Host-adapted Serovars Research Articles

Clonal relation between Salmonella enterica subspecies enterica serovar Dublin strains of bovine and food origin in Germany.

Salmonella enterica subspecies enterica serovar Dublin (S. Dublin) is a host-adapted serovar causing enteritis and/or systemic diseases in cattle. As the serovar is not host-restricted, it may cause infections in other animals, including humans with severe illness and higher mortality rates than other non-typhoidal serovars. As human infections are mainly caused by contaminated milk, milk products and beef, information on the genetic relationship of S. Dublin strains from cattle and food should be evaluated. Whole-genome sequencing (WGS) of 144 S. Dublin strains from cattle and 30 strains from food origin was performed. Multilocus sequence typing (MLST) revealed mostly sequence type ST-10 from both, cattle and food isolates. In total, 14 of 30 strains from food origin were clonally related to at least one strain from cattle, as detected by core-genome single nucleotide polymorphisms typing as well as core-genome MLST. The remaining 16 foodborne strains fit into the genome structure of S. Dublin in Germany without outliers. WGS proved to be a powerful tool not only to gain information on the epidemiology of Salmonella strains but also to detect clonal relations between organisms isolated from different stages of production. This study has shown a high genetic correlation between S. Dublin strains from cattle and food and, therefore, the potential to cause human infections. S. Dublin strains of both origins share an almost identical set of virulence factors, emphasizing their potential to cause severe clinical manifestations in animals, but also in humans and thus the need for effective control of S. Dublin in a farm-to-fork strategy.

Salmonella in Poultry; An Overview

An essential part of commercial poultry production is safeguarding flocks of birds against contamination by unwanted microorganisms. Currently, a serious issue called salmonellosis poses a threat to the chicken industry globally. The two most virulent serovars in avian species, Salmonella gallinarium and Salmonella pullorum (Fowl Typhoid) cause systemic infection and significant financial losses in the poultry sector. Salmonella nontyphoidal serotypes (Paratyphoid illness) pose a risk to the public's health because of their role in cases of food poisoning and their significance as zoonotic agents. All animals, including humans, can transmit the intestinal bacterium known as salmonella. Out of a total of 2500 serovars, Salmonella pullorum (pullorum illness) and S. gallinarum (bird typhoid) are the two host-adapted serovars that primarily harm poultry. Salmonella can spread horizontally from contaminated environments to birds as well as vertically from parent flocks to offspring. The danger of the introduction and persistence of infections can be substantially reduced by good management of biosecurity. This study is an overview of Salmonella in poultry which tell us some diagnostic and treatment of salmonella. By reading this study people will get sound knowledge regarding salmonella even they will be able to do desirable management in order to save their birds from Salmonella.

Genomic insights into Salmonella Choleraesuis var. Kunzendorf outbreak reveal possible interspecies transmission

Salmonella enterica serovar Choleraesuis is a host-adapted serovar that causes serious infections in domestic pigs and wild boars. Here, we investigated an outbreak of salmonellosis in domestic pigs in Slovenia, 2018–2019. To assess the outbreak, 18 isolates from domestic pigs, wild boars, wild boar meat and a human patient underwent whole-genome sequencing (WGS). All isolates were of sequence type (ST) 145 and harbored no antimicrobial resistance genes or AMR-associated mutations. A single transmission cluster (≤ 6 alleles) of spatially (< 100 km) and temporally linked isolates was observed, comprising isolates of pig (n = 9), wild boar (n = 2) and human (n = 1) origin, and suggesting possible interspecies transmission. In all outbreak-related animal cases, septicemic salmonellosis was observed, accompanied in some cases by enteric symptoms. All pig isolates were linked to a single intensive breeding farm that distributed growers to small family farms. The same transport vehicles were used to distribute growers to family farms and also to transport livestock between neighboring countries. Both isolates that originated from the imported wild boar meat were genetically distant (≥ 122 alleles) from the outbreak cluster. The present results indicate the importance of screening domestic pigs and proper disinfection of transport vehicles to control the spread of S. Choleraesuis.

Epidemiological Analysis of Salmonella enterica subsp. enterica Serovar Dublin in German Cattle Herds Using Whole-Genome Sequencing.

ABSTRACTSalmonella enterica subsp. enterica serovar Dublin is a cattle-adapted serovar that causes enteritis and systemic diseases in animals. In Germany, S. Dublin is not detected or is very rarely detected in some federal states but is endemic in certain regions. Information on detailed genetic characteristics of S. Dublin is not available. An understanding of the paths and spreading of S. Dublin within and between regions and over time is essential to establish effective control strategies. Whole-genome sequencing (WGS) and bioinformatic analysis were used to explore the genetic traits of S. Dublin and to determine their epidemiological context. Seventy-four S. Dublin strains collected in 2005 to 2018 from 10 federal states were studied. The phylogeny was analyzed using core-genome single-nucleotide polymorphisms (cgSNPs) and core-genome multilocus sequence typing. Genomic clusters at 100 cgSNPs, 40 cgSNPs, and 15 cgSNPs were selected for molecular epidemiology. WGS-based genoserotyping confirmed serotyping. Important specific virulence determinants were detected in all strains, but multidrug resistance in German S. Dublin organisms is uncommon. Use of different thresholds for cgSNP analysis enabled a broad view and also a detailed view of the occurrence of S. Dublin in Germany. Genomic clusters could be allocated nationwide, to a limited number of federal states, or to special regions only. Results indicate both persistence and spread of S. Dublin within and between federal states in short and longer time periods. However, to detect possible routes of infection or persistence of S. Dublin indicated by genomic analysis, information on the management of the cattle farms and contacts with corresponding farms are essential.IMPORTANCE Salmonella enterica subsp. enterica serovar Dublin is a bovine host-adapted serovar that causes up to 50% of all registered outbreaks of salmonellosis in cattle in Germany. S. Dublin is not detected or is only rarely detected in some federal states but has been endemic in certain regions of the country for a long time. Information on genetic traits of the causative strains is essential to determine routes of infection. WGS and bioinformatic analysis should be used to explore the genetic characteristics of S. Dublin. Combining the genomic features of S. Dublin strains with information on the management of the cattle farms concerned should enable the detection of possible routes of infection or persistence of S. Dublin. This approach is regarded as a prerequisite to developing effective intervention strategies.

Equine leptospirosis: Experimental challenge of Leptospira interrogans serovar Bratislava fails to establish infection in naïve horses.

Little information is available about experimental inoculation of leptospirosis in horses and the pathogenicity of Leptospira interrogans serovar Bratislava in this host. To determine the serological, clinical, pathological and haematological responses of horses to L. interrogans serovar Bratislava strain PigK151. Randomised controlled in vivo experiment. Ten seronegative female foals were divided into 2 groups, control (n=4) and challenged (n=6). The challenged group received 1×109 leptospires divided equally between topical ocular and intraperitoneal injections. Blood and urine samples were analysed. The temperature was recorded daily for the first 9days, then weekly. Sera were tested by microscopic agglutination test (MAT). Automated complete blood count, differential and chemistry panel were performed. Histopathological analysis was performed on sections of liver, kidney, urinary bladder, uterine body and pineal gland. Sample culturing was performed from blood, urine, liver, kidney, reproductive tract and vitreous humour. No pyrexia was noted. PCR and culture were negative from all samples. Differences between groups were found in CBC, differential counts and serum biochemistry panel (or profile), suggesting that leptospiral challenge triggered an inflammatory response. No evidence of leptospirosis was found from histopathological analysis. All challenged foals developed a humoral response. The MAT allowed the confirmation of the infecting serovar at a later stage, but it also revealed cross-reactive results that were further explained by genomic analysis. This experimental challenge had two main limitations: (a) the results might have varied if another strain from the same serovar had been used and (b) the use of another route of infection and a higher bacterial dose might have achieved colonisation. Based on these findings, it may suggest that L. interrogans serovar Bratislava is neither pathogenic nor host-adapted serovar for horses, although these results might have varied if another strain from the same serovar had been used instead.

Leptospiral shedding and seropositivity in shelter dogs in the Cumberland Gap Region of Southeastern Appalachia.

BackgroundLeptospirosis, caused by pathogenic Leptospira spp., is a zoonotic infection that affects humans, dogs and many other mammalian species. Virtually any mammalian species can act as asymptomatic reservoir, characterized by chronic renal carriage and shedding of a host-adapted leptospiral serovar. Environmental contamination by chronic shedders results in acquisition of infection by humans and susceptible animals.MethodsIn this study, we investigated if clinically normal shelter dogs and cats harbor leptospires in their kidneys by screening urine samples for the presence of leptospiral DNA by a TaqMan based-quantitative PCR (qPCR) that targets pathogen-associated lipl32 gene. To identify the infecting leptospiral species, a fragment of leptospiral rpoB gene was PCR amplified and sequenced. Additionally, we measured Leptospira-specific serum antibodies using the microscopic agglutination test (MAT), a gold standard in leptospiral serology.ResultsA total of 269 shelter animals (219 dogs and 50 cats) from seven shelters located in the tri-state area of western Virginia, eastern Tennessee, and southeastern Kentucky were included in this study. All cats tested negative by both qPCR and MAT. Of the 219 dogs tested in the study, 26/198 (13.1%, 95% CI: 8.4–17.8%) were positive for leptospiral DNA in urine by qPCR and 38/211 (18.0%, 95% CI: 12.8–23.2%) were seropositive by MAT. Twelve dogs were positive for both qPCR and MAT. Fourteen dogs were positive by qPCR but not by MAT. Additionally, leptospiral rpoB gene sequencing from a sub-set of qPCR-positive urine samples (n = 21) revealed L. interrogans to be the leptospiral species shed by dogs.ConclusionsThese findings have significant implications regarding animal and public health in the Cumberland Gap Region and possibly outside where these animals may be adopted.

Association of Salmonella virulence factor alleles with intestinal and invasive serovars

BackgroundThe role of Salmonella virulence factor (VF) allelic variation in modulating pathogenesis or host specificity has only been demonstrated in a few cases, mostly through serendipitous findings. Virulence factor (VF) alleles from Salmonella enterica subsp. enterica genomes were compared to identify potential associations with the host-adapted invasive serovars Typhi, Dublin, Choleraesuis, and Gallinarum, and with the broad host-range intestinal serovars Typhimurium, Enteritidis, and Newport.ResultsThrough a bioinformatics analysis of 500 Salmonella genomes, we have identified allelic variants of 70 VFs, many of which are associated with either one of the four host-adapted invasive Salmonella serovars or one of the three broad host-range intestinal serovars. In addition, associations between specific VF alleles and intra-serovar clusters, sequence types (STs) and/or host-adapted FimH adhesins were identified. Moreover, new allelic VF associations with non-typhoidal S. Enteritidis and S. Typhimurium (NTS) or invasive NTS (iNTS) were detected.ConclusionsBy analogy to the previously shown association of specific FimH adhesin alleles with optimal binding by host adapted Salmonella serovars, lineages or strains, we predict that some of the identified association of other VF alleles with host-adapted serovars, lineages or strains will reflect specific contributions to host adaptation and/or pathogenesis. The identification of these allelic associations will support investigations of the biological impact of VF alleles and better characterize the role of allelic variation in Salmonella pathogenesis. Most relevant functional experiments will test the potential causal contribution of the detected FimH-associated VF variants in host adapted virulence.

Identification of Bacterial Species That Can Utilize Fructose-Asparagine.

Salmonella enterica serovar Typhimurium is the only organism demonstrated to utilize fructose-asparagine (F-Asn) as a source of carbon and nitrogen. In this report, we first used a bioinformatics approach to identify other microorganisms that encode homologs of the Salmonella F-Asn utilization enzymes FraB (deglycase), FraD (kinase), and FraE (asparaginase). These candidate organisms were then tested with up to four different methods to confirm their ability to utilize F-Asn. The easiest and most broadly applicable method utilized a biological toxicity assay, which is based on the observation that F-Asn is toxic to a Salmonella fraB mutant. Candidate organisms were grown in a rich medium containing F-Asn, and depletion of F-Asn from the medium was inferred by the growth of a Salmonella fraB mutant in that same medium. For select organisms, the toxicity assay was cross-validated by direct mass spectrometry-aided measurement of F-Asn in the spent-culture media and through demonstration of FraB and FraD enzyme activity in cellular extracts. For prototrophs, F-Asn utilization was additionally confirmed by growth in a minimal medium containing F-Asn as the sole carbon source. Collectively, these studies established that Clostridiumbolteae, Clostridium acetobutylicum, and Clostridium clostridioforme can utilize F-Asn, but Clostridium difficile cannot; Klebsiella oxytoca and some Klebsiella pneumoniae subspecies can utilize F-Asn; and some Citrobacter rodentium and Citrobacter freundii strains can also utilize F-Asn. Within Salmonella enterica, the host-adapted serovars Typhi and Paratyphi A have lost the ability to utilize F-Asn.IMPORTANCE Fructose-asparagine (F-Asn) is a precursor to acrylamide that is found in human foods, and it is also a nutrient source for Salmonella enterica, a foodborne pathogen. Here, we determined that among the normal intestinal microbiota, there are species of Clostridium that encode the enzymes required for F-Asn utilization. Using complementary experimental approaches, we have confirmed that three members of Clostridium, two members of Klebsiella, and two members of Citrobacter can indeed utilize F-Asn. The Clostridium spp. likely compete with Salmonella for F-Asn in the gut and contribute to competitive exclusion. FraB, one of the enzymes in the F-Asn utilization pathway, is a potential drug target because inhibition of this enzyme leads to the accumulation of a toxic metabolite that inhibits the growth of Salmonella species. This study identifies the potential off-target organisms that need to be considered when developing therapeutics directed at FraB.

Detection of Some SalmonellaEnteritidisVirulence Genes by Multiplex-PCR Assay Using Two Different DNA Extraction Methods

The aim of this study was screeningsome Salmonella genus-specific virulence genes by multiplex-PCR technique using a group of primers targeting InvA,SipB,SpiA,CdtB,PefA genes using two different DNA extraction methods. A total of fifteen Salmonella isolates from patient's stool samples were collected. Suspected colonies onHiChromeRajhans (HCR) Medium and XLD medium were selected, and biochemical and serological tests were then performed for identification of Salmonella. Identification of Salmonella serotypes was done in Central Public Health Laboratory (CPHL) with O and H antisera. Extraction of bacterial genome was down by boiling method and salting out method using commercial kit (Wizard® Genomic DNA purification Kit). The results showed that all screened genes (chromosomally and plasmid-mediated) were found in all tested SalmonellaEnteritidis strains except cdtB gene which is thought to be limited only to certain SalmonellaTyphi andS.Paratyphi A strains. Moreover,the presence of pefA gene could be depending on host-adapted serovars. Boiling extraction method and commercial kit both gave a good result in multiplex-PCR technique. In conclusion, the results from this study of occurrence of SPIs genes support previous studies suggesting that these virulence genes are widely distributed among Salmonella and required for full Salmonella virulence, in addition, the boiling method was good, easy and specific method for multiplex-PCR technique.

The Novel Type 1 Fimbriae FimH Receptor Calreticulin Plays a Role in Salmonella Host Specificity.

It was suggested that minor differences in the structure of FimH are most likely associated with differences in its adhesion specificities and may determine the tropism of various Salmonella serovars to different species and tissues. We have recently shown that FimH adhesins from host-adapted serovars, e.g., Salmonella Choleraesuis (SCh), bind to other glycoprotein receptors compared to FimH from host-unrestricted Salmonella Enteritidis (SE). Here we identify porcine calreticulin expressed by swine intestinal cells as a host-specific receptor for SCh FimH adhesin, suggesting that such an interaction may contribute to SCh host specificity. Calreticulin was identified by 2D electrophoresis and mass spectrometry as a glycoprotein that was bound specifically by recombinant SCh FimH protein, but not by FimH from SE. The functionality of calreticulin as a specific receptor of SCh FimH adhesin was further confirmed by adhesion and invasion of mutated strains of SCh carrying different variants of FimH proteins to IPEC-J2 cells with overexpression and silenced expression of calreticulin. It was found that SCh carrying the active variant of FimH adhered and invaded IPEC-J2 cells with calreticulin overexpression at significantly higher numbers than those of SCh expressing the non-active variant or SE variant of FimH. Moreover, binding of SCh carrying the active variant of FimH to IPEC-J2 with silenced calreticulin expression was significantly weaker. Furthermore, we observed that SCh infection induces translocation of calreticulin to cell membrane. All of the aforementioned results lead to the general conclusion that Salmonella host specificity requires not only special mechanisms and proteins expressed by the pathogen but also specifically recognized receptors expressed by a specific host.

Plurality of Leptospira strains on slaughtered animals suggest a broader concept of adaptability of leptospires to cattle

Leptospirosis in bovines is in majority determined by the host-adapted serovars, mainly Hardjo (types Hardjoprajitno and Hardjobovis), that belong to the serogroup Sejroe. Members of other serogroups as Pomona and Tarassovi have been eventually reported, mainly when outbreaks occurs. Nevertheless, the real role of other strains (non-Hardjo) on determining disease or being transmitted by cattle free of apparent clinical signs of acute infection remains to be elucidated. In that context, the aim of the present study was to investigate the hypothesis that strains of serovars/serogroups other than Hardjo may also be maintained and shed by cattle free of clinical signs. Samples of urine and/or vaginal fluid were collected from 697 bovines from a slaughterhouse located close to Rio de Janeiro, Brazil. Culturing yielded 19 isolates what represents the largest number ever obtained in Brazil on similar studies. These strains were serogrouped and genetically characterized. Fifteen of those were described in other papers and four are first described on the present study. Isolates belong to three different species (Leptospira santarosai, L. alstonii and L. interrogans) and five serogroups (Sarmin, Tarassovi, Shermani, Grippotyphosa and Sejroe). The majority (84.2%) of the isolates belongs to the species L. santarosai, the most prevalent species on cattle in the studied region. Non-Hardjo (non-Sejroe) strains represent 57.9% of the isolates, what indicates an unexpected high diversity of serogroups obtained from these cattle. This suggest that non-Hardjo (non-Sejroe) strains may also be maintained and shed by cattle and that finding must be considered in the epidemiology and control of the disease.

Salmonellosis in Poultry - An Overview

Protecting poultry flocks from contamination by undesirable micro-organisms is an extremely important component of commercial poultry production. The introduction of a highly pathogenic, contagious disease organism into poultry flocks could result in serious economic consequences for the whole society. Salmonella are intestinal bacteria that can be transmitted by all animals, including humans. Out of total 2500 serovars the two host-adapted serovars, Salmonella pullorum (pullorum disease) and S. gallinarum (fowl typhoid) mainly affect the poultry. Salmonella can be transmitted both vertically from parent flocks to progeny and horizontally from contamination in the environment to the birds. Good management and bio-security can reduce the risk of introduction and persistence of infections to minimal levels.

Infectious abortion caused by Salmonella enterica subsp enterica serovar Abortusequi in Argentina

The equine host-adapted serovar, Salmonella enterica subsp enterica (See) serovar Abortusequi (SeeA) cause a disease called equine paratyphoid. The disease is manifested as abortion with other signs, including fistulous withers, septicemia, and arthritis. SeeA is transmitted by the ingestion of contaminated food with uterine secretions of aborted mares [1]. Different episodes of reproductive failure have recently been reported at several farms in the Province of Buenos Aires. Some of these episodes were studied at the Laboratory-School of Diagnosis of Infectious Diseases at the Veterinary University, and in two of these cases, the isolation of the SeeA bacterium was posible. The recovery of this bacterium gives an alarm signal; therefore, we should reconsider former agents responsible for reproductive diseases which now re-emerge due to the lack or discontinuation of preventive immunizations or due to critical points that we should not dismiss when considering the epidemiology of the agent. The objective of this study is to identify the cause of abortions that showed clinical, anatomic and pathological features of the bacterial abortions reported at different farms. Placentas from aborted mares and aborted fetuses were examined. For the isolation of bacteria, heart blood, liver, spleen, lung, intestine and stomach content were cultured in pre enrichment and selective enrichment medium. The enrichment medium was streaked onto XLD and MacConkey agar plates. Salmonella like isolates were identified by biochemical analysis using primary and secondary test as described Cowan and Steel, 2003. [2] The serotype was verified at the Bacteriology Departament, INEI ANLIS Dr. Carlos G. Malbran. Dra. Maria Ines Caffer, Three placentas from aborted mares and three aborted fetuses were examined. Fibrinonecrotic exudates or congestion were observed at the placentas. Liver and lung congestions and intestine petechial hemorrhages were observed at the fetuses. See was isolated from two fetuses from heart blood, liver, spleen and lung. UBA 874 Salmonella Abortusequi (4,12:-:e,n,x) and UBA 879 Salmonella Abortusequi (4,12:-:e,n,x) were identified from the two spleens. The strains were used for developing formalin-inactivated bacterins in Tymerosal and OHAl adjuvant. The SeeA is a hard-to-isolate bacterium so in this study it was isolated in two samples only. Both isolated samples were enough to conclude that we are facing a reemerging disease. It is known that animals with positive serologic response as well as vaccinated animals cannot be reinfected by the Salmonella bacterium. The complete aborted animal, fetal organs, placenta or even fecal material are adequate samples for cultivation since isolation and identifications provide the definitive diagnosis.

Evolution of Salmonella enterica Virulence via Point Mutations in the Fimbrial Adhesin

Whereas the majority of pathogenic Salmonella serovars are capable of infecting many different animal species, typically producing a self-limited gastroenteritis, serovars with narrow host-specificity exhibit increased virulence and their infections frequently result in fatal systemic diseases. In our study, a genetic and functional analysis of the mannose-specific type 1 fimbrial adhesin FimH from a variety of serovars of Salmonella enterica revealed that specific mutant variants of FimH are common in host-adapted (systemically invasive) serovars. We have found that while the low-binding shear-dependent phenotype of the adhesin is preserved in broad host-range (usually systemically non-invasive) Salmonella, the majority of host-adapted serovars express FimH variants with one of two alternative phenotypes: a significantly increased binding to mannose (as in S. Typhi, S. Paratyphi C, S. Dublin and some isolates of S. Choleraesuis), or complete loss of the mannose-binding activity (as in S. Paratyphi B, S. Choleraesuis and S. Gallinarum). The functional diversification of FimH in host-adapted Salmonella results from recently acquired structural mutations. Many of the mutations are of a convergent nature indicative of strong positive selection. The high-binding phenotype of FimH that leads to increased bacterial adhesiveness to and invasiveness of epithelial cells and macrophages usually precedes acquisition of the non-binding phenotype. Collectively these observations suggest that activation or inactivation of mannose-specific adhesive properties in different systemically invasive serovars of Salmonella reflects their dynamic trajectories of adaptation to a life style in specific hosts. In conclusion, our study demonstrates that point mutations are the target of positive selection and, in addition to horizontal gene transfer and genome degradation events, can contribute to the differential pathoadaptive evolution of Salmonella.

Acute Respiratory Failure Caused by Leptospira spp. in 5 Foals

A lthough clinical disease in horses is uncommon, serological surveys show that equine exposure to leptospires is very common. In some populations, up to 80% of the animals have leptospiral antibodies. In Europe, Leptospira interrogans serovar bratislava, copenhageni, and patoc are the presumed host-adapted serovars of horses. Clinical leptospirosis in horses is primarily associated with recurrent uveitis, abortions, stillbirth, neonatal disease, hemolysis, renal disease, and liver disease. Unlike cases in humans or small animals, respiratory signs caused by alveolar hemorrhage have not been associated with leptospirosis. The present report describes 5 cases of foals with respiratory distress caused by leptospirosis.

Characterisation of antibiotic resistance in host-adapted Salmonella enterica

Salmonella enterica serovars Dublin, Choleraesuis and Pullorum are host-adapted serovars that cause disease primarily in cattle, swine and poultry, respectively. In addition, serovars Dublin and Choleraesuis are important human pathogens that are disproportionately associated with severe invasive infections that require antimicrobial therapy. Because of the potential increased emergence and spread of antimicrobial resistance, isolates of 42 S. enterica serovars Dublin, Choleraesuis and Pullorum were characterised to evaluate resistance. Antimicrobial susceptibility testing, detection of resistance genes and integrons, pulsed-field gel electrophoresis and plasmid analysis were carried out to characterise the isolates. Seventy-nine percent of the isolates were resistant to at least one of the antimicrobial agents tested, whilst 38% of the isolates were resistant to six or more antimicrobial agents. Resistance was most commonly detected to tetracycline (64%), streptomycin (57%) and kanamycin (52%). Overall, when resistance was seen, a corresponding resistance gene was detected 86.7% of the time. The results of this study indicate that antimicrobial resistance is a major concern in serovars Dublin and Choleraesuis isolates owing to the presence of multidrug resistance.

Effects of feeding Salmonella enterica serovar Typhimurium or serovar Choleraesuis on growth performance and circulating insulin-like growth factor-I, tumor necrosis factor-α, and interleukin-1β in weaned pigs1

The most common Salmonella serovars causing clinical disease in pigs are Salmonella enterica serovars Typhimurium (Typhimurium) and Choleraesuis. Given that the swine host-adapted serovar Choleraesuis has been reported to cause systemic disease, a different disease outcome from that of Typhimurium, our working hypothesis was that this serovar would likely engage systemic immune-inflammatory mechanisms, resulting in elevated systemic cytokine secretion. Forty-eight weaned pigs were blocked by BW and sex, and randomly allotted to 1 of 3 treatments in a 14-d study. Each treatment had 8 replicates (pens), with 2 pigs/pen. The treatments consisted of a negative control and pigs repeatedly fed 10(8) cfu of Typhimurium or Choleraesuis. On d 0, the pigs were fed Choleraesuis or Typhimurium in dough balls, and the bacteria were refed twice weekly throughout the experiment. Control pigs received dough balls without bacteria. All pigs were housed in temperature-controlled rooms under constant lighting and were fed a standard corn-soybean meal-based nursery diet. Pig BW and feed disappearance were used to determine ADG, ADFI, and G:F. Rectal temperatures were obtained daily from 1 pig/pen beginning 2 d before the first bacterial feeding through d 7 using rapid-response digital thermometers. Serum was collected on d 0, 7, and 14 from a single pig/pen for analysis of IGF-I, tumor necrosis factor-alpha , and IL-1beta. There was no change in the rectal temperature of the control or the Typhimurium-challenged pigs (compared with d 0) or when comparing Typhimurium-challenged pigs with control animals. In contrast, pigs fed Choleraesuis had increased rectal temperatures beginning on d 2 and continuing through d 7 (P < 0.05), with the greatest elevation on d 3 (P < 0.001) compared with the control pigs. Average daily gain and ADFI of pigs challenged with Typhimurium did not differ from those of the control animals. Pigs fed Choleraesuis had a 25% reduction in ADG (P < 0.0001) and ADFI (P < 0.002) compared with the control pigs. On d 7, pigs fed Choleraesuis had reduced serum IGF-I compared with control (P < 0.01) or Typhimurium-challenged pigs (P = 0.01). Bacterial feeding did not affect serum tumor necrosis factor-alpha or IL-1beta compared with control pigs at any time throughout the experiment. We conclude that repeated exposure of weaned pigs to Choleraesuis reduced growth performance in the absence of changes in systemic inflammatory cytokines.

Virulence of Broad- and Narrow-Host-RangeSalmonella entericaSerovars in the Streptomycin-PretreatedMouse Model

Salmonella enterica subspecies I serovars are common bacterial pathogens causing diseases ranging from enterocolitis to systemic infections. Some serovars are adapted to specific hosts, whereas others have a broad host range. The molecular mechanisms defining the virulence characteristics and the host range of a given S. enterica serovar are unknown. Streptomycin pretreated mice provide a surrogate host model for studying molecular aspects of the intestinal inflammation (colitis) caused by serovar Typhimurium (S. Hapfelmeier and W. D. Hardt, Trends Microbiol. 13:497-503, 2005). Here, we studied whether this animal model is also useful for studying other S. enterica subspecies I serovars. All three tested strains of the broad-host-range serovar Enteritidis (125109, 5496/98, and 832/99) caused pronounced colitis and systemic infection in streptomycin pretreated mice. Different levels of virulence were observed among three tested strains of the host-adapted serovar Dublin (SARB13, SD2229, and SD3246). Several strains of host restricted serovars were also studied. Two serovar Pullorum strains (X3543 and 449/87) caused intermediate levels of colitis. No intestinal inflammation was observed upon infection with three different serovar Paratyphi A strains (SARB42, 2804/96, and 5314/98) and one serovar Gallinarum strain (X3796). A second serovar Gallinarum strain (287/91) was highly virulent and caused severe colitis. This strain awaits future analysis. In conclusion, the streptomycin pretreated mouse model can provide an additional tool to study virulence factors (i.e., those involved in enteropathogenesis) of various S. enterica subspecies I serovars. Five of these strains (125109, 2229, 287/91, 449/87, and SARB42) are subject of Salmonella genome sequencing projects. The streptomycin pretreated mouse model may be useful for testing hypotheses derived from this genomic data.

The rise and fall of Salmonella Enteritidis in the UK.

After rising in the early 1980s, the number of recorded human cases of Salmonella enterica subsp. enterica in the UK has fallen in the last 5 years, with a particular decline in cases of infection with serovar Enteritidis. This decline has been concomitant with the introduction of vaccination of egg-laying hens against serovar Enteritidis. It is likely that other factors such as improved biosecurity in egg-laying flocks, a build-up of immunity in other animals and the rise in the number of livestock infections with host-adapted serovars of Salmonella have also played a part in this decline. Although human Salmonella cases are currently at their lowest level since 1987, it is important to remember that the reasons for the dominance of Enteritidis in human infection are poorly understood and it is possible that other serovars could share similar properties and the eradication of Enteritidis may leave a niche for them to fill.

EVIDENCE OF LEPTOSPIRA INTERROGANS INFECTION IN CALIFORNIA SEA LION PUPS FROM THE GULF OF CALIFORNIA

Forty-two urine and 96 blood and serum samples were obtained from California sea lion (Zalophus californianus) pups from the Gulf of California during the 2000 reproductive season. Antibody prevalence to 13 serovars of Leptospira interrogans was determined by microagglutination tests (MAT); presence of pathogenic leptospires was detected by polymerase chain reaction (PCR). Samples with antibody titers > or = 1:25 or 115 bp fragments on ethidium bromidestained 1.5% agarose gels were considered positive. Antibody prevalence was 54% overall with highest prevalence against serovar cynopteri (50% of all positive reactions). Highest antibody titers (1:50) were detected against serovars cynopteri and pomona. Polymerase chain reaction products were observed in two of 42 urine samples, six of 96 blood samples, and one of 96 serum samples. Presence of PCR products in blood and serum was demonstrated in pups that were seronegative. Kruskall-Wallis tests and corresponding post hoc Tukey tests (alpha = 0.05) showed that prevalence of leptospirosis was significantly different among all rookeries. The high seroprevalence (54%), low antibody titers (maximum 1:50), absence of pups showing clinical signs indicative of the disease, and lack of recent reports of increased mortality of sea lions in the Gulf of California are suggestive of the presence of enzootic host-adapted serovars. Crowding in rookeries as well as the presence of bats and rodents on some of the islands may explain infection by L. interrogans (sensu lato) and some of the differences in seroprevalence among reproductive rookeries.