with iron metabolism: 88.9% of isolates had the iroN geneand 79.4% the sitC gene . Although all the isolates belong to the same serotype, several genotypic profiles were observed. These findings suggest that there is a diversity of S. Heidelberg isolates in poultry products. The fact that a single predominant profile was not found in this study indicates the presence of variable sources of contamination caused by SH. The detection of genetic profiles of Salmonella strains can be used to determine the virulence patterns of SH isolates.

Molecular detection of Salmonella serovars Enteritidis, Heidelberg and Typhimurium directly from pre-enriched poultry samples

1. Salmonella is one of the most important pathogens in public health and it is usually associated with food-borne diseases. Salmonella serovars Enteritidis and Typhimurium are widespread in the world with outbreaks frequently associated with consumption of poultry products; furthermore, there is an increasing public health concern with the wide dissemination of the serovar Heidelberg in poultry flocks. 2. The aim of the experiment was to develop and to validate rapid methods to detect Salmonella serovars Enteritidis, Typhimurium, and Heidelberg by real-time PCRs and test isolates from pre-enriched poultry samples. 3. Three real-time PCRs were developed and used in combination to detect the serovars Enteritidis, Typhimurium and Heidelberg. These assays were validated by the analysis of 126 Salmonella isolates, eight other enteric bacterial species and 34 naturally contaminated poultry samples after pre-enrichment with buffered peptone water (BPW). 4. Real-time PCRs detected the isolates of the most important poultry serovars (Enteritidis, Typhimurium and Heidelberg) with 100% inclusivity and exclusivity in each assay. The PCR identified monophasic variants of the serovars Typhimurium and Heidelberg. All PCRs were validated in detecting these specific serovars directly from pre-enriched poultry samples. The whole analytical procedure was performed in less than 24 h in a veterinary diagnostic laboratory.

Comparative evaluation of structure and characteristic of peptidyl-prolyl cis-trans isomerase proteins and their function in Salmonella Typhimurium stress responses and virulence

Peptidyl-prolyl cis-trans isomerases (PPIase) exhibit chaperone activity and assist in protein folding by increasing the rate of cis-trans transition on proline-peptide bonds. The current study aimed to identify and characterize three genes, ppiA, ppiB, and ppiC, which encode proteins of the PPIase family in the bacterium Salmonella enterica serovar Typhimurium. Salmonella Typhimurium is a facultative intracellular zoonotic pathogen that causes food- and water-borne gastroenteritis in humans (leading to bacteremia in immune-compromised subjects). Recombinant clones for the three genes were constructed and sequenced and the sequences submitted to NCBI GenBank. Three-dimensional structures for the corresponding proteins were predicted by comparative modeling. A maximum-likelihood phylogenetic gene tree constructed for the three genes showed a low evolutionary mean diversity, indicating strong evolutionary conservation. Further, single-gene deletion mutant strains, generated for the respective genes, were observed to be more susceptible to the stationary phase of growth and heat stress conditions and showed reduced survival within macrophage cells line. The present study thus indicates that ppiA, ppiB, and ppiC genes are conserved among Salmonella genome, are critical for the growth of Salmonella Typhimurium in the examined stress conditions, and may play a role in its responses and virulence.

Salmonella Typhimurium Sensing Strategy Based on the Loop-Mediated Isothermal Amplification Using Retroreflective Janus Particle as a Nonspectroscopic Signaling Probe

Loop-mediated isothermal amplification (LAMP) is a powerful gene amplification method, which has many advantages, including high specificity, sensitivity, and simple operation. However, quantitative analysis of the amplified target gene with the LAMP assay is very difficult. To overcome this limitation, we developed a novel biosensing platform for molecular diagnosis by integrating the LAMP method and retroreflective Janus particle (RJP) together. The final amplified products of the LAMP assay are dumbbell-shaped DNA structures, containing a single-stranded loop with two different sequences. Therefore, the concentration of the amplified products can be measured in a manner similar to the sandwich-type immunoassay. To carry out the sandwich-type molecular diagnostics using the LAMP product, two DNA probes, with complementary sequences to the loop-regions, were prepared and immobilized on both the sensing surface and the surface of the RJPs. When the amplified LAMP product was applied to the sensing surface, the surface-immobilized DNA probe hybridized to the loop-region of the LAMP product to form a double-stranded structure. When the DNA probe-conjugated RJPs were injected, the RJPs bound to the unreacted loop-region of the LAMP product. The number of RJPs bound to the loop-region of the LAMP product was proportional to the concentration of the amplified LAMP product, indicating that the concentration of the target gene can be quantitatively analyzed by counting the number of observed RJPs. Using the developed system, a highly sensitive and selective quantification of Salmonella was successfully performed with a detection limit of 10² CFU.

Identification and Discrimination of Salmonella enterica Serovar Gallinarum Biovars Pullorum and Gallinarum Based on a One-Step Multiplex PCR Assay

Salmonella enterica serovar Gallinarum biovars Pullorum (S. Pullorum) and Gallinarum (S. Gallinarum) can result in pullorum disease and fowl typhoid in avian species, respectively, and cause considerable economic losses in poultry in many developing countries. Conventional Salmonella serotyping is a time-consuming, labor-intensive and expensive process, and the two biovars cannot be distinguished using the traditional serological method. In this study, we developed a rapid and reliable one-step multiplex polymerase chain reaction (PCR) assay to simultaneously identify and discriminate the biovars Pullorum and Gallinarum. The multiplex PCR method focused on three specific genes, stn, I137_08605 and ratA. Based on bioinformatics analysis, we found that gene I137_08605 was present only in S. Pullorum and S. Gallinarum, and a region of difference in ratA was deleted only in S. Pullorum after comparison with that of S. Gallinarum and other Salmonella serovars. Three pairs of primers specific for the three genes were designed for the multiplex PCR system and their selectivity and sensitivity were determined. The multiplex PCR results showed that S. Pullorum and S. Gallinarum could be identified and discriminated accurately from all tested strains including 124 strains of various Salmonella serovars and 42 strains of different non-Salmonella pathogens. In addition, this multiplex PCR assay could detect a minimum genomic DNA concentration of 67.4 pg/μL, and 100 colony forming units. The efficiency of the multiplex PCR was evaluated by detecting natural-occurring Salmonella isolates from a chicken farm. The results demonstrated that the established multiplex PCR was able to identify S. Gallinarum and S. Pullorum individually, with results being consistent with traditional serotyping and biochemical testing. These results demonstrated that a highly accurate and simple biovar-specific multiplex PCR assay could be performed for the rapid identification and discrimination of Salmonella biovars Gallinarum and Pullorum, which will be useful, particularly under massive screening situations.

Prevalência de Salmonella spp. em suínos abatidos em um frigorífico do Distrito Federal determinada pela técnica de PCR

Resumo A cadeia de produção suína vem crescendo assim como a exigência do fornecimento de produtos de qualidade, isentos de qualquer risco para os consumidores. A Salmonella spp. representa um risco biológico e é apontada como o agente responsável por diversos casos de doenças transmitidas por alimentos. O suíno é considerado um importante reservatório de Salmonella spp., o que torna imprescindível o conhecimento da dinâmica dessa bactéria em toda a cadeia de produção suína. Este trabalho foi realizado com o objetivo de determinar a prevalência de Salmonella spp. em suínos abatidos no Distrito Federal. Para isso, foram coletadas 240 amostras de linfonodos mesentéricos (LM) e 240 swabs de carcaça (SC) em um abatedouro com inspeção distrital. As amostras foram submetidas à PCR (Reação em Cadeia de Polimerase) para detecção da bactéria, revelando uma prevalência de 68,75% em LM de suínos abatidos e de 29,17% em SC suína. A análise dos dados obtidos demonstrou que a distância entre granja de origem e abatedouro apresentou correlação positiva moderada com a prevalência de Salmonella spp. em LM de suínos abatidos. Foi constatada, ainda, uma correlação positiva fraca entre a prevalência de Salmonella spp. em LM de suínos abatidos e a prevalência de Salmonella spp. em SC. Esses resultados apontam a necessidade da implantação de programas de controle para diminuir a prevalência nos animais destinados ao abate, bem como evitar a contaminação cruzada nos estabelecimentos manipuladores de alimentos.

Detection and Characterization of Salmonella Serotypes in the Production Chain of Two Pig Farms in Buenos Aires Province, Argentina

The aim of the present study was to determine the prevalence of Salmonella in the pork production chain and to characterize Salmonella isolates. From 764 samples, 35 (4.6%) were positive for Salmonella spp., as determined by biochemical tests and the presence of the invA gene. From these, 2.6, 2.0, 8.8, and 8.0% corresponded to samples collected from farms, slaughterhouses, boning rooms and retail markets, respectively. Salmonella strains were classified into five serotypes and distributed as follows: S. Typhimurium in the pork production chain, S. Kentucky in farms and slaughterhouses, S. Brandenburg in slaughterhouses, S. Livingstone in farms and S. Agona in boning rooms and retail markets. Interestingly, the antimicrobial susceptibility testing indicated that all 35 Salmonella spp.-positive isolates were resistant to at least one antimicrobial agent, and 30 were multidrug-resistant (MDR) and resistant to different classes of antibiotics. The enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) analysis showed clonal relatedness among strains isolated from farms, boning rooms and retail markets. The presence of antibiotic-resistant Salmonella in food poses a potential health hazard to consumers.

Phenotypic and Molecular Characterization of Salmonella Enteritidis SE86 Isolated from Poultry and Salmonellosis Outbreaks

Salmonella Enteritidis remains a standout among the leading causes of foodborne diseases worldwide. Previous studies have demonstrated that a unique clonal group of Salmonella Enteritidis, named SE86, is involved in foodborne outbreaks in southern Brazil and is frequently identified among strains isolated from poultry. The aim of this study was to determine the influence of the isolation source (food products involved in salmonellosis outbreaks and poultry sources) on the phenotypic and molecular characteristics of Salmonella Enteritidis SE86. A biofilm formation assay, antimicrobial susceptibility test, polymerase chain reaction identification of virulence-associated genes, and phage type 4 (PT4) assessment were performed to characterize Salmonella Enteritidis SE86. The human strains presented less antimicrobial resistance than the poultry strains. Resistance to some substances was related to the isolation source of the strain. Strains of the same clonal group presented different biofilm production abilities. Biofilm formation was independent of the isolation source at all temperatures. Temperature influenced biofilm formation only by the poultry strains. Most of the investigated genes presented a high frequency and a regular distribution, regardless of the isolation source. The spvB, spiA, pagC, sipB, prgH, spaN, sitC, and lpfC genes were associated with the avian strains, whereas iroN was associated with the strains isolated from food products involved in salmonellosis outbreaks. Most strains belonged to PT4. No relationship was found between biofilm production and antimicrobial resistance or between the virulence profile and biofilm production or antimicrobial resistance.

Sodium bisulfate and a sodium bisulfate/tannin mixture decreases pH when added to an in vitro incubated poultry cecal or fecal contents while reducing Salmonella Typhimurium marker strain survival and altering the microbiome

The objective of the present study was to investigate the ability of animal feed-grade sodium bisulfate (SBS) and a mixture of sodium bisulfate/tannin to inhibit the growth of Salmonella using an anerobic in vitro mixed cecal culture to mimic the conditions within the chicken cecum. An initial inoculum of Salmonella Typhimurium was introduced to an anerobic dilution solution containing 1/3000 diluted cecal bacteria and solids consisting of ground chicken feed and different percentages of solid SBS or SBS/tannin, and surviving organisms were enumerated. Two different experimental designs were employed. In the "unadapted" treatment, the S. Typhimurium was added at the beginning of the culture incubation along with cecal bacteria and chicken feed/SBS or chicken feed/SBS/tannin. In the "adapted" treatment, S. Typhimurium was added after a 24 hour pre-incubation of the cecal bacteria with the chicken feed/SBS or chicken feed/SBS/tannin. Adding SBS resulted in reduction of pH in the cultures which paralleled with the reduction of S. Typhimurium. The SBS alone was found to be inhibitory to S. Typhimurium in the adapted treatment at all concentrations tested (0.25, 0.5, and 0.75%), and the degree of inhibition was concentration-dependent. Salmonella Typhimurium was completely killed in the adapted culture with 0.5% SBS after 24 and 48 h. The SBS/tannin mixture was less inhibitory than SBS alone at the same concentrations in side-by-side comparisons. Testing at a 0.5% SBS concentration, chicken age had little or no effect on log reduction of S. Typhimurium relative to age-matched control cultures without SBS, but age did affect the absolute number of S. Typhimurium surviving, with the greatest decreases occurring at 2 and 4 weeks of age (approx. 10³ S. Typhimurium surviving) compared to 6 weeks of age (approx. 10⁵ Salmonella surviving). Microbiome analysis with an Illumina MiSeq platform was conducted to investigate bacterial compositional changes related to the addition of SBS. The relative abundance of Firmicutes (at the phylum level) was decreased, and genera Lactobacillus and Faecalibacterium were increased when SBS was added to the anaerobic mixed culture containing either fecal or cecal material. The antimicrobial action of feed-grade SBS may represent a potential pre-harvest control measure for Salmonella in poultry production.

Protein-L-Isoaspartyl Methyltransferase (PIMT) Is Required for Survival of Salmonella Typhimurium at 42°C and Contributes to the Virulence in Poultry

Poultry birds are asymptomatic reservoir of Salmonella Typhimurium (S. Typhimurium) but act as source of human infection for this bacterium. Inside the poultry, S. Typhimurium experiences several stresses, 42°C body temperature of birds is one of them. Proteins are highly susceptible to temperature mediated damage. Conversion of protein bound aspartate (Asp) residues to iso-aspartate (iso-Asp) is one of such modifications that occur at elevated temperature. Iso-Asp formation has been linked to protein inactivation and compromised cellular survival. Protein-L-isoaspartyl methyltransferase (PIMT) can repair iso-Asp back to Asp, thus enhances the cellular survival at elevated temperature. Here, we show that the pimt gene deletion strain of S. Typhimurium (Δpimt mutant strain) is hypersensitive to 42°C in vitro. The hypersusceptibility of Δpimt strain is partially reversed by plasmid based complementation (trans-complementation) of Δpimt strain. Following oral inoculation, Δpimt strain showed defective colonization in poultry caecum, and compromised dissemination to spleen and liver. Interestingly, we have observed three and half folds induction of the PIMT protein following exposure of S. Typhimurium to 42°C. Our data suggest a novel role of pimt gene in the survival of S. Typhimurium at elevated temperature and virulence.

Effective characterization of Salmonella Enteritidis by most probable number (MPN) followed by multiplex polymerase chain reaction (PCR) methods

Nontyphoidal Salmonella (NTS) is a relevant pathogen involved in gastroenteritis outbreaks worldwide. In this study, we determined the capacity to combine the most probable number (MPN) and multiplex polymerase chain reaction (PCR) methods to characterize the most important Salmonella serotypes in raw sewage. A total of 499 isolates were recovered from 27 raw sewage samples and screened using two previously described multiplex PCR methods. From those, 123 isolates were selected based on PCR banding pattern-identical or similar to Salmonella Enteritidis and Salmonella Typhimurium-and submitted to conventional serotyping. Results showed that both PCR assays correctly serotyped Salmonella Enteritidis, however, they presented ambiguous results for Salmonella Typhimurium identification. These data highlight that MPN and multiplex PCR can be useful methods to describe microbial quality in raw sewage and suggest two new PCR patterns for Salmonella Enteritidis identification.

Phenotypic and genotypic characterization of locally isolated Salmonella strains used in preparation of Salmonella antigens in Egypt

Aim:

This work was conducted to study the phenotypic and genotypic characterization of locally isolated Salmonella strains (Salmonella Pullorum, Salmonella Enteritidis, and Salmonella Typhimurium) from poultry used in the preparation of Salmonella antigens in Egypt.

Materials and Methods:

The phenotypic characterization of Salmonella strains was done using standard microbiological, biochemical, and serological techniques. Molecular identification was done using different sets of primers on different genes using different polymerase chain reaction (PCR) techniques.

Results:

The phenotypic characterization of Salmonella strains was confirmed. Molecular identification revealed detection of 284 bp fragment of InvA gene in all studied Salmonella strains. Furthermore, multiplex PCR was used for more confirmation of being Salmonella spp., generally at 429 bp as well as genotyping of Salmonella Typhimurium and Salmonella Enteritidis at 559 and 312 bp, respectively, in one reaction.

Conclusion:

The locally isolated field Salmonella strains were confirmed phenotypically and genotypically to be Salmonella Enteritidis, and Salmonella Typhimurium and could be used for the preparation of Salmonella antigens.

Assessing the Impact of Manure Application in Commercial Swine Farms on the Transmission of Antimicrobial Resistant Salmonella in the Environment

Land application of swine manure in commercial hog farms is an integral part of their waste management system which recycles the nutrients back to the soil. However, manure application can lead to the dissemination of bacterial pathogens in the environment and pose a serious public health threat. The aim of this study was to determine the dissemination of antimicrobial resistant Salmonella in the environment due to manure application in commercial swine farms in North Carolina (n = 6) and Iowa (n = 7), two leading pork producing states in the US. We collected manure and soil samples twice on day 0 (before and after manure application) from four distinct plots of lands (5 soil samples/plot) located at 20 feet away from each other in the field. Subsequent soil samples were collected again on days 7, 14, 21 from the same plots. A total of 1,300 soil samples (NC = 600; IA = 700) and 130 manure samples (NC = 60; IA = 70) were collected and analyzed in this study. The overall Salmonella prevalence was 13.22% (189/1,430), represented by 10.69% and 38.46% prevalence in soil and manure, respectively. The prevalence in NC (25.45%) was significantly higher than in IA (2.73%) (P<0.001) and a consistent decrease in Salmonella prevalence was detected from Day 0-Day 21 in all the farms that tested positive. Salmonella serotypes detected in NC were not detected in IA, thereby highlighting serotype association based on manure storage and soil application method used in the two regions. Antimicrobial susceptibility testing was done by the broth microdilution method to a panel of 15 antimicrobial drugs. A high frequency of isolates (58.73%) were multidrug resistant (resistance to three or more class of antimicrobials) and the most frequent resistance was detected against streptomycin (88.36%), sulfisoxazole (67.2%), and tetracycline (57.67%). Genotypic characterization by pulse field gel electrophoresis revealed clonally related Salmonella in both manure and soil at multiple time points in the positive farms. Our study highlights the potential role of swine manure application in the dissemination and persistence of antimicrobial resistant Salmonella in the environment.

Prevalence, Distribution, and Diversity of Salmonella spp. in Meat Samples Collected from Italian Slaughterhouses

Recently worldwide food safety authorities indicated the rise of foodborne outbreaks linked to Salmonella: this highlighted the need to intensify monitoring and apply more targeted controls to help manage the spread of the disease. The aim of this study was to assess the prevalence and distribution of Salmonella serotypes in 7 slaughterhouses, located in different areas of Naples province (Regione Campania, Italy). Meat samples collected from the slaughterhouses were submitted for standardized microbiological analysis in 2015. Results of routine testing for Salmonella spp. were analyzed and then compared to biochemical and molecular evaluations. Salmonella spp. were detected in 12% of 320 samples examined (39/320) and the isolation rates ranged from 87% (32 samples) for raw poultry meat to 13% (7 samples) for pork meat. Biochemical serotyping showed that approximately 50% of the isolates belonged to Salmonella enterica serotype Choleraesuis. Rapid detection methods, such as molecular analysis (polymerase chain reaction and gel electrophoresis), able to confirm food matrices contamination, represent a valid support to the fast identification of Salmonella species. A further aspect of the study consisted, indeed, on analyzing isolated strains through molecular evaluations. By amplifying bacterial DNA-using invA primers, selective for Salmonella-it was possible, in less than 3 h, to classify the isolates as Salmonella spp., confirming the results of microbiological outcomes. Results of distribution analysis, supported by rapid molecular approaches, showed the difficulty of reducing Salmonella risk on food chain. This emphasized the importance of periodic surveillance to prevent outbreaks.

Use of Pooled Samples for the Detection of Salmonella in Feces by Polymerase Chain Reaction

Many epidemiological studies of Salmonella rely on conventional bacteriological culture methods to detect Salmonella in fecal samples. These culture-based methods are inefficient for epidemiological studies in populations with a low prevalence of Salmonella. The objective of this study was to optimize a protocol that uses pooled Salmonella enrichment broth cultures of bovine feces and polymerase chain reaction (PCR) for the detection of the invA gene of Salmonella in feces. In one field trial, 196 animals were sampled, and all samples were tested by culture, invA PCR on individual samples, invA PCR on pools of 5 samples, and BAX PCR on individual samples. All assays showed a high agreement on individual samples (kappa ≥ 0.75). The invA PCR was run on each of 40 pools and detected 19 of 22 culture-positive pools. In another field trial, 152 samples were taken from 4 dairies, and the invA PCR was performed on pools of 5 samples in addition to bacteriological culture of individual samples. Salmonella was detected in 5 of the 32 pools (7 total positive samples) by both PCR and culture. One pool was PCR-positive but culture-negative. Pooling did not dramatically affect the performance of the invA PCR; most of the culture-positive samples were detected, including all of the samples when there were 4 or more Salmonella colonies on the agar plate. Based on these field trials, invA PCR on pooled samples appears to be an efficient method of Salmonella detection as long as Salmonella loads are not extremely low.

Molecular identification of Salmonella enterica subsp. enterica serovar Gallinarum biovars Gallinarum and Pullorum by a duplex PCR assay

Salmonella enterica subsp. enterica serovar Gallinarum biovar Gallinarum ( S. Gallinarum) and biovar Pullorum ( S. Pullorum) are 2 poultry pathogens that cause major economic losses to the poultry industry worldwide. Control of both diseases mainly relies on the adoption of biosecurity programs, and success is dependent on accurate and fast detection. Based on this concept, we developed a duplex PCR assay, targeting 2 chromosomal sequences, which allowed us to precisely identify and differentiate S. Gallinarum and S. Pullorum field strains. This assay was validated by testing genomic DNA from 40 S. Gallinarum and 29 S. Pullorum field strains, 87 other Salmonella serovars, and 7 non- Salmonella strains. The serovar identifier region (SIR) primers produced a fragment only in S. Gallinarum and S. Pullorum strains, whereas the fragment from the ratA coding sequence, which was previously demonstrated to differentiate the 2 biovars, was also amplified from other Salmonella serovars. Our results showed that the combination of both SIR and ratA amplifications could be used to identify as well as to differentiate colonies of S. Gallinarum and S. Pullorum reliably. Thus, we believe this methodology can be a useful ancillary tool for routine veterinary diagnostic laboratories by providing rapid, accurate results.