Efficacy of Lactobacillus animalis and Propionibacterium freudenreichii-Based Feed Additives in Reducing Salmonella-Associated Health and Performance Effects in Commercial Beef Calves

Salmonella enterica, which causes typhoid fever, is one of the most prevalent food-borne pathogens. Salmonellosis in cattle can greatly impact a producer’s income due to treatment costs, decreased productivity of the herd, and mortality due to disease. Current methods of treatment and prevention for salmonellosis consist of antibiotics and vaccinations, but neither of these options are perfect. Probiotics, categorized as antibiotic alternatives, are living microorganisms that are added to animal feeds in appropriate quantities in order to benefit health and productivity in adult and newborn livestock. The objective of this study was to demonstrate that Lactobacillus animalis and Propionibacterium freudenreichii, when used as a direct-fed microbial, was effective in reducing the adverse effects of experimentally induced Salmonella infection in beef calves. We conducted a single site efficacy study with masking using a randomized design comprising two groups of ten beef calves allocated to two treatment groups (control and probiotic). Procedures such as determining general health scores and body weight and collecting fecal samples were carried out following the experimental challenge of calves with Salmonella Typhimurium. The presence of at least one CFU of bacteria in feces was significantly higher among animals in the control than in the probiotic group, which was higher on days 0 to 7 than on days 8 to 14 (p = 0.012). Animals in the control group had a significantly higher presence of abnormal diarrhea scores than animals in the probiotic group (p < 0.001). Most notably, other health benefits in probiotic-fed group calves were obviously better than those for control calves and further substantiates the potential economic and health benefits of feeding effective probiotics.

Differential Effects of Bacitracin Methylene Disalicylate (BMD) on the Distal Colon and Cecal Microbiota of Young Broiler Chickens

Antibiotics have been used extensively for growth promotion in poultry, along with other food production animals, as well as therapeutically to treat infectious diseases. However, with concerns over selection for drug antibiotic resistant bacteria the practice of using subtherapeutic doses of antibiotics is under increased scrutiny. Consequently, we assessed the impact of the commonly used antibiotic bacitracin methylene disalicylate (BMD) on the gastrointestinal microbiota of chickens. For this we administered therapeutic doses of BMD as a feed additive and 16s rRNA gene amplicon sequencing to measure changes in taxonomic abundance on the distal colon and cecal microbiota of young broiler chickens. While BMD treatment was found to impact the abundance of selected taxa and overall beta diversity, significant changes were, in general, limited to the colon of the treated birds. Selected taxa at the phylum, class, and genus levels that were most impacted were identified. The composition of the cecum remained relatively stable in BMD-treated animals. As poultry production practices seek alternatives to growth promoting antibiotic feed additives, manipulation of the gastrointestinal microbiota holds promise. These results suggest that targeting the cecum may offer a means to promote changes to the microbiota that maximize the benefits for the hosts.

Impact of cyadox on human colonic microflora in chemostat models

The aim of this study was to evaluate the microbiological safety of cyadox, a new member of quinoxaline-1,4-dioxides (QdNOs), on human intestinal flora. Four chemostats containing human fecal flora were exposed to 0, 16, 32, and 128 μg/mL of cyadox, respectively. Bacterial populations, resistance rates of two predominant bacteria and short-chain fatty acids (SCFA) were monitored daily prior to and during drug MOA Laboratory of Risk Assessment for Quality and Safety of Livestock and Poultry Products exposure. Colonization resistance (CR) of each community was determined by three successive daily challenges of Salmonella typhimurium. Efflux pump gene (oqxAB) in the Escherichia coli and Enterococcus strains were analyzed by PCR amplification and DNA sequencing. No change in SCFA was observed after exposure to different concentrations of cyadox. Lower concentration of cyadox (16 μg/mL) had no adverse effect on human microflora. However, higher concentrations of cyadox (32 and 128 μg/mL) could change bacterial population and increase the proportion of resistant E. coli and Enterococcus. More than 26% (12/46) of cyadox resistant E. coli strains contained oqxAB gene, while all the resistant Enterococcus were negative to oqxAB gene. Relationship between the occurrence of oqxAB gene and cyadox exposure is inconclusive. Our data indicated that 16 μg/mL might be the no observed effect concentration (NOEC) of cyadox. Derived microbiological acceptable daily intake (mADI) would be 1552.03 μg/kg d. The data obtained in present study indicated that cyadox was a safe member of QdNOs family of antimicrobial agents.

Effect of lactic acid bacteria probiotic culture treatment timing on Salmonella Enteritidis in neonatal broilers

In the present study, a series of experiments were conducted to evaluate the ability of a combination of 3 ATCC lactobacilli (LAB3) or a commercially available probiotic culture (PROB) to reduce Salmonella enterica serovar Enteritidis (Salmonella Enteritidis) in broiler chicks. Additionally, we varied the timing of PROB administration in relationship to Salmonella challenge and determined the influence on recovery of enteric Salmonella. In experiments 1 to 3, chicks were randomly assigned to treatment groups and were then challenged via oral gavage with Salmonella Enteritidis. Chicks were treated 1 h after Salmonella Enteritidis challenge with LAB3 or PROB. Twenty-four hours posttreatment, cecal tonsils were collected for recovery of enteric Salmonella. In experiments 4 to 7, day-of-hatch chicks were randomly assigned to treatment groups and were then treated with PROB via oral gavage and placed into pens. Chicks were challenged with Salmonella Enteritidis 24 h after treatment via oral gavage. At 24 h after Salmonella Enteritidis challenge, cecal tonsils were collected and recovery of enteric Salmonella was determined. In experiments 8 to 10, 1-d-old chicks were randomly assigned to treatment groups and were then challenged via oral gavage with Salmonella Enteritidis and placed into pens. Chicks were treated 24 h after challenge with PROB via oral gavage. Twenty-four hours post PROB treatment, cecal tonsils were collected and enriched as described above. It was found that PROB significantly reduced cecal Salmonella Enteritidis recovery 24 h after treatment as compared with controls or LAB3-treated chicks in experiments 1 to 3 (P<0.05). Administration of PROB 24 h before Salmonella Enteritidis challenge significantly reduced recovery of Salmonella Enteritidis in 2 out of 4 experiments and no reduction in cecal Salmonella Enteritidis was observed when chicks were challenged with Salmonella Enteritidis and treated 24 h later with PROB. These data demonstrate that PROB more effectively reduced Salmonella Enteritidis than LAB3, and the timing of PROB treatment affects Salmonella Enteritidis-associated reductions.

The role of probiotics in the poultry industry

The increase of productivity in the poultry industry has been accompanied by various impacts, including emergence of a large variety of pathogens and bacterial resistance. These impacts are in part due to the indiscriminate use of chemotherapeutic agents as a result of management practices in rearing cycles. This review provides a summary of the use of probiotics for prevention of bacterial diseases in poultry, as well as demonstrating the potential role of probiotics in the growth performance and immune response of poultry, safety and wholesomeness of dressed poultry meat evidencing consumer's protection, with a critical evaluation of results obtained to date.

Probiotic bacteria are antagonistic to Salmonella enterica and Campylobacter jejuni and influence host lymphocyte responses in human microbiota-associated immunodeficient and immunocompetent mice

A defined human microbiota-associated (HMA) mouse model in BALB/c and immunodeficient Tgepsilon26 mice was used to assess the ability of probiotic lactobacilli and bifidobacteria to enhance colonization resistance to gastrointestinal (GI) tract pathogens. Probiotic bacteria (1x10(8) colony forming unit (CFU)/mL) successfully excluded Campylobacter jejuni from both strains of mice 7 days after challenge. The probiotic bacteria also reduced the number of Salmonella in the large intestines of both mouse strains. The nylon wool fractionated spleen lymphocyte populations were incubated with Salmonella or C. jejuni antigens. The probiotic treatments did not affect lymphocyte proliferation to C. jejuni antigens, but significantly increased proliferation of lymphocytes to Salmonella antigens by 68 and 55%, respectively, over untreated mice. Caspase 3/7 activation was significantly reduced 33 and 38% in the T and B lymphocyte fractions, respectively, of probiotic-treated, Salmonella-challenged HMA BALB/c mice, suggesting that lymphocyte rescue from apoptosis was occurring as a result of probiotic bacteria activity. These results revealed an immunosuppressive activity by Salmonella that was inhibited by the presence of probiotic bacteria. In summary, lactobacilli and bifidobacteria competitively excluded C. jejuni from immunocompetent and immunodeficient mice and antagonized an observable Salmonella-induced immunosuppression in immunocompetent mice.

In vitro model of colonization resistance by the enteric microbiota: effects of antimicrobial agents used in food-producing animals

A bioassay was developed to measure the minimum concentration of an antimicrobial drug that disrupts the colonization resistance mediated by model human intestinal microbiota against Salmonella invasion of Caco-2 intestinal cells. The bioassay was used to measure the minimum disruptive concentrations (MDCs) of drugs used in animal agriculture. The MDCs varied from 0.125 microg/ml for some broad-spectrum antimicrobial drugs (e.g., streptomycin) to 16 microg/ml for drugs with limited spectra of antimicrobial activity (e.g., lincomycin). The acceptable daily intake (ADI) residue concentration calculated on the basis of the MDCs were higher for erythromycin, lincomycin, and tylosin than the ADI residue concentrations calculated on the basis of the MICs. The MDC-based ADI values for apramycin, bacitracin, neomycin, novobiocin, penicillin G, streptomycin, tetracycline, and vancomycin were lower than the reported MIC-based ADI values. The effects of antimicrobial drugs at their MDCs on the bacterial composition of the microbiota were observed by denaturing gradient gel electrophoresis of 16S rRNA sequences amplified by PCR. Changes in the population composition of the model colonization resistance microbiota occurred simultaneously with reduced colonization resistance. The results of this study suggest that direct assessment of the effects of antimicrobial drugs on colonization resistance in an in vitro model can be useful in determining ADI values.

A comparative study on the effects of tylosin on select bacteria during continuous flow culture of mixed populations of gut microflora derived from a feral and a domestic pig

Continuous flow cultures of feral (culture FC) and domesticated (culture RPCF) pig gut microflora were established in steady state. Cultures were continuously infused with 25 or 100 microg tylosin/mL and sampled at intervals to assess effects on total culturable anaerobes, Bacteroides and Enterococcus via plating to agar supplemented without or with 100 microg tylosin/mL, the latter to assess bacterial sensitivity to tylosin. Endogenous tylosin-insensitive anaerobes within the cultures, while similar prior to tylosin administration, responded differently during tylosin administration, with concentrations in RPCF cultures becoming enriched more than in FC cultures. Tylosin-insensitive anaerobes in RPCF cultures persisted at increased concentrations after cessation of tylosin administration whereas concentrations in FC cultures decreased slightly. Concentrations of Bacteroides and endogenous Enterococcus recovered on medium without tylosin decreased to near or below detectable levels in FC cultures administered 25 or 100 microg tylosin/mL. Tylosin-insensitive Bacteroides were enriched to >5 log10 CFU/mL in RPCF cultures after 25 microg tylosin/mL but not at 100 microg tylosin/mL. Populations of endogenous tylosin-insensitive Enterococcus were enriched in RPCF but not FC cultures administered 25 or 100 microg tylosin/mL. In cultures administered 100 microg tylosin/mL, an exogenous-sourced E. faecium possessing tylosin resistance maintained itself only in the presence of tylosin. These results indicate that under the conditions of these tests, antibiotic exposure may enrich for antibiotic-insensitive bacteria populations of endogenous or exogenous origin but that the ability of an exogenous tylosin-resistant E. faecium to persist is reduced in the absence of the antibiotic, likely due to exclusion by native flora.

The effect of oral administration of a homologous hilA mutant strain on the long-term colonization and transmission of Salmonella Enteritidis in broiler chickens

The effect of pre-treatment with a homologous live Salmonella hilA mutant strain on the long-term colonization and transmission of Salmonella Enteritidis in broilers was evaluated. For this purpose, three treatment groups of newly hatched broilers were created. Each group consisted of 4 pens with 25 birds per pen. The first and second groups were orally inoculated with a Salmonella Enteritidis hilA mutant strain (Nal r) whereas the third group was not. In the second and third group, 20% of the birds were challenged 1 day later with a Salmonella Enteritidis wild type strain (Strep r). The Salmonella Enteritidis hilA mutant strain showed no residual virulence in the chicken host and was largely cleared from the chickens at 6 weeks of age. A significant long-term inhibition of faecal shedding and caecal and internal organ colonization of the wild type Salmonella Enteritidis strain was observed in the birds pre-treated with the hilA mutant strain. Although pre-treatment with a hilA mutant strain could not fully prevent the spread of Salmonella Enteritidis amongst the broilers, a significant reduction of transmission was observed in comparison to the non-pre-treated groups. The observed colonization-inhibition (CI) indicates that administration of live attenuated hilA mutant Salmonella strains to newly hatched chicks might, in combination with other protective control measures, contribute to the control of Salmonella infections in broilers.

Salmonellae reduction in poultry by competitive exclusion bacteria Lactobacillus salivarius and Streptococcus cristatus

The objective of this study was to develop a defined competitive exclusion bacteria (CE) culture that will prevent or substantially reduce Salmonella colonization of poultry. The efficacy of 56 potential CE isolates in preventing or reducing Salmonella colonization in chickens was determined. These potential CE were perorally administered to day-of-hatch chicks at 10(6) to 10(8) CFU per chick, and salmonellae were subsequently administered by gavage 2 days later at 5.5 x 10(3) to 5.0 x 10(4) CFU per chick. Feeding chickens an overnight CE culture of Lactobacillus salivarius strains Salm-9, List40-1,8, or List40-41 reduced Salmonella carriage in cecal contents by 2.10, 2.52, and 2.20 log CFU/g (average of three trials), respectively. The percentages of Salmonella-positive chickens after receiving these treatments were 35, 31, and 35% respectively, compared with 84% for the untreated control. A mixture of these three isolates had a similar effect when compared with the results of the individual isolates. A mixture of Streptococcus cristatus List40-13 and L. salivarius List40-41 reduced Salmonella carriage from 90 to 65% and 88 to 31% in two feeding trials, and by 2.2 and 4 log CFU/g of cecal contents of chickens. In conclusion, CE isolates L. salivarius Salm-9, List40-18, and List40-41 and S. cristatus List40-13 either individually or in combination were effective in significantly preventing Salmonella colonization of chickens.

A five-strain probiotic combination reduces pathogen shedding and alleviates disease signs in pigs challenged with Salmonella enterica Serovar Typhimurium

Salmonella spp. infection is a major cause of gastroenteritis, with many thousands of cases reported in the European Union every year. The use of probiotics offers the potential to improve this situation. Here, we investigate the effects of oral treatment of pigs with a defined lactic acid bacteria culture mixture on both clinical and microbiological signs of Salmonella enterica serovar Typhimurium infection. Fifteen weaned pigs blocked by sex and weight were administered control milk or a mixture of five probiotic strains as either a milk fermentate or milk suspension for a total of 30 days. The mixture consisted of two strains of Lactobacillus murinus and one strain each of Lactobacillus salivarius subsp. salivarius, Lactobacillus pentosus, and Pediococcus pentosaceous. Following probiotic administration for 6 days, animals were challenged orally with serovar Typhimurium; the health of the animals and the microbiological composition of their feces were monitored for 23 days postinfection. Animals treated with probiotic showed reduced incidence, severity, and duration of diarrhea. These animals also gained weight at a greater rate than control pigs administered skim milk. Mean fecal numbers of Salmonella were significantly reduced in probiotic-treated animals at 15 days postinfection (P = 0.01). The administered probiotic bacteria improved both the clinical and microbiological outcome of Salmonella infection. These strains offer significant benefit for use in the food industry and may have potential in human applications.

The Effect of an Experimental Chlorate Product on Salmonella Recovery of Turkeys when Administered Prior to Feed and Water Withdrawal

Previously, an experimental chlorate product (ECP) has been observed to reduce Escherichia coli and Salmonella infections in swine, cattle, and broilers. The following studies were performed to investigate the effects of different concentrations and durations of administering ECP on crop and ceca Salmonella typhimurium (ST) colonization of turkeys. In 2 separate trials, each conducted with 2 replicates, 15-wk-old turkey toms were challenged with 10(7) to 10(9) cfu of ST. In Experiment 1, toms were administered 0, 0.5, 1.0, 2.0, or 4.0x of ECP (a 1.0x concentration is equivalent to a 15 mM chlorate ion concentration) in the drinking water for 38 h. In Experiment 2, toms were administered a 2x concentration of ECP in the drinking water for 0, 14, 26, or 38 h prior to water withdrawal. All treatments were followed by a 10-h water withdrawal and an 8-h feed withdrawal prior to organ sampling. In Experiment 1, turkeys provided ECP had significantly (P < 0.05) lower populations and incidences of crop (>1.4 log reduction) and ceca (>0.6 log reduction) ST as compared with control birds (2.1 and 0.94 log ST average for all trials, respectively), with little or no additional benefit from administration of higher ECP concentrations. In Experiment 2, toms provided ECP had lower populations of crop (>2.2 log reduction) and ceca (>1.5 log reduction) ST when compared with controls (3.1 and 1.8 log ST, respectively). Again, there appeared to be little benefit in longer administration intervals on quantitative reduction of ST. These experiments suggest that the ECP significantly reduces Salmonella colonization in commercial turkeys when administered prior to feed and water withdrawal.

Efficacy and food safety considerations of poultry competitive exclusion products

Competitive exclusion (CE) products are anaerobic cultures of bacteria that are applied to poultry hatchlings to establish a protective enteric microbiota that excludes intestinal colonization by human food-borne pathogens. For safety of the poultry flock and human consumers, the identities of bacteria in CE products need to be known. A CE product is a culture of intestinal contents from adult chickens. It may be microbiologically defined by analysis of bacteria isolated from the culture, but many bacteria are hard to reliably isolate, identify, and characterize with conventional techniques. Sequence analysis of 16S ribosomal RNA (rRNA) genes may be more reliable than conventional techniques to identify CE bacteria. Bacteria in CE products may contain antimicrobial drug resistance and virulence mechanisms that could be transferred to the enteric bacteria of the food animal and to the human consumer. Detection methods for specific antimicrobial drug resistance and virulence genes and the integrase genes of conjugative transposons, mostly utilizing PCR technology, are being developed that can be applied to assess these risks in CE bacteria. With improvements in efficacy, bacterial identification, and detection and control of the possible risks of gene transfer, CE product technology can be made a more effective food safety tool.

Screening for bacillus isolates in the broiler gastrointestinal tract

Spores from a number of different Bacillus species are currently being used as human and animal probiotics, although their mechanisms of action remain poorly understood. Here we describe the isolation of 237 presumptive gut-associated Bacillus spp. isolates that were obtained by heat and ethanol treatment of fecal material from organically reared broilers followed by aerobic plating. Thirty-one representative isolates were characterized according to their morphological, physiological, and biochemical properties as well as partial 16S rRNA gene sequences and screening for the presence of plasmid DNA. The Bacillus species identified included B. subtilis, B. pumilus, B. licheniformis, B. clausii, B. megaterium, B. firmus, and species of the B. cereus group, whereas a number of our isolates could not be classified. Intrinsic properties of potential importance for survival in the gut that could be advantageous for spore-forming probiotics were further investigated for seven isolates belonging to five different species. All isolates sporulated efficiently in the laboratory, and the resulting spores were tolerant to simulated gastrointestinal tract conditions. They also exhibited antimicrobial activity against a broad spectrum of bacteria, including food spoilage and pathogenic organisms such as Bacillus spp., Clostridium perfringens, Staphylococcus aureus, and Listeria monocytogenes. Importantly, the isolates were susceptible to most of the antibiotics tested, arguing that they would not act as donors for resistance determinants if introduced in the form of probiotic preparations. Together, our results suggest that some of the sporeformers isolated in this study have the potential to persist in or transiently associate with the complex gut ecosystem.

Effect of experimental chlorate product administration in the drinking water on Salmonella typhimurium contamination of broilers

The crop is a known source of Salmonella and Campylobacter contamination. Previously, we evaluated lactic acid in the drinking water during a simulated pretransport feed withdrawal (FW) and reported 0.44% lactic acid significantly (P < 0.05) reduced the number of Salmonella recovered in market-age broiler crops. However, total consumption of the organic acid-treated drinking water was reduced. Presently, we evaluated the effect of experimental chlorate product (ECP; 1x ECP is equivalent to a 15 mM chlorate ion concentration) during a 10-h pretransport FW. Market-age broilers were obtained from a commercial processing plant and randomly assigned to ECP-treated or control (nontreated) groups. Broilers were challenged by crop gavage with 10(8) Salmonella Typhimurium (ST) immediately upon arrival and 1 d prior to termination of the experiment. One day later, broilers were killed for ST enumeration (cfu) in the crop and ceca. Broilers provided ECP 24 h prior to slaughter consumed slightly more ECP water than broilers provided distilled water. Treatment with ECP caused a significant decrease (P < 0.05) in the incidence of ST in crop contents (2%) as compared to the controls (36.7%). Similarly, ECP treatment caused a significant decrease (P < 0.05) in number of ST (0.96 log10 ST/g cecal content) detected in the ceca when compared to controls (2.52 log10 ST). This study suggested that incorporation of ECP in the drinking water 24 to 48 h prior to slaughter could reduce Salmonella contamination in broilers.

Antimicrobial use and resistance in animals

Food animals in the United States are often exposed to antimicrobials to treat and prevent infectious disease or to promote growth. Many of these antimicrobials are identical to or closely resemble drugs used in humans. Precise figures for the quantity of antimicrobials used in animals are not publicly available in the United States, and estimates vary widely. Antimicrobial resistance has emerged in zoonotic enteropathogens (e.g., Salmonella spp., Campylobacter spp.), commensal bacteria (e.g., Escherichia coli, enterococci), and bacterial pathogens of animals (e.g., Pasteurella, Actinobacillus spp.), but the prevalence of resistance varies. Antimicrobial resistance emerges from the use of antimicrobials in animals and the subsequent transfer of resistance genes and bacteria among animals and animal products and the environment. To slow the development of resistance, some countries have restricted antimicrobial use in feed, and some groups advocate similar measures in the United States. Alternatives to growth-promoting and prophylactic uses of antimicrobials in agriculture include improved management practices, wider use of vaccines, and introduction of probiotics. Monitoring programs, prudent use guidelines, and educational campaigns provide approaches to minimize the further development of antimicrobial resistance.

Effects of rearing conditions on the colonization of Salmonella enteritidis in the cecum of chicks

Salmonella enteritidis is the cause of human salmonellosis associated with contaminated eggs. In this study, we artificially challenged S. enteritidis to chicks just after hatching, and the effects of breeding conditions on the intestinal carriage of S. enteritidis were examined. S. enteritidis was not directly detected from spleen, liver and blood, but were constantly isolated from the cecal contents throughout the experiment. When chicks were reared in the unsanitary conditions and in the high housing density, the numbers of S. enteritidis increased. The subsequent experiment was undertaken to examine whether the antibacterial additive in a feed would have any impact on S. enteritidis colonization in chicks. Some antibiotic effective on the growth promotion had an influence on S. enteritidis colonization.

In vitro inhibition of Salmonella organisms isolated from reptiles by an inactivated culture of microcin-producing Escherichia coli

OBJECTIVE

To determine whether an inactivated culture of a microcin-producing avian Escherichia coli was capable of killing Salmonella isolates from reptiles in an in vitro test system.

SAMPLE POPULATION

57 Salmonella isolate from reptiles.

PROCEDURE

A wild-type avian E. coli electrotransformed with a plasmid coding for the production of microcin 24 was tested in an in vitro microassay system for its ability to kill 57 Salmonella spp isolated from reptiles. The reptile population included snakes, iguana, frilled lizards, turtles, other lizards, and unspecified reptiles.

RESULTS

44 of the Salmonella isolates were inhibited strongly, compared with the in vitro assay controls; 12 had weak inhibition, and 1 was not inhibited by the microcin-producing E. coli. Thirteen of the 57 isolates had resistance to at least 1 antibiotic, primarily streptomycin. There were 9 O serogroups identified in the 57 isolates, with serogroup H being the most prevalent (18 to 57).

CONCLUSION AND CLINICAL RELEVANCE

Antibiotics are not recommended to eliminate Salmonella organisms from reptiles because of the development of antibiotic resistance. Further studies are necessary to determine whether the use of microcin-producing bacteria will be effective in controlling Salmonella infections in companion reptiles.

Foodborne infections

The role of foodborne infections in the health of the population has become of major concern recently. Numerous agents are transmitted in food and water and typically result in acute gastroenteritis, although long-term complications such as reactive arthritis (due to Salmonella, Yersinia, and Shigella organisms), Guillain-Barré syndrome (due to Campylobacter organisms), and renal failure (due to Escherichia coli) are now well recognized. The development of FoodNet to follow the epidemiology of select foodborne infections in the United States has been a major advance in recent years and is now beginning to show interesting trends. Our understanding of the pathogenesis of some of the major foodborne pathogens, especially Salmonella, is advancing and the genome sequencing of these organisms will advance the field further. Of particular concern of late is the increasing number of antibiotic-resistant bacterial isolates, especially for Salmonella and Campylobacter. Irrespective of their cause, these changes in susceptibility patterns pose a major threat to the appropriate treatment of patients. Overall, our knowledge of foodborne infections is advancing rapidly, but new factors such as the emergence of antibiotic resistance means that vigilance must be maintained.