Novel Insight into the Effects of CpxR on Salmonella enteritidis Cells during the Chlorhexidine Treatment and Non-Stressful Growing Conditions.

The development and spread of antibiotics and biocides resistance is a significant global challenge. To find a solution for this emerging problem, the discovery of novel bacterial cellular targets and the critical pathways associated with antimicrobial resistance is needed. In the present study, we investigated the role of the two most critical envelope stress response regulators, RpoE and CpxR, on the physiology and susceptibility of growing Salmonella enterica serovar enteritidis cells using the polycationic antimicrobial agent, chlorhexidine (CHX). It was shown that deletion of the cpxR gene significantly increased the susceptibility of this organism, whereas deletion of the rpoE gene had no effect on the pathogen's susceptibility to this antiseptic. It has been shown that a lack of the CpxR regulator induces multifaceted stress responses not only in the envelope but also in the cytosol, further affecting the key biomolecules, including DNA, RNA, and proteins. We showed that alterations in cellular trafficking and most of the stress responses are associated with a dysfunctional CpxR regulator during exponential growth phase, indicating that these physiological changes are intrinsically associated with the lack of the CpxR regulator. In contrast, induction of type II toxin-antitoxin systems and decrease of abundances of enzymes and proteins associated with the recycling of muropeptides and resistance to polymixin and cationic antimicrobial peptides were specific responses of the ∆cpxR mutant to the CHX treatment. Overall, our study provides insight into the effects of CpxR on the physiology of S. Enteritidis cells during the exponential growth phase and CHX treatment, which may point to potential cellular targets for the development of an effective antimicrobial agent.

Genetic Diversity of Ornithobacterium rhinotracheale Isolated from Chickens and Turkeys in the United States.

Ornithobacterium rhinotracheale (ORT) is an important bacterial pathogen of great economic significance to poultry production. This bacterium causes severe disease in chickens and turkeys worldwide. The objective of this study was to characterize ORT isolates from two different geographic locations in the United States by multilocus sequence typing (MLST). A total of 60 isolates were included in this study; 36 from California and 24 from Minnesota. All 60 isolates were confirmed to be ORT by PCR that targeted the 16S rRNA gene. The results of MLST revealed eight different sequence types (ST) of ORT. Out of these, four were novel and were assigned numbers ST-32, ST-33, ST-34, and ST-35. ST-1 was the predominant sequence type among all isolates followed by ST-9 and ST-8. Only one isolate was identified as ST-2. No significant variation was seen in STs in ORT isolated from different years. In turkeys, 76.3% (29/38) of isolates belonged to ST-1 and 7.9% (3/38) to ST-8. Of the chicken isolates, 72.2% (13/18) belonged to ST-1 and 16.6% (3/18) to ST-9. Isolates from both states showed low genetic variability. Of the 32 isolates from California, 24 (75%) were identified as ST-1 and 4 (12.5%) were identified as ST-9. The most prevalent sequence type was ST-1 (17/24) followed by ST-8 (3/24) in Minnesota. Three isolates from turkeys in Minnesota belonged to the same ST (ST-8) as the already known ORT strain RefO, which isolated from a rook in Germany in 2000. Whether this sequence type had evolved from wild birds could not be ascertained in this study.

Insights into the Oxidative Stress Response of Salmonella enterica serovar Enteritidis Revealed by the Next Generation Sequencing Approach.

As a facultative intracellular pathogen, Salmonella Enteritidis must develop an effective oxidative stress response to survive exposure to reactive oxygen species within the host. To study this defense mechanism, we carried out a series of oxidative stress assays in parallel with a comparative transcriptome analyses using a next generation sequencing approach. It was shown that the expression of 45% of the genome was significantly altered upon exposure to H2O2. Quantitatively the most significant (≥100 fold) gene expression alterations were observed among genes encoding the sulfur utilization factor of Fe-S cluster formation and iron homeostasis. Our data point out the multifaceted nature of the oxidative stress response. It includes not only numerous mechanisms of DNA and protein repair and redox homeostasis, but also the key genes associated with osmotic stress, multidrug efflux, stringent stress, decrease influx of small molecules, manganese and phosphate starvation stress responses. Importantly, this study revealed that oxidatively stressed S. Enteritidis cells simultaneously repressed key motility encoding genes and induced a wide range of adhesin- and salmonellae-essential virulence-encoding genes, that are critical for the biofilm formation and intracellular survival, respectively. This finding indicates a potential intrinsic link between oxidative stress and pathogenicity in non-typhoidal Salmonella that needs to be empirically evaluated.

Virulence factors and antibiograms of Escherichia coli isolated from diarrheic calves of Egyptian cattle and water buffaloes.

Diarrhea caused by Escherichia coli in calves is an important problem in terms of survivability, productivity and treatment costs. In this study, 88 of 150 diarrheic animals tested positive for E. coli. Of these, 54 samples had mixed infection with other bacterial and/or parasitic agents. There are several diarrheagenic E. coli pathotypes including enteropathogenic E. coli (EPEC), Shiga-toxin producing E. coli (STEC), enterotoxigenic E. coli (ETEC) and necrotoxigenic E. coli (NTEC). Molecular detection of virulence factors Stx2, Cdt3, Eae, CNF2, F5, Hly, Stx1, and ST revealed their presence at 39.7, 27.2, 19.3, 15.9, 13.6, 9.0, 3.4, and 3.4 percent, respectively. As many as 13.6% of the isolates lacked virulence genes and none of the isolate had LT or CNF1 toxin gene. The odds of isolating ETEC from male calves was 3.6 times (95% CI: 1.1, 12.4; P value = 0.042) that of female calves, whereas the odds of isolating NTEC from male calves was 72.9% lower (95% CI: 91.3% lower, 15.7% lower; P value = 0.024) than that in females. The odds of isolating STEC in winter was 3.3 times (95% CI: 1.1, 10.3; P value = 0.037) that of spring. Antibiograms showed 48 (54.5%) of the isolates to be multi-drug resistant. The percent resistance to tetracycline, streptomycin, ampicillin, and trimethoprim-sulfamethoxazole was 79.5, 67.0, 54.5, and 43.0, respectively. Ceftazidime (14.8%), amoxicillin-clavulanic acid (13.6%) and aztreonam (11.3%) showed the lowest resistance, and none of the isolates was resistant to imipenem. The results of this study can help improve our understanding of the epidemiological aspects of E. coli infection and to devise strategies for protection against it. The prevalence of E. coli pathotypes can help potential buyers of calves to avoid infected premises. The antibiograms in this study emphasizes the risks associated with the random use of antibiotics.

Bactericidal Efficacy of a Two-Dimensional Array of Integrated, Coaxial, Microhollow, Dielectric Barrier Discharge Plasma Against Salmonella enterica Serovar Heidelberg.

We studied the efficacy of cold atmospheric-pressure plasma (CAP), generated by a two-dimensional array of integrated, coaxial, microhollow, dielectric barrier discharge plasma, against Salmonella enterica serovar Heidelberg (SH) on stainless steel, romaine lettuce, and chicken breast. Exposure of SH to CAP on a dry stainless steel surface had low bactericidal efficacy; only 2.5 log10 colony-forming units (CFUs) were inactivated after 10 min of exposure. On the other hand, the presence of moisture led to decontamination of ∼6.5 log10 CFUs after only 3 min. Although complete decontamination was not achieved on lettuce and chicken breast samples after 10 min of exposure, SH counts were reduced by ∼4.5 and 3.7 log10 CFUs, respectively. A partial suppression of bactericidal effects was observed on steel surfaces when it was coated with bovine serum albumin before spiking with bacteria and exposure to plasma, indicating that the proteinaceous nature of chicken meat may be partially responsible for lower efficacy of CAP on chicken muscles. The initial bacterial load was also found to affect the anti-SH efficacy; at high (∼6.5 log CFUs) and low (∼3.5 CFUs) initial counts, the time required for complete decontamination on stainless steel and lettuce decreased from 3 to 0.5 min and >10 to 1 min, respectively. However, the analysis of inactivation kinetics showed that effects of initial loads of contamination on the rate of bacterial inactivation were not statistically significant. This is consistent with other findings for conditions where both bacterial loads were under the multilayering threshold that might have affected the rate of killing.

Comparative Genomic Studies of Salmonella Heidelberg Isolated From Chicken- and Turkey-Associated Farm Environmental Samples.

Salmonella is one of the leading causes of human foodborne gastroenteritis in the United States. In addition, Salmonella contributes to morbidity and mortality in livestock. The control of Salmonella is an increasing problematic issue in livestock production due to lack of effective control methods and the constant adaptation of Salmonella to new management practices, which is often related to horizontal acquisition of virulence or antibiotic resistance genes. Salmonella enterica serotype Heidelberg is one of the most commonly isolated serotypes in all poultry production systems in North America. Emergence and persistence of multi-drug resistant Salmonella Heidelberg isolates further impact the poultry production and public health. We hypothesized that distinct poultry production environments affect Salmonella genomic content, and by consequence its survival and virulence abilities. This study compared the genomic composition of S. Heidelberg isolated from environmental samples (19 chicken and 12 turkey isolates) of different breeder farms (16 chicken and 8 turkey farms) in the Midwest, United States. Whole genome comparison of 31 genomes using RAST and SEED identified differences in specific sub-systems in isolates between the chicken- and turkey-associated farm environmental samples. Genes associated with the type IV secretion system (n = 12) and conjugative transfer (n = 3) were absent in turkey farm isolates compared to the chicken ones (p-value < 0.01); Further, turkey farm isolates were enriched in prophage proteins (n = 53; p-value < 0.01). Complementary studies using PHASTER showed that prophages were all Caudovirales phages and were more represented in turkey environmental isolates than the chicken isolates. This study corroborates that isolates from distinct farm environment show differences in S. Heidelberg genome content related to horizontal transfer between bacteria or through viral infections. Complementary microbiome studies of these samples would provide critical insights on sources of these variations. Overall, our findings enhance the understanding of Salmonella genome plasticity and may aid in the development of future effective management practices to control Salmonella.

Occurrence of Campylobacter in retail meat in Lahore, Pakistan.

Campylobacter, one of the emerging zoonotic pathogens, is worldwide in distribution. This thermo-tolerant pathogen is one of the leading causes of diarrhea and gastroenteritis in humans. The main sources of infection are contaminated meat and meat products. A cross-sectional study was conducted to estimate the prevalence of Campylobacter species in retail meat in the Lahore district of Pakistan from September 2014 to January 2015. A total of 600 samples (200 samples each of beef, mutton, and chicken) were collected from retail shops through convenience sampling and preceded for Campylobacter contamination using the ISO 10272-1:2006 (E) method. Campylobacter was present in all three types of meat; the highest prevalence being recorded in chicken meat (29%) followed by mutton (18%) and beef (15.5%). Campylobacters were isolated from 125 (20.8%) samples out of the 600 meat samples. Campylobacter jejuni was more common (74.4%) than C. coli (25.6%). The highest number of Campylobacters were isolated in September (25/125) and November (23/125) while low numbers were isolated in October and December with isolates rate of (17/125) and (19/125), respectively. The highest prevalence was seen in the oldest and overpopulated town of Data Gunj Bakhsh 16% (20/125) while lowest prevalence was seen in a newer and least populated town of Gulburg (7/125). These results indicate that Campylobacter species are circulating in various meat sources in Lahore and that it may pose a threat to public health.

Genotypic relatedness and antimicrobial resistance of Salmonella Heidelberg isolated from chickens and turkeys in the midwestern United States.

Salmonella is one of the most common causes of foodborne illnesses in humans in the United States, and domestic poultry is considered an important source of this pathogen. Salmonella enterica subsp. enterica serovar Heidelberg is the fourth most commonly reported Salmonella from retail meats and food animals in the United States. We assessed the genotypes and antimicrobial resistance phenotypes of Salmonella Heidelberg isolated from various chicken and turkey hatcheries and breeder farms in the Midwest. The genotypes of 33 S. Heidelberg isolates from chickens ( n = 19) and turkeys ( n = 14) were compared using pulsed-field gel electrophoresis analysis. Cluster analysis of the fingerprints showed that the majority of the chicken isolates grouped together with 87% similarity; those from turkeys clustered with 88% similarity. Similarity between chicken and turkey isolates was also high (86%). Isolates from turkeys were generally more genetically diverse than those from chickens. Antimicrobial susceptibility analysis detected resistance to sulfisoxazole (36% of the isolates), streptomycin (33%), gentamicin (27%), tetracycline (24%), ampicillin and amoxicillin-clavulanic acid (15%), cefoxitin (12%), ceftriaxone and ceftiofur (12%), and chloramphenicol (9%). None of the isolates was resistant to azithromycin, ciprofloxacin, or nalidixic acid. Although the number of the isolates was limited in our study, we conclude that S. Heidelberg isolates from the same host generally clustered together and that a considerable number of the isolates were resistant to a number of antimicrobial agents.

Effects of dexamethasone immunosuppression on turkey clostridial dermatitis.

Clostridia represents a group of anaerobic spore-forming bacteria ubiquitous in the poultry environment. They are widely distributed in soil and survive for many years as highly resistant, inactive spores. They enter the body through wounds and contaminated feed as active bacteria or spores. Multiplication of clostridial bacteria occurs only in the absence of oxygen or in environments with very low concentrations of oxygen. During active multiplication, the clostridial organisms produce several toxins that are responsible for most of the clinical signs seen in clostridial diseases. Immunosuppression is a problem for the poultry industry. In modern, intensive poultry-rearing conditions, stress due to high population densities pose a considerable challenge for the immune system, and infectious agents can exploit this situation to cause disease. Immunosuppression may predispose turkeys to clostridial infection, resulting in clostridial dermatitis and mortality. The purpose of this study was to determine whether immunosuppression predisposes turkeys to clostridial infection and causes clostridial dermatitis. We immunosuppressed 10-wk-old turkey poults with dexamethasone. The birds immunosuppressed and not immunosuppressed were then challenged with Clostridium perfringens, Clostridium septicum, or both and examined for the development of clostridial dermatitis. The dexamethasone-treated birds were found to be more susceptible to C. peifingens/C. septicum challenge and developed clostridial dermatitis than the no-dexamethasone-treated birds through the subcutaneous route. However, oral inoculation of the same agents did not cause any dermatitis lesions in either of the groups.

Vaccination of turkeys with Clostridium septicum bacterin-toxoid: evaluation of protection against clostridial dermatitis.

Clostridial dermatitis is an acute disease causing high mortality in turkeys. Both Clostridium septicum and Clostridium pefringens have been isolated from these cases; however, reports from several diagnostic laboratories indicate an increased isolation rate of C septicum compared with C. perfringens from cases of clostridial dermatitis in recent years. Previous studies suggested C. septicum was more potent than C. perfringens in causing clostridial dermatitis in turkeys. The objective of this study was to develop and evaluate the use of a C. septicum bacterin-toxoid to control clostridial dermatitis in turkeys. A C. septicum bacterin-toxoid was prepared and was initially tested in 6-wk-old commercial turkeys under laboratory conditions for its safety and efficacy. Subsequently, the bacterin-toxoid was evaluated for use in commercial turkey farms with a consistent history of clostridial dermatitis. Birds in the field were vaccinated subcutaneously once at 6 wk of age with C. septicum bacterin-toxoid, and then mortality in both vaccinated and unvaccinated groups was recorded and compared. Blood samples from birds in both groups were examined using ELISA to detect antibody response to the C. septicum toxoid. The C. septicum bacterin-toxoid was found to be safe and to elicit antibodies against the toxoid. In vaccinated commercial turkeys, control of clostridial dermatitis was achieved via antibiotic use and clostridial dermatitis mortality was significantly reduced compared with that of birds in the unvaccinated group. The C. septicum bacterin-toxoid seems to be a valuable tool for the turkey industry to reduce losses due to clostridial dermatitis.

Serologic evidence of avian metapneumovirus infection among adults occupationally exposed to Turkeys.

Genetically similar, the avian metapneumovirus (aMPV) and the human MPV (hMPV) are the only viruses in the Metapneumovirus genus. Previous research demonstrated the ability of hMPV to cause clinical disease in turkeys. In this controlled, cross-sectional, seroepidemiological study, we examined the hypothesis that aMPV might infect humans. We enrolled 95 adults occupationally exposed to turkeys and 82 nonexposed controls. Sera from study participants were examined for antibodies against aMPV and hMPV. Both in bivariate (OR=3.2; 95% CI: 1.1-9.2) and in multivariate modelling adjusting for antibody to hMPV (OR=4.1; 95% CI: 1.3-13.1), meat-processing workers were found to have an increased odds of previous infection with aMPV compared to controls. While hMPV antibody cross-reactivity is evident, these data suggest that occupational exposure to turkeys is a risk factor for human infection with aMPV. More studies are needed to validate these findings, to identify modes of aMPV transmission, and to determine risk factors associated with infection.

Role of Clostridium perfringens and Clostridium septicum in causing turkey cellulitis.

The role of Clostridium perfringens and Clostridium septicum in the development of cellulitis and mortality in turkey poults was examined. Studies were done in turkeys of two age groups: 3-wk-old and 7-wk-old turkey poults. The effect of varying doses of C. perfringens and C. septicum in reproducing cellulitis lesions and mortality in turkeys was investigated. Both in vitro and in vivo assays were conducted to study their toxic and biologic activities. Clostridium septicum spore culture was found to be more potent than that of C. perfringens in both in vitro assays, such as the hemolysis test, and in vivo assays in mice and turkeys. Both C. perfringens and C. septicum spore cultures were found to be capable of inducing cellulitis lesions and mortality in turkey poults when inoculated by subcutaneous route. Histopathology examination of affected tissues revealed a "moth-eaten appearance, with abundant growth of C. perfringens and C. septicum in the sarcomeres of muscle tissues and in the subcutaneous tissues. However, C. septicum was found to be more potent than C. perfringens in causing cellulitis lesions and mortality in turkeys. Three-week-old poults were found to be less susceptible than 7-wk-old poults in the development of cellulitis lesions and mortality after inoculation with either spore cultures of C. perfringens or C. septicum. The results of the current study suggest that although C. septicum is more potent in causing cellulitis lesions and mortality, infection with either C. septicum or C. perfringens can cause cellulitis lesions and mortality in turkeys.

Iron acquisition by Ornithobacterium rhinotracheale.

Ornithobacterium rhinotracheale (ORT) is an emerging respiratory pathogen of poultry in North America that is causing millions of dollars in economic losses to the poultry industry. Ornithobacterium rhinotracheale is associated with airsacculitis, pleuritis, pneumonia, and consolidation of lungs. Little is known about the molecular mechanisms of infection. In this study, the mechanism of iron acquisition by O. rhinotracheale was explored. O. rhinotracheale strains grown under iron deprivation in media containing 200 microM 2,2'-dipyridyl did not secrete siderophores as measured by the chrome azurol S (CAS) agar and CAS solution assays. Filter disks impregnated with various protein-bound iron compounds and inorganic iron salts of Fe(III) and Fe(II) placed on iron-restricted agar inoculated with a lawn of O. rhinotracheale supported growth from sheep and porcine hemoglobins, ovotransferrin, Fe(III), and Fe(II), but they did not support growth from bovine transferrin, bovine apo-transferrin, bovine lactoferrin, and hemin. However, both bovine hemoglobin and transferrin supported growth of O. rhinotracheale serotype C. Four immunoreactive proteins involved in iron acquisition were identified in an O. rhinotracheale membrane extract by using mass spectrometry. Furthermore, O. rhinotracheale field strains showed differential sensitivity to 2,2'-dipyridyl. Of the 72 field strains tested, 22 strains were resistant to the iron chelator at concentrations of 50 microM and 100 microM, suggesting this attribute may be related to disease-producing potential of these strains. This is the first report on the identification of the iron acquisition mechanism of O. rhinotracheale.

Comparative pathogenicity of early and recent isolates of avian metapneumovirus subtype C in turkeys.

The objective of the present study was to compare the pathogenicity of early and recent isolates of avian metapneumovirus subtype-C (aMPV-C) in turkeys. Two-week-old turkeys were inoculated with early and recent isolates of aMPV-C. Clinical signs were monitored. Tissues were examined for viral ribonucleic acid (RNA), lesions, and viral antigen by reverse transcription-polymerase chain reaction (RT-PCR), histopathology and immunohistochemistry, respectively. Birds infected with the recent isolate had higher clinical sign scores than those infected with the early isolate. Only the recent isolate produced a multifocal loss of cilia in the nasal turbinate of infected birds. Immunohistochemistry revealed intense staining of aMPV antigen in turbinate and trachea of birds infected with the recent isolate. The findings indicate that the recent isolate produced more severe clinical signs and lesions in turkeys compared to the early isolate. The recent isolate could be ideal for the development of a challenge model for aMPV infection in turkeys.

Glycoprotein gene truncation in avian metapneumovirus subtype C isolates from the United States.

The length of the published glycoprotein (G) gene sequences of avian metapneumovirus subtype-C (aMPV-C) isolated from domestic turkeys and wild birds in the United States (1996-2003) remains controversial. To explore the G gene size variation in aMPV-C by the year of isolation and cell culture passage levels, we examined 21 turkey isolates of aMPV-C at different cell culture passages. The early domestic turkey isolates of aMPV-C (aMPV/CO/1996, aMPV/MN/1a-b, and 2a-b/97) had a G gene of 1,798 nucleotides (nt) that coded for a predicted protein of 585 amino acids (aa) and showed >97% nt similarity with that of aMPV-C isolated from Canada geese. This large G gene got truncated upon serial passages in Vero cell cultures by deletion of 1,015 nt near the end of the open reading frame. The recent domestic turkey isolates of aMPV-C lacked the large G gene but instead had a small G gene of 783 nt, irrespective of cell culture passage levels. In some cultures, both large and small genes were detected, indicating the existence of a mixed population of the virus. Apparently, serial passage of aMPV-C in cell cultures and natural passage in turkeys in the field led to truncation of the G gene, which may be a mechanism of virus evolution for survival in a new host or environment.

Application of polymerase chain reaction fingerprinting to differentiate Ornithobacterium rhinotracheale isolates.

Ornithobacterium rhinotracheale (ORT) is an infectious respiratory pathogen of chickens, turkeys, and wild birds. There are 18 serotypes of ORT reported worldwide. In this study, enterobacterial repetitive intergenic consensus (ERIC) polymerase chain reaction and random amplified polymorphic DNA assay with Universal M13 primer-based fingerprinting techniques were investigated for their ability to differentiate ORT isolates. The authors examined 50 field isolates and 8 reference strains of ORT for their genetic differences. The fingerprint patterns were compared with serotyping results of ORT by the agar gel precipitation test. M13 fingerprinting revealed different patterns for 6 reference serotypes of ORT that were tested, namely, C, D, E, I, J, and K. Ornithobacterium rhinotracheale reference serotypes A and F yielded indistinguishable fingerprints with M13 fingerprinting. The ERIC 1R technique discerned only 5 of the 8 reference serotypes of ORT. Distinct fingerprints were also found within the ORT serotypes with both techniques. From 58 isolates of ORT that were fingerprinted belonging to 8 ORT serotypes, 10 different fingerprints were obtained with M13 fingerprinting and 6 different fingerprints were obtained with ERIC 1R fingerprinting. M13 fingerprinting technique was found to be more discriminative in differentiating ORT isolates than the ERIC 1R fingerprinting technique. These results suggest that fingerprinting techniques may be a more discerning tool for characterizing ORT isolates than the serological test using the agar gel precipitation test. This fingerprinting technique could potentially be a valuable tool in identifying an isolate from a clinical outbreak of ORT infection for development of an autogenous vaccine.

Development of a vaccine-challenge model for avian metapneumovirus subtype C in turkeys.

The objective of this study was to evaluate different preparations of avian metapneumovirus (aMPV) subtype C as vaccine challenge in turkeys. Two aMPV isolates and their respective nasal turbinate homogenates after propagation in turkeys were used in the study. Significantly higher clinical sign scores were recorded in birds inoculated with 20 or 2% turbinate homogenate of recent isolate. Birds in the above groups showed more pronounced histopathological lesions, and a higher percentage of birds showed viral RNA and antigen in tissues. The data demonstrated that nasal turbinate homogenate of recent isolate produced severe clinical signs and lesions in turkeys and could be an ideal candidate for vaccine-challenge studies.

Effects of temperature and stabilizer on the viability of a live attenuated avian metapneumovirus vaccine.

A commercial live attenuated, freeze-dried avian metapneumovirus vaccine, Pneumomune, was assessed for its viability at three different temperatures (5.6 C, 21 C, and 37 C). No significant reduction in virus titer was observed when the vaccine was stored at 5.6 C for a period of 24 hr. However, reductions in virus titer of 1 log10 and 2 log10 were observed after 24 hr at 21 C and 37 C, respectively. Batch-to-batch variation in virus reduction was also observed. The addition of a dye or a vaccine stabilizer to the vaccine preparation did not have any deleterious effect on the survival of vaccine virus.

Preliminary evaluation of the use of the sefA fimbrial gene to elicit immune response against Salmonella enterica serotype Enteritidis in chickens.

In the last 2 decades, the prevalence of Salmonella enterica serotype Enteritidis (Salmonella Enteritidis) has dramatically increased worldwide, becoming the leading cause of food-borne illnesses and an important public health issue. Many studies have suggested the role of the SEF14 fimbrial protein in the adhesion of Salmonella Enteritidis to the host. In the present study, the sefA gene, which encodes the main subunit of the SEF14 fimbrial protein, was cloned into a temperature-sensitive expression vector and transformed into a nonpathogenic, avirulent strain of Escherichia coli. The recombinant strain was used as a vaccine to elicit specific immune response against the SefA protein of Salmonella Enteritidis in 1-day-old chickens. The recombinant strain was reisolated from the intestines of treated birds for up to 21 days posttreatment, demonstrating its ability to colonize the intestinal tracts of 1-day-old chickens. In addition, immunoglobulin A (IgA) against the SefA protein was detected in intestinal secretions from treated birds at 7 days posttreatment and in bile samples from 14 to 21 days posttreatment by enzyme-linked immunosorbent assay. Nontreated birds did not show any evidence of intestinal colonization by the recombinant strain or anti-SefA IgA response in their bile or intestinal secretions. Preliminary evaluation of the recombinant strain showed a potential use of this strain to elicit protection against Salmonella Enteritidis infection in chickens. Further experiments are needed to study the ability of the recombinant strain to protect birds against Salmonella Enteritidis colonization.

Emergence of multidrug-resistant Salmonella enterica serotype Newport in Minnesota.

We report a concurrent increase in the number of isolates of Salmonella enterica serotype Newport and the rate of multidrug resistance in S. Newport isolates from animal and human populations in Minnesota. Antimicrobial susceptibility and pulsed-field gel electrophoresis analysis demonstrated heterogeneity of isolates and showed that 1 pulsed-field gel electrophoresis cluster contained most of the multidrug-resistant isolates with a resistance pattern and most class 1 integron isolates, implying the clonal origin of the isolates.